/* * Copyright 2015-2017 Leonid Yuriev . * * This code is derived from "LMDB engine" written by * Howard Chu (Symas Corporation), which itself derived from btree.c * written by Martin Hedenfalk. * * --- * * Portions Copyright 2011-2017 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 * . * * --- * * Portions Copyright (c) 2009, 2010 Martin Hedenfalk * * 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. */ #pragma once #ifndef _MDBX_H_ #define _MDBX_H_ #define MDBX_MODE_ENABLED 1 #include #include #include #include #include #ifdef __cplusplus extern "C" { #endif /** Library major version */ #define MDB_VERSION_MAJOR 0 /** Library minor version */ #define MDB_VERSION_MINOR 9 /** Library patch version */ #define MDB_VERSION_PATCH 19 /** 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 "DEVEL" /** A stringifier for the version info */ #define MDB_VERSTR(a, b, c, d) \ "MDBX " #a "." #b "." #c ": (" d ", https://github.com/ReOpen/libmdbx)" /** 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 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 #mdbx_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 iovec MDB_val; #define mv_size iov_len #define mv_data iov_base /** @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 * #mdbx_set_relctx(). * @todo This feature is currently unimplemented. */ typedef void(MDB_rel_func)(MDB_val *item, void *oldptr, void *newptr, void *relctx); /** @defgroup mdbx_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 * WARNING: libmdbx don't support this mode. */ #define MDB_NOLOCK__UNSUPPORTED 0x400000 /** don't do readahead */ #define MDB_NORDAHEAD 0x800000 /** don't initialize malloc'd memory before writing to datafile */ #define MDB_NOMEMINIT 0x1000000 #if MDBX_MODE_ENABLED /** aim to coalesce FreeDB records */ #define MDBX_COALESCE 0x2000000 /** LIFO policy for reclaiming FreeDB records */ #define MDBX_LIFORECLAIM 0x4000000 #endif /* MDBX_MODE_ENABLED */ /** make a steady-sync only on close and explicit env-sync */ #define MDBX_UTTERLY_NOSYNC (MDB_NOSYNC | MDB_MAPASYNC) /** debuging option, fill/perturb released pages */ #define MDBX_PAGEPERTURB 0x8000000 /** @} */ /** @defgroup mdbx_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 #mdbx_size_t. * (lmdb expects 32-bit int <= size_t <= 32/64-bit mdbx_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 mdbx_put Write Flags * @{ */ /** For put: Don't write if the key already exists. */ #define MDB_NOOVERWRITE 0x10 /** Only for #MDB_DUPSORT
* For put: don't write if the key and data pair already exist.
* For mdbx_cursor_del: remove all duplicate data items. */ #define MDB_NODUPDATA 0x20 /** For mdbx_cursor_put: overwrite the current key/data pair * MDBX allows this flag for mdbx_put() for explicit overwrite/update without * insertion. */ #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 mdbx_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_PREV_MULTIPLE /**< Position at previous page and return key and 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) /** 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: *
    *
  • The operation expects an #MDB_DUPSORT / #MDB_DUPFIXED database. *
  • Opening a named DB when the unnamed DB has #MDB_DUPSORT / *#MDB_INTEGERKEY. *
  • Accessing a data record as a database, or vice versa. *
  • The database was dropped and recreated with different flags. *
*/ #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) /** Unexpected problem - txn should abort */ #define MDB_PROBLEM (-30779) /** The last defined error code */ #define MDB_LAST_ERRCODE MDB_PROBLEM /** @} */ /** @brief Statistics for a database in the environment */ typedef struct MDBX_stat { unsigned ms_psize; /**< Size of a database page. This is currently the same for all databases. */ unsigned 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 */ } MDBX_stat; /** @brief Information about the environment */ typedef struct MDBX_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 me_maxreaders; /**< max reader slots in the environment */ unsigned me_numreaders; /**< max reader slots used in the environment */ size_t me_tail_txnid; /**< ID of the last reader transaction */ size_t me_meta1_txnid, me_meta1_sign; size_t me_meta2_txnid, me_meta2_sign; } MDBX_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 *mdbx_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 *mdbx_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 #mdbx_env_close(). * Before the handle may be used, it must be opened using #mdbx_env_open(). * Various other options may also need to be set before opening the handle, * e.g. #mdbx_env_set_mapsize(), #mdbx_env_set_maxreaders(), * #mdbx_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 mdbx_env_create(MDB_env **env); /** @brief Open an environment handle. * * If this function fails, #mdbx_env_close() must be called to discard the *#MDB_env handle. * @param[in] env An environment handle returned by #mdbx_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 mdbx_env_set_flags() are also used. *
