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@ -1,7 +1,39 @@ |
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/* mdb.h - memory-mapped database library header file */ |
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/*
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* Copyright 2011 Howard Chu, Symas Corp. |
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* All rights reserved. |
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/** @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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@ -11,6 +43,7 @@ |
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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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@ -32,132 +65,717 @@ |
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#include <sys/types.h> |
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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 8 |
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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 "August 11, 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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struct MDB_cursor; |
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struct MDB_txn; |
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struct MDB_env; |
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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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/** 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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/** 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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/** A handle for an individual database in the DB environment. */ |
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typedef unsigned int MDB_dbi; |
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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; |
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void *mv_data; |
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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. This feature is currently unimplemented. |
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*/ |
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typedef void (MDB_rel_func)(void *ptr, void *oldptr); |
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/** @defgroup mdb_put mdb_put flags
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* @{ |
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*/ |
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/** For mdb_put: don't write if the key already exists. */ |
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#define MDB_NOOVERWRITE 0x10 |
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/** For mdb_put: don't write if the key and data pair already exist.
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* Only for #MDB_DUPSORT |
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*/ |
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#define MDB_NODUPDATA 0x20 |
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#define MDB_DEL_DUP 0x40 |
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typedef enum MDB_cursor_op { /* cursor operations */ |
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MDB_FIRST, |
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MDB_GET_BOTH, /* position at key/data */ |
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MDB_GET_BOTH_RANGE, /* position at key, nearest data */ |
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MDB_GET_MULTIPLE, /* only for MDB_DUPFIXED */ |
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MDB_LAST, |
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MDB_NEXT, |
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MDB_NEXT_DUP, |
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MDB_NEXT_MULTIPLE, /* only for MDB_DUPFIXED */ |
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MDB_NEXT_NODUP, |
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MDB_PREV, |
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MDB_PREV_DUP, |
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MDB_PREV_NODUP, |
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MDB_SET, /* position at key, or fail */ |
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MDB_SET_RANGE /* position at given key */ |
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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_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_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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/* return codes */ |
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/* BerkeleyDB uses -30800 to -30999, we'll go under them */ |
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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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#define MDB_KEYEXIST (-30799) /* key/data pair already exists */ |
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#define MDB_NOTFOUND (-30798) /* key/data pair not found (EOF) */ |
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#define MDB_PAGE_NOTFOUND (-30797) /* Requested page not found */ |
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#define MDB_CORRUPTED (-30796) /* Located page was wrong type */ |
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#define MDB_PANIC (-30795) /* Update of meta page failed, probably I/O error */ |
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#define MDB_VERSION_MISMATCH (-30794) /* Environment version mismatch */ |
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/* DB flags */ |
