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diff --git a/libraries/liblmdb/lmdb.h b/libraries/liblmdb/lmdb.h new file mode 100644 index 0000000..69aa275 --- /dev/null +++ b/libraries/liblmdb/lmdb.h @@ -0,0 +1,1608 @@ +/** @file lmdb.h + * @brief Lightning memory-mapped database library + * + * @mainpage Lightning Memory-Mapped Database Manager (LMDB) + * + * @section intro_sec Introduction + * LMDB is a Btree-based database management library modeled loosely on the + * BerkeleyDB API, but much simplified. The entire database is exposed + * in a memory map, and all data fetches return data directly + * from the mapped memory, so no malloc's or memcpy's occur during + * data fetches. As such, the library is extremely simple because it + * requires no page caching layer of its own, and it is extremely high + * performance and memory-efficient. It is also fully transactional with + * full ACID semantics, and when the memory map is read-only, the + * database integrity cannot be corrupted by stray pointer writes from + * application code. + * + * The library is fully thread-aware and supports concurrent read/write + * access from multiple processes and threads. Data pages use a copy-on- + * write strategy so no active data pages are ever overwritten, which + * also provides resistance to corruption and eliminates the need of any + * special recovery procedures after a system crash. Writes are fully + * serialized; only one write transaction may be active at a time, which + * guarantees that writers can never deadlock. The database structure is + * multi-versioned so readers run with no locks; writers cannot block + * readers, and readers don't block writers. + * + * Unlike other well-known database mechanisms which use either write-ahead + * transaction logs or append-only data writes, LMDB requires no maintenance + * during operation. Both write-ahead loggers and append-only databases + * require periodic checkpointing and/or compaction of their log or database + * files otherwise they grow without bound. LMDB tracks free pages within + * the database and re-uses them for new write operations, so the database + * size does not grow without bound in normal use. + * + * The memory map can be used as a read-only or read-write map. It is + * read-only by default as this provides total immunity to corruption. + * Using read-write mode offers much higher write performance, but adds + * the possibility for stray application writes thru pointers to silently + * corrupt the database. Of course if your application code is known to + * be bug-free (...) then this is not an issue. + * + * If this is your first time using a transactional embedded key/value + * store, you may find the \ref starting page to be helpful. + * + * @section caveats_sec Caveats + * Troubleshooting the lock file, plus semaphores on BSD systems: + * + * - A broken lockfile can cause sync issues. + * Stale reader transactions left behind by an aborted program + * cause further writes to grow the database quickly, and + * stale locks can block further operation. + * + * Fix: Check for stale readers periodically, using the + * #mdb_reader_check function or the \ref mdb_stat_1 "mdb_stat" tool. + * Stale writers will be cleared automatically on some systems: + * - Windows - automatic + * - Linux, systems using POSIX mutexes with Robust option - automatic + * - not on BSD, systems using POSIX semaphores. + * Otherwise just make all programs using the database close it; + * the lockfile is always reset on first open of the environment. + * + * - On BSD systems or others configured with MDB_USE_POSIX_SEM, + * startup can fail due to semaphores owned by another userid. + * + * Fix: Open and close the database as the user which owns the + * semaphores (likely last user) or as root, while no other + * process is using the database. + * + * Restrictions/caveats (in addition to those listed for some functions): + * + * - Only the database owner should normally use the database on + * BSD systems or when otherwise configured with MDB_USE_POSIX_SEM. + * Multiple users can cause startup to fail later, as noted above. + * + * - There is normally no pure read-only mode, since readers need write + * access to locks and lock file. Exceptions: On read-only filesystems + * or with the #MDB_NOLOCK flag described under #mdb_env_open(). + * + * - An LMDB configuration will often reserve considerable \b unused + * memory address space and maybe file size for future growth. + * This does not use actual memory or disk space, but users may need + * to understand the difference so they won't be scared off. + * + * - By default, in versions before 0.9.10, unused portions of the data + * file might receive garbage data from memory freed by other code. + * (This does not happen when using the #MDB_WRITEMAP flag.) As of + * 0.9.10 the default behavior is to initialize such memory before + * writing to the data file. Since there may be a slight performance + * cost due to this initialization, applications may disable it using + * the #MDB_NOMEMINIT flag. Applications handling sensitive data + * which must not be written should not use this flag. This flag is + * irrelevant when using #MDB_WRITEMAP. + * + * - A thread can only use one transaction at a time, plus any child + * transactions. Each transaction belongs to one thread. See below. + * The #MDB_NOTLS flag changes this for read-only transactions. + * + * - Use an MDB_env* in the process which opened it, not after fork(). + * + * - Do not have open an LMDB database twice in the same process at + * the same time. Not even from a plain open() call - close()ing it + * breaks fcntl() advisory locking. (It is OK to reopen it after + * fork() - exec*(), since the lockfile has FD_CLOEXEC set.) + * + * - Avoid long-lived transactions. Read transactions prevent + * reuse of pages freed by newer write transactions, thus the + * database can grow quickly. Write transactions prevent + * other write transactions, since writes are serialized. + * + * - Avoid suspending a process with active transactions. These + * would then be "long-lived" as above. Also read transactions + * suspended when writers commit could sometimes see wrong data. + * + * ...when several processes can use a database concurrently: + * + * - Avoid aborting a process with an active transaction. + * The transaction becomes "long-lived" as above until a check + * for stale readers is performed or the lockfile is reset, + * since the process may not remove it from the lockfile. + * + * This does not apply to write transactions if the system clears + * stale writers, see above. + * + * - If you do that anyway, do a periodic check for stale readers. Or + * close the environment once in a while, so the lockfile can get reset. + * + * - Do not use LMDB databases on remote filesystems, even between + * processes on the same host. This breaks flock() on some OSes, + * possibly memory map sync, and certainly sync between programs + * on different hosts. + * + * - Opening a database can fail if another process is opening or + * closing it at exactly the same time. + * + * @author Howard Chu, Symas Corporation. + * + * @copyright Copyright 2011-2021 Howard Chu, Symas Corp. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted only as authorized by the OpenLDAP + * Public License. + * + * A copy of this license is available in the file LICENSE in the + * top-level directory of the distribution or, alternatively, at + * <http://www.OpenLDAP.org/license.html>. + * + * @par Derived From: + * This code is derived from btree.c written by Martin Hedenfalk. + * + * Copyright (c) 2009, 2010 Martin Hedenfalk <martin@bzero.se> + * + * Permission to use, copy, modify, and distribute this software for any + * purpose with or without fee is hereby granted, provided that the above + * copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES + * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR + * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES + * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN + * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF + * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. + */ +#ifndef _LMDB_H_ +#define _LMDB_H_ + +#include <sys/types.h> + +#ifdef __cplusplus +extern "C" { +#endif + +/** Unix permissions for creating files, or dummy definition for Windows */ +#ifdef _MSC_VER +typedef int mdb_mode_t; +#else +typedef mode_t mdb_mode_t; +#endif + +/** An abstraction for a file handle. + * On POSIX systems file handles are small integers. On Windows + * they're opaque pointers. + */ +#ifdef _WIN32 +typedef void *mdb_filehandle_t; +#else +typedef int mdb_filehandle_t; +#endif + +/** @defgroup mdb LMDB API + * @{ + * @brief OpenLDAP Lightning Memory-Mapped Database Manager + */ +/** @defgroup Version Version Macros + * @{ + */ +/** Library major version */ +#define MDB_VERSION_MAJOR 0 +/** Library minor version */ +#define MDB_VERSION_MINOR 9 +/** Library patch version */ +#define MDB_VERSION_PATCH 29 + +/** Combine args a,b,c