/* LICENSE AND COPYRUSTING *****************************************************
*
* Copyright 2015-2017 Leonid Yuriev <leo@yuriev.ru>
* and other libmdbx authors: please see AUTHORS file.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted only as authorized by the OpenLDAP
* Public License.
*
* A copy of this license is available in the file LICENSE in the
* top-level directory of the distribution or, alternatively, at
* <http://www.OpenLDAP.org/license.html>.
*
* ---
*
* This code is derived from "LMDB engine" written by
* Howard Chu (Symas Corporation), which itself derived from btree.c
* written by Martin Hedenfalk.
*
* ---
*
* Portions Copyright 2011-2015 Howard Chu, Symas Corp. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted only as authorized by the OpenLDAP
* Public License.
*
* A copy of this license is available in the file LICENSE in the
* top-level directory of the distribution or, alternatively, at
* <http://www.OpenLDAP.org/license.html>.
*
* ---
*
* Portions Copyright (c) 2009, 2010 Martin Hedenfalk <martin@bzero.se>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
/* ACKNOWLEDGEMENTS ************************************************************
*
* Howard Chu (Symas Corporation) - the author of LMDB,
* from which originated the MDBX in 2015.
*
* Martin Hedenfalk <martin@bzero.se> - the author of `btree.c` code,
* which was used for begin development of LMDB. */
#pragma once
#ifndef LIBMDBX_H
#define LIBMDBX_H
/* IMPENDING CHANGES WARNING ***************************************************
*
* Now MDBX is under active development and until November 2017 is expected a
* big change both of API and database format. Unfortunately those update will
* lead to loss of compatibility with previous versions.
*
* The aim of this revolution in providing a clearer robust API and adding new
* features, including the database properties. */
/*--------------------------------------------------------------------------*/
#ifdef _MSC_VER
#pragma warning(push, 1)
#pragma warning(disable : 4548) /* expression before comma has no effect; \
expected expression with side - effect */
#pragma warning(disable : 4530) /* C++ exception handler used, but unwind \
* semantics are not enabled. Specify /EHsc */
#pragma warning(disable : 4577) /* 'noexcept' used with no exception handling \
* mode specified; termination on exception is \
* not guaranteed. Specify /EHsc */
#endif /* _MSC_VER (warnings) */
#include <stdarg.h>
#include <stddef.h>
#include <stdint.h>
#if defined(_WIN32) || defined(_WIN64)
#include <windows.h>
#include <winnt.h>
#ifndef __mode_t_defined
typedef unsigned short mode_t;
#endif
typedef HANDLE mdbx_filehandle_t;
typedef DWORD mdbx_pid_t;
typedef DWORD mdbx_tid_t;
#define MDBX_ENODATA ERROR_HANDLE_EOF
#define MDBX_EINVAL ERROR_INVALID_PARAMETER
#define MDBX_EACCESS ERROR_ACCESS_DENIED
#define MDBX_ENOMEM ERROR_OUTOFMEMORY
#define MDBX_EROFS ERROR_FILE_READ_ONLY
#define MDBX_ENOSYS ERROR_NOT_SUPPORTED
#define MDBX_EIO ERROR_WRITE_FAULT
#define MDBX_EPERM ERROR_INVALID_FUNCTION
#define MDBX_EINTR ERROR_CANCELLED
#else
#include <errno.h> /* for error codes */
#include <pthread.h> /* for pthread_t */
#include <sys/types.h> /* for pid_t */
#include <sys/uio.h> /* for truct iovec */
#define HAVE_STRUCT_IOVEC 1
typedef int mdbx_filehandle_t;
typedef pid_t mdbx_pid_t;
typedef pthread_t mdbx_tid_t;
#define MDBX_ENODATA ENODATA
#define MDBX_EINVAL EINVAL
#define MDBX_EACCESS EACCES
#define MDBX_ENOMEM ENOMEM
#define MDBX_EROFS EROFS
#define MDBX_ENOSYS ENOSYS
#define MDBX_EIO EIO
#define MDBX_EPERM EPERM
#define MDBX_EINTR EINTR
#endif
#ifdef _MSC_VER
#pragma warning(pop)
#endif
/*--------------------------------------------------------------------------*/
#ifndef __has_attribute
#define __has_attribute(x) (0)
#endif
#ifndef __dll_export
#if defined(_WIN32) || defined(__CYGWIN__)
#if defined(__GNUC__) || __has_attribute(dllexport)
#define __dll_export __attribute__((dllexport))
#elif defined(_MSC_VER)
#define __dll_export __declspec(dllexport)
#else
#define __dll_export
#endif
#elif defined(__GNUC__) || __has_attribute(visibility)
#define __dll_export __attribute__((visibility("default")))
#else
#define __dll_export
#endif
#endif /* __dll_export */
#ifndef __dll_import
#if defined(_WIN32) || defined(__CYGWIN__)
#if defined(__GNUC__) || __has_attribute(dllimport)
#define __dll_import __attribute__((dllimport))
#elif defined(_MSC_VER)
#define __dll_import __declspec(dllimport)
#else
#define __dll_import
#endif
#else
#define __dll_import
#endif
#endif /* __dll_import */
/*--------------------------------------------------------------------------*/
#define MDBX_VERSION_MAJOR 0
#define MDBX_VERSION_MINOR 0
#if defined(LIBMDBX_EXPORTS)
#define LIBMDBX_API __dll_export
#elif defined(LIBMDBX_IMPORTS)
#define LIBMDBX_API __dll_import
#else
#define LIBMDBX_API
#endif /* LIBMDBX_API */
#ifdef __cplusplus
extern "C" {
#endif
typedef struct mdbx_version_info {
uint8_t major;
uint8_t minor;
uint16_t release;
uint32_t revision;
struct {
const char *datetime;
const char *tree;
const char *commit;
const char *describe;
} git;
} mdbx_version_info;
typedef struct mdbx_build_info {
const char *datetime;
const char *target;
const char *options;
const char *compiler;
const char *flags;
} mdbx_build_info;
extern LIBMDBX_API const mdbx_version_info mdbx_version;
extern LIBMDBX_API const mdbx_build_info mdbx_build;
/* The name of the lock file in the DB environment */
#define MDBX_LOCKNAME "/mdbx.lck"
/* The name of the data file in the DB environment */
#define MDBX_DATANAME "/mdbx.dat"
/* The suffix of the lock file when no subdir is used */
#define MDBX_LOCK_SUFFIX "-lck"
/* Opaque structure for a database environment.
*
* A DB environment supports multiple databases, all residing in the same
* shared-memory map. */
typedef struct MDBX_env MDBX_env;
/* Opaque structure for a transaction handle.
*
* All database operations require a transaction handle. Transactions may be
* read-only or read-write. */
typedef struct MDBX_txn MDBX_txn;
/* A handle for an individual database in the DB environment. */
typedef uint32_t MDBX_dbi;
/* Opaque structure for navigating through a database */
typedef struct MDBX_cursor MDBX_cursor;
/* Generic structure used for passing keys and data in and out
* of the database.
*
* Values returned from the database are valid only until a subsequent
* update operation, or the end of the transaction. Do not modify or
* free them, they commonly point into the database itself.
*
* Key sizes must be between 1 and mdbx_env_get_maxkeysize() inclusive.
* The same applies to data sizes in databases with the MDBX_DUPSORT flag.
* Other data items can in theory be from 0 to 0xffffffff bytes long. */
#ifndef HAVE_STRUCT_IOVEC
struct iovec {
void *iov_base;
size_t iov_len;
};
#define HAVE_STRUCT_IOVEC
#endif /* HAVE_STRUCT_IOVEC */
typedef struct iovec MDBX_val;
/* The maximum size of a data item.
* MDBX only store a 32 bit value for node sizes. */
#define MDBX_MAXDATASIZE INT32_MAX
/* A callback function used to compare two keys in a database */
typedef int(MDBX_cmp_func)(const MDBX_val *a, const MDBX_val *b);
/* Environment Flags */
/* no environment directory */
#define MDBX_NOSUBDIR 0x4000u
/* don't fsync after commit */
#define MDBX_NOSYNC 0x10000u
/* read only */
#define MDBX_RDONLY 0x20000u
/* don't fsync metapage after commit */
#define MDBX_NOMETASYNC 0x40000u
/* use writable mmap */
#define MDBX_WRITEMAP 0x80000u
/* use asynchronous msync when MDBX_WRITEMAP is used */
#define MDBX_MAPASYNC 0x100000u
/* tie reader locktable slots to MDBX_txn objects instead of to threads */
#define MDBX_NOTLS 0x200000u
/* don't do any locking, caller must manage their own locks
* WARNING: libmdbx don't support this mode. */
#define MDBX_NOLOCK__UNSUPPORTED 0x400000u
/* don't do readahead */
#define MDBX_NORDAHEAD 0x800000u
/* don't initialize malloc'd memory before writing to datafile */
#define MDBX_NOMEMINIT 0x1000000u
/* aim to coalesce FreeDB records */
#define MDBX_COALESCE 0x2000000u
/* LIFO policy for reclaiming FreeDB records */
#define MDBX_LIFORECLAIM 0x4000000u
/* make a steady-sync only on close and explicit env-sync */
#define MDBX_UTTERLY_NOSYNC (MDBX_NOSYNC | MDBX_MAPASYNC)
/* debuging option, fill/perturb released pages */
#define MDBX_PAGEPERTURB 0x8000000u
/* Database Flags */
/* use reverse string keys */
#define MDBX_REVERSEKEY 0x02u
/* use sorted duplicates */
#define MDBX_DUPSORT 0x04u
/* numeric keys in native byte order, either uint32_t or uint64_t.
