mdb.c 264 KB
Newer Older
1
/** @file mdb.c
Howard Chu's avatar
Howard Chu committed
2
 *	@brief Lightning memory-mapped database library
3
4
5
6
 *
 *	A Btree-based database management library modeled loosely on the
 *	BerkeleyDB API, but much simplified.
 */
Howard Chu's avatar
Howard Chu committed
7
/*
Quanah Gibson-Mount's avatar
Quanah Gibson-Mount committed
8
 * Copyright 2011-2015 Howard Chu, Symas Corp.
Howard Chu's avatar
Howard Chu committed
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
 * 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 btree.c written by Martin Hedenfalk.
 *
 * 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.
 */
35
#ifndef _GNU_SOURCE
Hallvard Furuseth's avatar
Hallvard Furuseth committed
36
#define _GNU_SOURCE 1
37
#endif
Howard Chu's avatar
Howard Chu committed
38
#ifdef _WIN32
Howard Chu's avatar
Howard Chu committed
39
#include <malloc.h>
Howard Chu's avatar
Howard Chu committed
40
#include <windows.h>
Howard Chu's avatar
Howard Chu committed
41
42
43
44
45
/** getpid() returns int; MinGW defines pid_t but MinGW64 typedefs it
 *  as int64 which is wrong. MSVC doesn't define it at all, so just
 *  don't use it.
 */
#define MDB_PID_T	int
Howard Chu's avatar
Howard Chu committed
46
47
48
#define MDB_THR_T	DWORD
#include <sys/types.h>
#include <sys/stat.h>
Howard Chu's avatar
Howard Chu committed
49
50
#ifdef __GNUC__
# include <sys/param.h>
Howard Chu's avatar
Howard Chu committed
51
#else
Howard Chu's avatar
Howard Chu committed
52
53
54
55
56
57
58
59
# define LITTLE_ENDIAN	1234
# define BIG_ENDIAN	4321
# define BYTE_ORDER	LITTLE_ENDIAN
# ifndef SSIZE_MAX
#  define SSIZE_MAX	INT_MAX
# endif
#endif
#else
Howard Chu's avatar
Howard Chu committed
60
61
#include <sys/types.h>
#include <sys/stat.h>
Howard Chu's avatar
Howard Chu committed
62
#define MDB_PID_T	pid_t
Howard Chu's avatar
Howard Chu committed
63
#define MDB_THR_T	pthread_t
Howard Chu's avatar
Howard Chu committed
64
#include <sys/param.h>
Howard Chu's avatar
Howard Chu committed
65
66
67
68
69
#include <sys/uio.h>
#include <sys/mman.h>
#ifdef HAVE_SYS_FILE_H
#include <sys/file.h>
#endif
Howard Chu's avatar
Howard Chu committed
70
#include <fcntl.h>
Howard Chu's avatar
Howard Chu committed
71
#endif
Howard Chu's avatar
Howard Chu committed
72

Howard Chu's avatar
Howard Chu committed
73
74
75
76
77
78
79
80
81
#if defined(__mips) && defined(__linux)
/* MIPS has cache coherency issues, requires explicit cache control */
#include <asm/cachectl.h>
extern int cacheflush(char *addr, int nbytes, int cache);
#define CACHEFLUSH(addr, bytes, cache)	cacheflush(addr, bytes, cache)
#else
#define CACHEFLUSH(addr, bytes, cache)
#endif

82
83
#if defined(__linux) && !defined(MDB_FDATASYNC_WORKS)
/** fdatasync is broken on ext3/ext4fs on older kernels, see
Howard Chu's avatar
Howard Chu committed
84
85
86
 *	description in #mdb_env_open2 comments. You can safely
 *	define MDB_FDATASYNC_WORKS if this code will only be run
 *	on kernels 3.6 and newer.
87
88
89
 */
#define	BROKEN_FDATASYNC
#endif
90

Howard Chu's avatar
Howard Chu committed
91
#include <errno.h>
92
#include <limits.h>
Howard Chu's avatar
Howard Chu committed
93
#include <stddef.h>
94
#include <inttypes.h>
Howard Chu's avatar
Howard Chu committed
95
96
97
98
99
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
100

Howard Chu's avatar
Howard Chu committed
101
#if defined(__sun) || defined(ANDROID)
102
103
104
105
106
/* Most platforms have posix_memalign, older may only have memalign */
#define HAVE_MEMALIGN	1
#include <malloc.h>
#endif

107
#if !(defined(BYTE_ORDER) || defined(__BYTE_ORDER))
108
#include <netinet/in.h>
109
110
111
#include <resolv.h>	/* defines BYTE_ORDER on HPUX and Solaris */
#endif

112
#if defined(__APPLE__) || defined (BSD)
113
# define MDB_USE_SYSV_SEM	1
114
115
116
# define MDB_FDATASYNC		fsync
#elif defined(ANDROID)
# define MDB_FDATASYNC		fsync
117
118
#endif

119
120
#ifndef _WIN32
#include <pthread.h>
121
122
123
124
125
126
127
128
129
130
#ifdef MDB_USE_SYSV_SEM
#include <sys/ipc.h>
#include <sys/sem.h>
#ifdef _SEM_SEMUN_UNDEFINED
union semun {
	int val;
	struct semid_ds *buf;
	unsigned short *array;
};
#endif /* _SEM_SEMUN_UNDEFINED */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
131
132
#else
#define MDB_USE_POSIX_MUTEX	1
133
134
#endif /* MDB_USE_SYSV_SEM */
#endif /* !_WIN32 */
Howard Chu's avatar
Howard Chu committed
135

Hallvard Furuseth's avatar
Hallvard Furuseth committed
136
137
138
139
140
#if defined(_WIN32) + defined(MDB_USE_SYSV_SEM) \
	+ defined(MDB_USE_POSIX_MUTEX) != 1
# error "Ambiguous shared-lock implementation"
#endif

141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
#ifdef USE_VALGRIND
#include <valgrind/memcheck.h>
#define VGMEMP_CREATE(h,r,z)    VALGRIND_CREATE_MEMPOOL(h,r,z)
#define VGMEMP_ALLOC(h,a,s) VALGRIND_MEMPOOL_ALLOC(h,a,s)
#define VGMEMP_FREE(h,a) VALGRIND_MEMPOOL_FREE(h,a)
#define VGMEMP_DESTROY(h)	VALGRIND_DESTROY_MEMPOOL(h)
#define VGMEMP_DEFINED(a,s)	VALGRIND_MAKE_MEM_DEFINED(a,s)
#else
#define VGMEMP_CREATE(h,r,z)
#define VGMEMP_ALLOC(h,a,s)
#define VGMEMP_FREE(h,a)
#define VGMEMP_DESTROY(h)
#define VGMEMP_DEFINED(a,s)
#endif

Howard Chu's avatar
Howard Chu committed
156
#ifndef BYTE_ORDER
Howard Chu's avatar
Howard Chu committed
157
158
159
160
161
162
163
164
165
166
167
168
# if (defined(_LITTLE_ENDIAN) || defined(_BIG_ENDIAN)) && !(defined(_LITTLE_ENDIAN) && defined(_BIG_ENDIAN))
/* Solaris just defines one or the other */
#  define LITTLE_ENDIAN	1234
#  define BIG_ENDIAN	4321
#  ifdef _LITTLE_ENDIAN
#   define BYTE_ORDER  LITTLE_ENDIAN
#  else
#   define BYTE_ORDER  BIG_ENDIAN
#  endif
# else
#  define BYTE_ORDER   __BYTE_ORDER
# endif
Howard Chu's avatar
Howard Chu committed
169
#endif
Howard Chu's avatar
Howard Chu committed
170

Howard Chu's avatar
Howard Chu committed
171
172
173
174
175
#ifndef LITTLE_ENDIAN
#define LITTLE_ENDIAN	__LITTLE_ENDIAN
#endif
#ifndef BIG_ENDIAN
#define BIG_ENDIAN	__BIG_ENDIAN
176
177
#endif

Howard Chu's avatar
Howard Chu committed
178
#if defined(__i386) || defined(__x86_64) || defined(_M_IX86)
Howard Chu's avatar
Howard Chu committed
179
180
181
#define MISALIGNED_OK	1
#endif

