mdb.c 216 KB
Newer Older
1
2
3
4
5
6
/** @file mdb.c
 *	@brief memory-mapped database library
 *
 *	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 2011-2013 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
39
40
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/param.h>
Howard Chu's avatar
Howard Chu committed
41
42
43
#ifdef _WIN32
#include <windows.h>
#else
Howard Chu's avatar
Howard Chu committed
44
45
46
47
48
#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
49
#include <fcntl.h>
Howard Chu's avatar
Howard Chu committed
50
#endif
Howard Chu's avatar
Howard Chu committed
51
52
53

#include <assert.h>
#include <errno.h>
54
#include <limits.h>
Howard Chu's avatar
Howard Chu committed
55
#include <stddef.h>
56
#include <inttypes.h>
Howard Chu's avatar
Howard Chu committed
57
58
59
60
61
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
62

63
#if !(defined(BYTE_ORDER) || defined(__BYTE_ORDER))
64
#include <netinet/in.h>
65
66
67
#include <resolv.h>	/* defines BYTE_ORDER on HPUX and Solaris */
#endif

68
#if defined(__APPLE__) || defined (BSD)
69
70
71
72
# define MDB_USE_POSIX_SEM	1
# define MDB_FDATASYNC		fsync
#elif defined(ANDROID)
# define MDB_FDATASYNC		fsync
73
74
#endif

75
76
#ifndef _WIN32
#include <pthread.h>
77
#ifdef MDB_USE_POSIX_SEM
Howard Chu's avatar
Howard Chu committed
78
79
80
81
#include <semaphore.h>
#endif
#endif

82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
#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
97
#ifndef BYTE_ORDER
Howard Chu's avatar
Howard Chu committed
98
99
100
101
102
103
104
105
106
107
108
109
# 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
110
#endif
Howard Chu's avatar
Howard Chu committed
111

Howard Chu's avatar
Howard Chu committed
112
113
114
115
116
#ifndef LITTLE_ENDIAN
#define LITTLE_ENDIAN	__LITTLE_ENDIAN
#endif
#ifndef BIG_ENDIAN
#define BIG_ENDIAN	__BIG_ENDIAN
117
118
#endif

Howard Chu's avatar
Howard Chu committed
119
#if defined(__i386) || defined(__x86_64) || defined(_M_IX86)
Howard Chu's avatar
Howard Chu committed
120
121
122
#define MISALIGNED_OK	1
#endif

Howard Chu's avatar
Howard Chu committed
123
#include "lmdb.h"
124
125
#include "midl.h"

Howard Chu's avatar
Howard Chu committed
126
127
#if (BYTE_ORDER == LITTLE_ENDIAN) == (BYTE_ORDER == BIG_ENDIAN)
# error "Unknown or unsupported endianness (BYTE_ORDER)"
128
129
130
131
#elif (-6 & 5) || CHAR_BIT != 8 || UINT_MAX < 0xffffffff || ULONG_MAX % 0xFFFF
# error "Two's complement, reasonably sized integer types, please"
#endif

132
133
134
135
/** @defgroup internal	MDB Internals
 *	@{
 */
/** @defgroup compat	Windows Compatibility Macros
Howard Chu's avatar
Howard Chu committed
136
137
138
139
 *	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.
140
141
 *	@{
 */
Howard Chu's avatar
Howard Chu committed
142
143
144
145
146
#ifdef _WIN32
#define pthread_t	DWORD
#define pthread_mutex_t	HANDLE
#define pthread_key_t	DWORD
#define pthread_self()	GetCurrentThreadId()
147
148
#define pthread_key_create(x,y)	\
	((*(x) = TlsAlloc()) == TLS_OUT_OF_INDEXES ? ErrCode() : 0)
Howard Chu's avatar
Howard Chu committed
149
150
#define pthread_key_delete(x)	TlsFree(x)
#define pthread_getspecific(x)	TlsGetValue(x)
151
#define pthread_setspecific(x,y)	(TlsSetValue(x,y) ? 0 : ErrCode())
Howard Chu's avatar
Howard Chu committed
152
153
#define pthread_mutex_unlock(x)	ReleaseMutex(x)
#define pthread_mutex_lock(x)	WaitForSingleObject(x, INFINITE)
Hallvard Furuseth's avatar
Hallvard Furuseth committed
154
155
156
157
#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
158
#define getpid()	GetCurrentProcessId()
159
#define	MDB_FDATASYNC(fd)	(!FlushFileBuffers(fd))
160
#define	MDB_MSYNC(addr,len,flags)	(!FlushViewOfFile(addr,len))
Howard Chu's avatar
Howard Chu committed
161
#define	ErrCode()	GetLastError()
Hallvard Furuseth's avatar
Hallvard Furuseth committed
162
#define GET_PAGESIZE(x) {SYSTEM_INFO si; GetSystemInfo(&si); (x) = si.dwPageSize;}
163
#define	close(fd)	(CloseHandle(fd) ? 0 : -1)
Howard Chu's avatar
Howard Chu committed
164
#define	munmap(ptr,len)	UnmapViewOfFile(ptr)
Howard Chu's avatar
Howard Chu committed
165
#else
166

