mdb.c 248 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
/*
Howard Chu's avatar
Howard Chu committed
8
 * Copyright 2011-2014 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
73

#include <errno.h>
74
#include <limits.h>
Howard Chu's avatar
Howard Chu committed
75
#include <stddef.h>
76
#include <inttypes.h>
Howard Chu's avatar
Howard Chu committed
77
78
79
80
81
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
82

83
#if !(defined(BYTE_ORDER) || defined(__BYTE_ORDER))
84
#include <netinet/in.h>
85
86
87
#include <resolv.h>	/* defines BYTE_ORDER on HPUX and Solaris */
#endif

88
#if defined(__APPLE__) || defined (BSD)
89
90
91
92
# define MDB_USE_POSIX_SEM	1
# define MDB_FDATASYNC		fsync
#elif defined(ANDROID)
# define MDB_FDATASYNC		fsync
93
94
#endif

95
96
#ifndef _WIN32
#include <pthread.h>
97
#ifdef MDB_USE_POSIX_SEM
98
# define MDB_USE_HASH		1
Howard Chu's avatar
Howard Chu committed
99
100
101
102
#include <semaphore.h>
#endif
#endif

103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
#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
118
#ifndef BYTE_ORDER
Howard Chu's avatar
Howard Chu committed
119
120
121
122
123
124
125
126
127
128
129
130
# 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
131
#endif
Howard Chu's avatar
Howard Chu committed
132

Howard Chu's avatar
Howard Chu committed
133
134
135
136
137
#ifndef LITTLE_ENDIAN
#define LITTLE_ENDIAN	__LITTLE_ENDIAN
#endif
#ifndef BIG_ENDIAN
#define BIG_ENDIAN	__BIG_ENDIAN
138
139
#endif

Howard Chu's avatar
Howard Chu committed
140
#if defined(__i386) || defined(__x86_64) || defined(_M_IX86)
Howard Chu's avatar
Howard Chu committed
141
142
143
#define MISALIGNED_OK	1
#endif

Howard Chu's avatar
Howard Chu committed
144
#include "lmdb.h"
145
146
#include "midl.h"

Howard Chu's avatar
Howard Chu committed
147
148
#if (BYTE_ORDER == LITTLE_ENDIAN) == (BYTE_ORDER == BIG_ENDIAN)
# error "Unknown or unsupported endianness (BYTE_ORDER)"
149
150
151
152
#elif (-6 & 5) || CHAR_BIT != 8 || UINT_MAX < 0xffffffff || ULONG_MAX % 0xFFFF
# error "Two's complement, reasonably sized integer types, please"
#endif

153
154
155
156
157
158
159
#ifdef __GNUC__
/** Put infrequently used env functions in separate section */
#define	ESECT	__attribute__ ((section("text_env")))
#else
#define ESECT
#endif

Howard Chu's avatar
Howard Chu committed
160
/** @defgroup internal	LMDB Internals
161
162
 *	@{
 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
163
/** @defgroup compat	Compatibility Macros
Howard Chu's avatar
Howard Chu committed
164
165
166
167
 *	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.
168
169
 *	@{
 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
170
171
172
173
174
175
176
177
178
179
180

	/** 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

Howard Chu's avatar
Howard Chu committed
181
#ifdef _WIN32
Howard Chu's avatar
Howard Chu committed
182
#define MDB_USE_HASH	1
183
#define MDB_PIDLOCK	0
Howard Chu's avatar
Howard Chu committed
184
185
#define THREAD_RET	DWORD
#define pthread_t	HANDLE
Howard Chu's avatar
Howard Chu committed
186
#define pthread_mutex_t	HANDLE
Howard Chu's avatar
Howard Chu committed
187
#define pthread_cond_t	HANDLE
Howard Chu's avatar
Howard Chu committed
188
189
#define pthread_key_t	DWORD
#define pthread_self()	GetCurrentThreadId()
190
191
#define pthread_key_create(x,y)	\
	((*(x) = TlsAlloc()) == TLS_OUT_OF_INDEXES ? ErrCode() : 0)
Howard Chu's avatar
Howard Chu committed
192
193
#define pthread_key_delete(x)	TlsFree(x)
#define pthread_getspecific(x)	TlsGetValue(x)
194
#define pthread_setspecific(x,y)	(TlsSetValue(x,y) ? 0 : ErrCode())
Howard Chu's avatar
Howard Chu committed
195
196
#define pthread_mutex_unlock(x)	ReleaseMutex(*x)
#define pthread_mutex_lock(x)	WaitForSingleObject(*x, INFINITE)
Howard Chu's avatar
Howard Chu committed
197
#define pthread_cond_signal(x)	SetEvent(*x)
Howard Chu's avatar
Howard Chu committed
198
#define pthread_cond_wait(cond,mutex)	do{SignalObjectAndWait(*mutex, *cond, INFINITE, FALSE); WaitForSingleObject(*mutex, INFINITE);}while(0)
Howard Chu's avatar
Howard Chu committed
199
200
#define THREAD_CREATE(thr,start,arg)	thr=CreateThread(NULL,0,start,arg,0,NULL)
#define THREAD_FINISH(thr)	WaitForSingleObject(thr, INFINITE)
Howard Chu's avatar
Howard Chu committed
201
202
203
204
#define LOCK_MUTEX_R(env)	pthread_mutex_lock(&(env)->me_rmutex)
#define UNLOCK_MUTEX_R(env)	pthread_mutex_unlock(&(env)->me_rmutex)
#define LOCK_MUTEX_W(env)	pthread_mutex_lock(&(env)->me_wmutex)
#define UNLOCK_MUTEX_W(env)	pthread_mutex_unlock(&(env)->me_wmutex)
Howard Chu's avatar
Howard Chu committed
205
#define getpid()	GetCurrentProcessId()
206
#define	MDB_FDATASYNC(fd)	(!FlushFileBuffers(fd))
207
#define	MDB_MSYNC(addr,len,flags)	(!FlushViewOfFile(addr,len))
Howard Chu's avatar
Howard Chu committed
208
#define	ErrCode()	GetLastError()
Hallvard Furuseth's avatar
Hallvard Furuseth committed
209
#define GET_PAGESIZE(x) {SYSTEM_INFO si; GetSystemInfo(&si); (x) = si.dwPageSize;}
210
#define	close(fd)	(CloseHandle(fd) ? 0 : -1)
Howard Chu's avatar
Howard Chu committed
211
#define	munmap(ptr,len)	UnmapViewOfFile(ptr)
Hallvard Furuseth's avatar
Hallvard Furuseth committed
212
#ifdef PROCESS_QUERY_LIMITED_INFORMATION
Hallvard Furuseth's avatar
Hallvard Furuseth committed
213
214
215
216
#define MDB_PROCESS_QUERY_LIMITED_INFORMATION PROCESS_QUERY_LIMITED_INFORMATION
#else
#define MDB_PROCESS_QUERY_LIMITED_INFORMATION 0x1000
#endif
217
#define	Z	"I"
Howard Chu's avatar
Howard Chu committed
218
#else
Howard Chu's avatar
Howard Chu committed
219
220
221
#define THREAD_RET	void *
#define THREAD_CREATE(thr,start,arg)	pthread_create(&thr,NULL,start,arg)
#define THREAD_FINISH(thr)	pthread_join(thr,NULL)
222
#define	Z	"z"			/**< printf format modifier for size_t */
223