into a single integer for easy version comparisons */ +#define MDB_VERINT(a,b,c) (((a) << 24) | ((b) << 16) | (c)) + +/** The full library version as a single integer */ +#define MDB_VERSION_FULL \ + MDB_VERINT(MDB_VERSION_MAJOR,MDB_VERSION_MINOR,MDB_VERSION_PATCH) + +/** The release date of this library version */ +#define MDB_VERSION_DATE "March 16, 2021" + +/** A stringifier for the version info */ +#define MDB_VERSTR(a,b,c,d) "LMDB " #a "." #b "." #c ": (" d ")" + +/** A helper for the stringifier macro */ +#define MDB_VERFOO(a,b,c,d) MDB_VERSTR(a,b,c,d) + +/** The full library version as a C string */ +#define MDB_VERSION_STRING \ + MDB_VERFOO(MDB_VERSION_MAJOR,MDB_VERSION_MINOR,MDB_VERSION_PATCH,MDB_VERSION_DATE) +/** @} */ + +/** @brief Opaque structure for a database environment. + * + * A DB environment supports multiple databases, all residing in the same + * shared-memory map. + */ +typedef struct MDB_env MDB_env; + +/** @brief Opaque structure for a transaction handle. + * + * All database operations require a transaction handle. Transactions may be + * read-only or read-write. + */ +typedef struct MDB_txn MDB_txn; + +/** @brief A handle for an individual database in the DB environment. */ +typedef unsigned int MDB_dbi; + +/** @brief Opaque structure for navigating through a database */ +typedef struct MDB_cursor MDB_cursor; + +/** @brief Generic structure used for passing keys and data in and out + * of the database. + * + * Values returned from the database are valid only until a subsequent + * update operation, or the end of the transaction. Do not modify or + * free them, they commonly point into the database itself. + * + * Key sizes must be between 1 and #mdb_env_get_maxkeysize() inclusive. + * The same applies to data sizes in databases with the #MDB_DUPSORT flag. + * Other data items can in theory be from 0 to 0xffffffff bytes long. + */ +typedef struct MDB_val { + size_t mv_size; /**< size of the data item */ + void *mv_data; /**< address of the data item */ +} MDB_val; + +/** @brief A callback function used to compare two keys in a database */ +typedef int (MDB_cmp_func)(const MDB_val *a, const MDB_val *b); + +/** @brief A callback function used to relocate a position-dependent data item + * in a fixed-address database. + * + * The \b newptr gives the item's desired address in + * the memory map, and \b oldptr gives its previous address. The item's actual + * data resides at the address in \b item. This callback is expected to walk + * through the fields of the record in \b item and modify any + * values based at the \b oldptr address to be relative to the \b newptr address. + * @param[in,out] item The item that is to be relocated. + * @param[in] oldptr The previous address. + * @param[in] newptr The new address to relocate to. + * @param[in] relctx An application-provided context, set by #mdb_set_relctx(). + * @todo This feature is currently unimplemented. + */ +typedef void (MDB_rel_func)(MDB_val *item, void *oldptr, void *newptr, void *relctx); + +/** @defgroup mdb_env Environment Flags + * @{ + */ + /** mmap at a fixed address (experimental) */ +#define MDB_FIXEDMAP 0x01 + /** no environment directory */ +#define MDB_NOSUBDIR 0x4000 + /** don't fsync after commit */ +#define MDB_NOSYNC 0x10000 + /** read only */ +#define MDB_RDONLY 0x20000 + /** don't fsync metapage after commit */ +#define MDB_NOMETASYNC 0x40000 + /** use writable mmap */ +#define MDB_WRITEMAP 0x80000 + /** use asynchronous msync when #MDB_WRITEMAP is used */ +#define MDB_MAPASYNC 0x100000 + /** tie reader locktable slots to #MDB_txn objects instead of to threads */ +#define MDB_NOTLS 0x200000 + /** don't do any locking, caller must manage their own locks */ +#define MDB_NOLOCK 0x400000 + /** don't do readahead (no effect on Windows) */ +#define MDB_NORDAHEAD 0x800000 + /** don't initialize malloc'd memory before writing to datafile */ +#define MDB_NOMEMINIT 0x1000000 +/** @} */ + +/** @defgroup mdb_dbi_open Database Flags + * @{ + */ + /** use reverse string keys */ +#define MDB_REVERSEKEY 0x02 + /** use sorted duplicates */ +#define MDB_DUPSORT 0x04 + /** numeric keys in native byte order: either unsigned int or size_t. + * The keys must all be of the same size. */ +#define MDB_INTEGERKEY 0x08 + /** with #MDB_DUPSORT, sorted dup items have fixed size */ +#define MDB_DUPFIXED 0x10 + /** with #MDB_DUPSORT, dups are #MDB_INTEGERKEY-style integers */ +#define MDB_INTEGERDUP 0x20 + /** with #MDB_DUPSORT, use reverse string dups */ +#define MDB_REVERSEDUP 0x40 + /** create DB if not already existing */ +#define MDB_CREATE 0x40000 +/** @} */ + +/** @defgroup mdb_put Write Flags + * @{ + */ +/** For put: Don't write if the key already exists. */ +#define MDB_NOOVERWRITE 0x10 +/** Only for #MDB_DUPSORT<br> + * For put: don't write if the key and data pair already exist.<br> + * For mdb_cursor_del: remove all duplicate data items. + */ +#define MDB_NODUPDATA 0x20 +/** For mdb_cursor_put: overwrite the current key/data pair */ +#define MDB_CURRENT 0x40 +/** For put: Just reserve space for data, don't copy it. Return a + * pointer to the reserved space. + */ +#define MDB_RESERVE 0x10000 +/** Data is being appended, don't split full pages. */ +#define MDB_APPEND 0x20000 +/** Duplicate data is being appended, don't split full pages. */ +#define MDB_APPENDDUP 0x40000 +/** Store multiple data items in one call. Only for #MDB_DUPFIXED. */ +#define MDB_MULTIPLE 0x80000 +/* @} */ + +/** @defgroup mdb_copy Copy Flags + * @{ + */ +/** Compacting copy: Omit free space from copy, and renumber all + * pages sequentially. + */ +#define MDB_CP_COMPACT 0x01 +/* @} */ + +/** @brief Cursor Get operations. + * + * This is the set of all operations for retrieving data + * using a cursor. + */ +typedef enum MDB_cursor_op { + MDB_FIRST, /**< Position at first key/data item */ + MDB_FIRST_DUP, /**< Position at first data item of current key. + Only for #MDB_DUPSORT */ + MDB_GET_BOTH, /**< Position at key/data pair. Only for #MDB_DUPSORT */ + MDB_GET_BOTH_RANGE, /**< position at key, nearest data. Only for #MDB_DUPSORT */ + MDB_GET_CURRENT, /**< Return key/data at current cursor position */ + MDB_GET_MULTIPLE, /**< Return up to a page of duplicate data items + from current cursor position. Move cursor to prepare + for #MDB_NEXT_MULTIPLE. Only for #MDB_DUPFIXED */ + MDB_LAST, /**< Position at last key/data item */ + MDB_LAST_DUP, /**< Position at last data item of current key. + Only for #MDB_DUPSORT */ + MDB_NEXT, /**< Position at next data item */ + MDB_NEXT_DUP, /**< Position at next data item of current key. + Only for #MDB_DUPSORT */ + MDB_NEXT_MULTIPLE, /**< Return up to a page of duplicate data items + from next cursor position. Move cursor to prepare + for #MDB_NEXT_MULTIPLE. Only for #MDB_DUPFIXED */ + MDB_NEXT_NODUP, /**< Position at first data item of next key */ + MDB_PREV, /**< Position at previous data item */ + MDB_PREV_DUP, /**< Position at previous data item of current key. + Only for #MDB_DUPSORT */ + MDB_PREV_NODUP, /**< Position at last data item of previous key */ + MDB_SET, /**< Position at specified key */ + MDB_SET_KEY, /**< Position at specified key, return key + data */ + MDB_SET_RANGE, /**< Position at first key greater than or equal to specified key. */ + MDB_PREV_MULTIPLE /**< Position at previous page and return up to + a page of duplicate data items. Only for #MDB_DUPFIXED */ +} MDB_cursor_op; + +/** @defgroup errors Return Codes + * + * BerkeleyDB uses -30800 to -30999, we'll go under them + * @{ + */ + /** Successful result */ +#define MDB_SUCCESS 0 + /** key/data pair already exists */ +#define MDB_KEYEXIST (-30799) + /** key/data pair not found (EOF) */ +#define MDB_NOTFOUND (-30798) + /** Requested page not found - this usually indicates corruption */ +#define MDB_PAGE_NOTFOUND (-30797) + /** Located page was wrong type */ +#define MDB_CORRUPTED (-30796) + /** Update of meta page failed or environment had fatal error */ +#define MDB_PANIC (-30795) + /** Environment version mismatch */ +#define MDB_VERSION_MISMATCH (-30794) + /** File is not a valid LMDB file */ +#define MDB_INVALID (-30793) + /** Environment mapsize reached */ +#define MDB_MAP_FULL (-30792) + /** Environment maxdbs reached */ +#define MDB_DBS_FULL (-30791) + /** Environment maxreaders reached */ +#define MDB_READERS_FULL (-30790) + /** Too many TLS keys in use - Windows only */ +#define MDB_TLS_FULL (-30789) + /** Txn has too many dirty pages */ +#define MDB_TXN_FULL (-30788) + /** Cursor stack too deep - internal error */ +#define MDB_CURSOR_FULL (-30787) + /** Page has not enough space - internal error */ +#define MDB_PAGE_FULL (-30786) + /** Database contents grew beyond environment mapsize */ +#define MDB_MAP_RESIZED (-30785) + /** Operation and DB incompatible, or DB type changed. This can mean: + * <ul> + * <li>The operation expects an #MDB_DUPSORT / #MDB_DUPFIXED database. + * <li>Opening a named DB when the unnamed DB has #MDB_DUPSORT / #MDB_INTEGERKEY. + * <li>Accessing a data record as a database, or vice versa. + * <li>The database