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Diffstat (limited to 'src/os.h')
| -rw-r--r-- | src/os.h | 225 |
1 files changed, 225 insertions, 0 deletions
diff --git a/src/os.h b/src/os.h new file mode 100644 index 0000000..aeb0172 --- /dev/null +++ b/src/os.h @@ -0,0 +1,225 @@ +/* +** 2001 September 16 +** +** 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 header file (together with is companion C source-code file +** "os.c") attempt to abstract the underlying operating system so that +** the SQLite library will work on both POSIX and windows systems. +** +** This header file is #include-ed by sqliteInt.h and thus ends up +** being included by every source file. +*/ +#ifndef _SQLITE_OS_H_ +#define _SQLITE_OS_H_ + +/* +** Attempt to automatically detect the operating system and setup the +** necessary pre-processor macros for it. +*/ +#include "os_setup.h" + +/* If the SET_FULLSYNC macro is not defined above, then make it +** a no-op +*/ +#ifndef SET_FULLSYNC +# define SET_FULLSYNC(x,y) +#endif + +/* Maximum pathname length. Note: FILENAME_MAX defined by stdio.h +*/ +#ifndef SQLITE_MAX_PATHLEN +# define SQLITE_MAX_PATHLEN FILENAME_MAX +#endif + +/* Maximum number of symlinks that will be resolved while trying to +** expand a filename in xFullPathname() in the VFS. +*/ +#ifndef SQLITE_MAX_SYMLINK +# define SQLITE_MAX_SYMLINK 200 +#endif + +/* +** The default size of a disk sector +*/ +#ifndef SQLITE_DEFAULT_SECTOR_SIZE +# define SQLITE_DEFAULT_SECTOR_SIZE 4096 +#endif + +/* +** Temporary files are named starting with this prefix followed by 16 random +** alphanumeric characters, and no file extension. They are stored in the +** OS's standard temporary file directory, and are deleted prior to exit. +** If sqlite is being embedded in another program, you may wish to change the +** prefix to reflect your program's name, so that if your program exits +** prematurely, old temporary files can be easily identified. This can be done +** using -DSQLITE_TEMP_FILE_PREFIX=myprefix_ on the compiler command line. +** +** 2006-10-31: The default prefix used to be "sqlite_". But then +** Mcafee started using SQLite in their anti-virus product and it +** started putting files with the "sqlite" name in the c:/temp folder. +** This annoyed many windows users. Those users would then do a +** Google search for "sqlite", find the telephone numbers of the +** developers and call to wake them up at night and complain. +** For this reason, the default name prefix is changed to be "sqlite" +** spelled backwards. So the temp files are still identified, but +** anybody smart enough to figure out the code is also likely smart +** enough to know that calling the developer will not help get rid +** of the file. +*/ +#ifndef SQLITE_TEMP_FILE_PREFIX +# define SQLITE_TEMP_FILE_PREFIX "etilqs_" +#endif + +/* +** The following values may be passed as the second argument to +** sqlite3OsLock(). The various locks exhibit the following semantics: +** +** SHARED: Any number of processes may hold a SHARED lock simultaneously. +** RESERVED: A single process may hold a RESERVED lock on a file at +** any time. Other processes may hold and obtain new SHARED locks. +** PENDING: A single process may hold a PENDING lock on a file at +** any one time. Existing SHARED locks may persist, but no new +** SHARED locks may be obtained by other processes. +** EXCLUSIVE: An EXCLUSIVE lock precludes all other locks. +** +** PENDING_LOCK may not be passed directly to sqlite3OsLock(). Instead, a +** process that requests an EXCLUSIVE lock may actually obtain a PENDING +** lock. This can be upgraded to an EXCLUSIVE lock by a subsequent call to +** sqlite3OsLock(). +*/ +#define NO_LOCK 0 +#define SHARED_LOCK 1 +#define RESERVED_LOCK 2 +#define PENDING_LOCK 3 +#define EXCLUSIVE_LOCK 4 + +/* +** File Locking Notes: (Mostly about windows but also some info for Unix) +** +** We cannot use LockFileEx() or UnlockFileEx() on Win95/98/ME because +** those functions are not available. So we use only LockFile() and +** UnlockFile(). +** +** LockFile() prevents not just writing but also reading by other processes. +** A SHARED_LOCK is obtained by locking a single randomly-chosen +** byte out of a specific range of bytes. The lock byte is obtained at +** random so two separate readers can probably access the file at the +** same time, unless they are unlucky and choose the same lock byte. +** An EXCLUSIVE_LOCK is obtained by locking all bytes in the range. +** There can only be one writer. A RESERVED_LOCK is obtained by locking +** a single byte of the file that is designated as the reserved lock byte. +** A PENDING_LOCK is obtained by locking a designated byte different from +** the RESERVED_LOCK byte. +** +** On