* The keys must all be of the same size. */
#define MDBX_INTEGERKEY 0x08u
/* with MDBX_DUPSORT, sorted dup items have fixed size */
#define MDBX_DUPFIXED 0x10u
/* with MDBX_DUPSORT, dups are MDBX_INTEGERKEY-style integers */
#define MDBX_INTEGERDUP 0x20u
/* with MDBX_DUPSORT, use reverse string dups */
#define MDBX_REVERSEDUP 0x40u
/* create DB if not already existing */
#define MDBX_CREATE 0x40000u
/* Write Flags */
/* For put: Don't write if the key already exists. */
#define MDBX_NOOVERWRITE 0x10u
/* Only for MDBX_DUPSORT
* For put: don't write if the key and data pair already exist.
* For mdbx_cursor_del: remove all duplicate data items. */
#define MDBX_NODUPDATA 0x20u
/* For mdbx_cursor_put: overwrite the current key/data pair
* MDBX allows this flag for mdbx_put() for explicit overwrite/update without
* insertion. */
#define MDBX_CURRENT 0x40u
/* For put: Just reserve space for data, don't copy it. Return a
* pointer to the reserved space. */
#define MDBX_RESERVE 0x10000u
/* Data is being appended, don't split full pages. */
#define MDBX_APPEND 0x20000u
/* Duplicate data is being appended, don't split full pages. */
#define MDBX_APPENDDUP 0x40000u
/* Store multiple data items in one call. Only for MDBX_DUPFIXED. */
#define MDBX_MULTIPLE 0x80000u
/* Transaction Flags */
/* Do not block when starting a write transaction */
#define MDBX_TRYTXN 0x10000000u
/* Copy Flags */
/* Compacting copy: Omit free space from copy, and renumber all
* pages sequentially. */
#define MDBX_CP_COMPACT 1u
/* Cursor Get operations.
*
* This is the set of all operations for retrieving data
* using a cursor. */
typedef enum MDBX_cursor_op {
MDBX_FIRST, /* Position at first key/data item */
MDBX_FIRST_DUP, /* MDBX_DUPSORT-only: Position at first data item
* of current key. */
MDBX_GET_BOTH, /* MDBX_DUPSORT-only: Position at key/data pair. */
MDBX_GET_BOTH_RANGE, /* MDBX_DUPSORT-only: position at key, nearest data. */
MDBX_GET_CURRENT, /* Return key/data at current cursor position */
MDBX_GET_MULTIPLE, /* MDBX_DUPFIXED-only: Return key and up to a page of
* duplicate data items from current cursor position.
* Move cursor to prepare for MDBX_NEXT_MULTIPLE.*/
MDBX_LAST, /* Position at last key/data item */
MDBX_LAST_DUP, /* MDBX_DUPSORT-only: Position at last data item
* of current key. */
MDBX_NEXT, /* Position at next data item */
MDBX_NEXT_DUP, /* MDBX_DUPSORT-only: Position at next data item
* of current key. */
MDBX_NEXT_MULTIPLE, /* MDBX_DUPFIXED-only: Return key and up to a page of
* duplicate data items from next cursor position.
* Move cursor to prepare for MDBX_NEXT_MULTIPLE. */
MDBX_NEXT_NODUP, /* Position at first data item of next key */
MDBX_PREV, /* Position at previous data item */
MDBX_PREV_DUP, /* MDBX_DUPSORT-only: Position at previous data item
* of current key. */
MDBX_PREV_NODUP, /* Position at last data item of previous key */
MDBX_SET, /* Position at specified key */
MDBX_SET_KEY, /* Position at specified key, return both key and data */
MDBX_SET_RANGE, /* Position at first key greater than or equal to
* specified key. */
MDBX_PREV_MULTIPLE /* MDBX_DUPFIXED-only: Position at previous page and
* return key and up to a page of duplicate data items. */
} MDBX_cursor_op;
/* Return Codes
* BerkeleyDB uses -30800 to -30999, we'll go under them */
/* Successful result */
#define MDBX_SUCCESS 0
#define MDBX_RESULT_FALSE MDBX_SUCCESS
#define MDBX_RESULT_TRUE (-1)
/* key/data pair already exists */
#define MDBX_KEYEXIST (-30799)
/* key/data pair not found (EOF) */
#define MDBX_NOTFOUND (-30798)
/* Requested page not found - this usually indicates corruption */
#define MDBX_PAGE_NOTFOUND (-30797)
/* Located page was wrong type */
#define MDBX_CORRUPTED (-30796)
/* Update of meta page failed or environment had fatal error */
#define MDBX_PANIC (-30795)
/* DB file version mismatch with libmdbx */
#define MDBX_VERSION_MISMATCH (-30794)
/* File is not a valid MDBX file */
#define MDBX_INVALID (-30793)
/* Environment mapsize reached */
#define MDBX_MAP_FULL (-30792)
/* Environment maxdbs reached */
#define MDBX_DBS_FULL (-30791)
/* Environment maxreaders reached */
#define MDBX_READERS_FULL (-30790)
/* Txn has too many dirty pages */
#define MDBX_TXN_FULL (-30788)
/* Cursor stack too deep - internal error */
#define MDBX_CURSOR_FULL (-30787)
/* Page has not enough space - internal error */
#define MDBX_PAGE_FULL (-30786)
/* Database contents grew beyond environment mapsize */
#define MDBX_MAP_RESIZED (-30785)
/* Operation and DB incompatible, or DB type changed. This can mean:
* - The operation expects an MDBX_DUPSORT / MDBX_DUPFIXED database.
* - Opening a named DB when the unnamed DB has MDBX_DUPSORT/MDBX_INTEGERKEY.
* - Accessing a data record as a database, or vice versa.
* - The database was dropped and recreated with different flags. */
#define MDBX_INCOMPATIBLE (-30784)
/* Invalid reuse of reader locktable slot */
#define MDBX_BAD_RSLOT (-30783)
/* Transaction must abort, has a child, or is invalid */
#define MDBX_BAD_TXN (-30782)
/* Unsupported size of key/DB name/data, or wrong DUPFIXED size */
#define MDBX_BAD_VALSIZE (-30781)
/* The specified DBI was changed unexpectedly */
#define MDBX_BAD_DBI (-30780)
/* Unexpected problem - txn should abort */
#define MDBX_PROBLEM (-30779)
/* Another write transaction is running */
#define MDBX_BUSY (-30778)
/* The last defined error code */
#define MDBX_LAST_ERRCODE MDBX_BUSY
/* The mdbx_put() or mdbx_replace() was called for key,
that has more that one associated value. */
#define MDBX_EMULTIVAL (-30421)
/* Bad signature of a runtime object(s), this can mean:
* - memory corruption or double-free;
* - ABI version mismatch (rare case); */
#define MDBX_EBADSIGN (-30420)
/* Database should be recovered, but this could NOT be done automatically
* right now (e.g. in readonly mode and so forth). */
#define MDBX_WANNA_RECOVERY (-30419)
/* The given key value is mismatched to the current cursor position,
* when mdbx_cursor_put() called with MDBX_CURRENT option. */
#define MDBX_EKEYMISMATCH (-30418)
/* Database is too large for current system,
* e.g. could NOT be mapped into RAM. */
#define MDBX_TOO_LARGE (-30417)
/* A thread has attempted to use a not owned object,
* e.g. a transaction that started by another thread. */
#define MDBX_THREAD_MISMATCH (-30416)
/* Statistics for a database in the environment */
typedef struct MDBX_stat {
uint32_t ms_psize; /* Size of a database page.