was dropped and recreated with different flags. + * </ul> + */ +#define MDB_INCOMPATIBLE (-30784) + /** Invalid reuse of reader locktable slot */ +#define MDB_BAD_RSLOT (-30783) + /** Transaction must abort, has a child, or is invalid */ +#define MDB_BAD_TXN (-30782) + /** Unsupported size of key/DB name/data, or wrong DUPFIXED size */ +#define MDB_BAD_VALSIZE (-30781) + /** The specified DBI was changed unexpectedly */ +#define MDB_BAD_DBI (-30780) + /** The last defined error code */ +#define MDB_LAST_ERRCODE MDB_BAD_DBI +/** @} */ + +/** @brief Statistics for a database in the environment */ +typedef struct MDB_stat { + unsigned int ms_psize; /**< Size of a database page. + This is currently the same for all databases. */ + unsigned int ms_depth; /**< Depth (height) of the B-tree */ + size_t ms_branch_pages; /**< Number of internal (non-leaf) pages */ + size_t ms_leaf_pages; /**< Number of leaf pages */ + size_t ms_overflow_pages; /**< Number of overflow pages */ + size_t ms_entries; /**< Number of data items */ +} MDB_stat; + +/** @brief Information about the environment */ +typedef struct MDB_envinfo { + void *me_mapaddr; /**< Address of map, if fixed */ + size_t me_mapsize; /**< Size of the data memory map */ + size_t me_last_pgno; /**< ID of the last used page */ + size_t me_last_txnid; /**< ID of the last committed transaction */ + unsigned int me_maxreaders; /**< max reader slots in the environment */ + unsigned int me_numreaders; /**< max reader slots used in the environment */ +} MDB_envinfo; + + /** @brief Return the LMDB library version information. + * + * @param[out] major if non-NULL, the library major version number is copied here + * @param[out] minor if non-NULL, the library minor version number is copied here + * @param[out] patch if non-NULL, the library patch version number is copied here + * @retval "version string" The library version as a string + */ +char *mdb_version(int *major, int *minor, int *patch); + + /** @brief Return a string describing a given error code. + * + * This function is a superset of the ANSI C X3.159-1989 (ANSI C) strerror(3) + * function. If the error code is greater than or equal to 0, then the string + * returned by the system function strerror(3) is returned. If the error code + * is less than 0, an error string corresponding to the LMDB library error is + * returned. See @ref errors for a list of LMDB-specific error codes. + * @param[in] err The error code + * @retval "error message" The description of the error + */ +char *mdb_strerror(int err); + + /** @brief Create an LMDB environment handle. + * + * This function allocates memory for a #MDB_env structure. To release + * the allocated memory and discard the handle, call #mdb_env_close(). + * Before the handle may be used, it must be opened using #mdb_env_open(). + * Various other options may also need to be set before opening the handle, + * e.g. #mdb_env_set_mapsize(), #mdb_env_set_maxreaders(), #mdb_env_set_maxdbs(), + * depending on usage requirements. + * @param[out] env The address where the new handle will be stored + * @return A non-zero error value on failure and 0 on success. + */ +int mdb_env_create(MDB_env **env); + + /** @brief Open an environment handle. + * + * If this function fails, #mdb_env_close() must be called to discard the #MDB_env handle. + * @param[in] env An environment handle returned by #mdb_env_create() + * @param[in] path The directory in which the database files reside. This + * directory must already exist and be writable. + * @param[in] flags Special options for this environment. This parameter + * must be set to 0 or by bitwise OR'ing together one or more of the + * values described here. + * Flags set by mdb_env_set_flags() are also used. + * <ul> + * <li>#MDB_FIXEDMAP + * use a fixed address for the mmap region. This flag must be specified + * when creating the environment, and is stored persistently in the environment. + * If successful, the memory map will always reside at the same virtual address + * and pointers used to reference data items in the database will be constant + * across multiple invocations. This option may not always work, depending on + * how the operating system has allocated memory to shared libraries and other uses. + * The feature is highly experimental. + * <li>#MDB_NOSUBDIR + * By default, LMDB creates its environment in a directory whose + * pathname is given in \b path, and creates its data and lock files + * under that directory. With this option, \b path is used as-is for + * the database main data file. The database lock file is the \b path + * with "-lock" appended. + * <li>#MDB_RDONLY + * Open the environment in read-only mode. No write operations will be + * allowed. LMDB will still modify the lock file - except on read-only + * filesystems, where LMDB does not use locks. + * <li>#MDB_WRITEMAP + * Use a writeable memory map unless MDB_RDONLY is set. This uses + * fewer mallocs but loses protection from application bugs + * like wild pointer writes and other bad updates into the database. + * This may be slightly faster for DBs that fit entirely in RAM, but + * is slower for DBs larger than RAM. + * Incompatible with nested transactions. + * Do not mix processes with and without MDB_WRITEMAP on the same + * environment. This can defeat durability (#mdb_env_sync etc). + * <li>#MDB_NOMETASYNC + * Flush system buffers to disk only once per transaction, omit the + * metadata flush. Defer that until the system flushes files to disk, + * or next non-MDB_RDONLY commit or #mdb_env_sync(). This optimization + * maintains database integrity, but a system crash may undo the last + * committed transaction. I.e. it preserves the ACI (atomicity, + * consistency, isolation) but not D (durability) database property. + * This flag may be changed at any time using #mdb_env_set_flags(). + * <li>#MDB_NOSYNC + * Don't flush system buffers to disk when committing a transaction. + * This optimization means a system crash can corrupt the database or + * lose the last transactions if buffers are not yet flushed to disk. + * The risk is governed by how often the system flushes dirty buffers + * to disk and how often #mdb_env_sync() is called. However, if the + * filesystem preserves write order and the #MDB_WRITEMAP flag is not + * used, transactions exhibit ACI (atomicity, consistency, isolation) + * properties and only lose D (durability). I.e. database integrity + * is maintained, but a system crash may undo the final transactions. + * Note that (#MDB_NOSYNC | #MDB_WRITEMAP) leaves the system with no + * hint for when to write transactions to disk, unless #mdb_env_sync() + * is called. (#MDB_MAPASYNC | #MDB_WRITEMAP) may be preferable. + * This flag may be changed at any time using #mdb_env_set_flags(). + * <li>#MDB_MAPASYNC + * When using #MDB_WRITEMAP, use asynchronous flushes to disk. + * As with #MDB_NOSYNC, a system crash can then corrupt the + * database or lose the last transactions. Calling #mdb_env_sync() + * ensures on-disk database integrity until next commit. + * This flag may be changed at any time using #mdb_env_set_flags(). + * <li>#MDB_NOTLS + * Don't use Thread-Local Storage. Tie reader locktable slots to + * #MDB_txn objects instead of to threads. I.e. #mdb_txn_reset() keeps + * the slot reserved for the #MDB_txn object. A thread may use parallel + * read-only transactions. A read-only transaction may span threads if + * the user synchronizes its use. Applications that multiplex many + * user threads over individual OS threads need this option. Such an + * application must also serialize the write transactions in an OS + * thread, since LMDB's write locking is unaware of the user threads. + * <li>#MDB_NOLOCK + * Don't do any locking. If concurrent access is anticipated, the + * caller must manage all concurrency itself. For proper operation + * the caller must enforce single-writer semantics, and must ensure + * that no readers are using old transactions while a writer is + * active. The simplest approach is to use an exclusive lock so that + * no readers may be active at all when a writer begins. + * <li>#MDB_NORDAHEAD + * Turn off readahead. Most operating systems perform readahead on + * read requests by default. This option turns it off if the OS + * supports it. Turning it off may help random read performance + * when the DB is larger than RAM and system RAM is full. + * The option is not implemented on Windows. + * <li>#MDB_NOMEMINIT + * Don't initialize malloc'd memory before writing to unused spaces + * in the data file. By default, memory for pages written to the data + * file is obtained using malloc. While these pages may be reused in + * subsequent transactions, freshly malloc'd pages will be initialized + * to zeroes before use. This avoids persisting leftover data from other + * code (that used the heap and subsequently freed the memory) into the + * data file. Note that many other system libraries may allocate + * and free memory from the heap for arbitrary uses. E.g., stdio may + * use the heap for file I/O