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846 lines
38 KiB
846 lines
38 KiB
/** @file mdb.h
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* @brief memory-mapped database library
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*
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* @mainpage MDB Memory-Mapped Database Manager
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* MDB is a Btree-based database management library modeled loosely on the
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* BerkeleyDB API, but much simplified. The entire database is exposed
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* in a read-only memory map, and all data fetches return data directly
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* from the mapped memory, so no malloc's or memcpy's occur during
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* data fetches. As such, the library is extremely simple because it
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* requires no page caching layer of its own, and it is extremely high
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* performance and memory-efficient. It is also fully transactional with
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* full ACID semantics, and because the memory map is read-only, the
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* database integrity cannot be corrupted by stray pointer writes from
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* application code.
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*
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* The library is fully thread-aware and supports concurrent read/write
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* access from multiple processes and threads. Data pages use a copy-on-
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* write strategy so no active data pages are ever overwritten, which
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* also provides resistance to corruption and eliminates the need of any
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* special recovery procedures after a system crash. Writes are fully
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* serialized; only one write transaction may be active at a time, which
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* guarantees that writers can never deadlock. The database structure is
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* multi-versioned so readers run with no locks; writers cannot block
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* readers, and readers don't block writers.
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*
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* Unlike other well-known database mechanisms which use either write-ahead
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* transaction logs or append-only data writes, MDB requires no maintenance
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* during operation. Both write-ahead loggers and append-only databases
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* require periodic checkpointing and/or compaction of their log or database
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* files otherwise they grow without bound. MDB tracks free pages within
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* the database and re-uses them for new write operations, so the database
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* size does not grow without bound in normal use.
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*
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* @author Howard Chu, Symas Corporation.
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*
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* @copyright Copyright 2011 Howard Chu, Symas Corp. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted only as authorized by the OpenLDAP
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* Public License.
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*
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* A copy of this license is available in the file LICENSE in the
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* top-level directory of the distribution or, alternatively, at
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* <http://www.OpenLDAP.org/license.html>.
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*
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* @par Derived From:
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* This code is derived from btree.c written by Martin Hedenfalk.
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*
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* Copyright (c) 2009, 2010 Martin Hedenfalk <martin@bzero.se>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#ifndef _MDB_H_
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#define _MDB_H_
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#include <sys/types.h>
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/** @defgroup public Public API
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* @{
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*/
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/** @defgroup Version Version Macros
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* @{
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*/
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/** Library major version */
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#define MDB_VERSION_MAJOR 0
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/** Library minor version */
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#define MDB_VERSION_MINOR 9
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/** Library patch version */
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#define MDB_VERSION_PATCH 0
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/** Combine args a,b,c into a single integer for easy version comparisons */
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#define MDB_VERINT(a,b,c) (((a) << 24) | ((b) << 16) | (c))
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/** The full library version as a single integer */
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#define MDB_VERSION_FULL \
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MDB_VERINT(MDB_VERSION_MAJOR,MDB_VERSION_MINOR,MDB_VERSION_PATCH)
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/** The release date of this library version */
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#define MDB_VERSION_DATE "September 1, 2011"
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/** A stringifier for the version info */
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#define MDB_VERSTR(a,b,c,d) "MDB " #a "." #b "." #c ": (" #d ")"
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/** A helper for the stringifier macro */
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#define MDB_VERFOO(a,b,c,d) MDB_VERSTR(a,b,c,d)
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/** The full library version as a C string */
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#define MDB_VERSION_STRING \
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MDB_VERFOO(MDB_VERSION_MAJOR,MDB_VERSION_MINOR,MDB_VERSION_PATCH,MDB_VERSION_DATE)
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/** @} */
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/** Opaque structure for a database environment. A DB environment supports multiple
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* databases, all residing in the same shared-memory map.
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*/
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typedef struct MDB_env MDB_env;
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/** Opaque structure for a transaction handle. All database operations require
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* a transaction handle. Transactions may be read-only or read-write.