224
225
226
	/** For MDB_LOCK_FORMAT: True if readers take a pid lock in the lockfile */
#define MDB_PIDLOCK			1

227
#ifdef MDB_USE_POSIX_SEM
228
229

#define LOCK_MUTEX_R(env)	mdb_sem_wait((env)->me_rmutex)
Howard Chu's avatar
Howard Chu committed
230
#define UNLOCK_MUTEX_R(env)	sem_post((env)->me_rmutex)
231
#define LOCK_MUTEX_W(env)	mdb_sem_wait((env)->me_wmutex)
Howard Chu's avatar
Howard Chu committed
232
#define UNLOCK_MUTEX_W(env)	sem_post((env)->me_wmutex)
233
234
235
236
237
238
239
240
241

static int
mdb_sem_wait(sem_t *sem)
{
   int rc;
   while ((rc = sem_wait(sem)) && (rc = errno) == EINTR) ;
   return rc;
}

Howard Chu's avatar
Howard Chu committed
242
#else
Howard Chu's avatar
Howard Chu committed
243
244
	/** Lock the reader mutex.
	 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
245
#define LOCK_MUTEX_R(env)	pthread_mutex_lock(&(env)->me_txns->mti_mutex)
Howard Chu's avatar
Howard Chu committed
246
247
	/** Unlock the reader mutex.
	 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
248
#define UNLOCK_MUTEX_R(env)	pthread_mutex_unlock(&(env)->me_txns->mti_mutex)
Howard Chu's avatar
Howard Chu committed
249
250
251
252
253

	/** Lock the writer mutex.
	 *	Only a single write transaction is allowed at a time. Other writers
	 *	will block waiting for this mutex.
	 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
254
#define LOCK_MUTEX_W(env)	pthread_mutex_lock(&(env)->me_txns->mti_wmutex)
Howard Chu's avatar
Howard Chu committed
255
256
	/** Unlock the writer mutex.
	 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
257
#define UNLOCK_MUTEX_W(env)	pthread_mutex_unlock(&(env)->me_txns->mti_wmutex)
258
#endif	/* MDB_USE_POSIX_SEM */
Howard Chu's avatar
Howard Chu committed
259
260
261

	/** Get the error code for the last failed system function.
	 */
Howard Chu's avatar
Howard Chu committed
262
#define	ErrCode()	errno
Howard Chu's avatar
Howard Chu committed
263

264
265
266
267
268
269
	/** 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
270
271
272
273
	/**	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
274
#define INVALID_HANDLE_VALUE	(-1)
Howard Chu's avatar
Howard Chu committed
275
276
277
278
279

	/** 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
280
#define	GET_PAGESIZE(x)	((x) = sysconf(_SC_PAGE_SIZE))
Howard Chu's avatar
Howard Chu committed
281
#endif
Howard Chu's avatar
Howard Chu committed
282

283
#if defined(_WIN32) || defined(MDB_USE_POSIX_SEM)
Howard Chu's avatar
Howard Chu committed
284
#define MNAME_LEN	32
285
286
#else
#define MNAME_LEN	(sizeof(pthread_mutex_t))
Howard Chu's avatar
Howard Chu committed
287
288
#endif

289
/** @} */
Howard Chu's avatar
Howard Chu committed
290

291
#ifndef _WIN32
Howard Chu's avatar
Howard Chu committed
292
293
294
295
296
297
/**	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
298
299
300
301
302
303
 * 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
304
305
306
307
308
309
310
#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
311
312
313
314
315
316
317
318
319
320
321
322
#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
323
324
#endif

Howard Chu's avatar
Howard Chu committed
325
326
327
328
329
330
331
332
	/** 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.
	 */
333
typedef MDB_ID	pgno_t;
Hallvard Furuseth's avatar
Hallvard Furuseth committed
334

335
336
337
	/** A transaction ID.
	 *	See struct MDB_txn.mt_txnid for details.
	 */
338
typedef MDB_ID	txnid_t;
Hallvard Furuseth's avatar
Hallvard Furuseth committed
339

