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+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code. In place of
+** a legal notice, here is a blessing:
+**
+** May you do good and not evil.
+** May you find forgiveness for yourself and forgive others.
+** May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This is the implementation of the page cache subsystem or "pager".
+**
+** The pager is used to access a database disk file. It implements
+** atomic commit and rollback through the use of a journal file that
+** is separate from the database file. The pager also implements file
+** locking to prevent two processes from writing the same database
+** file simultaneously, or one process from reading the database while
+** another is writing.
+*/
+#ifndef SQLITE_OMIT_DISKIO
+#include "sqliteInt.h"
+#include "wal.h"
+
+
+/******************* NOTES ON THE DESIGN OF THE PAGER ************************
+**
+** This comment block describes invariants that hold when using a rollback
+** journal. These invariants do not apply for journal_mode=WAL,
+** journal_mode=MEMORY, or journal_mode=OFF.
+**
+** Within this comment block, a page is deemed to have been synced
+** automatically as soon as it is written when PRAGMA synchronous=OFF.
+** Otherwise, the page is not synced until the xSync method of the VFS
+** is called successfully on the file containing the page.
+**
+** Definition: A page of the database file is said to be "overwriteable" if
+** one or more of the following are true about the page:
+**
+** (a) The original content of the page as it was at the beginning of
+** the transaction has been written into the rollback journal and
+** synced.
+**
+** (b) The page was a freelist leaf page at the start of the transaction.
+**
+** (c) The page number is greater than the largest page that existed in
+** the database file at the start of the transaction.
+**
+** (1) A page of the database file is never overwritten unless one of the
+** following are true:
+**
+** (a) The page and all other pages on the same sector are overwriteable.
+**
+** (b) The atomic page write optimization is enabled, and the entire
+** transaction other than the update of the transaction sequence
+** number consists of a single page change.
+**
+** (2) The content of a page written into the rollback journal exactly matches
+** both the content in the database when the rollback journal was written
+** and the content in the database at the beginning of the current
+** transaction.
+**
+** (3) Writes to the database file are an integer multiple of the page size
+** in length and are aligned on a page boundary.
+**
+** (4) Reads from the database file are either aligned on a page boundary and
+** an integer multiple of the page size in length or are taken from the
+** first 100 bytes of the database file.
+**
+** (5) All writes to the database file are synced prior to the rollback journal
+** being deleted, truncated, or zeroed.
+**
+** (6) If a super-journal file is used, then all writes to the database file
+** are synced prior to the super-journal being deleted.
+**
+** Definition: Two databases (or the same database at two points it time)
+** are said to be "logically equivalent" if they give the same answer to
+** all queries. Note in particular the content of freelist leaf
+** pages can be changed arbitrarily without affecting the logical equivalence
+** of the database.
+**
+** (7) At any time, if any subset, including the empty set and the total set,
+** of the unsynced changes to a rollback journal are removed and the
+** journal is rolled back, the resulting database file will be logically
+** equivalent to the database file at the beginning of the transaction.
+**
+** (8) When a transaction is rolled back, the xTruncate method of the VFS
+** is called to restore the database file to the same size it was at
+** the beginning of the transaction. (In some VFSes, the xTruncate
+** method is a no-op, but that does not change the fact the SQLite will
+** invoke it.)
+**
+** (9) Whenever the database file is modified, at least one bit in the range
+** of bytes from 24 through 39 inclusive will be changed prior to releasing
+** the EXCLUSIVE lock, thus signaling other connections on the same
+** database to flush their caches.
+**
+** (10) The pattern of bits in bytes 24 through 39 shall not repeat in less
+** than one billion transactions.
+**
+** (11) A database file is well-formed at the beginning and at the conclusion
+** of every transaction.
+**
+** (12) An EXCLUSIVE lock is held on the database file when writing to
+** the database file.
+**
+** (13) A SHARED lock is held on the database file while reading any
+** content out of the database file.
+**
+******************************************************************************/
+
+/*
+** Macros for troubleshooting. Normally turned off
+*/
+#if 0
+int sqlite3PagerTrace=1; /* True to enable tracing */
+#define sqlite3DebugPrintf printf
+#define PAGERTRACE(X) if( sqlite3PagerTrace ){ sqlite3DebugPrintf X; }
+#else
+#define PAGERTRACE(X)
+#endif
+
+/*
+** The following two macros are used within the PAGERTRACE() macros above
+** to print out file-descriptors.
+**
+** PAGERID() takes a pointer to a Pager struct as its argument. The
+** associated file-descriptor is returned. FILEHANDLEID() takes an sqlite3_file
+** struct as its argument.
+*/
+#define PAGERID(p) (SQLITE_PTR_TO_INT(p->fd))
+#define FILEHANDLEID(fd) (SQLITE_PTR_TO_INT(fd))
+
+/*
+** The Pager.eState variable stores the current 'state' of a pager. A
+** pager may be in any one of the seven states shown in the following
+** state diagram.
+**
+** OPEN <------+------+
+** | | |
+** V | |
+** +---------> READER-------+ |
+** | | |
+** | V |
+** |<-------WRITER_LOCKED------> ERROR
+** | | ^
+** | V |
+** |<------WRITER_CACHEMOD-------->|
+** | | |
+** | V |
+** |<-------WRITER_DBMOD---------->|
+** | | |
+** | V |
+** +<------WRITER_FINISHED-------->+
+**
+**
+** List of state transitions and the C [function] that performs each:
+**
+** OPEN -> READER [sqlite3PagerSharedLock]
+** READER -> OPEN [pager_unlock]
+**
+** READER -> WRITER_LOCKED [sqlite3PagerBegin]
+** WRITER_LOCKED -> WRITER_CACHEMOD [pager_open_journal]
+** WRITER_CACHEMOD -> WRITER_DBMOD [syncJournal]
+** WRITER_DBMOD -> WRITER_FINISHED [sqlite3PagerCommitPhaseOne]
+** WRITER_*** -> READER [pager_end_transaction]
+**
+** WRITER_*** -> ERROR [pager_error]
+** ERROR -> OPEN [pager_unlock]
+**
+**
+** OPEN:
+**
+** The pager starts up in this state. Nothing is guaranteed in this
+** state - the file may or may not be locked and the database size is
+** unknown. The database may not be read or written.
+**
+** * No read or write transaction is active.
+** * Any lock, or no lock at all, may be held on the database file.
+** * The dbSize, dbOrigSize and dbFileSize variables may not be trusted.
+**
+** READER:
+**
+** In this state all the requirements for reading the database in
+** rollback (non-WAL) mode are met. Unless the pager is (or recently
+** was) in exclusive-locking mode, a user-level read transaction is
+** open. The database size is known in this state.
+**
+** A connection running with locking_mode=normal enters this state when
+** it opens a read-transaction on the database and returns to state
+** OPEN after the read-transaction is completed. However a connection
+** running in locking_mode=exclusive (including temp databases) remains in
+** this state even after the read-transaction is closed. The only way
+** a locking_mode=exclusive connection can transition from READER to OPEN
+** is via the ERROR state (see below).
+**
+** * A read transaction may be active (but a write-transaction cannot).
+** * A SHARED or greater lock is held on the database file.
+** * The dbSize variable may be trusted (even if a user-level read
+** transaction is not active). The dbOrigSize and dbFileSize variables
+** may not be trusted at this point.
+** * If the database is a WAL database, then the WAL connection is open.
+** * Even if a read-transaction is not open, it is guaranteed that
+** there is no hot-journal in the file-system.
+**
+** WRITER_LOCKED:
+**
+** The pager moves to this state from READER when a write-transaction
+** is first opened on the database. In WRITER_LOCKED state, all locks
+** required to start a write-transaction are held, but no actual
+** modifications to the cache or database have taken place.
+**
+** In rollback mode, a RESERVED or (if the transaction was opened with
+** BEGIN EXCLUSIVE) EXCLUSIVE lock is obtained on the database file when
+** moving to this state, but the journal file is not written to or opened
+** to in this state. If the transaction is committed or rolled back while
+** in WRITER_LOCKED state, all that is required is to unlock the database
+** file.
+**
+** IN WAL mode, WalBeginWriteTransaction() is called to lock the log file.
+** If the connection is running with locking_mode=exclusive, an attempt
+** is made to obtain an EXCLUSIVE lock on the database file.
+**
+** * A write transaction is active.
+** * If the connection is open in rollback-mode, a RESERVED or greater
+** lock is held on the database file.
+** * If the connection is open in WAL-mode, a WAL write transaction
+** is open (i.e. sqlite3WalBeginWriteTransaction() has been successfully
+** called).
+** * The dbSize, dbOrigSize and dbFileSize variables are all valid.
+** * The contents of the pager cache have not been modified.
+** * The journal file may or may not be open.
+** * Nothing (not even the first header) has been written to the journal.
+**
+** WRITER_CACHEMOD:
+**
+** A pager moves from WRITER_LOCKED state to this state when a page is
+** first modified by the upper layer. In rollback mode the journal file
+** is opened (if it is not already open) and a header written to the
+** start of it. The database file on disk has not been modified.
+**
+** * A write transaction is active.
+** * A RESERVED or greater lock is held on the database file.
+** * The journal file is open and the first header has been written
+** to it, but the header has not been synced to disk.
+** * The contents of the page cache have been modified.
+**
+** WRITER_DBMOD:
+**
+** The pager transitions from WRITER_CACHEMOD into WRITER_DBMOD state
+** when it modifies the contents of the database file. WAL connections
+** never enter this state (since they do not modify the database file,
+** just the log file).
+**
+** * A write transaction is active.
+** * An EXCLUSIVE or greater lock is held on the database file.
+** * The journal file is open and the first header has been written
+** and synced to disk.
+** * The contents of the page cache have been modified (and possibly
+** written to disk).
+**
+** WRITER_FINISHED:
+**
+** It is not possible for a WAL connection to enter this state.
+**
+** A rollback-mode pager changes to WRITER_FINISHED state from WRITER_DBMOD
+** state after the entire transaction has been successfully written into the
+** database file. In this state the transaction may be committed simply
+** by finalizing the journal file. Once in WRITER_FINISHED state, it is
+** not possible to modify the database further. At this point, the upper
+** layer must either commit or rollback the transaction.
+**
+** * A write transaction is active.
+** * An EXCLUSIVE or greater lock is held on the database file.
+** * All writing and syncing of journal and database data has finished.
+** If no error occurred, all that remains is to finalize the journal to
+** commit the transaction. If an error did occur, the caller will need
+** to rollback the transaction.
+**
+** ERROR:
+**
+** The ERROR state is entered when an IO or disk-full error (including
+** SQLITE_IOERR_NOMEM) occurs at a point in the code that makes it
+** difficult to be sure that the in-memory pager state (cache contents,
+** db size etc.) are consistent with the contents of the file-system.
+**
+** Temporary pager files may enter the ERROR state, but in-memory pagers
+** cannot.
+**
+** For example, if an IO error occurs while performing a rollback,
+** the contents of the page-cache may be left in an inconsistent state.
+** At this point it would be dangerous to change back to READER state
+** (as usually happens after a rollback). Any subsequent readers might
+** report database corruption (due to the inconsistent cache), and if
+** they upgrade to writers, they may inadvertently corrupt the database
+** file. To avoid this hazard, the pager switches into the ERROR state
+** instead of READER following such an error.
+**
+** Once it has entered the ERROR state, any attempt to use the pager
+** to read or write data returns an error. Eventually, once all
+** outstanding transactions have been abandoned, the pager is able to
+** transition back to OPEN state, discarding the contents of the
+** page-cache and any other in-memory state at the same time. Everything
+** is reloaded from disk (and, if necessary, hot-journal rollback performed)
+** when a read-transaction is next opened on the pager (transitioning
+** the pager into READER state). At that point the system has recovered
+** from the error.
+**
+** Specifically, the pager jumps into the ERROR state if:
+**
+** 1. An error occurs while attempting a rollback. This happens in
+** function sqlite3PagerRollback().
+**
+** 2. An error occurs while attempting to finalize a journal file
+** following a commit in function sqlite3PagerCommitPhaseTwo().
+**
+** 3. An error occurs while attempting to write to the journal or
+** database file in function pagerStress() in order to free up
+** memory.
+**
+** In other cases, the error is returned to the b-tree layer. The b-tree
+** layer then attempts a rollback operation. If the error condition
+** persists, the pager enters the ERROR state via condition (1) above.
+**
+** Condition (3) is necessary because it can be triggered by a read-only
+** statement executed within a transaction. In this case, if the error
+** code were simply returned to the user, the b-tree layer would not
+** automatically attempt a rollback, as it assumes that an error in a
+** read-only statement cannot leave the pager in an internally inconsistent
+** state.
+**
+** * The Pager.errCode variable is set to something other than SQLITE_OK.
+** * There are one or more outstanding references to pages (after the
+** last reference is dropped the pager should move back to OPEN state).
+** * The pager is not an in-memory pager.
+**
+**
+** Notes:
+**
+** * A pager is never in WRITER_DBMOD or WRITER_FINISHED state if the
+** connection is open in WAL mode. A WAL connection is always in one
+** of the first four states.
+**
+** * Normally, a connection open in exclusive mode is never in PAGER_OPEN
+** state. There are two exceptions: immediately after exclusive-mode has
+** been turned on (and before any read or write transactions are
+** executed), and when the pager is leaving the "error state".
+**
+** * See also: assert_pager_state().
+*/
+#define PAGER_OPEN 0
+#define PAGER_READER 1
+#define PAGER_WRITER_LOCKED 2
+#define PAGER_WRITER_CACHEMOD 3
+#define PAGER_WRITER_DBMOD 4
+#define PAGER_WRITER_FINISHED 5
+#define PAGER_ERROR 6
+
+/*
+** The Pager.eLock variable is almost always set to one of the
+** following locking-states, according to the lock currently held on
+** the database file: NO_LOCK, SHARED_LOCK, RESERVED_LOCK or EXCLUSIVE_LOCK.
+** This variable is kept up to date as locks are taken and released by
+** the pagerLockDb() and pagerUnlockDb() wrappers.
+**
+** If the VFS xLock() or xUnlock() returns an error other than SQLITE_BUSY
+** (i.e. one of the SQLITE_IOERR subtypes), it is not clear whether or not
+** the operation was successful. In these circumstances pagerLockDb() and
+** pagerUnlockDb() take a conservative approach - eLock is always updated
+** when unlocking the file, and only updated when locking the file if the
+** VFS call is successful. This way, the Pager.eLock variable may be set
+** to a less exclusive (lower) value than the lock that is actually held
+** at the system level, but it is never set to a more exclusive value.
+**
+** This is usually safe. If an xUnlock fails or appears to fail, there may
+** be a few redundant xLock() calls or a lock may be held for longer than
+** required, but nothing really goes wrong.
+**
+** The exception is when the database file is unlocked as the pager moves
+** from ERROR to OPEN state. At this point there may be a hot-journal file
+** in the file-system that needs to be rolled back (as part of an OPEN->SHARED
+** transition, by the same pager or any other). If the call to xUnlock()
+** fails at this point and the pager is left holding an EXCLUSIVE lock, this
+** can confuse the call to xCheckReservedLock() call made later as part
+** of hot-journal detection.
+**
+** xCheckReservedLock() is defined as returning true "if there is a RESERVED
+** lock held by this process or any others". So xCheckReservedLock may
+** return true because the caller itself is holding an EXCLUSIVE lock (but
+** doesn't know it because of a previous error in xUnlock). If this happens
+** a hot-journal may be mistaken for a journal being created by an active
+** transaction in another process, causing SQLite to read from the database
+** without rolling it back.
+**
+** To work around this, if a call to xUnlock() fails when unlocking the
+** database in the ERROR state, Pager.eLock is set to UNKNOWN_LOCK. It
+** is only changed back to a real locking state after a successful call
+** to xLock(EXCLUSIVE). Also, the code to do the OPEN->SHARED state transition
+** omits the check for a hot-journal if Pager.eLock is set to UNKNOWN_LOCK
+** lock. Instead, it assumes a hot-journal exists and obtains an EXCLUSIVE
+** lock on the database file before attempting to roll it back. See function
+** PagerSharedLock() for more detail.
+**
+** Pager.eLock may only be set to UNKNOWN_LOCK when the pager is in
+** PAGER_OPEN state.
+*/
+#define UNKNOWN_LOCK (EXCLUSIVE_LOCK+1)
+
+/*
+** The maximum allowed sector size. 64KiB. If the xSectorsize() method
+** returns a value larger than this, then MAX_SECTOR_SIZE is used instead.
+** This could conceivably cause corruption following a power failure on
+** such a system. This is currently an undocumented limit.
+*/
+#define MAX_SECTOR_SIZE 0x10000
+
+
+/*
+** An instance of the following structure is allocated for each active
+** savepoint and statement transaction in the system. All such structures
+** are stored in the Pager.aSavepoint[] array, which is allocated and
+** resized using sqlite3Realloc().
+**
+** When a savepoint is created, the PagerSavepoint.iHdrOffset field is
+** set to 0. If a journal-header is written into the main journal while
+** the savepoint is active, then iHdrOffset is set to the byte offset
+** immediately following the last journal record written into the main
+** journal before the journal-header. This is required during savepoint
+** rollback (see pagerPlaybackSavepoint()).
+*/
+typedef struct PagerSavepoint PagerSavepoint;
+struct PagerSavepoint {
+ i64 iOffset; /* Starting offset in main journal */
+ i64 iHdrOffset; /* See above */
+ Bitvec *pInSavepoint; /* Set of pages in this savepoint */
+ Pgno nOrig; /* Original number of pages in file */
+ Pgno iSubRec; /* Index of first record in sub-journal */
+ int bTruncateOnRelease; /* If stmt journal may be truncated on RELEASE */
+#ifndef SQLITE_OMIT_WAL
+ u32 aWalData[WAL_SAVEPOINT_NDATA]; /* WAL savepoint context */
+#endif
+};
+
+/*
+** Bits of the Pager.doNotSpill flag. See further description below.
+*/
+#define SPILLFLAG_OFF 0x01 /* Never spill cache. Set via pragma */
+#define SPILLFLAG_ROLLBACK 0x02 /* Current rolling back, so do not spill */
+#define SPILLFLAG_NOSYNC 0x04 /* Spill is ok, but do not sync */
+
+/*
+** An open page cache is an instance of struct Pager. A description of
+** some of the more important member variables follows:
+**
+** eState
+**
+** The current 'state' of the pager object. See the comment and state
+** diagram above for a description of the pager state.
+**
+** eLock
+**
+** For a real on-disk database, the current lock held on the database file -
+** NO_LOCK, SHARED_LOCK, RESERVED_LOCK or EXCLUSIVE_LOCK.
+**
+** For a temporary or in-memory database (neither of which require any
+** locks), this variable is always set to EXCLUSIVE_LOCK. Since such
+** databases always have Pager.exclusiveMode==1, this tricks the pager
+** logic into thinking that it already has all the locks it will ever
+** need (and no reason to release them).
+**
+** In some (obscure) circumstances, this variable may also be set to
+** UNKNOWN_LOCK. See the comment above the #define of UNKNOWN_LOCK for
+** details.
+**
+** changeCountDone
+**
+** This boolean variable is used to make sure that the change-counter
+** (the 4-byte header field at byte offset 24 of the database file) is
+** not updated more often than necessary.
+**
+** It is set to true when the change-counter field is updated, which
+** can only happen if an exclusive lock is held on the database file.
+** It is cleared (set to false) whenever an exclusive lock is
+** relinquished on the database file. Each time a transaction is committed,
+** The changeCountDone flag is inspected. If it is true, the work of
+** updating the change-counter is omitted for the current transaction.
+**
+** This mechanism means that when running in exclusive mode, a connection
+** need only update the change-counter once, for the first transaction
+** committed.
+**
+** setSuper
+**
+** When PagerCommitPhaseOne() is called to commit a transaction, it may
+** (or may not) specify a super-journal name to be written into the
+** journal file before it is synced to disk.
+**
+** Whether or not a journal file contains a super-journal pointer affects
+** the way in which the journal file is finalized after the transaction is
+** committed or rolled back when running in "journal_mode=PERSIST" mode.
+** If a journal file does not contain a super-journal pointer, it is
+** finalized by overwriting the first journal header with zeroes. If
+** it does contain a super-journal pointer the journal file is finalized
+** by truncating it to zero bytes, just as if the connection were
+** running in "journal_mode=truncate" mode.
+**
+** Journal files that contain super-journal pointers cannot be finalized
+** simply by overwriting the first journal-header with zeroes, as the
+** super-journal pointer could interfere with hot-journal rollback of any
+** subsequently interrupted transaction that reuses the journal file.
+**
+** The flag is cleared as soon as the journal file is finalized (either
+** by PagerCommitPhaseTwo or PagerRollback). If an IO error prevents the
+** journal file from being successfully finalized, the setSuper flag
+** is cleared anyway (and the pager will move to ERROR state).
+**
+** doNotSpill
+**
+** This variables control the behavior of cache-spills (calls made by
+** the pcache module to the pagerStress() routine to write cached data
+** to the file-system in order to free up memory).
+**
+** When bits SPILLFLAG_OFF or SPILLFLAG_ROLLBACK of doNotSpill are set,
+** writing to the database from pagerStress() is disabled altogether.
+** The SPILLFLAG_ROLLBACK case is done in a very obscure case that
+** comes up during savepoint rollback that requires the pcache module
+** to allocate a new page to prevent the journal file from being written
+** while it is being traversed by code in pager_playback(). The SPILLFLAG_OFF
+** case is a user preference.
+**
+** If the SPILLFLAG_NOSYNC bit is set, writing to the database from
+** pagerStress() is permitted, but syncing the journal file is not.
+** This flag is set by sqlite3PagerWrite() when the file-system sector-size
+** is larger than the database page-size in order to prevent a journal sync
+** from happening in between the journalling of two pages on the same sector.
+**
+** subjInMemory
+**
+** This is a boolean variable. If true, then any required sub-journal
+** is opened as an in-memory journal file. If false, then in-memory
+** sub-journals are only used for in-memory pager files.
+**
+** This variable is updated by the upper layer each time a new
+** write-transaction is opened.
+**
+** dbSize, dbOrigSize, dbFileSize
+**
+** Variable dbSize is set to the number of pages in the database file.
+** It is valid in PAGER_READER and higher states (all states except for
+** OPEN and ERROR).
+**
+** dbSize is set based on the size of the database file, which may be
+** larger than the size of the database (the value stored at offset
+** 28 of the database header by the btree). If the size of the file
+** is not an integer multiple of the page-size, the value stored in
+** dbSize is rounded down (i.e. a 5KB file with 2K page-size has dbSize==2).
+** Except, any file that is greater than 0 bytes in size is considered
+** to have at least one page. (i.e. a 1KB file with 2K page-size leads
+** to dbSize==1).
+**
+** During a write-transaction, if pages with page-numbers greater than
+** dbSize are modified in the cache, dbSize is updated accordingly.
+** Similarly, if the database is truncated using PagerTruncateImage(),
+** dbSize is updated.
+**
+** Variables dbOrigSize and dbFileSize are valid in states
+** PAGER_WRITER_LOCKED and higher. dbOrigSize is a copy of the dbSize
+** variable at the start of the transaction. It is used during rollback,
+** and to determine whether or not pages need to be journalled before
+** being modified.
+**
+** Throughout a write-transaction, dbFileSize contains the size of
+** the file on disk in pages. It is set to a copy of dbSize when the
+** write-transaction is first opened, and updated when VFS calls are made
+** to write or truncate the database file on disk.
+**
+** The only reason the dbFileSize variable is required is to suppress
+** unnecessary calls to xTruncate() after committing a transaction. If,
+** when a transaction is committed, the dbFileSize variable indicates
+** that the database file is larger than the database image (Pager.dbSize),
+** pager_truncate() is called. The pager_truncate() call uses xFilesize()
+** to measure the database file on disk, and then truncates it if required.
+** dbFileSize is not used when rolling back a transaction. In this case
+** pager_truncate() is called unconditionally (which means there may be
+** a call to xFilesize() that is not strictly required). In either case,
+** pager_truncate() may cause the file to become smaller or larger.
+**
+** dbHintSize
+**
+** The dbHintSize variable is used to limit the number of calls made to
+** the VFS xFileControl(FCNTL_SIZE_HINT) method.
+**
+** dbHintSize is set to a copy of the dbSize variable when a
+** write-transaction is opened (at the same time as dbFileSize and
+** dbOrigSize). If the xFileControl(FCNTL_SIZE_HINT) method is called,
+** dbHintSize is increased to the number of pages that correspond to the
+** size-hint passed to the method call. See pager_write_pagelist() for
+** details.
+**
+** errCode
+**
+** The Pager.errCode variable is only ever used in PAGER_ERROR state. It
+** is set to zero in all other states. In PAGER_ERROR state, Pager.errCode
+** is always set to SQLITE_FULL, SQLITE_IOERR or one of the SQLITE_IOERR_XXX
+** sub-codes.
+**
+** syncFlags, walSyncFlags
+**
+** syncFlags is either SQLITE_SYNC_NORMAL (0x02) or SQLITE_SYNC_FULL (0x03).
+** syncFlags is used for rollback mode. walSyncFlags is used for WAL mode
+** and contains the flags used to sync the checkpoint operations in the
+** lower two bits, and sync flags used for transaction commits in the WAL
+** file in bits 0x04 and 0x08. In other words, to get the correct sync flags
+** for checkpoint operations, use (walSyncFlags&0x03) and to get the correct
+** sync flags for transaction commit, use ((walSyncFlags>>2)&0x03). Note
+** that with synchronous=NORMAL in WAL mode, transaction commit is not synced
+** meaning that the 0x04 and 0x08 bits are both zero.
+*/
+struct Pager {
+ sqlite3_vfs *pVfs; /* OS functions to use for IO */
+ u8 exclusiveMode; /* Boolean. True if locking_mode==EXCLUSIVE */
+ u8 journalMode; /* One of the PAGER_JOURNALMODE_* values */
+ u8 useJournal; /* Use a rollback journal on this file */
+ u8 noSync; /* Do not sync the journal if true */
+ u8 fullSync; /* Do extra syncs of the journal for robustness */
+ u8 extraSync; /* sync directory after journal delete */
+ u8 syncFlags; /* SYNC_NORMAL or SYNC_FULL otherwise */
+ u8 walSyncFlags; /* See description above */
+ u8 tempFile; /* zFilename is a temporary or immutable file */
+ u8 noLock; /* Do not lock (except in WAL mode) */
+ u8 readOnly; /* True for a read-only database */
+ u8 memDb; /* True to inhibit all file I/O */
+ u8 memVfs; /* VFS-implemented memory database */
+
+ /**************************************************************************
+ ** The following block contains those class members that change during
+ ** routine operation. Class members not in this block are either fixed
+ ** when the pager is first created or else only change when there is a
+ ** significant mode change (such as changing the page_size, locking_mode,
+ ** or the journal_mode). From another view, these class members describe
+ ** the "state" of the pager, while other class members describe the
+ ** "configuration" of the pager.
+ */
+ u8 eState; /* Pager state (OPEN, READER, WRITER_LOCKED..) */
+ u8 eLock; /* Current lock held on database file */
+ u8 changeCountDone; /* Set after incrementing the change-counter */
+ u8 setSuper; /* Super-jrnl name is written into jrnl */
+ u8 doNotSpill; /* Do not spill the cache when non-zero */
+ u8 subjInMemory; /* True to use in-memory sub-journals */
+ u8 bUseFetch; /* True to use xFetch() */
+ u8 hasHeldSharedLock; /* True if a shared lock has ever been held */
+ Pgno dbSize; /* Number of pages in the database */
+ Pgno dbOrigSize; /* dbSize before the current transaction */
+ Pgno dbFileSize; /* Number of pages in the database file */
+ Pgno dbHintSize; /* Value passed to FCNTL_SIZE_HINT call */
+ int errCode; /* One of several kinds of errors */
+ int nRec; /* Pages journalled since last j-header written */
+ u32 cksumInit; /* Quasi-random value added to every checksum */
+ u32 nSubRec; /* Number of records written to sub-journal */
+ Bitvec *pInJournal; /* One bit for each page in the database file */
+ sqlite3_file *fd; /* File descriptor for database */
+ sqlite3_file *jfd; /* File descriptor for main journal */
+ sqlite3_file *sjfd; /* File descriptor for sub-journal */
+ i64 journalOff; /* Current write offset in the journal file */
+ i64 journalHdr; /* Byte offset to previous journal header */
+ sqlite3_backup *pBackup; /* Pointer to list of ongoing backup processes */
+ PagerSavepoint *aSavepoint; /* Array of active savepoints */
+ int nSavepoint; /* Number of elements in aSavepoint[] */
+ u32 iDataVersion; /* Changes whenever database content changes */
+ char dbFileVers[16]; /* Changes whenever database file changes */
+
+ int nMmapOut; /* Number of mmap pages currently outstanding */
+ sqlite3_int64 szMmap; /* Desired maximum mmap size */
+ PgHdr *pMmapFreelist; /* List of free mmap page headers (pDirty) */
+ /*
+ ** End of the routinely-changing class members
+ ***************************************************************************/
+
+ u16 nExtra; /* Add this many bytes to each in-memory page */
+ i16 nReserve; /* Number of unused bytes at end of each page */
+ u32 vfsFlags; /* Flags for sqlite3_vfs.xOpen() */
+ u32 sectorSize; /* Assumed sector size during rollback */
+ Pgno mxPgno; /* Maximum allowed size of the database */
+ Pgno lckPgno; /* Page number for the locking page */
+ i64 pageSize; /* Number of bytes in a page */
+ i64 journalSizeLimit; /* Size limit for persistent journal files */
+ char *zFilename; /* Name of the database file */
+ char *zJournal; /* Name of the journal file */
+ int (*xBusyHandler)(void*); /* Function to call when busy */
+ void *pBusyHandlerArg; /* Context argument for xBusyHandler */
+ u32 aStat[4]; /* Total cache hits, misses, writes, spills */
+#ifdef SQLITE_TEST
+ int nRead; /* Database pages read */
+#endif
+ void (*xReiniter)(DbPage*); /* Call this routine when reloading pages */
+ int (*xGet)(Pager*,Pgno,DbPage**,int); /* Routine to fetch a patch */
+ char *pTmpSpace; /* Pager.pageSize bytes of space for tmp use */
+ PCache *pPCache; /* Pointer to page cache object */
+#ifndef SQLITE_OMIT_WAL
+ Wal *pWal; /* Write-ahead log used by "journal_mode=wal" */
+ char *zWal; /* File name for write-ahead log */
+#endif
+};
+
+/*
+** Indexes for use with Pager.aStat[]. The Pager.aStat[] array contains
+** the values accessed by passing SQLITE_DBSTATUS_CACHE_HIT, CACHE_MISS
+** or CACHE_WRITE to sqlite3_db_status().
+*/
+#define PAGER_STAT_HIT 0
+#define PAGER_STAT_MISS 1
+#define PAGER_STAT_WRITE 2
+#define PAGER_STAT_SPILL 3
+
+/*
+** The following global variables hold counters used for
+** testing purposes only. These variables do not exist in
+** a non-testing build. These variables are not thread-safe.
+*/
+#ifdef SQLITE_TEST
+int sqlite3_pager_readdb_count = 0; /* Number of full pages read from DB */
+int sqlite3_pager_writedb_count = 0; /* Number of full pages written to DB */
+int sqlite3_pager_writej_count = 0; /* Number of pages written to journal */
+# define PAGER_INCR(v) v++
+#else
+# define PAGER_INCR(v)
+#endif
+
+
+
+/*
+** Journal files begin with the following magic string. The data
+** was obtained from /dev/random. It is used only as a sanity check.
+**
+** Since version 2.8.0, the journal format contains additional sanity
+** checking information. If the power fails while the journal is being
+** written, semi-random garbage data might appear in the journal
+** file after power is restored. If an attempt is then made
+** to roll the journal back, the database could be corrupted. The additional
+** sanity checking data is an attempt to discover the garbage in the
+** journal and ignore it.
+**
+** The sanity checking information for the new journal format consists
+** of a 32-bit checksum on each page of data. The checksum covers both
+** the page number and the pPager->pageSize bytes of data for the page.
+** This cksum is initialized to a 32-bit random value that appears in the
+** journal file right after the header. The random initializer is important,
+** because garbage data that appears at the end of a journal is likely
+** data that was once in other files that have now been deleted. If the
+** garbage data came from an obsolete journal file, the checksums might
+** be correct. But by initializing the checksum to random value which
+** is different for every journal, we minimize that risk.
+*/
+static const unsigned char aJournalMagic[] = {
+ 0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd7,
+};
+
+/*
+** The size of the of each page record in the journal is given by
+** the following macro.
+*/
+#define JOURNAL_PG_SZ(pPager) ((pPager->pageSize) + 8)
+
+/*
+** The journal header size for this pager. This is usually the same
+** size as a single disk sector. See also setSectorSize().
+*/
+#define JOURNAL_HDR_SZ(pPager) (pPager->sectorSize)
+
+/*
+** The macro MEMDB is true if we are dealing with an in-memory database.
+** We do this as a macro so that if the SQLITE_OMIT_MEMORYDB macro is set,
+** the value of MEMDB will be a constant and the compiler will optimize
+** out code that would never execute.
+*/
+#ifdef SQLITE_OMIT_MEMORYDB
+# define MEMDB 0
+#else
+# define MEMDB pPager->memDb
+#endif
+
+/*
+** The macro USEFETCH is true if we are allowed to use the xFetch and xUnfetch
+** interfaces to access the database using memory-mapped I/O.
+*/
+#if SQLITE_MAX_MMAP_SIZE>0
+# define USEFETCH(x) ((x)->bUseFetch)
+#else
+# define USEFETCH(x) 0
+#endif
+
+/*
+** The argument to this macro is a file descriptor (type sqlite3_file*).
+** Return 0 if it is not open, or non-zero (but not 1) if it is.
+**
+** This is so that expressions can be written as:
+**
+** if( isOpen(pPager->jfd) ){ ...
+**
+** instead of
+**
+** if( pPager->jfd->pMethods ){ ...
+*/
+#define isOpen(pFd) ((pFd)->pMethods!=0)
+
+#ifdef SQLITE_DIRECT_OVERFLOW_READ
+/*
+** Return true if page pgno can be read directly from the database file
+** by the b-tree layer. This is the case if:
+**
+** * the database file is open,
+** * there are no dirty pages in the cache, and
+** * the desired page is not currently in the wal file.
+*/
+int sqlite3PagerDirectReadOk(Pager *pPager, Pgno pgno){
+ if( pPager->fd->pMethods==0 ) return 0;
+ if( sqlite3PCacheIsDirty(pPager->pPCache) ) return 0;
+#ifndef SQLITE_OMIT_WAL
+ if( pPager->pWal ){
+ u32 iRead = 0;
+ (void)sqlite3WalFindFrame(pPager->pWal, pgno, &iRead);
+ return iRead==0;
+ }
+#endif
+ return 1;
+}
+#endif
+
+#ifndef SQLITE_OMIT_WAL
+# define pagerUseWal(x) ((x)->pWal!=0)
+#else
+# define pagerUseWal(x) 0
+# define pagerRollbackWal(x) 0
+# define pagerWalFrames(v,w,x,y) 0
+# define pagerOpenWalIfPresent(z) SQLITE_OK
+# define pagerBeginReadTransaction(z) SQLITE_OK
+#endif
+
+#ifndef NDEBUG
+/*
+** Usage:
+**
+** assert( assert_pager_state(pPager) );
+**
+** This function runs many asserts to try to find inconsistencies in
+** the internal state of the Pager object.
+*/
+static int assert_pager_state(Pager *p){
+ Pager *pPager = p;
+
+ /* State must be valid. */
+ assert( p->eState==PAGER_OPEN
+ || p->eState==PAGER_READER
+ || p->eState==PAGER_WRITER_LOCKED
+ || p->eState==PAGER_WRITER_CACHEMOD
+ || p->eState==PAGER_WRITER_DBMOD
+ || p->eState==PAGER_WRITER_FINISHED
+ || p->eState==PAGER_ERROR
+ );
+
+ /* Regardless of the current state, a temp-file connection always behaves
+ ** as if it has an exclusive lock on the database file. It never updates
+ ** the change-counter field, so the changeCountDone flag is always set.
+ */
+ assert( p->tempFile==0 || p->eLock==EXCLUSIVE_LOCK );
+ assert( p->tempFile==0 || pPager->changeCountDone );
+
+ /* If the useJournal flag is clear, the journal-mode must be "OFF".
+ ** And if the journal-mode is "OFF", the journal file must not be open.
+ */
+ assert( p->journalMode==PAGER_JOURNALMODE_OFF || p->useJournal );
+ assert( p->journalMode!=PAGER_JOURNALMODE_OFF || !isOpen(p->jfd) );
+
+ /* Check that MEMDB implies noSync. And an in-memory journal. Since
+ ** this means an in-memory pager performs no IO at all, it cannot encounter
+ ** either SQLITE_IOERR or SQLITE_FULL during rollback or while finalizing
+ ** a journal file. (although the in-memory journal implementation may
+ ** return SQLITE_IOERR_NOMEM while the journal file is being written). It
+ ** is therefore not possible for an in-memory pager to enter the ERROR
+ ** state.
+ */
+ if( MEMDB ){
+ assert( !isOpen(p->fd) );
+ assert( p->noSync );
+ assert( p->journalMode==PAGER_JOURNALMODE_OFF
+ || p->journalMode==PAGER_JOURNALMODE_MEMORY
+ );
+ assert( p->eState!=PAGER_ERROR && p->eState!=PAGER_OPEN );
+ assert( pagerUseWal(p)==0 );
+ }
+
+ /* If changeCountDone is set, a RESERVED lock or greater must be held
+ ** on the file.
+ */
+ assert( pPager->changeCountDone==0 || pPager->eLock>=RESERVED_LOCK );
+ assert( p->eLock!=PENDING_LOCK );
+
+ switch( p->eState ){
+ case PAGER_OPEN:
+ assert( !MEMDB );
+ assert( pPager->errCode==SQLITE_OK );
+ assert( sqlite3PcacheRefCount(pPager->pPCache)==0 || pPager->tempFile );
+ break;
+
+ case PAGER_READER:
+ assert( pPager->errCode==SQLITE_OK );
+ assert( p->eLock!=UNKNOWN_LOCK );
+ assert( p->eLock>=SHARED_LOCK );
+ break;
+
+ case PAGER_WRITER_LOCKED:
+ assert( p->eLock!=UNKNOWN_LOCK );
+ assert( pPager->errCode==SQLITE_OK );
+ if( !pagerUseWal(pPager) ){
+ assert( p->eLock>=RESERVED_LOCK );
+ }
+ assert( pPager->dbSize==pPager->dbOrigSize );
+ assert( pPager->dbOrigSize==pPager->dbFileSize );
+ assert( pPager->dbOrigSize==pPager->dbHintSize );
+ assert( pPager->setSuper==0 );
+ break;
+
+ case PAGER_WRITER_CACHEMOD:
+ assert( p->eLock!=UNKNOWN_LOCK );
+ assert( pPager->errCode==SQLITE_OK );
+ if( !pagerUseWal(pPager) ){
+ /* It is possible that if journal_mode=wal here that neither the
+ ** journal file nor the WAL file are open. This happens during
+ ** a rollback transaction that switches from journal_mode=off
+ ** to journal_mode=wal.
+ */
+ assert( p->eLock>=RESERVED_LOCK );
+ assert( isOpen(p->jfd)
+ || p->journalMode==PAGER_JOURNALMODE_OFF
+ || p->journalMode==PAGER_JOURNALMODE_WAL
+ );
+ }
+ assert( pPager->dbOrigSize==pPager->dbFileSize );
+ assert( pPager->dbOrigSize==pPager->dbHintSize );
+ break;
+
+ case PAGER_WRITER_DBMOD:
+ assert( p->eLock==EXCLUSIVE_LOCK );
+ assert( pPager->errCode==SQLITE_OK );
+ assert( !pagerUseWal(pPager) );
+ assert( p->eLock>=EXCLUSIVE_LOCK );
+ assert( isOpen(p->jfd)
+ || p->journalMode==PAGER_JOURNALMODE_OFF
+ || p->journalMode==PAGER_JOURNALMODE_WAL
+ || (sqlite3OsDeviceCharacteristics(p->fd)&SQLITE_IOCAP_BATCH_ATOMIC)
+ );
+ assert( pPager->dbOrigSize<=pPager->dbHintSize );
+ break;
+
+ case PAGER_WRITER_FINISHED:
+ assert( p->eLock==EXCLUSIVE_LOCK );
+ assert( pPager->errCode==SQLITE_OK );
+ assert( !pagerUseWal(pPager) );
+ assert( isOpen(p->jfd)
+ || p->journalMode==PAGER_JOURNALMODE_OFF
+ || p->journalMode==PAGER_JOURNALMODE_WAL
+ || (sqlite3OsDeviceCharacteristics(p->fd)&SQLITE_IOCAP_BATCH_ATOMIC)
+ );
+ break;
+
+ case PAGER_ERROR:
+ /* There must be at least one outstanding reference to the pager if
+ ** in ERROR state. Otherwise the pager should have already dropped
+ ** back to OPEN state.