buffers. This initialization step has a + * modest performance cost so some applications may want to disable + * it using this flag. This option can be a problem for applications + * which handle sensitive data like passwords, and it makes memory + * checkers like Valgrind noisy. This flag is not needed with #MDB_WRITEMAP, + * which writes directly to the mmap instead of using malloc for pages. The + * initialization is also skipped if #MDB_RESERVE is used; the + * caller is expected to overwrite all of the memory that was + * reserved in that case. + * This flag may be changed at any time using #mdb_env_set_flags(). + * </ul> + * @param[in] mode The UNIX permissions to set on created files and semaphores. + * This parameter is ignored on Windows. + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>#MDB_VERSION_MISMATCH - the version of the LMDB library doesn't match the + * version that created the database environment. + * <li>#MDB_INVALID - the environment file headers are corrupted. + * <li>ENOENT - the directory specified by the path parameter doesn't exist. + * <li>EACCES - the user didn't have permission to access the environment files. + * <li>EAGAIN - the environment was locked by another process. + * </ul> + */ +int mdb_env_open(MDB_env *env, const char *path, unsigned int flags, mdb_mode_t mode); + + /** @brief Copy an LMDB environment to the specified path. + * + * This function may be used to make a backup of an existing environment. + * No lockfile is created, since it gets recreated at need. + * @note This call can trigger significant file size growth if run in + * parallel with write transactions, because it employs a read-only + * transaction. See long-lived transactions under @ref caveats_sec. + * @param[in] env An environment handle returned by #mdb_env_create(). It + * must have already been opened successfully. + * @param[in] path The directory in which the copy will reside. This + * directory must already exist and be writable but must otherwise be + * empty. + * @return A non-zero error value on failure and 0 on success. + */ +int mdb_env_copy(MDB_env *env, const char *path); + + /** @brief Copy an LMDB environment to the specified file descriptor. + * + * This function may be used to make a backup of an existing environment. + * No lockfile is created, since it gets recreated at need. + * @note This call can trigger significant file size growth if run in + * parallel with write transactions, because it employs a read-only + * transaction. See long-lived transactions under @ref caveats_sec. + * @param[in] env An environment handle returned by #mdb_env_create(). It + * must have already been opened successfully. + * @param[in] fd The filedescriptor to write the copy to. It must + * have already been opened for Write access. + * @return A non-zero error value on failure and 0 on success. + */ +int mdb_env_copyfd(MDB_env *env, mdb_filehandle_t fd); + + /** @brief Copy an LMDB environment to the specified path, with options. + * + * This function may be used to make a backup of an existing environment. + * No lockfile is created, since it gets recreated at need. + * @note This call can trigger significant file size growth if run in + * parallel with write transactions, because it employs a read-only + * transaction. See long-lived transactions under @ref caveats_sec. + * @param[in] env An environment handle returned by #mdb_env_create(). It + * must have already been opened successfully. + * @param[in] path The directory in which the copy will reside. This + * directory must already exist and be writable but must otherwise be + * empty. + * @param[in] flags Special options for this operation. This parameter + * must be set to 0 or by bitwise OR'ing together one or more of the + * values described here. + * <ul> + * <li>#MDB_CP_COMPACT - Perform compaction while copying: omit free + * pages and sequentially renumber all pages in output. This option + * consumes more CPU and runs more slowly than the default. + * Currently it fails if the environment has suffered a page leak. + * </ul> + * @return A non-zero error value on failure and 0 on success. + */ +int mdb_env_copy2(MDB_env *env, const char *path, unsigned int flags); + + /** @brief Copy an LMDB environment to the specified file descriptor, + * with options. + * + * This function may be used to make a backup of an existing environment. + * No lockfile is created, since it gets recreated at need. See + * #mdb_env_copy2() for further details. + * @note This call can trigger significant file size growth if run in + * parallel with write transactions, because it employs a read-only + * transaction. See long-lived transactions under @ref caveats_sec. + * @param[in] env An environment handle returned by #mdb_env_create(). It + * must have already been opened successfully. + * @param[in] fd The filedescriptor to write the copy to. It must + * have already been opened for Write access. + * @param[in] flags Special options for this operation. + * See #mdb_env_copy2() for options. + * @return A non-zero error value on failure and 0 on success. + */ +int mdb_env_copyfd2(MDB_env *env, mdb_filehandle_t fd, unsigned int flags); + + /** @brief Return statistics about the LMDB environment. + * + * @param[in] env An environment handle returned by #mdb_env_create() + * @param[out] stat The address of an #MDB_stat structure + * where the statistics will be copied + */ +int mdb_env_stat(MDB_env *env, MDB_stat *stat); + + /** @brief Return information about the LMDB environment. + * + * @param[in] env An environment handle returned by #mdb_env_create() + * @param[out] stat The address of an #MDB_envinfo structure + * where the information will be copied + */ +int mdb_env_info(MDB_env *env, MDB_envinfo *stat); + + /** @brief Flush the data buffers to disk. + * + * Data is always written to disk when #mdb_txn_commit() is called, + * but the operating system may keep it buffered. LMDB always flushes + * the OS buffers upon commit as well, unless the environment was + * opened with #MDB_NOSYNC or in part #MDB_NOMETASYNC. This call is + * not valid if the environment was opened with #MDB_RDONLY. + * @param[in] env An environment handle returned by #mdb_env_create() + * @param[in] force If non-zero, force a synchronous flush. Otherwise + * if the environment has the #MDB_NOSYNC flag set the flushes + * will be omitted, and with #MDB_MAPASYNC they will be asynchronous. + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>EACCES - the environment is read-only. + * <li>EINVAL - an invalid parameter was specified. + * <li>EIO - an error occurred during synchronization. + * </ul> + */ +int mdb_env_sync(MDB_env *env, int force); + + /** @brief Close the environment and release the memory map. + * + * Only a single thread may call this function. All transactions, databases, + * and cursors must already be closed before calling this function. Attempts to + * use any such handles after calling this function will cause a SIGSEGV. + * The environment handle will be freed and must not be used again after this call. + * @param[in] env An environment handle returned by #mdb_env_create() + */ +void mdb_env_close(MDB_env *env); + + /** @brief Set environment flags. + * + * This may be used to set some flags in addition to those from + * #mdb_env_open(), or to unset these flags. If several threads + * change the flags at the same time, the result is undefined. + * @param[in] env An environment handle returned by #mdb_env_create() + * @param[in] flags The flags to change, bitwise OR'ed together + * @param[in] onoff A non-zero value sets the flags, zero clears them. + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>EINVAL - an invalid parameter was specified. + * </ul> + */ +int mdb_env_set_flags(MDB_env *env, unsigned int flags, int onoff); + + /** @brief Get environment flags. + * + * @param[in] env An environment handle returned by #mdb_env_create() + * @param[out] flags The address of an integer to store the flags + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>EINVAL - an invalid parameter was specified. + * </ul> + */ +int mdb_env_get_flags(MDB_env *env, unsigned int *flags); + + /** @brief Return the path that was used in #mdb_env_open(). + * + * @param[in] env An environment handle returned by #mdb_env_create() + * @param[out] path Address of a string pointer to contain the path. This + * is the actual string in the environment, not a copy. It should not be + * altered in any way. + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>EINVAL - an invalid parameter was specified. + * </ul> + */ +int mdb_env_get_path(MDB_env *env, const char **path); + + /** @brief Return the filedescriptor for the given environment. + * + * This function may be called after fork(), so the descriptor can be + * closed before exec*(). Other LMDB file descriptors have FD_CLOEXEC. + * (Until LMDB 0.9.18, only the lockfile had that.) + * + * @param[in] env An environment handle returned by #mdb_env_create() + * @param[out] fd Address of a mdb_filehandle_t to contain the