Howard Chu's avatar
Howard Chu committed
182
#include "lmdb.h"
183
184
#include "midl.h"

Howard Chu's avatar
Howard Chu committed
185
186
#if (BYTE_ORDER == LITTLE_ENDIAN) == (BYTE_ORDER == BIG_ENDIAN)
# error "Unknown or unsupported endianness (BYTE_ORDER)"
187
188
189
190
#elif (-6 & 5) || CHAR_BIT != 8 || UINT_MAX < 0xffffffff || ULONG_MAX % 0xFFFF
# error "Two's complement, reasonably sized integer types, please"
#endif

191
192
#ifdef __GNUC__
/** Put infrequently used env functions in separate section */
Howard Chu's avatar
Howard Chu committed
193
194
195
196
197
# ifdef __APPLE__
#  define	ESECT	__attribute__ ((section("__TEXT,text_env")))
# else
#  define	ESECT	__attribute__ ((section("text_env")))
# endif
198
199
200
201
#else
#define ESECT
#endif

Howard Chu's avatar
Howard Chu committed
202
/** @defgroup internal	LMDB Internals
203
204
 *	@{
 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
205
/** @defgroup compat	Compatibility Macros
Howard Chu's avatar
Howard Chu committed
206
207
208
209
 *	A bunch of macros to minimize the amount of platform-specific ifdefs
 *	needed throughout the rest of the code. When the features this library
 *	needs are similar enough to POSIX to be hidden in a one-or-two line
 *	replacement, this macro approach is used.
210
211
 *	@{
 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
212

Hallvard Furuseth's avatar
Hallvard Furuseth committed
213
	/** Features under development */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
214
215
216
217
#ifndef MDB_DEVEL
#define MDB_DEVEL 0
#endif

Hallvard Furuseth's avatar
Hallvard Furuseth committed
218
219
220
221
222
223
224
225
226
227
	/** Wrapper around __func__, which is a C99 feature */
#if __STDC_VERSION__ >= 199901L
# define mdb_func_	__func__
#elif __GNUC__ >= 2 || _MSC_VER >= 1300
# define mdb_func_	__FUNCTION__
#else
/* If a debug message says <mdb_unknown>(), update the #if statements above */
# define mdb_func_	"<mdb_unknown>"
#endif

228
229
230
231
232
233
/* Internal error codes, not exposed outside liblmdb */
#define	MDB_NO_ROOT		(MDB_LAST_ERRCODE + 10)
#ifdef _WIN32
#define MDB_OWNERDEAD	((int) WAIT_ABANDONED)
#elif defined MDB_USE_SYSV_SEM
#define MDB_OWNERDEAD	(MDB_LAST_ERRCODE + 11)
Hallvard Furuseth's avatar
Hallvard Furuseth committed
234
235
236
237
238
239
#elif defined(MDB_USE_POSIX_MUTEX) && defined(EOWNERDEAD)
#define MDB_OWNERDEAD	EOWNERDEAD	/**< #LOCK_MUTEX0() result if dead owner */
#endif

#ifdef MDB_OWNERDEAD
#define MDB_ROBUST_SUPPORTED	1
240
241
#endif

Howard Chu's avatar
Howard Chu committed
242
#ifdef _WIN32
Howard Chu's avatar
Howard Chu committed
243
#define MDB_USE_HASH	1
244
#define MDB_PIDLOCK	0
Howard Chu's avatar
Howard Chu committed
245
246
#define THREAD_RET	DWORD
#define pthread_t	HANDLE
Howard Chu's avatar
Howard Chu committed
247
#define pthread_mutex_t	HANDLE
Howard Chu's avatar
Howard Chu committed
248
#define pthread_cond_t	HANDLE
249
typedef HANDLE mdb_mutex_t, mdb_mutexref_t;
Howard Chu's avatar
Howard Chu committed
250
251
#define pthread_key_t	DWORD
#define pthread_self()	GetCurrentThreadId()
252
253
#define pthread_key_create(x,y)	\
	((*(x) = TlsAlloc()) == TLS_OUT_OF_INDEXES ? ErrCode() : 0)
Howard Chu's avatar
Howard Chu committed
254
255
#define pthread_key_delete(x)	TlsFree(x)
#define pthread_getspecific(x)	TlsGetValue(x)
256
#define pthread_setspecific(x,y)	(TlsSetValue(x,y) ? 0 : ErrCode())
Howard Chu's avatar
Howard Chu committed
257
258
#define pthread_mutex_unlock(x)	ReleaseMutex(*x)
#define pthread_mutex_lock(x)	WaitForSingleObject(*x, INFINITE)
Howard Chu's avatar
Howard Chu committed
259
#define pthread_cond_signal(x)	SetEvent(*x)
Howard Chu's avatar
Howard Chu committed
260
#define pthread_cond_wait(cond,mutex)	do{SignalObjectAndWait(*mutex, *cond, INFINITE, FALSE); WaitForSingleObject(*mutex, INFINITE);}while(0)
Howard Chu's avatar
Howard Chu committed
261
262
#define THREAD_CREATE(thr,start,arg)	thr=CreateThread(NULL,0,start,arg,0,NULL)
#define THREAD_FINISH(thr)	WaitForSingleObject(thr, INFINITE)
Hallvard Furuseth's avatar
Hallvard Furuseth committed
263
264
#define LOCK_MUTEX0(mutex)		WaitForSingleObject(mutex, INFINITE)
#define UNLOCK_MUTEX(mutex)		ReleaseMutex(mutex)
265
#define mdb_mutex_consistent(mutex)	0
Howard Chu's avatar
Howard Chu committed
266
#define getpid()	GetCurrentProcessId()
267
#define	MDB_FDATASYNC(fd)	(!FlushFileBuffers(fd))
268
#define	MDB_MSYNC(addr,len,flags)	(!FlushViewOfFile(addr,len))
Howard Chu's avatar
Howard Chu committed
269
#define	ErrCode()	GetLastError()
Hallvard Furuseth's avatar
Hallvard Furuseth committed
270
#define GET_PAGESIZE(x) {SYSTEM_INFO si; GetSystemInfo(&si); (x) = si.dwPageSize;}
271
#define	close(fd)	(CloseHandle(fd) ? 0 : -1)
Howard Chu's avatar
Howard Chu committed
272
#define	munmap(ptr,len)	UnmapViewOfFile(ptr)
Hallvard Furuseth's avatar
Hallvard Furuseth committed
273
#ifdef PROCESS_QUERY_LIMITED_INFORMATION
Hallvard Furuseth's avatar
Hallvard Furuseth committed
274
275
276
277
#define MDB_PROCESS_QUERY_LIMITED_INFORMATION PROCESS_QUERY_LIMITED_INFORMATION
#else
#define MDB_PROCESS_QUERY_LIMITED_INFORMATION 0x1000
#endif
278
#define	Z	"I"
Howard Chu's avatar
Howard Chu committed
279
#else
Howard Chu's avatar
Howard Chu committed
280
281
282
#define THREAD_RET	void *
#define THREAD_CREATE(thr,start,arg)	pthread_create(&thr,NULL,start,arg)
#define THREAD_FINISH(thr)	pthread_join(thr,NULL)
283
#define	Z	"z"			/**< printf format modifier for size_t */
284

285
286
287
	/** For MDB_LOCK_FORMAT: True if readers take a pid lock in the lockfile */
#define MDB_PIDLOCK			1

288
#ifdef MDB_USE_SYSV_SEM
289

290
291
292
typedef struct mdb_mutex {
	int semid;
	int semnum;
293
	int *locked;
294
} mdb_mutex_t[1], *mdb_mutexref_t;
295