+ */
+ assert( pPager->errCode!=SQLITE_OK );
+ assert( sqlite3PcacheRefCount(pPager->pPCache)>0 || pPager->tempFile );
+ break;
+ }
+
+ return 1;
+}
+#endif /* ifndef NDEBUG */
+
+#ifdef SQLITE_DEBUG
+/*
+** Return a pointer to a human readable string in a static buffer
+** containing the state of the Pager object passed as an argument. This
+** is intended to be used within debuggers. For example, as an alternative
+** to "print *pPager" in gdb:
+**
+** (gdb) printf "%s", print_pager_state(pPager)
+**
+** This routine has external linkage in order to suppress compiler warnings
+** about an unused function. It is enclosed within SQLITE_DEBUG and so does
+** not appear in normal builds.
+*/
+char *print_pager_state(Pager *p){
+ static char zRet[1024];
+
+ sqlite3_snprintf(1024, zRet,
+ "Filename: %s\n"
+ "State: %s errCode=%d\n"
+ "Lock: %s\n"
+ "Locking mode: locking_mode=%s\n"
+ "Journal mode: journal_mode=%s\n"
+ "Backing store: tempFile=%d memDb=%d useJournal=%d\n"
+ "Journal: journalOff=%lld journalHdr=%lld\n"
+ "Size: dbsize=%d dbOrigSize=%d dbFileSize=%d\n"
+ , p->zFilename
+ , p->eState==PAGER_OPEN ? "OPEN" :
+ p->eState==PAGER_READER ? "READER" :
+ p->eState==PAGER_WRITER_LOCKED ? "WRITER_LOCKED" :
+ p->eState==PAGER_WRITER_CACHEMOD ? "WRITER_CACHEMOD" :
+ p->eState==PAGER_WRITER_DBMOD ? "WRITER_DBMOD" :
+ p->eState==PAGER_WRITER_FINISHED ? "WRITER_FINISHED" :
+ p->eState==PAGER_ERROR ? "ERROR" : "?error?"
+ , (int)p->errCode
+ , p->eLock==NO_LOCK ? "NO_LOCK" :
+ p->eLock==RESERVED_LOCK ? "RESERVED" :
+ p->eLock==EXCLUSIVE_LOCK ? "EXCLUSIVE" :
+ p->eLock==SHARED_LOCK ? "SHARED" :
+ p->eLock==UNKNOWN_LOCK ? "UNKNOWN" : "?error?"
+ , p->exclusiveMode ? "exclusive" : "normal"
+ , p->journalMode==PAGER_JOURNALMODE_MEMORY ? "memory" :
+ p->journalMode==PAGER_JOURNALMODE_OFF ? "off" :
+ p->journalMode==PAGER_JOURNALMODE_DELETE ? "delete" :
+ p->journalMode==PAGER_JOURNALMODE_PERSIST ? "persist" :
+ p->journalMode==PAGER_JOURNALMODE_TRUNCATE ? "truncate" :
+ p->journalMode==PAGER_JOURNALMODE_WAL ? "wal" : "?error?"
+ , (int)p->tempFile, (int)p->memDb, (int)p->useJournal
+ , p->journalOff, p->journalHdr
+ , (int)p->dbSize, (int)p->dbOrigSize, (int)p->dbFileSize
+ );
+
+ return zRet;
+}
+#endif
+
+/* Forward references to the various page getters */
+static int getPageNormal(Pager*,Pgno,DbPage**,int);
+static int getPageError(Pager*,Pgno,DbPage**,int);
+#if SQLITE_MAX_MMAP_SIZE>0
+static int getPageMMap(Pager*,Pgno,DbPage**,int);
+#endif
+
+/*
+** Set the Pager.xGet method for the appropriate routine used to fetch
+** content from the pager.
+*/
+static void setGetterMethod(Pager *pPager){
+ if( pPager->errCode ){
+ pPager->xGet = getPageError;
+#if SQLITE_MAX_MMAP_SIZE>0
+ }else if( USEFETCH(pPager) ){
+ pPager->xGet = getPageMMap;
+#endif /* SQLITE_MAX_MMAP_SIZE>0 */
+ }else{
+ pPager->xGet = getPageNormal;
+ }
+}
+
+/*
+** Return true if it is necessary to write page *pPg into the sub-journal.
+** A page needs to be written into the sub-journal if there exists one
+** or more open savepoints for which:
+**
+** * The page-number is less than or equal to PagerSavepoint.nOrig, and
+** * The bit corresponding to the page-number is not set in
+** PagerSavepoint.pInSavepoint.
+*/
+static int subjRequiresPage(PgHdr *pPg){
+ Pager *pPager = pPg->pPager;
+ PagerSavepoint *p;
+ Pgno pgno = pPg->pgno;
+ int i;
+ for(i=0; i<pPager->nSavepoint; i++){
+ p = &pPager->aSavepoint[i];
+ if( p->nOrig>=pgno && 0==sqlite3BitvecTestNotNull(p->pInSavepoint, pgno) ){
+ for(i=i+1; i<pPager->nSavepoint; i++){
+ pPager->aSavepoint[i].bTruncateOnRelease = 0;
+ }
+ return 1;
+ }
+ }
+ return 0;
+}
+
+#ifdef SQLITE_DEBUG
+/*
+** Return true if the page is already in the journal file.
+*/
+static int pageInJournal(Pager *pPager, PgHdr *pPg){
+ return sqlite3BitvecTest(pPager->pInJournal, pPg->pgno);
+}
+#endif
+
+/*
+** Read a 32-bit integer from the given file descriptor. Store the integer
+** that is read in *pRes. Return SQLITE_OK if everything worked, or an
+** error code is something goes wrong.
+**
+** All values are stored on disk as big-endian.
+*/
+static int read32bits(sqlite3_file *fd, i64 offset, u32 *pRes){
+ unsigned char ac[4];
+ int rc = sqlite3OsRead(fd, ac, sizeof(ac), offset);
+ if( rc==SQLITE_OK ){
+ *pRes = sqlite3Get4byte(ac);
+ }
+ return rc;
+}
+
+/*
+** Write a 32-bit integer into a string buffer in big-endian byte order.
+*/
+#define put32bits(A,B) sqlite3Put4byte((u8*)A,B)
+
+
+/*
+** Write a 32-bit integer into the given file descriptor. Return SQLITE_OK
+** on success or an error code is something goes wrong.
+*/
+static int write32bits(sqlite3_file *fd, i64 offset, u32 val){
+ char ac[4];
+ put32bits(ac, val);
+ return sqlite3OsWrite(fd, ac, 4, offset);
+}
+
+/*
+** Unlock the database file to level eLock, which must be either NO_LOCK
+** or SHARED_LOCK. Regardless of whether or not the call to xUnlock()
+** succeeds, set the Pager.eLock variable to match the (attempted) new lock.
+**
+** Except, if Pager.eLock is set to UNKNOWN_LOCK when this function is
+** called, do not modify it. See the comment above the #define of
+** UNKNOWN_LOCK for an explanation of this.
+*/
+static int pagerUnlockDb(Pager *pPager, int eLock){
+ int rc = SQLITE_OK;
+
+ assert( !pPager->exclusiveMode || pPager->eLock==eLock );
+ assert( eLock==NO_LOCK || eLock==SHARED_LOCK );
+ assert( eLock!=NO_LOCK || pagerUseWal(pPager)==0 );
+ if( isOpen(pPager->fd) ){
+ assert( pPager->eLock>=eLock );
+ rc = pPager->noLock ? SQLITE_OK : sqlite3OsUnlock(pPager->fd, eLock);
+ if( pPager->eLock!=UNKNOWN_LOCK ){
+ pPager->eLock = (u8)eLock;
+ }
+ IOTRACE(("UNLOCK %p %d\n", pPager, eLock))
+ }
+ pPager->changeCountDone = pPager->tempFile; /* ticket fb3b3024ea238d5c */
+ return rc;
+}
+
+/*
+** Lock the database file to level eLock, which must be either SHARED_LOCK,
+** RESERVED_LOCK or EXCLUSIVE_LOCK. If the caller is successful, set the
+** Pager.eLock variable to the new locking state.
+**
+** Except, if Pager.eLock is set to UNKNOWN_LOCK when this function is
+** called, do not modify it unless the new locking state is EXCLUSIVE_LOCK.
+** See the comment above the #define of UNKNOWN_LOCK for an explanation
+** of this.
+*/
+static int pagerLockDb(Pager *pPager, int eLock){
+ int rc = SQLITE_OK;
+
+ assert( eLock==SHARED_LOCK || eLock==RESERVED_LOCK || eLock==EXCLUSIVE_LOCK );
+ if( pPager->eLock<eLock || pPager->eLock==UNKNOWN_LOCK ){
+ rc = pPager->noLock ? SQLITE_OK : sqlite3OsLock(pPager->fd, eLock);
+ if( rc==SQLITE_OK && (pPager->eLock!=UNKNOWN_LOCK||eLock==EXCLUSIVE_LOCK) ){
+ pPager->eLock = (u8)eLock;
+ IOTRACE(("LOCK %p %d\n", pPager, eLock))
+ }
+ }
+ return rc;
+}
+
+/*
+** This function determines whether or not the atomic-write or
+** atomic-batch-write optimizations can be used with this pager. The
+** atomic-write optimization can be used if:
+**
+** (a) the value returned by OsDeviceCharacteristics() indicates that
+** a database page may be written atomically, and
+** (b) the value returned by OsSectorSize() is less than or equal
+** to the page size.
+**
+** If it can be used, then the value returned is the size of the journal
+** file when it contains rollback data for exactly one page.
+**
+** The atomic-batch-write optimization can be used if OsDeviceCharacteristics()
+** returns a value with the SQLITE_IOCAP_BATCH_ATOMIC bit set. -1 is
+** returned in this case.
+**
+** If neither optimization can be used, 0 is returned.
+*/
+static int jrnlBufferSize(Pager *pPager){
+ assert( !MEMDB );
+
+#if defined(SQLITE_ENABLE_ATOMIC_WRITE) \
+ || defined(SQLITE_ENABLE_BATCH_ATOMIC_WRITE)
+ int dc; /* Device characteristics */
+
+ assert( isOpen(pPager->fd) );
+ dc = sqlite3OsDeviceCharacteristics(pPager->fd);
+#else
+ UNUSED_PARAMETER(pPager);
+#endif
+
+#ifdef SQLITE_ENABLE_BATCH_ATOMIC_WRITE
+ if( pPager->dbSize>0 && (dc&SQLITE_IOCAP_BATCH_ATOMIC) ){
+ return -1;
+ }
+#endif
+
+#ifdef SQLITE_ENABLE_ATOMIC_WRITE
+ {
+ int nSector = pPager->sectorSize;
+ int szPage = pPager->pageSize;
+
+ assert(SQLITE_IOCAP_ATOMIC512==(512>>8));
+ assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8));
+ if( 0==(dc&(SQLITE_IOCAP_ATOMIC|(szPage>>8)) || nSector>szPage) ){
+ return 0;
+ }
+ }
+
+ return JOURNAL_HDR_SZ(pPager) + JOURNAL_PG_SZ(pPager);
+#endif
+
+ return 0;
+}
+
+/*
+** If SQLITE_CHECK_PAGES is defined then we do some sanity checking
+** on the cache using a hash function. This is used for testing
+** and debugging only.
+*/
+#ifdef SQLITE_CHECK_PAGES
+/*
+** Return a 32-bit hash of the page data for pPage.
+*/
+static u32 pager_datahash(int nByte, unsigned char *pData){
+ u32 hash = 0;
+ int i;
+ for(i=0; i<nByte; i++){
+ hash = (hash*1039) + pData[i];
+ }
+ return hash;
+}
+static u32 pager_pagehash(PgHdr *pPage){
+ return pager_datahash(pPage->pPager->pageSize, (unsigned char *)pPage->pData);
+}
+static void pager_set_pagehash(PgHdr *pPage){
+ pPage->pageHash = pager_pagehash(pPage);
+}
+
+/*
+** The CHECK_PAGE macro takes a PgHdr* as an argument. If SQLITE_CHECK_PAGES
+** is defined, and NDEBUG is not defined, an assert() statement checks
+** that the page is either dirty or still matches the calculated page-hash.
+*/
+#define CHECK_PAGE(x) checkPage(x)
+static void checkPage(PgHdr *pPg){
+ Pager *pPager = pPg->pPager;
+ assert( pPager->eState!=PAGER_ERROR );
+ assert( (pPg->flags&PGHDR_DIRTY) || pPg->pageHash==pager_pagehash(pPg) );
+}
+
+#else
+#define pager_datahash(X,Y) 0
+#define pager_pagehash(X) 0
+#define pager_set_pagehash(X)
+#define CHECK_PAGE(x)
+#endif /* SQLITE_CHECK_PAGES */
+
+/*
+** When this is called the journal file for pager pPager must be open.
+** This function attempts to read a super-journal file name from the
+** end of the file and, if successful, copies it into memory supplied
+** by the caller. See comments above writeSuperJournal() for the format
+** used to store a super-journal file name at the end of a journal file.
+**
+** zSuper must point to a buffer of at least nSuper bytes allocated by
+** the caller. This should be sqlite3_vfs.mxPathname+1 (to ensure there is
+** enough space to write the super-journal name). If the super-journal
+** name in the journal is longer than nSuper bytes (including a
+** nul-terminator), then this is handled as if no super-journal name
+** were present in the journal.
+**
+** If a super-journal file name is present at the end of the journal
+** file, then it is copied into the buffer pointed to by zSuper. A
+** nul-terminator byte is appended to the buffer following the
+** super-journal file name.
+**
+** If it is determined that no super-journal file name is present
+** zSuper[0] is set to 0 and SQLITE_OK returned.
+**
+** If an error occurs while reading from the journal file, an SQLite
+** error code is returned.
+*/
+static int readSuperJournal(sqlite3_file *pJrnl, char *zSuper, u32 nSuper){
+ int rc; /* Return code */
+ u32 len; /* Length in bytes of super-journal name */
+ i64 szJ; /* Total size in bytes of journal file pJrnl */
+ u32 cksum; /* MJ checksum value read from journal */
+ u32 u; /* Unsigned loop counter */
+ unsigned char aMagic[8]; /* A buffer to hold the magic header */
+ zSuper[0] = '\0';
+
+ if( SQLITE_OK!=(rc = sqlite3OsFileSize(pJrnl, &szJ))
+ || szJ<16
+ || SQLITE_OK!=(rc = read32bits(pJrnl, szJ-16, &len))
+ || len>=nSuper
+ || len>szJ-16
+ || len==0
+ || SQLITE_OK!=(rc = read32bits(pJrnl, szJ-12, &cksum))
+ || SQLITE_OK!=(rc = sqlite3OsRead(pJrnl, aMagic, 8, szJ-8))
+ || memcmp(aMagic, aJournalMagic, 8)
+ || SQLITE_OK!=(rc = sqlite3OsRead(pJrnl, zSuper, len, szJ-16-len))
+ ){
+ return rc;
+ }
+
+ /* See if the checksum matches the super-journal name */
+ for(u=0; u<len; u++){
+ cksum -= zSuper[u];
+ }
+ if( cksum ){
+ /* If the checksum doesn't add up, then one or more of the disk sectors
+ ** containing the super-journal filename is corrupted. This means
+ ** definitely roll back, so just return SQLITE_OK and report a (nul)
+ ** super-journal filename.
+ */
+ len = 0;
+ }
+ zSuper[len] = '\0';
+ zSuper[len+1] = '\0';
+
+ return SQLITE_OK;
+}
+
+/*
+** Return the offset of the sector boundary at or immediately
+** following the value in pPager->journalOff, assuming a sector
+** size of pPager->sectorSize bytes.
+**
+** i.e for a sector size of 512:
+**
+** Pager.journalOff Return value
+** ---------------------------------------
+** 0 0
+** 512 512
+** 100 512
+** 2000 2048
+**
+*/
+static i64 journalHdrOffset(Pager *pPager){
+ i64 offset = 0;
+ i64 c = pPager->journalOff;
+ if( c ){
+ offset = ((c-1)/JOURNAL_HDR_SZ(pPager) + 1) * JOURNAL_HDR_SZ(pPager);
+ }
+ assert( offset%JOURNAL_HDR_SZ(pPager)==0 );
+ assert( offset>=c );
+ assert( (offset-c)<JOURNAL_HDR_SZ(pPager) );
+ return offset;
+}
+
+/*
+** The journal file must be open when this function is called.
+**
+** This function is a no-op if the journal file has not been written to
+** within the current transaction (i.e. if Pager.journalOff==0).
+**
+** If doTruncate is non-zero or the Pager.journalSizeLimit variable is
+** set to 0, then truncate the journal file to zero bytes in size. Otherwise,
+** zero the 28-byte header at the start of the journal file. In either case,
+** if the pager is not in no-sync mode, sync the journal file immediately
+** after writing or truncating it.
+**
+** If Pager.journalSizeLimit is set to a positive, non-zero value, and
+** following the truncation or zeroing described above the size of the
+** journal file in bytes is larger than this value, then truncate the
+** journal file to Pager.journalSizeLimit bytes. The journal file does
+** not need to be synced following this operation.
+**
+** If an IO error occurs, abandon processing and return the IO error code.
+** Otherwise, return SQLITE_OK.
+*/
+static int zeroJournalHdr(Pager *pPager, int doTruncate){
+ int rc = SQLITE_OK; /* Return code */
+ assert( isOpen(pPager->jfd) );
+ assert( !sqlite3JournalIsInMemory(pPager->jfd) );
+ if( pPager->journalOff ){
+ const i64 iLimit = pPager->journalSizeLimit; /* Local cache of jsl */
+
+ IOTRACE(("JZEROHDR %p\n", pPager))
+ if( doTruncate || iLimit==0 ){
+ rc = sqlite3OsTruncate(pPager->jfd, 0);
+ }else{
+ static const char zeroHdr[28] = {0};
+ rc = sqlite3OsWrite(pPager->jfd, zeroHdr, sizeof(zeroHdr), 0);
+ }
+ if( rc==SQLITE_OK && !pPager->noSync ){
+ rc = sqlite3OsSync(pPager->jfd, SQLITE_SYNC_DATAONLY|pPager->syncFlags);
+ }
+
+ /* At this point the transaction is committed but the write lock
+ ** is still held on the file. If there is a size limit configured for
+ ** the persistent journal and the journal file currently consumes more
+ ** space than that limit allows for, truncate it now. There is no need
+ ** to sync the file following this operation.
+ */
+ if( rc==SQLITE_OK && iLimit>0 ){
+ i64 sz;
+ rc = sqlite3OsFileSize(pPager->jfd, &sz);
+ if( rc==SQLITE_OK && sz>iLimit ){
+ rc = sqlite3OsTruncate(pPager->jfd, iLimit);
+ }
+ }
+ }
+ return rc;
+}
+
+/*
+** The journal file must be open when this routine is called. A journal
+** header (JOURNAL_HDR_SZ bytes) is written into the journal file at the
+** current location.
+**
+** The format for the journal header is as follows:
+** - 8 bytes: Magic identifying journal format.
+** - 4 bytes: Number of records in journal, or -1 no-sync mode is on.
+** - 4 bytes: Random number used for page hash.
+** - 4 bytes: Initial database page count.
+** - 4 bytes: Sector size used by the process that wrote this journal.
+** - 4 bytes: Database page size.
+**
+** Followed by (JOURNAL_HDR_SZ - 28) bytes of unused space.
+*/
+static int writeJournalHdr(Pager *pPager){
+ int rc = SQLITE_OK; /* Return code */
+ char *zHeader = pPager->pTmpSpace; /* Temporary space used to build header */
+ u32 nHeader = (u32)pPager->pageSize;/* Size of buffer pointed to by zHeader */
+ u32 nWrite; /* Bytes of header sector written */
+ int ii; /* Loop counter */
+
+ assert( isOpen(pPager->jfd) ); /* Journal file must be open. */
+
+ if( nHeader>JOURNAL_HDR_SZ(pPager) ){
+ nHeader = JOURNAL_HDR_SZ(pPager);
+ }
+
+ /* If there are active savepoints and any of them were created
+ ** since the most recent journal header was written, update the
+ ** PagerSavepoint.iHdrOffset fields now.
+ */
+ for(ii=0; ii<pPager->nSavepoint; ii++){
+ if( pPager->aSavepoint[ii].iHdrOffset==0 ){
+ pPager->aSavepoint[ii].iHdrOffset = pPager->journalOff;
+ }
+ }
+
+ pPager->journalHdr = pPager->journalOff = journalHdrOffset(pPager);
+
+ /*
+ ** Write the nRec Field - the number of page records that follow this
+ ** journal header. Normally, zero is written to this value at this time.
+ ** After the records are added to the journal (and the journal synced,
+ ** if in full-sync mode), the zero is overwritten with the true number
+ ** of records (see syncJournal()).
+ **
+ ** A faster alternative is to write 0xFFFFFFFF to the nRec field. When
+ ** reading the journal this value tells SQLite to assume that the
+ ** rest of the journal file contains valid page records. This assumption
+ ** is dangerous, as if a failure occurred whilst writing to the journal
+ ** file it may contain some garbage data. There are two scenarios
+ ** where this risk can be ignored:
+ **
+ ** * When the pager is in no-sync mode. Corruption can follow a
+ ** power failure in this case anyway.
+ **
+ ** * When the SQLITE_IOCAP_SAFE_APPEND flag is set. This guarantees
+ ** that garbage data is never appended to the journal file.
+ */
+ assert( isOpen(pPager->fd) || pPager->noSync );
+ if( pPager->noSync || (pPager->journalMode==PAGER_JOURNALMODE_MEMORY)
+ || (sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_SAFE_APPEND)
+ ){
+ memcpy(zHeader, aJournalMagic, sizeof(aJournalMagic));
+ put32bits(&zHeader[sizeof(aJournalMagic)], 0xffffffff);
+ }else{
+ memset(zHeader, 0, sizeof(aJournalMagic)+4);
+ }
+
+
+
+ /* The random check-hash initializer */
+ if( pPager->journalMode!=PAGER_JOURNALMODE_MEMORY ){
+ sqlite3_randomness(sizeof(pPager->cksumInit), &pPager->cksumInit);
+ }
+#ifdef SQLITE_DEBUG
+ else{
+ /* The Pager.cksumInit variable is usually randomized above to protect
+ ** against there being existing records in the journal file. This is
+ ** dangerous, as following a crash they may be mistaken for records
+ ** written by the current transaction and rolled back into the database
+ ** file, causing corruption. The following assert statements verify
+ ** that this is not required in "journal_mode=memory" mode, as in that
+ ** case the journal file is always 0 bytes in size at this point.
+ ** It is advantageous to avoid the sqlite3_randomness() call if possible
+ ** as it takes the global PRNG mutex. */
+ i64 sz = 0;
+ sqlite3OsFileSize(pPager->jfd, &sz);
+ assert( sz==0 );
+ assert( pPager->journalOff==journalHdrOffset(pPager) );
+ assert( sqlite3JournalIsInMemory(pPager->jfd) );
+ }
+#endif
+ put32bits(&zHeader[sizeof(aJournalMagic)+4], pPager->cksumInit);
+
+ /* The initial database size */
+ put32bits(&zHeader[sizeof(aJournalMagic)+8], pPager->dbOrigSize);
+ /* The assumed sector size for this process */
+ put32bits(&zHeader[sizeof(aJournalMagic)+12], pPager->sectorSize);
+
+ /* The page size */
+ put32bits(&zHeader[sizeof(aJournalMagic)+16], pPager->pageSize);
+
+ /* Initializing the tail of the buffer is not necessary. Everything
+ ** works find if the following memset() is omitted. But initializing
+ ** the memory prevents valgrind from complaining, so we are willing to
+ ** take the performance hit.
+ */
+ memset(&zHeader[sizeof(aJournalMagic)+20], 0,
+ nHeader-(sizeof(aJournalMagic)+20));
+
+ /* In theory, it is only necessary to write the 28 bytes that the
+ ** journal header consumes to the journal file here. Then increment the
+ ** Pager.journalOff variable by JOURNAL_HDR_SZ so that the next
+ ** record is written to the following sector (leaving a gap in the file
+ ** that will be implicitly filled in by the OS).
+ **
+ ** However it has been discovered that on some systems this pattern can
+ ** be significantly slower than contiguously writing data to the file,
+ ** even if that means explicitly writing data to the block of
+ ** (JOURNAL_HDR_SZ - 28) bytes that will not be used. So that is what
+ ** is done.
+ **
+ ** The loop is required here in case the sector-size is larger than the
+ ** database page size. Since the zHeader buffer is only Pager.pageSize
+ ** bytes in size, more than one call to sqlite3OsWrite() may be required
+ ** to populate the entire journal header sector.
+ */
+ for(nWrite=0; rc==SQLITE_OK&&nWrite<JOURNAL_HDR_SZ(pPager); nWrite+=nHeader){
+ IOTRACE(("JHDR %p %lld %d\n", pPager, pPager->journalHdr, nHeader))
+ rc = sqlite3OsWrite(pPager->jfd, zHeader, nHeader, pPager->journalOff);
+ assert( pPager->journalHdr <= pPager->journalOff );
+ pPager->journalOff += nHeader;
+ }
+
+ return rc;
+}
+
+/*
+** The journal file must be open when this is called. A journal header file
+** (JOURNAL_HDR_SZ bytes) is read from the current location in the journal
+** file. The current location in the journal file is given by
+** pPager->journalOff. See comments above function writeJournalHdr() for
+** a description of the journal header format.
+**
+** If the header is read successfully, *pNRec is set to the number of
+** page records following this header and *pDbSize is set to the size of the
+** database before the transaction began, in pages. Also, pPager->cksumInit
+** is set to the value read from the journal header. SQLITE_OK is returned
+** in this case.
+**
+** If the journal header file appears to be corrupted, SQLITE_DONE is
+** returned and *pNRec and *PDbSize are undefined. If JOURNAL_HDR_SZ bytes
+** cannot be read from the journal file an error code is returned.
+*/
+static int readJournalHdr(
+ Pager *pPager, /* Pager object */
+ int isHot,
+ i64 journalSize, /* Size of the open journal file in bytes */
+ u32 *pNRec, /* OUT: Value read from the nRec field */
+ u32 *pDbSize /* OUT: Value of original database size field */
+){
+ int rc; /* Return code */
+ unsigned char aMagic[8]; /* A buffer to hold the magic header */
+ i64 iHdrOff; /* Offset of journal header being read */
+
+ assert( isOpen(pPager->jfd) ); /* Journal file must be open. */
+
+ /* Advance Pager.journalOff to the start of the next sector. If the
+ ** journal file is too small for there to be a header stored at this
+ ** point, return SQLITE_DONE.
+ */
+ pPager->journalOff = journalHdrOffset(pPager);
+ if( pPager->journalOff+JOURNAL_HDR_SZ(pPager) > journalSize ){
+ return SQLITE_DONE;
+ }
+ iHdrOff = pPager->journalOff;
+
+ /* Read in the first 8 bytes of the journal header. If they do not match
+ ** the magic string found at the start of each journal header, return
+ ** SQLITE_DONE. If an IO error occurs, return an error code. Otherwise,
+ ** proceed.
+ */
+ if( isHot || iHdrOff!=pPager->journalHdr ){
+ rc = sqlite3OsRead(pPager->jfd, aMagic, sizeof(aMagic), iHdrOff);
+ if( rc ){
+ return rc;
+ }
+ if( memcmp(aMagic, aJournalMagic, sizeof(aMagic))!=0 ){
+ return SQLITE_DONE;
+ }
+ }
+
+ /* Read the first three 32-bit fields of the journal header: The nRec
+ ** field, the checksum-initializer and the database size at the start
+ ** of the transaction. Return an error code if anything goes wrong.
+ */
+ if( SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+8, pNRec))
+ || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+12, &pPager->cksumInit))
+ || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+16, pDbSize))
+ ){
+ return rc;
+ }
+
+ if( pPager->journalOff==0 ){
+ u32 iPageSize; /* Page-size field of journal header */
+ u32 iSectorSize; /* Sector-size field of journal header */
+
+ /* Read the page-size and sector-size journal header fields. */
+ if( SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+20, &iSectorSize))
+ || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+24, &iPageSize))
+ ){
+ return rc;
+ }
+
+ /* Versions of SQLite prior to 3.5.8 set the page-size field of the
+ ** journal header to zero. In this case, assume that the Pager.pageSize
+ ** variable is already set to the correct page size.
+ */
+ if( iPageSize==0 ){
+ iPageSize = pPager->pageSize;
+ }
+
+ /* Check that the values read from the page-size and sector-size fields
+ ** are within range. To be 'in range', both values need to be a power
+ ** of two greater than or equal to 512 or 32, and not greater than their
+ ** respective compile time maximum limits.
+ */
+ if( iPageSize<512 || iSectorSize<32
+ || iPageSize>SQLITE_MAX_PAGE_SIZE || iSectorSize>MAX_SECTOR_SIZE
+ || ((iPageSize-1)&iPageSize)!=0 || ((iSectorSize-1)&iSectorSize)!=0
+ ){
+ /* If the either the page-size or sector-size in the journal-header is
+ ** invalid, then the process that wrote the journal-header must have
+ ** crashed before the header was synced. In this case stop reading
+ ** the journal file here.
+ */
+ return SQLITE_DONE;
+ }
+
+ /* Update the page-size to match the value read from the journal.
+ ** Use a testcase() macro to make sure that malloc failure within
+ ** PagerSetPagesize() is tested.
+ */
+ rc = sqlite3PagerSetPagesize(pPager, &iPageSize, -1);
+ testcase( rc!=SQLITE_OK );
+
+ /* Update the assumed sector-size to match the value used by
+ ** the process that created this journal. If this journal was
+ ** created by a process other than this one, then this routine
+ ** is being called from within pager_playback(). The local value
+ ** of Pager.sectorSize is restored at the end of that routine.
+ */
+ pPager->sectorSize = iSectorSize;
+ }
+
+ pPager->journalOff += JOURNAL_HDR_SZ(pPager);
+ return rc;
+}
+
+
+/*
+** Write the supplied super-journal name into the journal file for pager
+** pPager at the current location. The super-journal name must be the last
+** thing written to a journal file. If the pager is in full-sync mode, the
+** journal file descriptor is advanced to the next sector boundary before
+** anything is written. The format is:
+**
+** + 4 bytes: PAGER_SJ_PGNO.
+** + N bytes: super-journal filename in utf-8.
+** + 4 bytes: N (length of super-journal name in bytes, no nul-terminator).
+** + 4 bytes: super-journal name checksum.
+** + 8 bytes: aJournalMagic[].
+**
+** The super-journal page checksum is the sum of the bytes in the super-journal
+** name, where each byte is interpreted as a signed 8-bit integer.
+**
+** If zSuper is a NULL pointer (occurs for a single database transaction),
+** this call is a no-op.
+*/
+static int writeSuperJournal(Pager *pPager, const char *zSuper){
+ int rc; /* Return code */
+ int nSuper; /* Length of string zSuper */
+ i64 iHdrOff; /* Offset of header in journal file */
+ i64 jrnlSize; /* Size of journal file on disk */
+ u32 cksum = 0; /* Checksum of string zSuper */
+
+ assert( pPager->setSuper==0 );
+ assert( !pagerUseWal(pPager) );
+
+ if( !zSuper
+ || pPager->journalMode==PAGER_JOURNALMODE_MEMORY
+ || !isOpen(pPager->jfd)
+ ){
+ return SQLITE_OK;
+ }
+ pPager->setSuper = 1;
+ assert( pPager->journalHdr <= pPager->journalOff );
+
+ /* Calculate the length in bytes and the checksum of zSuper */
+ for(nSuper=0; zSuper[nSuper]; nSuper++){
+ cksum += zSuper[nSuper];
+ }
+
+ /* If in full-sync mode, advance to the next disk sector before writing
+ ** the super-journal name. This is in case the previous page written to
+ ** the journal has already been synced.
+ */
+ if( pPager->fullSync ){
+ pPager->journalOff = journalHdrOffset(pPager);
+ }
+ iHdrOff = pPager->journalOff;
+
+ /* Write the super-journal data to the end of the journal file. If
+ ** an error occurs, return the error code to the caller.
+ */
+ if( (0 != (rc = write32bits(pPager->jfd, iHdrOff, PAGER_SJ_PGNO(pPager))))
+ || (0 != (rc = sqlite3OsWrite(pPager->jfd, zSuper, nSuper, iHdrOff+4)))
+ || (0 != (rc = write32bits(pPager->jfd, iHdrOff+4+nSuper, nSuper)))
+ || (0 != (rc = write32bits(pPager->jfd, iHdrOff+4+nSuper+4, cksum)))
+ || (0 != (rc = sqlite3OsWrite(pPager->jfd, aJournalMagic, 8,
+ iHdrOff+4+nSuper+8)))
+ ){
+ return rc;
+ }
+ pPager->journalOff += (nSuper+20);
+
+ /* If the pager is in persistent-journal mode, then the physical
+ ** journal-file may extend past the end of the super-journal name
+ ** and 8 bytes of magic data just written to the file. This is
+ ** dangerous because the code to rollback a hot-journal file
+ ** will not be able to find the super-journal name to determine
+ ** whether or not the journal is hot.
+ **
+ ** Easiest thing to do in this scenario is to truncate the journal
+ ** file to the required size.
+ */
+ if( SQLITE_OK==(rc = sqlite3OsFileSize(pPager->jfd, &jrnlSize))
+ && jrnlSize>pPager->journalOff
+ ){
+ rc = sqlite3OsTruncate(pPager->jfd, pPager->journalOff);
+ }
+ return rc;
+}
+
+/*
+** Discard the entire contents of the in-memory page-cache.
+*/
+static void pager_reset(Pager *pPager){
+ pPager->iDataVersion++;
+ sqlite3BackupRestart(pPager->pBackup);
+ sqlite3PcacheClear(pPager->pPCache);
+}
+
+/*
+** Return the pPager->iDataVersion value
+*/
+u32 sqlite3PagerDataVersion(Pager *pPager){
+ return pPager->iDataVersion;
+}
+
+/*
+** Free all structures in the Pager.aSavepoint[] array and set both
+** Pager.aSavepoint and Pager.nSavepoint to zero. Close the sub-journal
+** if it is open and the pager is not in exclusive mode.
+*/
+static void releaseAllSavepoints(Pager *pPager){
+ int ii; /* Iterator for looping through Pager.aSavepoint */
+ for(ii=0; ii<pPager->nSavepoint; ii++){
+ sqlite3BitvecDestroy(pPager->aSavepoint[ii].pInSavepoint);
+ }
+ if( !pPager->exclusiveMode || sqlite3JournalIsInMemory(pPager->sjfd) ){
+ sqlite3OsClose(pPager->sjfd);
+ }
+ sqlite3_free(pPager->aSavepoint);
+ pPager->aSavepoint = 0;
+ pPager->nSavepoint = 0;
+ pPager->nSubRec = 0;
+}
+
+/*
+** Set the bit number pgno in the PagerSavepoint.pInSavepoint
+** bitvecs of all open savepoints. Return SQLITE_OK if successful
+** or SQLITE_NOMEM if a malloc failure occurs.
+*/
+static int addToSavepointBitvecs(Pager *pPager, Pgno pgno){
+ int ii; /* Loop counter */
+ int rc = SQLITE_OK; /* Result code */
+
+ for(ii=0; ii<pPager->nSavepoint; ii++){
+ PagerSavepoint *p = &pPager->aSavepoint[ii];
+ if( pgno<=p->nOrig ){
+ rc |= sqlite3BitvecSet(p->pInSavepoint, pgno);
+ testcase( rc==SQLITE_NOMEM );
+ assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
+ }
+ }
+ return rc;
+}
+
+/*
+** This function is a no-op if the pager is in exclusive mode and not
+** in the ERROR state. Otherwise, it switches the pager to PAGER_OPEN
+** state.
+**
+** If the pager is not in exclusive-access mode, the database file is
+** completely unlocked. If the file is unlocked and the file-system does
+** not exhibit the UNDELETABLE_WHEN_OPEN property, the journal file is
+** closed (if it is open).
+**
+** If the pager is in ERROR state when this function is called, the
+** contents of the pager cache are discarded before switching back to
+** the OPEN state. Regardless of whether the pager is in exclusive-mode
+** or not, any journal file left in the file-system will be treated
+** as a hot-journal and rolled back the next time a read-transaction
+** is opened (by this or by any other connection).
+*/
+static void pager_unlock(Pager *pPager){
+
+ assert( pPager->eState==PAGER_READER
+ || pPager->eState==PAGER_OPEN
+ || pPager->eState==PAGER_ERROR
+ );
+
+ sqlite3BitvecDestroy(pPager->pInJournal);
+ pPager->pInJournal = 0;
+ releaseAllSavepoints(pPager);
+
+ if( pagerUseWal(pPager) ){
+ assert( !isOpen(pPager->jfd) );
+ sqlite3WalEndReadTransaction(pPager->pWal);
+ pPager->eState = PAGER_OPEN;
+ }else if( !pPager->exclusiveMode ){
+ int rc; /* Error code returned by pagerUnlockDb() */
+ int iDc = isOpen(pPager->fd)?sqlite3OsDeviceCharacteristics(pPager->fd):0;
+
+ /* If the operating system support deletion of open files, then
+ ** close the journal file when dropping the database lock. Otherwise
+ ** another connection with journal_mode=delete might delete the file
+ ** out from under us.
+ */
+ assert( (PAGER_JOURNALMODE_MEMORY & 5)!=1 );
+ assert( (PAGER_JOURNALMODE_OFF & 5)!=1 );
+ assert( (PAGER_JOURNALMODE_WAL & 5)!=1 );
+ assert( (PAGER_JOURNALMODE_DELETE & 5)!=1 );
+ assert( (PAGER_JOURNALMODE_TRUNCATE & 5)==1 );
+ assert( (PAGER_JOURNALMODE_PERSIST & 5)==1 );
+ if( 0==(iDc & SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN)
+ || 1!=(pPager->journalMode & 5)
+ ){
+ sqlite3OsClose(pPager->jfd);
+ }
+
+ /* If the pager is in the ERROR state and the call to unlock the database
+ ** file fails, set the current lock to UNKNOWN_LOCK. See the comment
+ ** above the #define for UNKNOWN_LOCK for an explanation of why this
+ ** is necessary.
+ */
+ rc = pagerUnlockDb(pPager, NO_LOCK);
+ if( rc!=SQLITE_OK && pPager->eState==PAGER_ERROR ){
+ pPager->eLock = UNKNOWN_LOCK;
+ }
+
+ /* The pager state may be changed from PAGER_ERROR to PAGER_OPEN here
+ ** without clearing the error code. This is intentional - the error
+ ** code is cleared and the cache reset in the block below.
+ */
+ assert( pPager->errCode || pPager->eState!=PAGER_ERROR );
+ pPager->eState = PAGER_OPEN;
+ }
+
+ /* If Pager.errCode is set, the contents of the pager cache cannot be
+ ** trusted. Now that there are no outstanding references to the pager,
+ ** it can safely move back to PAGER_OPEN state. This happens in both
+ ** normal and exclusive-locking mode.
+ */
+ assert( pPager->errCode==SQLITE_OK || !MEMDB );
+ if( pPager->errCode ){
+ if( pPager->tempFile==0 ){
+ pager_reset(pPager);
+ pPager->changeCountDone = 0;
+ pPager->eState = PAGER_OPEN;
+ }else{
+ pPager->eState = (isOpen(pPager->jfd) ? PAGER_OPEN : PAGER_READER);
+ }
+ if( USEFETCH(pPager) ) sqlite3OsUnfetch(pPager->fd, 0, 0);
+ pPager->errCode = SQLITE_OK;
+ setGetterMethod(pPager);
+ }
+
+ pPager->journalOff = 0;
+ pPager->journalHdr = 0;
+ pPager->setSuper = 0;
+}
+
+/*
+** This function is called whenever an IOERR or FULL error that requires
+** the pager to transition into the ERROR state may have occurred.
+** The first argument is a pointer to the pager structure, the second
+** the error-code about to be returned by a pager API function. The
+** value returned is a copy of the second argument to this function.
+**
+** If the second argument is SQLITE_FULL, SQLITE_IOERR or one of the
+** IOERR sub-codes, the pager enters the ERROR state and the error code
+** is stored in Pager.errCode. While the pager remains in the ERROR state,
+** all major API calls on the Pager will immediately return Pager.errCode.
+**
+** The ERROR state indicates that the contents of the pager-cache
+** cannot be trusted. This state can be cleared by completely discarding
+** the contents of the pager-cache. If a transaction was active when
+** the persistent error occurred, then the rollback journal may need
+** to be replayed to restore the contents of the database file (as if
+** it were a hot-journal).
+*/
+static int pager_error(Pager *pPager, int rc){
+ int rc2 = rc & 0xff;
+ assert( rc==SQLITE_OK || !MEMDB );
+ assert(
+ pPager->errCode==SQLITE_FULL ||
+ pPager->errCode==SQLITE_OK ||
+ (pPager->errCode & 0xff)==SQLITE_IOERR
+ );
+ if( rc2==SQLITE_FULL || rc2==SQLITE_IOERR ){
+ pPager->errCode = rc;
+ pPager->eState = PAGER_ERROR;
+ setGetterMethod(pPager);
+ }
+ return rc;
+}
+
+static int pager_truncate(Pager *pPager, Pgno nPage);
+
+/*
+** The write transaction open on pPager is being committed (bCommit==1)
+** or rolled back (bCommit==0).