167
#ifdef MDB_USE_POSIX_SEM
168
169

#define LOCK_MUTEX_R(env)	mdb_sem_wait((env)->me_rmutex)
Howard Chu's avatar
Howard Chu committed
170
#define UNLOCK_MUTEX_R(env)	sem_post((env)->me_rmutex)
171
#define LOCK_MUTEX_W(env)	mdb_sem_wait((env)->me_wmutex)
Howard Chu's avatar
Howard Chu committed
172
#define UNLOCK_MUTEX_W(env)	sem_post((env)->me_wmutex)
173
174
175
176
177
178
179
180
181

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
182
#else
Howard Chu's avatar
Howard Chu committed
183
184
	/** Lock the reader mutex.
	 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
185
#define LOCK_MUTEX_R(env)	pthread_mutex_lock(&(env)->me_txns->mti_mutex)
Howard Chu's avatar
Howard Chu committed
186
187
	/** Unlock the reader mutex.
	 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
188
#define UNLOCK_MUTEX_R(env)	pthread_mutex_unlock(&(env)->me_txns->mti_mutex)
Howard Chu's avatar
Howard Chu committed
189
190
191
192
193

	/** 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
194
#define LOCK_MUTEX_W(env)	pthread_mutex_lock(&(env)->me_txns->mti_wmutex)
Howard Chu's avatar
Howard Chu committed
195
196
	/** Unlock the writer mutex.
	 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
197
#define UNLOCK_MUTEX_W(env)	pthread_mutex_unlock(&(env)->me_txns->mti_wmutex)
198
#endif	/* MDB_USE_POSIX_SEM */
Howard Chu's avatar
Howard Chu committed
199
200
201

	/** Get the error code for the last failed system function.
	 */
Howard Chu's avatar
Howard Chu committed
202
#define	ErrCode()	errno
Howard Chu's avatar
Howard Chu committed
203

204
205
206
207
208
209
	/** 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
210
211
212
213
	/**	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
214
#define INVALID_HANDLE_VALUE	(-1)
Howard Chu's avatar
Howard Chu committed
215
216
217
218
219

	/** 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
220
#define	GET_PAGESIZE(x)	((x) = sysconf(_SC_PAGE_SIZE))
Howard Chu's avatar
Howard Chu committed
221
#endif
Howard Chu's avatar
Howard Chu committed
222

223
#if defined(_WIN32) || defined(MDB_USE_POSIX_SEM)
Howard Chu's avatar
Howard Chu committed
224
#define MNAME_LEN	32
225
226
#else
#define MNAME_LEN	(sizeof(pthread_mutex_t))
Howard Chu's avatar
Howard Chu committed
227
228
#endif

229
/** @} */
Howard Chu's avatar
Howard Chu committed
230

231
#ifndef _WIN32
Howard Chu's avatar
Howard Chu committed
232
233
234
235
236
237
/**	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
238
239
240
241
242
243
 * 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
244
245
246
247
248
249
250
#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
251
252
253
254
255
256
257
258
259
260
261
262
#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
263
264
#endif

Howard Chu's avatar
Howard Chu committed
265
266
267
268
269
270
271
272
	/** 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.
	 */
273
typedef MDB_ID	pgno_t;
Hallvard Furuseth's avatar
Hallvard Furuseth committed
274

275
276
277
	/** A transaction ID.
	 *	See struct MDB_txn.mt_txnid for details.
	 */
278
typedef MDB_ID	txnid_t;
Hallvard Furuseth's avatar
Hallvard Furuseth committed
279

Howard Chu's avatar
Howard Chu committed
280
281
282
/** @defgroup debug	Debug Macros
 *	@{
 */
Howard Chu's avatar
Howard Chu committed
283
#ifndef MDB_DEBUG
Howard Chu's avatar
Howard Chu committed
284
285
286
287
	/**	Enable debug output.
	 *	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
288
#define MDB_DEBUG 0
289
#endif
Howard Chu's avatar
Howard Chu committed
290