Hallvard Furuseth's avatar
Hallvard Furuseth committed
296
#define LOCK_MUTEX0(mutex)		mdb_sem_wait(mutex)
297
298
299
#define UNLOCK_MUTEX(mutex)		do { \
	struct sembuf sb = { 0, 1, SEM_UNDO }; \
	sb.sem_num = (mutex)->semnum; \
300
	*(mutex)->locked = 0; \
301
302
	semop((mutex)->semid, &sb, 1); \
} while(0)
303
304

static int
305
mdb_sem_wait(mdb_mutexref_t sem)
306
{
307
308
309
310
311
312
313
314
315
316
317
	int rc, *locked = sem->locked;
	struct sembuf sb = { 0, -1, SEM_UNDO };
	sb.sem_num = sem->semnum;
	do {
		if (!semop(sem->semid, &sb, 1)) {
			rc = *locked ? MDB_OWNERDEAD : MDB_SUCCESS;
			*locked = 1;
			break;
		}
	} while ((rc = errno) == EINTR);
	return rc;
318
319
}

320
321
#define mdb_mutex_consistent(mutex)	0

Hallvard Furuseth's avatar
Hallvard Furuseth committed
322
#else	/* MDB_USE_POSIX_MUTEX: */
323
324
325
326
327
328
	/** Shared mutex/semaphore as it is stored (mdb_mutex_t), and as
	 *	local variables keep it (mdb_mutexref_t).
	 *
	 *	An mdb_mutex_t can be assigned to an mdb_mutexref_t.  They can
	 *	be the same, or an array[size 1] and a pointer.
	 *	@{
Howard Chu's avatar
Howard Chu committed
329
	 */
330
331
typedef pthread_mutex_t mdb_mutex_t[1], *mdb_mutexref_t;
	/*	@} */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
332
333
	/** Lock the reader or writer mutex.
	 *	Returns 0 or a code to give #mdb_mutex_failed(), as in #LOCK_MUTEX().
Howard Chu's avatar
Howard Chu committed
334
	 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
335
336
#define LOCK_MUTEX0(mutex)	pthread_mutex_lock(mutex)
	/** Unlock the reader or writer mutex.
Howard Chu's avatar
Howard Chu committed
337
	 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
338
#define UNLOCK_MUTEX(mutex)	pthread_mutex_unlock(mutex)
339
340
341
	/** Mark mutex-protected data as repaired, after death of previous owner.
	 */
#define mdb_mutex_consistent(mutex)	pthread_mutex_consistent(mutex)
342
#endif	/* MDB_USE_SYSV_SEM */
Howard Chu's avatar
Howard Chu committed
343
344
345

	/** Get the error code for the last failed system function.
	 */
Howard Chu's avatar
Howard Chu committed
346
#define	ErrCode()	errno
Howard Chu's avatar
Howard Chu committed
347

348
349
350
351
352
353
	/** An abstraction for a file handle.
	 *	On POSIX systems file handles are small integers. On Windows
	 *	they're opaque pointers.
	 */
#define	HANDLE	int

Howard Chu's avatar
Howard Chu committed
354
355
356
357
	/**	A value for an invalid file handle.
	 *	Mainly used to initialize file variables and signify that they are
	 *	unused.
	 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
358
#define INVALID_HANDLE_VALUE	(-1)
Howard Chu's avatar
Howard Chu committed
359
360
361
362
363

	/** Get the size of a memory page for the system.
	 *	This is the basic size that the platform's memory manager uses, and is
	 *	fundamental to the use of memory-mapped files.
	 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
364
#define	GET_PAGESIZE(x)	((x) = sysconf(_SC_PAGE_SIZE))
Howard Chu's avatar
Howard Chu committed
365
#endif
Howard Chu's avatar
Howard Chu committed
366

367
#if defined(_WIN32)
Howard Chu's avatar
Howard Chu committed
368
#define MNAME_LEN	32
369
#elif defined(MDB_USE_SYSV_SEM)
370
#define MNAME_LEN	(sizeof(int))
371
372
#else
#define MNAME_LEN	(sizeof(pthread_mutex_t))
Howard Chu's avatar
Howard Chu committed
373
374
#endif

375
376
377
378
379
380
#ifdef MDB_USE_SYSV_SEM
#define SYSV_SEM_FLAG	1		/**< SysV sems in lockfile format */
#else
#define SYSV_SEM_FLAG	0
#endif

381
/** @} */
Howard Chu's avatar
Howard Chu committed
382

Hallvard Furuseth's avatar
Hallvard Furuseth committed
383
384
385
386
387
388
389
#ifdef MDB_ROBUST_SUPPORTED
	/** Lock mutex, handle any error, set rc = result.
	 *	Return 0 on success, nonzero (not rc) on error.
	 */
#define LOCK_MUTEX(rc, env, mutex) \
	(((rc) = LOCK_MUTEX0(mutex)) && \
	 ((rc) = mdb_mutex_failed(env, mutex, rc)))
390
static int mdb_mutex_failed(MDB_env *env, mdb_mutexref_t mutex, int rc);
Hallvard Furuseth's avatar
Hallvard Furuseth committed
391
392
393
394
395
#else
#define LOCK_MUTEX(rc, env, mutex) ((rc) = LOCK_MUTEX0(mutex))
#define mdb_mutex_failed(env, mutex, rc) (rc)
#endif

396
#ifndef _WIN32
Howard Chu's avatar
Howard Chu committed
397
398
399
400
401
402
/**	A flag for opening a file and requesting synchronous data writes.
 *	This is only used when writing a meta page. It's not strictly needed;
 *	we could just do a normal write and then immediately perform a flush.
 *	But if this flag is available it saves us an extra system call.
 *
 *	@note If O_DSYNC is undefined but exists in /usr/include,
Hallvard Furuseth's avatar
Hallvard Furuseth committed
403
404
405
406
407
408
 * preferably set some compiler flag to get the definition.
 * Otherwise compile with the less efficient -DMDB_DSYNC=O_SYNC.
 */
#ifndef MDB_DSYNC
# define MDB_DSYNC	O_DSYNC
#endif
409
410
411
412
413
414
415
#endif

/** Function for flushing the data of a file. Define this to fsync
 *	if fdatasync() is not supported.
 */
#ifndef MDB_FDATASYNC
# define MDB_FDATASYNC	fdatasync
416
417
418
419
420
421
422
423
424
425
426
427
#endif

#ifndef MDB_MSYNC
# define MDB_MSYNC(addr,len,flags)	msync(addr,len,flags)
#endif

#ifndef MS_SYNC
#define	MS_SYNC	1
#endif

#ifndef MS_ASYNC
#define	MS_ASYNC	0
428
429
#endif

Howard Chu's avatar
Howard Chu committed
430
431
432
433
434
435
436
437
	/** A page number in the database.
	 *	Note that 64 bit page numbers are overkill, since pages themselves
	 *	already represent 12-13 bits of addressable memory, and the OS will
	 *	always limit applications to a maximum of 63 bits of address space.
	 *
	 *	@note In the #MDB_node structure, we only store 48 bits of this value,
	 *	which thus limits us to only 60 bits of addressable data.
	 */
438
typedef MDB_ID	pgno_t;
Hallvard Furuseth's avatar
Hallvard Furuseth committed
439

440
441
442
	/** A transaction ID.
	 *	See struct MDB_txn.mt_txnid for details.
	 */
443
typedef MDB_ID	txnid_t;
Hallvard Furuseth's avatar
Hallvard Furuseth committed
444

Howard Chu's avatar
Howard Chu committed
445
446
447
/** @defgroup debug	Debug Macros
 *	@{
 */
Howard Chu's avatar
Howard Chu committed
448
#ifndef MDB_DEBUG
449
	/**	Enable debug output.  Needs variable argument macros (a C99 feature).
Howard Chu's avatar
Howard Chu committed
450
451
452
	 *	Set this to 1 for copious tracing. Set to 2 to add dumps of all IDLs
	 *	read from and written to the database (used for free space management).
	 */
Howard Chu's avatar
Howard Chu committed
453
#define MDB_DEBUG 0
454
#endif
Howard Chu's avatar
Howard Chu committed
455

456
#if MDB_DEBUG
457
static int mdb_debug;
458
static txnid_t mdb_debug_start;
459