+**
+** Return TRUE if and only if all dirty pages should be flushed to disk.
+**
+** Rules:
+**
+** * For non-TEMP databases, always sync to disk. This is necessary
+** for transactions to be durable.
+**
+** * Sync TEMP database only on a COMMIT (not a ROLLBACK) when the backing
+** file has been created already (via a spill on pagerStress()) and
+** when the number of dirty pages in memory exceeds 25% of the total
+** cache size.
+*/
+static int pagerFlushOnCommit(Pager *pPager, int bCommit){
+ if( pPager->tempFile==0 ) return 1;
+ if( !bCommit ) return 0;
+ if( !isOpen(pPager->fd) ) return 0;
+ return (sqlite3PCachePercentDirty(pPager->pPCache)>=25);
+}
+
+/*
+** This routine ends a transaction. A transaction is usually ended by
+** either a COMMIT or a ROLLBACK operation. This routine may be called
+** after rollback of a hot-journal, or if an error occurs while opening
+** the journal file or writing the very first journal-header of a
+** database transaction.
+**
+** This routine is never called in PAGER_ERROR state. If it is called
+** in PAGER_NONE or PAGER_SHARED state and the lock held is less
+** exclusive than a RESERVED lock, it is a no-op.
+**
+** Otherwise, any active savepoints are released.
+**
+** If the journal file is open, then it is "finalized". Once a journal
+** file has been finalized it is not possible to use it to roll back a
+** transaction. Nor will it be considered to be a hot-journal by this
+** or any other database connection. Exactly how a journal is finalized
+** depends on whether or not the pager is running in exclusive mode and
+** the current journal-mode (Pager.journalMode value), as follows:
+**
+** journalMode==MEMORY
+** Journal file descriptor is simply closed. This destroys an
+** in-memory journal.
+**
+** journalMode==TRUNCATE
+** Journal file is truncated to zero bytes in size.
+**
+** journalMode==PERSIST
+** The first 28 bytes of the journal file are zeroed. This invalidates
+** the first journal header in the file, and hence the entire journal
+** file. An invalid journal file cannot be rolled back.
+**
+** journalMode==DELETE
+** The journal file is closed and deleted using sqlite3OsDelete().
+**
+** If the pager is running in exclusive mode, this method of finalizing
+** the journal file is never used. Instead, if the journalMode is
+** DELETE and the pager is in exclusive mode, the method described under
+** journalMode==PERSIST is used instead.
+**
+** After the journal is finalized, the pager moves to PAGER_READER state.
+** If running in non-exclusive rollback mode, the lock on the file is
+** downgraded to a SHARED_LOCK.
+**
+** SQLITE_OK is returned if no error occurs. If an error occurs during
+** any of the IO operations to finalize the journal file or unlock the
+** database then the IO error code is returned to the user. If the
+** operation to finalize the journal file fails, then the code still
+** tries to unlock the database file if not in exclusive mode. If the
+** unlock operation fails as well, then the first error code related
+** to the first error encountered (the journal finalization one) is
+** returned.
+*/
+static int pager_end_transaction(Pager *pPager, int hasSuper, int bCommit){
+ int rc = SQLITE_OK; /* Error code from journal finalization operation */
+ int rc2 = SQLITE_OK; /* Error code from db file unlock operation */
+
+ /* Do nothing if the pager does not have an open write transaction
+ ** or at least a RESERVED lock. This function may be called when there
+ ** is no write-transaction active but a RESERVED or greater lock is
+ ** held under two circumstances:
+ **
+ ** 1. After a successful hot-journal rollback, it is called with
+ ** eState==PAGER_NONE and eLock==EXCLUSIVE_LOCK.
+ **
+ ** 2. If a connection with locking_mode=exclusive holding an EXCLUSIVE
+ ** lock switches back to locking_mode=normal and then executes a
+ ** read-transaction, this function is called with eState==PAGER_READER
+ ** and eLock==EXCLUSIVE_LOCK when the read-transaction is closed.
+ */
+ assert( assert_pager_state(pPager) );
+ assert( pPager->eState!=PAGER_ERROR );
+ if( pPager->eState<PAGER_WRITER_LOCKED && pPager->eLock<RESERVED_LOCK ){
+ return SQLITE_OK;
+ }
+
+ releaseAllSavepoints(pPager);
+ assert( isOpen(pPager->jfd) || pPager->pInJournal==0
+ || (sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_BATCH_ATOMIC)
+ );
+ if( isOpen(pPager->jfd) ){
+ assert( !pagerUseWal(pPager) );
+
+ /* Finalize the journal file. */
+ if( sqlite3JournalIsInMemory(pPager->jfd) ){
+ /* assert( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ); */
+ sqlite3OsClose(pPager->jfd);
+ }else if( pPager->journalMode==PAGER_JOURNALMODE_TRUNCATE ){
+ if( pPager->journalOff==0 ){
+ rc = SQLITE_OK;
+ }else{
+ rc = sqlite3OsTruncate(pPager->jfd, 0);
+ if( rc==SQLITE_OK && pPager->fullSync ){
+ /* Make sure the new file size is written into the inode right away.
+ ** Otherwise the journal might resurrect following a power loss and
+ ** cause the last transaction to roll back. See
+ ** https://bugzilla.mozilla.org/show_bug.cgi?id=1072773
+ */
+ rc = sqlite3OsSync(pPager->jfd, pPager->syncFlags);
+ }
+ }
+ pPager->journalOff = 0;
+ }else if( pPager->journalMode==PAGER_JOURNALMODE_PERSIST
+ || (pPager->exclusiveMode && pPager->journalMode!=PAGER_JOURNALMODE_WAL)
+ ){
+ rc = zeroJournalHdr(pPager, hasSuper||pPager->tempFile);
+ pPager->journalOff = 0;
+ }else{
+ /* This branch may be executed with Pager.journalMode==MEMORY if
+ ** a hot-journal was just rolled back. In this case the journal
+ ** file should be closed and deleted. If this connection writes to
+ ** the database file, it will do so using an in-memory journal.
+ */
+ int bDelete = !pPager->tempFile;
+ assert( sqlite3JournalIsInMemory(pPager->jfd)==0 );
+ assert( pPager->journalMode==PAGER_JOURNALMODE_DELETE
+ || pPager->journalMode==PAGER_JOURNALMODE_MEMORY
+ || pPager->journalMode==PAGER_JOURNALMODE_WAL
+ );
+ sqlite3OsClose(pPager->jfd);
+ if( bDelete ){
+ rc = sqlite3OsDelete(pPager->pVfs, pPager->zJournal, pPager->extraSync);
+ }
+ }
+ }
+
+#ifdef SQLITE_CHECK_PAGES
+ sqlite3PcacheIterateDirty(pPager->pPCache, pager_set_pagehash);
+ if( pPager->dbSize==0 && sqlite3PcacheRefCount(pPager->pPCache)>0 ){
+ PgHdr *p = sqlite3PagerLookup(pPager, 1);
+ if( p ){
+ p->pageHash = 0;
+ sqlite3PagerUnrefNotNull(p);
+ }
+ }
+#endif
+
+ sqlite3BitvecDestroy(pPager->pInJournal);
+ pPager->pInJournal = 0;
+ pPager->nRec = 0;
+ if( rc==SQLITE_OK ){
+ if( MEMDB || pagerFlushOnCommit(pPager, bCommit) ){
+ sqlite3PcacheCleanAll(pPager->pPCache);
+ }else{
+ sqlite3PcacheClearWritable(pPager->pPCache);
+ }
+ sqlite3PcacheTruncate(pPager->pPCache, pPager->dbSize);
+ }
+
+ if( pagerUseWal(pPager) ){
+ /* Drop the WAL write-lock, if any. Also, if the connection was in
+ ** locking_mode=exclusive mode but is no longer, drop the EXCLUSIVE
+ ** lock held on the database file.
+ */
+ rc2 = sqlite3WalEndWriteTransaction(pPager->pWal);
+ assert( rc2==SQLITE_OK );
+ }else if( rc==SQLITE_OK && bCommit && pPager->dbFileSize>pPager->dbSize ){
+ /* This branch is taken when committing a transaction in rollback-journal
+ ** mode if the database file on disk is larger than the database image.
+ ** At this point the journal has been finalized and the transaction
+ ** successfully committed, but the EXCLUSIVE lock is still held on the
+ ** file. So it is safe to truncate the database file to its minimum
+ ** required size. */
+ assert( pPager->eLock==EXCLUSIVE_LOCK );
+ rc = pager_truncate(pPager, pPager->dbSize);
+ }
+
+ if( rc==SQLITE_OK && bCommit ){
+ rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_COMMIT_PHASETWO, 0);
+ if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK;
+ }
+
+ if( !pPager->exclusiveMode
+ && (!pagerUseWal(pPager) || sqlite3WalExclusiveMode(pPager->pWal, 0))
+ ){
+ rc2 = pagerUnlockDb(pPager, SHARED_LOCK);
+ }
+ pPager->eState = PAGER_READER;
+ pPager->setSuper = 0;
+
+ return (rc==SQLITE_OK?rc2:rc);
+}
+
+/* Forward reference */
+static int pager_playback(Pager *pPager, int isHot);
+
+/*
+** Execute a rollback if a transaction is active and unlock the
+** database file.
+**
+** If the pager has already entered the ERROR state, do not attempt
+** the rollback at this time. Instead, pager_unlock() is called. The
+** call to pager_unlock() will discard all in-memory pages, unlock
+** the database file and move the pager back to OPEN state. If this
+** means that there is a hot-journal left in the file-system, the next
+** connection to obtain a shared lock on the pager (which may be this one)
+** will roll it back.
+**
+** If the pager has not already entered the ERROR state, but an IO or
+** malloc error occurs during a rollback, then this will itself cause
+** the pager to enter the ERROR state. Which will be cleared by the
+** call to pager_unlock(), as described above.
+*/
+static void pagerUnlockAndRollback(Pager *pPager){
+ if( pPager->eState!=PAGER_ERROR && pPager->eState!=PAGER_OPEN ){
+ assert( assert_pager_state(pPager) );
+ if( pPager->eState>=PAGER_WRITER_LOCKED ){
+ sqlite3BeginBenignMalloc();
+ sqlite3PagerRollback(pPager);
+ sqlite3EndBenignMalloc();
+ }else if( !pPager->exclusiveMode ){
+ assert( pPager->eState==PAGER_READER );
+ pager_end_transaction(pPager, 0, 0);
+ }
+ }else if( pPager->eState==PAGER_ERROR
+ && pPager->journalMode==PAGER_JOURNALMODE_MEMORY
+ && isOpen(pPager->jfd)
+ ){
+ /* Special case for a ROLLBACK due to I/O error with an in-memory
+ ** journal: We have to rollback immediately, before the journal is
+ ** closed, because once it is closed, all content is forgotten. */
+ int errCode = pPager->errCode;
+ u8 eLock = pPager->eLock;
+ pPager->eState = PAGER_OPEN;
+ pPager->errCode = SQLITE_OK;
+ pPager->eLock = EXCLUSIVE_LOCK;
+ pager_playback(pPager, 1);
+ pPager->errCode = errCode;
+ pPager->eLock = eLock;
+ }
+ pager_unlock(pPager);
+}
+
+/*
+** Parameter aData must point to a buffer of pPager->pageSize bytes
+** of data. Compute and return a checksum based on the contents of the
+** page of data and the current value of pPager->cksumInit.
+**
+** This is not a real checksum. It is really just the sum of the
+** random initial value (pPager->cksumInit) and every 200th byte
+** of the page data, starting with byte offset (pPager->pageSize%200).
+** Each byte is interpreted as an 8-bit unsigned integer.
+**
+** Changing the formula used to compute this checksum results in an
+** incompatible journal file format.
+**
+** If journal corruption occurs due to a power failure, the most likely
+** scenario is that one end or the other of the record will be changed.
+** It is much less likely that the two ends of the journal record will be
+** correct and the middle be corrupt. Thus, this "checksum" scheme,
+** though fast and simple, catches the mostly likely kind of corruption.
+*/
+static u32 pager_cksum(Pager *pPager, const u8 *aData){
+ u32 cksum = pPager->cksumInit; /* Checksum value to return */
+ int i = pPager->pageSize-200; /* Loop counter */
+ while( i>0 ){
+ cksum += aData[i];
+ i -= 200;
+ }
+ return cksum;
+}
+
+/*
+** Read a single page from either the journal file (if isMainJrnl==1) or
+** from the sub-journal (if isMainJrnl==0) and playback that page.
+** The page begins at offset *pOffset into the file. The *pOffset
+** value is increased to the start of the next page in the journal.
+**
+** The main rollback journal uses checksums - the statement journal does
+** not.
+**
+** If the page number of the page record read from the (sub-)journal file
+** is greater than the current value of Pager.dbSize, then playback is
+** skipped and SQLITE_OK is returned.
+**
+** If pDone is not NULL, then it is a record of pages that have already
+** been played back. If the page at *pOffset has already been played back
+** (if the corresponding pDone bit is set) then skip the playback.
+** Make sure the pDone bit corresponding to the *pOffset page is set
+** prior to returning.
+**
+** If the page record is successfully read from the (sub-)journal file
+** and played back, then SQLITE_OK is returned. If an IO error occurs
+** while reading the record from the (sub-)journal file or while writing
+** to the database file, then the IO error code is returned. If data
+** is successfully read from the (sub-)journal file but appears to be
+** corrupted, SQLITE_DONE is returned. Data is considered corrupted in
+** two circumstances:
+**
+** * If the record page-number is illegal (0 or PAGER_SJ_PGNO), or
+** * If the record is being rolled back from the main journal file
+** and the checksum field does not match the record content.
+**
+** Neither of these two scenarios are possible during a savepoint rollback.
+**
+** If this is a savepoint rollback, then memory may have to be dynamically
+** allocated by this function. If this is the case and an allocation fails,
+** SQLITE_NOMEM is returned.
+*/
+static int pager_playback_one_page(
+ Pager *pPager, /* The pager being played back */
+ i64 *pOffset, /* Offset of record to playback */
+ Bitvec *pDone, /* Bitvec of pages already played back */
+ int isMainJrnl, /* 1 -> main journal. 0 -> sub-journal. */
+ int isSavepnt /* True for a savepoint rollback */
+){
+ int rc;
+ PgHdr *pPg; /* An existing page in the cache */
+ Pgno pgno; /* The page number of a page in journal */
+ u32 cksum; /* Checksum used for sanity checking */
+ char *aData; /* Temporary storage for the page */
+ sqlite3_file *jfd; /* The file descriptor for the journal file */
+ int isSynced; /* True if journal page is synced */
+
+ assert( (isMainJrnl&~1)==0 ); /* isMainJrnl is 0 or 1 */
+ assert( (isSavepnt&~1)==0 ); /* isSavepnt is 0 or 1 */
+ assert( isMainJrnl || pDone ); /* pDone always used on sub-journals */
+ assert( isSavepnt || pDone==0 ); /* pDone never used on non-savepoint */
+
+ aData = pPager->pTmpSpace;
+ assert( aData ); /* Temp storage must have already been allocated */
+ assert( pagerUseWal(pPager)==0 || (!isMainJrnl && isSavepnt) );
+
+ /* Either the state is greater than PAGER_WRITER_CACHEMOD (a transaction
+ ** or savepoint rollback done at the request of the caller) or this is
+ ** a hot-journal rollback. If it is a hot-journal rollback, the pager
+ ** is in state OPEN and holds an EXCLUSIVE lock. Hot-journal rollback
+ ** only reads from the main journal, not the sub-journal.
+ */
+ assert( pPager->eState>=PAGER_WRITER_CACHEMOD
+ || (pPager->eState==PAGER_OPEN && pPager->eLock==EXCLUSIVE_LOCK)
+ );
+ assert( pPager->eState>=PAGER_WRITER_CACHEMOD || isMainJrnl );
+
+ /* Read the page number and page data from the journal or sub-journal
+ ** file. Return an error code to the caller if an IO error occurs.
+ */
+ jfd = isMainJrnl ? pPager->jfd : pPager->sjfd;
+ rc = read32bits(jfd, *pOffset, &pgno);
+ if( rc!=SQLITE_OK ) return rc;
+ rc = sqlite3OsRead(jfd, (u8*)aData, pPager->pageSize, (*pOffset)+4);
+ if( rc!=SQLITE_OK ) return rc;
+ *pOffset += pPager->pageSize + 4 + isMainJrnl*4;
+
+ /* Sanity checking on the page. This is more important that I originally
+ ** thought. If a power failure occurs while the journal is being written,
+ ** it could cause invalid data to be written into the journal. We need to
+ ** detect this invalid data (with high probability) and ignore it.
+ */
+ if( pgno==0 || pgno==PAGER_SJ_PGNO(pPager) ){
+ assert( !isSavepnt );
+ return SQLITE_DONE;
+ }
+ if( pgno>(Pgno)pPager->dbSize || sqlite3BitvecTest(pDone, pgno) ){
+ return SQLITE_OK;
+ }
+ if( isMainJrnl ){
+ rc = read32bits(jfd, (*pOffset)-4, &cksum);
+ if( rc ) return rc;
+ if( !isSavepnt && pager_cksum(pPager, (u8*)aData)!=cksum ){
+ return SQLITE_DONE;
+ }
+ }
+
+ /* If this page has already been played back before during the current
+ ** rollback, then don't bother to play it back again.
+ */
+ if( pDone && (rc = sqlite3BitvecSet(pDone, pgno))!=SQLITE_OK ){
+ return rc;
+ }
+
+ /* When playing back page 1, restore the nReserve setting
+ */
+ if( pgno==1 && pPager->nReserve!=((u8*)aData)[20] ){
+ pPager->nReserve = ((u8*)aData)[20];
+ }
+
+ /* If the pager is in CACHEMOD state, then there must be a copy of this
+ ** page in the pager cache. In this case just update the pager cache,
+ ** not the database file. The page is left marked dirty in this case.
+ **
+ ** An exception to the above rule: If the database is in no-sync mode
+ ** and a page is moved during an incremental vacuum then the page may
+ ** not be in the pager cache. Later: if a malloc() or IO error occurs
+ ** during a Movepage() call, then the page may not be in the cache
+ ** either. So the condition described in the above paragraph is not
+ ** assert()able.
+ **
+ ** If in WRITER_DBMOD, WRITER_FINISHED or OPEN state, then we update the
+ ** pager cache if it exists and the main file. The page is then marked
+ ** not dirty. Since this code is only executed in PAGER_OPEN state for
+ ** a hot-journal rollback, it is guaranteed that the page-cache is empty
+ ** if the pager is in OPEN state.
+ **
+ ** Ticket #1171: The statement journal might contain page content that is
+ ** different from the page content at the start of the transaction.
+ ** This occurs when a page is changed prior to the start of a statement
+ ** then changed again within the statement. When rolling back such a
+ ** statement we must not write to the original database unless we know
+ ** for certain that original page contents are synced into the main rollback
+ ** journal. Otherwise, a power loss might leave modified data in the
+ ** database file without an entry in the rollback journal that can
+ ** restore the database to its original form. Two conditions must be
+ ** met before writing to the database files. (1) the database must be
+ ** locked. (2) we know that the original page content is fully synced
+ ** in the main journal either because the page is not in cache or else
+ ** the page is marked as needSync==0.
+ **
+ ** 2008-04-14: When attempting to vacuum a corrupt database file, it
+ ** is possible to fail a statement on a database that does not yet exist.
+ ** Do not attempt to write if database file has never been opened.
+ */
+ if( pagerUseWal(pPager) ){
+ pPg = 0;
+ }else{
+ pPg = sqlite3PagerLookup(pPager, pgno);
+ }
+ assert( pPg || !MEMDB );
+ assert( pPager->eState!=PAGER_OPEN || pPg==0 || pPager->tempFile );
+ PAGERTRACE(("PLAYBACK %d page %d hash(%08x) %s\n",
+ PAGERID(pPager), pgno, pager_datahash(pPager->pageSize, (u8*)aData),
+ (isMainJrnl?"main-journal":"sub-journal")
+ ));
+ if( isMainJrnl ){
+ isSynced = pPager->noSync || (*pOffset <= pPager->journalHdr);
+ }else{
+ isSynced = (pPg==0 || 0==(pPg->flags & PGHDR_NEED_SYNC));
+ }
+ if( isOpen(pPager->fd)
+ && (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_OPEN)
+ && isSynced
+ ){
+ i64 ofst = (pgno-1)*(i64)pPager->pageSize;
+ testcase( !isSavepnt && pPg!=0 && (pPg->flags&PGHDR_NEED_SYNC)!=0 );
+ assert( !pagerUseWal(pPager) );
+
+ /* Write the data read from the journal back into the database file.
+ ** This is usually safe even for an encrypted database - as the data
+ ** was encrypted before it was written to the journal file. The exception
+ ** is if the data was just read from an in-memory sub-journal. In that
+ ** case it must be encrypted here before it is copied into the database
+ ** file. */
+ rc = sqlite3OsWrite(pPager->fd, (u8 *)aData, pPager->pageSize, ofst);
+
+ if( pgno>pPager->dbFileSize ){
+ pPager->dbFileSize = pgno;
+ }
+ if( pPager->pBackup ){
+ sqlite3BackupUpdate(pPager->pBackup, pgno, (u8*)aData);
+ }
+ }else if( !isMainJrnl && pPg==0 ){
+ /* If this is a rollback of a savepoint and data was not written to
+ ** the database and the page is not in-memory, there is a potential
+ ** problem. When the page is next fetched by the b-tree layer, it
+ ** will be read from the database file, which may or may not be
+ ** current.
+ **
+ ** There are a couple of different ways this can happen. All are quite
+ ** obscure. When running in synchronous mode, this can only happen
+ ** if the page is on the free-list at the start of the transaction, then
+ ** populated, then moved using sqlite3PagerMovepage().
+ **
+ ** The solution is to add an in-memory page to the cache containing
+ ** the data just read from the sub-journal. Mark the page as dirty
+ ** and if the pager requires a journal-sync, then mark the page as
+ ** requiring a journal-sync before it is written.
+ */
+ assert( isSavepnt );
+ assert( (pPager->doNotSpill & SPILLFLAG_ROLLBACK)==0 );
+ pPager->doNotSpill |= SPILLFLAG_ROLLBACK;
+ rc = sqlite3PagerGet(pPager, pgno, &pPg, 1);
+ assert( (pPager->doNotSpill & SPILLFLAG_ROLLBACK)!=0 );
+ pPager->doNotSpill &= ~SPILLFLAG_ROLLBACK;
+ if( rc!=SQLITE_OK ) return rc;
+ sqlite3PcacheMakeDirty(pPg);
+ }
+ if( pPg ){
+ /* No page should ever be explicitly rolled back that is in use, except
+ ** for page 1 which is held in use in order to keep the lock on the
+ ** database active. However such a page may be rolled back as a result
+ ** of an internal error resulting in an automatic call to
+ ** sqlite3PagerRollback().
+ */
+ void *pData;
+ pData = pPg->pData;
+ memcpy(pData, (u8*)aData, pPager->pageSize);
+ pPager->xReiniter(pPg);
+ /* It used to be that sqlite3PcacheMakeClean(pPg) was called here. But
+ ** that call was dangerous and had no detectable benefit since the cache
+ ** is normally cleaned by sqlite3PcacheCleanAll() after rollback and so
+ ** has been removed. */
+ pager_set_pagehash(pPg);
+
+ /* If this was page 1, then restore the value of Pager.dbFileVers.
+ ** Do this before any decoding. */
+ if( pgno==1 ){
+ memcpy(&pPager->dbFileVers, &((u8*)pData)[24],sizeof(pPager->dbFileVers));
+ }
+ sqlite3PcacheRelease(pPg);
+ }
+ return rc;
+}
+
+/*
+** Parameter zSuper is the name of a super-journal file. A single journal
+** file that referred to the super-journal file has just been rolled back.
+** This routine checks if it is possible to delete the super-journal file,
+** and does so if it is.
+**
+** Argument zSuper may point to Pager.pTmpSpace. So that buffer is not
+** available for use within this function.
+**
+** When a super-journal file is created, it is populated with the names
+** of all of its child journals, one after another, formatted as utf-8
+** encoded text. The end of each child journal file is marked with a
+** nul-terminator byte (0x00). i.e. the entire contents of a super-journal
+** file for a transaction involving two databases might be:
+**
+** "/home/bill/a.db-journal\x00/home/bill/b.db-journal\x00"
+**
+** A super-journal file may only be deleted once all of its child
+** journals have been rolled back.
+**
+** This function reads the contents of the super-journal file into
+** memory and loops through each of the child journal names. For
+** each child journal, it checks if:
+**
+** * if the child journal exists, and if so
+** * if the child journal contains a reference to super-journal
+** file zSuper
+**
+** If a child journal can be found that matches both of the criteria
+** above, this function returns without doing anything. Otherwise, if
+** no such child journal can be found, file zSuper is deleted from
+** the file-system using sqlite3OsDelete().
+**
+** If an IO error within this function, an error code is returned. This
+** function allocates memory by calling sqlite3Malloc(). If an allocation
+** fails, SQLITE_NOMEM is returned. Otherwise, if no IO or malloc errors
+** occur, SQLITE_OK is returned.
+**
+** TODO: This function allocates a single block of memory to load
+** the entire contents of the super-journal file. This could be
+** a couple of kilobytes or so - potentially larger than the page
+** size.
+*/
+static int pager_delsuper(Pager *pPager, const char *zSuper){
+ sqlite3_vfs *pVfs = pPager->pVfs;
+ int rc; /* Return code */
+ sqlite3_file *pSuper; /* Malloc'd super-journal file descriptor */
+ sqlite3_file *pJournal; /* Malloc'd child-journal file descriptor */
+ char *zSuperJournal = 0; /* Contents of super-journal file */
+ i64 nSuperJournal; /* Size of super-journal file */
+ char *zJournal; /* Pointer to one journal within MJ file */
+ char *zSuperPtr; /* Space to hold super-journal filename */
+ char *zFree = 0; /* Free this buffer */
+ int nSuperPtr; /* Amount of space allocated to zSuperPtr[] */
+
+ /* Allocate space for both the pJournal and pSuper file descriptors.
+ ** If successful, open the super-journal file for reading.
+ */
+ pSuper = (sqlite3_file *)sqlite3MallocZero(pVfs->szOsFile * 2);
+ if( !pSuper ){
+ rc = SQLITE_NOMEM_BKPT;
+ pJournal = 0;
+ }else{
+ const int flags = (SQLITE_OPEN_READONLY|SQLITE_OPEN_SUPER_JOURNAL);
+ rc = sqlite3OsOpen(pVfs, zSuper, pSuper, flags, 0);
+ pJournal = (sqlite3_file *)(((u8 *)pSuper) + pVfs->szOsFile);
+ }
+ if( rc!=SQLITE_OK ) goto delsuper_out;
+
+ /* Load the entire super-journal file into space obtained from
+ ** sqlite3_malloc() and pointed to by zSuperJournal. Also obtain
+ ** sufficient space (in zSuperPtr) to hold the names of super-journal
+ ** files extracted from regular rollback-journals.
+ */
+ rc = sqlite3OsFileSize(pSuper, &nSuperJournal);
+ if( rc!=SQLITE_OK ) goto delsuper_out;
+ nSuperPtr = pVfs->mxPathname+1;
+ zFree = sqlite3Malloc(4 + nSuperJournal + nSuperPtr + 2);
+ if( !zFree ){
+ rc = SQLITE_NOMEM_BKPT;
+ goto delsuper_out;
+ }
+ zFree[0] = zFree[1] = zFree[2] = zFree[3] = 0;
+ zSuperJournal = &zFree[4];
+ zSuperPtr = &zSuperJournal[nSuperJournal+2];
+ rc = sqlite3OsRead(pSuper, zSuperJournal, (int)nSuperJournal, 0);
+ if( rc!=SQLITE_OK ) goto delsuper_out;
+ zSuperJournal[nSuperJournal] = 0;
+ zSuperJournal[nSuperJournal+1] = 0;
+
+ zJournal = zSuperJournal;
+ while( (zJournal-zSuperJournal)<nSuperJournal ){
+ int exists;
+ rc = sqlite3OsAccess(pVfs, zJournal, SQLITE_ACCESS_EXISTS, &exists);
+ if( rc!=SQLITE_OK ){
+ goto delsuper_out;
+ }
+ if( exists ){
+ /* One of the journals pointed to by the super-journal exists.
+ ** Open it and check if it points at the super-journal. If
+ ** so, return without deleting the super-journal file.
+ ** NB: zJournal is really a MAIN_JOURNAL. But call it a
+ ** SUPER_JOURNAL here so that the VFS will not send the zJournal
+ ** name into sqlite3_database_file_object().
+ */
+ int c;
+ int flags = (SQLITE_OPEN_READONLY|SQLITE_OPEN_SUPER_JOURNAL);
+ rc = sqlite3OsOpen(pVfs, zJournal, pJournal, flags, 0);
+ if( rc!=SQLITE_OK ){
+ goto delsuper_out;
+ }
+
+ rc = readSuperJournal(pJournal, zSuperPtr, nSuperPtr);
+ sqlite3OsClose(pJournal);
+ if( rc!=SQLITE_OK ){
+ goto delsuper_out;
+ }
+
+ c = zSuperPtr[0]!=0 && strcmp(zSuperPtr, zSuper)==0;
+ if( c ){
+ /* We have a match. Do not delete the super-journal file. */
+ goto delsuper_out;
+ }
+ }
+ zJournal += (sqlite3Strlen30(zJournal)+1);
+ }
+
+ sqlite3OsClose(pSuper);
+ rc = sqlite3OsDelete(pVfs, zSuper, 0);
+
+delsuper_out:
+ sqlite3_free(zFree);
+ if( pSuper ){
+ sqlite3OsClose(pSuper);
+ assert( !isOpen(pJournal) );
+ sqlite3_free(pSuper);
+ }
+ return rc;
+}
+
+
+/*
+** This function is used to change the actual size of the database
+** file in the file-system. This only happens when committing a transaction,
+** or rolling back a transaction (including rolling back a hot-journal).
+**
+** If the main database file is not open, or the pager is not in either
+** DBMOD or OPEN state, this function is a no-op. Otherwise, the size
+** of the file is changed to nPage pages (nPage*pPager->pageSize bytes).
+** If the file on disk is currently larger than nPage pages, then use the VFS
+** xTruncate() method to truncate it.
+**
+** Or, it might be the case that the file on disk is smaller than
+** nPage pages. Some operating system implementations can get confused if
+** you try to truncate a file to some size that is larger than it
+** currently is, so detect this case and write a single zero byte to
+** the end of the new file instead.
+**
+** If successful, return SQLITE_OK. If an IO error occurs while modifying
+** the database file, return the error code to the caller.
+*/
+static int pager_truncate(Pager *pPager, Pgno nPage){
+ int rc = SQLITE_OK;
+ assert( pPager->eState!=PAGER_ERROR );
+ assert( pPager->eState!=PAGER_READER );
+ PAGERTRACE(("Truncate %d npage %u\n", PAGERID(pPager), nPage));
+
+
+ if( isOpen(pPager->fd)
+ && (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_OPEN)
+ ){
+ i64 currentSize, newSize;
+ int szPage = pPager->pageSize;
+ assert( pPager->eLock==EXCLUSIVE_LOCK );
+ /* TODO: Is it safe to use Pager.dbFileSize here? */
+ rc = sqlite3OsFileSize(pPager->fd, &currentSize);
+ newSize = szPage*(i64)nPage;
+ if( rc==SQLITE_OK && currentSize!=newSize ){
+ if( currentSize>newSize ){
+ rc = sqlite3OsTruncate(pPager->fd, newSize);
+ }else if( (currentSize+szPage)<=newSize ){
+ char *pTmp = pPager->pTmpSpace;
+ memset(pTmp, 0, szPage);
+ testcase( (newSize-szPage) == currentSize );
+ testcase( (newSize-szPage) > currentSize );
+ sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_SIZE_HINT, &newSize);
+ rc = sqlite3OsWrite(pPager->fd, pTmp, szPage, newSize-szPage);
+ }
+ if( rc==SQLITE_OK ){
+ pPager->dbFileSize = nPage;
+ }
+ }
+ }
+ return rc;
+}
+
+/*
+** Return a sanitized version of the sector-size of OS file pFile. The
+** return value is guaranteed to lie between 32 and MAX_SECTOR_SIZE.
+*/
+int sqlite3SectorSize(sqlite3_file *pFile){
+ int iRet = sqlite3OsSectorSize(pFile);
+ if( iRet<32 ){
+ iRet = 512;
+ }else if( iRet>MAX_SECTOR_SIZE ){
+ assert( MAX_SECTOR_SIZE>=512 );
+ iRet = MAX_SECTOR_SIZE;
+ }
+ return iRet;
+}
+
+/*
+** Set the value of the Pager.sectorSize variable for the given
+** pager based on the value returned by the xSectorSize method
+** of the open database file. The sector size will be used
+** to determine the size and alignment of journal header and
+** super-journal pointers within created journal files.
+**
+** For temporary files the effective sector size is always 512 bytes.
+**
+** Otherwise, for non-temporary files, the effective sector size is
+** the value returned by the xSectorSize() method rounded up to 32 if
+** it is less than 32, or rounded down to MAX_SECTOR_SIZE if it
+** is greater than MAX_SECTOR_SIZE.
+**
+** If the file has the SQLITE_IOCAP_POWERSAFE_OVERWRITE property, then set
+** the effective sector size to its minimum value (512). The purpose of
+** pPager->sectorSize is to define the "blast radius" of bytes that
+** might change if a crash occurs while writing to a single byte in
+** that range. But with POWERSAFE_OVERWRITE, the blast radius is zero
+** (that is what POWERSAFE_OVERWRITE means), so we minimize the sector
+** size. For backwards compatibility of the rollback journal file format,
+** we cannot reduce the effective sector size below 512.
+*/
+static void setSectorSize(Pager *pPager){
+ assert( isOpen(pPager->fd) || pPager->tempFile );
+
+ if( pPager->tempFile
+ || (sqlite3OsDeviceCharacteristics(pPager->fd) &
+ SQLITE_IOCAP_POWERSAFE_OVERWRITE)!=0
+ ){
+ /* Sector size doesn't matter for temporary files. Also, the file
+ ** may not have been opened yet, in which case the OsSectorSize()
+ ** call will segfault. */
+ pPager->sectorSize = 512;
+ }else{
+ pPager->sectorSize = sqlite3SectorSize(pPager->fd);
+ }
+}
+
+/*
+** Playback the journal and thus restore the database file to
+** the state it was in before we started making changes.
+**
+** The journal file format is as follows:
+**
+** (1) 8 byte prefix. A copy of aJournalMagic[].
+** (2) 4 byte big-endian integer which is the number of valid page records
+** in the journal. If this value is 0xffffffff, then compute the
+** number of page records from the journal size.
+** (3) 4 byte big-endian integer which is the initial value for the
+** sanity checksum.
+** (4) 4 byte integer which is the number of pages to truncate the
+** database to during a rollback.
+** (5) 4 byte big-endian integer which is the sector size. The header
+** is this many bytes in size.
+** (6) 4 byte big-endian integer which is the page size.
+** (7) zero padding out to the next sector size.
+** (8) Zero or more pages instances, each as follows:
+** + 4 byte page number.
+** + pPager->pageSize bytes of data.
+** + 4 byte checksum
+**
+** When we speak of the journal header, we mean the first 7 items above.
+** Each entry in the journal is an instance of the 8th item.
+**
+** Call the value from the second bullet "nRec". nRec is the number of
+** valid page entries in the journal. In most cases, you can compute the
+** value of nRec from the size of the journal file. But if a power
+** failure occurred while the journal was being written, it could be the
+** case that the size of the journal file had already been increased but
+** the extra entries had not yet made it safely to disk. In such a case,
+** the value of nRec computed from the file size would be too large. For
+** that reason, we always use the nRec value in the header.
+**
+** If the nRec value is 0xffffffff it means that nRec should be computed
+** from the file size. This value is used when the user selects the
+** no-sync option for the journal. A power failure could lead to corruption
+** in this case. But for things like temporary table (which will be
+** deleted when the power is restored) we don't care.
+**
+** If the file opened as the journal file is not a well-formed
+** journal file then all pages up to the first corrupted page are rolled
+** back (or no pages if the journal header is corrupted). The journal file
+** is then deleted and SQLITE_OK returned, just as if no corruption had
+** been encountered.
+**
+** If an I/O or malloc() error occurs, the journal-file is not deleted
+** and an error code is returned.
+**
+** The isHot parameter indicates that we are trying to rollback a journal
+** that might be a hot journal. Or, it could be that the journal is
+** preserved because of JOURNALMODE_PERSIST or JOURNALMODE_TRUNCATE.
+** If the journal really is hot, reset the pager cache prior rolling
+** back any content. If the journal is merely persistent, no reset is
+** needed.
+*/
+static int pager_playback(Pager *pPager, int isHot){
+ sqlite3_vfs *pVfs = pPager->pVfs;
+ i64 szJ; /* Size of the journal file in bytes */
+ u32 nRec; /* Number of Records in the journal */
+ u32 u; /* Unsigned loop counter */
+ Pgno mxPg = 0; /* Size of the original file in pages */
+ int rc; /* Result code of a subroutine */
+ int res = 1; /* Value returned by sqlite3OsAccess() */
+ char *zSuper = 0; /* Name of super-journal file if any */
+ int needPagerReset; /* True to reset page prior to first page rollback */
+ int nPlayback = 0; /* Total number of pages restored from journal */
+ u32 savedPageSize = pPager->pageSize;
+
+ /* Figure out how many records are in the journal. Abort early if
+ ** the journal is empty.
+ */
+ assert( isOpen(pPager->jfd) );
+ rc = sqlite3OsFileSize(pPager->jfd, &szJ);
+ if( rc!=SQLITE_OK ){
+ goto end_playback;
+ }
+
+ /* Read the super-journal name from the journal, if it is present.
+ ** If a super-journal file name is specified, but the file is not
+ ** present on disk, then the journal is not hot and does not need to be
+ ** played back.
+ **
+ ** TODO: Technically the following is an error because it assumes that
+ ** buffer Pager.pTmpSpace is (mxPathname+1) bytes or larger. i.e. that
+ ** (pPager->pageSize >= pPager->pVfs->mxPathname+1). Using os_unix.c,
+ ** mxPathname is 512, which is the same as the minimum allowable value
+ ** for pageSize.
+ */
+ zSuper = pPager->pTmpSpace;
+ rc = readSuperJournal(pPager->jfd, zSuper, pPager->pVfs->mxPathname+1);
+ if( rc==SQLITE_OK && zSuper[0] ){
+ rc = sqlite3OsAccess(pVfs, zSuper, SQLITE_ACCESS_EXISTS, &res);
+ }
+ zSuper = 0;
+ if( rc!=SQLITE_OK || !res ){
+ goto end_playback;
+ }
+ pPager->journalOff = 0;
+ needPagerReset = isHot;
+
+ /* This loop terminates either when a readJournalHdr() or
+ ** pager_playback_one_page() call returns SQLITE_DONE or an IO error
+ ** occurs.
+ */
+ while( 1 ){
+ /* Read the next journal header from the journal file. If there are
+ ** not enough bytes left in the journal file for a complete header, or
+ ** it is corrupted, then a process must have failed while writing it.
+ ** This indicates nothing more needs to be rolled back.
+ */
+ rc = readJournalHdr(pPager, isHot, szJ, &nRec, &mxPg);
+ if( rc!=SQLITE_OK ){
+ if( rc==SQLITE_DONE ){
+ rc = SQLITE_OK;
+ }
+ goto end_playback;
+ }
+
+ /* If nRec is 0xffffffff, then this journal was created by a process
+ ** working in no-sync mode. This means that the rest of the journal
+ ** file consists of pages, there are no more journal headers. Compute
+ ** the value of nRec based on this assumption.
+ */
+ if( nRec==0xffffffff ){
+ assert( pPager->journalOff==JOURNAL_HDR_SZ(pPager) );
+ nRec = (int)((szJ - JOURNAL_HDR_SZ(pPager))/JOURNAL_PG_SZ(pPager));
+ }
+
+ /* If nRec is 0 and this rollback is of a transaction created by this
+ ** process and if this is the final header in the journal, then it means
+ ** that this part of the journal was being filled but has not yet been
+ ** synced to disk. Compute the number of pages based on the remaining
+ ** size of the file.
+ **
+ ** The third term of the test was added to fix ticket #2565.
+ ** When rolling back a hot journal, nRec==0 always means that the next
+ ** chunk of the journal contains zero pages to be rolled back. But
+ ** when doing a ROLLBACK and the nRec==0 chunk is the last chunk in
+ ** the journal, it means that the journal might contain additional
+ ** pages that need to be rolled back and that the number of pages
+ ** should be computed based on the journal file size.
+ */
+ if( nRec==0 && !isHot &&
+ pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff ){
+ nRec = (int)((szJ - pPager->journalOff) / JOURNAL_PG_SZ(pPager));
+ }
+
+ /* If this is the first header read from the journal, truncate the
+ ** database file back to its original size.