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#define MDB_REVERSEKEY 0x02 /* use reverse string keys */ |
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#define MDB_DUPSORT 0x04 /* use sorted duplicates */ |
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#define MDB_INTEGERKEY 0x08 /* numeric keys in native byte order */ |
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#define MDB_DUPFIXED 0x10 /* sorted dup items have fixed size */ |
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#define MDB_INTEGERDUP 0x20 /* numeric dups in native byte order */ |
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/* environment flags */ |
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#define MDB_FIXEDMAP 0x01 /* mmap at a fixed address */ |
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#define MDB_NOSYNC 0x10000 /* don't fsync after commit */ |
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#define MDB_RDONLY 0x20000 /* read only */ |
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/* DB or env flags */ |
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#define MDB_CREATE 0x40000 /* create if not present */ |
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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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/** @defgroup mdb_open mdb_open 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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/** @} */ |
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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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/** create env or DB if not already existing */ |
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#define MDB_CREATE 0x40000 |
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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; |
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unsigned int ms_depth; |
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unsigned long ms_branch_pages; |
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unsigned long ms_leaf_pages; |
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unsigned long ms_overflow_pages; |
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unsigned long ms_entries; |
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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 |
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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) |
|
|
|
|
* properties, but not D (durability); that is database integrity will be |
|
|
|
|
* maintained but it is possible some number of the most recently committed |
|
|
|
|
* transactions may be undone after a system crash. The number of transactions |
|
|
|
|
* at risk is governed by how often the system flushes dirty buffers to disk |
|
|
|
|
* and how often #mdb_env_sync() is called. This flag may be changed |
|
|
|
|
* at any time using #mdb_env_set_flags(). |
|
|
|
|
* <li>#MDB_RDONLY |
|
|
|
|
* Open the environment in read-only mode. No write operations will be allowed. |
|
|
|
|
* <li>#MDB_CREATE |
|
|
|
|
* Create the environment if it doesn't already exist. |
|
|
|
|
* </ul> |
|
|
|
|
* @param[in] mode The UNIX permissions to set on created files. |
|
|
|
|
* @return A non-zero error value on failure and 0 on success. Some possible |
|
|
|
|
* errors are: |
|
|
|
|
* <ul> |
|
|
|
|
* <li>#MDB_VERSION_MISMATCH - the version of the MDB library doesn't match the |
|
|
|
|
* version that created the database environment. |
|
|
|
|
* <li>EINVAL - the environment file headers are corrupted. |
|
|
|
|
* <li>ENOENT - the directory specified by the path parameter doesn't exist. |
|
|
|
|
* <li>EACCES - the user didn't have permission to access the environment files. |
|
|
|
|
* <li>EAGAIN - the environment was locked by another process. |
|
|
|
|
* </ul> |
|
|
|
|
*/ |
|
|
|
|
int mdb_env_open(MDB_env *env, const char *path, unsigned int flags, mode_t mode); |
|
|
|
|
|
|
|
|
|
/** Return statistics about the MDB environment.
|
|
|
|
|
* @param[in] env An environment handle returned by #mdb_env_create() |
|
|
|
|
* @param[out] stat The address of an #MDB_stat structure |
|
|
|
|
* where the statistics will be copied |
|
|
|
|
*/ |
|
|
|
|
int mdb_env_stat(MDB_env *env, MDB_stat *stat); |
|
|
|
|
|
|
|
|
|
/** Flush the data buffers to disk.
|
|
|
|
|
* Data is always written to disk when #mdb_txn_commit() is called, |
|
|
|
|
* but the operating system may keep it buffered. MDB always flushes |
|
|
|
|
* the OS buffers upon commit as well, unless the environment was |
|
|
|
|
* opened with #MDB_NOSYNC. |
|
|
|
|
* @param[in] env An environment handle returned by #mdb_env_create() |
|
|
|
|
* @param[in] force If non-zero, force the flush to occur. Otherwise |
|
|
|
|
* if the environment has the #MDB_NOSYNC flag set the flushes |
|
|
|
|
* will be omitted. |
|
|
|
|
* @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>EIO - an error occurred during synchronization. |
|
|
|
|
* </ul> |
|
|
|
|
*/ |
|
|
|
|
int mdb_env_sync(MDB_env *env, int force); |
|
|
|
|
|
|
|
|
|
/** Close the environment and release the memory map.
|
|
|
|
|
* Only a single thread may call this function. All transactions, databases, |
|
|
|
|
* and cursors must already be closed before calling this function. Attempts to |
|
|
|
|
* use any such handles after calling this function will cause a SIGSEGV. |
|
|
|
|
* The environment handle will be freed and must not be used again after this call. |
|
|
|
|
* @param[in] env An environment handle returned by #mdb_env_create() |
|
|
|
|
*/ |
|
|
|
|
void mdb_env_close(MDB_env *env); |
|
|
|
|
|
|
|
|
|
/** Set environment flags.