460
461
462
463
464
	/**	Print a debug message with printf formatting.
	 *	Requires double parenthesis around 2 or more args.
	 */
# define DPRINTF(args) ((void) ((mdb_debug) && DPRINTF0 args))
# define DPRINTF0(fmt, ...) \
Hallvard Furuseth's avatar
Hallvard Furuseth committed
465
	fprintf(stderr, "%s:%d " fmt "\n", mdb_func_, __LINE__, __VA_ARGS__)
Howard Chu's avatar
Howard Chu committed
466
#else
467
# define DPRINTF(args)	((void) 0)
Howard Chu's avatar
Howard Chu committed
468
#endif
Howard Chu's avatar
Howard Chu committed
469
470
471
	/**	Print a debug string.
	 *	The string is printed literally, with no format processing.
	 */
472
#define DPUTS(arg)	DPRINTF(("%s", arg))
473
474
475
	/** Debuging output value of a cursor DBI: Negative in a sub-cursor. */
#define DDBI(mc) \
	(((mc)->mc_flags & C_SUB) ? -(int)(mc)->mc_dbi : (int)(mc)->mc_dbi)
Howard Chu's avatar
Howard Chu committed
476
/** @} */
Howard Chu's avatar
Howard Chu committed
477

478
479
	/**	@brief The maximum size of a database page.
	 *
Hallvard Furuseth's avatar
Hallvard Furuseth committed
480
481
	 *	It is 32k or 64k, since value-PAGEBASE must fit in
	 *	#MDB_page.%mp_upper.
482
483
484
485
	 *
	 *	LMDB will use database pages < OS pages if needed.
	 *	That causes more I/O in write transactions: The OS must
	 *	know (read) the whole page before writing a partial page.
Howard Chu's avatar
Howard Chu committed
486
487
488
489
490
491
492
493
	 *
	 *	Note that we don't currently support Huge pages. On Linux,
	 *	regular data files cannot use Huge pages, and in general
	 *	Huge pages aren't actually pageable. We rely on the OS
	 *	demand-pager to read our data and page it out when memory
	 *	pressure from other processes is high. So until OSs have
	 *	actual paging support for Huge pages, they're not viable.
	 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
494
#define MAX_PAGESIZE	 (PAGEBASE ? 0x10000 : 0x8000)
Howard Chu's avatar
Howard Chu committed
495
496
497
498
499
500
501
502
503
504
505
506
507

	/** The minimum number of keys required in a database page.
	 *	Setting this to a larger value will place a smaller bound on the
	 *	maximum size of a data item. Data items larger than this size will
	 *	be pushed into overflow pages instead of being stored directly in
	 *	the B-tree node. This value used to default to 4. With a page size
	 *	of 4096 bytes that meant that any item larger than 1024 bytes would
	 *	go into an overflow page. That also meant that on average 2-3KB of
	 *	each overflow page was wasted space. The value cannot be lower than
	 *	2 because then there would no longer be a tree structure. With this
	 *	value, items larger than 2KB will go into overflow pages, and on
	 *	average only 1KB will be wasted.
	 */
Howard Chu's avatar
Howard Chu committed
508
#define MDB_MINKEYS	 2
Howard Chu's avatar
Howard Chu committed
509

Howard Chu's avatar
Howard Chu committed
510
	/**	A stamp that identifies a file as an LMDB file.
Howard Chu's avatar
Howard Chu committed
511
512
513
	 *	There's nothing special about this value other than that it is easily
	 *	recognizable, and it will reflect any byte order mismatches.
	 */
Howard Chu's avatar
Howard Chu committed
514
#define MDB_MAGIC	 0xBEEFC0DE
Howard Chu's avatar
Howard Chu committed
515

516
	/**	The version number for a database's datafile format. */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
517
#define MDB_DATA_VERSION	 ((MDB_DEVEL) ? 999 : 1)
518
	/**	The version number for a database's lockfile format. */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
519
#define MDB_LOCK_VERSION	 ((MDB_DEVEL) ? 999 : 1)
Howard Chu's avatar
Howard Chu committed
520

521
	/**	@brief The max size of a key we can write, or 0 for computed max.
522
	 *
523
524
525
526
527
528
529
530
531
	 *	This macro should normally be left alone or set to 0.
	 *	Note that a database with big keys or dupsort data cannot be
	 *	reliably modified by a liblmdb which uses a smaller max.
	 *	The default is 511 for backwards compat, or 0 when #MDB_DEVEL.
	 *
	 *	Other values are allowed, for backwards compat.  However:
	 *	A value bigger than the computed max can break if you do not
	 *	know what you are doing, and liblmdb <= 0.9.10 can break when
	 *	modifying a DB with keys/dupsort data bigger than its max.
532
	 *
533
534
535
	 *	Data items in an #MDB_DUPSORT database are also limited to
	 *	this size, since they're actually keys of a sub-DB.  Keys and
	 *	#MDB_DUPSORT data items must fit on a node in a regular page.
Howard Chu's avatar
Howard Chu committed
536
	 */
537
#ifndef MDB_MAXKEYSIZE
538
#define MDB_MAXKEYSIZE	 ((MDB_DEVEL) ? 0 : 511)
539
540
541
542
543
544
545
#endif

	/**	The maximum size of a key we can write to the environment. */
#if MDB_MAXKEYSIZE
#define ENV_MAXKEY(env)	(MDB_MAXKEYSIZE)
#else
#define ENV_MAXKEY(env)	((env)->me_maxkey)
546
#endif
Howard Chu's avatar
Howard Chu committed
547

548
549
550
551
552
553
	/**	@brief The maximum size of a data item.
	 *
	 *	We only store a 32 bit value for node sizes.
	 */
#define MAXDATASIZE	0xffffffffUL

Howard Chu's avatar
Howard Chu committed
554
#if MDB_DEBUG
555
556
557
558
	/**	Key size which fits in a #DKBUF.
	 *	@ingroup debug
	 */
#define DKBUF_MAXKEYSIZE ((MDB_MAXKEYSIZE) > 0 ? (MDB_MAXKEYSIZE) : 511)
Howard Chu's avatar
Howard Chu committed
559
560
561
562
	/**	A key buffer.
	 *	@ingroup debug
	 *	This is used for printing a hex dump of a key's contents.
	 */
563
#define DKBUF	char kbuf[DKBUF_MAXKEYSIZE*2+1]
Howard Chu's avatar
Howard Chu committed
564
565
566
567
	/**	Display a key in hex.
	 *	@ingroup debug
	 *	Invoke a function to display a key in hex.
	 */
Howard Chu's avatar
Howard Chu committed
568
569
#define	DKEY(x)	mdb_dkey(x, kbuf)
#else
Howard Chu's avatar
Howard Chu committed
570
#define	DKBUF
Howard Chu's avatar
Howard Chu committed
571
#define DKEY(x)	0
Howard Chu's avatar
Howard Chu committed
572
#endif
Howard Chu's avatar
Howard Chu committed
573

Howard Chu's avatar
Howard Chu committed
574
575
576
	/** An invalid page number.
	 *	Mainly used to denote an empty tree.
	 */
577
#define P_INVALID	 (~(pgno_t)0)
Howard Chu's avatar
Howard Chu committed
578

579
	/** Test if the flags \b f are set in a flag word \b w. */
Howard Chu's avatar
Howard Chu committed
580
581
#define F_ISSET(w, f)	 (((w) & (f)) == (f))

582
583
584
	/** Round \b n up to an even number. */
#define EVEN(n)		(((n) + 1U) & -2) /* sign-extending -2 to match n+1U */

Howard Chu's avatar
Howard Chu committed
585
586
587
588
	/**	Used for offsets within a single page.
	 *	Since memory pages are typically 4 or 8KB in size, 12-13 bits,
	 *	this is plenty.
	 */
Howard Chu's avatar
Howard Chu committed
589
590
typedef uint16_t	 indx_t;

Howard Chu's avatar
Howard Chu committed
591
592
593
594
	/**	Default size of memory map.
	 *	This is certainly too small for any actual applications. Apps should always set
	 *	the size explicitly using #mdb_env_set_mapsize().
	 */
Howard Chu's avatar
Howard Chu committed
595
596
#define DEFAULT_MAPSIZE	1048576