Howard Chu's avatar
Howard Chu committed
340
341
342
/** @defgroup debug	Debug Macros
 *	@{
 */
Howard Chu's avatar
Howard Chu committed
343
#ifndef MDB_DEBUG
344
	/**	Enable debug output.  Needs variable argument macros (a C99 feature).
Howard Chu's avatar
Howard Chu committed
345
346
347
	 *	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
348
#define MDB_DEBUG 0
349
#endif
Howard Chu's avatar
Howard Chu committed
350

351
#if MDB_DEBUG
352
static int mdb_debug;
353
static txnid_t mdb_debug_start;
354

355
356
357
358
359
	/**	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
360
	fprintf(stderr, "%s:%d " fmt "\n", mdb_func_, __LINE__, __VA_ARGS__)
Howard Chu's avatar
Howard Chu committed
361
#else
362
# define DPRINTF(args)	((void) 0)
Howard Chu's avatar
Howard Chu committed
363
#endif
Howard Chu's avatar
Howard Chu committed
364
365
366
	/**	Print a debug string.
	 *	The string is printed literally, with no format processing.
	 */
367
#define DPUTS(arg)	DPRINTF(("%s", arg))
368
369
370
	/** 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
371
/** @} */
Howard Chu's avatar
Howard Chu committed
372

373
374
	/**	@brief The maximum size of a database page.
	 *
Hallvard Furuseth's avatar
Hallvard Furuseth committed
375
	 *	This is 32k, since it must fit in #MDB_page.%mp_upper.
376
377
378
379
	 *
	 *	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
380
381
382
383
384
385
386
387
	 *
	 *	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.
	 */
388
#define MAX_PAGESIZE	 0x8000
Howard Chu's avatar
Howard Chu committed
389
390
391
392
393
394
395
396
397
398
399
400
401

	/** 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
402
#define MDB_MINKEYS	 2
Howard Chu's avatar
Howard Chu committed
403

Howard Chu's avatar
Howard Chu committed
404
	/**	A stamp that identifies a file as an LMDB file.
Howard Chu's avatar
Howard Chu committed
405
406
407
	 *	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
408
#define MDB_MAGIC	 0xBEEFC0DE
Howard Chu's avatar
Howard Chu committed
409

410
411
412
413
	/**	The version number for a database's datafile format. */
#define MDB_DATA_VERSION	 1
	/**	The version number for a database's lockfile format. */
#define MDB_LOCK_VERSION	 1
Howard Chu's avatar
Howard Chu committed
414

415
	/**	@brief The max size of a key we can write, or 0 for dynamic max.
416
	 *
417
418
419
	 *	Define this as 0 to compute the max from the page size.  511
	 *	is default for backwards compat: liblmdb <= 0.9.10 can break
	 *	when modifying a DB with keys/dupsort data bigger than its max.
420
	 *
421
422
423
	 *	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
424
	 */
425
426
#ifndef MDB_MAXKEYSIZE
#define MDB_MAXKEYSIZE	 511
427
428
429
430
431
432
433
#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)
434
#endif
Howard Chu's avatar
Howard Chu committed
435

436
437
438
439
440
441
	/**	@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
442
#if MDB_DEBUG
443
444
445
446
	/**	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
447
448
449
450
	/**	A key buffer.
	 *	@ingroup debug
	 *	This is used for printing a hex dump of a key's contents.
	 */
451
#define DKBUF	char kbuf[DKBUF_MAXKEYSIZE*2+1]
Howard Chu's avatar
Howard Chu committed
452
453
454
455
	/**	Display a key in hex.
	 *	@ingroup debug
	 *	Invoke a function to display a key in hex.
	 */
Howard Chu's avatar
Howard Chu committed
456
457
#define	DKEY(x)	mdb_dkey(x, kbuf)
#else
Howard Chu's avatar
Howard Chu committed
458
#define	DKBUF
Howard Chu's avatar
Howard Chu committed
459
#define DKEY(x)	0
Howard Chu's avatar
Howard Chu committed
460
#endif
Howard Chu's avatar
Howard Chu committed
461

Howard Chu's avatar
Howard Chu committed
462
463
464
	/** An invalid page number.
	 *	Mainly used to denote an empty tree.
	 */
465
#define P_INVALID	 (~(pgno_t)0)
Howard Chu's avatar
Howard Chu committed
466

467
	/** Test if the flags \b f are set in a flag word \b w. */
Howard Chu's avatar
Howard Chu committed
468
469
#define F_ISSET(w, f)	 (((w) & (f)) == (f))

470
471
472
	/** 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
473
474
475
476
	/**	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
477
478
typedef uint16_t	 indx_t;

Howard Chu's avatar
Howard Chu committed
479
480
481
482
	/**	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
483
484
#define DEFAULT_MAPSIZE	1048576

Howard Chu's avatar
Howard Chu committed
485
486
487
488
489
490
491
/**	@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
492
493
 *	If #MDB_NOTLS is set, the slot address is not saved in thread-specific data.
 *
Howard Chu's avatar
Howard Chu committed
494
495
 *	No reader table is used if the database is on a read-only filesystem, or
 *	if #MDB_NOLOCK is set.
496
 *
Howard Chu's avatar
Howard Chu committed
497
498
499
 *	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
500
501
 *	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
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
 *	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
536
#ifndef CACHELINE
Howard Chu's avatar
Howard Chu committed
537
#define CACHELINE	64
Howard Chu's avatar
Howard Chu committed
538
539
#endif