WinNT/2K/XP systems, LockFileEx() and UnlockFileEx() are available, +** which means we can use reader/writer locks. When reader/writer locks +** are used, the lock is placed on the same range of bytes that is used +** for probabilistic locking in Win95/98/ME. Hence, the locking scheme +** will support two or more Win95 readers or two or more WinNT readers. +** But a single Win95 reader will lock out all WinNT readers and a single +** WinNT reader will lock out all other Win95 readers. +** +** The following #defines specify the range of bytes used for locking. +** SHARED_SIZE is the number of bytes available in the pool from which +** a random byte is selected for a shared lock. The pool of bytes for +** shared locks begins at SHARED_FIRST. +** +** The same locking strategy and +** byte ranges are used for Unix. This leaves open the possibility of having +** clients on win95, winNT, and unix all talking to the same shared file +** and all locking correctly. To do so would require that samba (or whatever +** tool is being used for file sharing) implements locks correctly between +** windows and unix. I'm guessing that isn't likely to happen, but by +** using the same locking range we are at least open to the possibility. +** +** Locking in windows is manditory. For this reason, we cannot store +** actual data in the bytes used for locking. The pager never allocates +** the pages involved in locking therefore. SHARED_SIZE is selected so +** that all locks will fit on a single page even at the minimum page size. +** PENDING_BYTE defines the beginning of the locks. By default PENDING_BYTE +** is set high so that we don't have to allocate an unused page except +** for very large databases. But one should test the page skipping logic +** by setting PENDING_BYTE low and running the entire regression suite. +** +** Changing the value of PENDING_BYTE results in a subtly incompatible +** file format. Depending on how it is changed, you might not notice +** the incompatibility right away, even running a full regression test. +** The default location of PENDING_BYTE is the first byte past the +** 1GB boundary. +** +*/ +#ifdef SQLITE_OMIT_WSD +# define PENDING_BYTE (0x40000000) +#else +# define PENDING_BYTE sqlite3PendingByte +#endif +#define RESERVED_BYTE (PENDING_BYTE+1) +#define SHARED_FIRST (PENDING_BYTE+2) +#define SHARED_SIZE 510 + +/* +** Wrapper around OS specific sqlite3_os_init() function. +*/ +int sqlite3OsInit(void); + +/* +** Functions for accessing sqlite3_file methods +*/ +void sqlite3OsClose(sqlite3_file*); +int sqlite3OsRead(sqlite3_file*, void*, int amt, i64 offset); +int sqlite3OsWrite(sqlite3_file*, const void*, int amt, i64 offset); +int sqlite3OsTruncate(sqlite3_file*, i64 size); +int sqlite3OsSync(sqlite3_file*, int); +int sqlite3OsFileSize(sqlite3_file*, i64 *pSize); +int sqlite3OsLock(sqlite3_file*, int); +int sqlite3OsUnlock(sqlite3_file*, int); +int sqlite3OsCheckReservedLock(sqlite3_file *id, int *pResOut); +int sqlite3OsFileControl(sqlite3_file*,int,void*); +void sqlite3OsFileControlHint(sqlite3_file*,int,void*); +#define SQLITE_FCNTL_DB_UNCHANGED 0xca093fa0 +int sqlite3OsSectorSize(sqlite3_file *id); +int sqlite3OsDeviceCharacteristics(sqlite3_file *id); +#ifndef SQLITE_OMIT_WAL +int sqlite3OsShmMap(sqlite3_file *,int,int,int,void volatile **); +int sqlite3OsShmLock(sqlite3_file *id, int, int, int); +void sqlite3OsShmBarrier(sqlite3_file *id); +int sqlite3OsShmUnmap(sqlite3_file *id, int); +#endif /* SQLITE_OMIT_WAL */ +int sqlite3OsFetch(sqlite3_file *id, i64, int, void **); +int sqlite3OsUnfetch(sqlite3_file *, i64, void *); + + +/* +** Functions for accessing sqlite3_vfs methods +*/ +int sqlite3OsOpen(sqlite3_vfs *, const char *, sqlite3_file*, int, int *); +int sqlite3OsDelete(sqlite3_vfs *, const char *, int); +int sqlite3OsAccess(sqlite3_vfs *, const char *, int, int *pResOut); +int sqlite3OsFullPathname(sqlite3_vfs *, const char *, int, char *); +#ifndef SQLITE_OMIT_LOAD_EXTENSION +void *sqlite3OsDlOpen(sqlite3_vfs *, const char *); +void sqlite3OsDlError(sqlite3_vfs *, int, char *); +void (*sqlite3OsDlSym(sqlite3_vfs *, void *, const char *))(void); +void sqlite3OsDlClose(sqlite3_vfs *, void *); +#endif /* SQLITE_OMIT_LOAD_EXTENSION */ +int sqlite3OsRandomness(sqlite3_vfs *, int, char *); +int sqlite3OsSleep(sqlite3_vfs *, int); +int sqlite3OsGetLastError(sqlite3_vfs*); +int sqlite3OsCurrentTimeInt64(sqlite3_vfs *, sqlite3_int64*); + +/* +** Convenience functions for opening and closing files using +** sqlite3_malloc() to obtain space for the file-handle structure. +*/ +int sqlite3OsOpenMalloc(sqlite3_vfs *, const char *, sqlite3_file **, int,int*); +void sqlite3OsCloseFree(sqlite3_file *); + +#endif /* _SQLITE_OS_H_ */ |