Howard Chu's avatar
Howard Chu committed
597
598
599
600
601
602
603
/**	@defgroup readers	Reader Lock Table
 *	Readers don't acquire any locks for their data access. Instead, they
 *	simply record their transaction ID in the reader table. The reader
 *	mutex is needed just to find an empty slot in the reader table. The
 *	slot's address is saved in thread-specific data so that subsequent read
 *	transactions started by the same thread need no further locking to proceed.
 *
Howard Chu's avatar
Howard Chu committed
604
605
 *	If #MDB_NOTLS is set, the slot address is not saved in thread-specific data.
 *
Howard Chu's avatar
Howard Chu committed
606
607
 *	No reader table is used if the database is on a read-only filesystem, or
 *	if #MDB_NOLOCK is set.
608
 *
Howard Chu's avatar
Howard Chu committed
609
610
611
 *	Since the database uses multi-version concurrency control, readers don't
 *	actually need any locking. This table is used to keep track of which
 *	readers are using data from which old transactions, so that we'll know
612
613
 *	when a particular old transaction is no longer in use. Old transactions
 *	that have discarded any data pages can then have those pages reclaimed
Howard Chu's avatar
Howard Chu committed
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
 *	for use by a later write transaction.
 *
 *	The lock table is constructed such that reader slots are aligned with the
 *	processor's cache line size. Any slot is only ever used by one thread.
 *	This alignment guarantees that there will be no contention or cache
 *	thrashing as threads update their own slot info, and also eliminates
 *	any need for locking when accessing a slot.
 *
 *	A writer thread will scan every slot in the table to determine the oldest
 *	outstanding reader transaction. Any freed pages older than this will be
 *	reclaimed by the writer. The writer doesn't use any locks when scanning
 *	this table. This means that there's no guarantee that the writer will
 *	see the most up-to-date reader info, but that's not required for correct
 *	operation - all we need is to know the upper bound on the oldest reader,
 *	we don't care at all about the newest reader. So the only consequence of
 *	reading stale information here is that old pages might hang around a
 *	while longer before being reclaimed. That's actually good anyway, because
 *	the longer we delay reclaiming old pages, the more likely it is that a
 *	string of contiguous pages can be found after coalescing old pages from
 *	many old transactions together.
 *	@{
 */
	/**	Number of slots in the reader table.
	 *	This value was chosen somewhat arbitrarily. 126 readers plus a
	 *	couple mutexes fit exactly into 8KB on my development machine.
	 *	Applications should set the table size using #mdb_env_set_maxreaders().
	 */
#define DEFAULT_READERS	126

	/**	The size of a CPU cache line in bytes. We want our lock structures
	 *	aligned to this size to avoid false cache line sharing in the
	 *	lock table.
	 *	This value works for most CPUs. For Itanium this should be 128.
	 */
Howard Chu's avatar
Howard Chu committed
648
#ifndef CACHELINE
Howard Chu's avatar
Howard Chu committed
649
#define CACHELINE	64
Howard Chu's avatar
Howard Chu committed
650
651
#endif

Howard Chu's avatar
Howard Chu committed
652
653
654
655
656
657
658
659
	/**	The information we store in a single slot of the reader table.
	 *	In addition to a transaction ID, we also record the process and
	 *	thread ID that owns a slot, so that we can detect stale information,
	 *	e.g. threads or processes that went away without cleaning up.
	 *	@note We currently don't check for stale records. We simply re-init
	 *	the table when we know that we're the only process opening the
	 *	lock file.
	 */
Howard Chu's avatar
Howard Chu committed
660
typedef struct MDB_rxbody {
661
	/**	Current Transaction ID when this transaction began, or (txnid_t)-1.
Howard Chu's avatar
Howard Chu committed
662
663
664
665
666
667
	 *	Multiple readers that start at the same time will probably have the
	 *	same ID here. Again, it's not important to exclude them from
	 *	anything; all we need to know is which version of the DB they
	 *	started from so we can avoid overwriting any data used in that
	 *	particular version.
	 */
668
	volatile txnid_t		mrb_txnid;
Howard Chu's avatar
Howard Chu committed
669
	/** The process ID of the process owning this reader txn. */
670
	volatile MDB_PID_T	mrb_pid;
Howard Chu's avatar
Howard Chu committed
671
	/** The thread ID of the thread owning this txn. */
672
	volatile MDB_THR_T	mrb_tid;
Howard Chu's avatar
Howard Chu committed
673
674
} MDB_rxbody;

Howard Chu's avatar
Howard Chu committed
675
	/** The actual reader record, with cacheline padding. */
Howard Chu's avatar
Howard Chu committed
676
typedef struct MDB_reader {
Howard Chu's avatar
Howard Chu committed
677
678
	union {
		MDB_rxbody mrx;
Howard Chu's avatar
Howard Chu committed
679
		/** shorthand for mrb_txnid */
Howard Chu's avatar
Howard Chu committed
680
681
682
#define	mr_txnid	mru.mrx.mrb_txnid
#define	mr_pid	mru.mrx.mrb_pid
#define	mr_tid	mru.mrx.mrb_tid
Howard Chu's avatar
Howard Chu committed
683
		/** cache line alignment */
Howard Chu's avatar
Howard Chu committed
684
685
		char pad[(sizeof(MDB_rxbody)+CACHELINE-1) & ~(CACHELINE-1)];
	} mru;
Howard Chu's avatar
Howard Chu committed
686
687
} MDB_reader;

Howard Chu's avatar
Howard Chu committed
688
689
690
691
692
693
694
	/** The header for the reader table.
	 *	The table resides in a memory-mapped file. (This is a different file
	 *	than is used for the main database.)
	 *
	 *	For POSIX the actual mutexes reside in the shared memory of this
	 *	mapped file. On Windows, mutexes are named objects allocated by the
	 *	kernel; we store the mutex names in this mapped file so that other
Howard Chu's avatar
Howard Chu committed
695
	 *	processes can grab them. This same approach is also used on
Howard Chu's avatar
Howard Chu committed
696
	 *	MacOSX/Darwin (using named semaphores) since MacOSX doesn't support
Howard Chu's avatar
Howard Chu committed
697
698
699
700
	 *	process-shared POSIX mutexes. For these cases where a named object
	 *	is used, the object name is derived from a 64 bit FNV hash of the
	 *	environment pathname. As such, naming collisions are extremely
	 *	unlikely. If a collision occurs, the results are unpredictable.
Howard Chu's avatar
Howard Chu committed
701
	 */
Howard Chu's avatar
Howard Chu committed
702
typedef struct MDB_txbody {
Howard Chu's avatar
Howard Chu committed
703
		/** Stamp identifying this as an LMDB file. It must be set
Howard Chu's avatar
Howard Chu committed
704
		 *	to #MDB_MAGIC. */
Howard Chu's avatar
Howard Chu committed
705
	uint32_t	mtb_magic;
706
707
		/** Format of this lock file. Must be set to #MDB_LOCK_FORMAT. */
	uint32_t	mtb_format;
708
#if defined(_WIN32)
Howard Chu's avatar
Howard Chu committed
709
	char	mtb_rmname[MNAME_LEN];
710
711
#elif defined(MDB_USE_SYSV_SEM)
	int 	mtb_semid;
712
	int		mtb_rlocked;
Howard Chu's avatar
Howard Chu committed
713
#else
Howard Chu's avatar
Howard Chu committed
714
		/** Mutex protecting access to this table.
715
		 *	This is the reader table lock used with LOCK_MUTEX().
Howard Chu's avatar
Howard Chu committed
716
		 */
717
	mdb_mutex_t	mtb_rmutex;
Howard Chu's avatar
Howard Chu committed
718
#endif
Howard Chu's avatar
Howard Chu committed
719
720
721
722
		/**	The ID of the last transaction committed to the database.
		 *	This is recorded here only for convenience; the value can always
		 *	be determined by reading the main database meta pages.
		 */
723
	volatile txnid_t		mtb_txnid;
Howard Chu's avatar
Howard Chu committed
724
725
726
727
		/** The number of slots that have been used in the reader table.
		 *	This always records the maximum count, it is not decremented
		 *	when readers release their slots.
		 */
728
	volatile unsigned	mtb_numreaders;
Howard Chu's avatar
Howard Chu committed
729
730
} MDB_txbody;

