-/* mdb.h - memory-mapped database library header file */
-/*
- * Copyright 2011 Howard Chu, Symas Corp.
- * All rights reserved.
+/** @file mdb.h
+ * @brief memory-mapped database library
+ *
+ * @mainpage MDB Memory-Mapped Database Manager
+ * MDB is a Btree-based database management library modeled loosely on the
+ * BerkeleyDB API, but much simplified. The entire database is exposed
+ * in a read-only memory map, and all data fetches return data directly
+ * from the mapped memory, so no malloc's or memcpy's occur during
+ * data fetches. As such, the library is extremely simple because it
+ * requires no page caching layer of its own, and it is extremely high
+ * performance and memory-efficient. It is also fully transactional with
+ * full ACID semantics, and because the memory map is read-only, the
+ * database integrity cannot be corrupted by stray pointer writes from
+ * application code.
+ *
+ * The library is fully thread-aware and supports concurrent read/write
+ * access from multiple processes and threads. Data pages use a copy-on-
+ * write strategy so no active data pages are ever overwritten, which
+ * also provides resistance to corruption and eliminates the need of any
+ * special recovery procedures after a system crash. Writes are fully
+ * serialized; only one write transaction may be active at a time, which
+ * guarantees that writers can never deadlock. The database structure is
+ * multi-versioned so readers run with no locks; writers cannot block
+ * readers, and readers don't block writers.
+ *
+ * Unlike other well-known database mechanisms which use either write-ahead
+ * transaction logs or append-only data writes, MDB requires no maintenance
+ * during operation. Both write-ahead loggers and append-only databases
+ * require periodic checkpointing and/or compaction of their log or database
+ * files otherwise they grow without bound. MDB tracks free pages within
+ * the database and re-uses them for new write operations, so the database
+ * size does not grow without bound in normal use.
+ *
+ * @author Howard Chu, Symas Corporation.
+ *
+ * @copyright Copyright 2011 Howard Chu, Symas Corp. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted only as authorized by the OpenLDAP
* top-level directory of the distribution or, alternatively, at
* <http://www.OpenLDAP.org/license.html>.
*
+ * @par Derived From:
* This code is derived from btree.c written by Martin Hedenfalk.
*
* Copyright (c) 2009, 2010 Martin Hedenfalk <martin@bzero.se>
#include <sys/types.h>
+/** @defgroup Version Version Macros
+ * @{
+ */
+/** Library major version */
#define MDB_VERSION_MAJOR 0
+/** Library minor version */
#define MDB_VERSION_MINOR 8
+/** Library patch version */
#define MDB_VERSION_PATCH 0
+
+/** Combine args a,b,c into a single integer for easy version comparisons */
#define MDB_VERINT(a,b,c) (((a) << 24) | ((b) << 16) | (c))
+
+/** The full library version as a single integer */
#define MDB_VERSION_FULL \
MDB_VERINT(MDB_VERSION_MAJOR,MDB_VERSION_MINOR,MDB_VERSION_PATCH)
+
+/** The release date of this library version */
#define MDB_VERSION_DATE "August 11, 2011"
+
+/** A stringifier for the version info */
#define MDB_VERSTR(a,b,c,d) "MDB " #a "." #b "." #c ": (" #d ")"
+
+/** A helper for the stringifier macro */
#define MDB_VERFOO(a,b,c,d) MDB_VERSTR(a,b,c,d)
+
+/** The full library version as a C string */
#define MDB_VERSION_STRING \
MDB_VERFOO(MDB_VERSION_MAJOR,MDB_VERSION_MINOR,MDB_VERSION_PATCH,MDB_VERSION_DATE)
+/** @} */
-struct MDB_cursor;
-struct MDB_txn;
-struct MDB_env;
-
+/** Opaque structure for navigating through a database */
typedef struct MDB_cursor MDB_cursor;
+
+/** Opaque structure for a transaction handle. All database operations require
+ * a transaction handle. Transactions may be read-only or read-write.
+ */
typedef struct MDB_txn MDB_txn;
+
+/** Opaque structure for a database environment. A DB environment supports multiple
+ * databases, all residing in the same shared-memory map.
+ */
typedef struct MDB_env MDB_env;
+/** A handle for an individual database in the DB environment. */
typedef unsigned int MDB_dbi;
+/** Generic structure used for passing keys and data in and out of the database. */
typedef struct MDB_val {
- size_t mv_size;
- void *mv_data;
+ size_t mv_size; /**< size of the data item */
+ void *mv_data; /**< address of the data item */
} MDB_val;
+/** A callback function used to compare two keys in a database */
typedef int (MDB_cmp_func)(const MDB_val *a, const MDB_val *b);
+
+/** A callback function used to relocate a position-dependent data item
+ * in a fixed-address database. This feature is currently unimplemented.
+ */
typedef void (MDB_rel_func)(void *ptr, void *oldptr);
+/** @defgroup mdb_put mdb_put flags
+ * @{
+ */
+/** For mdb_put: don't write if the key already exists. */
#define MDB_NOOVERWRITE 0x10
+/** For mdb_put: don't write if the key and data pair already exist.