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*/
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typedef struct MDB_txn MDB_txn;
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/** A handle for an individual database in the DB environment. */
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typedef unsigned int MDB_dbi;
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/** Opaque structure for navigating through a database */
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typedef struct MDB_cursor MDB_cursor;
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/** Generic structure used for passing keys and data in and out of the database. */
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typedef struct MDB_val {
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size_t mv_size; /**< size of the data item */
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void *mv_data; /**< address of the data item */
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} MDB_val;
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/** A callback function used to compare two keys in a database */
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typedef int (MDB_cmp_func)(const MDB_val *a, const MDB_val *b);
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/** A callback function used to relocate a position-dependent data item
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* in a fixed-address database. The \b newptr gives the item's current address in
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* the memory map, and \b oldptr gives its previous address. This callback is
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* expected to walk through the fields of the record in newptr and modify any
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* values based at the \b oldptr address to be relative to the \b newptr address.
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* @todo This feature is currently unimplemented.
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*/
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typedef void (MDB_rel_func)(void *newptr, void *oldptr, size_t size);
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/** @defgroup mdb_env Environment Flags
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* @{
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*/
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/** mmap at a fixed address */
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#define MDB_FIXEDMAP 0x01
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/** don't fsync after commit */
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#define MDB_NOSYNC 0x10000
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/** read only */
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#define MDB_RDONLY 0x20000
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/** @} */
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/** @defgroup mdb_open Database Flags
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* @{
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*/
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/** use reverse string keys */
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#define MDB_REVERSEKEY 0x02
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/** use sorted duplicates */
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#define MDB_DUPSORT 0x04
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/** numeric keys in native byte order */
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#define MDB_INTEGERKEY 0x08
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/** with #MDB_DUPSORT, sorted dup items have fixed size */
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#define MDB_DUPFIXED 0x10
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/** with #MDB_DUPSORT, dups are numeric in native byte order */
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#define MDB_INTEGERDUP 0x20
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/** create DB if not already existing */
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#define MDB_CREATE 0x40000
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/** @} */
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/** @defgroup mdb_put Write Flags
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* @{
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*/
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/** For put: Don't write if the key already exists. */
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#define MDB_NOOVERWRITE 0x10
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/** Only for #MDB_DUPSORT<br>
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* For put: don't write if the key and data pair already exist.<br>
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* For mdb_cursor_del: remove all duplicate data items.
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*/
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#define MDB_NODUPDATA 0x20
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/** For mdb_cursor_put: overwrite the current key/data pair */
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#define MDB_CURRENT 0x40
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/* @} */
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/** Cursor operations */
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typedef enum MDB_cursor_op {
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MDB_FIRST, /**< Position at first key/data item */
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MDB_FIRST_DUP, /**< Position at first data item of current key.
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Only for #MDB_DUPSORT */
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MDB_GET_BOTH, /**< Position at key/data pair. Only for #MDB_DUPSORT */
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MDB_GET_BOTH_RANGE, /**< position at key, nearest data. Only for #MDB_DUPSORT */
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MDB_GET_MULTIPLE, /**< Return all the duplicate data items at the current
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cursor position. Only for #MDB_DUPFIXED */
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MDB_LAST, /**< Position at last key/data item */
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MDB_LAST_DUP, /**< Position at last data item of current key.
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Only for #MDB_DUPSORT */
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MDB_NEXT, /**< Position at next data item */
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MDB_NEXT_DUP, /**< Position at next data item of current key.
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Only for #MDB_DUPSORT */
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MDB_NEXT_MULTIPLE, /**< Return all duplicate data items at the next
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cursor position. Only for #MDB_DUPFIXED */
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MDB_NEXT_NODUP, /**< Position at first data item of next key.
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Only for #MDB_DUPSORT */
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MDB_PREV, /**< Position at previous data item */
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MDB_PREV_DUP, /**< Position at previous data item of current key.
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Only for #MDB_DUPSORT */
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MDB_PREV_NODUP, /**< Position at last data item of previous key.