+ */
+ if( pPager->journalOff==JOURNAL_HDR_SZ(pPager) ){
+ rc = pager_truncate(pPager, mxPg);
+ if( rc!=SQLITE_OK ){
+ goto end_playback;
+ }
+ pPager->dbSize = mxPg;
+ if( pPager->mxPgno<mxPg ){
+ pPager->mxPgno = mxPg;
+ }
+ }
+
+ /* Copy original pages out of the journal and back into the
+ ** database file and/or page cache.
+ */
+ for(u=0; u<nRec; u++){
+ if( needPagerReset ){
+ pager_reset(pPager);
+ needPagerReset = 0;
+ }
+ rc = pager_playback_one_page(pPager,&pPager->journalOff,0,1,0);
+ if( rc==SQLITE_OK ){
+ nPlayback++;
+ }else{
+ if( rc==SQLITE_DONE ){
+ pPager->journalOff = szJ;
+ break;
+ }else if( rc==SQLITE_IOERR_SHORT_READ ){
+ /* If the journal has been truncated, simply stop reading and
+ ** processing the journal. This might happen if the journal was
+ ** not completely written and synced prior to a crash. In that
+ ** case, the database should have never been written in the
+ ** first place so it is OK to simply abandon the rollback. */
+ rc = SQLITE_OK;
+ goto end_playback;
+ }else{
+ /* If we are unable to rollback, quit and return the error
+ ** code. This will cause the pager to enter the error state
+ ** so that no further harm will be done. Perhaps the next
+ ** process to come along will be able to rollback the database.
+ */
+ goto end_playback;
+ }
+ }
+ }
+ }
+ /*NOTREACHED*/
+ assert( 0 );
+
+end_playback:
+ if( rc==SQLITE_OK ){
+ rc = sqlite3PagerSetPagesize(pPager, &savedPageSize, -1);
+ }
+ /* Following a rollback, the database file should be back in its original
+ ** state prior to the start of the transaction, so invoke the
+ ** SQLITE_FCNTL_DB_UNCHANGED file-control method to disable the
+ ** assertion that the transaction counter was modified.
+ */
+#ifdef SQLITE_DEBUG
+ sqlite3OsFileControlHint(pPager->fd,SQLITE_FCNTL_DB_UNCHANGED,0);
+#endif
+
+ /* If this playback is happening automatically as a result of an IO or
+ ** malloc error that occurred after the change-counter was updated but
+ ** before the transaction was committed, then the change-counter
+ ** modification may just have been reverted. If this happens in exclusive
+ ** mode, then subsequent transactions performed by the connection will not
+ ** update the change-counter at all. This may lead to cache inconsistency
+ ** problems for other processes at some point in the future. So, just
+ ** in case this has happened, clear the changeCountDone flag now.
+ */
+ pPager->changeCountDone = pPager->tempFile;
+
+ if( rc==SQLITE_OK ){
+ /* Leave 4 bytes of space before the super-journal filename in memory.
+ ** This is because it may end up being passed to sqlite3OsOpen(), in
+ ** which case it requires 4 0x00 bytes in memory immediately before
+ ** the filename. */
+ zSuper = &pPager->pTmpSpace[4];
+ rc = readSuperJournal(pPager->jfd, zSuper, pPager->pVfs->mxPathname+1);
+ testcase( rc!=SQLITE_OK );
+ }
+ if( rc==SQLITE_OK
+ && (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_OPEN)
+ ){
+ rc = sqlite3PagerSync(pPager, 0);
+ }
+ if( rc==SQLITE_OK ){
+ rc = pager_end_transaction(pPager, zSuper[0]!='\0', 0);
+ testcase( rc!=SQLITE_OK );
+ }
+ if( rc==SQLITE_OK && zSuper[0] && res ){
+ /* If there was a super-journal and this routine will return success,
+ ** see if it is possible to delete the super-journal.
+ */
+ assert( zSuper==&pPager->pTmpSpace[4] );
+ memset(pPager->pTmpSpace, 0, 4);
+ rc = pager_delsuper(pPager, zSuper);
+ testcase( rc!=SQLITE_OK );
+ }
+ if( isHot && nPlayback ){
+ sqlite3_log(SQLITE_NOTICE_RECOVER_ROLLBACK, "recovered %d pages from %s",
+ nPlayback, pPager->zJournal);
+ }
+
+ /* The Pager.sectorSize variable may have been updated while rolling
+ ** back a journal created by a process with a different sector size
+ ** value. Reset it to the correct value for this process.
+ */
+ setSectorSize(pPager);
+ return rc;
+}
+
+
+/*
+** Read the content for page pPg out of the database file (or out of
+** the WAL if that is where the most recent copy if found) into
+** pPg->pData. A shared lock or greater must be held on the database
+** file before this function is called.
+**
+** If page 1 is read, then the value of Pager.dbFileVers[] is set to
+** the value read from the database file.
+**
+** If an IO error occurs, then the IO error is returned to the caller.
+** Otherwise, SQLITE_OK is returned.
+*/
+static int readDbPage(PgHdr *pPg){
+ Pager *pPager = pPg->pPager; /* Pager object associated with page pPg */
+ int rc = SQLITE_OK; /* Return code */
+
+#ifndef SQLITE_OMIT_WAL
+ u32 iFrame = 0; /* Frame of WAL containing pgno */
+
+ assert( pPager->eState>=PAGER_READER && !MEMDB );
+ assert( isOpen(pPager->fd) );
+
+ if( pagerUseWal(pPager) ){
+ rc = sqlite3WalFindFrame(pPager->pWal, pPg->pgno, &iFrame);
+ if( rc ) return rc;
+ }
+ if( iFrame ){
+ rc = sqlite3WalReadFrame(pPager->pWal, iFrame,pPager->pageSize,pPg->pData);
+ }else
+#endif
+ {
+ i64 iOffset = (pPg->pgno-1)*(i64)pPager->pageSize;
+ rc = sqlite3OsRead(pPager->fd, pPg->pData, pPager->pageSize, iOffset);
+ if( rc==SQLITE_IOERR_SHORT_READ ){
+ rc = SQLITE_OK;
+ }
+ }
+
+ if( pPg->pgno==1 ){
+ if( rc ){
+ /* If the read is unsuccessful, set the dbFileVers[] to something
+ ** that will never be a valid file version. dbFileVers[] is a copy
+ ** of bytes 24..39 of the database. Bytes 28..31 should always be
+ ** zero or the size of the database in page. Bytes 32..35 and 35..39
+ ** should be page numbers which are never 0xffffffff. So filling
+ ** pPager->dbFileVers[] with all 0xff bytes should suffice.
+ **
+ ** For an encrypted database, the situation is more complex: bytes
+ ** 24..39 of the database are white noise. But the probability of
+ ** white noise equaling 16 bytes of 0xff is vanishingly small so
+ ** we should still be ok.
+ */
+ memset(pPager->dbFileVers, 0xff, sizeof(pPager->dbFileVers));
+ }else{
+ u8 *dbFileVers = &((u8*)pPg->pData)[24];
+ memcpy(&pPager->dbFileVers, dbFileVers, sizeof(pPager->dbFileVers));
+ }
+ }
+ PAGER_INCR(sqlite3_pager_readdb_count);
+ PAGER_INCR(pPager->nRead);
+ IOTRACE(("PGIN %p %d\n", pPager, pPg->pgno));
+ PAGERTRACE(("FETCH %d page %d hash(%08x)\n",
+ PAGERID(pPager), pPg->pgno, pager_pagehash(pPg)));
+
+ return rc;
+}
+
+/*
+** Update the value of the change-counter at offsets 24 and 92 in
+** the header and the sqlite version number at offset 96.
+**
+** This is an unconditional update. See also the pager_incr_changecounter()
+** routine which only updates the change-counter if the update is actually
+** needed, as determined by the pPager->changeCountDone state variable.
+*/
+static void pager_write_changecounter(PgHdr *pPg){
+ u32 change_counter;
+ if( NEVER(pPg==0) ) return;
+
+ /* Increment the value just read and write it back to byte 24. */
+ change_counter = sqlite3Get4byte((u8*)pPg->pPager->dbFileVers)+1;
+ put32bits(((char*)pPg->pData)+24, change_counter);
+
+ /* Also store the SQLite version number in bytes 96..99 and in
+ ** bytes 92..95 store the change counter for which the version number
+ ** is valid. */
+ put32bits(((char*)pPg->pData)+92, change_counter);
+ put32bits(((char*)pPg->pData)+96, SQLITE_VERSION_NUMBER);
+}
+
+#ifndef SQLITE_OMIT_WAL
+/*
+** This function is invoked once for each page that has already been
+** written into the log file when a WAL transaction is rolled back.
+** Parameter iPg is the page number of said page. The pCtx argument
+** is actually a pointer to the Pager structure.
+**
+** If page iPg is present in the cache, and has no outstanding references,
+** it is discarded. Otherwise, if there are one or more outstanding
+** references, the page content is reloaded from the database. If the
+** attempt to reload content from the database is required and fails,
+** return an SQLite error code. Otherwise, SQLITE_OK.
+*/
+static int pagerUndoCallback(void *pCtx, Pgno iPg){
+ int rc = SQLITE_OK;
+ Pager *pPager = (Pager *)pCtx;
+ PgHdr *pPg;
+
+ assert( pagerUseWal(pPager) );
+ pPg = sqlite3PagerLookup(pPager, iPg);
+ if( pPg ){
+ if( sqlite3PcachePageRefcount(pPg)==1 ){
+ sqlite3PcacheDrop(pPg);
+ }else{
+ rc = readDbPage(pPg);
+ if( rc==SQLITE_OK ){
+ pPager->xReiniter(pPg);
+ }
+ sqlite3PagerUnrefNotNull(pPg);
+ }
+ }
+
+ /* Normally, if a transaction is rolled back, any backup processes are
+ ** updated as data is copied out of the rollback journal and into the
+ ** database. This is not generally possible with a WAL database, as
+ ** rollback involves simply truncating the log file. Therefore, if one
+ ** or more frames have already been written to the log (and therefore
+ ** also copied into the backup databases) as part of this transaction,
+ ** the backups must be restarted.
+ */
+ sqlite3BackupRestart(pPager->pBackup);
+
+ return rc;
+}
+
+/*
+** This function is called to rollback a transaction on a WAL database.
+*/
+static int pagerRollbackWal(Pager *pPager){
+ int rc; /* Return Code */
+ PgHdr *pList; /* List of dirty pages to revert */
+
+ /* For all pages in the cache that are currently dirty or have already
+ ** been written (but not committed) to the log file, do one of the
+ ** following:
+ **
+ ** + Discard the cached page (if refcount==0), or
+ ** + Reload page content from the database (if refcount>0).
+ */
+ pPager->dbSize = pPager->dbOrigSize;
+ rc = sqlite3WalUndo(pPager->pWal, pagerUndoCallback, (void *)pPager);
+ pList = sqlite3PcacheDirtyList(pPager->pPCache);
+ while( pList && rc==SQLITE_OK ){
+ PgHdr *pNext = pList->pDirty;
+ rc = pagerUndoCallback((void *)pPager, pList->pgno);
+ pList = pNext;
+ }
+
+ return rc;
+}
+
+/*
+** This function is a wrapper around sqlite3WalFrames(). As well as logging
+** the contents of the list of pages headed by pList (connected by pDirty),
+** this function notifies any active backup processes that the pages have
+** changed.
+**
+** The list of pages passed into this routine is always sorted by page number.
+** Hence, if page 1 appears anywhere on the list, it will be the first page.
+*/
+static int pagerWalFrames(
+ Pager *pPager, /* Pager object */
+ PgHdr *pList, /* List of frames to log */
+ Pgno nTruncate, /* Database size after this commit */
+ int isCommit /* True if this is a commit */
+){
+ int rc; /* Return code */
+ int nList; /* Number of pages in pList */
+ PgHdr *p; /* For looping over pages */
+
+ assert( pPager->pWal );
+ assert( pList );
+#ifdef SQLITE_DEBUG
+ /* Verify that the page list is in ascending order */
+ for(p=pList; p && p->pDirty; p=p->pDirty){
+ assert( p->pgno < p->pDirty->pgno );
+ }
+#endif
+
+ assert( pList->pDirty==0 || isCommit );
+ if( isCommit ){
+ /* If a WAL transaction is being committed, there is no point in writing
+ ** any pages with page numbers greater than nTruncate into the WAL file.
+ ** They will never be read by any client. So remove them from the pDirty
+ ** list here. */
+ PgHdr **ppNext = &pList;
+ nList = 0;
+ for(p=pList; (*ppNext = p)!=0; p=p->pDirty){
+ if( p->pgno<=nTruncate ){
+ ppNext = &p->pDirty;
+ nList++;
+ }
+ }
+ assert( pList );
+ }else{
+ nList = 1;
+ }
+ pPager->aStat[PAGER_STAT_WRITE] += nList;
+
+ if( pList->pgno==1 ) pager_write_changecounter(pList);
+ rc = sqlite3WalFrames(pPager->pWal,
+ pPager->pageSize, pList, nTruncate, isCommit, pPager->walSyncFlags
+ );
+ if( rc==SQLITE_OK && pPager->pBackup ){
+ for(p=pList; p; p=p->pDirty){
+ sqlite3BackupUpdate(pPager->pBackup, p->pgno, (u8 *)p->pData);
+ }
+ }
+
+#ifdef SQLITE_CHECK_PAGES
+ pList = sqlite3PcacheDirtyList(pPager->pPCache);
+ for(p=pList; p; p=p->pDirty){
+ pager_set_pagehash(p);
+ }
+#endif
+
+ return rc;
+}
+
+/*
+** Begin a read transaction on the WAL.
+**
+** This routine used to be called "pagerOpenSnapshot()" because it essentially
+** makes a snapshot of the database at the current point in time and preserves
+** that snapshot for use by the reader in spite of concurrently changes by
+** other writers or checkpointers.
+*/
+static int pagerBeginReadTransaction(Pager *pPager){
+ int rc; /* Return code */
+ int changed = 0; /* True if cache must be reset */
+
+ assert( pagerUseWal(pPager) );
+ assert( pPager->eState==PAGER_OPEN || pPager->eState==PAGER_READER );
+
+ /* sqlite3WalEndReadTransaction() was not called for the previous
+ ** transaction in locking_mode=EXCLUSIVE. So call it now. If we
+ ** are in locking_mode=NORMAL and EndRead() was previously called,
+ ** the duplicate call is harmless.
+ */
+ sqlite3WalEndReadTransaction(pPager->pWal);
+
+ rc = sqlite3WalBeginReadTransaction(pPager->pWal, &changed);
+ if( rc!=SQLITE_OK || changed ){
+ pager_reset(pPager);
+ if( USEFETCH(pPager) ) sqlite3OsUnfetch(pPager->fd, 0, 0);
+ }
+
+ return rc;
+}
+#endif
+
+/*
+** This function is called as part of the transition from PAGER_OPEN
+** to PAGER_READER state to determine the size of the database file
+** in pages (assuming the page size currently stored in Pager.pageSize).
+**
+** If no error occurs, SQLITE_OK is returned and the size of the database
+** in pages is stored in *pnPage. Otherwise, an error code (perhaps
+** SQLITE_IOERR_FSTAT) is returned and *pnPage is left unmodified.
+*/
+static int pagerPagecount(Pager *pPager, Pgno *pnPage){
+ Pgno nPage; /* Value to return via *pnPage */
+
+ /* Query the WAL sub-system for the database size. The WalDbsize()
+ ** function returns zero if the WAL is not open (i.e. Pager.pWal==0), or
+ ** if the database size is not available. The database size is not
+ ** available from the WAL sub-system if the log file is empty or
+ ** contains no valid committed transactions.
+ */
+ assert( pPager->eState==PAGER_OPEN );
+ assert( pPager->eLock>=SHARED_LOCK );
+ assert( isOpen(pPager->fd) );
+ assert( pPager->tempFile==0 );
+ nPage = sqlite3WalDbsize(pPager->pWal);
+
+ /* If the number of pages in the database is not available from the
+ ** WAL sub-system, determine the page count based on the size of
+ ** the database file. If the size of the database file is not an
+ ** integer multiple of the page-size, round up the result.
+ */
+ if( nPage==0 && ALWAYS(isOpen(pPager->fd)) ){
+ i64 n = 0; /* Size of db file in bytes */
+ int rc = sqlite3OsFileSize(pPager->fd, &n);
+ if( rc!=SQLITE_OK ){
+ return rc;
+ }
+ nPage = (Pgno)((n+pPager->pageSize-1) / pPager->pageSize);
+ }
+
+ /* If the current number of pages in the file is greater than the
+ ** configured maximum pager number, increase the allowed limit so
+ ** that the file can be read.
+ */
+ if( nPage>pPager->mxPgno ){
+ pPager->mxPgno = (Pgno)nPage;
+ }
+
+ *pnPage = nPage;
+ return SQLITE_OK;
+}
+
+#ifndef SQLITE_OMIT_WAL
+/*
+** Check if the *-wal file that corresponds to the database opened by pPager
+** exists if the database is not empty, or verify that the *-wal file does
+** not exist (by deleting it) if the database file is empty.
+**
+** If the database is not empty and the *-wal file exists, open the pager
+** in WAL mode. If the database is empty or if no *-wal file exists and
+** if no error occurs, make sure Pager.journalMode is not set to
+** PAGER_JOURNALMODE_WAL.
+**
+** Return SQLITE_OK or an error code.
+**
+** The caller must hold a SHARED lock on the database file to call this
+** function. Because an EXCLUSIVE lock on the db file is required to delete
+** a WAL on a none-empty database, this ensures there is no race condition
+** between the xAccess() below and an xDelete() being executed by some
+** other connection.
+*/
+static int pagerOpenWalIfPresent(Pager *pPager){
+ int rc = SQLITE_OK;
+ assert( pPager->eState==PAGER_OPEN );
+ assert( pPager->eLock>=SHARED_LOCK );
+
+ if( !pPager->tempFile ){
+ int isWal; /* True if WAL file exists */
+ rc = sqlite3OsAccess(
+ pPager->pVfs, pPager->zWal, SQLITE_ACCESS_EXISTS, &isWal
+ );
+ if( rc==SQLITE_OK ){
+ if( isWal ){
+ Pgno nPage; /* Size of the database file */
+
+ rc = pagerPagecount(pPager, &nPage);
+ if( rc ) return rc;
+ if( nPage==0 ){
+ rc = sqlite3OsDelete(pPager->pVfs, pPager->zWal, 0);
+ }else{
+ testcase( sqlite3PcachePagecount(pPager->pPCache)==0 );
+ rc = sqlite3PagerOpenWal(pPager, 0);
+ }
+ }else if( pPager->journalMode==PAGER_JOURNALMODE_WAL ){
+ pPager->journalMode = PAGER_JOURNALMODE_DELETE;
+ }
+ }
+ }
+ return rc;
+}
+#endif
+
+/*
+** Playback savepoint pSavepoint. Or, if pSavepoint==NULL, then playback
+** the entire super-journal file. The case pSavepoint==NULL occurs when
+** a ROLLBACK TO command is invoked on a SAVEPOINT that is a transaction
+** savepoint.
+**
+** When pSavepoint is not NULL (meaning a non-transaction savepoint is
+** being rolled back), then the rollback consists of up to three stages,
+** performed in the order specified:
+**
+** * Pages are played back from the main journal starting at byte
+** offset PagerSavepoint.iOffset and continuing to
+** PagerSavepoint.iHdrOffset, or to the end of the main journal
+** file if PagerSavepoint.iHdrOffset is zero.
+**
+** * If PagerSavepoint.iHdrOffset is not zero, then pages are played
+** back starting from the journal header immediately following
+** PagerSavepoint.iHdrOffset to the end of the main journal file.
+**
+** * Pages are then played back from the sub-journal file, starting
+** with the PagerSavepoint.iSubRec and continuing to the end of
+** the journal file.
+**
+** Throughout the rollback process, each time a page is rolled back, the
+** corresponding bit is set in a bitvec structure (variable pDone in the
+** implementation below). This is used to ensure that a page is only
+** rolled back the first time it is encountered in either journal.
+**
+** If pSavepoint is NULL, then pages are only played back from the main
+** journal file. There is no need for a bitvec in this case.
+**
+** In either case, before playback commences the Pager.dbSize variable
+** is reset to the value that it held at the start of the savepoint
+** (or transaction). No page with a page-number greater than this value
+** is played back. If one is encountered it is simply skipped.
+*/
+static int pagerPlaybackSavepoint(Pager *pPager, PagerSavepoint *pSavepoint){
+ i64 szJ; /* Effective size of the main journal */
+ i64 iHdrOff; /* End of first segment of main-journal records */
+ int rc = SQLITE_OK; /* Return code */
+ Bitvec *pDone = 0; /* Bitvec to ensure pages played back only once */
+
+ assert( pPager->eState!=PAGER_ERROR );
+ assert( pPager->eState>=PAGER_WRITER_LOCKED );
+
+ /* Allocate a bitvec to use to store the set of pages rolled back */
+ if( pSavepoint ){
+ pDone = sqlite3BitvecCreate(pSavepoint->nOrig);
+ if( !pDone ){
+ return SQLITE_NOMEM_BKPT;
+ }
+ }
+
+ /* Set the database size back to the value it was before the savepoint
+ ** being reverted was opened.
+ */
+ pPager->dbSize = pSavepoint ? pSavepoint->nOrig : pPager->dbOrigSize;
+ pPager->changeCountDone = pPager->tempFile;
+
+ if( !pSavepoint && pagerUseWal(pPager) ){
+ return pagerRollbackWal(pPager);
+ }
+
+ /* Use pPager->journalOff as the effective size of the main rollback
+ ** journal. The actual file might be larger than this in
+ ** PAGER_JOURNALMODE_TRUNCATE or PAGER_JOURNALMODE_PERSIST. But anything
+ ** past pPager->journalOff is off-limits to us.
+ */
+ szJ = pPager->journalOff;
+ assert( pagerUseWal(pPager)==0 || szJ==0 );
+
+ /* Begin by rolling back records from the main journal starting at
+ ** PagerSavepoint.iOffset and continuing to the next journal header.
+ ** There might be records in the main journal that have a page number
+ ** greater than the current database size (pPager->dbSize) but those
+ ** will be skipped automatically. Pages are added to pDone as they
+ ** are played back.
+ */
+ if( pSavepoint && !pagerUseWal(pPager) ){
+ iHdrOff = pSavepoint->iHdrOffset ? pSavepoint->iHdrOffset : szJ;
+ pPager->journalOff = pSavepoint->iOffset;
+ while( rc==SQLITE_OK && pPager->journalOff<iHdrOff ){
+ rc = pager_playback_one_page(pPager, &pPager->journalOff, pDone, 1, 1);
+ }
+ assert( rc!=SQLITE_DONE );
+ }else{
+ pPager->journalOff = 0;
+ }
+
+ /* Continue rolling back records out of the main journal starting at
+ ** the first journal header seen and continuing until the effective end
+ ** of the main journal file. Continue to skip out-of-range pages and
+ ** continue adding pages rolled back to pDone.
+ */
+ while( rc==SQLITE_OK && pPager->journalOff<szJ ){
+ u32 ii; /* Loop counter */
+ u32 nJRec = 0; /* Number of Journal Records */
+ u32 dummy;
+ rc = readJournalHdr(pPager, 0, szJ, &nJRec, &dummy);
+ assert( rc!=SQLITE_DONE );
+
+ /*
+ ** The "pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff"
+ ** test is related to ticket #2565. See the discussion in the
+ ** pager_playback() function for additional information.
+ */
+ if( nJRec==0
+ && pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff
+ ){
+ nJRec = (u32)((szJ - pPager->journalOff)/JOURNAL_PG_SZ(pPager));
+ }
+ for(ii=0; rc==SQLITE_OK && ii<nJRec && pPager->journalOff<szJ; ii++){
+ rc = pager_playback_one_page(pPager, &pPager->journalOff, pDone, 1, 1);
+ }
+ assert( rc!=SQLITE_DONE );
+ }
+ assert( rc!=SQLITE_OK || pPager->journalOff>=szJ );
+
+ /* Finally, rollback pages from the sub-journal. Page that were
+ ** previously rolled back out of the main journal (and are hence in pDone)
+ ** will be skipped. Out-of-range pages are also skipped.
+ */
+ if( pSavepoint ){
+ u32 ii; /* Loop counter */
+ i64 offset = (i64)pSavepoint->iSubRec*(4+pPager->pageSize);
+
+ if( pagerUseWal(pPager) ){
+ rc = sqlite3WalSavepointUndo(pPager->pWal, pSavepoint->aWalData);
+ }
+ for(ii=pSavepoint->iSubRec; rc==SQLITE_OK && ii<pPager->nSubRec; ii++){
+ assert( offset==(i64)ii*(4+pPager->pageSize) );
+ rc = pager_playback_one_page(pPager, &offset, pDone, 0, 1);
+ }
+ assert( rc!=SQLITE_DONE );
+ }
+
+ sqlite3BitvecDestroy(pDone);
+ if( rc==SQLITE_OK ){
+ pPager->journalOff = szJ;
+ }
+
+ return rc;
+}
+
+/*
+** Change the maximum number of in-memory pages that are allowed
+** before attempting to recycle clean and unused pages.
+*/
+void sqlite3PagerSetCachesize(Pager *pPager, int mxPage){
+ sqlite3PcacheSetCachesize(pPager->pPCache, mxPage);
+}
+
+/*
+** Change the maximum number of in-memory pages that are allowed
+** before attempting to spill pages to journal.
+*/
+int sqlite3PagerSetSpillsize(Pager *pPager, int mxPage){
+ return sqlite3PcacheSetSpillsize(pPager->pPCache, mxPage);
+}
+
+/*
+** Invoke SQLITE_FCNTL_MMAP_SIZE based on the current value of szMmap.
+*/
+static void pagerFixMaplimit(Pager *pPager){
+#if SQLITE_MAX_MMAP_SIZE>0
+ sqlite3_file *fd = pPager->fd;
+ if( isOpen(fd) && fd->pMethods->iVersion>=3 ){
+ sqlite3_int64 sz;
+ sz = pPager->szMmap;
+ pPager->bUseFetch = (sz>0);
+ setGetterMethod(pPager);
+ sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_MMAP_SIZE, &sz);
+ }
+#endif
+}
+
+/*
+** Change the maximum size of any memory mapping made of the database file.
+*/
+void sqlite3PagerSetMmapLimit(Pager *pPager, sqlite3_int64 szMmap){
+ pPager->szMmap = szMmap;
+ pagerFixMaplimit(pPager);
+}
+
+/*
+** Free as much memory as possible from the pager.
+*/
+void sqlite3PagerShrink(Pager *pPager){
+ sqlite3PcacheShrink(pPager->pPCache);
+}
+
+/*
+** Adjust settings of the pager to those specified in the pgFlags parameter.
+**
+** The "level" in pgFlags & PAGER_SYNCHRONOUS_MASK sets the robustness
+** of the database to damage due to OS crashes or power failures by
+** changing the number of syncs()s when writing the journals.
+** There are four levels:
+**
+** OFF sqlite3OsSync() is never called. This is the default
+** for temporary and transient files.
+**
+** NORMAL The journal is synced once before writes begin on the
+** database. This is normally adequate protection, but
+** it is theoretically possible, though very unlikely,
+** that an inopertune power failure could leave the journal
+** in a state which would cause damage to the database
+** when it is rolled back.
+**
+** FULL The journal is synced twice before writes begin on the
+** database (with some additional information - the nRec field
+** of the journal header - being written in between the two
+** syncs). If we assume that writing a
+** single disk sector is atomic, then this mode provides
+** assurance that the journal will not be corrupted to the
+** point of causing damage to the database during rollback.
+**
+** EXTRA This is like FULL except that is also syncs the directory
+** that contains the rollback journal after the rollback
+** journal is unlinked.
+**
+** The above is for a rollback-journal mode. For WAL mode, OFF continues
+** to mean that no syncs ever occur. NORMAL means that the WAL is synced
+** prior to the start of checkpoint and that the database file is synced
+** at the conclusion of the checkpoint if the entire content of the WAL
+** was written back into the database. But no sync operations occur for
+** an ordinary commit in NORMAL mode with WAL. FULL means that the WAL
+** file is synced following each commit operation, in addition to the
+** syncs associated with NORMAL. There is no difference between FULL
+** and EXTRA for WAL mode.
+**
+** Do not confuse synchronous=FULL with SQLITE_SYNC_FULL. The
+** SQLITE_SYNC_FULL macro means to use the MacOSX-style full-fsync
+** using fcntl(F_FULLFSYNC). SQLITE_SYNC_NORMAL means to do an
+** ordinary fsync() call. There is no difference between SQLITE_SYNC_FULL
+** and SQLITE_SYNC_NORMAL on platforms other than MacOSX. But the
+** synchronous=FULL versus synchronous=NORMAL setting determines when
+** the xSync primitive is called and is relevant to all platforms.
+**
+** Numeric values associated with these states are OFF==1, NORMAL=2,
+** and FULL=3.
+*/
+void sqlite3PagerSetFlags(
+ Pager *pPager, /* The pager to set safety level for */
+ unsigned pgFlags /* Various flags */
+){
+ unsigned level = pgFlags & PAGER_SYNCHRONOUS_MASK;
+ if( pPager->tempFile ){
+ pPager->noSync = 1;
+ pPager->fullSync = 0;
+ pPager->extraSync = 0;
+ }else{
+ pPager->noSync = level==PAGER_SYNCHRONOUS_OFF ?1:0;
+ pPager->fullSync = level>=PAGER_SYNCHRONOUS_FULL ?1:0;
+ pPager->extraSync = level==PAGER_SYNCHRONOUS_EXTRA ?1:0;
+ }
+ if( pPager->noSync ){
+ pPager->syncFlags = 0;
+ }else if( pgFlags & PAGER_FULLFSYNC ){
+ pPager->syncFlags = SQLITE_SYNC_FULL;
+ }else{
+ pPager->syncFlags = SQLITE_SYNC_NORMAL;
+ }
+ pPager->walSyncFlags = (pPager->syncFlags<<2);
+ if( pPager->fullSync ){
+ pPager->walSyncFlags |= pPager->syncFlags;
+ }
+ if( (pgFlags & PAGER_CKPT_FULLFSYNC) && !pPager->noSync ){
+ pPager->walSyncFlags |= (SQLITE_SYNC_FULL<<2);
+ }
+ if( pgFlags & PAGER_CACHESPILL ){
+ pPager->doNotSpill &= ~SPILLFLAG_OFF;
+ }else{
+ pPager->doNotSpill |= SPILLFLAG_OFF;
+ }
+}
+
+/*
+** The following global variable is incremented whenever the library
+** attempts to open a temporary file. This information is used for
+** testing and analysis only.
+*/
+#ifdef SQLITE_TEST
+int sqlite3_opentemp_count = 0;
+#endif
+
+/*
+** Open a temporary file.
+**
+** Write the file descriptor into *pFile. Return SQLITE_OK on success
+** or some other error code if we fail. The OS will automatically
+** delete the temporary file when it is closed.
+**
+** The flags passed to the VFS layer xOpen() call are those specified
+** by parameter vfsFlags ORed with the following:
+**
+** SQLITE_OPEN_READWRITE
+** SQLITE_OPEN_CREATE
+** SQLITE_OPEN_EXCLUSIVE
+** SQLITE_OPEN_DELETEONCLOSE
+*/
+static int pagerOpentemp(
+ Pager *pPager, /* The pager object */
+ sqlite3_file *pFile, /* Write the file descriptor here */
+ int vfsFlags /* Flags passed through to the VFS */
+){
+ int rc; /* Return code */
+
+#ifdef SQLITE_TEST
+ sqlite3_opentemp_count++; /* Used for testing and analysis only */
+#endif
+
+ vfsFlags |= SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE |
+ SQLITE_OPEN_EXCLUSIVE | SQLITE_OPEN_DELETEONCLOSE;
+ rc = sqlite3OsOpen(pPager->pVfs, 0, pFile, vfsFlags, 0);
+ assert( rc!=SQLITE_OK || isOpen(pFile) );
+ return rc;
+}
+
+/*
+** Set the busy handler function.
+**
+** The pager invokes the busy-handler if sqlite3OsLock() returns
+** SQLITE_BUSY when trying to upgrade from no-lock to a SHARED lock,
+** or when trying to upgrade from a RESERVED lock to an EXCLUSIVE
+** lock. It does *not* invoke the busy handler when upgrading from
+** SHARED to RESERVED, or when upgrading from SHARED to EXCLUSIVE
+** (which occurs during hot-journal rollback). Summary:
+**
+** Transition | Invokes xBusyHandler
+** --------------------------------------------------------
+** NO_LOCK -> SHARED_LOCK | Yes
+** SHARED_LOCK -> RESERVED_LOCK | No
+** SHARED_LOCK -> EXCLUSIVE_LOCK | No
+** RESERVED_LOCK -> EXCLUSIVE_LOCK | Yes
+**
+** If the busy-handler callback returns non-zero, the lock is
+** retried. If it returns zero, then the SQLITE_BUSY error is
+** returned to the caller of the pager API function.
+*/
+void sqlite3PagerSetBusyHandler(
+ Pager *pPager, /* Pager object */
+ int (*xBusyHandler)(void *), /* Pointer to busy-handler function */
+ void *pBusyHandlerArg /* Argument to pass to xBusyHandler */
+){
+ void **ap;
+ pPager->xBusyHandler = xBusyHandler;
+ pPager->pBusyHandlerArg = pBusyHandlerArg;
+ ap = (void **)&pPager->xBusyHandler;
+ assert( ((int(*)(void *))(ap[0]))==xBusyHandler );
+ assert( ap[1]==pBusyHandlerArg );
+ sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_BUSYHANDLER, (void *)ap);
+}
+
+/*
+** Change the page size used by the Pager object. The new page size
+** is passed in *pPageSize.
+**
+** If the pager is in the error state when this function is called, it
+** is a no-op. The value returned is the error state error code (i.e.
+** one of SQLITE_IOERR, an SQLITE_IOERR_xxx sub-code or SQLITE_FULL).
+**
+** Otherwise, if all of the following are true:
+**
+** * the new page size (value of *pPageSize) is valid (a power
+** of two between 512 and SQLITE_MAX_PAGE_SIZE, inclusive), and
+**
+** * there are no outstanding page references, and
+**
+** * the database is either not an in-memory database or it is
+** an in-memory database that currently consists of zero pages.
+**
+** then the pager object page size is set to *pPageSize.
+**
+** If the page size is changed, then this function uses sqlite3PagerMalloc()
+** to obtain a new Pager.pTmpSpace buffer. If this allocation attempt
+** fails, SQLITE_NOMEM is returned and the page size remains unchanged.
+** In all other cases, SQLITE_OK is returned.
+**
+** If the page size is not changed, either because one of the enumerated
+** conditions above is not true, the pager was in error state when this
+** function was called, or because the memory allocation attempt failed,
+** then *pPageSize is set to the old, retained page size before returning.
+*/
+int sqlite3PagerSetPagesize(Pager *pPager, u32 *pPageSize, int nReserve){
+ int rc = SQLITE_OK;
+
+ /* It is not possible to do a full assert_pager_state() here, as this
+ ** function may be called from within PagerOpen(), before the state
+ ** of the Pager object is internally consistent.
+ **
+ ** At one point this function returned an error if the pager was in
+ ** PAGER_ERROR state. But since PAGER_ERROR state guarantees that
+ ** there is at least one outstanding page reference, this function
+ ** is a no-op for that case anyhow.
+ */
+
+ u32 pageSize = *pPageSize;
+ assert( pageSize==0 || (pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE) );
+ if( (pPager->memDb==0 || pPager->dbSize==0)
+ && sqlite3PcacheRefCount(pPager->pPCache)==0
+ && pageSize && pageSize!=(u32)pPager->pageSize
+ ){
+ char *pNew = NULL; /* New temp space */
+ i64 nByte = 0;
+
+ if( pPager->eState>PAGER_OPEN && isOpen(pPager->fd) ){
+ rc = sqlite3OsFileSize(pPager->fd, &nByte);
+ }
+ if( rc==SQLITE_OK ){
+ /* 8 bytes of zeroed overrun space is sufficient so that the b-tree
+ * cell header parser will never run off the end of the allocation */
+ pNew = (char *)sqlite3PageMalloc(pageSize+8);
+ if( !pNew ){
+ rc = SQLITE_NOMEM_BKPT;
+ }else{
+ memset(pNew+pageSize, 0, 8);
+ }
+ }
+
+ if( rc==SQLITE_OK ){
+ pager_reset(pPager);
+ rc = sqlite3PcacheSetPageSize(pPager->pPCache, pageSize);
+ }
+ if( rc==SQLITE_OK ){
+ sqlite3PageFree(pPager->pTmpSpace);
+ pPager->pTmpSpace = pNew;
+ pPager->dbSize = (Pgno)((nByte+pageSize-1)/pageSize);
+ pPager->pageSize = pageSize;
+ pPager->lckPgno = (Pgno)(PENDING_BYTE/pageSize) + 1;
+ }else{
+ sqlite3PageFree(pNew);
+ }
+ }
+
+ *pPageSize = pPager->pageSize;
+ if( rc==SQLITE_OK ){
+ if( nReserve<0 ) nReserve = pPager->nReserve;
+ assert( nReserve>=0 && nReserve<1000 );
+ pPager->nReserve = (i16)nReserve;
+ pagerFixMaplimit(pPager);
+ }
+ return rc;
+}
+
+/*
+** Return a pointer to the "temporary page" buffer held internally
+** by the pager. This is a buffer that is big enough to hold the
+** entire content of a database page. This buffer is used internally
+** during rollback and will be overwritten whenever a rollback
+** occurs. But other modules are free to use it too, as long as
+** no rollbacks are happening.
+*/
+void *sqlite3PagerTempSpace(Pager *pPager){
+ return pPager->pTmpSpace;
+}
+
+/*
+** Attempt to set the maximum database page count if mxPage is positive.
+** Make no changes if mxPage is zero or negative. And never reduce the
+** maximum page count below the current size of the database.
+**
+** Regardless of mxPage, return the current maximum page count.
+*/
+Pgno sqlite3PagerMaxPageCount(Pager *pPager, Pgno mxPage){
+ if( mxPage>0 ){
+ pPager->mxPgno = mxPage;
+ }
+ assert( pPager->eState!=PAGER_OPEN ); /* Called only by OP_MaxPgcnt */
+ /* assert( pPager->mxPgno>=pPager->dbSize ); */
+ /* OP_MaxPgcnt ensures that the parameter passed to this function is not
+ ** less than the total number of valid pages in the database. But this
+ ** may be less than Pager.dbSize, and so the assert() above is not valid */
+ return pPager->mxPgno;
+}
+
+/*
+** The following set of routines are used to disable the simulated
+** I/O error mechanism. These routines are used to avoid simulated
+** errors in places where we do not care about errors.
+**
+** Unless -DSQLITE_TEST=1 is used, these routines are all no-ops
+** and generate no code.
+*/
+#ifdef SQLITE_TEST
+extern int sqlite3_io_error_pending;
+extern int sqlite3_io_error_hit;
+static int saved_cnt;
+void disable_simulated_io_errors(void){
+ saved_cnt = sqlite3_io_error_pending;
+ sqlite3_io_error_pending = -1;
+}
+void enable_simulated_io_errors(void){
+ sqlite3_io_error_pending = saved_cnt;
+}
+#else
+# define disable_simulated_io_errors()
+# define enable_simulated_io_errors()
+#endif
+
+/*
+** Read the first N bytes from the beginning of the file into memory
+** that pDest points to.
+**
+** If the pager was opened on a transient file (zFilename==""), or
+** opened on a file less than N bytes in size, the output buffer is
+** zeroed and SQLITE_OK returned. The rationale for this is that this
+** function is used to read database headers, and a new transient or
+** zero sized database has a header than consists entirely of zeroes.
+**
+** If any IO error apart from SQLITE_IOERR_SHORT_READ is encountered,
+** the error code is returned to the caller and the contents of the
+** output buffer undefined.
+*/
+int sqlite3PagerReadFileheader(Pager *pPager, int N, unsigned char *pDest){
+ int rc = SQLITE_OK;
+ memset(pDest, 0, N);
+ assert( isOpen(pPager->fd) || pPager->tempFile );
+
+ /* This routine is only called by btree immediately after creating
+ ** the Pager object. There has not been an opportunity to transition
+ ** to WAL mode yet.
+ */
+ assert( !pagerUseWal(pPager) );
+
+ if( isOpen(pPager->fd) ){
+ IOTRACE(("DBHDR %p 0 %d\n", pPager, N))
+ rc = sqlite3OsRead(pPager->fd, pDest, N, 0);
+ if( rc==SQLITE_IOERR_SHORT_READ ){
+ rc = SQLITE_OK;
+ }
+ }
+ return rc;
+}
+
+/*
+** This function may only be called when a read-transaction is open on
+** the pager. It returns the total number of pages in the database.
+**
+** However, if the file is between 1 and <page-size> bytes in size, then
+** this is considered a 1 page file.
+*/
+void sqlite3PagerPagecount(Pager *pPager, int *pnPage){
+ assert( pPager->eState>=PAGER_READER );
+ assert( pPager->eState!=PAGER_WRITER_FINISHED );
+ *pnPage = (int)pPager->dbSize;
+}
+
+
+/*
+** Try to obtain a lock of type locktype on the database file. If
+** a similar or greater lock is already held, this function is a no-op
+** (returning SQLITE_OK immediately).