+ * Only for #MDB_DUPSORT
+ */
#define MDB_NODUPDATA 0x20
-#define MDB_DEL_DUP 0x40
-
-typedef enum MDB_cursor_op { /* cursor operations */
- MDB_FIRST,
- MDB_GET_BOTH, /* position at key/data */
- MDB_GET_BOTH_RANGE, /* position at key, nearest data */
- MDB_GET_MULTIPLE, /* only for MDB_DUPFIXED */
- MDB_LAST,
- MDB_NEXT,
- MDB_NEXT_DUP,
- MDB_NEXT_MULTIPLE, /* only for MDB_DUPFIXED */
- MDB_NEXT_NODUP,
- MDB_PREV,
- MDB_PREV_DUP,
- MDB_PREV_NODUP,
- MDB_SET, /* position at key, or fail */
- MDB_SET_RANGE /* position at given key */
+/* @} */
+
+/** Cursor operations */
+typedef enum MDB_cursor_op {
+ MDB_FIRST, /**< Position at first key/data item */
+ MDB_GET_BOTH, /**< Position at key/data pair. Only for #MDB_DUPSORT */
+ MDB_GET_BOTH_RANGE, /**< position at key, nearest data. Only for #MDB_DUPSORT */
+ MDB_GET_MULTIPLE, /**< Return all the duplicate data items at the current
+ cursor position. Only for #MDB_DUPFIXED */
+ MDB_LAST, /**< Position at last key/data item */
+ MDB_NEXT, /**< Position at next data item */
+ MDB_NEXT_DUP, /**< Position at next data item of current key.
+ Only for #MDB_DUPSORT */
+ MDB_NEXT_MULTIPLE, /**< Return all duplicate data items at the next
+ cursor position. Only for #MDB_DUPFIXED */
+ MDB_NEXT_NODUP, /**< Position at first data item of next key.
+ Only for #MDB_DUPSORT */
+ MDB_PREV, /**< Position at previous data item */
+ MDB_PREV_DUP, /**< Position at previous data item of current key.
+ Only for #MDB_DUPSORT */
+ MDB_PREV_NODUP, /**< Position at last data item of previous key.
+ only for #MDB_DUPSORT */
+ MDB_SET, /**< Position at specified key */
+ MDB_SET_RANGE /**< Position at first key greater than or equal to specified key. */
} MDB_cursor_op;
-/* return codes */
-/* BerkeleyDB uses -30800 to -30999, we'll go under them */
+/** @defgroup errors Return Codes
+ *
+ * BerkeleyDB uses -30800 to -30999, we'll go under them
+ * @{
+ */
+ /** Successful result */
#define MDB_SUCCESS 0
-#define MDB_KEYEXIST (-30799) /* key/data pair already exists */
-#define MDB_NOTFOUND (-30798) /* key/data pair not found (EOF) */
-#define MDB_PAGE_NOTFOUND (-30797) /* Requested page not found */
-#define MDB_CORRUPTED (-30796) /* Located page was wrong type */
-#define MDB_PANIC (-30795) /* Update of meta page failed, probably I/O error */
-#define MDB_VERSION_MISMATCH (-30794) /* Environment version mismatch */
-
-/* DB flags */
-#define MDB_REVERSEKEY 0x02 /* use reverse string keys */
-#define MDB_DUPSORT 0x04 /* use sorted duplicates */
-#define MDB_INTEGERKEY 0x08 /* numeric keys in native byte order */
-#define MDB_DUPFIXED 0x10 /* sorted dup items have fixed size */
-#define MDB_INTEGERDUP 0x20 /* numeric dups in native byte order */
-
-/* environment flags */
-#define MDB_FIXEDMAP 0x01 /* mmap at a fixed address */
-#define MDB_NOSYNC 0x10000 /* don't fsync after commit */
-#define MDB_RDONLY 0x20000 /* read only */
-
-/* DB or env flags */
-#define MDB_CREATE 0x40000 /* create if not present */
+ /** key/data pair already exists */
+#define MDB_KEYEXIST (-30799)
+ /** key/data pair not found (EOF) */
+#define MDB_NOTFOUND (-30798)
+ /** Requested page not found - this usually indicates corruption */
+#define MDB_PAGE_NOTFOUND (-30797)
+ /** Located page was wrong type */
+#define MDB_CORRUPTED (-30796)
+ /** Update of meta page failed, probably I/O error */
+#define MDB_PANIC (-30795)
+ /** Environment version mismatch */
+#define MDB_VERSION_MISMATCH (-30794)
+/** @} */
+
+/** @defgroup mdb_open mdb_open flags
+ * @{
+ */
+ /** use reverse string keys */
+#define MDB_REVERSEKEY 0x02
+ /** use sorted duplicates */
+#define MDB_DUPSORT 0x04
+ /** numeric keys in native byte order */
+#define MDB_INTEGERKEY 0x08
+ /** with #MDB_DUPSORT, sorted dup items have fixed size */
+#define MDB_DUPFIXED 0x10
+ /** with #MDB_DUPSORT, dups are numeric in native byte order */
+#define MDB_INTEGERDUP 0x20
+/** @} */
+
+/** @defgroup mdb_env environment flags
+ * @{
+ */
+ /** mmap at a fixed address */
+#define MDB_FIXEDMAP 0x01
+ /** don't fsync after commit */
+#define MDB_NOSYNC 0x10000
+ /** read only */
+#define MDB_RDONLY 0x20000
+/** @} */
+ /** create env or DB if not already existing */
+#define MDB_CREATE 0x40000
+
+/** Statistics for a database in the environment */
typedef struct MDB_stat {
- unsigned int ms_psize;
- unsigned int ms_depth;
- unsigned long ms_branch_pages;
- unsigned long ms_leaf_pages;
- unsigned long ms_overflow_pages;
- unsigned long ms_entries;
+ unsigned int ms_psize; /**< Size of a database page.