* This is currently the same for all databases. */
uint32_t ms_depth; /* Depth (height) of the B-tree */
uint64_t ms_branch_pages; /* Number of internal (non-leaf) pages */
uint64_t ms_leaf_pages; /* Number of leaf pages */
uint64_t ms_overflow_pages; /* Number of overflow pages */
uint64_t ms_entries; /* Number of data items */
} MDBX_stat;
/* Information about the environment */
typedef struct MDBX_envinfo {
struct {
uint64_t lower; /* lower limit for datafile size */
uint64_t upper; /* upper limit for datafile size */
uint64_t current; /* current datafile size */
uint64_t shrink; /* shrink theshold for datafile */
uint64_t grow; /* growth step for datafile */
} mi_geo;
uint64_t mi_mapsize; /* Size of the data memory map */
uint64_t mi_last_pgno; /* ID of the last used page */
uint64_t mi_recent_txnid; /* ID of the last committed transaction */
uint64_t mi_latter_reader_txnid; /* ID of the last reader transaction */
uint64_t mi_meta0_txnid, mi_meta0_sign;
uint64_t mi_meta1_txnid, mi_meta1_sign;
uint64_t mi_meta2_txnid, mi_meta2_sign;
uint32_t mi_maxreaders; /* max reader slots in the environment */
uint32_t mi_numreaders; /* max reader slots used in the environment */
uint32_t mi_dxb_pagesize; /* database pagesize */
uint32_t mi_sys_pagesize; /* system pagesize */
} MDBX_envinfo;
/* 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 MDBX library error is
* returned. See errors for a list of MDBX-specific error codes.
*
* [in] err The error code
*
* Returns "error message" The description of the error */
LIBMDBX_API const char *mdbx_strerror(int errnum);
LIBMDBX_API const char *mdbx_strerror_r(int errnum, char *buf, size_t buflen);
/* Create an MDBX environment handle.
*
* This function allocates memory for a MDBX_env structure. To release
* the allocated memory and discard the handle, call mdbx_env_close().
* Before the handle may be used, it must be opened using mdbx_env_open().
* Various other options may also need to be set before opening the handle,
* e.g. mdbx_env_set_mapsize(), mdbx_env_set_maxreaders(),
* mdbx_env_set_maxdbs(), depending on usage requirements.
*
* [out] env The address where the new handle will be stored
*
* Returns A non-zero error value on failure and 0 on success. */
LIBMDBX_API int mdbx_env_create(MDBX_env **penv);
/* Open an environment handle.
*
* If this function fails, mdbx_env_close() must be called to discard
* the MDBX_env handle.
*
* [in] env An environment handle returned by mdbx_env_create()
* [in] path The directory in which the database files reside.
* This directory must already exist and be writable.
* [in] flags Special options for this environment. This parameter
* must be set to 0 or by bitwise OR'ing together one
* or more of the values described here.
*
* Flags set by mdbx_env_set_flags() are also used:
* - MDBX_NOSUBDIR
* By default, MDBX creates its environment in a directory whose
* pathname is given in path, and creates its data and lock files
* under that directory. With this option, path is used as-is for
* the database main data file. The database lock file is the path
* with "-lock" appended.
*
* - MDBX_RDONLY
* Open the environment in read-only mode. No write operations will
* be allowed. MDBX will still modify the lock file - except on
* read-only filesystems, where MDBX does not use locks.
*
* - MDBX_WRITEMAP
* Use a writeable memory map unless MDBX_RDONLY is set. This uses fewer
* mallocs but loses protection from application bugs like wild pointer
* writes and other bad updates into the database.
* This may be slightly faster for DBs that fit entirely in RAM,
* but is slower for DBs larger than RAM.
* Incompatible with nested transactions.
* Do not mix processes with and without MDBX_WRITEMAP on the same
* environment. This can defeat durability (mdbx_env_sync etc).
*
* - MDBX_NOMETASYNC
* Flush system buffers to disk only once per transaction, omit the
* metadata flush. Defer that until the system flushes files to disk,
* or next non-MDBX_RDONLY commit or mdbx_env_sync(). This optimization
* maintains database integrity, but a system crash may undo the last
* committed transaction. I.e. it preserves the ACI (atomicity,
* consistency, isolation) but not D (durability) database property.
* This flag may be changed at any time using mdbx_env_set_flags().
*
* - MDBX_NOSYNC
* Don't flush system buffers to disk when committing a transaction.
* This optimization means a system crash can corrupt the database or
* lose the last transactions if buffers are not yet flushed to disk.
* The risk is governed by how often the system flushes dirty buffers
* to disk and how often mdbx_env_sync() is called. However, if the
* filesystem preserves write order and the MDBX_WRITEMAP and/or
* MDBX_LIFORECLAIM flags are not used, transactions exhibit ACI
* (atomicity, consistency, isolation) properties and only lose D
* (durability). I.e. database integrity is maintained, but a system
* crash may undo the final transactions.
*
* Note that (MDBX_NOSYNC | MDBX_WRITEMAP) leaves the system with no
* hint for when to write transactions to disk.
* Therefore the (MDBX_MAPASYNC | MDBX_WRITEMAP) may be preferable.
* This flag may be changed at any time using mdbx_env_set_flags().
*
* - MDBX_UTTERLY_NOSYNC (internally MDBX_NOSYNC | MDBX_MAPASYNC)
* FIXME: TODO
*
* - MDBX_MAPASYNC
* When using MDBX_WRITEMAP, use asynchronous flushes to disk. As with
* MDBX_NOSYNC, a system crash can then corrupt the database or lose
* the last transactions. Calling mdbx_env_sync() ensures on-disk
* database integrity until next commit. This flag may be changed at
* any time using mdbx_env_set_flags().
*
* - MDBX_NOTLS
* Don't use Thread-Local Storage. Tie reader locktable slots to
* MDBX_txn objects instead of to threads. I.e. mdbx_txn_reset() keeps
* the slot reseved for the MDBX_txn object. A thread may use parallel
* read-only transactions. A read-only transaction may span threads if
* the user synchronizes its use. Applications that multiplex many
* user threads over individual OS threads need this option. Such an
* application must also serialize the write transactions in an OS
* thread, since MDBX's write locking is unaware of the user threads.
*
* - MDBX_NOLOCK (don't supported by MDBX)
* Don't do any locking. If concurrent access is anticipated, the
* caller must manage all concurrency itself. For proper operation
* the caller must enforce single-writer semantics, and must ensure
* that no readers are using old transactions while a writer is
* active. The simplest approach is to use an exclusive lock so that
* no readers may be active at all when a writer begins.
*
* - MDBX_NORDAHEAD
* Turn off readahead. Most operating systems perform readahead on
* read requests by default. This option turns it off if the OS
* supports it. Turning it off may help random read performance
* when the DB is larger than RAM and system RAM is full.
*
* - MDBX_NOMEMINIT
* Don't initialize malloc'd memory before writing to unused spaces
* in the data file. By default, memory for pages written to the data
* file is obtained using malloc. While these pages may be reused in
* subsequent transactions, freshly malloc'd pages will be initialized
* to zeroes before use. This avoids persisting leftover data from other
* code (that used the heap and subsequently freed the memory) into the
* data file. Note that many other system libraries may allocate and free
* memory from the heap for arbitrary uses. E.g., stdio may use the heap
* for file I/O buffers. This initialization step has a modest performance
* cost so some applications may want to disable it using this flag. This
* option can be a problem for applications which handle sensitive data
* like passwords, and it makes memory checkers like Valgrind noisy. This
* flag is not needed with MDBX_WRITEMAP, which writes directly to the
* mmap instead of using malloc for pages. The initialization is also
* skipped if MDBX_RESERVE is used; the caller is expected to overwrite
* all of the memory that was reserved in that case. This flag may be
* changed at any time using mdbx_env_set_flags().
*
* - MDBX_COALESCE
* Aim to coalesce records while reclaiming FreeDB. This flag may be
* changed at any time using mdbx_env_set_flags().
* FIXME: TODO
*
* - MDBX_LIFORECLAIM
* LIFO policy for reclaiming FreeDB records. This significantly reduce
* write IPOs in case MDBX_NOSYNC with periodically checkpoints.
* FIXME: TODO
*
* [in] mode The UNIX permissions to set on created files.
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_VERSION_MISMATCH - the version of the MDBX library doesn't match the
* version that created the database environment.
* - MDBX_INVALID - the environment file headers are corrupted.
* - MDBX_ENOENT - the directory specified by the path parameter
* doesn't exist.
* - MDBX_EACCES - the user didn't have permission to access
* the environment files.
* - MDBX_EAGAIN - the environment was locked by another process. */
LIBMDBX_API int mdbx_env_open(MDBX_env *env, const char *path, unsigned flags,
mode_t mode);
LIBMDBX_API int mdbx_env_open_ex(MDBX_env *env, const char *path,
unsigned flags, mode_t mode, int *exclusive);
/* Copy an MDBX environment to the specified path, with options.
*
* This function may be used to make a backup of an existing environment.
* No lockfile is created, since it gets recreated at need.
* NOTE: This call can trigger significant file size growth if run in
* parallel with write transactions, because it employs a read-only
* transaction. See long-lived transactions under "Caveats" section.