Howard Chu's avatar
Howard Chu committed
540
541
542
543
544
545
546
547
	/**	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
548
typedef struct MDB_rxbody {
549
	/**	Current Transaction ID when this transaction began, or (txnid_t)-1.
Howard Chu's avatar
Howard Chu committed
550
551
552
553
554
555
	 *	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.
	 */
556
	txnid_t		mrb_txnid;
Howard Chu's avatar
Howard Chu committed
557
	/** The process ID of the process owning this reader txn. */
Howard Chu's avatar
Howard Chu committed
558
	MDB_PID_T	mrb_pid;
Howard Chu's avatar
Howard Chu committed
559
	/** The thread ID of the thread owning this txn. */
Howard Chu's avatar
Howard Chu committed
560
	MDB_THR_T	mrb_tid;
Howard Chu's avatar
Howard Chu committed
561
562
} MDB_rxbody;

Howard Chu's avatar
Howard Chu committed
563
	/** The actual reader record, with cacheline padding. */
Howard Chu's avatar
Howard Chu committed
564
typedef struct MDB_reader {
Howard Chu's avatar
Howard Chu committed
565
566
	union {
		MDB_rxbody mrx;
Howard Chu's avatar
Howard Chu committed
567
		/** shorthand for mrb_txnid */
Howard Chu's avatar
Howard Chu committed
568
569
570
#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
571
		/** cache line alignment */
Howard Chu's avatar
Howard Chu committed
572
573
		char pad[(sizeof(MDB_rxbody)+CACHELINE-1) & ~(CACHELINE-1)];
	} mru;
Howard Chu's avatar
Howard Chu committed
574
575
} MDB_reader;

Howard Chu's avatar
Howard Chu committed
576
577
578
579
580
581
582
	/** 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
583
	 *	processes can grab them. This same approach is also used on
Howard Chu's avatar
Howard Chu committed
584
	 *	MacOSX/Darwin (using named semaphores) since MacOSX doesn't support
Howard Chu's avatar
Howard Chu committed
585
586
587
588
	 *	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
589
	 */
Howard Chu's avatar
Howard Chu committed
590
typedef struct MDB_txbody {
Howard Chu's avatar
Howard Chu committed
591
		/** Stamp identifying this as an LMDB file. It must be set
Howard Chu's avatar
Howard Chu committed
592
		 *	to #MDB_MAGIC. */
Howard Chu's avatar
Howard Chu committed
593
	uint32_t	mtb_magic;
594
595
		/** Format of this lock file. Must be set to #MDB_LOCK_FORMAT. */
	uint32_t	mtb_format;
596
#if defined(_WIN32) || defined(MDB_USE_POSIX_SEM)
Howard Chu's avatar
Howard Chu committed
597
	char	mtb_rmname[MNAME_LEN];
Howard Chu's avatar
Howard Chu committed
598
#else
Howard Chu's avatar
Howard Chu committed
599
600
601
		/** Mutex protecting access to this table.
		 *	This is the reader lock that #LOCK_MUTEX_R acquires.
		 */
Howard Chu's avatar
Howard Chu committed
602
	pthread_mutex_t	mtb_mutex;
Howard Chu's avatar
Howard Chu committed
603
#endif
Howard Chu's avatar
Howard Chu committed
604
605
606
607
		/**	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.
		 */
608
	txnid_t		mtb_txnid;
Howard Chu's avatar
Howard Chu committed
609
610
611
612
		/** 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.
		 */
613
	unsigned	mtb_numreaders;
Howard Chu's avatar
Howard Chu committed
614
615
} MDB_txbody;

Howard Chu's avatar
Howard Chu committed
616
	/** The actual reader table definition. */
Howard Chu's avatar
Howard Chu committed
617
typedef struct MDB_txninfo {
Howard Chu's avatar
Howard Chu committed
618
619
620
	union {
		MDB_txbody mtb;
#define mti_magic	mt1.mtb.mtb_magic
621
#define mti_format	mt1.mtb.mtb_format
Howard Chu's avatar
Howard Chu committed
622
#define mti_mutex	mt1.mtb.mtb_mutex
Howard Chu's avatar
Howard Chu committed
623
#define mti_rmname	mt1.mtb.mtb_rmname
Howard Chu's avatar
Howard Chu committed
624
625
626
627
628
#define mti_txnid	mt1.mtb.mtb_txnid
#define mti_numreaders	mt1.mtb.mtb_numreaders
		char pad[(sizeof(MDB_txbody)+CACHELINE-1) & ~(CACHELINE-1)];
	} mt1;
	union {
629
#if defined(_WIN32) || defined(MDB_USE_POSIX_SEM)
Howard Chu's avatar
Howard Chu committed
630
		char mt2_wmname[MNAME_LEN];
Howard Chu's avatar
Howard Chu committed
631
632
#define	mti_wmname	mt2.mt2_wmname
#else
Howard Chu's avatar
Howard Chu committed
633
634
		pthread_mutex_t	mt2_wmutex;
#define mti_wmutex	mt2.mt2_wmutex
Howard Chu's avatar
Howard Chu committed
635
#endif
636
		char pad[(MNAME_LEN+CACHELINE-1) & ~(CACHELINE-1)];
Howard Chu's avatar
Howard Chu committed
637
638
	} mt2;
	MDB_reader	mti_readers[1];
Howard Chu's avatar
Howard Chu committed
639
} MDB_txninfo;
640
641
642
643
644
645
646

	/** Lockfile format signature: version, features and field layout */
#define MDB_LOCK_FORMAT \
	((uint32_t) \
	 ((MDB_LOCK_VERSION) \
	  /* Flags which describe functionality */ \
	  + (((MDB_PIDLOCK) != 0) << 16)))
Howard Chu's avatar
Howard Chu committed
647
/** @} */
Howard Chu's avatar
Howard Chu committed
648