|
|
|
|
|
* This may be used to set some flags that weren't already set during |
|
|
|
|
* #mdb_env_open(), or to unset these flags. Currently only the |
|
|
|
|
* #MDB_NOSYNC flag setting may be changed with this function. |
|
|
|
|
* @param[in] env An environment handle returned by #mdb_env_create() |
|
|
|
|
* @param[in] flags The flags to change, bitwise OR'ed together |
|
|
|
|
* @param[in] onoff A non-zero value sets the flags, zero clears them. |
|
|
|
|
* @return A non-zero error value on failure and 0 on success. Some possible |
|
|
|
|
* errors are: |
|
|
|
|
* <ul> |
|
|
|
|
* <li>EINVAL - an invalid parameter was specified. |
|
|
|
|
* </ul> |
|
|
|
|
*/ |
|
|
|
|
int mdb_env_set_flags(MDB_env *env, unsigned int flags, int onoff); |
|
|
|
|
|
|
|
|
|
/** Get environment flags.
|
|
|
|
|
* @param[in] env An environment handle returned by #mdb_env_create() |
|
|
|
|
* @param[out] flags The address of an integer to store the flags |
|
|
|
|
* @return A non-zero error value on failure and 0 on success. Some possible |
|
|
|
|
* errors are: |
|
|
|
|
* <ul> |
|
|
|
|
* <li>EINVAL - an invalid parameter was specified. |
|
|
|
|
* </ul> |
|
|
|
|
*/ |
|
|
|
|
int mdb_env_get_flags(MDB_env *env, unsigned int *flags); |
|
|
|
|
|
|
|
|
|
/** Return the path that was used in #mdb_env_open().
|
|
|
|
|
* @param[in] env An environment handle returned by #mdb_env_create() |
|
|
|
|
* @param[out] path Address of a string pointer to contain the path. This |
|
|
|
|
* is the actual string in the environment, not a copy. It should not be |
|
|
|
|
* altered in any way. |
|
|
|
|
* @return A non-zero error value on failure and 0 on success. Some possible |
|
|
|
|
* errors are: |
|
|
|
|
* <ul> |
|
|
|
|
* <li>EINVAL - an invalid parameter was specified. |
|
|
|
|
* </ul> |
|
|
|
|
*/ |
|
|
|
|
int mdb_env_get_path(MDB_env *env, const char **path); |
|
|
|
|
|
|
|
|
|
/** 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 value should be chosen as large as possible, |
|
|
|
|
* to accomodate future growth of the database. |
|
|
|
|
* 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] size The size in bytes |
|
|
|
|
* @return A non-zero error value on failure and 0 on success. Some possible |
|
|
|
|
* errors are: |
|
|
|
|
* <ul> |
|
|
|
|
* <li>EINVAL - an invalid parameter was specified, or the environment is already open. |
|
|
|
|
* </ul> |
|
|
|
|
*/ |
|
|
|
|
int mdb_env_set_mapsize(MDB_env *env, size_t size); |
|
|
|
|
|
|
|
|
|
/** Set the maximum number of threads 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. |
|
|
|
|
* This function may only be called after #mdb_env_create() and before #mdb_env_open(). |
|
|
|
|
* @param[in] env An environment handle returned by #mdb_env_create() |
|
|
|
|
* @param[in] readers The maximum number of threads |
|
|
|
|
* @return A non-zero error value on failure and 0 on success. Some possible |
|
|
|
|
* errors are: |
|
|
|
|
* <ul> |
|
|
|
|
* <li>EINVAL - an invalid parameter was specified, or the environment is already open. |
|
|
|
|
* </ul> |
|
|
|
|
*/ |
|
|
|
|
int mdb_env_set_maxreaders(MDB_env *env, int readers); |
|
|
|
|
|
|
|
|
|
/** Get the maximum number of threads for the environment.
|
|
|
|
|
* @param[in] env An environment handle returned by #mdb_env_create() |
|
|
|
|
* @param[out] readers Address of an integer to store the number of readers |
|
|
|
|
* @return A non-zero error value on failure and 0 on success. Some possible |
|
|
|
|
* errors are: |
|
|
|
|
* <ul> |
|
|
|
|
* <li>EINVAL - an invalid parameter was specified. |
|
|
|
|
* </ul> |
|
|
|
|
*/ |
|
|
|
|
int mdb_env_get_maxreaders(MDB_env *env, int *readers); |
|
|
|
|
|
|
|
|
|
/** 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); |
|
|
|
|
|
|
|
|
|
int mdb_txn_begin(MDB_env *env, int rdonly, MDB_txn **txn); |
|
|
|
|
/** 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); |
|
|
|
|
void mdb_txn_reset(MDB_txn *txn); /* like abort, but doesn't free TXN */ |
|
|
|
|
int mdb_txn_renew(MDB_txn *txn); /* like begin, but doesn't alloc 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() |
|
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*/ |
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void mdb_close(MDB_txn *txn, MDB_dbi dbi); |
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/** Set a custom key comparison function for a database.