291
#if !(__STDC_VERSION__ >= 199901L || defined(__GNUC__))
292
293
# undef  MDB_DEBUG
# define MDB_DEBUG	0
294
# define DPRINTF	(void)	/* Vararg macros may be unsupported */
Howard Chu's avatar
Howard Chu committed
295
#elif MDB_DEBUG
296
static int mdb_debug;
297
static txnid_t mdb_debug_start;
298

Howard Chu's avatar
Howard Chu committed
299
300
	/**	Print a debug message with printf formatting. */
# define DPRINTF(fmt, ...)	/**< Requires 2 or more args */ \
301
302
	((void) ((mdb_debug) && \
	 fprintf(stderr, "%s:%d " fmt "\n", __func__, __LINE__, __VA_ARGS__)))
Howard Chu's avatar
Howard Chu committed
303
#else
304
# define DPRINTF(fmt, ...)	((void) 0)
305
# define MDB_DEBUG_SKIP
Howard Chu's avatar
Howard Chu committed
306
#endif
Howard Chu's avatar
Howard Chu committed
307
308
309
	/**	Print a debug string.
	 *	The string is printed literally, with no format processing.
	 */
310
#define DPUTS(arg)	DPRINTF("%s", arg)
Howard Chu's avatar
Howard Chu committed
311
/** @} */
Howard Chu's avatar
Howard Chu committed
312

Howard Chu's avatar
Howard Chu committed
313
314
315
	/** A default memory page size.
	 *	The actual size is platform-dependent, but we use this for
	 *	boot-strapping. We probably should not be using this any more.
Hallvard Furuseth's avatar
Hallvard Furuseth committed
316
	 *	The #GET_PAGESIZE() macro is used to get the actual size.
Howard Chu's avatar
Howard Chu committed
317
318
319
320
321
322
323
324
	 *
	 *	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.
	 */
Howard Chu's avatar
Howard Chu committed
325
#define MDB_PAGESIZE	 4096
Howard Chu's avatar
Howard Chu committed
326
327
328
329
330
331
332
333
334
335
336
337
338

	/** 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
339
#define MDB_MINKEYS	 2
Howard Chu's avatar
Howard Chu committed
340
341
342
343
344

	/**	A stamp that identifies a file as an MDB file.
	 *	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
345
#define MDB_MAGIC	 0xBEEFC0DE
Howard Chu's avatar
Howard Chu committed
346
347

	/**	The version number for a database's file format. */
Howard Chu's avatar
Howard Chu committed
348
#define MDB_VERSION	 1
Howard Chu's avatar
Howard Chu committed
349

350
	/**	@brief The maximum size of a key in the database.
351
352
353
	 *
	 *	The library rejects bigger keys, and cannot deal with records
	 *	with bigger keys stored by a library with bigger max keysize.
354
	 *
355
356
357
	 *	We require that keys all fit onto a regular page. This limit
	 *	could be raised a bit further if needed; to something just
	 *	under #MDB_PAGESIZE / #MDB_MINKEYS.
358
359
360
	 *
	 *	Note that data items in an #MDB_DUPSORT database are actually keys
	 *	of a subDB, so they're also limited to this size.
Howard Chu's avatar
Howard Chu committed
361
	 */
362
363
364
#ifndef MDB_MAXKEYSIZE
#define MDB_MAXKEYSIZE	 511
#endif
Howard Chu's avatar
Howard Chu committed
365

366
367
368
369
370
371
	/**	@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
372
#if MDB_DEBUG
Howard Chu's avatar
Howard Chu committed
373
374
375
376
	/**	A key buffer.
	 *	@ingroup debug
	 *	This is used for printing a hex dump of a key's contents.
	 */
377
#define DKBUF	char kbuf[(MDB_MAXKEYSIZE*2+1)]
Howard Chu's avatar
Howard Chu committed
378
379
380
381
	/**	Display a key in hex.
	 *	@ingroup debug
	 *	Invoke a function to display a key in hex.
	 */
Howard Chu's avatar
Howard Chu committed
382
383
#define	DKEY(x)	mdb_dkey(x, kbuf)
#else
384
#define	DKBUF	typedef int dummy_kbuf	/* so we can put ';' after */
Howard Chu's avatar
Howard Chu committed
385
#define DKEY(x)	0
Howard Chu's avatar
Howard Chu committed
386
#endif
Howard Chu's avatar
Howard Chu committed
387

Howard Chu's avatar
Howard Chu committed
388
389
390
	/** An invalid page number.
	 *	Mainly used to denote an empty tree.
	 */
391
#define P_INVALID	 (~(pgno_t)0)
Howard Chu's avatar
Howard Chu committed
392

393
	/** Test if the flags \b f are set in a flag word \b w. */
Howard Chu's avatar
Howard Chu committed
394
395
#define F_ISSET(w, f)	 (((w) & (f)) == (f))