*
* [in] env An environment handle returned by mdbx_env_create(). It must
* have already been opened successfully.
* [in] path The directory in which the copy will reside. This directory
* must already exist and be writable but must otherwise be empty.
* [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:
*
* - MDBX_CP_COMPACT
* Perform compaction while copying: omit free pages and sequentially
* renumber all pages in output. This option consumes little bit more
* CPU for processing, but may running quickly than the default, on
* account skipping free pages.
*
* NOTE: Currently it fails if the environment has suffered a page leak.
*
* Returns A non-zero error value on failure and 0 on success. */
LIBMDBX_API int mdbx_env_copy(MDBX_env *env, const char *path, unsigned flags);
/* Copy an MDBX environment to the specified file descriptor,
* with options.
*
* This function may be used to make a backup of an existing environment.
* No lockfile is created, since it gets recreated at need. See
* mdbx_env_copy() for further details.
*
* NOTE: This call can trigger significant file size growth if run in
* parallel with write transactions, because it employs a read-only
* transaction. See long-lived transactions under "Caveats" section.
*
* [in] env An environment handle returned by mdbx_env_create(). It must
* have already been opened successfully.
* [in] fd The filedescriptor to write the copy to. It must have already
* been opened for Write access.
* [in] flags Special options for this operation. See mdbx_env_copy() for
* options.
*
* Returns A non-zero error value on failure and 0 on success. */
LIBMDBX_API int mdbx_env_copy2fd(MDBX_env *env, mdbx_filehandle_t fd,
unsigned flags);
/* Return statistics about the MDBX environment.
*
* [in] env An environment handle returned by mdbx_env_create()
* [out] stat The address of an MDBX_stat structure where the statistics
* will be copied */
LIBMDBX_API int mdbx_env_stat(MDBX_env *env, MDBX_stat *stat, size_t bytes);
/* Return information about the MDBX environment.
*
* [in] env An environment handle returned by mdbx_env_create()
* [out] stat The address of an MDBX_envinfo structure
* where the information will be copied */
LIBMDBX_API int mdbx_env_info(MDBX_env *env, MDBX_envinfo *info, size_t bytes);
/* Flush the data buffers to disk.
*
* Data is always written to disk when mdbx_txn_commit() is called,
* but the operating system may keep it buffered. MDBX always flushes
* the OS buffers upon commit as well, unless the environment was
* opened with MDBX_NOSYNC or in part MDBX_NOMETASYNC. This call is
* not valid if the environment was opened with MDBX_RDONLY.
*
* [in] env An environment handle returned by mdbx_env_create()
* [in] force If non-zero, force a synchronous flush. Otherwise if the
* environment has the MDBX_NOSYNC flag set the flushes will be
* omitted, and with MDBX_MAPASYNC they will be asynchronous.
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_EACCES - the environment is read-only.
* - MDBX_EINVAL - an invalid parameter was specified.
* - MDBX_EIO - an error occurred during synchronization. */
LIBMDBX_API int mdbx_env_sync(MDBX_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.
*
* [in] env An environment handle returned by mdbx_env_create()
* [in] dont_sync A dont'sync flag, if non-zero the last checkpoint (meta-page
* update) will be kept "as is" and may be still "weak" in the
* NOSYNC/MAPASYNC modes. Such "weak" checkpoint will be
* ignored on opening next time, and transactions since the
* last non-weak checkpoint (meta-page update) will rolledback
* for consistency guarantee. */
LIBMDBX_API int mdbx_env_close(MDBX_env *env);
/* Set environment flags.
*
* This may be used to set some flags in addition to those from
* mdbx_env_open(), or to unset these flags. If several threads
* change the flags at the same time, the result is undefined.
*
* [in] env An environment handle returned by mdbx_env_create()
* [in] flags The flags to change, bitwise OR'ed together
* [in] onoff A non-zero value sets the flags, zero clears them.
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_EINVAL - an invalid parameter was specified. */
LIBMDBX_API int mdbx_env_set_flags(MDBX_env *env, unsigned flags, int onoff);
/* Get environment flags.
*
* [in] env An environment handle returned by mdbx_env_create()
* [out] flags The address of an integer to store the flags
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_EINVAL - an invalid parameter was specified. */
LIBMDBX_API int mdbx_env_get_flags(MDBX_env *env, unsigned *flags);
/* Return the path that was used in mdbx_env_open().
*
* [in] env An environment handle returned by mdbx_env_create()
* [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.
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_EINVAL - an invalid parameter was specified. */
LIBMDBX_API int mdbx_env_get_path(MDBX_env *env, const char **path);
/* Return the file descriptor for the given environment.
*
* NOTE: All MDBX file descriptors have FD_CLOEXEC and
* could't be used after exec() and or fork().
*
* [in] env An environment handle returned by mdbx_env_create()
* [out] fd Address of a int to contain the descriptor.
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_EINVAL - an invalid parameter was specified. */
LIBMDBX_API int mdbx_env_get_fd(MDBX_env *env, mdbx_filehandle_t *fd);
/* Set the size of the memory map to use for this environment.
*
* The size should be a multiple of the OS page size. The default is
* 10485760 bytes. The size of the memory map is also the maximum size
* of the database. The value should be chosen as large as possible,
* to accommodate future growth of the database.
* This function should be called after mdbx_env_create() and before
* mdbx_env_open(). It may be called at later times if no transactions
* are active in this process. Note that the library does not check for
* this condition, the caller must ensure it explicitly.
*
* The new size takes effect immediately for the current process but
* will not be persisted to any others until a write transaction has been
* committed by the current process. Also, only mapsize increases are
* persisted into the environment.
*
* If the mapsize is increased by another process, and data has grown
* beyond the range of the current mapsize, mdbx_txn_begin() will
* return MDBX_MAP_RESIZED. This function may be called with a size
* of zero to adopt the new size.
*
* Any attempt to set a size smaller than the space already consumed by the
* environment will be silently changed to the current size of the used space.
*
* [in] env An environment handle returned by mdbx_env_create()
* [in] size The size in bytes
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_EINVAL - an invalid parameter was specified,
* or the environment has an active write transaction. */
LIBMDBX_API int mdbx_env_set_mapsize(MDBX_env *env, size_t size);
LIBMDBX_API int mdbx_env_set_geometry(MDBX_env *env, intptr_t size_lower,
intptr_t size_now, intptr_t size_upper,
intptr_t growth_step,
intptr_t shrink_threshold,
intptr_t pagesize);
/* Set the maximum number of threads/reader slots for the environment.
*
* This defines the number of slots in the lock table that is used to track
* readers in the the environment. The default is 61.
* Starting a read-only transaction normally ties a lock table slot to the
* current thread until the environment closes or the thread exits. If
* MDBX_NOTLS is in use, mdbx_txn_begin() instead ties the slot to the
* MDBX_txn object until it or the MDBX_env object is destroyed.
* This function may only be called after mdbx_env_create() and before
* mdbx_env_open().
*
* [in] env An environment handle returned by mdbx_env_create()
* [in] readers The maximum number of reader lock table slots
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_EINVAL - an invalid parameter was specified,
* or the environment is already open. */
LIBMDBX_API int mdbx_env_set_maxreaders(MDBX_env *env, unsigned readers);
/* Get the maximum number of threads/reader slots for the environment.
*
* [in] env An environment handle returned by mdbx_env_create()
* [out] readers Address of an integer to store the number of readers
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_EINVAL - an invalid parameter was specified. */
LIBMDBX_API int mdbx_env_get_maxreaders(MDBX_env *env, unsigned *readers);
/* Set the maximum number of named databases for the environment.
*
* This function is only needed if multiple databases will be used in the
* environment. Simpler applications that use the environment as a single
* unnamed database can ignore this option.
* This function may only be called after mdbx_env_create() and before
* mdbx_env_open().
*
* Currently a moderate number of slots are cheap but a huge number gets
* expensive: 7-120 words per transaction, and every mdbx_dbi_open()
* does a linear search of the opened slots.
*
* [in] env An environment handle returned by mdbx_env_create()
* [in] dbs The maximum number of databases
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_EINVAL - an invalid parameter was specified,
* or the environment is already open. */
LIBMDBX_API int mdbx_env_set_maxdbs(MDBX_env *env, MDBX_dbi dbs);
/* Get the maximum size of keys and MDBX_DUPSORT data we can write.
*
* [in] env An environment handle returned by mdbx_env_create()
*
* Returns The maximum size of a key we can write. */
LIBMDBX_API int mdbx_env_get_maxkeysize(MDBX_env *env);
LIBMDBX_API int mdbx_get_maxkeysize(size_t pagesize);
/* Set application information associated with the MDBX_env.
*
* [in] env An environment handle returned by mdbx_env_create()
* [in] ctx An arbitrary pointer for whatever the application needs.