descriptor. + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>EINVAL - an invalid parameter was specified. + * </ul> + */ +int mdb_env_get_fd(MDB_env *env, mdb_filehandle_t *fd); + + /** @brief Set the size of the memory map to use for this environment. + * + * The size should be a multiple of the OS page size. The default is + * 10485760 bytes. The size of the memory map is also the maximum size + * of the database. The value should be chosen as large as possible, + * to accommodate future growth of the database. + * This function should be called after #mdb_env_create() and before #mdb_env_open(). + * It may be called at later times if no transactions are active in + * this process. Note that the library does not check for this condition, + * the caller must ensure it explicitly. + * + * The new size takes effect immediately for the current process but + * will not be persisted to any others until a write transaction has been + * committed by the current process. Also, only mapsize increases are + * persisted into the environment. + * + * If the mapsize is increased by another process, and data has grown + * beyond the range of the current mapsize, #mdb_txn_begin() will + * return #MDB_MAP_RESIZED. This function may be called with a size + * of zero to adopt the new size. + * + * Any attempt to set a size smaller than the space already consumed + * by the environment will be silently changed to the current size of the used space. + * @param[in] env An environment handle returned by #mdb_env_create() + * @param[in] size The size in bytes + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>EINVAL - an invalid parameter was specified, or the environment has + * an active write transaction. + * </ul> + */ +int mdb_env_set_mapsize(MDB_env *env, size_t size); + + /** @brief Set the maximum number of threads/reader slots for the environment. + * + * This defines the number of slots in the lock table that is used to track readers in the + * the environment. The default is 126. + * Starting a read-only transaction normally ties a lock table slot to the + * current thread until the environment closes or the thread exits. If + * MDB_NOTLS is in use, #mdb_txn_begin() instead ties the slot to the + * MDB_txn object until it or the #MDB_env object is destroyed. + * This function may only be called after #mdb_env_create() and before #mdb_env_open(). + * @param[in] env An environment handle returned by #mdb_env_create() + * @param[in] readers The maximum number of reader lock table slots + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>EINVAL - an invalid parameter was specified, or the environment is already open. + * </ul> + */ +int mdb_env_set_maxreaders(MDB_env *env, unsigned int readers); + + /** @brief Get the maximum number of threads/reader slots for the environment. + * + * @param[in] env An environment handle returned by #mdb_env_create() + * @param[out] readers Address of an integer to store the number of readers + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>EINVAL - an invalid parameter was specified. + * </ul> + */ +int mdb_env_get_maxreaders(MDB_env *env, unsigned int *readers); + + /** @brief Set the maximum number of named databases for the environment. + * + * This function is only needed if multiple databases will be used in the + * environment. Simpler applications that use the environment as a single + * unnamed database can ignore this option. + * This function may only be called after #mdb_env_create() and before #mdb_env_open(). + * + * Currently a moderate number of slots are cheap but a huge number gets + * expensive: 7-120 words per transaction, and every #mdb_dbi_open() + * does a linear search of the opened slots. + * @param[in] env An environment handle returned by #mdb_env_create() + * @param[in] dbs The maximum number of databases + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>EINVAL - an invalid parameter was specified, or the environment is already open. + * </ul> + */ +int mdb_env_set_maxdbs(MDB_env *env, MDB_dbi dbs); + + /** @brief Get the maximum size of keys and #MDB_DUPSORT data we can write. + * + * Depends on the compile-time constant #MDB_MAXKEYSIZE. Default 511. + * See @ref MDB_val. + * @param[in] env An environment handle returned by #mdb_env_create() + * @return The maximum size of a key we can write + */ +int mdb_env_get_maxkeysize(MDB_env *env); + + /** @brief Set application information associated with the #MDB_env. + * + * @param[in] env An environment handle returned by #mdb_env_create() + * @param[in] ctx An arbitrary pointer for whatever the application needs. + * @return A non-zero error value on failure and 0 on success. + */ +int mdb_env_set_userctx(MDB_env *env, void *ctx); + + /** @brief Get the application information associated with the #MDB_env. + * + * @param[in] env An environment handle returned by #mdb_env_create() + * @return The pointer set by #mdb_env_set_userctx(). + */ +void *mdb_env_get_userctx(MDB_env *env); + + /** @brief A callback function for most LMDB assert() failures, + * called before printing the message and aborting. + * + * @param[in] env An environment handle returned by #mdb_env_create(). + * @param[in] msg The assertion message, not including newline. + */ +typedef void MDB_assert_func(MDB_env *env, const char *msg); + + /** Set or reset the assert() callback of the environment. + * Disabled if liblmdb is built with NDEBUG. + * @note This hack should become obsolete as lmdb's error handling matures. + * @param[in] env An environment handle returned by #mdb_env_create(). + * @param[in] func An #MDB_assert_func function, or 0. + * @return A non-zero error value on failure and 0 on success. + */ +int mdb_env_set_assert(MDB_env *env, MDB_assert_func *func); + + /** @brief Create a transaction for use with the environment. + * + * The transaction handle may be discarded using #mdb_txn_abort() or #mdb_txn_commit(). + * @note A transaction and its cursors must only be used by a single + * thread, and a thread may only have a single transaction at a time. + * If #MDB_NOTLS is in use, this does not apply to read-only transactions. + * @note Cursors may not span transactions. + * @param[in] env An environment handle returned by #mdb_env_create() + * @param[in] parent If this parameter is non-NULL, the new transaction + * will be a nested transaction, with the transaction indicated by \b parent + * as its parent. Transactions may be nested to any level. A parent + * transaction and its cursors may not issue any other operations than + * mdb_txn_commit and mdb_txn_abort while it has active child transactions. + * @param[in] flags Special options for this transaction. This parameter + * must be set to 0 or by bitwise OR'ing together one or more of the + * values described here. + * <ul> + * <li>#MDB_RDONLY + * This transaction will not perform any write operations. + * </ul> + * @param[out] txn Address where the new #MDB_txn handle will be stored + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>#MDB_PANIC - a fatal error occurred earlier and the environment + * must be shut down. + * <li>#MDB_MAP_RESIZED - another process wrote data beyond this MDB_env's + * mapsize and this environment's map must be resized as well. + * See #mdb_env_set_mapsize(). + * <li>#MDB_READERS_FULL - a read-only transaction was requested and + * the reader lock table is full. See #mdb_env_set_maxreaders(). + * <li>ENOMEM - out of memory. + * </ul> + */ +int mdb_txn_begin(MDB_env *env, MDB_txn *parent, unsigned int flags, MDB_txn **txn); + + /** @brief Returns the transaction's #MDB_env + * + * @param[in] txn A transaction handle returned by #mdb_txn_begin() + */ +MDB_env *mdb_txn_env(MDB_txn *txn); + + /** @brief Return the transaction's ID. + * + * This returns the identifier associated with this transaction. For a + * read-only transaction, this corresponds to the snapshot being read; + * concurrent readers will frequently have the same transaction ID. + * + * @param[in] txn A transaction handle returned by #mdb_txn_begin() + * @return A transaction ID, valid if input is an active transaction. + */ +size_t mdb_txn_id(MDB_txn *txn); + + /** @brief Commit all the operations of a transaction into the database. + * + * The transaction handle is freed. It and its cursors must not be used + * again after this call, except with #mdb_cursor_renew(). + * @note Earlier documentation incorrectly said all cursors would be freed. + * Only write-transactions free cursors. + * @param[in] txn A transaction handle returned by #mdb_txn_begin() + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>EINVAL - an invalid parameter was specified. + * <li>ENOSPC - no more disk space. + * <li>EIO - a low-level I/O error occurred while writing. + * <li>ENOMEM - out of memory. + * </ul> + */ +int mdb_txn_commit(MDB_txn *txn); + + /** @brief Abandon all the operations of the transaction instead of saving them. + * + * The transaction handle is freed. It and its cursors must not be used + * again after this call, except with #mdb_cursor_renew(). + * @note