    *
  • #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. *
  • #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. *
  • #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. *
  • #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 (#mdbx_env_sync etc). *
  • #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 #mdbx_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 *#mdbx_env_set_flags(). *
  • #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 #mdbx_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 *#mdbx_env_sync() * is called. (#MDB_MAPASYNC | #MDB_WRITEMAP) may be preferable. * This flag may be changed at any time using *#mdbx_env_set_flags(). *
  • #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 *#mdbx_env_sync() * ensures on-disk database integrity until next commit. * This flag may be changed at any time using *#mdbx_env_set_flags(). *
  • #MDB_NOTLS * Don't use Thread-Local Storage. Tie reader locktable slots to * #MDB_txn objects instead of to threads. I.e. #mdbx_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. *
  • #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. *
  • #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. *
  • #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 *#mdbx_env_set_flags(). *
  • #MDBX_COALESCE * Aim to coalesce records while reclaiming FreeDB. * This flag may be changed at any time using *#mdbx_env_set_flags(). *
  • #MDBX_LIFORECLAIM * LIFO policy for reclaiming FreeDB records. This significantly *reduce * write IPOS in case MDB_NOSYNC with periodically checkpoints. *
* @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: *
    *
  • #MDB_VERSION_MISMATCH - the version of the LMDB library doesn't *match the * version that created the database environment. *
  • #MDB_INVALID - the environment file headers are corrupted. *
  • ENOENT - the directory specified by the path parameter doesn't *exist. *
  • EACCES - the user didn't have permission to access the environment *files. *
  • EAGAIN - the environment was locked by another process. *
*/ int mdbx_env_open(MDB_env *env, const char *path, unsigned flags, mode_t mode); int mdbx_env_open_ex(MDB_env *env, const char *path, unsigned flags, mode_t mode, int *exclusive); /** @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 #mdbx_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 mdbx_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 #mdbx_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 mdbx_env_copyfd(MDB_env *env, int 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 #mdbx_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. *
    *
  • #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. *
* @return A non-zero error value on failure and 0 on success. */ int mdbx_env_copy2(MDB_env *env, const char *path, unsigned 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 * #mdbx_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 #mdbx_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 #mdbx_env_copy2() for options. * @return A non-zero error value on failure and 0 on success. */ int mdbx_env_copyfd2(MDB_env *env, int fd, unsigned flags); /** @brief Return statistics about the LMDB environment. * * @param[in] env An environment handle returned by #mdbx_env_create() * @param[out] stat The address of an #MDB_stat structure * where the statistics will be copied */ int mdbx_env_stat(MDB_env *env, MDBX_stat *stat, size_t bytes); /** @brief Return information about the LMDB environment. * * @param[in] env An environment handle returned by #mdbx_env_create() * @param[out] stat The address of an #MDB_envinfo structure * where the information will be copied */ int mdbx_env_info(MDB_env *env, MDBX_envinfo *info, size_t bytes); /** @brief Flush the data buffers to disk. * * Data is always written to disk when #mdbx_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 #mdbx_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: *
    *
  • EACCES - the environment is read-only. *