*
* Returns A non-zero error value on failure and 0 on success. */
LIBMDBX_API int mdbx_env_set_userctx(MDBX_env *env, void *ctx);
/* Get the application information associated with the MDBX_env.
*
* [in] env An environment handle returned by mdbx_env_create()
* Returns The pointer set by mdbx_env_set_userctx(). */
LIBMDBX_API void *mdbx_env_get_userctx(MDBX_env *env);
/* A callback function for most MDBX assert() failures,
* called before printing the message and aborting.
*
* [in] env An environment handle returned by mdbx_env_create().
* [in] msg The assertion message, not including newline. */
typedef void MDBX_assert_func(const MDBX_env *env, const char *msg,
const char *function, unsigned line);
/* Set or reset the assert() callback of the environment.
*
* Disabled if libmdbx is buillt with MDBX_DEBUG=0.
* NOTE: This hack should become obsolete as mdbx's error handling matures.
*
* [in] env An environment handle returned by mdbx_env_create().
* [in] func An MDBX_assert_func function, or 0.
*
* Returns A non-zero error value on failure and 0 on success. */
LIBMDBX_API int mdbx_env_set_assert(MDBX_env *env, MDBX_assert_func *func);
/* Create a transaction for use with the environment.
*
* The transaction handle may be discarded using mdbx_txn_abort()
* or mdbx_txn_commit().
* NOTE: A transaction and its cursors must only be used by a single
* thread, and a thread may only have a single transaction at a time.
* If MDBX_NOTLS is in use, this does not apply to read-only transactions.
* NOTE: Cursors may not span transactions.
*
* [in] env An environment handle returned by mdbx_env_create()
* [in] parent If this parameter is non-NULL, the new transaction will be
* a nested transaction, with the transaction indicated by parent
* as its parent. Transactions may be nested to any level.
* A parent transaction and its cursors may not issue any other
* operations than mdbx_txn_commit and mdbx_txn_abort while it
* has active child transactions.
* [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.
*
* - MDBX_RDONLY
* This transaction will not perform any write operations.
*
* - MDBX_TRYTXN
* Do not block when starting a write transaction
*
* [out] txn Address where the new MDBX_txn handle will be stored
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_PANIC - a fatal error occurred earlier and the environment
* must be shut down.
* - MDBX_MAP_RESIZED - another process wrote data beyond this MDBX_env's
* mapsize and this environment's map must be resized
* as well. See mdbx_env_set_mapsize().
* - MDBX_READERS_FULL - a read-only transaction was requested and the reader
* lock table is full. See mdbx_env_set_maxreaders().
* - MDBX_ENOMEM - out of memory.
* - MDBX_BUSY - a write transaction is already started. */
LIBMDBX_API int mdbx_txn_begin(MDBX_env *env, MDBX_txn *parent, unsigned flags,
MDBX_txn **txn);
/* Returns the transaction's MDBX_env
*
* [in] txn A transaction handle returned by mdbx_txn_begin() */
LIBMDBX_API MDBX_env *mdbx_txn_env(MDBX_txn *txn);
/* Return the transaction's ID.
*
* This returns the identifier associated with this transaction. For a
* read-only transaction, this corresponds to the snapshot being read;
* concurrent readers will frequently have the same transaction ID.
*
* [in] txn A transaction handle returned by mdbx_txn_begin()
*
* Returns A transaction ID, valid if input is an active transaction. */
LIBMDBX_API uint64_t mdbx_txn_id(MDBX_txn *txn);
/* Commit all the operations of a transaction into the database.
*
* The transaction handle is freed. It and its cursors must not be used
* again after this call, except with mdbx_cursor_renew().
*
* A cursor must be closed explicitly always, before
* or after its transaction ends. It can be reused with
* mdbx_cursor_renew() before finally closing it.
*
* [in] txn A transaction handle returned by mdbx_txn_begin()
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_EINVAL - an invalid parameter was specified.
* - MDBX_ENOSPC - no more disk space.
* - MDBX_EIO - a low-level I/O error occurred while writing.
* - MDBX_ENOMEM - out of memory. */
LIBMDBX_API int mdbx_txn_commit(MDBX_txn *txn);
/* Abandon all the operations of the transaction instead of saving them.
*
* The transaction handle is freed. It and its cursors must not be used
* again after this call, except with mdbx_cursor_renew().
*
* A cursor must be closed explicitly always, before or after its transaction
* ends. It can be reused with mdbx_cursor_renew() before finally closing it.
*
* [in] txn A transaction handle returned by mdbx_txn_begin(). */
LIBMDBX_API int mdbx_txn_abort(MDBX_txn *txn);
/* Reset a read-only transaction.
*
* Abort the transaction like mdbx_txn_abort(), but keep the transaction
* handle. Therefore mdbx_txn_renew() may reuse the handle. This saves
* allocation overhead if the process will start a new read-only transaction
* soon, and also locking overhead if MDBX_NOTLS is in use. The reader table
* lock is released, but the table slot stays tied to its thread or
* MDBX_txn. Use mdbx_txn_abort() to discard a reset handle, and to free
* its lock table slot if MDBX_NOTLS is in use.
*
* Cursors opened within the transaction must not be used
* again after this call, except with mdbx_cursor_renew().
*
* Reader locks generally don't interfere with writers, but they keep old
* versions of database pages allocated. Thus they prevent the old pages
* from being reused when writers commit new data, and so under heavy load
* the database size may grow much more rapidly than otherwise.
*
* [in] txn A transaction handle returned by mdbx_txn_begin() */
LIBMDBX_API int mdbx_txn_reset(MDBX_txn *txn);
/* Renew a read-only transaction.
*
* This acquires a new reader lock for a transaction handle that had been
* released by mdbx_txn_reset(). It must be called before a reset transaction
* may be used again.
*
* [in] txn A transaction handle returned by mdbx_txn_begin()
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_PANIC - a fatal error occurred earlier and the environment
* must be shut down.
* - MDBX_EINVAL - an invalid parameter was specified. */
LIBMDBX_API int mdbx_txn_renew(MDBX_txn *txn);
/* Open a table in the environment.
*
* A table handle denotes the name and parameters of a table, independently
* of whether such a table exists. The table handle may be discarded by
* calling mdbx_dbi_close(). The old table handle is returned if the table
* was already open. The handle may only be closed once.
*
* The table handle will be private to the current transaction until
* the transaction is successfully committed. If the transaction is
* aborted the handle will be closed automatically.
* After a successful commit the handle will reside in the shared
* environment, and may be used by other transactions.
*
* This function must not be called from multiple concurrent
* transactions in the same process. A transaction that uses
* this function must finish (either commit or abort) before
* any other transaction in the process may use this function.
*
* To use named table (with name != NULL), mdbx_env_set_maxdbs()
* must be called before opening the environment. Table names are
* keys in the internal unnamed table, and may be read but not written.
*
* [in] txn transaction handle returned by mdbx_txn_begin()
* [in] name The name of the table to open. If only a single
* table is needed in the environment, this value may be NULL.
* [in] flags Special options for this table. This parameter must be set
* to 0 or by bitwise OR'ing together one or more of the values
* described here:
* - MDBX_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.
* - MDBX_DUPSORT
* Duplicate keys may be used in the table. Or, from another point of
* view, keys may have multiple data items, stored in sorted order. By
* default keys must be unique and may have only a single data item.
* - MDBX_INTEGERKEY
* Keys are binary integers in native byte order, either uin32_t or
* uint64_t, and will be sorted as such. The keys must all be of the
* same size.
* - MDBX_DUPFIXED
* This flag may only be used in combination with MDBX_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 MDBX_GET_MULTIPLE,
* MDBX_NEXT_MULTIPLE and MDBX_PREV_MULTIPLE cursor operations may be used
* to retrieve multiple items at once.
* - MDBX_INTEGERDUP
* This option specifies that duplicate data items are binary integers,
* similar to MDBX_INTEGERKEY keys.
* - MDBX_REVERSEDUP
* This option specifies that duplicate data items should be compared as
* strings in reverse order (the comparison is performed in the direction
* from the last byte to the first).
* - MDBX_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.
*
* [out] dbi Address where the new MDBX_dbi handle will be stored
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_NOTFOUND - the specified database doesn't exist in the
* environment and MDBX_CREATE was not specified.
* - MDBX_DBS_FULL - too many databases have been opened.
* See mdbx_env_set_maxdbs(). */
LIBMDBX_API int mdbx_dbi_open_ex(MDBX_txn *txn, const char *name,
unsigned flags, MDBX_dbi *dbi,
MDBX_cmp_func *keycmp, MDBX_cmp_func *datacmp);
LIBMDBX_API int mdbx_dbi_open(MDBX_txn *txn, const char *name, unsigned flags,
MDBX_dbi *dbi);
/* Retrieve statistics for a database.