+**
+** Otherwise, attempt to obtain the lock using sqlite3OsLock(). Invoke
+** the busy callback if the lock is currently not available. Repeat
+** until the busy callback returns false or until the attempt to
+** obtain the lock succeeds.
+**
+** Return SQLITE_OK on success and an error code if we cannot obtain
+** the lock. If the lock is obtained successfully, set the Pager.state
+** variable to locktype before returning.
+*/
+static int pager_wait_on_lock(Pager *pPager, int locktype){
+ int rc; /* Return code */
+
+ /* Check that this is either a no-op (because the requested lock is
+ ** already held), or one of the transitions that the busy-handler
+ ** may be invoked during, according to the comment above
+ ** sqlite3PagerSetBusyhandler().
+ */
+ assert( (pPager->eLock>=locktype)
+ || (pPager->eLock==NO_LOCK && locktype==SHARED_LOCK)
+ || (pPager->eLock==RESERVED_LOCK && locktype==EXCLUSIVE_LOCK)
+ );
+
+ do {
+ rc = pagerLockDb(pPager, locktype);
+ }while( rc==SQLITE_BUSY && pPager->xBusyHandler(pPager->pBusyHandlerArg) );
+ return rc;
+}
+
+/*
+** Function assertTruncateConstraint(pPager) checks that one of the
+** following is true for all dirty pages currently in the page-cache:
+**
+** a) The page number is less than or equal to the size of the
+** current database image, in pages, OR
+**
+** b) if the page content were written at this time, it would not
+** be necessary to write the current content out to the sub-journal.
+**
+** If the condition asserted by this function were not true, and the
+** dirty page were to be discarded from the cache via the pagerStress()
+** routine, pagerStress() would not write the current page content to
+** the database file. If a savepoint transaction were rolled back after
+** this happened, the correct behavior would be to restore the current
+** content of the page. However, since this content is not present in either
+** the database file or the portion of the rollback journal and
+** sub-journal rolled back the content could not be restored and the
+** database image would become corrupt. It is therefore fortunate that
+** this circumstance cannot arise.
+*/
+#if defined(SQLITE_DEBUG)
+static void assertTruncateConstraintCb(PgHdr *pPg){
+ Pager *pPager = pPg->pPager;
+ assert( pPg->flags&PGHDR_DIRTY );
+ if( pPg->pgno>pPager->dbSize ){ /* if (a) is false */
+ Pgno pgno = pPg->pgno;
+ int i;
+ for(i=0; i<pPg->pPager->nSavepoint; i++){
+ PagerSavepoint *p = &pPager->aSavepoint[i];
+ assert( p->nOrig<pgno || sqlite3BitvecTestNotNull(p->pInSavepoint,pgno) );
+ }
+ }
+}
+static void assertTruncateConstraint(Pager *pPager){
+ sqlite3PcacheIterateDirty(pPager->pPCache, assertTruncateConstraintCb);
+}
+#else
+# define assertTruncateConstraint(pPager)
+#endif
+
+/*
+** Truncate the in-memory database file image to nPage pages. This
+** function does not actually modify the database file on disk. It
+** just sets the internal state of the pager object so that the
+** truncation will be done when the current transaction is committed.
+**
+** This function is only called right before committing a transaction.
+** Once this function has been called, the transaction must either be
+** rolled back or committed. It is not safe to call this function and
+** then continue writing to the database.
+*/
+void sqlite3PagerTruncateImage(Pager *pPager, Pgno nPage){
+ assert( pPager->dbSize>=nPage || CORRUPT_DB );
+ assert( pPager->eState>=PAGER_WRITER_CACHEMOD );
+ pPager->dbSize = nPage;
+
+ /* At one point the code here called assertTruncateConstraint() to
+ ** ensure that all pages being truncated away by this operation are,
+ ** if one or more savepoints are open, present in the savepoint
+ ** journal so that they can be restored if the savepoint is rolled
+ ** back. This is no longer necessary as this function is now only
+ ** called right before committing a transaction. So although the
+ ** Pager object may still have open savepoints (Pager.nSavepoint!=0),
+ ** they cannot be rolled back. So the assertTruncateConstraint() call
+ ** is no longer correct. */
+}
+
+
+/*
+** This function is called before attempting a hot-journal rollback. It
+** syncs the journal file to disk, then sets pPager->journalHdr to the
+** size of the journal file so that the pager_playback() routine knows
+** that the entire journal file has been synced.
+**
+** Syncing a hot-journal to disk before attempting to roll it back ensures
+** that if a power-failure occurs during the rollback, the process that
+** attempts rollback following system recovery sees the same journal
+** content as this process.
+**
+** If everything goes as planned, SQLITE_OK is returned. Otherwise,
+** an SQLite error code.
+*/
+static int pagerSyncHotJournal(Pager *pPager){
+ int rc = SQLITE_OK;
+ if( !pPager->noSync ){
+ rc = sqlite3OsSync(pPager->jfd, SQLITE_SYNC_NORMAL);
+ }
+ if( rc==SQLITE_OK ){
+ rc = sqlite3OsFileSize(pPager->jfd, &pPager->journalHdr);
+ }
+ return rc;
+}
+
+#if SQLITE_MAX_MMAP_SIZE>0
+/*
+** Obtain a reference to a memory mapped page object for page number pgno.
+** The new object will use the pointer pData, obtained from xFetch().
+** If successful, set *ppPage to point to the new page reference
+** and return SQLITE_OK. Otherwise, return an SQLite error code and set
+** *ppPage to zero.
+**
+** Page references obtained by calling this function should be released
+** by calling pagerReleaseMapPage().
+*/
+static int pagerAcquireMapPage(
+ Pager *pPager, /* Pager object */
+ Pgno pgno, /* Page number */
+ void *pData, /* xFetch()'d data for this page */
+ PgHdr **ppPage /* OUT: Acquired page object */
+){
+ PgHdr *p; /* Memory mapped page to return */
+
+ if( pPager->pMmapFreelist ){
+ *ppPage = p = pPager->pMmapFreelist;
+ pPager->pMmapFreelist = p->pDirty;
+ p->pDirty = 0;
+ assert( pPager->nExtra>=8 );
+ memset(p->pExtra, 0, 8);
+ }else{
+ *ppPage = p = (PgHdr *)sqlite3MallocZero(sizeof(PgHdr) + pPager->nExtra);
+ if( p==0 ){
+ sqlite3OsUnfetch(pPager->fd, (i64)(pgno-1) * pPager->pageSize, pData);
+ return SQLITE_NOMEM_BKPT;
+ }
+ p->pExtra = (void *)&p[1];
+ p->flags = PGHDR_MMAP;
+ p->nRef = 1;
+ p->pPager = pPager;
+ }
+
+ assert( p->pExtra==(void *)&p[1] );
+ assert( p->pPage==0 );
+ assert( p->flags==PGHDR_MMAP );
+ assert( p->pPager==pPager );
+ assert( p->nRef==1 );
+
+ p->pgno = pgno;
+ p->pData = pData;
+ pPager->nMmapOut++;
+
+ return SQLITE_OK;
+}
+#endif
+
+/*
+** Release a reference to page pPg. pPg must have been returned by an
+** earlier call to pagerAcquireMapPage().
+*/
+static void pagerReleaseMapPage(PgHdr *pPg){
+ Pager *pPager = pPg->pPager;
+ pPager->nMmapOut--;
+ pPg->pDirty = pPager->pMmapFreelist;
+ pPager->pMmapFreelist = pPg;
+
+ assert( pPager->fd->pMethods->iVersion>=3 );
+ sqlite3OsUnfetch(pPager->fd, (i64)(pPg->pgno-1)*pPager->pageSize, pPg->pData);
+}
+
+/*
+** Free all PgHdr objects stored in the Pager.pMmapFreelist list.
+*/
+static void pagerFreeMapHdrs(Pager *pPager){
+ PgHdr *p;
+ PgHdr *pNext;
+ for(p=pPager->pMmapFreelist; p; p=pNext){
+ pNext = p->pDirty;
+ sqlite3_free(p);
+ }
+}
+
+/* Verify that the database file has not be deleted or renamed out from
+** under the pager. Return SQLITE_OK if the database is still where it ought
+** to be on disk. Return non-zero (SQLITE_READONLY_DBMOVED or some other error
+** code from sqlite3OsAccess()) if the database has gone missing.
+*/
+static int databaseIsUnmoved(Pager *pPager){
+ int bHasMoved = 0;
+ int rc;
+
+ if( pPager->tempFile ) return SQLITE_OK;
+ if( pPager->dbSize==0 ) return SQLITE_OK;
+ assert( pPager->zFilename && pPager->zFilename[0] );
+ rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_HAS_MOVED, &bHasMoved);
+ if( rc==SQLITE_NOTFOUND ){
+ /* If the HAS_MOVED file-control is unimplemented, assume that the file
+ ** has not been moved. That is the historical behavior of SQLite: prior to
+ ** version 3.8.3, it never checked */
+ rc = SQLITE_OK;
+ }else if( rc==SQLITE_OK && bHasMoved ){
+ rc = SQLITE_READONLY_DBMOVED;
+ }
+ return rc;
+}
+
+
+/*
+** Shutdown the page cache. Free all memory and close all files.
+**
+** If a transaction was in progress when this routine is called, that
+** transaction is rolled back. All outstanding pages are invalidated
+** and their memory is freed. Any attempt to use a page associated
+** with this page cache after this function returns will likely
+** result in a coredump.
+**
+** This function always succeeds. If a transaction is active an attempt
+** is made to roll it back. If an error occurs during the rollback
+** a hot journal may be left in the filesystem but no error is returned
+** to the caller.
+*/
+int sqlite3PagerClose(Pager *pPager, sqlite3 *db){
+ u8 *pTmp = (u8*)pPager->pTmpSpace;
+ assert( db || pagerUseWal(pPager)==0 );
+ assert( assert_pager_state(pPager) );
+ disable_simulated_io_errors();
+ sqlite3BeginBenignMalloc();
+ pagerFreeMapHdrs(pPager);
+ /* pPager->errCode = 0; */
+ pPager->exclusiveMode = 0;
+#ifndef SQLITE_OMIT_WAL
+ {
+ u8 *a = 0;
+ assert( db || pPager->pWal==0 );
+ if( db && 0==(db->flags & SQLITE_NoCkptOnClose)
+ && SQLITE_OK==databaseIsUnmoved(pPager)
+ ){
+ a = pTmp;
+ }
+ sqlite3WalClose(pPager->pWal, db, pPager->walSyncFlags, pPager->pageSize,a);
+ pPager->pWal = 0;
+ }
+#endif
+ pager_reset(pPager);
+ if( MEMDB ){
+ pager_unlock(pPager);
+ }else{
+ /* If it is open, sync the journal file before calling UnlockAndRollback.
+ ** If this is not done, then an unsynced portion of the open journal
+ ** file may be played back into the database. If a power failure occurs
+ ** while this is happening, the database could become corrupt.
+ **
+ ** If an error occurs while trying to sync the journal, shift the pager
+ ** into the ERROR state. This causes UnlockAndRollback to unlock the
+ ** database and close the journal file without attempting to roll it
+ ** back or finalize it. The next database user will have to do hot-journal
+ ** rollback before accessing the database file.
+ */
+ if( isOpen(pPager->jfd) ){
+ pager_error(pPager, pagerSyncHotJournal(pPager));
+ }
+ pagerUnlockAndRollback(pPager);
+ }
+ sqlite3EndBenignMalloc();
+ enable_simulated_io_errors();
+ PAGERTRACE(("CLOSE %d\n", PAGERID(pPager)));
+ IOTRACE(("CLOSE %p\n", pPager))
+ sqlite3OsClose(pPager->jfd);
+ sqlite3OsClose(pPager->fd);
+ sqlite3PageFree(pTmp);
+ sqlite3PcacheClose(pPager->pPCache);
+ assert( !pPager->aSavepoint && !pPager->pInJournal );
+ assert( !isOpen(pPager->jfd) && !isOpen(pPager->sjfd) );
+
+ sqlite3_free(pPager);
+ return SQLITE_OK;
+}
+
+#if !defined(NDEBUG) || defined(SQLITE_TEST)
+/*
+** Return the page number for page pPg.
+*/
+Pgno sqlite3PagerPagenumber(DbPage *pPg){
+ return pPg->pgno;
+}
+#endif
+
+/*
+** Increment the reference count for page pPg.
+*/
+void sqlite3PagerRef(DbPage *pPg){
+ sqlite3PcacheRef(pPg);
+}
+
+/*
+** Sync the journal. In other words, make sure all the pages that have
+** been written to the journal have actually reached the surface of the
+** disk and can be restored in the event of a hot-journal rollback.
+**
+** If the Pager.noSync flag is set, then this function is a no-op.
+** Otherwise, the actions required depend on the journal-mode and the
+** device characteristics of the file-system, as follows:
+**
+** * If the journal file is an in-memory journal file, no action need
+** be taken.
+**
+** * Otherwise, if the device does not support the SAFE_APPEND property,
+** then the nRec field of the most recently written journal header
+** is updated to contain the number of journal records that have
+** been written following it. If the pager is operating in full-sync
+** mode, then the journal file is synced before this field is updated.
+**
+** * If the device does not support the SEQUENTIAL property, then
+** journal file is synced.
+**
+** Or, in pseudo-code:
+**
+** if( NOT <in-memory journal> ){
+** if( NOT SAFE_APPEND ){
+** if( <full-sync mode> ) xSync(<journal file>);
+** <update nRec field>
+** }
+** if( NOT SEQUENTIAL ) xSync(<journal file>);
+** }
+**
+** If successful, this routine clears the PGHDR_NEED_SYNC flag of every
+** page currently held in memory before returning SQLITE_OK. If an IO
+** error is encountered, then the IO error code is returned to the caller.
+*/
+static int syncJournal(Pager *pPager, int newHdr){
+ int rc; /* Return code */
+
+ assert( pPager->eState==PAGER_WRITER_CACHEMOD
+ || pPager->eState==PAGER_WRITER_DBMOD
+ );
+ assert( assert_pager_state(pPager) );
+ assert( !pagerUseWal(pPager) );
+
+ rc = sqlite3PagerExclusiveLock(pPager);
+ if( rc!=SQLITE_OK ) return rc;
+
+ if( !pPager->noSync ){
+ assert( !pPager->tempFile );
+ if( isOpen(pPager->jfd) && pPager->journalMode!=PAGER_JOURNALMODE_MEMORY ){
+ const int iDc = sqlite3OsDeviceCharacteristics(pPager->fd);
+ assert( isOpen(pPager->jfd) );
+
+ if( 0==(iDc&SQLITE_IOCAP_SAFE_APPEND) ){
+ /* This block deals with an obscure problem. If the last connection
+ ** that wrote to this database was operating in persistent-journal
+ ** mode, then the journal file may at this point actually be larger
+ ** than Pager.journalOff bytes. If the next thing in the journal
+ ** file happens to be a journal-header (written as part of the
+ ** previous connection's transaction), and a crash or power-failure
+ ** occurs after nRec is updated but before this connection writes
+ ** anything else to the journal file (or commits/rolls back its
+ ** transaction), then SQLite may become confused when doing the
+ ** hot-journal rollback following recovery. It may roll back all
+ ** of this connections data, then proceed to rolling back the old,
+ ** out-of-date data that follows it. Database corruption.
+ **
+ ** To work around this, if the journal file does appear to contain
+ ** a valid header following Pager.journalOff, then write a 0x00
+ ** byte to the start of it to prevent it from being recognized.
+ **
+ ** Variable iNextHdrOffset is set to the offset at which this
+ ** problematic header will occur, if it exists. aMagic is used
+ ** as a temporary buffer to inspect the first couple of bytes of
+ ** the potential journal header.
+ */
+ i64 iNextHdrOffset;
+ u8 aMagic[8];
+ u8 zHeader[sizeof(aJournalMagic)+4];
+
+ memcpy(zHeader, aJournalMagic, sizeof(aJournalMagic));
+ put32bits(&zHeader[sizeof(aJournalMagic)], pPager->nRec);
+
+ iNextHdrOffset = journalHdrOffset(pPager);
+ rc = sqlite3OsRead(pPager->jfd, aMagic, 8, iNextHdrOffset);
+ if( rc==SQLITE_OK && 0==memcmp(aMagic, aJournalMagic, 8) ){
+ static const u8 zerobyte = 0;
+ rc = sqlite3OsWrite(pPager->jfd, &zerobyte, 1, iNextHdrOffset);
+ }
+ if( rc!=SQLITE_OK && rc!=SQLITE_IOERR_SHORT_READ ){
+ return rc;
+ }
+
+ /* Write the nRec value into the journal file header. If in
+ ** full-synchronous mode, sync the journal first. This ensures that
+ ** all data has really hit the disk before nRec is updated to mark
+ ** it as a candidate for rollback.
+ **
+ ** This is not required if the persistent media supports the
+ ** SAFE_APPEND property. Because in this case it is not possible
+ ** for garbage data to be appended to the file, the nRec field
+ ** is populated with 0xFFFFFFFF when the journal header is written
+ ** and never needs to be updated.
+ */
+ if( pPager->fullSync && 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){
+ PAGERTRACE(("SYNC journal of %d\n", PAGERID(pPager)));
+ IOTRACE(("JSYNC %p\n", pPager))
+ rc = sqlite3OsSync(pPager->jfd, pPager->syncFlags);
+ if( rc!=SQLITE_OK ) return rc;
+ }
+ IOTRACE(("JHDR %p %lld\n", pPager, pPager->journalHdr));
+ rc = sqlite3OsWrite(
+ pPager->jfd, zHeader, sizeof(zHeader), pPager->journalHdr
+ );
+ if( rc!=SQLITE_OK ) return rc;
+ }
+ if( 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){
+ PAGERTRACE(("SYNC journal of %d\n", PAGERID(pPager)));
+ IOTRACE(("JSYNC %p\n", pPager))
+ rc = sqlite3OsSync(pPager->jfd, pPager->syncFlags|
+ (pPager->syncFlags==SQLITE_SYNC_FULL?SQLITE_SYNC_DATAONLY:0)
+ );
+ if( rc!=SQLITE_OK ) return rc;
+ }
+
+ pPager->journalHdr = pPager->journalOff;
+ if( newHdr && 0==(iDc&SQLITE_IOCAP_SAFE_APPEND) ){
+ pPager->nRec = 0;
+ rc = writeJournalHdr(pPager);
+ if( rc!=SQLITE_OK ) return rc;
+ }
+ }else{
+ pPager->journalHdr = pPager->journalOff;
+ }
+ }
+
+ /* Unless the pager is in noSync mode, the journal file was just
+ ** successfully synced. Either way, clear the PGHDR_NEED_SYNC flag on
+ ** all pages.
+ */
+ sqlite3PcacheClearSyncFlags(pPager->pPCache);
+ pPager->eState = PAGER_WRITER_DBMOD;
+ assert( assert_pager_state(pPager) );
+ return SQLITE_OK;
+}
+
+/*
+** The argument is the first in a linked list of dirty pages connected
+** by the PgHdr.pDirty pointer. This function writes each one of the
+** in-memory pages in the list to the database file. The argument may
+** be NULL, representing an empty list. In this case this function is
+** a no-op.
+**
+** The pager must hold at least a RESERVED lock when this function
+** is called. Before writing anything to the database file, this lock
+** is upgraded to an EXCLUSIVE lock. If the lock cannot be obtained,
+** SQLITE_BUSY is returned and no data is written to the database file.
+**
+** If the pager is a temp-file pager and the actual file-system file
+** is not yet open, it is created and opened before any data is
+** written out.
+**
+** Once the lock has been upgraded and, if necessary, the file opened,
+** the pages are written out to the database file in list order. Writing
+** a page is skipped if it meets either of the following criteria:
+**
+** * The page number is greater than Pager.dbSize, or
+** * The PGHDR_DONT_WRITE flag is set on the page.
+**
+** If writing out a page causes the database file to grow, Pager.dbFileSize
+** is updated accordingly. If page 1 is written out, then the value cached
+** in Pager.dbFileVers[] is updated to match the new value stored in
+** the database file.
+**
+** If everything is successful, SQLITE_OK is returned. If an IO error
+** occurs, an IO error code is returned. Or, if the EXCLUSIVE lock cannot
+** be obtained, SQLITE_BUSY is returned.
+*/
+static int pager_write_pagelist(Pager *pPager, PgHdr *pList){
+ int rc = SQLITE_OK; /* Return code */
+
+ /* This function is only called for rollback pagers in WRITER_DBMOD state. */
+ assert( !pagerUseWal(pPager) );
+ assert( pPager->tempFile || pPager->eState==PAGER_WRITER_DBMOD );
+ assert( pPager->eLock==EXCLUSIVE_LOCK );
+ assert( isOpen(pPager->fd) || pList->pDirty==0 );
+
+ /* If the file is a temp-file has not yet been opened, open it now. It
+ ** is not possible for rc to be other than SQLITE_OK if this branch
+ ** is taken, as pager_wait_on_lock() is a no-op for temp-files.
+ */
+ if( !isOpen(pPager->fd) ){
+ assert( pPager->tempFile && rc==SQLITE_OK );
+ rc = pagerOpentemp(pPager, pPager->fd, pPager->vfsFlags);
+ }
+
+ /* Before the first write, give the VFS a hint of what the final
+ ** file size will be.
+ */
+ assert( rc!=SQLITE_OK || isOpen(pPager->fd) );
+ if( rc==SQLITE_OK
+ && pPager->dbHintSize<pPager->dbSize
+ && (pList->pDirty || pList->pgno>pPager->dbHintSize)
+ ){
+ sqlite3_int64 szFile = pPager->pageSize * (sqlite3_int64)pPager->dbSize;
+ sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_SIZE_HINT, &szFile);
+ pPager->dbHintSize = pPager->dbSize;
+ }
+
+ while( rc==SQLITE_OK && pList ){
+ Pgno pgno = pList->pgno;
+
+ /* If there are dirty pages in the page cache with page numbers greater
+ ** than Pager.dbSize, this means sqlite3PagerTruncateImage() was called to
+ ** make the file smaller (presumably by auto-vacuum code). Do not write
+ ** any such pages to the file.
+ **
+ ** Also, do not write out any page that has the PGHDR_DONT_WRITE flag
+ ** set (set by sqlite3PagerDontWrite()).
+ */
+ if( pgno<=pPager->dbSize && 0==(pList->flags&PGHDR_DONT_WRITE) ){
+ i64 offset = (pgno-1)*(i64)pPager->pageSize; /* Offset to write */
+ char *pData; /* Data to write */
+
+ assert( (pList->flags&PGHDR_NEED_SYNC)==0 );
+ if( pList->pgno==1 ) pager_write_changecounter(pList);
+
+ pData = pList->pData;
+
+ /* Write out the page data. */
+ rc = sqlite3OsWrite(pPager->fd, pData, pPager->pageSize, offset);
+
+ /* If page 1 was just written, update Pager.dbFileVers to match
+ ** the value now stored in the database file. If writing this
+ ** page caused the database file to grow, update dbFileSize.
+ */
+ if( pgno==1 ){
+ memcpy(&pPager->dbFileVers, &pData[24], sizeof(pPager->dbFileVers));
+ }
+ if( pgno>pPager->dbFileSize ){
+ pPager->dbFileSize = pgno;
+ }
+ pPager->aStat[PAGER_STAT_WRITE]++;
+
+ /* Update any backup objects copying the contents of this pager. */
+ sqlite3BackupUpdate(pPager->pBackup, pgno, (u8*)pList->pData);
+
+ PAGERTRACE(("STORE %d page %d hash(%08x)\n",
+ PAGERID(pPager), pgno, pager_pagehash(pList)));
+ IOTRACE(("PGOUT %p %d\n", pPager, pgno));
+ PAGER_INCR(sqlite3_pager_writedb_count);
+ }else{
+ PAGERTRACE(("NOSTORE %d page %d\n", PAGERID(pPager), pgno));
+ }
+ pager_set_pagehash(pList);
+ pList = pList->pDirty;
+ }
+
+ return rc;
+}
+
+/*
+** Ensure that the sub-journal file is open. If it is already open, this
+** function is a no-op.
+**
+** SQLITE_OK is returned if everything goes according to plan. An
+** SQLITE_IOERR_XXX error code is returned if a call to sqlite3OsOpen()
+** fails.
+*/
+static int openSubJournal(Pager *pPager){
+ int rc = SQLITE_OK;
+ if( !isOpen(pPager->sjfd) ){
+ const int flags = SQLITE_OPEN_SUBJOURNAL | SQLITE_OPEN_READWRITE
+ | SQLITE_OPEN_CREATE | SQLITE_OPEN_EXCLUSIVE
+ | SQLITE_OPEN_DELETEONCLOSE;
+ int nStmtSpill = sqlite3Config.nStmtSpill;
+ if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY || pPager->subjInMemory ){
+ nStmtSpill = -1;
+ }
+ rc = sqlite3JournalOpen(pPager->pVfs, 0, pPager->sjfd, flags, nStmtSpill);
+ }
+ return rc;
+}
+
+/*
+** Append a record of the current state of page pPg to the sub-journal.
+**
+** If successful, set the bit corresponding to pPg->pgno in the bitvecs
+** for all open savepoints before returning.
+**
+** This function returns SQLITE_OK if everything is successful, an IO
+** error code if the attempt to write to the sub-journal fails, or
+** SQLITE_NOMEM if a malloc fails while setting a bit in a savepoint
+** bitvec.
+*/
+static int subjournalPage(PgHdr *pPg){
+ int rc = SQLITE_OK;
+ Pager *pPager = pPg->pPager;
+ if( pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
+
+ /* Open the sub-journal, if it has not already been opened */
+ assert( pPager->useJournal );
+ assert( isOpen(pPager->jfd) || pagerUseWal(pPager) );
+ assert( isOpen(pPager->sjfd) || pPager->nSubRec==0 );
+ assert( pagerUseWal(pPager)
+ || pageInJournal(pPager, pPg)
+ || pPg->pgno>pPager->dbOrigSize
+ );
+ rc = openSubJournal(pPager);
+
+ /* If the sub-journal was opened successfully (or was already open),
+ ** write the journal record into the file. */
+ if( rc==SQLITE_OK ){
+ void *pData = pPg->pData;
+ i64 offset = (i64)pPager->nSubRec*(4+pPager->pageSize);
+ char *pData2;
+ pData2 = pData;
+ PAGERTRACE(("STMT-JOURNAL %d page %d\n", PAGERID(pPager), pPg->pgno));
+ rc = write32bits(pPager->sjfd, offset, pPg->pgno);
+ if( rc==SQLITE_OK ){
+ rc = sqlite3OsWrite(pPager->sjfd, pData2, pPager->pageSize, offset+4);
+ }
+ }
+ }
+ if( rc==SQLITE_OK ){
+ pPager->nSubRec++;
+ assert( pPager->nSavepoint>0 );
+ rc = addToSavepointBitvecs(pPager, pPg->pgno);
+ }
+ return rc;
+}
+static int subjournalPageIfRequired(PgHdr *pPg){
+ if( subjRequiresPage(pPg) ){
+ return subjournalPage(pPg);
+ }else{
+ return SQLITE_OK;
+ }
+}
+
+/*
+** This function is called by the pcache layer when it has reached some
+** soft memory limit. The first argument is a pointer to a Pager object
+** (cast as a void*). The pager is always 'purgeable' (not an in-memory
+** database). The second argument is a reference to a page that is
+** currently dirty but has no outstanding references. The page
+** is always associated with the Pager object passed as the first
+** argument.
+**
+** The job of this function is to make pPg clean by writing its contents
+** out to the database file, if possible. This may involve syncing the
+** journal file.
+**
+** If successful, sqlite3PcacheMakeClean() is called on the page and
+** SQLITE_OK returned. If an IO error occurs while trying to make the
+** page clean, the IO error code is returned. If the page cannot be
+** made clean for some other reason, but no error occurs, then SQLITE_OK
+** is returned by sqlite3PcacheMakeClean() is not called.
+*/
+static int pagerStress(void *p, PgHdr *pPg){
+ Pager *pPager = (Pager *)p;
+ int rc = SQLITE_OK;
+
+ assert( pPg->pPager==pPager );
+ assert( pPg->flags&PGHDR_DIRTY );
+
+ /* The doNotSpill NOSYNC bit is set during times when doing a sync of
+ ** journal (and adding a new header) is not allowed. This occurs
+ ** during calls to sqlite3PagerWrite() while trying to journal multiple
+ ** pages belonging to the same sector.
+ **
+ ** The doNotSpill ROLLBACK and OFF bits inhibits all cache spilling
+ ** regardless of whether or not a sync is required. This is set during
+ ** a rollback or by user request, respectively.
+ **
+ ** Spilling is also prohibited when in an error state since that could
+ ** lead to database corruption. In the current implementation it
+ ** is impossible for sqlite3PcacheFetch() to be called with createFlag==3
+ ** while in the error state, hence it is impossible for this routine to
+ ** be called in the error state. Nevertheless, we include a NEVER()
+ ** test for the error state as a safeguard against future changes.
+ */
+ if( NEVER(pPager->errCode) ) return SQLITE_OK;
+ testcase( pPager->doNotSpill & SPILLFLAG_ROLLBACK );
+ testcase( pPager->doNotSpill & SPILLFLAG_OFF );
+ testcase( pPager->doNotSpill & SPILLFLAG_NOSYNC );
+ if( pPager->doNotSpill
+ && ((pPager->doNotSpill & (SPILLFLAG_ROLLBACK|SPILLFLAG_OFF))!=0
+ || (pPg->flags & PGHDR_NEED_SYNC)!=0)
+ ){
+ return SQLITE_OK;
+ }
+
+ pPager->aStat[PAGER_STAT_SPILL]++;
+ pPg->pDirty = 0;
+ if( pagerUseWal(pPager) ){
+ /* Write a single frame for this page to the log. */
+ rc = subjournalPageIfRequired(pPg);
+ if( rc==SQLITE_OK ){
+ rc = pagerWalFrames(pPager, pPg, 0, 0);
+ }
+ }else{
+
+#ifdef SQLITE_ENABLE_BATCH_ATOMIC_WRITE
+ if( pPager->tempFile==0 ){
+ rc = sqlite3JournalCreate(pPager->jfd);
+ if( rc!=SQLITE_OK ) return pager_error(pPager, rc);
+ }
+#endif
+
+ /* Sync the journal file if required. */
+ if( pPg->flags&PGHDR_NEED_SYNC
+ || pPager->eState==PAGER_WRITER_CACHEMOD
+ ){
+ rc = syncJournal(pPager, 1);
+ }
+
+ /* Write the contents of the page out to the database file. */
+ if( rc==SQLITE_OK ){
+ assert( (pPg->flags&PGHDR_NEED_SYNC)==0 );
+ rc = pager_write_pagelist(pPager, pPg);
+ }
+ }
+
+ /* Mark the page as clean. */
+ if( rc==SQLITE_OK ){
+ PAGERTRACE(("STRESS %d page %d\n", PAGERID(pPager), pPg->pgno));
+ sqlite3PcacheMakeClean(pPg);
+ }
+
+ return pager_error(pPager, rc);
+}
+
+/*
+** Flush all unreferenced dirty pages to disk.
+*/
+int sqlite3PagerFlush(Pager *pPager){
+ int rc = pPager->errCode;
+ if( !MEMDB ){
+ PgHdr *pList = sqlite3PcacheDirtyList(pPager->pPCache);
+ assert( assert_pager_state(pPager) );
+ while( rc==SQLITE_OK && pList ){
+ PgHdr *pNext = pList->pDirty;
+ if( pList->nRef==0 ){
+ rc = pagerStress((void*)pPager, pList);
+ }
+ pList = pNext;
+ }
+ }
+
+ return rc;
+}
+
+/*
+** Allocate and initialize a new Pager object and put a pointer to it
+** in *ppPager. The pager should eventually be freed by passing it
+** to sqlite3PagerClose().
+**
+** The zFilename argument is the path to the database file to open.
+** If zFilename is NULL then a randomly-named temporary file is created
+** and used as the file to be cached. Temporary files are be deleted
+** automatically when they are closed. If zFilename is ":memory:" then
+** all information is held in cache. It is never written to disk.
+** This can be used to implement an in-memory database.
+**
+** The nExtra parameter specifies the number of bytes of space allocated
+** along with each page reference. This space is available to the user
+** via the sqlite3PagerGetExtra() API. When a new page is allocated, the
+** first 8 bytes of this space are zeroed but the remainder is uninitialized.
+** (The extra space is used by btree as the MemPage object.)
+**
+** The flags argument is used to specify properties that affect the
+** operation of the pager. It should be passed some bitwise combination
+** of the PAGER_* flags.
+**
+** The vfsFlags parameter is a bitmask to pass to the flags parameter
+** of the xOpen() method of the supplied VFS when opening files.
+**
+** If the pager object is allocated and the specified file opened
+** successfully, SQLITE_OK is returned and *ppPager set to point to
+** the new pager object. If an error occurs, *ppPager is set to NULL
+** and error code returned. This function may return SQLITE_NOMEM
+** (sqlite3Malloc() is used to allocate memory), SQLITE_CANTOPEN or
+** various SQLITE_IO_XXX errors.
+*/
+int sqlite3PagerOpen(
+ sqlite3_vfs *pVfs, /* The virtual file system to use */
+ Pager **ppPager, /* OUT: Return the Pager structure here */
+ const char *zFilename, /* Name of the database file to open */
+ int nExtra, /* Extra bytes append to each in-memory page */
+ int flags, /* flags controlling this file */
+ int vfsFlags, /* flags passed through to sqlite3_vfs.xOpen() */
+ void (*xReinit)(DbPage*) /* Function to reinitialize pages */
+){
+ u8 *pPtr;
+ Pager *pPager = 0; /* Pager object to allocate and return */
+ int rc = SQLITE_OK; /* Return code */
+ int tempFile = 0; /* True for temp files (incl. in-memory files) */
+ int memDb = 0; /* True if this is an in-memory file */
+ int memJM = 0; /* Memory journal mode */
+ int readOnly = 0; /* True if this is a read-only file */
+ int journalFileSize; /* Bytes to allocate for each journal fd */
+ char *zPathname = 0; /* Full path to database file */
+ int nPathname = 0; /* Number of bytes in zPathname */
+ int useJournal = (flags & PAGER_OMIT_JOURNAL)==0; /* False to omit journal */
+ int pcacheSize = sqlite3PcacheSize(); /* Bytes to allocate for PCache */
+ u32 szPageDflt = SQLITE_DEFAULT_PAGE_SIZE; /* Default page size */
+ const char *zUri = 0; /* URI args to copy */
+ int nUriByte = 1; /* Number of bytes of URI args at *zUri */
+
+ /* Figure out how much space is required for each journal file-handle
+ ** (there are two of them, the main journal and the sub-journal). */
+ journalFileSize = ROUND8(sqlite3JournalSize(pVfs));
+
+ /* Set the output variable to NULL in case an error occurs. */
+ *ppPager = 0;
+
+#ifndef SQLITE_OMIT_MEMORYDB
+ if( flags & PAGER_MEMORY ){
+ memDb = 1;
+ if( zFilename && zFilename[0] ){
+ zPathname = sqlite3DbStrDup(0, zFilename);
+ if( zPathname==0 ) return SQLITE_NOMEM_BKPT;
+ nPathname = sqlite3Strlen30(zPathname);
+ zFilename = 0;
+ }
+ }
+#endif
+
+ /* Compute and store the full pathname in an allocated buffer pointed
+ ** to by zPathname, length nPathname. Or, if this is a temporary file,
+ ** leave both nPathname and zPathname set to 0.
+ */
+ if( zFilename && zFilename[0] ){
+ const char *z;
+ nPathname = pVfs->mxPathname+1;
+ zPathname = sqlite3DbMallocRaw(0, nPathname*2);
+ if( zPathname==0 ){
+ return SQLITE_NOMEM_BKPT;
+ }
+ zPathname[0] = 0; /* Make sure initialized even if FullPathname() fails */
+ rc = sqlite3OsFullPathname(pVfs, zFilename, nPathname, zPathname);
+ if( rc!=SQLITE_OK ){
+ if( rc==SQLITE_OK_SYMLINK ){
+ if( vfsFlags & SQLITE_OPEN_NOFOLLOW ){
+ rc = SQLITE_CANTOPEN_SYMLINK;
+ }else{
+ rc = SQLITE_OK;
+ }
+ }
+ }
+ nPathname = sqlite3Strlen30(zPathname);
+ z = zUri = &zFilename[sqlite3Strlen30(zFilename)+1];
+ while( *z ){
+ z += strlen(z)+1;
+ z += strlen(z)+1;
+ }
+ nUriByte = (int)(&z[1] - zUri);
+ assert( nUriByte>=1 );
+ if( rc==SQLITE_OK && nPathname+8>pVfs->mxPathname ){
+ /* This branch is taken when the journal path required by
+ ** the database being opened will be more than pVfs->mxPathname
+ ** bytes in length. This means the database cannot be opened,
+ ** as it will not be possible to open the journal file or even
+ ** check for a hot-journal before reading.
+ */
+ rc = SQLITE_CANTOPEN_BKPT;
+ }
+ if( rc!=SQLITE_OK ){
+ sqlite3DbFree(0, zPathname);
+ return rc;
+ }
+ }
+
+ /* Allocate memory for the Pager structure, PCache object, the
+ ** three file descriptors, the database file name and the journal
+ ** file name. The layout in memory is as follows:
+ **
+ ** Pager object (sizeof(Pager) bytes)
+ ** PCache object (sqlite3PcacheSize() bytes)
+ ** Database file handle (pVfs->szOsFile bytes)
+ ** Sub-journal file handle (journalFileSize bytes)
+ ** Main journal file handle (journalFileSize bytes)
+ ** Ptr back to the Pager (sizeof(Pager*) bytes)
+ ** \0\0\0\0 database prefix (4 bytes)
+ ** Database file name (nPathname+1 bytes)
+ ** URI query parameters (nUriByte bytes)
+ ** Journal filename (nPathname+8+1 bytes)
+ ** WAL filename (nPathname+4+1 bytes)
+ ** \0\0\0 terminator (3 bytes)
+ **
+ ** Some 3rd-party software, over which we have no control, depends on
+ ** the specific order of the filenames and the \0 separators between them
+ ** so that it can (for example) find the database filename given the WAL
+ ** filename without using the sqlite3_filename_database() API. This is a
+ ** misuse of SQLite and a bug in the 3rd-party software, but the 3rd-party
+ ** software is in widespread use, so we try to avoid changing the filename
+ ** order and formatting if possible. In particular, the details of the
+ ** filename format expected by 3rd-party software should be as follows:
+ **
+ ** - Main Database Path
+ ** - \0
+ ** - Multiple URI components consisting of:
+ ** - Key
+ ** - \0
+ ** - Value
+ ** - \0
+ ** - \0
+ ** - Journal Path
+ ** - \0
+ ** - WAL Path (zWALName)
+ ** - \0
+ **
+ ** The sqlite3_create_filename() interface and the databaseFilename() utility
+ ** that is used by sqlite3_filename_database() and kin also depend on the
+ ** specific formatting and order of the various filenames, so if the format
+ ** changes here, be sure to change it there as well.
+ */
+ assert( SQLITE_PTRSIZE==sizeof(Pager*) );
+ pPtr = (u8 *)sqlite3MallocZero(
+ ROUND8(sizeof(*pPager)) + /* Pager structure */
+ ROUND8(pcacheSize) + /* PCache object */
+ ROUND8(pVfs->szOsFile) + /* The main db file */
+ journalFileSize * 2 + /* The two journal files */
+ SQLITE_PTRSIZE + /* Space to hold a pointer */
+ 4 + /* Database prefix */
+ nPathname + 1 + /* database filename */
+ nUriByte + /* query parameters */
+ nPathname + 8 + 1 + /* Journal filename */
+#ifndef SQLITE_OMIT_WAL
+ nPathname + 4 + 1 + /* WAL filename */
+#endif
+ 3 /* Terminator */
+ );
+ assert( EIGHT_BYTE_ALIGNMENT(SQLITE_INT_TO_PTR(journalFileSize)) );
+ if( !pPtr ){
+ sqlite3DbFree(0, zPathname);
+ return SQLITE_NOMEM_BKPT;
+ }
+ pPager = (Pager*)pPtr; pPtr += ROUND8(sizeof(*pPager));
+ pPager->pPCache = (PCache*)pPtr; pPtr += ROUND8(pcacheSize);
+ pPager->fd = (sqlite3_file*)pPtr; pPtr += ROUND8(pVfs->szOsFile);
+ pPager->sjfd = (sqlite3_file*)pPtr; pPtr += journalFileSize;
+ pPager->jfd = (sqlite3_file*)pPtr; pPtr += journalFileSize;
+ assert( EIGHT_BYTE_ALIGNMENT(pPager->jfd) );
+ memcpy(pPtr, &pPager, SQLITE_PTRSIZE); pPtr += SQLITE_PTRSIZE;
+
+ /* Fill in the Pager.zFilename and pPager.zQueryParam fields */
+ pPtr += 4; /* Skip zero prefix */
+ pPager->zFilename = (char*)pPtr;
+ if( nPathname>0 ){
+ memcpy(pPtr, zPathname, nPathname); pPtr += nPathname + 1;
+ if( zUri ){
+ memcpy(pPtr, zUri, nUriByte); pPtr += nUriByte;
+ }else{
+ pPtr++;
+ }
+ }
+
+
+ /* Fill in Pager.zJournal */
+ if( nPathname>0 ){
+ pPager->zJournal = (char*)pPtr;
+ memcpy(pPtr, zPathname, nPathname); pPtr += nPathname;
+ memcpy(pPtr, "-journal",8); pPtr += 8 + 1;
+#ifdef SQLITE_ENABLE_8_3_NAMES
+ sqlite3FileSuffix3(zFilename,pPager->zJournal);
+ pPtr = (u8*)(pPager->zJournal + sqlite3Strlen30(pPager->zJournal)+1);
+#endif
+ }else{
+ pPager->zJournal = 0;
+ }
+
+#ifndef SQLITE_OMIT_WAL
+ /* Fill in Pager.zWal */
+ if( nPathname>0 ){
+ pPager->zWal = (char*)pPtr;
+ memcpy(pPtr, zPathname, nPathname); pPtr += nPathname;
+ memcpy(pPtr, "-wal", 4); pPtr += 4 + 1;
+#ifdef SQLITE_ENABLE_8_3_NAMES
+ sqlite3FileSuffix3(zFilename, pPager->zWal);
+ pPtr = (u8*)(pPager->zWal + sqlite3Strlen30(pPager->zWal)+1);
+#endif
+ }else{
+ pPager->zWal = 0;
+ }
+#endif
+ (void)pPtr; /* Suppress warning about unused pPtr value */
+
+ if( nPathname ) sqlite3DbFree(0, zPathname);
+ pPager->pVfs = pVfs;
+ pPager->vfsFlags = vfsFlags;
+
+ /* Open the pager file.