Earlier documentation incorrectly said all cursors would be freed. + * Only write-transactions free cursors. + * @param[in] txn A transaction handle returned by #mdb_txn_begin() + */ +void mdb_txn_abort(MDB_txn *txn); + + /** @brief Reset a read-only transaction. + * + * Abort the transaction like #mdb_txn_abort(), but keep the transaction + * handle. #mdb_txn_renew() may reuse the handle. This saves allocation + * overhead if the process will start a new read-only transaction soon, + * and also locking overhead if #MDB_NOTLS is in use. The reader table + * lock is released, but the table slot stays tied to its thread or + * #MDB_txn. Use mdb_txn_abort() to discard a reset handle, and to free + * its lock table slot if MDB_NOTLS is in use. + * Cursors opened within the transaction must not be used + * again after this call, except with #mdb_cursor_renew(). + * Reader locks generally don't interfere with writers, but they keep old + * versions of database pages allocated. Thus they prevent the old pages + * from being reused when writers commit new data, and so under heavy load + * the database size may grow much more rapidly than otherwise. + * @param[in] txn A transaction handle returned by #mdb_txn_begin() + */ +void mdb_txn_reset(MDB_txn *txn); + + /** @brief Renew a read-only transaction. + * + * This acquires a new reader lock for a transaction handle that had been + * released by #mdb_txn_reset(). It must be called before a reset transaction + * may be used again. + * @param[in] txn A transaction handle returned by #mdb_txn_begin() + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>#MDB_PANIC - a fatal error occurred earlier and the environment + * must be shut down. + * <li>EINVAL - an invalid parameter was specified. + * </ul> + */ +int mdb_txn_renew(MDB_txn *txn); + +/** Compat with version <= 0.9.4, avoid clash with libmdb from MDB Tools project */ +#define mdb_open(txn,name,flags,dbi) mdb_dbi_open(txn,name,flags,dbi) +/** Compat with version <= 0.9.4, avoid clash with libmdb from MDB Tools project */ +#define mdb_close(env,dbi) mdb_dbi_close(env,dbi) + + /** @brief Open a database in the environment. + * + * A database handle denotes the name and parameters of a database, + * independently of whether such a database exists. + * The database handle may be discarded by calling #mdb_dbi_close(). + * The old database handle is returned if the database was already open. + * The handle may only be closed once. + * + * The database handle will be private to the current transaction until + * the transaction is successfully committed. If the transaction is + * aborted the handle will be closed automatically. + * After a successful commit the handle will reside in the shared + * environment, and may be used by other transactions. + * + * This function must not be called from multiple concurrent + * transactions in the same process. A transaction that uses + * this function must finish (either commit or abort) before + * any other transaction in the process may use this function. + * + * To use named databases (with name != NULL), #mdb_env_set_maxdbs() + * must be called before opening the environment. Database names are + * keys in the unnamed database, and may be read but not written. + * + * @param[in] txn A transaction handle returned by #mdb_txn_begin() + * @param[in] name The name of the database to open. If only a single + * database is needed in the environment, this value may be NULL. + * @param[in] flags Special options for this database. This parameter + * must be set to 0 or by bitwise OR'ing together one or more of the + * values described here. + * <ul> + * <li>#MDB_REVERSEKEY + * Keys are strings to be compared in reverse order, from the end + * of the strings to the beginning. By default, Keys are treated as strings and + * compared from beginning to end. + * <li>#MDB_DUPSORT + * Duplicate keys may be used in the database. (Or, from another perspective, + * keys may have multiple data items, stored in sorted order.) By default + * keys must be unique and may have only a single data item. + * <li>#MDB_INTEGERKEY + * Keys are binary integers in native byte order, either unsigned int + * or size_t, and will be sorted as such. + * The keys must all be of the same size. + * <li>#MDB_DUPFIXED + * This flag may only be used in combination with #MDB_DUPSORT. This option + * tells the library that the data items for this database are all the same + * size, which allows further optimizations in storage and retrieval. When + * all data items are the same size, the #MDB_GET_MULTIPLE, #MDB_NEXT_MULTIPLE + * and #MDB_PREV_MULTIPLE cursor operations may be used to retrieve multiple + * items at once. + * <li>#MDB_INTEGERDUP + * This option specifies that duplicate data items are binary integers, + * similar to #MDB_INTEGERKEY keys. + * <li>#MDB_REVERSEDUP + * This option specifies that duplicate data items should be compared as + * strings in reverse order. + * <li>#MDB_CREATE + * Create the named database if it doesn't exist. This option is not + * allowed in a read-only transaction or a read-only environment. + * </ul> + * @param[out] dbi Address where the new #MDB_dbi handle will be stored + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>#MDB_NOTFOUND - the specified database doesn't exist in the environment + * and #MDB_CREATE was not specified. + * <li>#MDB_DBS_FULL - too many databases have been opened. See #mdb_env_set_maxdbs(). + * </ul> + */ +int mdb_dbi_open(MDB_txn *txn, const char *name, unsigned int flags, MDB_dbi *dbi); + + /** @brief Retrieve statistics for a database. + * + * @param[in] txn A transaction handle returned by #mdb_txn_begin() + * @param[in] dbi A database handle returned by #mdb_dbi_open() + * @param[out] stat The address of an #MDB_stat structure + * where the statistics will be copied + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>EINVAL - an invalid parameter was specified. + * </ul> + */ +int mdb_stat(MDB_txn *txn, MDB_dbi dbi, MDB_stat *stat); + + /** @brief Retrieve the DB flags for a database handle. + * + * @param[in] txn A transaction handle returned by #mdb_txn_begin() + * @param[in] dbi A database handle returned by #mdb_dbi_open() + * @param[out] flags Address where the flags will be returned. + * @return A non-zero error value on failure and 0 on success. + */ +int mdb_dbi_flags(MDB_txn *txn, MDB_dbi dbi, unsigned int *flags); + + /** @brief Close a database handle. Normally unnecessary. Use with care: + * + * This call is not mutex protected. Handles should only be closed by + * a single thread, and only if no other threads are going to reference + * the database handle or one of its cursors any further. Do not close + * a handle if an existing transaction has modified its database. + * Doing so can cause misbehavior from database corruption to errors + * like MDB_BAD_VALSIZE (since the DB name is gone). + * + * Closing a database handle is not necessary, but lets #mdb_dbi_open() + * reuse the handle value. Usually it's better to set a bigger + * #mdb_env_set_maxdbs(), unless that value would be large. + * + * @param[in] env An environment handle returned by #mdb_env_create() + * @param[in] dbi A database handle returned by #mdb_dbi_open() + */ +void mdb_dbi_close(MDB_env *env, MDB_dbi dbi); + + /** @brief Empty or delete+close a database. + * + * See #mdb_dbi_close() for restrictions about closing the DB handle. + * @param[in] txn A transaction handle returned by #mdb_txn_begin() + * @param[in] dbi A database handle returned by #mdb_dbi_open() + * @param[in] del 0 to empty the DB, 1 to delete it from the + * environment and close the DB handle. + * @return A non-zero error value on failure and 0 on success. + */ +int mdb_drop(MDB_txn *txn, MDB_dbi dbi, int del); + + /** @brief Set a custom key comparison function for a database. + * + * The comparison function is called whenever it is necessary to compare a + * key specified by the application with a key currently stored in the database. + * If no comparison function is specified, and no special key flags were specified + * with #mdb_dbi_open(), the keys are compared lexically, with shorter keys collating + * before longer keys. + * @warning This function must be called before any data access functions are used, + * otherwise data corruption may occur. The same comparison function must be used by every + * program accessing the database, every time the database is used. + * @param[in] txn A transaction handle returned by #mdb_txn_begin() + * @param[in] dbi A database handle returned by #mdb_dbi_open() + * @param[in] cmp A #MDB_cmp_func function + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>EINVAL - an invalid parameter was specified. + * </ul> + */ +int mdb_set_compare(MDB_txn *txn, MDB_dbi dbi, MDB_cmp_func *cmp); + + /** @brief Set a custom data comparison function for a #MDB_DUPSORT database. + * + * This comparison function is called whenever it is necessary to compare a data + * item specified by the application with a data item currently stored in the database. + * This