  • EINVAL - an invalid parameter was specified. *
  • EIO - an error occurred during synchronization. *
*/ int mdbx_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 #mdbx_env_create() * @param[in] dont_sync A dont'sync flag, if non-zero the last checkpoint * (meta-page update) will be kept "as is" and may be still "weak" * in NOSYNC/MAPASYNC modes. Such "weak" checkpoint will be ignored * on opening next time, and transactions since the last non-weak * checkpoint (meta-page update) will rolledback for consistency guarantee. */ void mdbx_env_close(MDB_env *env); /** @brief Set environment flags. * * This may be used to set some flags in addition to those from * #mdbx_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 #mdbx_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: *
    *
  • EINVAL - an invalid parameter was specified. *
*/ int mdbx_env_set_flags(MDB_env *env, unsigned flags, int onoff); /** @brief Get environment flags. * * @param[in] env An environment handle returned by #mdbx_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: *
    *
  • EINVAL - an invalid parameter was specified. *
*/ int mdbx_env_get_flags(MDB_env *env, unsigned *flags); /** @brief Return the path that was used in #mdbx_env_open(). * * @param[in] env An environment handle returned by #mdbx_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: *
    *
  • EINVAL - an invalid parameter was specified. *
*/ int mdbx_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 #mdbx_env_create() * @param[out] fd Address of a int to contain the descriptor. * @return A non-zero error value on failure and 0 on success. Some possible * errors are: *
    *
  • EINVAL - an invalid parameter was specified. *
*/ int mdbx_env_get_fd(MDB_env *env, int *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 #mdbx_env_create() and before *#mdbx_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, #mdbx_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 #mdbx_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: *
    *
  • EINVAL - an invalid parameter was specified, or the environment *has * an active write transaction. *
*/ int mdbx_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, #mdbx_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 #mdbx_env_create() and before *#mdbx_env_open(). * @param[in] env An environment handle returned by #mdbx_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: *
    *
  • EINVAL - an invalid parameter was specified, or the environment is *already open. *
*/ int mdbx_env_set_maxreaders(MDB_env *env, unsigned readers); /** @brief Get the maximum number of threads/reader slots for the environment. * * @param[in] env An environment handle returned by #mdbx_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: *
    *
  • EINVAL - an invalid parameter was specified. *
*/ int mdbx_env_get_maxreaders(MDB_env *env, unsigned *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 #mdbx_env_create() and before *#mdbx_env_open(). * * Currently a moderate number of slots are cheap but a huge number gets * expensive: 7-120 words per transaction, and every #mdbx_dbi_open() * does a linear search of the opened slots. * @param[in] env An environment handle returned by #mdbx_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: *
    *
  • EINVAL - an invalid parameter was specified, or the environment is *already open. *
*/ int mdbx_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 #mdbx_env_create() * @return The maximum size of a key we can write */ int mdbx_env_get_maxkeysize(MDB_env *env); /** @brief Set application information associated with the #MDB_env. * * @param[in] env An environment handle returned by #mdbx_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 mdbx_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 #mdbx_env_create() * @return The pointer set by #mdbx_env_set_userctx(). */ void *mdbx_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 #mdbx_env_create(). * @param[in] msg The assertion message, not including newline. */ typedef void MDB_assert_func(MDB_env *env, const char *msg, const char *function, unsigned line); /** Set or reset the assert() callback of the environment. * Disabled if liblmdb is buillt with MDB_DEBUG=0. * @note This hack should become obsolete as lmdb's error handling matures. * @param[in] env An environment handle returned by #mdbx_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 mdbx_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 #mdbx_txn_abort() or *#mdbx_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 #mdbx_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 * mdbx_txn_commit and mdbx_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. *