*
* [in] txn A transaction handle returned by mdbx_txn_begin()
* [in] dbi A database handle returned by mdbx_dbi_open()
* [out] stat The address of an MDBX_stat structure where the statistics
* will be copied
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_EINVAL - an invalid parameter was specified. */
LIBMDBX_API int mdbx_dbi_stat(MDBX_txn *txn, MDBX_dbi dbi, MDBX_stat *stat,
size_t bytes);
/* Retrieve the DB flags for a database handle.
*
* [in] txn A transaction handle returned by mdbx_txn_begin()
* [in] dbi A database handle returned by mdbx_dbi_open()
* [out] flags Address where the flags will be returned.
* [out] state Address where the state will be returned.
*
* Returns A non-zero error value on failure and 0 on success. */
#define MDBX_TBL_DIRTY 0x01 /* DB was written in this txn */
#define MDBX_TBL_STALE 0x02 /* Named-DB record is older than txnID */
#define MDBX_TBL_NEW 0x04 /* Named-DB handle opened in this txn */
LIBMDBX_API int mdbx_dbi_flags_ex(MDBX_txn *txn, MDBX_dbi dbi, unsigned *flags,
unsigned *state);
LIBMDBX_API int mdbx_dbi_flags(MDBX_txn *txn, MDBX_dbi dbi, unsigned *flags);
/* Close a database handle. Normally unnecessary.
*
* Use with care:
* FIXME: This call is not mutex protected. Handles should only be closed by
* a single thread, and only if no other threads are going to reference
* the database handle or one of its cursors any further. Do not close
* a handle if an existing transaction has modified its database.
* Doing so can cause misbehavior from database corruption to errors
* like MDBX_BAD_VALSIZE (since the DB name is gone).
*
* Closing a database handle is not necessary, but lets mdbx_dbi_open()
* reuse the handle value. Usually it's better to set a bigger
* mdbx_env_set_maxdbs(), unless that value would be large.
*
* [in] env An environment handle returned by mdbx_env_create()
* [in] dbi A database handle returned by mdbx_dbi_open()
*/
LIBMDBX_API int mdbx_dbi_close(MDBX_env *env, MDBX_dbi dbi);
/* Empty or delete+close a database.
*
* See mdbx_dbi_close() for restrictions about closing the DB handle.
*
* [in] txn A transaction handle returned by mdbx_txn_begin()
* [in] dbi A database handle returned by mdbx_dbi_open()
* [in] del 0 to empty the DB, 1 to delete it from the environment
* and close the DB handle.
*
* Returns A non-zero error value on failure and 0 on success. */
LIBMDBX_API int mdbx_drop(MDBX_txn *txn, MDBX_dbi dbi, int del);
/* 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 key are returned
* in the structure to which data refers.
* If the database supports duplicate keys (MDBX_DUPSORT) then the
* first data item for the key will be returned. Retrieval of other
* items requires the use of mdbx_cursor_get().
*
* NOTE: The memory pointed to by the returned values is owned by the
* database. The caller need not dispose of the memory, and may not
* modify it in any way. For values returned in a read-only transaction
* any modification attempts will cause a SIGSEGV.
*
* NOTE: Values returned from the database are valid only until a
* subsequent update operation, or the end of the transaction.
*
* [in] txn A transaction handle returned by mdbx_txn_begin()
* [in] dbi A database handle returned by mdbx_dbi_open()
* [in] key The key to search for in the database
* [in,out] data The data corresponding to the key
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_NOTFOUND - the key was not in the database.
* - MDBX_EINVAL - an invalid parameter was specified. */
LIBMDBX_API int mdbx_get(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key,
MDBX_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 (MDBX_DUPSORT).
*
* [in] txn A transaction handle returned by mdbx_txn_begin()
* [in] dbi A database handle returned by mdbx_dbi_open()
* [in] key The key to store in the database
* [in,out] data The data to store
* [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.
*
* - MDBX_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 MDBX_DUPSORT. The function will return MDBX_KEYEXIST
* if the key/data pair already appears in the database.
*
* - MDBX_NOOVERWRITE
* Enter the new key/data pair only if the key does not already appear
* in the database. The function will return MDBX_KEYEXIST if the key
* already appears in the database, even if the database supports
* duplicates (MDBX_DUPSORT). The data parameter will be set to point
* to the existing item.
*
* - MDBX_CURRENT
* Update an single existing entry, but not add new ones. The function
* will return MDBX_NOTFOUND if the given key not exist in the database.
* Or the MDBX_EMULTIVAL in case duplicates for the given key.
*
* - MDBX_RESERVE
* Reserve space for data of the given size, but don't copy the given
* data. Instead, return a pointer to the reserved space, which the
* caller can fill in later - before the next update operation or the
* transaction ends. This saves an extra memcpy if the data is being
* generated later. MDBX does nothing else with this memory, the caller
* is expected to modify all of the space requested. This flag must not
* be specified if the database was opened with MDBX_DUPSORT.
*
* - MDBX_APPEND
* Append the given key/data pair to the end of the database. This option
* allows fast bulk loading when keys are already known to be in the
* correct order. Loading unsorted keys with this flag will cause
* a MDBX_EKEYMISMATCH error.
*
* - MDBX_APPENDDUP
* As above, but for sorted dup data.
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_KEYEXIST
* - MDBX_MAP_FULL - the database is full, see mdbx_env_set_mapsize().
* - MDBX_TXN_FULL - the transaction has too many dirty pages.
* - MDBX_EACCES - an attempt was made to write in a read-only transaction.
* - MDBX_EINVAL - an invalid parameter was specified. */
LIBMDBX_API int mdbx_put(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key,
MDBX_val *data, unsigned flags);
/* Delete items from a database.
*
* This function removes key/data pairs from the database.
*
* The data parameter is NOT ignored regardless the database does
* support sorted duplicate data items or not. If the data parameter
* is non-NULL only the matching data item will be deleted.
*
* This function will return MDBX_NOTFOUND if the specified key/data
* pair is not in the database.
*
* [in] txn A transaction handle returned by mdbx_txn_begin()
* [in] dbi A database handle returned by mdbx_dbi_open()
* [in] key The key to delete from the database
* [in] data The data to delete
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_EACCES - an attempt was made to write in a read-only transaction.
* - MDBX_EINVAL - an invalid parameter was specified. */
LIBMDBX_API int mdbx_del(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key,
MDBX_val *data);
/* Create a cursor handle.
*
* A cursor is associated with a specific transaction and database.
* A cursor cannot be used when its database handle is closed. Nor
* when its transaction has ended, except with mdbx_cursor_renew().
* It can be discarded with mdbx_cursor_close().
*
* A cursor must be closed explicitly always, before
* or after its transaction ends. It can be reused with
* mdbx_cursor_renew() before finally closing it.
*
* [in] txn A transaction handle returned by mdbx_txn_begin()
* [in] dbi A database handle returned by mdbx_dbi_open()
* [out] cursor Address where the new MDBX_cursor handle will be stored
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_EINVAL - an invalid parameter was specified. */
LIBMDBX_API int mdbx_cursor_open(MDBX_txn *txn, MDBX_dbi dbi,
MDBX_cursor **cursor);
/* Close a cursor handle.
*
* The cursor handle will be freed and must not be used again after this call.
* Its transaction must still be live if it is a write-transaction.
*
* [in] cursor A cursor handle returned by mdbx_cursor_open() */
LIBMDBX_API void mdbx_cursor_close(MDBX_cursor *cursor);
/* Renew a cursor handle.
*
* A cursor is associated with a specific transaction and database.
* Cursors that are only used in read-only transactions may be re-used,
* to avoid unnecessary malloc/free overhead. The cursor may be associated
* with a new read-only transaction, and referencing the same database handle
* as it was created with.
*
* This may be done whether the previous transaction is live or dead.
* [in] txn A transaction handle returned by mdbx_txn_begin()
* [in] cursor A cursor handle returned by mdbx_cursor_open()
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_EINVAL - an invalid parameter was specified. */
LIBMDBX_API int mdbx_cursor_renew(MDBX_txn *txn, MDBX_cursor *cursor);
/* Return the cursor's transaction handle.
*
* [in] cursor A cursor handle returned by mdbx_cursor_open() */
LIBMDBX_API MDBX_txn *mdbx_cursor_txn(MDBX_cursor *cursor);
/* Return the cursor's database handle.
*
* [in] cursor A cursor handle returned by mdbx_cursor_open() */
LIBMDBX_API MDBX_dbi mdbx_cursor_dbi(MDBX_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 key refers (except
* for the case of the MDBX_SET option, in which the key object is unchanged),
* and the address and length of the data are returned in the object to which
* data refers. See mdbx_get() for restrictions on using the output values.
*
* [in] cursor A cursor handle returned by mdbx_cursor_open()
* [in,out] key The key for a retrieved item
* [in,out] data The data of a retrieved item
* [in] op A cursor operation MDBX_cursor_op
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_NOTFOUND - no matching key found.