Howard Chu's avatar
Howard Chu committed
649
/** Common header for all page types.
Howard Chu's avatar
Howard Chu committed
650
 * Overflow records occupy a number of contiguous pages with no
Howard Chu's avatar
Howard Chu committed
651
652
 * headers on any page after the first.
 */
Howard Chu's avatar
Howard Chu committed
653
typedef struct MDB_page {
654
655
#define	mp_pgno	mp_p.p_pgno
#define	mp_next	mp_p.p_next
Howard Chu's avatar
Howard Chu committed
656
	union {
657
658
659
		pgno_t		p_pgno;	/**< page number */
		void *		p_next;	/**< for in-memory list of freed structs */
	} mp_p;
Howard Chu's avatar
Howard Chu committed
660
	uint16_t	mp_pad;
Howard Chu's avatar
Howard Chu committed
661
662
663
664
665
/**	@defgroup mdb_page	Page Flags
 *	@ingroup internal
 *	Flags for the page headers.
 *	@{
 */
Howard Chu's avatar
Howard Chu committed
666
667
668
669
#define	P_BRANCH	 0x01		/**< branch page */
#define	P_LEAF		 0x02		/**< leaf page */
#define	P_OVERFLOW	 0x04		/**< overflow page */
#define	P_META		 0x08		/**< meta page */
670
#define	P_DIRTY		 0x10		/**< dirty page, also set for #P_SUBP pages */
Howard Chu's avatar
Howard Chu committed
671
#define	P_LEAF2		 0x20		/**< for #MDB_DUPFIXED records */
Howard Chu's avatar
Howard Chu committed
672
#define	P_SUBP		 0x40		/**< for #MDB_DUPSORT sub-pages */
Howard Chu's avatar
Howard Chu committed
673
#define	P_LOOSE		 0x4000		/**< page was dirtied then freed, can be reused */
Howard Chu's avatar
Howard Chu committed
674
#define	P_KEEP		 0x8000		/**< leave this page alone during spill */
Howard Chu's avatar
Howard Chu committed
675
/** @} */
Howard Chu's avatar
Howard Chu committed
676
	uint16_t	mp_flags;		/**< @ref mdb_page */
677
678
679
#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
680
	union {
Howard Chu's avatar
Howard Chu committed
681
		struct {
682
683
684
685
686
			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
687
	indx_t		mp_ptrs[1];		/**< dynamic size */
Howard Chu's avatar
Howard Chu committed
688
689
} MDB_page;

Howard Chu's avatar
Howard Chu committed
690
	/** Size of the page header, excluding dynamic data at the end */
691
#define PAGEHDRSZ	 ((unsigned) offsetof(MDB_page, mp_ptrs))
Howard Chu's avatar
Howard Chu committed
692

Howard Chu's avatar
Howard Chu committed
693
694
695
696
	/** Address of first usable data byte in a page, after the header */
#define METADATA(p)	 ((void *)((char *)(p) + PAGEHDRSZ))

	/** Number of nodes on a page */
Howard Chu's avatar
Howard Chu committed
697
#define NUMKEYS(p)	 (((p)->mp_lower - PAGEHDRSZ) >> 1)
Howard Chu's avatar
Howard Chu committed
698
699

	/** The amount of space remaining in the page */
Howard Chu's avatar
Howard Chu committed
700
#define SIZELEFT(p)	 (indx_t)((p)->mp_upper - (p)->mp_lower)
Howard Chu's avatar
Howard Chu committed
701
702

	/** The percentage of space used in the page, in tenths of a percent. */
Howard Chu's avatar
Howard Chu committed
703
704
#define PAGEFILL(env, p) (1000L * ((env)->me_psize - PAGEHDRSZ - SIZELEFT(p)) / \
				((env)->me_psize - PAGEHDRSZ))
Howard Chu's avatar
Howard Chu committed
705
706
707
708
709
710
	/** 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
711
#define IS_LEAF(p)	 F_ISSET((p)->mp_flags, P_LEAF)
Howard Chu's avatar
Howard Chu committed
712
	/** Test if a page is a LEAF2 page */
Howard Chu's avatar
Howard Chu committed
713
#define IS_LEAF2(p)	 F_ISSET((p)->mp_flags, P_LEAF2)
Howard Chu's avatar
Howard Chu committed
714
	/** Test if a page is a branch page */
Howard Chu's avatar
Howard Chu committed
715
#define IS_BRANCH(p)	 F_ISSET((p)->mp_flags, P_BRANCH)
Howard Chu's avatar
Howard Chu committed
716
	/** Test if a page is an overflow page */
Howard Chu's avatar
Howard Chu committed
717
#define IS_OVERFLOW(p)	 F_ISSET((p)->mp_flags, P_OVERFLOW)
Howard Chu's avatar
Howard Chu committed
718
719
	/** 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
720

Howard Chu's avatar
Howard Chu committed
721
	/** The number of overflow pages needed to store the given size. */
722
#define OVPAGES(size, psize)	((PAGEHDRSZ-1 + (size)) / (psize) + 1)
Howard Chu's avatar
Howard Chu committed
723

724
725
726
	/** Link in #MDB_txn.%mt_loose_pages list */
#define NEXT_LOOSE_PAGE(p)		(*(MDB_page **)METADATA(p))

Howard Chu's avatar
Howard Chu committed
727
	/** Header for a single key/data pair within a page.
728
729
	 * 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
730
731
732
733
	 */
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
734
	 * is also used for pgno. (Branch nodes have no flags).
Howard Chu's avatar
Howard Chu committed
735
	 * They are in host byte order in case that lets some
736
	 * accesses be optimized into a 32-bit word access.
Howard Chu's avatar
Howard Chu committed
737
	 */
738
739
740
741
742
#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
743
744
745
746
747
/** @defgroup mdb_node Node Flags
 *	@ingroup internal
 *	Flags for node headers.
 *	@{
 */
Howard Chu's avatar
Howard Chu committed
748
749
750
#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
751
752