    *
  • #MDB_RDONLY * This transaction will not perform any write operations. *
* @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: *
    *
  • #MDB_PANIC - a fatal error occurred earlier and the environment * must be shut down. *
  • #MDB_MAP_RESIZED - another process wrote data beyond this *MDB_env's * mapsize and this environment's map must be resized as well. * See #mdbx_env_set_mapsize(). *
  • #MDB_READERS_FULL - a read-only transaction was requested and * the reader lock table is full. See #mdbx_env_set_maxreaders(). *
  • ENOMEM - out of memory. *
*/ int mdbx_txn_begin(MDB_env *env, MDB_txn *parent, unsigned flags, MDB_txn **txn); /** @brief Returns the transaction's #MDB_env * * @param[in] txn A transaction handle returned by #mdbx_txn_begin() */ MDB_env *mdbx_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 #mdbx_txn_begin() * @return A transaction ID, valid if input is an active transaction. */ size_t mdbx_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 #mdbx_cursor_renew(). * * @note MDBX-mode: * A cursor must be closed explicitly always, before * or after its transaction ends. It can be reused with * #mdbx_cursor_renew() before finally closing it. * * @note LMDB-compatible mode: * Earlier documentation incorrectly said all cursors would be freed. * Only write-transactions free cursors. * * @param[in] txn A transaction handle returned by #mdbx_txn_begin() * @return A non-zero error value on failure and 0 on success. Some possible * errors are: *
    *
  • EINVAL - an invalid parameter was specified. *
  • ENOSPC - no more disk space. *
  • EIO - a low-level I/O error occurred while writing. *
  • ENOMEM - out of memory. *
*/ int mdbx_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 #mdbx_cursor_renew(). * * @note MDBX-mode: * A cursor must be closed explicitly always, before * or after its transaction ends. It can be reused with * #mdbx_cursor_renew() before finally closing it. * * @note LMDB-compatible mode: * Earlier documentation incorrectly said all cursors would be freed. * Only write-transactions free cursors. * * @param[in] txn A transaction handle returned by #mdbx_txn_begin() */ int mdbx_txn_abort(MDB_txn *txn); /** @brief Reset a read-only transaction. * * Abort the transaction like #mdbx_txn_abort(), but keep the transaction * handle. #mdbx_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 mdbx_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 #mdbx_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 #mdbx_txn_begin() */ int mdbx_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 #mdbx_txn_reset(). It must be called before a reset transaction * may be used again. * @param[in] txn A transaction handle returned by #mdbx_txn_begin() * @return A non-zero error value on failure and 0 on success. Some possible * errors are: *
    *
  • #MDB_PANIC - a fatal error occurred earlier and the environment * must be shut down. *
  • EINVAL - an invalid parameter was specified. *
*/ int mdbx_txn_renew(MDB_txn *txn); /** @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 #mdbx_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), #mdbx_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 #mdbx_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. *
    *
  • #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. *
  • #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. *
  • #MDB_INTEGERKEY * Keys are binary integers in native byte order, either unsigned *int * or #mdbx_size_t, and will be sorted as such. * (lmdb expects 32-bit int <= size_t <= 32/64-bit mdbx_size_t.) * The keys must all be of the same size. *
  • #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. *
  • #MDB_INTEGERDUP * This option specifies that duplicate data items are binary *integers, * similar to #MDB_INTEGERKEY keys. *
  • #MDB_REVERSEDUP * This option specifies that duplicate data items should be *compared as * strings in reverse order. *
  • #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. *
* @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: *
    *
  • #MDB_NOTFOUND - the specified database doesn't exist in the *environment * and #MDB_CREATE was not specified. *
  • #MDB_DBS_FULL - too many databases have been opened. See *#mdbx_env_set_maxdbs(). *