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* The comparison function is called whenever it is necessary to compare a |
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* key specified by the application with a key currently stored in the database. |
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* If no comparison function is specified, and no special key flags were specified |
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* with #mdb_open(), the keys are compared lexically, with shorter keys collating |
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* before longer keys. |
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* @warning This function must be called before any data access functions are used, |
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* otherwise data corruption may occur. The same function must be used by every |
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* process accessing the database, every time the database is used. |
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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] cmp A #MDB_cmp_func function |
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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_set_compare(MDB_txn *txn, MDB_dbi dbi, MDB_cmp_func *cmp); |
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/** Set a custom data comparison function for a #MDB_DUPSORT database.
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* This comparison function is called whenever it is necessary to compare a data |
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* item specified by the application with a data item currently stored in the database. |
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* This function only takes effect if the database was opened with the #MDB_DUPSORT |
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* flag. |
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* If no comparison function is specified, and no special key flags were specified |
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* with #mdb_open(), the data items are compared lexically, with shorter items collating |
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* before longer items. |
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* @warning This function must be called before any data access functions are used, |
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* otherwise data corruption may occur. The same function must be used by every |
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* process accessing the database, every time the database is used. |
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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] cmp A #MDB_cmp_func function |
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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_set_dupsort(MDB_txn *txn, MDB_dbi dbi, MDB_cmp_func *cmp); |
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/** Set a relocation function for a #MDB_FIXEDMAP database.
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* @todo The relocation function is called whenever it is necessary to move the data |
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* of an item to a different position in the database (e.g. through tree |
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* balancing operations, shifts as a result of adds or deletes, etc.). It is |
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* intended to allow address/position-dependent data items to be stored in |
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* a database in an environment opened with the #MDB_FIXEDMAP option. |
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* Currently the relocation feature is unimplemented and setting |
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* this function has no effect. |
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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] rel A #MDB_rel_func function |
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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_set_relfunc(MDB_txn *txn, MDB_dbi dbi, MDB_rel_func *rel); |
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/** Get items from a database.
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* This function retrieves key/data pairs from the database. The address |
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* and length of the data associated with the specified \b key are returned |
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* in the structure to which \b data refers. |
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* If the database supports duplicate keys (#MDB_DUPSORT) then the |
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* first data item for the key will be returned. Retrieval of other |
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* items requires the use of #mdb_cursor_get(). |
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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] key The key to search for in the database |
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* @param[out] data The data corresponding to the key |
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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_NOTFOUND - the key was not in the database. |
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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_get(MDB_txn *txn, MDB_dbi dbi, MDB_val *key, MDB_val *data); |
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/** Store items into a database.
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* This function stores key/data pairs in the database. The default behavior |
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* is to enter the new key/data pair, replacing any previously existing key |
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* if duplicates are disallowed, or adding a duplicate data item if |
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* duplicates are allowed (#MDB_DUPSORT). |
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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] key The key to store in the database |
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* @param[in] data The data to store |
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* @param[in] flags Special options for this operation. 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_NODUPDATA - enter the new key/data pair only if it does not |
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* already appear in the database. This flag may only be specified |
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* if the database was opened with #MDB_DUPSORT. The function will |
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* return #MDB_KEYEXIST if the key/data pair already appears in the |
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* database. |
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* <li>#MDB_NOOVERWRITE - enter the new key/data pair only if the key |
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* does not already appear in the database. The function will return |
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* #MDB_KEYEXIST if the key already appears in the database, even if |
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* the database supports duplicates (#MDB_DUPSORT). |
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* </ul> |
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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>EACCESS - an attempt was made to write in a read-only transaction. |
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* <li>EINVAL - an invalid parameter was specified. |
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* <li>ENOMEM - the database is full, see #mdb_env_set_mapsize(). |
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* </ul> |
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*/ |
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int mdb_put(MDB_txn *txn, MDB_dbi dbi, MDB_val *key, MDB_val *data, |
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unsigned int flags); |
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int mdb_del(MDB_txn *txn, MDB_dbi dbi, MDB_val *key, MDB_val *data, |
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unsigned int flags); |
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/** Delete items from a database.