+ */
+ if( zFilename && zFilename[0] ){
+ int fout = 0; /* VFS flags returned by xOpen() */
+ rc = sqlite3OsOpen(pVfs, pPager->zFilename, pPager->fd, vfsFlags, &fout);
+ assert( !memDb );
+ pPager->memVfs = memJM = (fout&SQLITE_OPEN_MEMORY)!=0;
+ readOnly = (fout&SQLITE_OPEN_READONLY)!=0;
+
+ /* If the file was successfully opened for read/write access,
+ ** choose a default page size in case we have to create the
+ ** database file. The default page size is the maximum of:
+ **
+ ** + SQLITE_DEFAULT_PAGE_SIZE,
+ ** + The value returned by sqlite3OsSectorSize()
+ ** + The largest page size that can be written atomically.
+ */
+ if( rc==SQLITE_OK ){
+ int iDc = sqlite3OsDeviceCharacteristics(pPager->fd);
+ if( !readOnly ){
+ setSectorSize(pPager);
+ assert(SQLITE_DEFAULT_PAGE_SIZE<=SQLITE_MAX_DEFAULT_PAGE_SIZE);
+ if( szPageDflt<pPager->sectorSize ){
+ if( pPager->sectorSize>SQLITE_MAX_DEFAULT_PAGE_SIZE ){
+ szPageDflt = SQLITE_MAX_DEFAULT_PAGE_SIZE;
+ }else{
+ szPageDflt = (u32)pPager->sectorSize;
+ }
+ }
+#ifdef SQLITE_ENABLE_ATOMIC_WRITE
+ {
+ int ii;
+ assert(SQLITE_IOCAP_ATOMIC512==(512>>8));
+ assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8));
+ assert(SQLITE_MAX_DEFAULT_PAGE_SIZE<=65536);
+ for(ii=szPageDflt; ii<=SQLITE_MAX_DEFAULT_PAGE_SIZE; ii=ii*2){
+ if( iDc&(SQLITE_IOCAP_ATOMIC|(ii>>8)) ){
+ szPageDflt = ii;
+ }
+ }
+ }
+#endif
+ }
+ pPager->noLock = sqlite3_uri_boolean(pPager->zFilename, "nolock", 0);
+ if( (iDc & SQLITE_IOCAP_IMMUTABLE)!=0
+ || sqlite3_uri_boolean(pPager->zFilename, "immutable", 0) ){
+ vfsFlags |= SQLITE_OPEN_READONLY;
+ goto act_like_temp_file;
+ }
+ }
+ }else{
+ /* If a temporary file is requested, it is not opened immediately.
+ ** In this case we accept the default page size and delay actually
+ ** opening the file until the first call to OsWrite().
+ **
+ ** This branch is also run for an in-memory database. An in-memory
+ ** database is the same as a temp-file that is never written out to
+ ** disk and uses an in-memory rollback journal.
+ **
+ ** This branch also runs for files marked as immutable.
+ */
+act_like_temp_file:
+ tempFile = 1;
+ pPager->eState = PAGER_READER; /* Pretend we already have a lock */
+ pPager->eLock = EXCLUSIVE_LOCK; /* Pretend we are in EXCLUSIVE mode */
+ pPager->noLock = 1; /* Do no locking */
+ readOnly = (vfsFlags&SQLITE_OPEN_READONLY);
+ }
+
+ /* The following call to PagerSetPagesize() serves to set the value of
+ ** Pager.pageSize and to allocate the Pager.pTmpSpace buffer.
+ */
+ if( rc==SQLITE_OK ){
+ assert( pPager->memDb==0 );
+ rc = sqlite3PagerSetPagesize(pPager, &szPageDflt, -1);
+ testcase( rc!=SQLITE_OK );
+ }
+
+ /* Initialize the PCache object. */
+ if( rc==SQLITE_OK ){
+ nExtra = ROUND8(nExtra);
+ assert( nExtra>=8 && nExtra<1000 );
+ rc = sqlite3PcacheOpen(szPageDflt, nExtra, !memDb,
+ !memDb?pagerStress:0, (void *)pPager, pPager->pPCache);
+ }
+
+ /* If an error occurred above, free the Pager structure and close the file.
+ */
+ if( rc!=SQLITE_OK ){
+ sqlite3OsClose(pPager->fd);
+ sqlite3PageFree(pPager->pTmpSpace);
+ sqlite3_free(pPager);
+ return rc;
+ }
+
+ PAGERTRACE(("OPEN %d %s\n", FILEHANDLEID(pPager->fd), pPager->zFilename));
+ IOTRACE(("OPEN %p %s\n", pPager, pPager->zFilename))
+
+ pPager->useJournal = (u8)useJournal;
+ /* pPager->stmtOpen = 0; */
+ /* pPager->stmtInUse = 0; */
+ /* pPager->nRef = 0; */
+ /* pPager->stmtSize = 0; */
+ /* pPager->stmtJSize = 0; */
+ /* pPager->nPage = 0; */
+ pPager->mxPgno = SQLITE_MAX_PAGE_COUNT;
+ /* pPager->state = PAGER_UNLOCK; */
+ /* pPager->errMask = 0; */
+ pPager->tempFile = (u8)tempFile;
+ assert( tempFile==PAGER_LOCKINGMODE_NORMAL
+ || tempFile==PAGER_LOCKINGMODE_EXCLUSIVE );
+ assert( PAGER_LOCKINGMODE_EXCLUSIVE==1 );
+ pPager->exclusiveMode = (u8)tempFile;
+ pPager->changeCountDone = pPager->tempFile;
+ pPager->memDb = (u8)memDb;
+ pPager->readOnly = (u8)readOnly;
+ assert( useJournal || pPager->tempFile );
+ sqlite3PagerSetFlags(pPager, (SQLITE_DEFAULT_SYNCHRONOUS+1)|PAGER_CACHESPILL);
+ /* pPager->pFirst = 0; */
+ /* pPager->pFirstSynced = 0; */
+ /* pPager->pLast = 0; */
+ pPager->nExtra = (u16)nExtra;
+ pPager->journalSizeLimit = SQLITE_DEFAULT_JOURNAL_SIZE_LIMIT;
+ assert( isOpen(pPager->fd) || tempFile );
+ setSectorSize(pPager);
+ if( !useJournal ){
+ pPager->journalMode = PAGER_JOURNALMODE_OFF;
+ }else if( memDb || memJM ){
+ pPager->journalMode = PAGER_JOURNALMODE_MEMORY;
+ }
+ /* pPager->xBusyHandler = 0; */
+ /* pPager->pBusyHandlerArg = 0; */
+ pPager->xReiniter = xReinit;
+ setGetterMethod(pPager);
+ /* memset(pPager->aHash, 0, sizeof(pPager->aHash)); */
+ /* pPager->szMmap = SQLITE_DEFAULT_MMAP_SIZE // will be set by btree.c */
+
+ *ppPager = pPager;
+ return SQLITE_OK;
+}
+
+/*
+** Return the sqlite3_file for the main database given the name
+** of the corresponding WAL or Journal name as passed into
+** xOpen.
+*/
+sqlite3_file *sqlite3_database_file_object(const char *zName){
+ Pager *pPager;
+ const char *p;
+ while( zName[-1]!=0 || zName[-2]!=0 || zName[-3]!=0 || zName[-4]!=0 ){
+ zName--;
+ }
+ p = zName - 4 - sizeof(Pager*);
+ assert( EIGHT_BYTE_ALIGNMENT(p) );
+ pPager = *(Pager**)p;
+ return pPager->fd;
+}
+
+
+/*
+** This function is called after transitioning from PAGER_UNLOCK to
+** PAGER_SHARED state. It tests if there is a hot journal present in
+** the file-system for the given pager. A hot journal is one that
+** needs to be played back. According to this function, a hot-journal
+** file exists if the following criteria are met:
+**
+** * The journal file exists in the file system, and
+** * No process holds a RESERVED or greater lock on the database file, and
+** * The database file itself is greater than 0 bytes in size, and
+** * The first byte of the journal file exists and is not 0x00.
+**
+** If the current size of the database file is 0 but a journal file
+** exists, that is probably an old journal left over from a prior
+** database with the same name. In this case the journal file is
+** just deleted using OsDelete, *pExists is set to 0 and SQLITE_OK
+** is returned.
+**
+** This routine does not check if there is a super-journal filename
+** at the end of the file. If there is, and that super-journal file
+** does not exist, then the journal file is not really hot. In this
+** case this routine will return a false-positive. The pager_playback()
+** routine will discover that the journal file is not really hot and
+** will not roll it back.
+**
+** If a hot-journal file is found to exist, *pExists is set to 1 and
+** SQLITE_OK returned. If no hot-journal file is present, *pExists is
+** set to 0 and SQLITE_OK returned. If an IO error occurs while trying
+** to determine whether or not a hot-journal file exists, the IO error
+** code is returned and the value of *pExists is undefined.
+*/
+static int hasHotJournal(Pager *pPager, int *pExists){
+ sqlite3_vfs * const pVfs = pPager->pVfs;
+ int rc = SQLITE_OK; /* Return code */
+ int exists = 1; /* True if a journal file is present */
+ int jrnlOpen = !!isOpen(pPager->jfd);
+
+ assert( pPager->useJournal );
+ assert( isOpen(pPager->fd) );
+ assert( pPager->eState==PAGER_OPEN );
+
+ assert( jrnlOpen==0 || ( sqlite3OsDeviceCharacteristics(pPager->jfd) &
+ SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN
+ ));
+
+ *pExists = 0;
+ if( !jrnlOpen ){
+ rc = sqlite3OsAccess(pVfs, pPager->zJournal, SQLITE_ACCESS_EXISTS, &exists);
+ }
+ if( rc==SQLITE_OK && exists ){
+ int locked = 0; /* True if some process holds a RESERVED lock */
+
+ /* Race condition here: Another process might have been holding the
+ ** the RESERVED lock and have a journal open at the sqlite3OsAccess()
+ ** call above, but then delete the journal and drop the lock before
+ ** we get to the following sqlite3OsCheckReservedLock() call. If that
+ ** is the case, this routine might think there is a hot journal when
+ ** in fact there is none. This results in a false-positive which will
+ ** be dealt with by the playback routine. Ticket #3883.
+ */
+ rc = sqlite3OsCheckReservedLock(pPager->fd, &locked);
+ if( rc==SQLITE_OK && !locked ){
+ Pgno nPage; /* Number of pages in database file */
+
+ assert( pPager->tempFile==0 );
+ rc = pagerPagecount(pPager, &nPage);
+ if( rc==SQLITE_OK ){
+ /* If the database is zero pages in size, that means that either (1) the
+ ** journal is a remnant from a prior database with the same name where
+ ** the database file but not the journal was deleted, or (2) the initial
+ ** transaction that populates a new database is being rolled back.
+ ** In either case, the journal file can be deleted. However, take care
+ ** not to delete the journal file if it is already open due to
+ ** journal_mode=PERSIST.
+ */
+ if( nPage==0 && !jrnlOpen ){
+ sqlite3BeginBenignMalloc();
+ if( pagerLockDb(pPager, RESERVED_LOCK)==SQLITE_OK ){
+ sqlite3OsDelete(pVfs, pPager->zJournal, 0);
+ if( !pPager->exclusiveMode ) pagerUnlockDb(pPager, SHARED_LOCK);
+ }
+ sqlite3EndBenignMalloc();
+ }else{
+ /* The journal file exists and no other connection has a reserved
+ ** or greater lock on the database file. Now check that there is
+ ** at least one non-zero bytes at the start of the journal file.
+ ** If there is, then we consider this journal to be hot. If not,
+ ** it can be ignored.
+ */
+ if( !jrnlOpen ){
+ int f = SQLITE_OPEN_READONLY|SQLITE_OPEN_MAIN_JOURNAL;
+ rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, f, &f);
+ }
+ if( rc==SQLITE_OK ){
+ u8 first = 0;
+ rc = sqlite3OsRead(pPager->jfd, (void *)&first, 1, 0);
+ if( rc==SQLITE_IOERR_SHORT_READ ){
+ rc = SQLITE_OK;
+ }
+ if( !jrnlOpen ){
+ sqlite3OsClose(pPager->jfd);
+ }
+ *pExists = (first!=0);
+ }else if( rc==SQLITE_CANTOPEN ){
+ /* If we cannot open the rollback journal file in order to see if
+ ** it has a zero header, that might be due to an I/O error, or
+ ** it might be due to the race condition described above and in
+ ** ticket #3883. Either way, assume that the journal is hot.
+ ** This might be a false positive. But if it is, then the
+ ** automatic journal playback and recovery mechanism will deal
+ ** with it under an EXCLUSIVE lock where we do not need to
+ ** worry so much with race conditions.
+ */
+ *pExists = 1;
+ rc = SQLITE_OK;
+ }
+ }
+ }
+ }
+ }
+
+ return rc;
+}
+
+/*
+** This function is called to obtain a shared lock on the database file.
+** It is illegal to call sqlite3PagerGet() until after this function
+** has been successfully called. If a shared-lock is already held when
+** this function is called, it is a no-op.
+**
+** The following operations are also performed by this function.
+**
+** 1) If the pager is currently in PAGER_OPEN state (no lock held
+** on the database file), then an attempt is made to obtain a
+** SHARED lock on the database file. Immediately after obtaining
+** the SHARED lock, the file-system is checked for a hot-journal,
+** which is played back if present. Following any hot-journal
+** rollback, the contents of the cache are validated by checking
+** the 'change-counter' field of the database file header and
+** discarded if they are found to be invalid.
+**
+** 2) If the pager is running in exclusive-mode, and there are currently
+** no outstanding references to any pages, and is in the error state,
+** then an attempt is made to clear the error state by discarding
+** the contents of the page cache and rolling back any open journal
+** file.
+**
+** If everything is successful, SQLITE_OK is returned. If an IO error
+** occurs while locking the database, checking for a hot-journal file or
+** rolling back a journal file, the IO error code is returned.
+*/
+int sqlite3PagerSharedLock(Pager *pPager){
+ int rc = SQLITE_OK; /* Return code */
+
+ /* This routine is only called from b-tree and only when there are no
+ ** outstanding pages. This implies that the pager state should either
+ ** be OPEN or READER. READER is only possible if the pager is or was in
+ ** exclusive access mode. */
+ assert( sqlite3PcacheRefCount(pPager->pPCache)==0 );
+ assert( assert_pager_state(pPager) );
+ assert( pPager->eState==PAGER_OPEN || pPager->eState==PAGER_READER );
+ assert( pPager->errCode==SQLITE_OK );
+
+ if( !pagerUseWal(pPager) && pPager->eState==PAGER_OPEN ){
+ int bHotJournal = 1; /* True if there exists a hot journal-file */
+
+ assert( !MEMDB );
+ assert( pPager->tempFile==0 || pPager->eLock==EXCLUSIVE_LOCK );
+
+ rc = pager_wait_on_lock(pPager, SHARED_LOCK);
+ if( rc!=SQLITE_OK ){
+ assert( pPager->eLock==NO_LOCK || pPager->eLock==UNKNOWN_LOCK );
+ goto failed;
+ }
+
+ /* If a journal file exists, and there is no RESERVED lock on the
+ ** database file, then it either needs to be played back or deleted.
+ */
+ if( pPager->eLock<=SHARED_LOCK ){
+ rc = hasHotJournal(pPager, &bHotJournal);
+ }
+ if( rc!=SQLITE_OK ){
+ goto failed;
+ }
+ if( bHotJournal ){
+ if( pPager->readOnly ){
+ rc = SQLITE_READONLY_ROLLBACK;
+ goto failed;
+ }
+
+ /* Get an EXCLUSIVE lock on the database file. At this point it is
+ ** important that a RESERVED lock is not obtained on the way to the
+ ** EXCLUSIVE lock. If it were, another process might open the
+ ** database file, detect the RESERVED lock, and conclude that the
+ ** database is safe to read while this process is still rolling the
+ ** hot-journal back.
+ **
+ ** Because the intermediate RESERVED lock is not requested, any
+ ** other process attempting to access the database file will get to
+ ** this point in the code and fail to obtain its own EXCLUSIVE lock
+ ** on the database file.
+ **
+ ** Unless the pager is in locking_mode=exclusive mode, the lock is
+ ** downgraded to SHARED_LOCK before this function returns.
+ */
+ rc = pagerLockDb(pPager, EXCLUSIVE_LOCK);
+ if( rc!=SQLITE_OK ){
+ goto failed;
+ }
+
+ /* If it is not already open and the file exists on disk, open the
+ ** journal for read/write access. Write access is required because
+ ** in exclusive-access mode the file descriptor will be kept open
+ ** and possibly used for a transaction later on. Also, write-access
+ ** is usually required to finalize the journal in journal_mode=persist
+ ** mode (and also for journal_mode=truncate on some systems).
+ **
+ ** If the journal does not exist, it usually means that some
+ ** other connection managed to get in and roll it back before
+ ** this connection obtained the exclusive lock above. Or, it
+ ** may mean that the pager was in the error-state when this
+ ** function was called and the journal file does not exist.
+ */
+ if( !isOpen(pPager->jfd) && pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
+ sqlite3_vfs * const pVfs = pPager->pVfs;
+ int bExists; /* True if journal file exists */
+ rc = sqlite3OsAccess(
+ pVfs, pPager->zJournal, SQLITE_ACCESS_EXISTS, &bExists);
+ if( rc==SQLITE_OK && bExists ){
+ int fout = 0;
+ int f = SQLITE_OPEN_READWRITE|SQLITE_OPEN_MAIN_JOURNAL;
+ assert( !pPager->tempFile );
+ rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, f, &fout);
+ assert( rc!=SQLITE_OK || isOpen(pPager->jfd) );
+ if( rc==SQLITE_OK && fout&SQLITE_OPEN_READONLY ){
+ rc = SQLITE_CANTOPEN_BKPT;
+ sqlite3OsClose(pPager->jfd);
+ }
+ }
+ }
+
+ /* Playback and delete the journal. Drop the database write
+ ** lock and reacquire the read lock. Purge the cache before
+ ** playing back the hot-journal so that we don't end up with
+ ** an inconsistent cache. Sync the hot journal before playing
+ ** it back since the process that crashed and left the hot journal
+ ** probably did not sync it and we are required to always sync
+ ** the journal before playing it back.
+ */
+ if( isOpen(pPager->jfd) ){
+ assert( rc==SQLITE_OK );
+ rc = pagerSyncHotJournal(pPager);
+ if( rc==SQLITE_OK ){
+ rc = pager_playback(pPager, !pPager->tempFile);
+ pPager->eState = PAGER_OPEN;
+ }
+ }else if( !pPager->exclusiveMode ){
+ pagerUnlockDb(pPager, SHARED_LOCK);
+ }
+
+ if( rc!=SQLITE_OK ){
+ /* This branch is taken if an error occurs while trying to open
+ ** or roll back a hot-journal while holding an EXCLUSIVE lock. The
+ ** pager_unlock() routine will be called before returning to unlock
+ ** the file. If the unlock attempt fails, then Pager.eLock must be
+ ** set to UNKNOWN_LOCK (see the comment above the #define for
+ ** UNKNOWN_LOCK above for an explanation).
+ **
+ ** In order to get pager_unlock() to do this, set Pager.eState to
+ ** PAGER_ERROR now. This is not actually counted as a transition
+ ** to ERROR state in the state diagram at the top of this file,
+ ** since we know that the same call to pager_unlock() will very
+ ** shortly transition the pager object to the OPEN state. Calling
+ ** assert_pager_state() would fail now, as it should not be possible
+ ** to be in ERROR state when there are zero outstanding page
+ ** references.
+ */
+ pager_error(pPager, rc);
+ goto failed;
+ }
+
+ assert( pPager->eState==PAGER_OPEN );
+ assert( (pPager->eLock==SHARED_LOCK)
+ || (pPager->exclusiveMode && pPager->eLock>SHARED_LOCK)
+ );
+ }
+
+ if( !pPager->tempFile && pPager->hasHeldSharedLock ){
+ /* The shared-lock has just been acquired then check to
+ ** see if the database has been modified. If the database has changed,
+ ** flush the cache. The hasHeldSharedLock flag prevents this from
+ ** occurring on the very first access to a file, in order to save a
+ ** single unnecessary sqlite3OsRead() call at the start-up.
+ **
+ ** Database changes are detected by looking at 15 bytes beginning
+ ** at offset 24 into the file. The first 4 of these 16 bytes are
+ ** a 32-bit counter that is incremented with each change. The
+ ** other bytes change randomly with each file change when
+ ** a codec is in use.
+ **
+ ** There is a vanishingly small chance that a change will not be
+ ** detected. The chance of an undetected change is so small that
+ ** it can be neglected.
+ */
+ char dbFileVers[sizeof(pPager->dbFileVers)];
+
+ IOTRACE(("CKVERS %p %d\n", pPager, sizeof(dbFileVers)));
+ rc = sqlite3OsRead(pPager->fd, &dbFileVers, sizeof(dbFileVers), 24);
+ if( rc!=SQLITE_OK ){
+ if( rc!=SQLITE_IOERR_SHORT_READ ){
+ goto failed;
+ }
+ memset(dbFileVers, 0, sizeof(dbFileVers));
+ }
+
+ if( memcmp(pPager->dbFileVers, dbFileVers, sizeof(dbFileVers))!=0 ){
+ pager_reset(pPager);
+
+ /* Unmap the database file. It is possible that external processes
+ ** may have truncated the database file and then extended it back
+ ** to its original size while this process was not holding a lock.
+ ** In this case there may exist a Pager.pMap mapping that appears
+ ** to be the right size but is not actually valid. Avoid this
+ ** possibility by unmapping the db here. */
+ if( USEFETCH(pPager) ){
+ sqlite3OsUnfetch(pPager->fd, 0, 0);
+ }
+ }
+ }
+
+ /* If there is a WAL file in the file-system, open this database in WAL
+ ** mode. Otherwise, the following function call is a no-op.
+ */
+ rc = pagerOpenWalIfPresent(pPager);
+#ifndef SQLITE_OMIT_WAL
+ assert( pPager->pWal==0 || rc==SQLITE_OK );
+#endif
+ }
+
+ if( pagerUseWal(pPager) ){
+ assert( rc==SQLITE_OK );
+ rc = pagerBeginReadTransaction(pPager);
+ }
+
+ if( pPager->tempFile==0 && pPager->eState==PAGER_OPEN && rc==SQLITE_OK ){
+ rc = pagerPagecount(pPager, &pPager->dbSize);
+ }
+
+ failed:
+ if( rc!=SQLITE_OK ){
+ assert( !MEMDB );
+ pager_unlock(pPager);
+ assert( pPager->eState==PAGER_OPEN );
+ }else{
+ pPager->eState = PAGER_READER;
+ pPager->hasHeldSharedLock = 1;
+ }
+ return rc;
+}
+
+/*
+** If the reference count has reached zero, rollback any active
+** transaction and unlock the pager.
+**
+** Except, in locking_mode=EXCLUSIVE when there is nothing to in
+** the rollback journal, the unlock is not performed and there is
+** nothing to rollback, so this routine is a no-op.
+*/
+static void pagerUnlockIfUnused(Pager *pPager){
+ if( sqlite3PcacheRefCount(pPager->pPCache)==0 ){
+ assert( pPager->nMmapOut==0 ); /* because page1 is never memory mapped */
+ pagerUnlockAndRollback(pPager);
+ }
+}
+
+/*
+** The page getter methods each try to acquire a reference to a
+** page with page number pgno. If the requested reference is
+** successfully obtained, it is copied to *ppPage and SQLITE_OK returned.
+**
+** There are different implementations of the getter method depending
+** on the current state of the pager.
+**
+** getPageNormal() -- The normal getter
+** getPageError() -- Used if the pager is in an error state
+** getPageMmap() -- Used if memory-mapped I/O is enabled
+**
+** If the requested page is already in the cache, it is returned.
+** Otherwise, a new page object is allocated and populated with data
+** read from the database file. In some cases, the pcache module may
+** choose not to allocate a new page object and may reuse an existing
+** object with no outstanding references.
+**
+** The extra data appended to a page is always initialized to zeros the
+** first time a page is loaded into memory. If the page requested is
+** already in the cache when this function is called, then the extra
+** data is left as it was when the page object was last used.
+**
+** If the database image is smaller than the requested page or if
+** the flags parameter contains the PAGER_GET_NOCONTENT bit and the
+** requested page is not already stored in the cache, then no
+** actual disk read occurs. In this case the memory image of the
+** page is initialized to all zeros.
+**
+** If PAGER_GET_NOCONTENT is true, it means that we do not care about
+** the contents of the page. This occurs in two scenarios:
+**
+** a) When reading a free-list leaf page from the database, and
+**
+** b) When a savepoint is being rolled back and we need to load
+** a new page into the cache to be filled with the data read
+** from the savepoint journal.
+**
+** If PAGER_GET_NOCONTENT is true, then the data returned is zeroed instead
+** of being read from the database. Additionally, the bits corresponding
+** to pgno in Pager.pInJournal (bitvec of pages already written to the
+** journal file) and the PagerSavepoint.pInSavepoint bitvecs of any open
+** savepoints are set. This means if the page is made writable at any
+** point in the future, using a call to sqlite3PagerWrite(), its contents
+** will not be journaled. This saves IO.
+**
+** The acquisition might fail for several reasons. In all cases,
+** an appropriate error code is returned and *ppPage is set to NULL.
+**
+** See also sqlite3PagerLookup(). Both this routine and Lookup() attempt
+** to find a page in the in-memory cache first. If the page is not already
+** in memory, this routine goes to disk to read it in whereas Lookup()
+** just returns 0. This routine acquires a read-lock the first time it
+** has to go to disk, and could also playback an old journal if necessary.
+** Since Lookup() never goes to disk, it never has to deal with locks
+** or journal files.
+*/
+static int getPageNormal(
+ Pager *pPager, /* The pager open on the database file */
+ Pgno pgno, /* Page number to fetch */
+ DbPage **ppPage, /* Write a pointer to the page here */
+ int flags /* PAGER_GET_XXX flags */
+){
+ int rc = SQLITE_OK;
+ PgHdr *pPg;
+ u8 noContent; /* True if PAGER_GET_NOCONTENT is set */
+ sqlite3_pcache_page *pBase;
+
+ assert( pPager->errCode==SQLITE_OK );
+ assert( pPager->eState>=PAGER_READER );
+ assert( assert_pager_state(pPager) );
+ assert( pPager->hasHeldSharedLock==1 );
+
+ if( pgno==0 ) return SQLITE_CORRUPT_BKPT;
+ pBase = sqlite3PcacheFetch(pPager->pPCache, pgno, 3);
+ if( pBase==0 ){
+ pPg = 0;
+ rc = sqlite3PcacheFetchStress(pPager->pPCache, pgno, &pBase);
+ if( rc!=SQLITE_OK ) goto pager_acquire_err;
+ if( pBase==0 ){
+ rc = SQLITE_NOMEM_BKPT;
+ goto pager_acquire_err;
+ }
+ }
+ pPg = *ppPage = sqlite3PcacheFetchFinish(pPager->pPCache, pgno, pBase);
+ assert( pPg==(*ppPage) );
+ assert( pPg->pgno==pgno );
+ assert( pPg->pPager==pPager || pPg->pPager==0 );
+
+ noContent = (flags & PAGER_GET_NOCONTENT)!=0;
+ if( pPg->pPager && !noContent ){
+ /* In this case the pcache already contains an initialized copy of
+ ** the page. Return without further ado. */
+ assert( pgno!=PAGER_SJ_PGNO(pPager) );
+ pPager->aStat[PAGER_STAT_HIT]++;
+ return SQLITE_OK;
+
+ }else{
+ /* The pager cache has created a new page. Its content needs to
+ ** be initialized. But first some error checks:
+ **
+ ** (*) obsolete. Was: maximum page number is 2^31
+ ** (2) Never try to fetch the locking page
+ */
+ if( pgno==PAGER_SJ_PGNO(pPager) ){
+ rc = SQLITE_CORRUPT_BKPT;
+ goto pager_acquire_err;
+ }
+
+ pPg->pPager = pPager;
+
+ assert( !isOpen(pPager->fd) || !MEMDB );
+ if( !isOpen(pPager->fd) || pPager->dbSize<pgno || noContent ){
+ if( pgno>pPager->mxPgno ){
+ rc = SQLITE_FULL;
+ if( pgno<=pPager->dbSize ){
+ sqlite3PcacheRelease(pPg);
+ pPg = 0;
+ }
+ goto pager_acquire_err;
+ }
+ if( noContent ){
+ /* Failure to set the bits in the InJournal bit-vectors is benign.
+ ** It merely means that we might do some extra work to journal a
+ ** page that does not need to be journaled. Nevertheless, be sure
+ ** to test the case where a malloc error occurs while trying to set
+ ** a bit in a bit vector.
+ */
+ sqlite3BeginBenignMalloc();
+ if( pgno<=pPager->dbOrigSize ){
+ TESTONLY( rc = ) sqlite3BitvecSet(pPager->pInJournal, pgno);
+ testcase( rc==SQLITE_NOMEM );
+ }
+ TESTONLY( rc = ) addToSavepointBitvecs(pPager, pgno);
+ testcase( rc==SQLITE_NOMEM );
+ sqlite3EndBenignMalloc();
+ }
+ memset(pPg->pData, 0, pPager->pageSize);
+ IOTRACE(("ZERO %p %d\n", pPager, pgno));
+ }else{
+ assert( pPg->pPager==pPager );
+ pPager->aStat[PAGER_STAT_MISS]++;
+ rc = readDbPage(pPg);
+ if( rc!=SQLITE_OK ){
+ goto pager_acquire_err;
+ }
+ }
+ pager_set_pagehash(pPg);
+ }
+ return SQLITE_OK;
+
+pager_acquire_err:
+ assert( rc!=SQLITE_OK );
+ if( pPg ){
+ sqlite3PcacheDrop(pPg);
+ }
+ pagerUnlockIfUnused(pPager);
+ *ppPage = 0;
+ return rc;
+}
+
+#if SQLITE_MAX_MMAP_SIZE>0
+/* The page getter for when memory-mapped I/O is enabled */
+static int getPageMMap(
+ Pager *pPager, /* The pager open on the database file */
+ Pgno pgno, /* Page number to fetch */
+ DbPage **ppPage, /* Write a pointer to the page here */
+ int flags /* PAGER_GET_XXX flags */
+){
+ int rc = SQLITE_OK;
+ PgHdr *pPg = 0;
+ u32 iFrame = 0; /* Frame to read from WAL file */
+
+ /* It is acceptable to use a read-only (mmap) page for any page except
+ ** page 1 if there is no write-transaction open or the ACQUIRE_READONLY
+ ** flag was specified by the caller. And so long as the db is not a
+ ** temporary or in-memory database. */
+ const int bMmapOk = (pgno>1
+ && (pPager->eState==PAGER_READER || (flags & PAGER_GET_READONLY))
+ );
+
+ assert( USEFETCH(pPager) );
+
+ /* Optimization note: Adding the "pgno<=1" term before "pgno==0" here
+ ** allows the compiler optimizer to reuse the results of the "pgno>1"
+ ** test in the previous statement, and avoid testing pgno==0 in the
+ ** common case where pgno is large. */
+ if( pgno<=1 && pgno==0 ){
+ return SQLITE_CORRUPT_BKPT;
+ }
+ assert( pPager->eState>=PAGER_READER );
+ assert( assert_pager_state(pPager) );
+ assert( pPager->hasHeldSharedLock==1 );
+ assert( pPager->errCode==SQLITE_OK );
+
+ if( bMmapOk && pagerUseWal(pPager) ){
+ rc = sqlite3WalFindFrame(pPager->pWal, pgno, &iFrame);
+ if( rc!=SQLITE_OK ){
+ *ppPage = 0;
+ return rc;
+ }
+ }
+ if( bMmapOk && iFrame==0 ){
+ void *pData = 0;
+ rc = sqlite3OsFetch(pPager->fd,
+ (i64)(pgno-1) * pPager->pageSize, pPager->pageSize, &pData
+ );
+ if( rc==SQLITE_OK && pData ){
+ if( pPager->eState>PAGER_READER || pPager->tempFile ){
+ pPg = sqlite3PagerLookup(pPager, pgno);
+ }
+ if( pPg==0 ){
+ rc = pagerAcquireMapPage(pPager, pgno, pData, &pPg);
+ }else{
+ sqlite3OsUnfetch(pPager->fd, (i64)(pgno-1)*pPager->pageSize, pData);
+ }
+ if( pPg ){
+ assert( rc==SQLITE_OK );
+ *ppPage = pPg;
+ return SQLITE_OK;
+ }
+ }
+ if( rc!=SQLITE_OK ){
+ *ppPage = 0;
+ return rc;
+ }
+ }
+ return getPageNormal(pPager, pgno, ppPage, flags);
+}
+#endif /* SQLITE_MAX_MMAP_SIZE>0 */
+
+/* The page getter method for when the pager is an error state */
+static int getPageError(
+ Pager *pPager, /* The pager open on the database file */
+ Pgno pgno, /* Page number to fetch */
+ DbPage **ppPage, /* Write a pointer to the page here */
+ int flags /* PAGER_GET_XXX flags */
+){
+ UNUSED_PARAMETER(pgno);
+ UNUSED_PARAMETER(flags);
+ assert( pPager->errCode!=SQLITE_OK );
+ *ppPage = 0;
+ return pPager->errCode;
+}
+
+
+/* Dispatch all page fetch requests to the appropriate getter method.
+*/
+int sqlite3PagerGet(
+ Pager *pPager, /* The pager open on the database file */
+ Pgno pgno, /* Page number to fetch */
+ DbPage **ppPage, /* Write a pointer to the page here */
+ int flags /* PAGER_GET_XXX flags */
+){
+#if 0 /* Trace page fetch by setting to 1 */
+ int rc;
+ printf("PAGE %u\n", pgno);
+ fflush(stdout);
+ rc = pPager->xGet(pPager, pgno, ppPage, flags);
+ if( rc ){
+ printf("PAGE %u failed with 0x%02x\n", pgno, rc);
+ fflush(stdout);
+ }
+ return rc;
+#else
+ /* Normal, high-speed version of sqlite3PagerGet() */
+ return pPager->xGet(pPager, pgno, ppPage, flags);
+#endif
+}
+
+/*
+** Acquire a page if it is already in the in-memory cache. Do
+** not read the page from disk. Return a pointer to the page,
+** or 0 if the page is not in cache.
+**
+** See also sqlite3PagerGet(). The difference between this routine
+** and sqlite3PagerGet() is that _get() will go to the disk and read
+** in the page if the page is not already in cache. This routine
+** returns NULL if the page is not in cache or if a disk I/O error
+** has ever happened.
+*/
+DbPage *sqlite3PagerLookup(Pager *pPager, Pgno pgno){
+ sqlite3_pcache_page *pPage;
+ assert( pPager!=0 );
+ assert( pgno!=0 );
+ assert( pPager->pPCache!=0 );
+ pPage = sqlite3PcacheFetch(pPager->pPCache, pgno, 0);
+ assert( pPage==0 || pPager->hasHeldSharedLock );
+ if( pPage==0 ) return 0;
+ return sqlite3PcacheFetchFinish(pPager->pPCache, pgno, pPage);
+}
+
+/*
+** Release a page reference.
+**
+** The sqlite3PagerUnref() and sqlite3PagerUnrefNotNull() may only be used
+** if we know that the page being released is not the last reference to page1.
+** The btree layer always holds page1 open until the end, so these first
+** two routines can be used to release any page other than BtShared.pPage1.
+** The assert() at tag-20230419-2 proves that this constraint is always
+** honored.
+**
+** Use sqlite3PagerUnrefPageOne() to release page1. This latter routine
+** checks the total number of outstanding pages and if the number of
+** pages reaches zero it drops the database lock.
+*/
+void sqlite3PagerUnrefNotNull(DbPage *pPg){
+ TESTONLY( Pager *pPager = pPg->pPager; )
+ assert( pPg!=0 );
+ if( pPg->flags & PGHDR_MMAP ){
+ assert( pPg->pgno!=1 ); /* Page1 is never memory mapped */
+ pagerReleaseMapPage(pPg);
+ }else{
+ sqlite3PcacheRelease(pPg);
+ }
+ /* Do not use this routine to release the last reference to page1 */
+ assert( sqlite3PcacheRefCount(pPager->pPCache)>0 ); /* tag-20230419-2 */
+}
+void sqlite3PagerUnref(DbPage *pPg){
+ if( pPg ) sqlite3PagerUnrefNotNull(pPg);
+}
+void sqlite3PagerUnrefPageOne(DbPage *pPg){
+ Pager *pPager;
+ assert( pPg!=0 );
+ assert( pPg->pgno==1 );
+ assert( (pPg->flags & PGHDR_MMAP)==0 ); /* Page1 is never memory mapped */
+ pPager = pPg->pPager;
+ sqlite3PcacheRelease(pPg);
+ pagerUnlockIfUnused(pPager);
+}
+
+/*
+** This function is called at the start of every write transaction.
+** There must already be a RESERVED or EXCLUSIVE lock on the database
+** file when this routine is called.
+**
+** Open the journal file for pager pPager and write a journal header
+** to the start of it. If there are active savepoints, open the sub-journal
+** as well. This function is only used when the journal file is being
+** opened to write a rollback log for a transaction. It is not used
+** when opening a hot journal file to roll it back.
+**
+** If the journal file is already open (as it may be in exclusive mode),
+** then this function just writes a journal header to the start of the
+** already open file.
+**
+** Whether or not the journal file is opened by this function, the
+** Pager.pInJournal bitvec structure is allocated.
+**
+** Return SQLITE_OK if everything is successful. Otherwise, return
+** SQLITE_NOMEM if the attempt to allocate Pager.pInJournal fails, or
+** an IO error code if opening or writing the journal file fails.
+*/
+static int pager_open_journal(Pager *pPager){
+ int rc = SQLITE_OK; /* Return code */
+ sqlite3_vfs * const pVfs = pPager->pVfs; /* Local cache of vfs pointer */
+
+ assert( pPager->eState==PAGER_WRITER_LOCKED );
+ assert( assert_pager_state(pPager) );
+ assert( pPager->pInJournal==0 );
+
+ /* If already in the error state, this function is a no-op. But on
+ ** the other hand, this routine is never called if we are already in
+ ** an error state. */
+ if( NEVER(pPager->errCode) ) return pPager->errCode;
+
+ if( !pagerUseWal(pPager) && pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
+ pPager->pInJournal = sqlite3BitvecCreate(pPager->dbSize);
+ if( pPager->pInJournal==0 ){
+ return SQLITE_NOMEM_BKPT;
+ }
+
+ /* Open the journal file if it is not already open. */
+ if( !isOpen(pPager->jfd) ){
+ if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ){
+ sqlite3MemJournalOpen(pPager->jfd);
+ }else{
+ int flags = SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE;
+ int nSpill;
+
+ if( pPager->tempFile ){
+ flags |= (SQLITE_OPEN_DELETEONCLOSE|SQLITE_OPEN_TEMP_JOURNAL);
+ flags |= SQLITE_OPEN_EXCLUSIVE;
+ nSpill = sqlite3Config.nStmtSpill;
+ }else{
+ flags |= SQLITE_OPEN_MAIN_JOURNAL;
+ nSpill = jrnlBufferSize(pPager);
+ }
+
+ /* Verify that the database still has the same name as it did when
+ ** it was originally opened. */
+ rc = databaseIsUnmoved(pPager);
+ if( rc==SQLITE_OK ){
+ rc = sqlite3JournalOpen (
+ pVfs, pPager->zJournal, pPager->jfd, flags, nSpill
+ );
+ }
+ }
+ assert( rc!=SQLITE_OK || isOpen(pPager->jfd) );
+ }
+
+
+ /* Write the first journal header to the journal file and open
+ ** the sub-journal if necessary.