*/ int mdbx_dbi_open(MDB_txn *txn, const char *name, unsigned flags, MDB_dbi *dbi); /** @brief Retrieve statistics for a database. * * @param[in] txn A transaction handle returned by #mdbx_txn_begin() * @param[in] dbi A database handle returned by #mdbx_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: *
    *
  • EINVAL - an invalid parameter was specified. *
*/ int mdbx_stat(MDB_txn *txn, MDB_dbi dbi, MDBX_stat *stat, size_t bytes); /** @brief Retrieve the DB flags for a database handle. * * @param[in] txn A transaction handle returned by #mdbx_txn_begin() * @param[in] dbi A database handle returned by #mdbx_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 mdbx_dbi_flags(MDB_txn *txn, MDB_dbi dbi, unsigned *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 #mdbx_dbi_open() * reuse the handle value. Usually it's better to set a bigger * #mdbx_env_set_maxdbs(), unless that value would be large. * * @param[in] env An environment handle returned by #mdbx_env_create() * @param[in] dbi A database handle returned by #mdbx_dbi_open() */ void mdbx_dbi_close(MDB_env *env, MDB_dbi dbi); /** @brief Empty or delete+close a database. * * See #mdbx_dbi_close() for restrictions about closing the DB handle. * @param[in] txn A transaction handle returned by #mdbx_txn_begin() * @param[in] dbi A database handle returned by #mdbx_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 mdbx_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 #mdbx_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 #mdbx_txn_begin() * @param[in] dbi A database handle returned by #mdbx_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: *
    *
  • EINVAL - an invalid parameter was specified. *
*/ int mdbx_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 #mdbx_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 #mdbx_txn_begin() * @param[in] dbi A database handle returned by #mdbx_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: *
    *
  • EINVAL - an invalid parameter was specified. *
*/ int mdbx_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 #mdbx_txn_begin() * @param[in] dbi A database handle returned by #mdbx_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: *
    *
  • EINVAL - an invalid parameter was specified. *
*/ int mdbx_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 #mdbx_set_relfunc and #MDB_rel_func for more details. * @param[in] txn A transaction handle returned by #mdbx_txn_begin() * @param[in] dbi A database handle returned by #mdbx_dbi_open() * @param[in] ctx An arbitrary pointer for whatever the application needs. * It will be passed to the callback function set by #mdbx_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: *
    *
  • EINVAL - an invalid parameter was specified. *
*/ int mdbx_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 #mdbx_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 #mdbx_txn_begin() * @param[in] dbi A database handle returned by #mdbx_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: *
    *
  • #MDB_NOTFOUND - the key was not in the database. *
  • EINVAL - an invalid parameter was specified. *
*/ int mdbx_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 #mdbx_txn_begin() * @param[in] dbi A database handle returned by #mdbx_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. *
    *
  • #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. *
  • #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. *
  • #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. *
  • #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. *
  • #MDB_APPENDDUP - as above, but for sorted dup data. *
* @return A non-zero error value on failure and 0 on success. Some possible * errors are: *
    *
  • #MDB_MAP_FULL - the database is full, see #mdbx_env_set_mapsize(). *
  • #MDB_TXN_FULL - the transaction has too many dirty pages. *
  • EACCES - an attempt was made to write in a read-only transaction. *
  • EINVAL - an invalid parameter was specified. *
*/ int mdbx_put(MDB_txn *txn, MDB_dbi dbi, MDB_val *key, MDB_val *data, unsigned flags); /** @brief Delete items from a database. * * This function removes key/data pairs from the database. * * MDBX-mode: * The data parameter is NOT ignored regardless the database does * support sorted duplicate data items or not. If the data parameter * is non-NULL only the matching data item will be deleted. * * LMDB-compatible mode: * 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 #mdbx_txn_begin() * @param[in] dbi A database handle returned by #mdbx_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: *