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only for #MDB_DUPSORT */
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MDB_SET, /**< Position at specified key */
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MDB_SET_RANGE /**< Position at first key greater than or equal to specified key. */
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} MDB_cursor_op;
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/** @defgroup errors Return Codes
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*
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* BerkeleyDB uses -30800 to -30999, we'll go under them
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* @{
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*/
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/** Successful result */
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#define MDB_SUCCESS 0
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/** key/data pair already exists */
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#define MDB_KEYEXIST (-30799)
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/** key/data pair not found (EOF) */
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#define MDB_NOTFOUND (-30798)
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/** Requested page not found - this usually indicates corruption */
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#define MDB_PAGE_NOTFOUND (-30797)
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/** Located page was wrong type */
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#define MDB_CORRUPTED (-30796)
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/** Update of meta page failed, probably I/O error */
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#define MDB_PANIC (-30795)
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/** Environment version mismatch */
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#define MDB_VERSION_MISMATCH (-30794)
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/** @} */
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/** Statistics for a database in the environment */
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typedef struct MDB_stat {
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unsigned int ms_psize; /**< Size of a database page.
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This is currently the same for all databases. */
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unsigned int ms_depth; /**< Depth (height) of the B-tree */
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unsigned long ms_branch_pages; /**< Number of internal (non-leaf) pages */
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unsigned long ms_leaf_pages; /**< Number of leaf pages */
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unsigned long ms_overflow_pages; /**< Number of overflow pages */
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unsigned long ms_entries; /**< Number of data items */
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} MDB_stat;
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/** Return the mdb library version information.
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* @param[out] major if non-NULL, the library major version number is copied here
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* @param[out] minor if non-NULL, the library minor version number is copied here
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* @param[out] patch if non-NULL, the library patch version number is copied here
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* @retval "version string" The library version as a string
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*/
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char *mdb_version(int *major, int *minor, int *patch);
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/** Return a string describing a given error code.
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* This function is a superset of the ANSI C X3.159-1989 (ANSI C) strerror(3)
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* function. If the error code is greater than or equal to 0, then the string
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* returned by the system function strerror(3) is returned. If the error code
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* is less than 0, an error string corresponding to the MDB library error is
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* returned. See @ref errors for a list of MDB-specific error codes.
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* @param[in] err The error code
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* @retval "error message" The description of the error
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*/
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char *mdb_strerror(int err);
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/** Create an MDB environment handle.
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* This function allocates memory for a #MDB_env structure. To release
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* the allocated memory and discard the handle, call #mdb_env_close().
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* Before the handle may be used, it must be opened using #mdb_env_open().
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* Various other options may also need to be set before opening the handle,
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* e.g. #mdb_env_set_mapsize(), #mdb_env_set_maxreaders(), #mdb_env_set_maxdbs(),
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* depending on usage requirements.
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* @param[out] env The address where the new handle will be stored
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* @return A non-zero error value on failure and 0 on success.
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*/
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int mdb_env_create(MDB_env **env);
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/** Open an environment handle.
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* If this function fails, #mdb_env_close() must be called to discard the #MDB_env handle.
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* @param[in] env An environment handle returned by #mdb_env_create()
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* @param[in] path The directory in which the database files reside. This
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* directory must already exist and be writable.
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* @param[in] flags Special options for this environment. This parameter
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* must be set to 0 or by bitwise OR'ing together one or more of the
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* values described here.
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* <ul>
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* <li>#MDB_FIXEDMAP
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* use a fixed address for the mmap region. This flag must be specified
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* when creating the environment, and is stored persistently in the environment.
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* If successful, the memory map will always reside at the same virtual address
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* and pointers used to reference data items in the database will be constant
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* across multiple invocations. This option may not always work, depending on
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* how the operating system has allocated memory to shared libraries and other uses.
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* The feature is highly experimental.
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* <li>#MDB_NOSYNC
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* Don't perform a synchronous flush after committing a transaction. This means
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* transactions will exhibit the ACI (atomicity, consistency, and isolation)
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* properties, but not D (durability); that is database integrity will be
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* maintained but it is possible some number of the most recently committed
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* transactions may be undone after a system crash. The number of transactions
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* at risk is governed by how often the system flushes dirty buffers to disk
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* and how often #mdb_env_sync() is called. This flag may be changed
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* at any time using #mdb_env_set_flags().