+ */
+ if( rc==SQLITE_OK ){
+ /* TODO: Check if all of these are really required. */
+ pPager->nRec = 0;
+ pPager->journalOff = 0;
+ pPager->setSuper = 0;
+ pPager->journalHdr = 0;
+ rc = writeJournalHdr(pPager);
+ }
+ }
+
+ if( rc!=SQLITE_OK ){
+ sqlite3BitvecDestroy(pPager->pInJournal);
+ pPager->pInJournal = 0;
+ pPager->journalOff = 0;
+ }else{
+ assert( pPager->eState==PAGER_WRITER_LOCKED );
+ pPager->eState = PAGER_WRITER_CACHEMOD;
+ }
+
+ return rc;
+}
+
+/*
+** Begin a write-transaction on the specified pager object. If a
+** write-transaction has already been opened, this function is a no-op.
+**
+** If the exFlag argument is false, then acquire at least a RESERVED
+** lock on the database file. If exFlag is true, then acquire at least
+** an EXCLUSIVE lock. If such a lock is already held, no locking
+** functions need be called.
+**
+** If the subjInMemory argument is non-zero, then any sub-journal opened
+** within this transaction will be opened as an in-memory file. This
+** has no effect if the sub-journal is already opened (as it may be when
+** running in exclusive mode) or if the transaction does not require a
+** sub-journal. If the subjInMemory argument is zero, then any required
+** sub-journal is implemented in-memory if pPager is an in-memory database,
+** or using a temporary file otherwise.
+*/
+int sqlite3PagerBegin(Pager *pPager, int exFlag, int subjInMemory){
+ int rc = SQLITE_OK;
+
+ if( pPager->errCode ) return pPager->errCode;
+ assert( pPager->eState>=PAGER_READER && pPager->eState<PAGER_ERROR );
+ pPager->subjInMemory = (u8)subjInMemory;
+
+ if( pPager->eState==PAGER_READER ){
+ assert( pPager->pInJournal==0 );
+
+ if( pagerUseWal(pPager) ){
+ /* If the pager is configured to use locking_mode=exclusive, and an
+ ** exclusive lock on the database is not already held, obtain it now.
+ */
+ if( pPager->exclusiveMode && sqlite3WalExclusiveMode(pPager->pWal, -1) ){
+ rc = pagerLockDb(pPager, EXCLUSIVE_LOCK);
+ if( rc!=SQLITE_OK ){
+ return rc;
+ }
+ (void)sqlite3WalExclusiveMode(pPager->pWal, 1);
+ }
+
+ /* Grab the write lock on the log file. If successful, upgrade to
+ ** PAGER_RESERVED state. Otherwise, return an error code to the caller.
+ ** The busy-handler is not invoked if another connection already
+ ** holds the write-lock. If possible, the upper layer will call it.
+ */
+ rc = sqlite3WalBeginWriteTransaction(pPager->pWal);
+ }else{
+ /* Obtain a RESERVED lock on the database file. If the exFlag parameter
+ ** is true, then immediately upgrade this to an EXCLUSIVE lock. The
+ ** busy-handler callback can be used when upgrading to the EXCLUSIVE
+ ** lock, but not when obtaining the RESERVED lock.
+ */
+ rc = pagerLockDb(pPager, RESERVED_LOCK);
+ if( rc==SQLITE_OK && exFlag ){
+ rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
+ }
+ }
+
+ if( rc==SQLITE_OK ){
+ /* Change to WRITER_LOCKED state.
+ **
+ ** WAL mode sets Pager.eState to PAGER_WRITER_LOCKED or CACHEMOD
+ ** when it has an open transaction, but never to DBMOD or FINISHED.
+ ** This is because in those states the code to roll back savepoint
+ ** transactions may copy data from the sub-journal into the database
+ ** file as well as into the page cache. Which would be incorrect in
+ ** WAL mode.
+ */
+ pPager->eState = PAGER_WRITER_LOCKED;
+ pPager->dbHintSize = pPager->dbSize;
+ pPager->dbFileSize = pPager->dbSize;
+ pPager->dbOrigSize = pPager->dbSize;
+ pPager->journalOff = 0;
+ }
+
+ assert( rc==SQLITE_OK || pPager->eState==PAGER_READER );
+ assert( rc!=SQLITE_OK || pPager->eState==PAGER_WRITER_LOCKED );
+ assert( assert_pager_state(pPager) );
+ }
+
+ PAGERTRACE(("TRANSACTION %d\n", PAGERID(pPager)));
+ return rc;
+}
+
+/*
+** Write page pPg onto the end of the rollback journal.
+*/
+static SQLITE_NOINLINE int pagerAddPageToRollbackJournal(PgHdr *pPg){
+ Pager *pPager = pPg->pPager;
+ int rc;
+ u32 cksum;
+ char *pData2;
+ i64 iOff = pPager->journalOff;
+
+ /* We should never write to the journal file the page that
+ ** contains the database locks. The following assert verifies
+ ** that we do not. */
+ assert( pPg->pgno!=PAGER_SJ_PGNO(pPager) );
+
+ assert( pPager->journalHdr<=pPager->journalOff );
+ pData2 = pPg->pData;
+ cksum = pager_cksum(pPager, (u8*)pData2);
+
+ /* Even if an IO or diskfull error occurs while journalling the
+ ** page in the block above, set the need-sync flag for the page.
+ ** Otherwise, when the transaction is rolled back, the logic in
+ ** playback_one_page() will think that the page needs to be restored
+ ** in the database file. And if an IO error occurs while doing so,
+ ** then corruption may follow.
+ */
+ pPg->flags |= PGHDR_NEED_SYNC;
+
+ rc = write32bits(pPager->jfd, iOff, pPg->pgno);
+ if( rc!=SQLITE_OK ) return rc;
+ rc = sqlite3OsWrite(pPager->jfd, pData2, pPager->pageSize, iOff+4);
+ if( rc!=SQLITE_OK ) return rc;
+ rc = write32bits(pPager->jfd, iOff+pPager->pageSize+4, cksum);
+ if( rc!=SQLITE_OK ) return rc;
+
+ IOTRACE(("JOUT %p %d %lld %d\n", pPager, pPg->pgno,
+ pPager->journalOff, pPager->pageSize));
+ PAGER_INCR(sqlite3_pager_writej_count);
+ PAGERTRACE(("JOURNAL %d page %d needSync=%d hash(%08x)\n",
+ PAGERID(pPager), pPg->pgno,
+ ((pPg->flags&PGHDR_NEED_SYNC)?1:0), pager_pagehash(pPg)));
+
+ pPager->journalOff += 8 + pPager->pageSize;
+ pPager->nRec++;
+ assert( pPager->pInJournal!=0 );
+ rc = sqlite3BitvecSet(pPager->pInJournal, pPg->pgno);
+ testcase( rc==SQLITE_NOMEM );
+ assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
+ rc |= addToSavepointBitvecs(pPager, pPg->pgno);
+ assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
+ return rc;
+}
+
+/*
+** Mark a single data page as writeable. The page is written into the
+** main journal or sub-journal as required. If the page is written into
+** one of the journals, the corresponding bit is set in the
+** Pager.pInJournal bitvec and the PagerSavepoint.pInSavepoint bitvecs
+** of any open savepoints as appropriate.
+*/
+static int pager_write(PgHdr *pPg){
+ Pager *pPager = pPg->pPager;
+ int rc = SQLITE_OK;
+
+ /* This routine is not called unless a write-transaction has already
+ ** been started. The journal file may or may not be open at this point.
+ ** It is never called in the ERROR state.
+ */
+ assert( pPager->eState==PAGER_WRITER_LOCKED
+ || pPager->eState==PAGER_WRITER_CACHEMOD
+ || pPager->eState==PAGER_WRITER_DBMOD
+ );
+ assert( assert_pager_state(pPager) );
+ assert( pPager->errCode==0 );
+ assert( pPager->readOnly==0 );
+ CHECK_PAGE(pPg);
+
+ /* The journal file needs to be opened. Higher level routines have already
+ ** obtained the necessary locks to begin the write-transaction, but the
+ ** rollback journal might not yet be open. Open it now if this is the case.
+ **
+ ** This is done before calling sqlite3PcacheMakeDirty() on the page.
+ ** Otherwise, if it were done after calling sqlite3PcacheMakeDirty(), then
+ ** an error might occur and the pager would end up in WRITER_LOCKED state
+ ** with pages marked as dirty in the cache.
+ */
+ if( pPager->eState==PAGER_WRITER_LOCKED ){
+ rc = pager_open_journal(pPager);
+ if( rc!=SQLITE_OK ) return rc;
+ }
+ assert( pPager->eState>=PAGER_WRITER_CACHEMOD );
+ assert( assert_pager_state(pPager) );
+
+ /* Mark the page that is about to be modified as dirty. */
+ sqlite3PcacheMakeDirty(pPg);
+
+ /* If a rollback journal is in use, them make sure the page that is about
+ ** to change is in the rollback journal, or if the page is a new page off
+ ** then end of the file, make sure it is marked as PGHDR_NEED_SYNC.
+ */
+ assert( (pPager->pInJournal!=0) == isOpen(pPager->jfd) );
+ if( pPager->pInJournal!=0
+ && sqlite3BitvecTestNotNull(pPager->pInJournal, pPg->pgno)==0
+ ){
+ assert( pagerUseWal(pPager)==0 );
+ if( pPg->pgno<=pPager->dbOrigSize ){
+ rc = pagerAddPageToRollbackJournal(pPg);
+ if( rc!=SQLITE_OK ){
+ return rc;
+ }
+ }else{
+ if( pPager->eState!=PAGER_WRITER_DBMOD ){
+ pPg->flags |= PGHDR_NEED_SYNC;
+ }
+ PAGERTRACE(("APPEND %d page %d needSync=%d\n",
+ PAGERID(pPager), pPg->pgno,
+ ((pPg->flags&PGHDR_NEED_SYNC)?1:0)));
+ }
+ }
+
+ /* The PGHDR_DIRTY bit is set above when the page was added to the dirty-list
+ ** and before writing the page into the rollback journal. Wait until now,
+ ** after the page has been successfully journalled, before setting the
+ ** PGHDR_WRITEABLE bit that indicates that the page can be safely modified.
+ */
+ pPg->flags |= PGHDR_WRITEABLE;
+
+ /* If the statement journal is open and the page is not in it,
+ ** then write the page into the statement journal.
+ */
+ if( pPager->nSavepoint>0 ){
+ rc = subjournalPageIfRequired(pPg);
+ }
+
+ /* Update the database size and return. */
+ if( pPager->dbSize<pPg->pgno ){
+ pPager->dbSize = pPg->pgno;
+ }
+ return rc;
+}
+
+/*
+** This is a variant of sqlite3PagerWrite() that runs when the sector size
+** is larger than the page size. SQLite makes the (reasonable) assumption that
+** all bytes of a sector are written together by hardware. Hence, all bytes of
+** a sector need to be journalled in case of a power loss in the middle of
+** a write.
+**
+** Usually, the sector size is less than or equal to the page size, in which
+** case pages can be individually written. This routine only runs in the
+** exceptional case where the page size is smaller than the sector size.
+*/
+static SQLITE_NOINLINE int pagerWriteLargeSector(PgHdr *pPg){
+ int rc = SQLITE_OK; /* Return code */
+ Pgno nPageCount; /* Total number of pages in database file */
+ Pgno pg1; /* First page of the sector pPg is located on. */
+ int nPage = 0; /* Number of pages starting at pg1 to journal */
+ int ii; /* Loop counter */
+ int needSync = 0; /* True if any page has PGHDR_NEED_SYNC */
+ Pager *pPager = pPg->pPager; /* The pager that owns pPg */
+ Pgno nPagePerSector = (pPager->sectorSize/pPager->pageSize);
+
+ /* Set the doNotSpill NOSYNC bit to 1. This is because we cannot allow
+ ** a journal header to be written between the pages journaled by
+ ** this function.
+ */
+ assert( !MEMDB );
+ assert( (pPager->doNotSpill & SPILLFLAG_NOSYNC)==0 );
+ pPager->doNotSpill |= SPILLFLAG_NOSYNC;
+
+ /* This trick assumes that both the page-size and sector-size are
+ ** an integer power of 2. It sets variable pg1 to the identifier
+ ** of the first page of the sector pPg is located on.
+ */
+ pg1 = ((pPg->pgno-1) & ~(nPagePerSector-1)) + 1;
+
+ nPageCount = pPager->dbSize;
+ if( pPg->pgno>nPageCount ){
+ nPage = (pPg->pgno - pg1)+1;
+ }else if( (pg1+nPagePerSector-1)>nPageCount ){
+ nPage = nPageCount+1-pg1;
+ }else{
+ nPage = nPagePerSector;
+ }
+ assert(nPage>0);
+ assert(pg1<=pPg->pgno);
+ assert((pg1+nPage)>pPg->pgno);
+
+ for(ii=0; ii<nPage && rc==SQLITE_OK; ii++){
+ Pgno pg = pg1+ii;
+ PgHdr *pPage;
+ if( pg==pPg->pgno || !sqlite3BitvecTest(pPager->pInJournal, pg) ){
+ if( pg!=PAGER_SJ_PGNO(pPager) ){
+ rc = sqlite3PagerGet(pPager, pg, &pPage, 0);
+ if( rc==SQLITE_OK ){
+ rc = pager_write(pPage);
+ if( pPage->flags&PGHDR_NEED_SYNC ){
+ needSync = 1;
+ }
+ sqlite3PagerUnrefNotNull(pPage);
+ }
+ }
+ }else if( (pPage = sqlite3PagerLookup(pPager, pg))!=0 ){
+ if( pPage->flags&PGHDR_NEED_SYNC ){
+ needSync = 1;
+ }
+ sqlite3PagerUnrefNotNull(pPage);
+ }
+ }
+
+ /* If the PGHDR_NEED_SYNC flag is set for any of the nPage pages
+ ** starting at pg1, then it needs to be set for all of them. Because
+ ** writing to any of these nPage pages may damage the others, the
+ ** journal file must contain sync()ed copies of all of them
+ ** before any of them can be written out to the database file.
+ */
+ if( rc==SQLITE_OK && needSync ){
+ assert( !MEMDB );
+ for(ii=0; ii<nPage; ii++){
+ PgHdr *pPage = sqlite3PagerLookup(pPager, pg1+ii);
+ if( pPage ){
+ pPage->flags |= PGHDR_NEED_SYNC;
+ sqlite3PagerUnrefNotNull(pPage);
+ }
+ }
+ }
+
+ assert( (pPager->doNotSpill & SPILLFLAG_NOSYNC)!=0 );
+ pPager->doNotSpill &= ~SPILLFLAG_NOSYNC;
+ return rc;
+}
+
+/*
+** Mark a data page as writeable. This routine must be called before
+** making changes to a page. The caller must check the return value
+** of this function and be careful not to change any page data unless
+** this routine returns SQLITE_OK.
+**
+** The difference between this function and pager_write() is that this
+** function also deals with the special case where 2 or more pages
+** fit on a single disk sector. In this case all co-resident pages
+** must have been written to the journal file before returning.
+**
+** If an error occurs, SQLITE_NOMEM or an IO error code is returned
+** as appropriate. Otherwise, SQLITE_OK.
+*/
+int sqlite3PagerWrite(PgHdr *pPg){
+ Pager *pPager = pPg->pPager;
+ assert( (pPg->flags & PGHDR_MMAP)==0 );
+ assert( pPager->eState>=PAGER_WRITER_LOCKED );
+ assert( assert_pager_state(pPager) );
+ if( (pPg->flags & PGHDR_WRITEABLE)!=0 && pPager->dbSize>=pPg->pgno ){
+ if( pPager->nSavepoint ) return subjournalPageIfRequired(pPg);
+ return SQLITE_OK;
+ }else if( pPager->errCode ){
+ return pPager->errCode;
+ }else if( pPager->sectorSize > (u32)pPager->pageSize ){
+ assert( pPager->tempFile==0 );
+ return pagerWriteLargeSector(pPg);
+ }else{
+ return pager_write(pPg);
+ }
+}
+
+/*
+** Return TRUE if the page given in the argument was previously passed
+** to sqlite3PagerWrite(). In other words, return TRUE if it is ok
+** to change the content of the page.
+*/
+#ifndef NDEBUG
+int sqlite3PagerIswriteable(DbPage *pPg){
+ return pPg->flags & PGHDR_WRITEABLE;
+}
+#endif
+
+/*
+** A call to this routine tells the pager that it is not necessary to
+** write the information on page pPg back to the disk, even though
+** that page might be marked as dirty. This happens, for example, when
+** the page has been added as a leaf of the freelist and so its
+** content no longer matters.
+**
+** The overlying software layer calls this routine when all of the data
+** on the given page is unused. The pager marks the page as clean so
+** that it does not get written to disk.
+**
+** Tests show that this optimization can quadruple the speed of large
+** DELETE operations.
+**
+** This optimization cannot be used with a temp-file, as the page may
+** have been dirty at the start of the transaction. In that case, if
+** memory pressure forces page pPg out of the cache, the data does need
+** to be written out to disk so that it may be read back in if the
+** current transaction is rolled back.
+*/
+void sqlite3PagerDontWrite(PgHdr *pPg){
+ Pager *pPager = pPg->pPager;
+ if( !pPager->tempFile && (pPg->flags&PGHDR_DIRTY) && pPager->nSavepoint==0 ){
+ PAGERTRACE(("DONT_WRITE page %d of %d\n", pPg->pgno, PAGERID(pPager)));
+ IOTRACE(("CLEAN %p %d\n", pPager, pPg->pgno))
+ pPg->flags |= PGHDR_DONT_WRITE;
+ pPg->flags &= ~PGHDR_WRITEABLE;
+ testcase( pPg->flags & PGHDR_NEED_SYNC );
+ pager_set_pagehash(pPg);
+ }
+}
+
+/*
+** This routine is called to increment the value of the database file
+** change-counter, stored as a 4-byte big-endian integer starting at
+** byte offset 24 of the pager file. The secondary change counter at
+** 92 is also updated, as is the SQLite version number at offset 96.
+**
+** But this only happens if the pPager->changeCountDone flag is false.
+** To avoid excess churning of page 1, the update only happens once.
+** See also the pager_write_changecounter() routine that does an
+** unconditional update of the change counters.
+**
+** If the isDirectMode flag is zero, then this is done by calling
+** sqlite3PagerWrite() on page 1, then modifying the contents of the
+** page data. In this case the file will be updated when the current
+** transaction is committed.
+**
+** The isDirectMode flag may only be non-zero if the library was compiled
+** with the SQLITE_ENABLE_ATOMIC_WRITE macro defined. In this case,
+** if isDirect is non-zero, then the database file is updated directly
+** by writing an updated version of page 1 using a call to the
+** sqlite3OsWrite() function.
+*/
+static int pager_incr_changecounter(Pager *pPager, int isDirectMode){
+ int rc = SQLITE_OK;
+
+ assert( pPager->eState==PAGER_WRITER_CACHEMOD
+ || pPager->eState==PAGER_WRITER_DBMOD
+ );
+ assert( assert_pager_state(pPager) );
+
+ /* Declare and initialize constant integer 'isDirect'. If the
+ ** atomic-write optimization is enabled in this build, then isDirect
+ ** is initialized to the value passed as the isDirectMode parameter
+ ** to this function. Otherwise, it is always set to zero.
+ **
+ ** The idea is that if the atomic-write optimization is not
+ ** enabled at compile time, the compiler can omit the tests of
+ ** 'isDirect' below, as well as the block enclosed in the
+ ** "if( isDirect )" condition.
+ */
+#ifndef SQLITE_ENABLE_ATOMIC_WRITE
+# define DIRECT_MODE 0
+ assert( isDirectMode==0 );
+ UNUSED_PARAMETER(isDirectMode);
+#else
+# define DIRECT_MODE isDirectMode
+#endif
+
+ if( !pPager->changeCountDone && pPager->dbSize>0 ){
+ PgHdr *pPgHdr; /* Reference to page 1 */
+
+ assert( !pPager->tempFile && isOpen(pPager->fd) );
+
+ /* Open page 1 of the file for writing. */
+ rc = sqlite3PagerGet(pPager, 1, &pPgHdr, 0);
+ assert( pPgHdr==0 || rc==SQLITE_OK );
+
+ /* If page one was fetched successfully, and this function is not
+ ** operating in direct-mode, make page 1 writable. When not in
+ ** direct mode, page 1 is always held in cache and hence the PagerGet()
+ ** above is always successful - hence the ALWAYS on rc==SQLITE_OK.
+ */
+ if( !DIRECT_MODE && ALWAYS(rc==SQLITE_OK) ){
+ rc = sqlite3PagerWrite(pPgHdr);
+ }
+
+ if( rc==SQLITE_OK ){
+ /* Actually do the update of the change counter */
+ pager_write_changecounter(pPgHdr);
+
+ /* If running in direct mode, write the contents of page 1 to the file. */
+ if( DIRECT_MODE ){
+ const void *zBuf;
+ assert( pPager->dbFileSize>0 );
+ zBuf = pPgHdr->pData;
+ if( rc==SQLITE_OK ){
+ rc = sqlite3OsWrite(pPager->fd, zBuf, pPager->pageSize, 0);
+ pPager->aStat[PAGER_STAT_WRITE]++;
+ }
+ if( rc==SQLITE_OK ){
+ /* Update the pager's copy of the change-counter. Otherwise, the
+ ** next time a read transaction is opened the cache will be
+ ** flushed (as the change-counter values will not match). */
+ const void *pCopy = (const void *)&((const char *)zBuf)[24];
+ memcpy(&pPager->dbFileVers, pCopy, sizeof(pPager->dbFileVers));
+ pPager->changeCountDone = 1;
+ }
+ }else{
+ pPager->changeCountDone = 1;
+ }
+ }
+
+ /* Release the page reference. */
+ sqlite3PagerUnref(pPgHdr);
+ }
+ return rc;
+}
+
+/*
+** Sync the database file to disk. This is a no-op for in-memory databases
+** or pages with the Pager.noSync flag set.
+**
+** If successful, or if called on a pager for which it is a no-op, this
+** function returns SQLITE_OK. Otherwise, an IO error code is returned.
+*/
+int sqlite3PagerSync(Pager *pPager, const char *zSuper){
+ int rc = SQLITE_OK;
+ void *pArg = (void*)zSuper;
+ rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_SYNC, pArg);
+ if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK;
+ if( rc==SQLITE_OK && !pPager->noSync ){
+ assert( !MEMDB );
+ rc = sqlite3OsSync(pPager->fd, pPager->syncFlags);
+ }
+ return rc;
+}
+
+/*
+** This function may only be called while a write-transaction is active in
+** rollback. If the connection is in WAL mode, this call is a no-op.
+** Otherwise, if the connection does not already have an EXCLUSIVE lock on
+** the database file, an attempt is made to obtain one.
+**
+** If the EXCLUSIVE lock is already held or the attempt to obtain it is
+** successful, or the connection is in WAL mode, SQLITE_OK is returned.
+** Otherwise, either SQLITE_BUSY or an SQLITE_IOERR_XXX error code is
+** returned.
+*/
+int sqlite3PagerExclusiveLock(Pager *pPager){
+ int rc = pPager->errCode;
+ assert( assert_pager_state(pPager) );
+ if( rc==SQLITE_OK ){
+ assert( pPager->eState==PAGER_WRITER_CACHEMOD
+ || pPager->eState==PAGER_WRITER_DBMOD
+ || pPager->eState==PAGER_WRITER_LOCKED
+ );
+ assert( assert_pager_state(pPager) );
+ if( 0==pagerUseWal(pPager) ){
+ rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
+ }
+ }
+ return rc;
+}
+
+/*
+** Sync the database file for the pager pPager. zSuper points to the name
+** of a super-journal file that should be written into the individual
+** journal file. zSuper may be NULL, which is interpreted as no
+** super-journal (a single database transaction).
+**
+** This routine ensures that:
+**
+** * The database file change-counter is updated,
+** * the journal is synced (unless the atomic-write optimization is used),
+** * all dirty pages are written to the database file,
+** * the database file is truncated (if required), and
+** * the database file synced.
+**
+** The only thing that remains to commit the transaction is to finalize
+** (delete, truncate or zero the first part of) the journal file (or
+** delete the super-journal file if specified).
+**
+** Note that if zSuper==NULL, this does not overwrite a previous value
+** passed to an sqlite3PagerCommitPhaseOne() call.
+**
+** If the final parameter - noSync - is true, then the database file itself
+** is not synced. The caller must call sqlite3PagerSync() directly to
+** sync the database file before calling CommitPhaseTwo() to delete the
+** journal file in this case.
+*/
+int sqlite3PagerCommitPhaseOne(
+ Pager *pPager, /* Pager object */
+ const char *zSuper, /* If not NULL, the super-journal name */
+ int noSync /* True to omit the xSync on the db file */
+){
+ int rc = SQLITE_OK; /* Return code */
+
+ assert( pPager->eState==PAGER_WRITER_LOCKED
+ || pPager->eState==PAGER_WRITER_CACHEMOD
+ || pPager->eState==PAGER_WRITER_DBMOD
+ || pPager->eState==PAGER_ERROR
+ );
+ assert( assert_pager_state(pPager) );
+
+ /* If a prior error occurred, report that error again. */
+ if( NEVER(pPager->errCode) ) return pPager->errCode;
+
+ /* Provide the ability to easily simulate an I/O error during testing */
+ if( sqlite3FaultSim(400) ) return SQLITE_IOERR;
+
+ PAGERTRACE(("DATABASE SYNC: File=%s zSuper=%s nSize=%d\n",
+ pPager->zFilename, zSuper, pPager->dbSize));
+
+ /* If no database changes have been made, return early. */
+ if( pPager->eState<PAGER_WRITER_CACHEMOD ) return SQLITE_OK;
+
+ assert( MEMDB==0 || pPager->tempFile );
+ assert( isOpen(pPager->fd) || pPager->tempFile );
+ if( 0==pagerFlushOnCommit(pPager, 1) ){
+ /* If this is an in-memory db, or no pages have been written to, or this
+ ** function has already been called, it is mostly a no-op. However, any
+ ** backup in progress needs to be restarted. */
+ sqlite3BackupRestart(pPager->pBackup);
+ }else{
+ PgHdr *pList;
+ if( pagerUseWal(pPager) ){
+ PgHdr *pPageOne = 0;
+ pList = sqlite3PcacheDirtyList(pPager->pPCache);
+ if( pList==0 ){
+ /* Must have at least one page for the WAL commit flag.
+ ** Ticket [2d1a5c67dfc2363e44f29d9bbd57f] 2011-05-18 */
+ rc = sqlite3PagerGet(pPager, 1, &pPageOne, 0);
+ pList = pPageOne;
+ pList->pDirty = 0;
+ }
+ assert( rc==SQLITE_OK );
+ if( ALWAYS(pList) ){
+ rc = pagerWalFrames(pPager, pList, pPager->dbSize, 1);
+ }
+ sqlite3PagerUnref(pPageOne);
+ if( rc==SQLITE_OK ){
+ sqlite3PcacheCleanAll(pPager->pPCache);
+ }
+ }else{
+ /* The bBatch boolean is true if the batch-atomic-write commit method
+ ** should be used. No rollback journal is created if batch-atomic-write
+ ** is enabled.
+ */
+#ifdef SQLITE_ENABLE_BATCH_ATOMIC_WRITE
+ sqlite3_file *fd = pPager->fd;
+ int bBatch = zSuper==0 /* An SQLITE_IOCAP_BATCH_ATOMIC commit */
+ && (sqlite3OsDeviceCharacteristics(fd) & SQLITE_IOCAP_BATCH_ATOMIC)
+ && !pPager->noSync
+ && sqlite3JournalIsInMemory(pPager->jfd);
+#else
+# define bBatch 0
+#endif
+
+#ifdef SQLITE_ENABLE_ATOMIC_WRITE
+ /* The following block updates the change-counter. Exactly how it
+ ** does this depends on whether or not the atomic-update optimization
+ ** was enabled at compile time, and if this transaction meets the
+ ** runtime criteria to use the operation:
+ **
+ ** * The file-system supports the atomic-write property for
+ ** blocks of size page-size, and
+ ** * This commit is not part of a multi-file transaction, and
+ ** * Exactly one page has been modified and store in the journal file.
+ **
+ ** If the optimization was not enabled at compile time, then the
+ ** pager_incr_changecounter() function is called to update the change
+ ** counter in 'indirect-mode'. If the optimization is compiled in but
+ ** is not applicable to this transaction, call sqlite3JournalCreate()
+ ** to make sure the journal file has actually been created, then call
+ ** pager_incr_changecounter() to update the change-counter in indirect
+ ** mode.
+ **
+ ** Otherwise, if the optimization is both enabled and applicable,
+ ** then call pager_incr_changecounter() to update the change-counter
+ ** in 'direct' mode. In this case the journal file will never be
+ ** created for this transaction.
+ */
+ if( bBatch==0 ){
+ PgHdr *pPg;
+ assert( isOpen(pPager->jfd)
+ || pPager->journalMode==PAGER_JOURNALMODE_OFF
+ || pPager->journalMode==PAGER_JOURNALMODE_WAL
+ );
+ if( !zSuper && isOpen(pPager->jfd)
+ && pPager->journalOff==jrnlBufferSize(pPager)
+ && pPager->dbSize>=pPager->dbOrigSize
+ && (!(pPg = sqlite3PcacheDirtyList(pPager->pPCache)) || 0==pPg->pDirty)
+ ){
+ /* Update the db file change counter via the direct-write method. The
+ ** following call will modify the in-memory representation of page 1
+ ** to include the updated change counter and then write page 1
+ ** directly to the database file. Because of the atomic-write
+ ** property of the host file-system, this is safe.
+ */
+ rc = pager_incr_changecounter(pPager, 1);
+ }else{
+ rc = sqlite3JournalCreate(pPager->jfd);
+ if( rc==SQLITE_OK ){
+ rc = pager_incr_changecounter(pPager, 0);
+ }
+ }
+ }
+#else /* SQLITE_ENABLE_ATOMIC_WRITE */
+#ifdef SQLITE_ENABLE_BATCH_ATOMIC_WRITE
+ if( zSuper ){
+ rc = sqlite3JournalCreate(pPager->jfd);
+ if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+ assert( bBatch==0 );
+ }
+#endif
+ rc = pager_incr_changecounter(pPager, 0);
+#endif /* !SQLITE_ENABLE_ATOMIC_WRITE */
+ if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+
+ /* Write the super-journal name into the journal file. If a
+ ** super-journal file name has already been written to the journal file,
+ ** or if zSuper is NULL (no super-journal), then this call is a no-op.
+ */
+ rc = writeSuperJournal(pPager, zSuper);
+ if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+
+ /* Sync the journal file and write all dirty pages to the database.
+ ** If the atomic-update optimization is being used, this sync will not
+ ** create the journal file or perform any real IO.
+ **
+ ** Because the change-counter page was just modified, unless the
+ ** atomic-update optimization is used it is almost certain that the
+ ** journal requires a sync here. However, in locking_mode=exclusive
+ ** on a system under memory pressure it is just possible that this is
+ ** not the case. In this case it is likely enough that the redundant
+ ** xSync() call will be changed to a no-op by the OS anyhow.
+ */
+ rc = syncJournal(pPager, 0);
+ if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+
+ pList = sqlite3PcacheDirtyList(pPager->pPCache);
+#ifdef SQLITE_ENABLE_BATCH_ATOMIC_WRITE
+ if( bBatch ){
+ rc = sqlite3OsFileControl(fd, SQLITE_FCNTL_BEGIN_ATOMIC_WRITE, 0);
+ if( rc==SQLITE_OK ){
+ rc = pager_write_pagelist(pPager, pList);
+ if( rc==SQLITE_OK && pPager->dbSize>pPager->dbFileSize ){
+ char *pTmp = pPager->pTmpSpace;
+ int szPage = (int)pPager->pageSize;
+ memset(pTmp, 0, szPage);
+ rc = sqlite3OsWrite(pPager->fd, pTmp, szPage,
+ ((i64)pPager->dbSize*pPager->pageSize)-szPage);
+ }
+ if( rc==SQLITE_OK ){
+ rc = sqlite3OsFileControl(fd, SQLITE_FCNTL_COMMIT_ATOMIC_WRITE, 0);
+ }
+ if( rc!=SQLITE_OK ){
+ sqlite3OsFileControlHint(fd, SQLITE_FCNTL_ROLLBACK_ATOMIC_WRITE, 0);
+ }
+ }
+
+ if( (rc&0xFF)==SQLITE_IOERR && rc!=SQLITE_IOERR_NOMEM ){
+ rc = sqlite3JournalCreate(pPager->jfd);
+ if( rc!=SQLITE_OK ){
+ sqlite3OsClose(pPager->jfd);
+ goto commit_phase_one_exit;
+ }
+ bBatch = 0;
+ }else{
+ sqlite3OsClose(pPager->jfd);
+ }
+ }
+#endif /* SQLITE_ENABLE_BATCH_ATOMIC_WRITE */
+
+ if( bBatch==0 ){
+ rc = pager_write_pagelist(pPager, pList);
+ }
+ if( rc!=SQLITE_OK ){
+ assert( rc!=SQLITE_IOERR_BLOCKED );
+ goto commit_phase_one_exit;
+ }
+ sqlite3PcacheCleanAll(pPager->pPCache);
+
+ /* If the file on disk is smaller than the database image, use
+ ** pager_truncate to grow the file here. This can happen if the database
+ ** image was extended as part of the current transaction and then the
+ ** last page in the db image moved to the free-list. In this case the
+ ** last page is never written out to disk, leaving the database file
+ ** undersized. Fix this now if it is the case. */
+ if( pPager->dbSize>pPager->dbFileSize ){
+ Pgno nNew = pPager->dbSize - (pPager->dbSize==PAGER_SJ_PGNO(pPager));
+ assert( pPager->eState==PAGER_WRITER_DBMOD );
+ rc = pager_truncate(pPager, nNew);
+ if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+ }
+
+ /* Finally, sync the database file. */
+ if( !noSync ){
+ rc = sqlite3PagerSync(pPager, zSuper);
+ }
+ IOTRACE(("DBSYNC %p\n", pPager))
+ }
+ }
+
+commit_phase_one_exit:
+ if( rc==SQLITE_OK && !pagerUseWal(pPager) ){
+ pPager->eState = PAGER_WRITER_FINISHED;
+ }
+ return rc;
+}
+
+
+/*
+** When this function is called, the database file has been completely
+** updated to reflect the changes made by the current transaction and
+** synced to disk. The journal file still exists in the file-system
+** though, and if a failure occurs at this point it will eventually
+** be used as a hot-journal and the current transaction rolled back.
+**
+** This function finalizes the journal file, either by deleting,
+** truncating or partially zeroing it, so that it cannot be used
+** for hot-journal rollback. Once this is done the transaction is
+** irrevocably committed.
+**
+** If an error occurs, an IO error code is returned and the pager
+** moves into the error state. Otherwise, SQLITE_OK is returned.
+*/
+int sqlite3PagerCommitPhaseTwo(Pager *pPager){
+ int rc = SQLITE_OK; /* Return code */
+
+ /* This routine should not be called if a prior error has occurred.
+ ** But if (due to a coding error elsewhere in the system) it does get
+ ** called, just return the same error code without doing anything. */
+ if( NEVER(pPager->errCode) ) return pPager->errCode;
+ pPager->iDataVersion++;
+
+ assert( pPager->eState==PAGER_WRITER_LOCKED
+ || pPager->eState==PAGER_WRITER_FINISHED
+ || (pagerUseWal(pPager) && pPager->eState==PAGER_WRITER_CACHEMOD)
+ );
+ assert( assert_pager_state(pPager) );
+
+ /* An optimization. If the database was not actually modified during
+ ** this transaction, the pager is running in exclusive-mode and is
+ ** using persistent journals, then this function is a no-op.
+ **
+ ** The start of the journal file currently contains a single journal
+ ** header with the nRec field set to 0. If such a journal is used as
+ ** a hot-journal during hot-journal rollback, 0 changes will be made
+ ** to the database file. So there is no need to zero the journal
+ ** header. Since the pager is in exclusive mode, there is no need
+ ** to drop any locks either.
+ */
+ if( pPager->eState==PAGER_WRITER_LOCKED
+ && pPager->exclusiveMode
+ && pPager->journalMode==PAGER_JOURNALMODE_PERSIST
+ ){
+ assert( pPager->journalOff==JOURNAL_HDR_SZ(pPager) || !pPager->journalOff );
+ pPager->eState = PAGER_READER;
+ return SQLITE_OK;
+ }
+
+ PAGERTRACE(("COMMIT %d\n", PAGERID(pPager)));
+ rc = pager_end_transaction(pPager, pPager->setSuper, 1);
+ return pager_error(pPager, rc);
+}
+
+/*
+** If a write transaction is open, then all changes made within the
+** transaction are reverted and the current write-transaction is closed.
+** The pager falls back to PAGER_READER state if successful, or PAGER_ERROR
+** state if an error occurs.
+**
+** If the pager is already in PAGER_ERROR state when this function is called,
+** it returns Pager.errCode immediately. No work is performed in this case.
+**
+** Otherwise, in rollback mode, this function performs two functions:
+**
+** 1) It rolls back the journal file, restoring all database file and
+** in-memory cache pages to the state they were in when the transaction
+** was opened, and
+**
+** 2) It finalizes the journal file, so that it is not used for hot
+** rollback at any point in the future.
+**
+** Finalization of the journal file (task 2) is only performed if the
+** rollback is successful.
+**
+** In WAL mode, all cache-entries containing data modified within the
+** current transaction are either expelled from the cache or reverted to
+** their pre-transaction state by re-reading data from the database or
+** WAL files. The WAL transaction is then closed.
+*/
+int sqlite3PagerRollback(Pager *pPager){
+ int rc = SQLITE_OK; /* Return code */
+ PAGERTRACE(("ROLLBACK %d\n", PAGERID(pPager)));
+
+ /* PagerRollback() is a no-op if called in READER or OPEN state. If
+ ** the pager is already in the ERROR state, the rollback is not
+ ** attempted here. Instead, the error code is returned to the caller.
+ */
+ assert( assert_pager_state(pPager) );
+ if( pPager->eState==PAGER_ERROR ) return pPager->errCode;
+ if( pPager->eState<=PAGER_READER ) return SQLITE_OK;
+
+ if( pagerUseWal(pPager) ){
+ int rc2;
+ rc = sqlite3PagerSavepoint(pPager, SAVEPOINT_ROLLBACK, -1);
+ rc2 = pager_end_transaction(pPager, pPager->setSuper, 0);
+ if( rc==SQLITE_OK ) rc = rc2;
+ }else if( !isOpen(pPager->jfd) || pPager->eState==PAGER_WRITER_LOCKED ){
+ int eState = pPager->eState;
+ rc = pager_end_transaction(pPager, 0, 0);
+ if( !MEMDB && eState>PAGER_WRITER_LOCKED ){
+ /* This can happen using journal_mode=off. Move the pager to the error
+ ** state to indicate that the contents of the cache may not be trusted.
+ ** Any active readers will get SQLITE_ABORT.
+ */
+ pPager->errCode = SQLITE_ABORT;
+ pPager->eState = PAGER_ERROR;
+ setGetterMethod(pPager);
+ return rc;
+ }
+ }else{
+ rc = pager_playback(pPager, 0);
+ }
+
+ assert( pPager->eState==PAGER_READER || rc!=SQLITE_OK );
+ assert( rc==SQLITE_OK || rc==SQLITE_FULL || rc==SQLITE_CORRUPT
+ || rc==SQLITE_NOMEM || (rc&0xFF)==SQLITE_IOERR
+ || rc==SQLITE_CANTOPEN
+ );
+
+ /* If an error occurs during a ROLLBACK, we can no longer trust the pager
+ ** cache. So call pager_error() on the way out to make any error persistent.
+ */
+ return pager_error(pPager, rc);
+}
+
+/*
+** Return TRUE if the database file is opened read-only. Return FALSE
+** if the database is (in theory) writable.
+*/
+u8 sqlite3PagerIsreadonly(Pager *pPager){
+ return pPager->readOnly;
+}
+
+#ifdef SQLITE_DEBUG
+/*
+** Return the sum of the reference counts for all pages held by pPager.
+*/
+int sqlite3PagerRefcount(Pager *pPager){
+ return sqlite3PcacheRefCount(pPager->pPCache);
+}
+#endif
+
+/*
+** Return the approximate number of bytes of memory currently
+** used by the pager and its associated cache.
+*/
+int sqlite3PagerMemUsed(Pager *pPager){
+ int perPageSize = pPager->pageSize + pPager->nExtra
+ + (int)(sizeof(PgHdr) + 5*sizeof(void*));
+ return perPageSize*sqlite3PcachePagecount(pPager->pPCache)
+ + sqlite3MallocSize(pPager)
+ + pPager->pageSize;
+}
+
+/*
+** Return the number of references to the specified page.
+*/
+int sqlite3PagerPageRefcount(DbPage *pPage){
+ return sqlite3PcachePageRefcount(pPage);
+}
+
+#ifdef SQLITE_TEST
+/*
+** This routine is used for testing and analysis only.