    *
  • EACCES - an attempt was made to write in a read-only transaction. *
  • EINVAL - an invalid parameter was specified. *
*/ int mdbx_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 #mdbx_cursor_renew(). * It can be discarded with #mdbx_cursor_close(). * * MDBX-mode: * A cursor must be closed explicitly always, before * or after its transaction ends. It can be reused with * #mdbx_cursor_renew() before finally closing it. * * LMDB-compatible mode: * 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 * #mdbx_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 #mdbx_txn_begin() * @param[in] dbi A database handle returned by #mdbx_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: *
    *
  • EINVAL - an invalid parameter was specified. *
*/ int mdbx_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 #mdbx_cursor_open() */ void mdbx_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 #mdbx_txn_begin() * @param[in] cursor A cursor handle returned by #mdbx_cursor_open() * @return A non-zero error value on failure and 0 on success. Some possible * errors are: *
    *
  • EINVAL - an invalid parameter was specified. *
*/ int mdbx_cursor_renew(MDB_txn *txn, MDB_cursor *cursor); /** @brief Return the cursor's transaction handle. * * @param[in] cursor A cursor handle returned by #mdbx_cursor_open() */ MDB_txn *mdbx_cursor_txn(MDB_cursor *cursor); /** @brief Return the cursor's database handle. * * @param[in] cursor A cursor handle returned by #mdbx_cursor_open() */ MDB_dbi mdbx_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 #mdbx_get() for restrictions on using the output values. * @param[in] cursor A cursor handle returned by #mdbx_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: *
    *
  • #MDB_NOTFOUND - no matching key found. *
  • EINVAL - an invalid parameter was specified. *
*/ int mdbx_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 #mdbx_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. *
    *
  • #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. *
  • #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. *
  • #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). *
  • #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. *
  • #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. *
  • #MDB_APPENDDUP - as above, but for sorted dup data. *
  • #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. *
* @return A non-zero error value on failure and 0 on success. Some possible * errors are: *
    *
  • #MDB_MAP_FULL - the database is full, see #mdbx_env_set_mapsize(). *
  • #MDB_TXN_FULL - the transaction has too many dirty pages. *
  • EACCES - an attempt was made to write in a read-only transaction. *
  • EINVAL - an invalid parameter was specified. *
*/ int mdbx_cursor_put(MDB_cursor *cursor, MDB_val *key, MDB_val *data, unsigned 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 #mdbx_cursor_open() * @param[in] flags Options for this operation. This parameter * must be set to 0 or one of the values described here. *
    *
  • #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. *
* @return A non-zero error value on failure and 0 on success. Some possible * errors are: *
    *
  • EACCES - an attempt was made to write in a read-only transaction. *
  • EINVAL - an invalid parameter was specified. *
*/ int mdbx_cursor_del(MDB_cursor *cursor, unsigned 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 #mdbx_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: *
    *
  • EINVAL - cursor is not initialized, or an invalid parameter was *specified. *
*/ int mdbx_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 #mdbx_txn_begin() * @param[in] dbi A database handle returned by #mdbx_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 mdbx_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 #mdbx_txn_begin() * @param[in] dbi A database handle returned by #mdbx_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 mdbx_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 #mdbx_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 mdbx_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 #mdbx_env_create() * @param[out] dead Number of stale slots that were cleared * @return 0 on success, non-zero on failure. */ int mdbx_reader_check(MDB_env *env, int *dead); char *mdbx_dkey(MDB_val *key, char *buf); int mdbx_env_close_ex(MDB_env *env, int dont_sync); /** @brief Set threshold to force flush the data buffers