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* This function removes key/data pairs from the database. |
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* If the database does not support sorted duplicate data items |
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* (#MDB_DUPSORT) the data parameter is ignored. |
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* If the database supports sorted duplicates and the data parameter |
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* is NULL, all of the duplicate data items for the key will be |
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* deleted. Otherwise, if the data parameter is non-NULL |
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* only the matching data item will be deleted. |
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* This function will return #MDB_NOTFOUND if the specified key/data |
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* pair is not in the 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] key The key to delete from the database |
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|
* @param[in] data The data to delete |
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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>EACCESS - an attempt was made to write in a read-only transaction. |
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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_del(MDB_txn *txn, MDB_dbi dbi, MDB_val *key, MDB_val *data); |
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/** Create a cursor handle.
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|
* Cursors are associated with a specific transaction and database and |
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* may not span threads. |
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|
* @todo Cursors only support read operations. Support for cursor_put() and |
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|
|
* cursor_del() needs to be added. |
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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[out] cursor Address where the new #MDB_cursor handle will be stored |
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|
* @return A non-zero error value on failure and 0 on success. Some possible |
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|
|
* errors are: |
|
|
|
|
* <ul> |
|
|
|
|
* <li>EINVAL - an invalid parameter was specified. |
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|
|
* </ul> |
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|
*/ |
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int mdb_cursor_open(MDB_txn *txn, MDB_dbi dbi, MDB_cursor **cursor); |
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/** Close a cursor handle.
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|
* The cursor handle will be freed and must not be used again after this call. |
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|
* @param[in] cursor A cursor handle returned by #mdb_cursor_open() |
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|
*/ |
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void mdb_cursor_close(MDB_cursor *cursor); |
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/** Retrieve by cursor.
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|
* This function retrieves key/data pairs from the database. The address and length |
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|
|
* of the key are returned in the object to which \b key refers (except for the |
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|
* case of the #MDB_SET option, in which the \b key object is unchanged), and |
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|
* the address and length of the data are returned in the object to which \b data |
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|
* refers. |
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|
|
* @bug Cursors are not coordinated with write operations. If a cursor in a |
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|
|
* write transaction is performing a sequential scan while records are being |
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|
|
* inserted or deleted in the same transaction, the cursor will be corrupted. |
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|
|
* @param[in] cursor A cursor handle returned by #mdb_cursor_open() |
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|
* @param[in,out] key The key for a retrieved item |
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|
* @param[in,out] data The data of a retrieved item |
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|
* @param[in] op A cursor operation #MDB_cursor_op |
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|
* @return A non-zero error value on failure and 0 on success. Some possible |
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|
|
|
* errors are: |
|
|
|
|
* <ul> |
|
|
|
|
* <li>#MDB_NOTFOUND - no matching key found. |
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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_cursor_get(MDB_cursor *cursor, MDB_val *key, MDB_val *data, |
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|
MDB_cursor_op op); |
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|
/** Return count of duplicates for current key.
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|
* This call is only valid on databases that support sorted duplicate |
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|
* data items #MDB_DUPSORT. |
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|
* @param[in] cursor A cursor handle returned by #mdb_cursor_open() |
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|
* @param[out] countp Address where the count will be stored |
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|
* @return A non-zero error value on failure and 0 on success. Some possible |
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|
|
|
* errors are: |
|
|
|
|
* <ul> |
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|
|
* <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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#endif /* _MDB_H_ */ |
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Howard Chu
14 years ago