+*/
+int *sqlite3PagerStats(Pager *pPager){
+ static int a[11];
+ a[0] = sqlite3PcacheRefCount(pPager->pPCache);
+ a[1] = sqlite3PcachePagecount(pPager->pPCache);
+ a[2] = sqlite3PcacheGetCachesize(pPager->pPCache);
+ a[3] = pPager->eState==PAGER_OPEN ? -1 : (int) pPager->dbSize;
+ a[4] = pPager->eState;
+ a[5] = pPager->errCode;
+ a[6] = (int)pPager->aStat[PAGER_STAT_HIT] & 0x7fffffff;
+ a[7] = (int)pPager->aStat[PAGER_STAT_MISS] & 0x7fffffff;
+ a[8] = 0; /* Used to be pPager->nOvfl */
+ a[9] = pPager->nRead;
+ a[10] = (int)pPager->aStat[PAGER_STAT_WRITE] & 0x7fffffff;
+ return a;
+}
+#endif
+
+/*
+** Parameter eStat must be one of SQLITE_DBSTATUS_CACHE_HIT, _MISS, _WRITE,
+** or _WRITE+1. The SQLITE_DBSTATUS_CACHE_WRITE+1 case is a translation
+** of SQLITE_DBSTATUS_CACHE_SPILL. The _SPILL case is not contiguous because
+** it was added later.
+**
+** Before returning, *pnVal is incremented by the
+** current cache hit or miss count, according to the value of eStat. If the
+** reset parameter is non-zero, the cache hit or miss count is zeroed before
+** returning.
+*/
+void sqlite3PagerCacheStat(Pager *pPager, int eStat, int reset, u64 *pnVal){
+
+ assert( eStat==SQLITE_DBSTATUS_CACHE_HIT
+ || eStat==SQLITE_DBSTATUS_CACHE_MISS
+ || eStat==SQLITE_DBSTATUS_CACHE_WRITE
+ || eStat==SQLITE_DBSTATUS_CACHE_WRITE+1
+ );
+
+ assert( SQLITE_DBSTATUS_CACHE_HIT+1==SQLITE_DBSTATUS_CACHE_MISS );
+ assert( SQLITE_DBSTATUS_CACHE_HIT+2==SQLITE_DBSTATUS_CACHE_WRITE );
+ assert( PAGER_STAT_HIT==0 && PAGER_STAT_MISS==1
+ && PAGER_STAT_WRITE==2 && PAGER_STAT_SPILL==3 );
+
+ eStat -= SQLITE_DBSTATUS_CACHE_HIT;
+ *pnVal += pPager->aStat[eStat];
+ if( reset ){
+ pPager->aStat[eStat] = 0;
+ }
+}
+
+/*
+** Return true if this is an in-memory or temp-file backed pager.
+*/
+int sqlite3PagerIsMemdb(Pager *pPager){
+ return pPager->tempFile || pPager->memVfs;
+}
+
+/*
+** Check that there are at least nSavepoint savepoints open. If there are
+** currently less than nSavepoints open, then open one or more savepoints
+** to make up the difference. If the number of savepoints is already
+** equal to nSavepoint, then this function is a no-op.
+**
+** If a memory allocation fails, SQLITE_NOMEM is returned. If an error
+** occurs while opening the sub-journal file, then an IO error code is
+** returned. Otherwise, SQLITE_OK.
+*/
+static SQLITE_NOINLINE int pagerOpenSavepoint(Pager *pPager, int nSavepoint){
+ int rc = SQLITE_OK; /* Return code */
+ int nCurrent = pPager->nSavepoint; /* Current number of savepoints */
+ int ii; /* Iterator variable */
+ PagerSavepoint *aNew; /* New Pager.aSavepoint array */
+
+ assert( pPager->eState>=PAGER_WRITER_LOCKED );
+ assert( assert_pager_state(pPager) );
+ assert( nSavepoint>nCurrent && pPager->useJournal );
+
+ /* Grow the Pager.aSavepoint array using realloc(). Return SQLITE_NOMEM
+ ** if the allocation fails. Otherwise, zero the new portion in case a
+ ** malloc failure occurs while populating it in the for(...) loop below.
+ */
+ aNew = (PagerSavepoint *)sqlite3Realloc(
+ pPager->aSavepoint, sizeof(PagerSavepoint)*nSavepoint
+ );
+ if( !aNew ){
+ return SQLITE_NOMEM_BKPT;
+ }
+ memset(&aNew[nCurrent], 0, (nSavepoint-nCurrent) * sizeof(PagerSavepoint));
+ pPager->aSavepoint = aNew;
+
+ /* Populate the PagerSavepoint structures just allocated. */
+ for(ii=nCurrent; ii<nSavepoint; ii++){
+ aNew[ii].nOrig = pPager->dbSize;
+ if( isOpen(pPager->jfd) && pPager->journalOff>0 ){
+ aNew[ii].iOffset = pPager->journalOff;
+ }else{
+ aNew[ii].iOffset = JOURNAL_HDR_SZ(pPager);
+ }
+ aNew[ii].iSubRec = pPager->nSubRec;
+ aNew[ii].pInSavepoint = sqlite3BitvecCreate(pPager->dbSize);
+ aNew[ii].bTruncateOnRelease = 1;
+ if( !aNew[ii].pInSavepoint ){
+ return SQLITE_NOMEM_BKPT;
+ }
+ if( pagerUseWal(pPager) ){
+ sqlite3WalSavepoint(pPager->pWal, aNew[ii].aWalData);
+ }
+ pPager->nSavepoint = ii+1;
+ }
+ assert( pPager->nSavepoint==nSavepoint );
+ assertTruncateConstraint(pPager);
+ return rc;
+}
+int sqlite3PagerOpenSavepoint(Pager *pPager, int nSavepoint){
+ assert( pPager->eState>=PAGER_WRITER_LOCKED );
+ assert( assert_pager_state(pPager) );
+
+ if( nSavepoint>pPager->nSavepoint && pPager->useJournal ){
+ return pagerOpenSavepoint(pPager, nSavepoint);
+ }else{
+ return SQLITE_OK;
+ }
+}
+
+
+/*
+** This function is called to rollback or release (commit) a savepoint.
+** The savepoint to release or rollback need not be the most recently
+** created savepoint.
+**
+** Parameter op is always either SAVEPOINT_ROLLBACK or SAVEPOINT_RELEASE.
+** If it is SAVEPOINT_RELEASE, then release and destroy the savepoint with
+** index iSavepoint. If it is SAVEPOINT_ROLLBACK, then rollback all changes
+** that have occurred since the specified savepoint was created.
+**
+** The savepoint to rollback or release is identified by parameter
+** iSavepoint. A value of 0 means to operate on the outermost savepoint
+** (the first created). A value of (Pager.nSavepoint-1) means operate
+** on the most recently created savepoint. If iSavepoint is greater than
+** (Pager.nSavepoint-1), then this function is a no-op.
+**
+** If a negative value is passed to this function, then the current
+** transaction is rolled back. This is different to calling
+** sqlite3PagerRollback() because this function does not terminate
+** the transaction or unlock the database, it just restores the
+** contents of the database to its original state.
+**
+** In any case, all savepoints with an index greater than iSavepoint
+** are destroyed. If this is a release operation (op==SAVEPOINT_RELEASE),
+** then savepoint iSavepoint is also destroyed.
+**
+** This function may return SQLITE_NOMEM if a memory allocation fails,
+** or an IO error code if an IO error occurs while rolling back a
+** savepoint. If no errors occur, SQLITE_OK is returned.
+*/
+int sqlite3PagerSavepoint(Pager *pPager, int op, int iSavepoint){
+ int rc = pPager->errCode;
+
+#ifdef SQLITE_ENABLE_ZIPVFS
+ if( op==SAVEPOINT_RELEASE ) rc = SQLITE_OK;
+#endif
+
+ assert( op==SAVEPOINT_RELEASE || op==SAVEPOINT_ROLLBACK );
+ assert( iSavepoint>=0 || op==SAVEPOINT_ROLLBACK );
+
+ if( rc==SQLITE_OK && iSavepoint<pPager->nSavepoint ){
+ int ii; /* Iterator variable */
+ int nNew; /* Number of remaining savepoints after this op. */
+
+ /* Figure out how many savepoints will still be active after this
+ ** operation. Store this value in nNew. Then free resources associated
+ ** with any savepoints that are destroyed by this operation.
+ */
+ nNew = iSavepoint + (( op==SAVEPOINT_RELEASE ) ? 0 : 1);
+ for(ii=nNew; ii<pPager->nSavepoint; ii++){
+ sqlite3BitvecDestroy(pPager->aSavepoint[ii].pInSavepoint);
+ }
+ pPager->nSavepoint = nNew;
+
+ /* Truncate the sub-journal so that it only includes the parts
+ ** that are still in use. */
+ if( op==SAVEPOINT_RELEASE ){
+ PagerSavepoint *pRel = &pPager->aSavepoint[nNew];
+ if( pRel->bTruncateOnRelease && isOpen(pPager->sjfd) ){
+ /* Only truncate if it is an in-memory sub-journal. */
+ if( sqlite3JournalIsInMemory(pPager->sjfd) ){
+ i64 sz = (pPager->pageSize+4)*(i64)pRel->iSubRec;
+ rc = sqlite3OsTruncate(pPager->sjfd, sz);
+ assert( rc==SQLITE_OK );
+ }
+ pPager->nSubRec = pRel->iSubRec;
+ }
+ }
+ /* Else this is a rollback operation, playback the specified savepoint.
+ ** If this is a temp-file, it is possible that the journal file has
+ ** not yet been opened. In this case there have been no changes to
+ ** the database file, so the playback operation can be skipped.
+ */
+ else if( pagerUseWal(pPager) || isOpen(pPager->jfd) ){
+ PagerSavepoint *pSavepoint = (nNew==0)?0:&pPager->aSavepoint[nNew-1];
+ rc = pagerPlaybackSavepoint(pPager, pSavepoint);
+ assert(rc!=SQLITE_DONE);
+ }
+
+#ifdef SQLITE_ENABLE_ZIPVFS
+ /* If the cache has been modified but the savepoint cannot be rolled
+ ** back journal_mode=off, put the pager in the error state. This way,
+ ** if the VFS used by this pager includes ZipVFS, the entire transaction
+ ** can be rolled back at the ZipVFS level. */
+ else if(
+ pPager->journalMode==PAGER_JOURNALMODE_OFF
+ && pPager->eState>=PAGER_WRITER_CACHEMOD
+ ){
+ pPager->errCode = SQLITE_ABORT;
+ pPager->eState = PAGER_ERROR;
+ setGetterMethod(pPager);
+ }
+#endif
+ }
+
+ return rc;
+}
+
+/*
+** Return the full pathname of the database file.
+**
+** Except, if the pager is in-memory only, then return an empty string if
+** nullIfMemDb is true. This routine is called with nullIfMemDb==1 when
+** used to report the filename to the user, for compatibility with legacy
+** behavior. But when the Btree needs to know the filename for matching to
+** shared cache, it uses nullIfMemDb==0 so that in-memory databases can
+** participate in shared-cache.
+**
+** The return value to this routine is always safe to use with
+** sqlite3_uri_parameter() and sqlite3_filename_database() and friends.
+*/
+const char *sqlite3PagerFilename(const Pager *pPager, int nullIfMemDb){
+ static const char zFake[8] = { 0, 0, 0, 0, 0, 0, 0, 0 };
+ if( nullIfMemDb && (pPager->memDb || sqlite3IsMemdb(pPager->pVfs)) ){
+ return &zFake[4];
+ }else{
+ return pPager->zFilename;
+ }
+}
+
+/*
+** Return the VFS structure for the pager.
+*/
+sqlite3_vfs *sqlite3PagerVfs(Pager *pPager){
+ return pPager->pVfs;
+}
+
+/*
+** Return the file handle for the database file associated
+** with the pager. This might return NULL if the file has
+** not yet been opened.
+*/
+sqlite3_file *sqlite3PagerFile(Pager *pPager){
+ return pPager->fd;
+}
+
+/*
+** Return the file handle for the journal file (if it exists).
+** This will be either the rollback journal or the WAL file.
+*/
+sqlite3_file *sqlite3PagerJrnlFile(Pager *pPager){
+#if SQLITE_OMIT_WAL
+ return pPager->jfd;
+#else
+ return pPager->pWal ? sqlite3WalFile(pPager->pWal) : pPager->jfd;
+#endif
+}
+
+/*
+** Return the full pathname of the journal file.
+*/
+const char *sqlite3PagerJournalname(Pager *pPager){
+ return pPager->zJournal;
+}
+
+#ifndef SQLITE_OMIT_AUTOVACUUM
+/*
+** Move the page pPg to location pgno in the file.
+**
+** There must be no references to the page previously located at
+** pgno (which we call pPgOld) though that page is allowed to be
+** in cache. If the page previously located at pgno is not already
+** in the rollback journal, it is not put there by by this routine.
+**
+** References to the page pPg remain valid. Updating any
+** meta-data associated with pPg (i.e. data stored in the nExtra bytes
+** allocated along with the page) is the responsibility of the caller.
+**
+** A transaction must be active when this routine is called. It used to be
+** required that a statement transaction was not active, but this restriction
+** has been removed (CREATE INDEX needs to move a page when a statement
+** transaction is active).
+**
+** If the fourth argument, isCommit, is non-zero, then this page is being
+** moved as part of a database reorganization just before the transaction
+** is being committed. In this case, it is guaranteed that the database page
+** pPg refers to will not be written to again within this transaction.
+**
+** This function may return SQLITE_NOMEM or an IO error code if an error
+** occurs. Otherwise, it returns SQLITE_OK.
+*/
+int sqlite3PagerMovepage(Pager *pPager, DbPage *pPg, Pgno pgno, int isCommit){
+ PgHdr *pPgOld; /* The page being overwritten. */
+ Pgno needSyncPgno = 0; /* Old value of pPg->pgno, if sync is required */
+ int rc; /* Return code */
+ Pgno origPgno; /* The original page number */
+
+ assert( pPg->nRef>0 );
+ assert( pPager->eState==PAGER_WRITER_CACHEMOD
+ || pPager->eState==PAGER_WRITER_DBMOD
+ );
+ assert( assert_pager_state(pPager) );
+
+ /* In order to be able to rollback, an in-memory database must journal
+ ** the page we are moving from.
+ */
+ assert( pPager->tempFile || !MEMDB );
+ if( pPager->tempFile ){
+ rc = sqlite3PagerWrite(pPg);
+ if( rc ) return rc;
+ }
+
+ /* If the page being moved is dirty and has not been saved by the latest
+ ** savepoint, then save the current contents of the page into the
+ ** sub-journal now. This is required to handle the following scenario:
+ **
+ ** BEGIN;
+ ** <journal page X, then modify it in memory>
+ ** SAVEPOINT one;
+ ** <Move page X to location Y>
+ ** ROLLBACK TO one;
+ **
+ ** If page X were not written to the sub-journal here, it would not
+ ** be possible to restore its contents when the "ROLLBACK TO one"
+ ** statement were is processed.
+ **
+ ** subjournalPage() may need to allocate space to store pPg->pgno into
+ ** one or more savepoint bitvecs. This is the reason this function
+ ** may return SQLITE_NOMEM.
+ */
+ if( (pPg->flags & PGHDR_DIRTY)!=0
+ && SQLITE_OK!=(rc = subjournalPageIfRequired(pPg))
+ ){
+ return rc;
+ }
+
+ PAGERTRACE(("MOVE %d page %d (needSync=%d) moves to %d\n",
+ PAGERID(pPager), pPg->pgno, (pPg->flags&PGHDR_NEED_SYNC)?1:0, pgno));
+ IOTRACE(("MOVE %p %d %d\n", pPager, pPg->pgno, pgno))
+
+ /* If the journal needs to be sync()ed before page pPg->pgno can
+ ** be written to, store pPg->pgno in local variable needSyncPgno.
+ **
+ ** If the isCommit flag is set, there is no need to remember that
+ ** the journal needs to be sync()ed before database page pPg->pgno
+ ** can be written to. The caller has already promised not to write to it.
+ */
+ if( (pPg->flags&PGHDR_NEED_SYNC) && !isCommit ){
+ needSyncPgno = pPg->pgno;
+ assert( pPager->journalMode==PAGER_JOURNALMODE_OFF ||
+ pageInJournal(pPager, pPg) || pPg->pgno>pPager->dbOrigSize );
+ assert( pPg->flags&PGHDR_DIRTY );
+ }
+
+ /* If the cache contains a page with page-number pgno, remove it
+ ** from its hash chain. Also, if the PGHDR_NEED_SYNC flag was set for
+ ** page pgno before the 'move' operation, it needs to be retained
+ ** for the page moved there.
+ */
+ pPg->flags &= ~PGHDR_NEED_SYNC;
+ pPgOld = sqlite3PagerLookup(pPager, pgno);
+ assert( !pPgOld || pPgOld->nRef==1 || CORRUPT_DB );
+ if( pPgOld ){
+ if( NEVER(pPgOld->nRef>1) ){
+ sqlite3PagerUnrefNotNull(pPgOld);
+ return SQLITE_CORRUPT_BKPT;
+ }
+ pPg->flags |= (pPgOld->flags&PGHDR_NEED_SYNC);
+ if( pPager->tempFile ){
+ /* Do not discard pages from an in-memory database since we might
+ ** need to rollback later. Just move the page out of the way. */
+ sqlite3PcacheMove(pPgOld, pPager->dbSize+1);
+ }else{
+ sqlite3PcacheDrop(pPgOld);
+ }
+ }
+
+ origPgno = pPg->pgno;
+ sqlite3PcacheMove(pPg, pgno);
+ sqlite3PcacheMakeDirty(pPg);
+
+ /* For an in-memory database, make sure the original page continues
+ ** to exist, in case the transaction needs to roll back. Use pPgOld
+ ** as the original page since it has already been allocated.
+ */
+ if( pPager->tempFile && pPgOld ){
+ sqlite3PcacheMove(pPgOld, origPgno);
+ sqlite3PagerUnrefNotNull(pPgOld);
+ }
+
+ if( needSyncPgno ){
+ /* If needSyncPgno is non-zero, then the journal file needs to be
+ ** sync()ed before any data is written to database file page needSyncPgno.
+ ** Currently, no such page exists in the page-cache and the
+ ** "is journaled" bitvec flag has been set. This needs to be remedied by
+ ** loading the page into the pager-cache and setting the PGHDR_NEED_SYNC
+ ** flag.
+ **
+ ** If the attempt to load the page into the page-cache fails, (due
+ ** to a malloc() or IO failure), clear the bit in the pInJournal[]
+ ** array. Otherwise, if the page is loaded and written again in
+ ** this transaction, it may be written to the database file before
+ ** it is synced into the journal file. This way, it may end up in
+ ** the journal file twice, but that is not a problem.
+ */
+ PgHdr *pPgHdr;
+ rc = sqlite3PagerGet(pPager, needSyncPgno, &pPgHdr, 0);
+ if( rc!=SQLITE_OK ){
+ if( needSyncPgno<=pPager->dbOrigSize ){
+ assert( pPager->pTmpSpace!=0 );
+ sqlite3BitvecClear(pPager->pInJournal, needSyncPgno, pPager->pTmpSpace);
+ }
+ return rc;
+ }
+ pPgHdr->flags |= PGHDR_NEED_SYNC;
+ sqlite3PcacheMakeDirty(pPgHdr);
+ sqlite3PagerUnrefNotNull(pPgHdr);
+ }
+
+ return SQLITE_OK;
+}
+#endif
+
+/*
+** The page handle passed as the first argument refers to a dirty page
+** with a page number other than iNew. This function changes the page's
+** page number to iNew and sets the value of the PgHdr.flags field to
+** the value passed as the third parameter.
+*/
+void sqlite3PagerRekey(DbPage *pPg, Pgno iNew, u16 flags){
+ assert( pPg->pgno!=iNew );
+ pPg->flags = flags;
+ sqlite3PcacheMove(pPg, iNew);
+}
+
+/*
+** Return a pointer to the data for the specified page.
+*/
+void *sqlite3PagerGetData(DbPage *pPg){
+ assert( pPg->nRef>0 || pPg->pPager->memDb );
+ return pPg->pData;
+}
+
+/*
+** Return a pointer to the Pager.nExtra bytes of "extra" space
+** allocated along with the specified page.
+*/
+void *sqlite3PagerGetExtra(DbPage *pPg){
+ return pPg->pExtra;
+}
+
+/*
+** Get/set the locking-mode for this pager. Parameter eMode must be one
+** of PAGER_LOCKINGMODE_QUERY, PAGER_LOCKINGMODE_NORMAL or
+** PAGER_LOCKINGMODE_EXCLUSIVE. If the parameter is not _QUERY, then
+** the locking-mode is set to the value specified.
+**
+** The returned value is either PAGER_LOCKINGMODE_NORMAL or
+** PAGER_LOCKINGMODE_EXCLUSIVE, indicating the current (possibly updated)
+** locking-mode.
+*/
+int sqlite3PagerLockingMode(Pager *pPager, int eMode){
+ assert( eMode==PAGER_LOCKINGMODE_QUERY
+ || eMode==PAGER_LOCKINGMODE_NORMAL
+ || eMode==PAGER_LOCKINGMODE_EXCLUSIVE );
+ assert( PAGER_LOCKINGMODE_QUERY<0 );
+ assert( PAGER_LOCKINGMODE_NORMAL>=0 && PAGER_LOCKINGMODE_EXCLUSIVE>=0 );
+ assert( pPager->exclusiveMode || 0==sqlite3WalHeapMemory(pPager->pWal) );
+ if( eMode>=0 && !pPager->tempFile && !sqlite3WalHeapMemory(pPager->pWal) ){
+ pPager->exclusiveMode = (u8)eMode;
+ }
+ return (int)pPager->exclusiveMode;
+}
+
+/*
+** Set the journal-mode for this pager. Parameter eMode must be one of:
+**
+** PAGER_JOURNALMODE_DELETE
+** PAGER_JOURNALMODE_TRUNCATE
+** PAGER_JOURNALMODE_PERSIST
+** PAGER_JOURNALMODE_OFF
+** PAGER_JOURNALMODE_MEMORY
+** PAGER_JOURNALMODE_WAL
+**
+** The journalmode is set to the value specified if the change is allowed.
+** The change may be disallowed for the following reasons:
+**
+** * An in-memory database can only have its journal_mode set to _OFF
+** or _MEMORY.
+**
+** * Temporary databases cannot have _WAL journalmode.
+**
+** The returned indicate the current (possibly updated) journal-mode.
+*/
+int sqlite3PagerSetJournalMode(Pager *pPager, int eMode){
+ u8 eOld = pPager->journalMode; /* Prior journalmode */
+
+ /* The eMode parameter is always valid */
+ assert( eMode==PAGER_JOURNALMODE_DELETE /* 0 */
+ || eMode==PAGER_JOURNALMODE_PERSIST /* 1 */
+ || eMode==PAGER_JOURNALMODE_OFF /* 2 */
+ || eMode==PAGER_JOURNALMODE_TRUNCATE /* 3 */
+ || eMode==PAGER_JOURNALMODE_MEMORY /* 4 */
+ || eMode==PAGER_JOURNALMODE_WAL /* 5 */ );
+
+ /* This routine is only called from the OP_JournalMode opcode, and
+ ** the logic there will never allow a temporary file to be changed
+ ** to WAL mode.
+ */
+ assert( pPager->tempFile==0 || eMode!=PAGER_JOURNALMODE_WAL );
+
+ /* Do allow the journalmode of an in-memory database to be set to
+ ** anything other than MEMORY or OFF
+ */
+ if( MEMDB ){
+ assert( eOld==PAGER_JOURNALMODE_MEMORY || eOld==PAGER_JOURNALMODE_OFF );
+ if( eMode!=PAGER_JOURNALMODE_MEMORY && eMode!=PAGER_JOURNALMODE_OFF ){
+ eMode = eOld;
+ }
+ }
+
+ if( eMode!=eOld ){
+
+ /* Change the journal mode. */
+ assert( pPager->eState!=PAGER_ERROR );
+ pPager->journalMode = (u8)eMode;
+
+ /* When transitioning from TRUNCATE or PERSIST to any other journal
+ ** mode except WAL, unless the pager is in locking_mode=exclusive mode,
+ ** delete the journal file.
+ */
+ assert( (PAGER_JOURNALMODE_TRUNCATE & 5)==1 );
+ assert( (PAGER_JOURNALMODE_PERSIST & 5)==1 );
+ assert( (PAGER_JOURNALMODE_DELETE & 5)==0 );
+ assert( (PAGER_JOURNALMODE_MEMORY & 5)==4 );
+ assert( (PAGER_JOURNALMODE_OFF & 5)==0 );
+ assert( (PAGER_JOURNALMODE_WAL & 5)==5 );
+
+ assert( isOpen(pPager->fd) || pPager->exclusiveMode );
+ if( !pPager->exclusiveMode && (eOld & 5)==1 && (eMode & 1)==0 ){
+ /* In this case we would like to delete the journal file. If it is
+ ** not possible, then that is not a problem. Deleting the journal file
+ ** here is an optimization only.
+ **
+ ** Before deleting the journal file, obtain a RESERVED lock on the
+ ** database file. This ensures that the journal file is not deleted
+ ** while it is in use by some other client.
+ */
+ sqlite3OsClose(pPager->jfd);
+ if( pPager->eLock>=RESERVED_LOCK ){
+ sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
+ }else{
+ int rc = SQLITE_OK;
+ int state = pPager->eState;
+ assert( state==PAGER_OPEN || state==PAGER_READER );
+ if( state==PAGER_OPEN ){
+ rc = sqlite3PagerSharedLock(pPager);
+ }
+ if( pPager->eState==PAGER_READER ){
+ assert( rc==SQLITE_OK );
+ rc = pagerLockDb(pPager, RESERVED_LOCK);
+ }
+ if( rc==SQLITE_OK ){
+ sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
+ }
+ if( rc==SQLITE_OK && state==PAGER_READER ){
+ pagerUnlockDb(pPager, SHARED_LOCK);
+ }else if( state==PAGER_OPEN ){
+ pager_unlock(pPager);
+ }
+ assert( state==pPager->eState );
+ }
+ }else if( eMode==PAGER_JOURNALMODE_OFF || eMode==PAGER_JOURNALMODE_MEMORY ){
+ sqlite3OsClose(pPager->jfd);
+ }
+ }
+
+ /* Return the new journal mode */
+ return (int)pPager->journalMode;
+}
+
+/*
+** Return the current journal mode.
+*/
+int sqlite3PagerGetJournalMode(Pager *pPager){
+ return (int)pPager->journalMode;
+}
+
+/*
+** Return TRUE if the pager is in a state where it is OK to change the
+** journalmode. Journalmode changes can only happen when the database
+** is unmodified.
+*/
+int sqlite3PagerOkToChangeJournalMode(Pager *pPager){
+ assert( assert_pager_state(pPager) );
+ if( pPager->eState>=PAGER_WRITER_CACHEMOD ) return 0;
+ if( NEVER(isOpen(pPager->jfd) && pPager->journalOff>0) ) return 0;
+ return 1;
+}
+
+/*
+** Get/set the size-limit used for persistent journal files.
+**
+** Setting the size limit to -1 means no limit is enforced.
+** An attempt to set a limit smaller than -1 is a no-op.
+*/
+i64 sqlite3PagerJournalSizeLimit(Pager *pPager, i64 iLimit){
+ if( iLimit>=-1 ){
+ pPager->journalSizeLimit = iLimit;
+ sqlite3WalLimit(pPager->pWal, iLimit);
+ }
+ return pPager->journalSizeLimit;
+}
+
+/*
+** Return a pointer to the pPager->pBackup variable. The backup module
+** in backup.c maintains the content of this variable. This module
+** uses it opaquely as an argument to sqlite3BackupRestart() and
+** sqlite3BackupUpdate() only.
+*/
+sqlite3_backup **sqlite3PagerBackupPtr(Pager *pPager){
+ return &pPager->pBackup;
+}
+
+#ifndef SQLITE_OMIT_VACUUM
+/*
+** Unless this is an in-memory or temporary database, clear the pager cache.
+*/
+void sqlite3PagerClearCache(Pager *pPager){
+ assert( MEMDB==0 || pPager->tempFile );
+ if( pPager->tempFile==0 ) pager_reset(pPager);
+}
+#endif
+
+
+#ifndef SQLITE_OMIT_WAL
+/*
+** This function is called when the user invokes "PRAGMA wal_checkpoint",
+** "PRAGMA wal_blocking_checkpoint" or calls the sqlite3_wal_checkpoint()
+** or wal_blocking_checkpoint() API functions.
+**
+** Parameter eMode is one of SQLITE_CHECKPOINT_PASSIVE, FULL or RESTART.
+*/
+int sqlite3PagerCheckpoint(
+ Pager *pPager, /* Checkpoint on this pager */
+ sqlite3 *db, /* Db handle used to check for interrupts */
+ int eMode, /* Type of checkpoint */
+ int *pnLog, /* OUT: Final number of frames in log */
+ int *pnCkpt /* OUT: Final number of checkpointed frames */
+){
+ int rc = SQLITE_OK;
+ if( pPager->pWal==0 && pPager->journalMode==PAGER_JOURNALMODE_WAL ){
+ /* This only happens when a database file is zero bytes in size opened and
+ ** then "PRAGMA journal_mode=WAL" is run and then sqlite3_wal_checkpoint()
+ ** is invoked without any intervening transactions. We need to start
+ ** a transaction to initialize pWal. The PRAGMA table_list statement is
+ ** used for this since it starts transactions on every database file,
+ ** including all ATTACHed databases. This seems expensive for a single
+ ** sqlite3_wal_checkpoint() call, but it happens very rarely.
+ ** https://sqlite.org/forum/forumpost/fd0f19d229156939
+ */
+ sqlite3_exec(db, "PRAGMA table_list",0,0,0);
+ }
+ if( pPager->pWal ){
+ rc = sqlite3WalCheckpoint(pPager->pWal, db, eMode,
+ (eMode==SQLITE_CHECKPOINT_PASSIVE ? 0 : pPager->xBusyHandler),
+ pPager->pBusyHandlerArg,
+ pPager->walSyncFlags, pPager->pageSize, (u8 *)pPager->pTmpSpace,
+ pnLog, pnCkpt
+ );
+ }
+ return rc;
+}
+
+int sqlite3PagerWalCallback(Pager *pPager){
+ return sqlite3WalCallback(pPager->pWal);
+}
+
+/*
+** Return true if the underlying VFS for the given pager supports the
+** primitives necessary for write-ahead logging.
+*/
+int sqlite3PagerWalSupported(Pager *pPager){
+ const sqlite3_io_methods *pMethods = pPager->fd->pMethods;
+ if( pPager->noLock ) return 0;
+ return pPager->exclusiveMode || (pMethods->iVersion>=2 && pMethods->xShmMap);
+}
+
+/*
+** Attempt to take an exclusive lock on the database file. If a PENDING lock
+** is obtained instead, immediately release it.
+*/
+static int pagerExclusiveLock(Pager *pPager){
+ int rc; /* Return code */
+ u8 eOrigLock; /* Original lock */
+
+ assert( pPager->eLock>=SHARED_LOCK );
+ eOrigLock = pPager->eLock;
+ rc = pagerLockDb(pPager, EXCLUSIVE_LOCK);
+ if( rc!=SQLITE_OK ){
+ /* If the attempt to grab the exclusive lock failed, release the
+ ** pending lock that may have been obtained instead. */
+ pagerUnlockDb(pPager, eOrigLock);
+ }
+
+ return rc;
+}
+
+/*
+** Call sqlite3WalOpen() to open the WAL handle. If the pager is in
+** exclusive-locking mode when this function is called, take an EXCLUSIVE
+** lock on the database file and use heap-memory to store the wal-index
+** in. Otherwise, use the normal shared-memory.
+*/
+static int pagerOpenWal(Pager *pPager){
+ int rc = SQLITE_OK;
+
+ assert( pPager->pWal==0 && pPager->tempFile==0 );
+ assert( pPager->eLock==SHARED_LOCK || pPager->eLock==EXCLUSIVE_LOCK );
+
+ /* If the pager is already in exclusive-mode, the WAL module will use
+ ** heap-memory for the wal-index instead of the VFS shared-memory
+ ** implementation. Take the exclusive lock now, before opening the WAL
+ ** file, to make sure this is safe.
+ */
+ if( pPager->exclusiveMode ){
+ rc = pagerExclusiveLock(pPager);
+ }
+
+ /* Open the connection to the log file. If this operation fails,
+ ** (e.g. due to malloc() failure), return an error code.
+ */
+ if( rc==SQLITE_OK ){
+ rc = sqlite3WalOpen(pPager->pVfs,
+ pPager->fd, pPager->zWal, pPager->exclusiveMode,
+ pPager->journalSizeLimit, &pPager->pWal
+ );
+ }
+ pagerFixMaplimit(pPager);
+
+ return rc;
+}
+
+
+/*
+** The caller must be holding a SHARED lock on the database file to call
+** this function.
+**
+** If the pager passed as the first argument is open on a real database
+** file (not a temp file or an in-memory database), and the WAL file
+** is not already open, make an attempt to open it now. If successful,
+** return SQLITE_OK. If an error occurs or the VFS used by the pager does
+** not support the xShmXXX() methods, return an error code. *pbOpen is
+** not modified in either case.
+**
+** If the pager is open on a temp-file (or in-memory database), or if
+** the WAL file is already open, set *pbOpen to 1 and return SQLITE_OK
+** without doing anything.
+*/
+int sqlite3PagerOpenWal(
+ Pager *pPager, /* Pager object */
+ int *pbOpen /* OUT: Set to true if call is a no-op */
+){
+ int rc = SQLITE_OK; /* Return code */
+
+ assert( assert_pager_state(pPager) );
+ assert( pPager->eState==PAGER_OPEN || pbOpen );
+ assert( pPager->eState==PAGER_READER || !pbOpen );
+ assert( pbOpen==0 || *pbOpen==0 );
+ assert( pbOpen!=0 || (!pPager->tempFile && !pPager->pWal) );
+
+ if( !pPager->tempFile && !pPager->pWal ){
+ if( !sqlite3PagerWalSupported(pPager) ) return SQLITE_CANTOPEN;
+
+ /* Close any rollback journal previously open */
+ sqlite3OsClose(pPager->jfd);
+
+ rc = pagerOpenWal(pPager);
+ if( rc==SQLITE_OK ){
+ pPager->journalMode = PAGER_JOURNALMODE_WAL;
+ pPager->eState = PAGER_OPEN;
+ }
+ }else{
+ *pbOpen = 1;
+ }
+
+ return rc;
+}
+
+/*
+** This function is called to close the connection to the log file prior
+** to switching from WAL to rollback mode.
+**
+** Before closing the log file, this function attempts to take an
+** EXCLUSIVE lock on the database file. If this cannot be obtained, an
+** error (SQLITE_BUSY) is returned and the log connection is not closed.
+** If successful, the EXCLUSIVE lock is not released before returning.
+*/
+int sqlite3PagerCloseWal(Pager *pPager, sqlite3 *db){
+ int rc = SQLITE_OK;
+
+ assert( pPager->journalMode==PAGER_JOURNALMODE_WAL );
+
+ /* If the log file is not already open, but does exist in the file-system,
+ ** it may need to be checkpointed before the connection can switch to
+ ** rollback mode. Open it now so this can happen.
+ */
+ if( !pPager->pWal ){
+ int logexists = 0;
+ rc = pagerLockDb(pPager, SHARED_LOCK);
+ if( rc==SQLITE_OK ){
+ rc = sqlite3OsAccess(
+ pPager->pVfs, pPager->zWal, SQLITE_ACCESS_EXISTS, &logexists
+ );
+ }
+ if( rc==SQLITE_OK && logexists ){
+ rc = pagerOpenWal(pPager);
+ }
+ }
+
+ /* Checkpoint and close the log. Because an EXCLUSIVE lock is held on
+ ** the database file, the log and log-summary files will be deleted.
+ */
+ if( rc==SQLITE_OK && pPager->pWal ){
+ rc = pagerExclusiveLock(pPager);
+ if( rc==SQLITE_OK ){
+ rc = sqlite3WalClose(pPager->pWal, db, pPager->walSyncFlags,
+ pPager->pageSize, (u8*)pPager->pTmpSpace);
+ pPager->pWal = 0;
+ pagerFixMaplimit(pPager);
+ if( rc && !pPager->exclusiveMode ) pagerUnlockDb(pPager, SHARED_LOCK);
+ }
+ }
+ return rc;
+}
+
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+/*
+** If pager pPager is a wal-mode database not in exclusive locking mode,
+** invoke the sqlite3WalWriteLock() function on the associated Wal object
+** with the same db and bLock parameters as were passed to this function.
+** Return an SQLite error code if an error occurs, or SQLITE_OK otherwise.
+*/
+int sqlite3PagerWalWriteLock(Pager *pPager, int bLock){
+ int rc = SQLITE_OK;
+ if( pagerUseWal(pPager) && pPager->exclusiveMode==0 ){
+ rc = sqlite3WalWriteLock(pPager->pWal, bLock);
+ }
+ return rc;
+}
+
+/*
+** Set the database handle used by the wal layer to determine if
+** blocking locks are required.
+*/
+void sqlite3PagerWalDb(Pager *pPager, sqlite3 *db){
+ if( pagerUseWal(pPager) ){
+ sqlite3WalDb(pPager->pWal, db);
+ }
+}
+#endif
+
+#ifdef SQLITE_ENABLE_SNAPSHOT
+/*
+** If this is a WAL database, obtain a snapshot handle for the snapshot
+** currently open. Otherwise, return an error.
+*/
+int sqlite3PagerSnapshotGet(Pager *pPager, sqlite3_snapshot **ppSnapshot){
+ int rc = SQLITE_ERROR;
+ if( pPager->pWal ){
+ rc = sqlite3WalSnapshotGet(pPager->pWal, ppSnapshot);
+ }
+ return rc;
+}
+
+/*
+** If this is a WAL database, store a pointer to pSnapshot. Next time a
+** read transaction is opened, attempt to read from the snapshot it
+** identifies. If this is not a WAL database, return an error.
+*/
+int sqlite3PagerSnapshotOpen(
+ Pager *pPager,
+ sqlite3_snapshot *pSnapshot
+){
+ int rc = SQLITE_OK;
+ if( pPager->pWal ){
+ sqlite3WalSnapshotOpen(pPager->pWal, pSnapshot);
+ }else{
+ rc = SQLITE_ERROR;
+ }
+ return rc;
+}
+
+/*
+** If this is a WAL database, call sqlite3WalSnapshotRecover(). If this
+** is not a WAL database, return an error.
+*/
+int sqlite3PagerSnapshotRecover(Pager *pPager){
+ int rc;
+ if( pPager->pWal ){
+ rc = sqlite3WalSnapshotRecover(pPager->pWal);
+ }else{
+ rc = SQLITE_ERROR;
+ }
+ return rc;
+}
+
+/*
+** The caller currently has a read transaction open on the database.
+** If this is not a WAL database, SQLITE_ERROR is returned. Otherwise,
+** this function takes a SHARED lock on the CHECKPOINTER slot and then
+** checks if the snapshot passed as the second argument is still
+** available. If so, SQLITE_OK is returned.
+**
+** If the snapshot is not available, SQLITE_ERROR is returned. Or, if
+** the CHECKPOINTER lock cannot be obtained, SQLITE_BUSY. If any error
+** occurs (any value other than SQLITE_OK is returned), the CHECKPOINTER
+** lock is released before returning.
+*/
+int sqlite3PagerSnapshotCheck(Pager *pPager, sqlite3_snapshot *pSnapshot){
+ int rc;
+ if( pPager->pWal ){
+ rc = sqlite3WalSnapshotCheck(pPager->pWal, pSnapshot);
+ }else{
+ rc = SQLITE_ERROR;
+ }
+ return rc;
+}
+
+/*
+** Release a lock obtained by an earlier successful call to
+** sqlite3PagerSnapshotCheck().
+*/
+void sqlite3PagerSnapshotUnlock(Pager *pPager){
+ assert( pPager->pWal );
+ sqlite3WalSnapshotUnlock(pPager->pWal);
+}
+
+#endif /* SQLITE_ENABLE_SNAPSHOT */
+#endif /* !SQLITE_OMIT_WAL */
+
+#ifdef SQLITE_ENABLE_ZIPVFS
+/*
+** A read-lock must be held on the pager when this function is called. If
+** the pager is in WAL mode and the WAL file currently contains one or more
+** frames, return the size in bytes of the page images stored within the
+** WAL frames. Otherwise, if this is not a WAL database or the WAL file
+** is empty, return 0.
+*/
+int sqlite3PagerWalFramesize(Pager *pPager){
+ assert( pPager->eState>=PAGER_READER );
+ return sqlite3WalFramesize(pPager->pWal);
+}
+#endif
+
+#if defined(SQLITE_USE_SEH) && !defined(SQLITE_OMIT_WAL)
+int sqlite3PagerWalSystemErrno(Pager *pPager){
+ return sqlite3WalSystemErrno(pPager->pWal);
+}
+#endif
+
+#endif /* SQLITE_OMIT_DISKIO */