function only takes effect if the database was opened with the #MDB_DUPSORT + * flag. + * If no comparison function is specified, and no special key flags were specified + * with #mdb_dbi_open(), the data items are compared lexically, with shorter items collating + * before longer items. + * @warning This function must be called before any data access functions are used, + * otherwise data corruption may occur. The same comparison function must be used by every + * program accessing the database, every time the database is used. + * @param[in] txn A transaction handle returned by #mdb_txn_begin() + * @param[in] dbi A database handle returned by #mdb_dbi_open() + * @param[in] cmp A #MDB_cmp_func function + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>EINVAL - an invalid parameter was specified. + * </ul> + */ +int mdb_set_dupsort(MDB_txn *txn, MDB_dbi dbi, MDB_cmp_func *cmp); + + /** @brief Set a relocation function for a #MDB_FIXEDMAP database. + * + * @todo The relocation function is called whenever it is necessary to move the data + * of an item to a different position in the database (e.g. through tree + * balancing operations, shifts as a result of adds or deletes, etc.). It is + * intended to allow address/position-dependent data items to be stored in + * a database in an environment opened with the #MDB_FIXEDMAP option. + * Currently the relocation feature is unimplemented and setting + * this function has no effect. + * @param[in] txn A transaction handle returned by #mdb_txn_begin() + * @param[in] dbi A database handle returned by #mdb_dbi_open() + * @param[in] rel A #MDB_rel_func function + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>EINVAL - an invalid parameter was specified. + * </ul> + */ +int mdb_set_relfunc(MDB_txn *txn, MDB_dbi dbi, MDB_rel_func *rel); + + /** @brief Set a context pointer for a #MDB_FIXEDMAP database's relocation function. + * + * See #mdb_set_relfunc and #MDB_rel_func for more details. + * @param[in] txn A transaction handle returned by #mdb_txn_begin() + * @param[in] dbi A database handle returned by #mdb_dbi_open() + * @param[in] ctx An arbitrary pointer for whatever the application needs. + * It will be passed to the callback function set by #mdb_set_relfunc + * as its \b relctx parameter whenever the callback is invoked. + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>EINVAL - an invalid parameter was specified. + * </ul> + */ +int mdb_set_relctx(MDB_txn *txn, MDB_dbi dbi, void *ctx); + + /** @brief Get items from a database. + * + * This function retrieves key/data pairs from the database. The address + * and length of the data associated with the specified \b key are returned + * in the structure to which \b data refers. + * If the database supports duplicate keys (#MDB_DUPSORT) then the + * first data item for the key will be returned. Retrieval of other + * items requires the use of #mdb_cursor_get(). + * + * @note The memory pointed to by the returned values is owned by the + * database. The caller need not dispose of the memory, and may not + * modify it in any way. For values returned in a read-only transaction + * any modification attempts will cause a SIGSEGV. + * @note Values returned from the database are valid only until a + * subsequent update operation, or the end of the transaction. + * @param[in] txn A transaction handle returned by #mdb_txn_begin() + * @param[in] dbi A database handle returned by #mdb_dbi_open() + * @param[in] key The key to search for in the database + * @param[out] data The data corresponding to the key + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>#MDB_NOTFOUND - the key was not in the database. + * <li>EINVAL - an invalid parameter was specified. + * </ul> + */ +int mdb_get(MDB_txn *txn, MDB_dbi dbi, MDB_val *key, MDB_val *data); + + /** @brief Store items into a database. + * + * This function stores key/data pairs in the database. The default behavior + * is to enter the new key/data pair, replacing any previously existing key + * if duplicates are disallowed, or adding a duplicate data item if + * duplicates are allowed (#MDB_DUPSORT). + * @param[in] txn A transaction handle returned by #mdb_txn_begin() + * @param[in] dbi A database handle returned by #mdb_dbi_open() + * @param[in] key The key to store in the database + * @param[in,out] data The data to store + * @param[in] flags Special options for this operation. This parameter + * must be set to 0 or by bitwise OR'ing together one or more of the + * values described here. + * <ul> + * <li>#MDB_NODUPDATA - enter the new key/data pair only if it does not + * already appear in the database. This flag may only be specified + * if the database was opened with #MDB_DUPSORT. The function will + * return #MDB_KEYEXIST if the key/data pair already appears in the + * database. + * <li>#MDB_NOOVERWRITE - enter the new key/data pair only if the key + * does not already appear in the database. The function will return + * #MDB_KEYEXIST if the key already appears in the database, even if + * the database supports duplicates (#MDB_DUPSORT). The \b data + * parameter will be set to point to the existing item. + * <li>#MDB_RESERVE - reserve space for data of the given size, but + * don't copy the given data. Instead, return a pointer to the + * reserved space, which the caller can fill in later - before + * the next update operation or the transaction ends. This saves + * an extra memcpy if the data is being generated later. + * LMDB does nothing else with this memory, the caller is expected + * to modify all of the space requested. This flag must not be + * specified if the database was opened with #MDB_DUPSORT. + * <li>#MDB_APPEND - append the given key/data pair to the end of the + * database. This option allows fast bulk loading when keys are + * already known to be in the correct order. Loading unsorted keys + * with this flag will cause a #MDB_KEYEXIST error. + * <li>#MDB_APPENDDUP - as above, but for sorted dup data. + * </ul> + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>#MDB_MAP_FULL - the database is full, see #mdb_env_set_mapsize(). + * <li>#MDB_TXN_FULL - the transaction has too many dirty pages. + * <li>EACCES - an attempt was made to write in a read-only transaction. + * <li>EINVAL - an invalid parameter was specified. + * </ul> + */ +int mdb_put(MDB_txn *txn, MDB_dbi dbi, MDB_val *key, MDB_val *data, + unsigned int flags); + + /** @brief Delete items from a database. + * + * This function removes key/data pairs from the database. + * If the database does not support sorted duplicate data items + * (#MDB_DUPSORT) the data parameter is ignored. + * If the database supports sorted duplicates and the data parameter + * is NULL, all of the duplicate data items for the key will be + * deleted. Otherwise, if the data parameter is non-NULL + * only the matching data item will be deleted. + * This function will return #MDB_NOTFOUND if the specified key/data + * pair is not in the database. + * @param[in] txn A transaction handle returned by #mdb_txn_begin() + * @param[in] dbi A database handle returned by #mdb_dbi_open() + * @param[in] key The key to delete from the database + * @param[in] data The data to delete + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>EACCES - an attempt was made to write in a read-only transaction. + * <li>EINVAL - an invalid parameter was specified. + * </ul> + */ +int mdb_del(MDB_txn *txn, MDB_dbi dbi, MDB_val *key, MDB_val *data); + + /** @brief Create a cursor handle. + * + * A cursor is associated with a specific transaction and database. + * A cursor cannot be used when its database handle is closed. Nor + * when its transaction has ended, except with #mdb_cursor_renew(). + * It can be discarded with #mdb_cursor_close(). + * A cursor in a write-transaction can be closed before its transaction + * ends, and will otherwise be closed when its transaction ends. + * A cursor in a read-only transaction must be closed explicitly, before + * or after its transaction ends. It can be reused with + * #mdb_cursor_renew() before finally closing it. + * @note Earlier documentation said that cursors in every transaction + * were closed when the transaction committed or aborted. + * @param[in] txn A transaction handle returned by #mdb_txn_begin() + * @param[in] dbi A database handle returned by #mdb_dbi_open() + * @param[out] cursor Address where the new #MDB_cursor handle will be stored + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>EINVAL - an invalid parameter was specified. + * </ul> + */ +int mdb_cursor_open(MDB_txn *txn, MDB_dbi dbi, MDB_cursor **cursor); + + /** @brief Close a cursor handle. + * + * The cursor handle will be freed and must not be used again after this call. + * Its transaction must still be live if it is a write-transaction. + * @param[in] cursor A cursor handle returned by #mdb_cursor_open() + */ +void mdb_cursor_close(MDB_cursor *cursor); + + /** @brief Renew a cursor handle. + * + * A cursor is associated with a specific transaction and database. + * Cursors that are only used in