* - MDBX_EINVAL - an invalid parameter was specified. */
LIBMDBX_API int mdbx_cursor_get(MDBX_cursor *cursor, MDBX_val *key,
MDBX_val *data, MDBX_cursor_op op);
/* Store by cursor.
*
* This function stores key/data pairs into the database. The cursor is
* positioned at the new item, or on failure usually near it.
*
* [in] cursor A cursor handle returned by mdbx_cursor_open()
* [in] key The key operated on.
* [in] data The data operated on.
* [in] flags Options for this operation. This parameter
* must be set to 0 or one of the values described here:
*
* - MDBX_CURRENT
* Replace the item at the current cursor position. The key parameter
* must still be provided, and must match it, otherwise the function
* return MDBX_EKEYMISMATCH.
*
* NOTE: MDBX unlike LMDB allows you to change the size of the data and
* automatically handles reordering for sorted duplicates (MDBX_DUPSORT).
*
* - MDBX_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 MDBX_DUPSORT. The function will return MDBX_KEYEXIST if the
* key/data pair already appears in the database.
*
* - MDBX_NOOVERWRITE
* Enter the new key/data pair only if the key does not already appear
* in the database. The function will return MDBX_KEYEXIST if the key
* already appears in the database, even if the database supports
* duplicates (MDBX_DUPSORT).
*
* - MDBX_RESERVE
* Reserve space for data of the given size, but don't copy the given
* data. Instead, return a pointer to the reserved space, which the
* caller can fill in later - before the next update operation or the
* transaction ends. This saves an extra memcpy if the data is being
* generated later. This flag must not be specified if the database
* was opened with MDBX_DUPSORT.
*
* - MDBX_APPEND
* Append the given key/data pair to the end of the database. No key
* comparisons are performed. This option allows fast bulk loading when
* keys are already known to be in the correct order. Loading unsorted
* keys with this flag will cause a MDBX_KEYEXIST error.
*
* - MDBX_APPENDDUP
* As above, but for sorted dup data.
*
* - MDBX_MULTIPLE
* Store multiple contiguous data elements in a single request. This flag
* may only be specified if the database was opened with MDBX_DUPFIXED.
* The data argument must be an array of two MDBX_vals. The iov_len of the
* first MDBX_val must be the size of a single data element. The iov_base
* of the first MDBX_val must point to the beginning of the array of
* contiguous data elements. The iov_len of the second MDBX_val must be
* the count of the number of data elements to store. On return this
* field will be set to the count of the number of elements actually
* written. The iov_base of the second MDBX_val is unused.
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_EKEYMISMATCH
* - MDBX_MAP_FULL - the database is full, see mdbx_env_set_mapsize().
* - MDBX_TXN_FULL - the transaction has too many dirty pages.
* - MDBX_EACCES - an attempt was made to write in a read-only transaction.
* - MDBX_EINVAL - an invalid parameter was specified. */
LIBMDBX_API int mdbx_cursor_put(MDBX_cursor *cursor, MDBX_val *key,
MDBX_val *data, unsigned flags);
/* Delete current key/data pair
*
* This function deletes the key/data pair to which the cursor refers.
*
* [in] cursor A cursor handle returned by mdbx_cursor_open()
* [in] flags Options for this operation. This parameter must be set to 0
* or one of the values described here.
*
* - MDBX_NODUPDATA
* Delete all of the data items for the current key. This flag may only
* be specified if the database was opened with MDBX_DUPSORT.
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_EACCES - an attempt was made to write in a read-only transaction.
* - MDBX_EINVAL - an invalid parameter was specified. */
LIBMDBX_API int mdbx_cursor_del(MDBX_cursor *cursor, unsigned flags);
/* Return count of duplicates for current key.
*
* This call is only valid on databases that support sorted duplicate data
* items MDBX_DUPSORT.
*
* [in] cursor A cursor handle returned by mdbx_cursor_open()
* [out] countp Address where the count will be stored
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_EINVAL - cursor is not initialized, or an invalid parameter
* was specified. */
LIBMDBX_API int mdbx_cursor_count(MDBX_cursor *cursor, size_t *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.
*
* [in] txn A transaction handle returned by mdbx_txn_begin()
* [in] dbi A database handle returned by mdbx_dbi_open()
* [in] a The first item to compare
* [in] b The second item to compare
*
* Returns < 0 if a < b, 0 if a == b, > 0 if a > b */
LIBMDBX_API int mdbx_cmp(MDBX_txn *txn, MDBX_dbi dbi, const MDBX_val *a,
const MDBX_val *b);
/* Compare two data items according to a particular database.
*
* This returns a comparison as if the two items were data items of
* the specified database. The database must have the MDBX_DUPSORT flag.
*
* [in] txn A transaction handle returned by mdbx_txn_begin()
* [in] dbi A database handle returned by mdbx_dbi_open()
* [in] a The first item to compare
* [in] b The second item to compare
*
* Returns < 0 if a < b, 0 if a == b, > 0 if a > b */
LIBMDBX_API int mdbx_dcmp(MDBX_txn *txn, MDBX_dbi dbi, const MDBX_val *a,
const MDBX_val *b);
/* A callback function used to print a message from the library.
*
* [in] msg The string to be printed.
* [in] ctx An arbitrary context pointer for the callback.
*
* Returns < 0 on failure, >= 0 on success. */
typedef int(MDBX_msg_func)(const char *msg, void *ctx);
/* Dump the entries in the reader lock table.
*
* [in] env An environment handle returned by mdbx_env_create()
* [in] func A MDBX_msg_func function
* [in] ctx Anything the message function needs
*
* Returns < 0 on failure, >= 0 on success. */
LIBMDBX_API int mdbx_reader_list(MDBX_env *env, MDBX_msg_func *func, void *ctx);
/* Check for stale entries in the reader lock table.
*
* [in] env An environment handle returned by mdbx_env_create()
* [out] dead Number of stale slots that were cleared
*
* Returns 0 on success, non-zero on failure. */
LIBMDBX_API int mdbx_reader_check(MDBX_env *env, int *dead);
LIBMDBX_API char *mdbx_dkey(const MDBX_val *key, char *const buf,
const size_t bufsize);
LIBMDBX_API int mdbx_env_close_ex(MDBX_env *env, int dont_sync);
/* Set threshold to force flush the data buffers to disk,
* even of MDBX_NOSYNC, MDBX_NOMETASYNC and MDBX_MAPASYNC flags
* in the environment.
*
* Data is always written to disk when mdbx_txn_commit() is called,
* but the operating system may keep it buffered. MDBX always flushes
* the OS buffers upon commit as well, unless the environment was
* opened with MDBX_NOSYNC or in part MDBX_NOMETASYNC.
*
* The default is 0, than mean no any threshold checked, and no additional
* flush will be made.
*
* [in] env An environment handle returned by mdbx_env_create()
* [in] bytes The size in bytes of summary changes when a synchronous
* flush would be made.
*
* Returns A non-zero error value on failure and 0 on success. */
LIBMDBX_API int mdbx_env_set_syncbytes(MDBX_env *env, size_t bytes);
/* Returns a lag of the reading for the given transaction.
*
* Returns an information for estimate how much given read-only
* transaction is lagging relative the to actual head.
*
* [in] txn A transaction handle returned by mdbx_txn_begin()
* [out] percent Percentage of page allocation in the database.
*
* Returns Number of transactions committed after the given was started for
* read, or -1 on failure. */
LIBMDBX_API int mdbx_txn_straggler(MDBX_txn *txn, int *percent);
/* A callback function for killing a laggard readers,
* but also could waiting ones. Called in case of MDBX_MAP_FULL error.
*
* [in] env An environment handle returned by mdbx_env_create().
* [in] pid pid of the reader process.
* [in] tid thread_id of the reader thread.
* [in] txn Transaction number on which stalled.
* [in] gap A lag from the last commited txn.
* [in] retry A retry number, less that zero for notify end of OOM-loop.
*
* Returns -1 on failure (reader is not killed),
* 0 should wait or retry,
* 1 drop reader txn-lock (reading-txn was aborted),
* >1 drop reader registration (reader process was killed). */
typedef int(MDBX_oom_func)(MDBX_env *env, int pid, mdbx_tid_t tid, uint64_t txn,
unsigned gap, int retry);
/* Set the OOM callback.
*
* Callback will be called only on out-of-pages case for killing
* a laggard readers to allowing reclaiming of freeDB.
*
* [in] env An environment handle returned by mdbx_env_create().
* [in] oomfunc A MDBX_oom_func function or NULL to disable.
*
* Returns A non-zero error value on failure and 0 on success. */
LIBMDBX_API int mdbx_env_set_oomfunc(MDBX_env *env, MDBX_oom_func *oom_func);
/* Get the current oom_func callback.