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* <li>#MDB_RDONLY
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* Open the environment in read-only mode. No write operations will be allowed.
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* </ul>
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* @param[in] mode The UNIX permissions to set on created files. This parameter
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* is ignored on Windows.
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* @return A non-zero error value on failure and 0 on success. Some possible
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* errors are:
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* <ul>
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* <li>#MDB_VERSION_MISMATCH - the version of the MDB library doesn't match the
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* version that created the database environment.
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* <li>EINVAL - the environment file headers are corrupted.
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* <li>ENOENT - the directory specified by the path parameter doesn't exist.
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* <li>EACCES - the user didn't have permission to access the environment files.
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* <li>EAGAIN - the environment was locked by another process.
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* </ul>
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*/
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int mdb_env_open(MDB_env *env, const char *path, unsigned int flags, mode_t mode);
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/** Return statistics about the MDB environment.
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* @param[in] env An environment handle returned by #mdb_env_create()
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* @param[out] stat The address of an #MDB_stat structure
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* where the statistics will be copied
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*/
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int mdb_env_stat(MDB_env *env, MDB_stat *stat);
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/** Flush the data buffers to disk.
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* Data is always written to disk when #mdb_txn_commit() is called,
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* but the operating system may keep it buffered. MDB always flushes
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* the OS buffers upon commit as well, unless the environment was
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* opened with #MDB_NOSYNC.
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* @param[in] env An environment handle returned by #mdb_env_create()
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* @param[in] force If non-zero, force the flush to occur. Otherwise
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* if the environment has the #MDB_NOSYNC flag set the flushes
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* will be omitted.
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* @return A non-zero error value on failure and 0 on success. Some possible
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* errors are:
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* <ul>
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* <li>EINVAL - an invalid parameter was specified.
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* <li>EIO - an error occurred during synchronization.
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* </ul>
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*/
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int mdb_env_sync(MDB_env *env, int force);
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/** Close the environment and release the memory map.
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* Only a single thread may call this function. All transactions, databases,
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* and cursors must already be closed before calling this function. Attempts to
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* use any such handles after calling this function will cause a SIGSEGV.
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* The environment handle will be freed and must not be used again after this call.
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* @param[in] env An environment handle returned by #mdb_env_create()
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*/
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void mdb_env_close(MDB_env *env);
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/** Set environment flags.
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* This may be used to set some flags that weren't already set during
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* #mdb_env_open(), or to unset these flags. Currently only the
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* #MDB_NOSYNC flag setting may be changed with this function.
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* @param[in] env An environment handle returned by #mdb_env_create()
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* @param[in] flags The flags to change, bitwise OR'ed together
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* @param[in] onoff A non-zero value sets the flags, zero clears them.
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* @return A non-zero error value on failure and 0 on success. Some possible
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* errors are:
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* <ul>
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* <li>EINVAL - an invalid parameter was specified.
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* </ul>
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*/
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int mdb_env_set_flags(MDB_env *env, unsigned int flags, int onoff);
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/** Get environment flags.
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* @param[in] env An environment handle returned by #mdb_env_create()
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* @param[out] flags The address of an integer to store the flags
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* @return A non-zero error value on failure and 0 on success. Some possible
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* errors are:
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* <ul>
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* <li>EINVAL - an invalid parameter was specified.
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* </ul>
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*/
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int mdb_env_get_flags(MDB_env *env, unsigned int *flags);
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/** Return the path that was used in #mdb_env_open().
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* @param[in] env An environment handle returned by #mdb_env_create()
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* @param[out] path Address of a string pointer to contain the path. This
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* is the actual string in the environment, not a copy. It should not be
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* altered in any way.
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* @return A non-zero error value on failure and 0 on success. Some possible
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* errors are:
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* <ul>
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* <li>EINVAL - an invalid parameter was specified.
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* </ul>
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*/
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int mdb_env_get_path(MDB_env *env, const char **path);
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/** Set the size of the memory map to use for this environment.
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* The size should be a multiple of the OS page size. The default is
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* 10485760 bytes. The size of the memory map is also the maximum size
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* of the database. The value should be chosen as large as possible,
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* to accomodate future growth of the database.