read-only + * transactions may be re-used, to avoid unnecessary malloc/free overhead. + * The cursor may be associated with a new read-only transaction, and + * referencing the same database handle as it was created with. + * This may be done whether the previous transaction is live or dead. + * @param[in] txn A transaction handle returned by #mdb_txn_begin() + * @param[in] cursor A cursor handle returned by #mdb_cursor_open() + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>EINVAL - an invalid parameter was specified. + * </ul> + */ +int mdb_cursor_renew(MDB_txn *txn, MDB_cursor *cursor); + + /** @brief Return the cursor's transaction handle. + * + * @param[in] cursor A cursor handle returned by #mdb_cursor_open() + */ +MDB_txn *mdb_cursor_txn(MDB_cursor *cursor); + + /** @brief Return the cursor's database handle. + * + * @param[in] cursor A cursor handle returned by #mdb_cursor_open() + */ +MDB_dbi mdb_cursor_dbi(MDB_cursor *cursor); + + /** @brief Retrieve by cursor. + * + * This function retrieves key/data pairs from the database. The address and length + * of the key are returned in the object to which \b key refers (except for the + * case of the #MDB_SET option, in which the \b key object is unchanged), and + * the address and length of the data are returned in the object to which \b data + * refers. + * See #mdb_get() for restrictions on using the output values. + * @param[in] cursor A cursor handle returned by #mdb_cursor_open() + * @param[in,out] key The key for a retrieved item + * @param[in,out] data The data of a retrieved item + * @param[in] op A cursor operation #MDB_cursor_op + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>#MDB_NOTFOUND - no matching key found. + * <li>EINVAL - an invalid parameter was specified. + * </ul> + */ +int mdb_cursor_get(MDB_cursor *cursor, MDB_val *key, MDB_val *data, + MDB_cursor_op op); + + /** @brief Store by cursor. + * + * This function stores key/data pairs into the database. + * The cursor is positioned at the new item, or on failure usually near it. + * @note Earlier documentation incorrectly said errors would leave the + * state of the cursor unchanged. + * @param[in] cursor A cursor handle returned by #mdb_cursor_open() + * @param[in] key The key operated on. + * @param[in] data The data operated on. + * @param[in] flags Options for this operation. This parameter + * must be set to 0 or one of the values described here. + * <ul> + * <li>#MDB_CURRENT - replace the item at the current cursor position. + * The \b key parameter must still be provided, and must match it. + * If using sorted duplicates (#MDB_DUPSORT) the data item must still + * sort into the same place. This is intended to be used when the + * new data is the same size as the old. Otherwise it will simply + * perform a delete of the old record followed by an insert. + * <li>#MDB_NODUPDATA - enter the new key/data pair only if it does not + * already appear in the database. This flag may only be specified + * if the database was opened with #MDB_DUPSORT. The function will + * return #MDB_KEYEXIST if the key/data pair already appears in the + * database. + * <li>#MDB_NOOVERWRITE - enter the new key/data pair only if the key + * does not already appear in the database. The function will return + * #MDB_KEYEXIST if the key already appears in the database, even if + * the database supports duplicates (#MDB_DUPSORT). + * <li>#MDB_RESERVE - reserve space for data of the given size, but + * don't copy the given data. Instead, return a pointer to the + * reserved space, which the caller can fill in later - before + * the next update operation or the transaction ends. This saves + * an extra memcpy if the data is being generated later. This flag + * must not be specified if the database was opened with #MDB_DUPSORT. + * <li>#MDB_APPEND - append the given key/data pair to the end of the + * database. No key comparisons are performed. This option allows + * fast bulk loading when keys are already known to be in the + * correct order. Loading unsorted keys with this flag will cause + * a #MDB_KEYEXIST error. + * <li>#MDB_APPENDDUP - as above, but for sorted dup data. + * <li>#MDB_MULTIPLE - store multiple contiguous data elements in a + * single request. This flag may only be specified if the database + * was opened with #MDB_DUPFIXED. The \b data argument must be an + * array of two MDB_vals. The mv_size of the first MDB_val must be + * the size of a single data element. The mv_data of the first MDB_val + * must point to the beginning of the array of contiguous data elements. + * The mv_size of the second MDB_val must be the count of the number + * of data elements to store. On return this field will be set to + * the count of the number of elements actually written. The mv_data + * of the second MDB_val is unused. + * </ul> + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>#MDB_MAP_FULL - the database is full, see #mdb_env_set_mapsize(). + * <li>#MDB_TXN_FULL - the transaction has too many dirty pages. + * <li>EACCES - an attempt was made to write in a read-only transaction. + * <li>EINVAL - an invalid parameter was specified. + * </ul> + */ +int mdb_cursor_put(MDB_cursor *cursor, MDB_val *key, MDB_val *data, + unsigned int flags); + + /** @brief Delete current key/data pair + * + * This function deletes the key/data pair to which the cursor refers. + * This does not invalidate the cursor, so operations such as MDB_NEXT + * can still be used on it. + * Both MDB_NEXT and MDB_GET_CURRENT will return the same record after + * this operation. + * @param[in] cursor A cursor handle returned by #mdb_cursor_open() + * @param[in] flags Options for this operation. This parameter + * must be set to 0 or one of the values described here. + * <ul> + * <li>#MDB_NODUPDATA - delete all of the data items for the current key. + * This flag may only be specified if the database was opened with #MDB_DUPSORT. + * </ul> + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>EACCES - an attempt was made to write in a read-only transaction. + * <li>EINVAL - an invalid parameter was specified. + * </ul> + */ +int mdb_cursor_del(MDB_cursor *cursor, unsigned int flags); + + /** @brief Return count of duplicates for current key. + * + * This call is only valid on databases that support sorted duplicate + * data items #MDB_DUPSORT. + * @param[in] cursor A cursor handle returned by #mdb_cursor_open() + * @param[out] countp Address where the count will be stored + * @return A non-zero error value on failure and 0 on success. Some possible + * errors are: + * <ul> + * <li>EINVAL - cursor is not initialized, or an invalid parameter was specified. + * </ul> + */ +int mdb_cursor_count(MDB_cursor *cursor, size_t *countp); + + /** @brief Compare two data items according to a particular database. + * + * This returns a comparison as if the two data items were keys in the + * specified database. + * @param[in] txn A transaction handle returned by #mdb_txn_begin() + * @param[in] dbi A database handle returned by #mdb_dbi_open() + * @param[in] a The first item to compare + * @param[in] b The second item to compare + * @return < 0 if a < b, 0 if a == b, > 0 if a > b + */ +int mdb_cmp(MDB_txn *txn, MDB_dbi dbi, const MDB_val *a, const MDB_val *b); + + /** @brief Compare two data items according to a particular database. + * + * This returns a comparison as if the two items were data items of + * the specified database. The database must have the #MDB_DUPSORT flag. + * @param[in] txn A transaction handle returned by #mdb_txn_begin() + * @param[in] dbi A database handle returned by #mdb_dbi_open() + * @param[in] a The first item to compare + * @param[in] b The second item to compare + * @return < 0 if a < b, 0 if a == b, > 0 if a > b + */ +int mdb_dcmp(MDB_txn *txn, MDB_dbi dbi, const MDB_val *a, const MDB_val *b); + + /** @brief A callback function used to print a message from the library. + * + * @param[in] msg The string to be printed. + * @param[in] ctx An arbitrary context pointer for the callback. + * @return < 0 on failure, >= 0 on success. + */ +typedef int (MDB_msg_func)(const char *msg, void *ctx); + + /** @brief Dump the entries in the reader lock table. + * + * @param[in] env An environment handle returned by #mdb_env_create() + * @param[in] func A #MDB_msg_func function + * @param[in] ctx Anything the message function needs + * @return < 0 on failure, >= 0 on success. + */ +int mdb_reader_list(MDB_env *env, MDB_msg_func *func, void *ctx); + + /** @brief Check for stale entries in the reader lock table. + * + * @param[in] env An environment handle returned by #mdb_env_create() + * @param[out] dead Number of stale slots that were cleared + * @return 0 on success, non-zero on failure. + */ +int mdb_reader_check(MDB_env *env, int *dead); +/** @} */ + +#ifdef __cplusplus +} +#endif +/** @page tools LMDB Command Line Tools + The following describes the command line tools that are available for LMDB. + \li \ref mdb_copy_1 + \li \ref mdb_dump_1 + \li \ref mdb_load_1 + \li \ref mdb_stat_1 +*/ + +#endif /* _LMDB_H_ */ |