/** valid flags for #mdb_node_add() */
753
#define	NODE_ADD_FLAGS	(F_DUPDATA|F_SUBDATA|MDB_RESERVE|MDB_APPEND)
Howard Chu's avatar
Howard Chu committed
754

Howard Chu's avatar
Howard Chu committed
755
756
/** @} */
	unsigned short	mn_flags;		/**< @ref mdb_node */
Howard Chu's avatar
Howard Chu committed
757
758
759
760
761
762
763
	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)

764
765
766
	/** 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
767
	/** Size of a node in a branch page with a given key.
Howard Chu's avatar
Howard Chu committed
768
769
770
771
	 *	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
772
	/** Size of a node in a leaf page with a given key and data.
Howard Chu's avatar
Howard Chu committed
773
774
775
776
	 *	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
777
	/** Address of node \b i in page \b p */
Howard Chu's avatar
Howard Chu committed
778
779
780
781
782
783
784
785
786
#define NODEPTR(p, i)	 ((MDB_node *)((char *)(p) + (p)->mp_ptrs[i]))

	/** 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 */
787
788
789
#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
790
791
792
	/** Set the page number in a branch node */
#define SETPGNO(node,pgno)	do { \
	(node)->mn_lo = (pgno) & 0xffff; (node)->mn_hi = (pgno) >> 16; \
793
	if (PGNO_TOPWORD) (node)->mn_flags = (pgno) >> PGNO_TOPWORD; } while(0)
Howard Chu's avatar
Howard Chu committed
794
795
796
797
798
799
800
801
802

	/** 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
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
	/** 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
827
828
829
830
831
832
	/** 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
833
834
835
836
837
838
	/** 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
839
840

	/** Information about a single database in the environment. */
Howard Chu's avatar
Howard Chu committed
841
typedef struct MDB_db {
Howard Chu's avatar
Howard Chu committed
842
	uint32_t	md_pad;		/**< also ksize for LEAF2 pages */
843
	uint16_t	md_flags;	/**< @ref mdb_dbi_open */
Howard Chu's avatar
Howard Chu committed
844
	uint16_t	md_depth;	/**< depth of this tree */
845
846
847
848
	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
849
	pgno_t		md_root;		/**< the root page of this tree */
Howard Chu's avatar
Howard Chu committed
850
851
} MDB_db;

852
	/** mdb_dbi_open flags */
853
854
#define MDB_VALID	0x8000		/**< DB handle is valid, for me_dbflags */
#define PERSISTENT_FLAGS	(0xffff & ~(MDB_VALID))
855
856
857
#define VALID_FLAGS	(MDB_REVERSEKEY|MDB_DUPSORT|MDB_INTEGERKEY|MDB_DUPFIXED|\
	MDB_INTEGERDUP|MDB_REVERSEDUP|MDB_CREATE)

Howard Chu's avatar
Howard Chu committed
858
	/** Handle for the DB used to track free pages. */
Howard Chu's avatar
Howard Chu committed
859
#define	FREE_DBI	0
Howard Chu's avatar
Howard Chu committed
860
	/** Handle for the default DB. */
Howard Chu's avatar
Howard Chu committed
861
862
#define	MAIN_DBI	1

863
864
865
866
	/** 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
867
typedef struct MDB_meta {
Howard Chu's avatar
Howard Chu committed
868
		/** Stamp identifying this as an LMDB file. It must be set
Howard Chu's avatar
Howard Chu committed
869
		 *	to #MDB_MAGIC. */
Howard Chu's avatar
Howard Chu committed
870
	uint32_t	mm_magic;
871
		/** Version number of this lock file. Must be set to #MDB_DATA_VERSION. */
Howard Chu's avatar
Howard Chu committed
872
	uint32_t	mm_version;
Howard Chu's avatar
Howard Chu committed
873
874
875
876
	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
877
#define	mm_psize	mm_dbs[0].md_pad
Howard Chu's avatar
Howard Chu committed
878
	/** Any persistent environment flags. @ref mdb_env */
Howard Chu's avatar
Howard Chu committed
879
#define	mm_flags	mm_dbs[0].md_flags
Howard Chu's avatar
Howard Chu committed
880
	pgno_t		mm_last_pg;			/**< last used page in file */
881
	txnid_t		mm_txnid;			/**< txnid that committed this page */
Howard Chu's avatar
Howard Chu committed
882
883
} MDB_meta;

884
	/** Buffer for a stack-allocated meta page.
885
886
887
888
	 *	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.
	 */
889
typedef union MDB_metabuf {
890
891
892
893
894
	MDB_page	mb_page;
	struct {
		char		mm_pad[PAGEHDRSZ];
		MDB_meta	mm_meta;
	} mb_metabuf;
895
} MDB_metabuf;
896

Howard Chu's avatar
Howard Chu committed
897
898
899
900
901
902
903
904
905
	/** 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 */
906
	void		*md_relctx;		/**< user-provided context for md_rel */
Howard Chu's avatar
Howard Chu committed
907
} MDB_dbx;
Howard Chu's avatar
Howard Chu committed
908