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* This function may only be called after #mdb_env_create() and before #mdb_env_open().
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* @param[in] env An environment handle returned by #mdb_env_create()
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* @param[in] size The size in bytes
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* @return A non-zero error value on failure and 0 on success. Some possible
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* errors are:
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* <ul>
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* <li>EINVAL - an invalid parameter was specified, or the environment is already open.
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* </ul>
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*/
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int mdb_env_set_mapsize(MDB_env *env, size_t size);
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/** Set the maximum number of threads for the environment.
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* This defines the number of slots in the lock table that is used to track readers in the
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* the environment. The default is 126.
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* This function may only be called after #mdb_env_create() and before #mdb_env_open().
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* @param[in] env An environment handle returned by #mdb_env_create()
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* @param[in] readers The maximum number of threads
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* @return A non-zero error value on failure and 0 on success. Some possible
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* errors are:
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* <ul>
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* <li>EINVAL - an invalid parameter was specified, or the environment is already open.
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* </ul>
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*/
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int mdb_env_set_maxreaders(MDB_env *env, int readers);
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/** Get the maximum number of threads for the environment.
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* @param[in] env An environment handle returned by #mdb_env_create()
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* @param[out] readers Address of an integer to store the number of readers
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* @return A non-zero error value on failure and 0 on success. Some possible
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* errors are:
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* <ul>
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* <li>EINVAL - an invalid parameter was specified.
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* </ul>
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*/
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int mdb_env_get_maxreaders(MDB_env *env, int *readers);
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/** Set the maximum number of databases for the environment.
|
|
* This function is only needed if multiple databases will be used in the
|
|
* environment. Simpler applications that only use a single database can ignore
|
|
* this option.
|
|
* 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] 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, int dbs);
|
|
|
|
/** Create a transaction for use with the environment.
|
|
* The transaction handle may be discarded using #mdb_txn_abort() or #mdb_txn_commit().
|
|
* @note Transactions may not span threads, a transaction must only be used by a
|
|
* single thread.
|
|
* @note Cursors may not span transactions; each cursor must be opened and closed
|
|
* within a single transaction.
|
|
* @param[in] env An environment handle returned by #mdb_env_create()
|
|
* @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>ENOMEM - out of memory, or a read-only transaction was requested and
|
|
* the reader lock table is full. See #mdb_env_set_maxreaders().
|
|
* </ul>
|
|
*/
|
|
int mdb_txn_begin(MDB_env *env, unsigned int flags, MDB_txn **txn);
|
|
|
|
/** Commit all the operations of a transaction into the database.
|
|
* All cursors opened within the transaction must be closed before the transaction
|
|
* is committed.
|
|
* The transaction handle will be freed and must not be used again after this call.
|
|
* @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.
|
|
* </ul>
|
|
*/
|
|
int mdb_txn_commit(MDB_txn *txn);
|
|
|
|
/** Abandon all the operations of the transaction instead of saving them.
|
|
* All cursors opened within the transaction must be closed before the transaction
|
|
* is aborted.
|
|
* The transaction handle will be freed and must not be used again after this call.
|
|
* @param[in] txn A transaction handle returned by #mdb_txn_begin()
|
|
*/
|
|
void mdb_txn_abort(MDB_txn *txn);
|
|
|
|
/** Reset a read-only transaction.
|
|
* This releases the current reader lock but doesn't free the
|
|
* transaction handle, allowing it to be used again later by #mdb_txn_renew().
|
|
* It otherwise has the same affect as #mdb_txn_abort() but saves some memory
|
|
* allocation/deallocation overhead if a thread is going to start a new
|
|
* read-only transaction again soon.
|
|
* All cursors opened within the transaction must be closed before the transaction
|
|
* is reset.
|
|
* 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);
|
|
|
|
/** 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);
|
|
|
|
/** Open a database in the environment.
|
|
* The database handle may be discarded by calling #mdb_close().
|
|
* @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 enviroment, 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. On Big-Endian systems
|
|
* this flag has no effect. On Little-Endian systems this flag behaves
|
|
* the same as #MDB_REVERSEKEY. This flag is simply provided as a
|
|
* convenience so that applications don't need to detect Endianness themselves
|
|
* when using integers as keys.