*
* Callback will be called only on out-of-pages case for killing
* a laggard readers to allowing reclaiming of freeDB.
*
* [in] env An environment handle returned by mdbx_env_create().
*
* Returns A MDBX_oom_func function or NULL if disabled. */
LIBMDBX_API MDBX_oom_func *mdbx_env_get_oomfunc(MDBX_env *env);
#define MDBX_DBG_ASSERT 1
#define MDBX_DBG_PRINT 2
#define MDBX_DBG_TRACE 4
#define MDBX_DBG_EXTRA 8
#define MDBX_DBG_AUDIT 16
#define MDBX_DBG_JITTER 32
#define MDBX_DBG_DUMP 64
typedef void MDBX_debug_func(int type, const char *function, int line,
const char *msg, va_list args);
LIBMDBX_API int mdbx_setup_debug(int flags, MDBX_debug_func *logger);
typedef int MDBX_pgvisitor_func(uint64_t pgno, unsigned pgnumber, void *ctx,
const char *dbi, const char *type,
size_t nentries, size_t payload_bytes,
size_t header_bytes, size_t unused_bytes);
LIBMDBX_API int mdbx_env_pgwalk(MDBX_txn *txn, MDBX_pgvisitor_func *visitor,
void *ctx);
typedef struct mdbx_canary { uint64_t x, y, z, v; } mdbx_canary;
LIBMDBX_API int mdbx_canary_put(MDBX_txn *txn, const mdbx_canary *canary);
LIBMDBX_API int mdbx_canary_get(MDBX_txn *txn, mdbx_canary *canary);
/* Returns:
* - MDBX_RESULT_TRUE
* when no more data available or cursor not positioned;
* - MDBX_RESULT_FALSE
* when data available;
* - Otherwise the error code. */
LIBMDBX_API int mdbx_cursor_eof(MDBX_cursor *mc);
/* Returns: MDBX_RESULT_TRUE, MDBX_RESULT_FALSE or Error code. */
LIBMDBX_API int mdbx_cursor_on_first(MDBX_cursor *mc);
/* Returns: MDBX_RESULT_TRUE, MDBX_RESULT_FALSE or Error code. */
LIBMDBX_API int mdbx_cursor_on_last(MDBX_cursor *mc);
LIBMDBX_API int mdbx_replace(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key,
MDBX_val *new_data, MDBX_val *old_data,
unsigned flags);
/* Same as mdbx_get(), but:
* 1) if values_count is not NULL, then returns the count
* of multi-values/duplicates for a given key.
* 2) updates the key for pointing to the actual key's data inside DB. */
LIBMDBX_API int mdbx_get_ex(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key,
MDBX_val *data, size_t *values_count);
LIBMDBX_API int mdbx_is_dirty(const MDBX_txn *txn, const void *ptr);
LIBMDBX_API int mdbx_dbi_sequence(MDBX_txn *txn, MDBX_dbi dbi, uint64_t *result,
uint64_t increment);
/*----------------------------------------------------------------------------*/
/* attribute support functions for Nexenta */
typedef uint_fast64_t mdbx_attr_t;
/* Store by cursor with attribute.
*
* This function stores key/data pairs into the database. The cursor is
* positioned at the new item, or on failure usually near it.
*
* NOTE: Internally based on MDBX_RESERVE feature,
* therefore doesn't support MDBX_DUPSORT.
*
* [in] cursor A cursor handle returned by mdbx_cursor_open()
* [in] key The key operated on.
* [in] data The data operated on.
* [in] attr The attribute.
* [in] flags Options for this operation. This parameter must be set to 0
* or one of the values described here:
*
* - MDBX_CURRENT
* Replace the item at the current cursor position. The key parameter
* must still be provided, and must match it, otherwise the function
* return MDBX_EKEYMISMATCH.
*
* - MDBX_APPEND
* Append the given key/data pair to the end of the database. No key
* comparisons are performed. This option allows fast bulk loading when
* keys are already known to be in the correct order. Loading unsorted
* keys with this flag will cause a MDBX_KEYEXIST error.
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_EKEYMISMATCH
* - MDBX_MAP_FULL - the database is full, see mdbx_env_set_mapsize().
* - MDBX_TXN_FULL - the transaction has too many dirty pages.
* - MDBX_EACCES - an attempt was made to write in a read-only transaction.
* - MDBX_EINVAL - an invalid parameter was specified. */
LIBMDBX_API int mdbx_cursor_put_attr(MDBX_cursor *cursor, MDBX_val *key,
MDBX_val *data, mdbx_attr_t attr,
unsigned flags);
/* Store items and attributes 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.
*
* NOTE: Internally based on MDBX_RESERVE feature,
* therefore doesn't support MDBX_DUPSORT.
*
* [in] txn A transaction handle returned by mdbx_txn_begin().
* [in] dbi A database handle returned by mdbx_dbi_open().
* [in] key The key to store in the database.
* [in] attr The attribute to store in the database.
* [in,out] data The data to store.
* [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:
*
* - MDBX_NOOVERWRITE
* Enter the new key/data pair only if the key does not already appear
* in the database. The function will return MDBX_KEYEXIST if the key
* already appears in the database. The data parameter will be set to
* point to the existing item.
*
* - MDBX_CURRENT
* Update an single existing entry, but not add new ones. The function
* will return MDBX_NOTFOUND if the given key not exist in the database.
* Or the MDBX_EMULTIVAL in case duplicates for the given key.
*
* - MDBX_APPEND
* Append the given key/data pair to the end of the database. This option
* allows fast bulk loading when keys are already known to be in the
* correct order. Loading unsorted keys with this flag will cause
* a MDBX_EKEYMISMATCH error.
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_KEYEXIST
* - MDBX_MAP_FULL - the database is full, see mdbx_env_set_mapsize().
* - MDBX_TXN_FULL - the transaction has too many dirty pages.
* - MDBX_EACCES - an attempt was made to write in a read-only transaction.
* - MDBX_EINVAL - an invalid parameter was specified. */
LIBMDBX_API int mdbx_put_attr(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key,
MDBX_val *data, mdbx_attr_t attr, unsigned flags);
/* Set items attribute from a database.
*
* This function stores key/data pairs attribute to the database.
*
* NOTE: Internally based on MDBX_RESERVE feature,
* therefore doesn't support MDBX_DUPSORT.
*
* [in] txn A transaction handle returned by mdbx_txn_begin().
* [in] dbi A database handle returned by mdbx_dbi_open().
* [in] key The key to search for in the database.
* [in] data The data to be stored or NULL to save previous value.
* [in] attr The attribute to be stored.
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_NOTFOUND - the key-value pair was not in the database.
* - MDBX_EINVAL - an invalid parameter was specified. */
LIBMDBX_API int mdbx_set_attr(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key,
MDBX_val *data, mdbx_attr_t attr);
/* Get items attribute from a database cursor.
*
* This function retrieves key/data pairs from the database. The address and
* length of the key are returned in the object to which key refers (except
* for the case of the MDBX_SET option, in which the key object is unchanged),
* and the address and length of the data are returned in the object to which
* data refers. See mdbx_get() for restrictions on using the output values.
*
* [in] cursor A cursor handle returned by mdbx_cursor_open()
* [in,out] key The key for a retrieved item
* [in,out] data The data of a retrieved item
* [in] op A cursor operation MDBX_cursor_op
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_NOTFOUND - no matching key found.
* - MDBX_EINVAL - an invalid parameter was specified. */
LIBMDBX_API int mdbx_cursor_get_attr(MDBX_cursor *mc, MDBX_val *key,
MDBX_val *data, mdbx_attr_t *attrptr,
MDBX_cursor_op op);
/* Get items attribute from a database.
*
* This function retrieves key/data pairs from the database. The address
* and length of the data associated with the specified key are returned
* in the structure to which data refers.
* If the database supports duplicate keys (MDBX_DUPSORT) then the
* first data item for the key will be returned. Retrieval of other
* items requires the use of mdbx_cursor_get().
*
* NOTE: The memory pointed to by the returned values is owned by the
* database. The caller need not dispose of the memory, and may not
* modify it in any way. For values returned in a read-only transaction
* any modification attempts will cause a SIGSEGV.
*
* NOTE: Values returned from the database are valid only until a
* subsequent update operation, or the end of the transaction.
*
* [in] txn A transaction handle returned by mdbx_txn_begin()
* [in] dbi A database handle returned by mdbx_dbi_open()
* [in] key The key to search for in the database
* [in,out] data The data corresponding to the key
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
* - MDBX_NOTFOUND - the key was not in the database.
* - MDBX_EINVAL - an invalid parameter was specified. */
LIBMDBX_API int mdbx_get_attr(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key,
MDBX_val *data, mdbx_attr_t *attrptr);
#ifdef __cplusplus
}
#endif
#endif /* LIBMDBX_H */