Howard Chu's avatar
Howard Chu committed
731
	/** The actual reader table definition. */
Howard Chu's avatar
Howard Chu committed
732
typedef struct MDB_txninfo {
Howard Chu's avatar
Howard Chu committed
733
734
735
	union {
		MDB_txbody mtb;
#define mti_magic	mt1.mtb.mtb_magic
736
#define mti_format	mt1.mtb.mtb_format
Hallvard Furuseth's avatar
Hallvard Furuseth committed
737
#define mti_rmutex	mt1.mtb.mtb_rmutex
Howard Chu's avatar
Howard Chu committed
738
#define mti_rmname	mt1.mtb.mtb_rmname
Howard Chu's avatar
Howard Chu committed
739
740
#define mti_txnid	mt1.mtb.mtb_txnid
#define mti_numreaders	mt1.mtb.mtb_numreaders
741
742
#ifdef MDB_USE_SYSV_SEM
#define	mti_semid	mt1.mtb.mtb_semid
743
744
745
746
#define	mti_rlocked	mt1.mtb.mtb_rlocked
#endif
		char pad[(sizeof(MDB_txbody)+CACHELINE-1) & ~(CACHELINE-1)];
	} mt1;
Howard Chu's avatar
Howard Chu committed
747
	union {
748
#if defined(_WIN32)
Howard Chu's avatar
Howard Chu committed
749
		char mt2_wmname[MNAME_LEN];
Howard Chu's avatar
Howard Chu committed
750
#define	mti_wmname	mt2.mt2_wmname
751
752
753
#elif defined MDB_USE_SYSV_SEM
		int mt2_wlocked;
#define mti_wlocked	mt2.mt2_wlocked
Howard Chu's avatar
Howard Chu committed
754
#else
755
		mdb_mutex_t	mt2_wmutex;
Howard Chu's avatar
Howard Chu committed
756
#define mti_wmutex	mt2.mt2_wmutex
Howard Chu's avatar
Howard Chu committed
757
#endif
758
		char pad[(MNAME_LEN+CACHELINE-1) & ~(CACHELINE-1)];
Howard Chu's avatar
Howard Chu committed
759
760
	} mt2;
	MDB_reader	mti_readers[1];
Howard Chu's avatar
Howard Chu committed
761
} MDB_txninfo;
762
763
764
765
766
767

	/** Lockfile format signature: version, features and field layout */
#define MDB_LOCK_FORMAT \
	((uint32_t) \
	 ((MDB_LOCK_VERSION) \
	  /* Flags which describe functionality */ \
768
	  + (SYSV_SEM_FLAG << 18) \
769
	  + (((MDB_PIDLOCK) != 0) << 16)))
Howard Chu's avatar
Howard Chu committed
770
/** @} */
Howard Chu's avatar
Howard Chu committed
771

Howard Chu's avatar
Howard Chu committed
772
/** Common header for all page types.
Howard Chu's avatar
Howard Chu committed
773
 * Overflow records occupy a number of contiguous pages with no
Howard Chu's avatar
Howard Chu committed
774
775
 * headers on any page after the first.
 */
Howard Chu's avatar
Howard Chu committed
776
typedef struct MDB_page {
777
778
#define	mp_pgno	mp_p.p_pgno
#define	mp_next	mp_p.p_next
Howard Chu's avatar
Howard Chu committed
779
	union {
780
		pgno_t		p_pgno;	/**< page number */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
781
		struct MDB_page *p_next; /**< for in-memory list of freed pages */
782
	} mp_p;
Howard Chu's avatar
Howard Chu committed
783
	uint16_t	mp_pad;
Howard Chu's avatar
Howard Chu committed
784
785
786
787
788
/**	@defgroup mdb_page	Page Flags
 *	@ingroup internal
 *	Flags for the page headers.
 *	@{
 */
Howard Chu's avatar
Howard Chu committed
789
790
791
792
#define	P_BRANCH	 0x01		/**< branch page */
#define	P_LEAF		 0x02		/**< leaf page */
#define	P_OVERFLOW	 0x04		/**< overflow page */
#define	P_META		 0x08		/**< meta page */
793
#define	P_DIRTY		 0x10		/**< dirty page, also set for #P_SUBP pages */
Howard Chu's avatar
Howard Chu committed
794
#define	P_LEAF2		 0x20		/**< for #MDB_DUPFIXED records */
Howard Chu's avatar
Howard Chu committed
795
#define	P_SUBP		 0x40		/**< for #MDB_DUPSORT sub-pages */
Howard Chu's avatar
Howard Chu committed
796
#define	P_LOOSE		 0x4000		/**< page was dirtied then freed, can be reused */
Howard Chu's avatar
Howard Chu committed
797
#define	P_KEEP		 0x8000		/**< leave this page alone during spill */
Howard Chu's avatar
Howard Chu committed
798
/** @} */
Howard Chu's avatar
Howard Chu committed
799
	uint16_t	mp_flags;		/**< @ref mdb_page */
800
801
802
#define mp_lower	mp_pb.pb.pb_lower
#define mp_upper	mp_pb.pb.pb_upper
#define mp_pages	mp_pb.pb_pages
Howard Chu's avatar
Howard Chu committed
803
	union {
Howard Chu's avatar
Howard Chu committed
804
		struct {
805
806
807
808
809
			indx_t		pb_lower;		/**< lower bound of free space */
			indx_t		pb_upper;		/**< upper bound of free space */
		} pb;
		uint32_t	pb_pages;	/**< number of overflow pages */
	} mp_pb;
Howard Chu's avatar
Howard Chu committed
810
	indx_t		mp_ptrs[1];		/**< dynamic size */
Howard Chu's avatar
Howard Chu committed
811
812
} MDB_page;

Howard Chu's avatar
Howard Chu committed
813
	/** Size of the page header, excluding dynamic data at the end */
814
#define PAGEHDRSZ	 ((unsigned) offsetof(MDB_page, mp_ptrs))
Howard Chu's avatar
Howard Chu committed
815

Howard Chu's avatar
Howard Chu committed
816
817
818
	/** Address of first usable data byte in a page, after the header */
#define METADATA(p)	 ((void *)((char *)(p) + PAGEHDRSZ))

819
	/** ITS#7713, change PAGEBASE to handle 65536 byte pages */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
820
#define	PAGEBASE	((MDB_DEVEL) ? PAGEHDRSZ : 0)
821

Howard Chu's avatar
Howard Chu committed
822
	/** Number of nodes on a page */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
823
#define NUMKEYS(p)	 (((p)->mp_lower - (PAGEHDRSZ-PAGEBASE)) >> 1)
Howard Chu's avatar
Howard Chu committed
824
825

	/** The amount of space remaining in the page */
Howard Chu's avatar
Howard Chu committed
826
#define SIZELEFT(p)	 (indx_t)((p)->mp_upper - (p)->mp_lower)
Howard Chu's avatar
Howard Chu committed
827
828

	/** The percentage of space used in the page, in tenths of a percent. */
Howard Chu's avatar
Howard Chu committed
829
830
#define PAGEFILL(env, p) (1000L * ((env)->me_psize - PAGEHDRSZ - SIZELEFT(p)) / \
				((env)->me_psize - PAGEHDRSZ))
Howard Chu's avatar
Howard Chu committed
831
832
833
834
835
836
	/** The minimum page fill factor, in tenths of a percent.
	 *	Pages emptier than this are candidates for merging.
	 */
#define FILL_THRESHOLD	 250

	/** Test if a page is a leaf page */
Howard Chu's avatar
Howard Chu committed
837
#define IS_LEAF(p)	 F_ISSET((p)->mp_flags, P_LEAF)
Howard Chu's avatar
Howard Chu committed
838
	/** Test if a page is a LEAF2 page */
Howard Chu's avatar
Howard Chu committed
839
#define IS_LEAF2(p)	 F_ISSET((p)->mp_flags, P_LEAF2)
Howard Chu's avatar
Howard Chu committed
840
	/** Test if a page is a branch page */
Howard Chu's avatar
Howard Chu committed
841
#define IS_BRANCH(p)	 F_ISSET((p)->mp_flags, P_BRANCH)
Howard Chu's avatar
Howard Chu committed
842
	/** Test if a page is an overflow page */
Howard Chu's avatar
Howard Chu committed
843
#define IS_OVERFLOW(p)	 F_ISSET((p)->mp_flags, P_OVERFLOW)
Howard Chu's avatar
Howard Chu committed
844
845
	/** Test if a page is a sub page */
#define IS_SUBP(p)	 F_ISSET((p)->mp_flags, P_SUBP)
Howard Chu's avatar
Howard Chu committed
846