to disk, * even of #MDB_NOSYNC, #MDB_NOMETASYNC and #MDB_MAPASYNC flags * in the environment. * * Data is always written to disk when #mdbx_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. * * The default is 0, than mean no any threshold checked, * and no additional flush will be made. * * @param[in] env An environment handle returned by #mdbx_env_create() * @param[in] bytes The size in bytes of summary changes * when a synchronous flush would be made. * @return A non-zero error value on failure and 0 on success. */ int mdbx_env_set_syncbytes(MDB_env *env, size_t bytes); /** @brief Returns a lag of the reading. * * Returns an information for estimate how much given read-only * transaction is lagging relative the to actual head. * * @param[in] txn A transaction handle returned by #mdbx_txn_begin() * @param[out] percent Percentage of page allocation in the database. * @return Number of transactions committed after the given was started for * read, or -1 on failure. */ int mdbx_txn_straggler(MDB_txn *txn, int *percent); /** @brief A callback function for killing a laggard readers, * but also could waiting ones. Called in case of MDB_MAP_FULL error. * * @param[in] env An environment handle returned by #mdbx_env_create(). * @param[in] pid pid of the reader process. * @param[in] thread_id thread_id of the reader thread. * @param[in] txn Transaction number on which stalled. * @param[in] gap a lag from the last commited txn. * @param[in] retry a retry number, less that zero for notify end of OOM-loop. * @return -1 on failure (reader is not killed), * 0 on a race condition (no such reader), * 1 on success (reader was killed), * >1 on success (reader was SURE killed). */ typedef int(MDBX_oom_func)(MDB_env *env, int pid, void *thread_id, size_t txn, unsigned gap, int retry); /** @brief Set the OOM callback. * * Callback will be called only on out-of-pages case for killing * a laggard readers to allowing reclaiming of freeDB. * * @param[in] env An environment handle returned by #mdbx_env_create(). * @param[in] oomfunc A #MDBX_oom_func function or NULL to disable. */ void mdbx_env_set_oomfunc(MDB_env *env, MDBX_oom_func *oom_func); /** @brief Get the current oom_func callback. * * Callback will be called only on out-of-pages case for killing * a laggard readers to allowing reclaiming of freeDB. * * @param[in] env An environment handle returned by #mdbx_env_create(). * @return A #MDBX_oom_func function or NULL if disabled. */ MDBX_oom_func *mdbx_env_get_oomfunc(MDB_env *env); #define MDBX_DBG_ASSERT 1 #define MDBX_DBG_PRINT 2 #define MDBX_DBG_TRACE 4 #define MDBX_DBG_EXTRA 8 #define MDBX_DBG_AUDIT 16 #define MDBX_DBG_EDGE 32 /* LY: a "don't touch" value */ #define MDBX_DBG_DNT (-1L) typedef void MDBX_debug_func(int type, const char *function, int line, const char *msg, va_list args); int mdbx_setup_debug(int flags, MDBX_debug_func *logger, long edge_txn); typedef int MDBX_pgvisitor_func(size_t pgno, unsigned pgnumber, void *ctx, const char *dbi, const char *type, int nentries, int payload_bytes, int header_bytes, int unused_bytes); int mdbx_env_pgwalk(MDB_txn *txn, MDBX_pgvisitor_func *visitor, void *ctx); typedef struct mdbx_canary { size_t x, y, z, v; } mdbx_canary; int mdbx_canary_put(MDB_txn *txn, const mdbx_canary *canary); size_t mdbx_canary_get(MDB_txn *txn, mdbx_canary *canary); /* Returns: * - MDBX_RESULT_TRUE when no more data available * or cursor not positioned; * - MDBX_RESULT_FALSE when data available; * - Otherwise the error code. */ int mdbx_cursor_eof(MDB_cursor *mc); /* Returns: MDBX_RESULT_TRUE, MDBX_RESULT_FALSE or Error code. */ int mdbx_cursor_on_first(MDB_cursor *mc); /* Returns: MDBX_RESULT_TRUE, MDBX_RESULT_FALSE or Error code. */ int mdbx_cursor_on_last(MDB_cursor *mc); #define MDBX_EMULTIVAL (MDB_LAST_ERRCODE - 42) #define MDBX_RESULT_FALSE MDB_SUCCESS #define MDBX_RESULT_TRUE (-1) int mdbx_replace(MDB_txn *txn, MDB_dbi dbi, MDB_val *key, MDB_val *new_data, MDB_val *old_data, unsigned flags); /* Same as mdbx_get(), but: * 1) if values_count is not NULL, then returns the count * of multi-values/duplicates for a given key. * 2) updates the key for pointing to the actual key's data inside DB. */ int mdbx_get_ex(MDB_txn *txn, MDB_dbi dbi, MDB_val *key, MDB_val *data, int *values_count); int mdbx_is_dirty(const MDB_txn *txn, const void *ptr); int mdbx_dbi_open_ex(MDB_txn *txn, const char *name, unsigned flags, MDB_dbi *dbi, MDB_cmp_func *keycmp, MDB_cmp_func *datacmp); #ifdef __cplusplus } #endif #endif /* _MDBX_H_ */