Howard Chu's avatar
Howard Chu committed
909
910
911
912
	/** A database transaction.
	 *	Every operation requires a transaction handle.
	 */
struct MDB_txn {
913
914
	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
915
916
917
918
919
	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.
	 */
920
	txnid_t		mt_txnid;
Howard Chu's avatar
Howard Chu committed
921
922
923
	MDB_env		*mt_env;		/**< the DB environment */
	/** The list of pages that became unused during this transaction.
	 */
924
	MDB_IDL		mt_free_pgs;
Howard Chu's avatar
Howard Chu committed
925
	/** The list of loose pages that became unused and may be reused
926
	 *	in this transaction, linked through #NEXT_LOOSE_PAGE(page).
Howard Chu's avatar
Howard Chu committed
927
928
	 */
	MDB_page	*mt_loose_pgs;
Hallvard Furuseth's avatar
Hallvard Furuseth committed
929
	/** The sorted list of dirty pages we temporarily wrote to disk
930
931
	 *	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
932
933
	 */
	MDB_IDL		mt_spill_pgs;
Howard Chu's avatar
Howard Chu committed
934
	union {
Hallvard Furuseth's avatar
Hallvard Furuseth committed
935
936
937
938
		/** 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
939
940
941
942
943
	} 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;
Howard Chu's avatar
Howard Chu committed
944
945
946
947
/** @defgroup mt_dbflag	Transaction DB Flags
 *	@ingroup internal
 * @{
 */
948
#define DB_DIRTY	0x01		/**< DB was modified or is DUPSORT data */
949
950
#define DB_STALE	0x02		/**< Named-DB record is older than txnID */
#define DB_NEW		0x04		/**< Named-DB handle opened in this txn */
951
#define DB_VALID	0x08		/**< DB handle is valid, see also #MDB_VALID */
Howard Chu's avatar
Howard Chu committed
952
/** @} */
953
	/** In write txns, array of cursors for each DB */
Howard Chu's avatar
Howard Chu committed
954
	MDB_cursor	**mt_cursors;
Howard Chu's avatar
Howard Chu committed
955
956
	/** Array of flags for each DB */
	unsigned char	*mt_dbflags;
Howard Chu's avatar
Howard Chu committed
957
958
959
	/**	Number of DB records in use. This number only ever increments;
	 *	we don't decrement it when individual DB handles are closed.
	 */
960
	MDB_dbi		mt_numdbs;
Howard Chu's avatar
Howard Chu committed
961

Howard Chu's avatar
Howard Chu committed
962
963
964
965
/** @defgroup mdb_txn	Transaction Flags
 *	@ingroup internal
 *	@{
 */
Howard Chu's avatar
Howard Chu committed
966
#define MDB_TXN_RDONLY		0x01		/**< read-only transaction */
967
#define MDB_TXN_ERROR		0x02		/**< txn is unusable after an error */
968
#define MDB_TXN_DIRTY		0x04		/**< must write, even if dirty list is empty */
Howard Chu's avatar
Howard Chu committed
969
#define MDB_TXN_SPILLS		0x08		/**< txn or a parent has spilled pages */
Howard Chu's avatar
Howard Chu committed
970
971
/** @} */
	unsigned int	mt_flags;		/**< @ref mdb_txn */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
972
	/** #dirty_list room: Array size - \#dirty pages visible to this txn.
973
974
975
976
	 *	Includes ancestor txns' dirty pages not hidden by other txns'
	 *	dirty/spilled pages. Thus commit(nested txn) has room to merge
	 *	dirty_list into mt_parent after freeing hidden mt_parent pages.
	 */
977
	unsigned int	mt_dirty_room;
Howard Chu's avatar
Howard Chu committed
978
};
Howard Chu's avatar
Howard Chu committed
979

Howard Chu's avatar
Howard Chu committed
980
/** Enough space for 2^32 nodes with minimum of 2 keys per node. I.e., plenty.
981
982
983
 * At 4 keys per node, enough for 2^64 nodes, so there's probably no need to
 * raise this on a 64 bit machine.
 */
Howard Chu's avatar
Howard Chu committed
984
#define CURSOR_STACK		 32
Howard Chu's avatar
Howard Chu committed
985

Howard Chu's avatar
Howard Chu committed
986
struct MDB_xcursor;
987

988
989
990
991
992
993
994
995
	/** Cursors are used for all DB operations.
	 *	A cursor holds a path of (page pointer, key index) from the DB
	 *	root to a position in the DB, plus other state. #MDB_DUPSORT
	 *	cursors include an xcursor to the current data item. Write txns
	 *	track their cursors and keep them up to date when data moves.
	 *	Exception: An xcursor's pointer to a #P_SUBP page can be stale.
	 *	(A node with #F_DUPDATA but no #F_SUBDATA contains a subpage).
	 */
Howard Chu's avatar
Howard Chu committed
996
struct MDB_cursor {
Howard Chu's avatar
Howard Chu committed
997
998
	/** Next cursor on this DB in this txn */
	MDB_cursor	*mc_next;
999
1000
	/** Backup of the original cursor if this cursor is a shadow */
	MDB_cursor	*mc_backup;
Howard Chu's avatar
Howard Chu committed
1001
	/** Context used for databases with #MDB_DUPSORT, otherwise NULL */
Howard Chu's avatar
Howard Chu committed
1002
	struct MDB_xcursor	*mc_xcursor;
Howard Chu's avatar
Howard Chu committed
1003
	/** The transaction that owns this cursor */
Howard Chu's avatar
Howard Chu committed
1004
	MDB_txn		*mc_txn;
Howard Chu's avatar
Howard Chu committed
1005
	/** The database handle this cursor operates on */
Howard Chu's avatar
Howard Chu committed
1006
	MDB_dbi		mc_dbi;
1007
1008
1009
1010
	/** The database record for this cursor */
	MDB_db		*mc_db;
	/** The database auxiliary record for this cursor */
	MDB_dbx		*mc_dbx;
Howard Chu's avatar
Howard Chu committed
1011
1012
	/** The @ref mt_dbflag for this database */
	unsigned char	*mc_dbflag;
Howard Chu's avatar
Howard Chu committed
1013
	unsigned short 	mc_snum;	/**< number of pushed pages */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
1014
	unsigned short	mc_top;		/**< index of top page, normally mc_snum-1 */
Howard Chu's avatar
Howard Chu committed
1015
1016
1017
1018
1019
/** @defgroup mdb_cursor	Cursor Flags
 *	@ingroup internal
 *	Cursor state flags.
 *	@{
 */
Howard Chu's avatar
Howard Chu committed
1020
1021
#define C_INITIALIZED	0x01	/**< cursor has been initialized and is valid */
#define C_EOF	0x02			/**< No more data */
Howard Chu's avatar
Howard Chu committed
1022
#define C_SUB	0x04			/**< Cursor is a sub-cursor */
1023
#define C_DEL	0x08			/**< last op was a cursor_del */
Howard Chu's avatar
Howard Chu committed
1024
#define C_SPLITTING	0x20		/**< Cursor is in page_split */
1025
#define C_UNTRACK	0x40		/**< Un-track cursor when closing */
Howard Chu's avatar
Howard Chu committed
1026
1027
/** @} */
	unsigned int	mc_flags;	/**< @ref mdb_cursor */
Howard Chu's avatar
Howard Chu committed
1028
1029
	MDB_page	*mc_pg[CURSOR_STACK];	/**< stack of pushed pages */
	indx_t		mc_ki[CURSOR_STACK];	/**< stack of page indices */
Howard Chu's avatar
Howard Chu committed
1030
1031
};