Howard Chu's avatar
Howard Chu committed
847
	/** The number of overflow pages needed to store the given size. */
848
#define OVPAGES(size, psize)	((PAGEHDRSZ-1 + (size)) / (psize) + 1)
Howard Chu's avatar
Howard Chu committed
849

850
	/** Link in #MDB_txn.%mt_loose_pgs list */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
851
#define NEXT_LOOSE_PAGE(p)		(*(MDB_page **)((p) + 2))
852

Howard Chu's avatar
Howard Chu committed
853
	/** Header for a single key/data pair within a page.
854
855
	 * Used in pages of type #P_BRANCH and #P_LEAF without #P_LEAF2.
	 * We guarantee 2-byte alignment for 'MDB_node's.
Howard Chu's avatar
Howard Chu committed
856
857
858
859
	 */
typedef struct MDB_node {
	/** lo and hi are used for data size on leaf nodes and for
	 * child pgno on branch nodes. On 64 bit platforms, flags
860
	 * is also used for pgno. (Branch nodes have no flags).
Howard Chu's avatar
Howard Chu committed
861
	 * They are in host byte order in case that lets some
862
	 * accesses be optimized into a 32-bit word access.
Howard Chu's avatar
Howard Chu committed
863
	 */
864
865
866
867
868
#if BYTE_ORDER == LITTLE_ENDIAN
	unsigned short	mn_lo, mn_hi;	/**< part of data size or pgno */
#else
	unsigned short	mn_hi, mn_lo;
#endif
Howard Chu's avatar
Howard Chu committed
869
870
871
872
873
/** @defgroup mdb_node Node Flags
 *	@ingroup internal
 *	Flags for node headers.
 *	@{
 */
Howard Chu's avatar
Howard Chu committed
874
875
876
#define F_BIGDATA	 0x01			/**< data put on overflow page */
#define F_SUBDATA	 0x02			/**< data is a sub-database */
#define F_DUPDATA	 0x04			/**< data has duplicates */
Howard Chu's avatar
Howard Chu committed
877
878

/** valid flags for #mdb_node_add() */
879
#define	NODE_ADD_FLAGS	(F_DUPDATA|F_SUBDATA|MDB_RESERVE|MDB_APPEND)
Howard Chu's avatar
Howard Chu committed
880

Howard Chu's avatar
Howard Chu committed
881
882
/** @} */
	unsigned short	mn_flags;		/**< @ref mdb_node */
Howard Chu's avatar
Howard Chu committed
883
884
885
886
887
888
889
	unsigned short	mn_ksize;		/**< key size */
	char		mn_data[1];			/**< key and data are appended here */
} MDB_node;

	/** Size of the node header, excluding dynamic data at the end */
#define NODESIZE	 offsetof(MDB_node, mn_data)

890
891
892
	/** Bit position of top word in page number, for shifting mn_flags */
#define PGNO_TOPWORD ((pgno_t)-1 > 0xffffffffu ? 32 : 0)

Howard Chu's avatar
Howard Chu committed
893
	/** Size of a node in a branch page with a given key.
Howard Chu's avatar
Howard Chu committed
894
895
896
897
	 *	This is just the node header plus the key, there is no data.
	 */
#define INDXSIZE(k)	 (NODESIZE + ((k) == NULL ? 0 : (k)->mv_size))

Howard Chu's avatar
Howard Chu committed
898
	/** Size of a node in a leaf page with a given key and data.
Howard Chu's avatar
Howard Chu committed
899
900
901
902
	 *	This is node header plus key plus data size.
	 */
#define LEAFSIZE(k, d)	 (NODESIZE + (k)->mv_size + (d)->mv_size)

Howard Chu's avatar
Howard Chu committed
903
	/** Address of node \b i in page \b p */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
904
#define NODEPTR(p, i)	 ((MDB_node *)((char *)(p) + (p)->mp_ptrs[i] + PAGEBASE))
Howard Chu's avatar
Howard Chu committed
905
906
907
908
909
910
911
912

	/** Address of the key for the node */
#define NODEKEY(node)	 (void *)((node)->mn_data)

	/** Address of the data for a node */
#define NODEDATA(node)	 (void *)((char *)(node)->mn_data + (node)->mn_ksize)

	/** Get the page number pointed to by a branch node */
913
914
915
#define NODEPGNO(node) \
	((node)->mn_lo | ((pgno_t) (node)->mn_hi << 16) | \
	 (PGNO_TOPWORD ? ((pgno_t) (node)->mn_flags << PGNO_TOPWORD) : 0))
Howard Chu's avatar
Howard Chu committed
916
917
918
	/** Set the page number in a branch node */
#define SETPGNO(node,pgno)	do { \
	(node)->mn_lo = (pgno) & 0xffff; (node)->mn_hi = (pgno) >> 16; \
919
	if (PGNO_TOPWORD) (node)->mn_flags = (pgno) >> PGNO_TOPWORD; } while(0)
Howard Chu's avatar
Howard Chu committed
920
921
922
923
924
925
926
927
928

	/** Get the size of the data in a leaf node */
#define NODEDSZ(node)	 ((node)->mn_lo | ((unsigned)(node)->mn_hi << 16))
	/** Set the size of the data for a leaf node */
#define SETDSZ(node,size)	do { \
	(node)->mn_lo = (size) & 0xffff; (node)->mn_hi = (size) >> 16;} while(0)
	/** The size of a key in a node */
#define NODEKSZ(node)	 ((node)->mn_ksize)

Howard Chu's avatar
Howard Chu committed
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
	/** Copy a page number from src to dst */
#ifdef MISALIGNED_OK
#define COPY_PGNO(dst,src)	dst = src
#else
#if SIZE_MAX > 4294967295UL
#define COPY_PGNO(dst,src)	do { \
	unsigned short *s, *d;	\
	s = (unsigned short *)&(src);	\
	d = (unsigned short *)&(dst);	\
	*d++ = *s++;	\
	*d++ = *s++;	\
	*d++ = *s++;	\
	*d = *s;	\
} while (0)
#else
#define COPY_PGNO(dst,src)	do { \
	unsigned short *s, *d;	\
	s = (unsigned short *)&(src);	\
	d = (unsigned short *)&(dst);	\
	*d++ = *s++;	\
	*d = *s;	\
} while (0)
#endif
#endif
Howard Chu's avatar
Howard Chu committed
953
954
955
956
957
958
	/** The address of a key in a LEAF2 page.
	 *	LEAF2 pages are used for #MDB_DUPFIXED sorted-duplicate sub-DBs.
	 *	There are no node headers, keys are stored contiguously.
	 */
#define LEAF2KEY(p, i, ks)	((char *)(p) + PAGEHDRSZ + ((i)*(ks)))

Howard Chu's avatar
Howard Chu committed
959
960
961
962
963
964
	/** Set the \b node's key into \b keyptr, if requested. */
#define MDB_GET_KEY(node, keyptr)	{ if ((keyptr) != NULL) { \
	(keyptr)->mv_size = NODEKSZ(node); (keyptr)->mv_data = NODEKEY(node); } }

	/** Set the \b node's key into \b key. */
#define MDB_GET_KEY2(node, key)	{ key.mv_size = NODEKSZ(node); key.mv_data = NODEKEY(node); }
Howard Chu's avatar
Howard Chu committed
965
966

	/** Information about a single database in the environment. */
Howard Chu's avatar
Howard Chu committed
967
typedef struct MDB_db {
Howard Chu's avatar
Howard Chu committed
968
	uint32_t	md_pad;		/**< also ksize for LEAF2 pages */
969
	uint16_t	md_flags;	/**< @ref mdb_dbi_open */
Howard Chu's avatar
Howard Chu committed
970
	uint16_t	md_depth;	/**< depth of this tree */
971
972
973
974
	pgno_t		md_branch_pages;	/**< number of internal pages */
	pgno_t		md_leaf_pages;		/**< number of leaf pages */
	pgno_t		md_overflow_pages;	/**< number of overflow pages */
	size_t		md_entries;		/**< number of data items */
Howard Chu's avatar
Howard Chu committed
975
	pgno_t		md_root;		/**< the root page of this tree */
Howard Chu's avatar
Howard Chu committed
976
977
} MDB_db;