|
|
* <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_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>ENFILE - too many databases have been opened. See #mdb_env_set_maxdbs().
|
|
* </ul>
|
|
*/
|
|
int mdb_open(MDB_txn *txn, const char *name, unsigned int flags, MDB_dbi *dbi);
|
|
|
|
/** 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_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);
|
|
|
|
/** Close a database handle.
|
|
* @param[in] txn A transaction handle returned by #mdb_txn_begin()
|
|
* @param[in] dbi A database handle returned by #mdb_open()
|
|
*/
|
|
void mdb_close(MDB_txn *txn, MDB_dbi dbi);
|
|
|
|
/** 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_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 function must be used by every
|
|
* process 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_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);
|
|
|
|
/** 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_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 function must be used by every
|
|
* process 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_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);
|
|
|
|
/** 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_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);
|
|
|
|
/** 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().
|
|
* @param[in] txn A transaction handle returned by #mdb_txn_begin()
|
|
* @param[in] dbi A database handle returned by #mdb_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);
|
|
|
|
/** 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_open()
|
|
* @param[in] key The key to store in the database
|
|
* @param[in] 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).
|
|
* </ul>
|
|
* @return A non-zero error value on failure and 0 on success. Some possible
|
|
* errors are:
|
|
* <ul>
|
|
* <li>EACCESS - an attempt was made to write in a read-only transaction.
|
|
* <li>EINVAL - an invalid parameter was specified.
|
|
* <li>ENOMEM - the database is full, see #mdb_env_set_mapsize().
|
|
* </ul>
|
|
*/
|
|
int mdb_put(MDB_txn *txn, MDB_dbi dbi, MDB_val *key, MDB_val *data,
|
|
unsigned int flags);
|
|
|
|
/** 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_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>EACCESS - 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);
|
|
|
|
/** Create a cursor handle.
|
|
* Cursors are associated with a specific transaction and database and
|
|
* may not span threads.
|
|
* @param[in] txn A transaction handle returned by #mdb_txn_begin()
|
|
* @param[in] dbi A database handle returned by #mdb_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);
|
|
|
|
/** Close a cursor handle.
|
|
* The cursor handle will be freed and must not be used again after this call.
|
|
* @param[in] cursor A cursor handle returned by #mdb_cursor_open()
|
|
*/
|
|
void mdb_cursor_close(MDB_cursor *cursor);
|
|
|
|
/** 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.
|
|
* @bug Cursors are not coordinated with write operations. If a cursor in a
|
|
* write transaction is performing a sequential scan while records are being
|
|
* inserted or deleted in the same transaction, the cursor will be corrupted.
|
|
* @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);
|
|
|
|
/** Store by cursor.
|
|
* This function stores key/data pairs into the database.
|
|
* If the function fails for any reason, the state of the cursor will be
|
|
* unchanged. If the function succeeds and an item is inserted into the
|
|
* database, the cursor is always positioned to refer to the newly inserted item.
|
|
* @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 - overwrite the data of the key/data pair to which
|
|
* the cursor refers with the specified data item. The \b key
|
|
* parameter is ignored.
|
|
* <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).
|
|
* </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_put(MDB_cursor *cursor, MDB_val *key, MDB_val *data,
|
|
unsigned int flags);
|
|
|
|
/** 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);
|
|
|
|
/** 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.
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* </ul>
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*/
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int mdb_cursor_count(MDB_cursor *cursor, unsigned long *countp);
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/** Compare two data items according to a particular database.
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* This returns a comparison as if the two data items were keys in the
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* specified database.
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* @param[in] txn A transaction handle returned by #mdb_txn_begin()
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* @param[in] dbi A database handle returned by #mdb_open()
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* @param[in] a The first item to compare
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* @param[in] b The second item to compare
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* @return < 0 if a < b, 0 if a == b, > 0 if a > b
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*/
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int mdb_cmp(MDB_txn *txn, MDB_dbi dbi, const MDB_val *a, const MDB_val *b);
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/** @} */
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#endif /* _MDB_H_ */
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