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Diffstat (limited to 'external/db_drivers/liblmdb/lmdb.h')
| -rw-r--r-- | external/db_drivers/liblmdb/lmdb.h | 1573 |
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diff --git a/external/db_drivers/liblmdb/lmdb.h b/external/db_drivers/liblmdb/lmdb.h deleted file mode 100644 index ebfbc5dc8..000000000 --- a/external/db_drivers/liblmdb/lmdb.h +++ /dev/null @@ -1,1573 +0,0 @@ -/** @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. - * - * @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 most systems: - * - Windows - automatic - * - BSD, systems using SysV semaphores - automatic - * - Linux, systems using POSIX mutexes with Robust option - automatic - * 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_SYSV_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(). - * - * - 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, without fork()ing. - * - * - 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 flock() advisory locking. - * - * - 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 2011-2014 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 14 - -/** 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 "September 20, 2014" - -/** 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. - * 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 numeric in native byte order */ -#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 key and 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 key and 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_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) - /** MDB_INCOMPATIBLE: Operation and DB incompatible, or DB flags changed */ -#define MDB_INCOMPATIBLE (-30784) - /** Invalid reuse of reader locktable slot */ -#define MDB_BAD_RSLOT (-30783) - /** Transaction cannot recover - it must be aborted */ -#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 is faster - * and uses fewer mallocs, but loses protection from application bugs - * like wild pointer writes and other bad updates into the database. - * 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 reseved 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. 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. - * </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. - * Most flags cannot be changed after #mdb_env_open(). - * @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. - * - * @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 buillt 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 kept as keys in the unnamed database. - * @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. Setting this option - * requires all keys to be the same size, typically sizeof(int) - * or sizeof(size_t). - * <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 and #MDB_NEXT_MULTIPLE - * cursor operations may be used to retrieve multiple items at once. - * <li>#MDB_INTEGERDUP - * This option specifies that duplicate data items are also integers, and - * should be sorted as such. - * <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. - * <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. This saves - * an extra memcpy if the data is being generated later. - * <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 - * data corruption. - * <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 modify a read-only database. - * <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. - * @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 modify a read-only database. - * <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_ */ |