+ This is currently the same for all databases. */
+ unsigned int ms_depth; /**< Depth (height) of the B-tree */
+ unsigned long ms_branch_pages; /**< Number of internal (non-leaf) pages */
+ unsigned long ms_leaf_pages; /**< Number of leaf pages */
+ unsigned long ms_overflow_pages; /**< Number of overflow pages */
+ unsigned long ms_entries; /**< Number of data items */
} MDB_stat;
+ /** Return the mdb library version information.
+ * @param[out] major if non-NULL, the library major version number is copied here
+ * @param[out] minor if non-NULL, the library minor version number is copied here
+ * @param[out] patch if non-NULL, the library patch version number is copied here
+ * @retval "version string" The library version as a string
+ */
char *mdb_version(int *major, int *minor, int *patch);
+
+ /** Return a string describing a given error code.
+ * This function is a superset of the ANSI C X3.159-1989 (ANSI C) strerror(3)
+ * function. If the error code is greater than or equal to 0, then the string
+ * returned by the system function strerror(3) is returned. If the error code
+ * is less than 0, an error string corresponding to the MDB library error is
+ * returned. See @ref errors for a list of MDB-specific error codes.
+ * @param[in] err The error code
+ * @retval "error message" The description of the error
+ */
char *mdb_strerror(int err);
+
+ /** Create an MDB environment handle.
+ * This function allocates memory for a #MDB_env structure. To release
+ * the allocated memory and discard the handle, call #mdb_env_close().
+ * Before the handle may be used, it must be opened using #mdb_env_open().
+ * Various other options may also need to be set before opening the handle,
+ * e.g. #mdb_env_set_mapsize(), #mdb_env_set_maxreaders(), #mdb_env_set_maxdbs(),
+ * depending on usage requirements.
+ * @param[out] env The address where the new handle will be stored
+ * @return A non-zero error value on failure and 0 on success.
+ */
int mdb_env_create(MDB_env **env);
+
+ /** Open an environment handle.
+ * If this function fails, #mdb_env_close() must be called to discard the #MDB_env handle.
+ * @param[in] env An environment handle returned by #mdb_env_create()
+ * @param[in] path The directory in which the database files reside
+ * @param[in] flags Special options for this environment. This parameter
+ * must be set to 0 or by bitwise OR'ing together one or more of the
+ * values described here.
+ * <ul>
+ * <li>#MDB_FIXEDMAP
+ * use a fixed address for the mmap region. This flag must be specified
+ * when creating the environment, and is stored persistently in the environment.
+ * If successful, the memory map will always reside at the same virtual address
+ * and pointers used to reference data items in the database will be constant
+ * across multiple invocations. This option may not always work, depending on
+ * how the operating system has allocated memory to shared libraries and other uses.
+ * The feature is highly experimental.
+ * <li>#MDB_NOSYNC
+ * Don't perform a synchronous flush after committing a transaction. This means
+ * 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()
+ */
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);
-int mdb_del(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.
+ * @todo Cursors only support read operations. Support for cursor_put() and
+ * cursor_del() needs to be added.
+ * @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);
+
+ /** Return count of duplicates for current key.
+ * This call is only valid on databases that support sorted duplicate
+ * data items #MDB_DUPSORT.
+ * @param[in] cursor A cursor handle returned by #mdb_cursor_open()
+ * @param[out] countp Address where the count will be stored
+ * @return A non-zero error value on failure and 0 on success. Some possible
+ * errors are:
+ * <ul>
+ * <li>EINVAL - cursor is not initialized, or an invalid parameter was specified.
+ * </ul>
+ */
int mdb_cursor_count(MDB_cursor *cursor, unsigned long *countp);
+ /** Compare two data items according to a particular database.
+ * This returns a comparison as if the two data items were keys in the
+ * specified database.
+ * @param[in] txn A transaction handle returned by #mdb_txn_begin()
+ * @param[in] dbi A database handle returned by #mdb_open()
+ * @param[in] a The first item to compare
+ * @param[in] b The second item to compare
+ * @return < 0 if a < b, 0 if a == b, > 0 if a > b
+ */
int mdb_cmp(MDB_txn *txn, MDB_dbi dbi, const MDB_val *a, const MDB_val *b);
#endif /* _MDB_H_ */
projects / openldap / blobdiff