Howard Chu's avatar
Howard Chu committed
1032
1033
1034
1035
	/** Context for sorted-dup records.
	 *	We could have gone to a fully recursive design, with arbitrarily
	 *	deep nesting of sub-databases. But for now we only handle these
	 *	levels - main DB, optional sub-DB, sorted-duplicate DB.
1036
	 */
Howard Chu's avatar
Howard Chu committed
1037
typedef struct MDB_xcursor {
Howard Chu's avatar
Howard Chu committed
1038
	/** A sub-cursor for traversing the Dup DB */
Howard Chu's avatar
Howard Chu committed
1039
	MDB_cursor mx_cursor;
1040
1041
1042
1043
	/** The database record for this Dup DB */
	MDB_db	mx_db;
	/**	The auxiliary DB record for this Dup DB */
	MDB_dbx	mx_dbx;
Howard Chu's avatar
Howard Chu committed
1044
1045
	/** The @ref mt_dbflag for this Dup DB */
	unsigned char mx_dbflag;
Howard Chu's avatar
Howard Chu committed
1046
1047
} MDB_xcursor;

1048
1049
	/** State of FreeDB old pages, stored in the MDB_env */
typedef struct MDB_pgstate {
1050
1051
	pgno_t		*mf_pghead;	/**< Reclaimed freeDB pages, or NULL before use */
	txnid_t		mf_pglast;	/**< ID of last used record, or 0 if !mf_pghead */
1052
1053
} MDB_pgstate;

Howard Chu's avatar
Howard Chu committed
1054
	/** The database environment. */
Howard Chu's avatar
Howard Chu committed
1055
struct MDB_env {
Howard Chu's avatar
Howard Chu committed
1056
1057
1058
	HANDLE		me_fd;		/**< The main data file */
	HANDLE		me_lfd;		/**< The lock file */
	HANDLE		me_mfd;			/**< just for writing the meta pages */
Howard Chu's avatar
Howard Chu committed
1059
	/** Failed to update the meta page. Probably an I/O error. */
Howard Chu's avatar
Howard Chu committed
1060
#define	MDB_FATAL_ERROR	0x80000000U
Hallvard Furuseth's avatar
Hallvard Furuseth committed
1061
1062
	/** Some fields are initialized. */
#define	MDB_ENV_ACTIVE	0x20000000U
1063
1064
	/** me_txkey is set */
#define	MDB_ENV_TXKEY	0x10000000U
Howard Chu's avatar
Howard Chu committed
1065
	uint32_t 	me_flags;		/**< @ref mdb_env */
1066
1067
	unsigned int	me_psize;	/**< DB page size, inited from me_os_psize */
	unsigned int	me_os_psize;	/**< OS page size, from #GET_PAGESIZE */
Howard Chu's avatar
Howard Chu committed
1068
	unsigned int	me_maxreaders;	/**< size of the reader table */
1069
	unsigned int	me_numreaders;	/**< max numreaders set by this env */
1070
1071
	MDB_dbi		me_numdbs;		/**< number of DBs opened */
	MDB_dbi		me_maxdbs;		/**< size of the DB table */
Howard Chu's avatar
Howard Chu committed
1072
	MDB_PID_T	me_pid;		/**< process ID of this env */
Howard Chu's avatar
Howard Chu committed
1073
1074
	char		*me_path;		/**< path to the DB files */
	char		*me_map;		/**< the memory map of the data file */
1075
	MDB_txninfo	*me_txns;		/**< the memory map of the lock file or NULL */
Howard Chu's avatar
Howard Chu committed
1076
	MDB_meta	*me_metas[2];	/**< pointers to the two meta pages */
1077
	void		*me_pbuf;		/**< scratch area for DUPSORT put() */
Howard Chu's avatar
Howard Chu committed
1078
1079
1080
1081
1082
	MDB_txn		*me_txn;		/**< current write transaction */
	size_t		me_mapsize;		/**< size of the data memory map */
	off_t		me_size;		/**< current file size */
	pgno_t		me_maxpg;		/**< me_mapsize / me_psize */
	MDB_dbx		*me_dbxs;		/**< array of static DB info */