978
	/** mdb_dbi_open flags */
979
980
#define MDB_VALID	0x8000		/**< DB handle is valid, for me_dbflags */
#define PERSISTENT_FLAGS	(0xffff & ~(MDB_VALID))
981
982
983
#define VALID_FLAGS	(MDB_REVERSEKEY|MDB_DUPSORT|MDB_INTEGERKEY|MDB_DUPFIXED|\
	MDB_INTEGERDUP|MDB_REVERSEDUP|MDB_CREATE)

Howard Chu's avatar
Howard Chu committed
984
	/** Handle for the DB used to track free pages. */
Howard Chu's avatar
Howard Chu committed
985
#define	FREE_DBI	0
Howard Chu's avatar
Howard Chu committed
986
	/** Handle for the default DB. */
Howard Chu's avatar
Howard Chu committed
987
988
#define	MAIN_DBI	1

989
990
991
992
	/** Meta page content.
	 *	A meta page is the start point for accessing a database snapshot.
	 *	Pages 0-1 are meta pages. Transaction N writes meta page #(N % 2).
	 */
Howard Chu's avatar
Howard Chu committed
993
typedef struct MDB_meta {
Howard Chu's avatar
Howard Chu committed
994
		/** Stamp identifying this as an LMDB file. It must be set
Howard Chu's avatar
Howard Chu committed
995
		 *	to #MDB_MAGIC. */
Howard Chu's avatar
Howard Chu committed
996
	uint32_t	mm_magic;
Hallvard Furuseth's avatar
Hallvard Furuseth committed
997
		/** Version number of this file. Must be set to #MDB_DATA_VERSION. */
Howard Chu's avatar
Howard Chu committed
998
	uint32_t	mm_version;
Howard Chu's avatar
Howard Chu committed
999
1000
1001
1002
	void		*mm_address;		/**< address for fixed mapping */
	size_t		mm_mapsize;			/**< size of mmap region */
	MDB_db		mm_dbs[2];			/**< first is free space, 2nd is main db */
	/** The size of pages used in this DB */
Howard Chu's avatar
Howard Chu committed
1003
#define	mm_psize	mm_dbs[0].md_pad
Howard Chu's avatar
Howard Chu committed
1004
	/** Any persistent environment flags. @ref mdb_env */
Howard Chu's avatar
Howard Chu committed
1005
#define	mm_flags	mm_dbs[0].md_flags
Howard Chu's avatar
Howard Chu committed
1006
	pgno_t		mm_last_pg;			/**< last used page in file */
1007
	volatile txnid_t	mm_txnid;	/**< txnid that committed this page */
Howard Chu's avatar
Howard Chu committed
1008
1009
} MDB_meta;

1010
	/** Buffer for a stack-allocated meta page.
1011
1012
1013
1014
	 *	The members define size and alignment, and silence type
	 *	aliasing warnings.  They are not used directly; that could
	 *	mean incorrectly using several union members in parallel.
	 */
1015
typedef union MDB_metabuf {
1016
1017
1018
1019
1020
	MDB_page	mb_page;
	struct {
		char		mm_pad[PAGEHDRSZ];
		MDB_meta	mm_meta;
	} mb_metabuf;
1021
} MDB_metabuf;
1022

Howard Chu's avatar
Howard Chu committed
1023
1024
1025
1026
1027
1028
1029
1030
1031
	/** Auxiliary DB info.
	 *	The information here is mostly static/read-only. There is
	 *	only a single copy of this record in the environment.
	 */
typedef struct MDB_dbx {
	MDB_val		md_name;		/**< name of the database */
	MDB_cmp_func	*md_cmp;	/**< function for comparing keys */
	MDB_cmp_func	*md_dcmp;	/**< function for comparing data items */
	MDB_rel_func	*md_rel;	/**< user relocate function */
1032
	void		*md_relctx;		/**< user-provided context for md_rel */
Howard Chu's avatar
Howard Chu committed
1033
} MDB_dbx;
Howard Chu's avatar
Howard Chu committed
1034

Howard Chu's avatar
Howard Chu committed
1035
1036
1037
1038
	/** A database transaction.
	 *	Every operation requires a transaction handle.
	 */
struct MDB_txn {
1039
1040
	MDB_txn		*mt_parent;		/**< parent of a nested txn */
	MDB_txn		*mt_child;		/**< nested txn under this txn */
Howard Chu's avatar
Howard Chu committed
1041
1042
1043
1044
1045
	pgno_t		mt_next_pgno;	/**< next unallocated page */
	/** The ID of this transaction. IDs are integers incrementing from 1.
	 *	Only committed write transactions increment the ID. If a transaction
	 *	aborts, the ID may be re-used by the next writer.
	 */
1046
	txnid_t		mt_txnid;
Howard Chu's avatar
Howard Chu committed
1047
1048
1049
	MDB_env		*mt_env;		/**< the DB environment */
	/** The list of pages that became unused during this transaction.
	 */
1050
	MDB_IDL		mt_free_pgs;
Howard Chu's avatar
Howard Chu committed
1051
	/** The list of loose pages that became unused and may be reused
1052
	 *	in this transaction, linked through #NEXT_LOOSE_PAGE(page).
Howard Chu's avatar
Howard Chu committed
1053
1054
	 */
	MDB_page	*mt_loose_pgs;
1055
1056
	/* #Number of loose pages (#mt_loose_pgs) */
	int			mt_loose_count;
Hallvard Furuseth's avatar
Hallvard Furuseth committed
1057
	/** The sorted list of dirty pages we temporarily wrote to disk
1058
1059
	 *	because the dirty list was full. page numbers in here are
	 *	shifted left by 1, deleted slots have the LSB set.
Howard Chu's avatar
Howard Chu committed
1060
1061
	 */
	MDB_IDL		mt_spill_pgs;
Howard Chu's avatar
Howard Chu committed
1062
	union {
Hallvard Furuseth's avatar
Hallvard Furuseth committed
1063
1064
1065
1066
		/** For write txns: Modified pages. Sorted when not MDB_WRITEMAP. */
		MDB_ID2L	dirty_list;
		/** For read txns: This thread/txn's reader table slot, or NULL. */
		MDB_reader	*reader;
Howard Chu's avatar
Howard Chu committed
1067
1068
1069
1070
1071
	} mt_u;
	/** Array of records for each DB known in the environment. */
	MDB_dbx		*mt_dbxs;
	/** Array of MDB_db records for each known DB */
	MDB_db		*mt_dbs;
1072
1073
	/** Array of sequence numbers for each DB handle */
	unsigned int	*mt_dbiseqs;
Howard Chu's avatar
Howard Chu committed
1074
1075
1076
1077
/** @defgroup mt_dbflag	Transaction DB Flags
 *	@ingroup internal
 * @{
 */
1078
#define DB_DIRTY	0x01		/**< DB was modified or is DUPSORT data */
1079
1080
#define DB_STALE	0x02		/**< Named-DB record is older than txnID */
#define DB_NEW		0x04		/**< Named-DB handle opened in this txn */
1081
#define DB_VALID	0x08		/**< DB handle is valid, see also #MDB_VALID */
Howard Chu's avatar
Howard Chu committed
1082
/** @} */
1083
	/** In write txns, array of cursors for each DB */
Howard Chu's avatar
Howard Chu committed
1084
	MDB_cursor	**mt_cursors;
Howard Chu's avatar
Howard Chu committed
1085
1086
	/** Array of flags for each DB */
	unsigned char	*mt_dbflags;
Howard Chu's avatar
Howard Chu committed
1087
1088
1089
	/**	Number of DB records in use. This number only ever increments;
	 *	we don't decrement it when individual DB handles are closed.
	 */
1090
	MDB_dbi		mt_numdbs;
Howard Chu's avatar
Howard Chu committed
1091