Howard Chu's avatar
Howard Chu committed
396
397
398
399
	/**	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
400
401
typedef uint16_t	 indx_t;

Howard Chu's avatar
Howard Chu committed
402
403
404
405
	/**	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
406
407
#define DEFAULT_MAPSIZE	1048576

Howard Chu's avatar
Howard Chu committed
408
409
410
411
412
413
414
/**	@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
415
416
 *	If #MDB_NOTLS is set, the slot address is not saved in thread-specific data.
 *
417
418
 *	No reader table is used if the database is on a read-only filesystem.
 *
Howard Chu's avatar
Howard Chu committed
419
420
421
 *	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
422
423
 *	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
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
 *	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
458
#ifndef CACHELINE
Howard Chu's avatar
Howard Chu committed
459
#define CACHELINE	64
Howard Chu's avatar
Howard Chu committed
460
461
#endif

Howard Chu's avatar
Howard Chu committed
462
463
464
465
466
467
468
469
	/**	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
470
typedef struct MDB_rxbody {
471
	/**	Current Transaction ID when this transaction began, or (txnid_t)-1.
Howard Chu's avatar
Howard Chu committed
472
473
474
475
476
477
	 *	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.
	 */
478
	txnid_t		mrb_txnid;
Howard Chu's avatar
Howard Chu committed
479
	/** The process ID of the process owning this reader txn. */
Howard Chu's avatar
Howard Chu committed
480
	pid_t		mrb_pid;
Howard Chu's avatar
Howard Chu committed
481
	/** The thread ID of the thread owning this txn. */
Howard Chu's avatar
Howard Chu committed
482
483
484
	pthread_t	mrb_tid;
} MDB_rxbody;

Howard Chu's avatar
Howard Chu committed
485
	/** The actual reader record, with cacheline padding. */
Howard Chu's avatar
Howard Chu committed
486
typedef struct MDB_reader {
Howard Chu's avatar
Howard Chu committed
487
488
	union {
		MDB_rxbody mrx;
Howard Chu's avatar
Howard Chu committed
489
		/** shorthand for mrb_txnid */
Howard Chu's avatar
Howard Chu committed
490
491
492
#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
493
		/** cache line alignment */
Howard Chu's avatar
Howard Chu committed
494
495
		char pad[(sizeof(MDB_rxbody)+CACHELINE-1) & ~(CACHELINE-1)];
	} mru;
Howard Chu's avatar
Howard Chu committed
496
497
} MDB_reader;

Howard Chu's avatar
Howard Chu committed
498
499
500
501
502
503
504
	/** 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
505
	 *	processes can grab them. This same approach is also used on
Howard Chu's avatar
Howard Chu committed
506
	 *	MacOSX/Darwin (using named semaphores) since MacOSX doesn't support
Howard Chu's avatar
Howard Chu committed
507
508
509
510
	 *	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
511
	 */
Howard Chu's avatar
Howard Chu committed
512
typedef struct MDB_txbody {
Hallvard Furuseth's avatar
Hallvard Furuseth committed
513
		/** Stamp identifying this as an MDB file. It must be set
Howard Chu's avatar
Howard Chu committed
514
		 *	to #MDB_MAGIC. */
Howard Chu's avatar
Howard Chu committed
515
	uint32_t	mtb_magic;
Howard Chu's avatar
Howard Chu committed
516
		/** Version number of this lock file. Must be set to #MDB_VERSION. */
Howard Chu's avatar
Howard Chu committed
517
	uint32_t	mtb_version;
518
#if defined(_WIN32) || defined(MDB_USE_POSIX_SEM)
Howard Chu's avatar
Howard Chu committed
519
	char	mtb_rmname[MNAME_LEN];
Howard Chu's avatar
Howard Chu committed
520
#else
Howard Chu's avatar
Howard Chu committed
521
522
523
		/** Mutex protecting access to this table.
		 *	This is the reader lock that #LOCK_MUTEX_R acquires.
		 */
Howard Chu's avatar
Howard Chu committed
524
	pthread_mutex_t	mtb_mutex;
Howard Chu's avatar
Howard Chu committed
525
#endif
Howard Chu's avatar
Howard Chu committed
526
527
528
529
		/**	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.
		 */
530
	txnid_t		mtb_txnid;
Howard Chu's avatar
Howard Chu committed
531
532
533
534
		/** 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.
		 */
535
	unsigned	mtb_numreaders;
Howard Chu's avatar
Howard Chu committed
536
537
} MDB_txbody;

Howard Chu's avatar
Howard Chu committed
538
	/** The actual reader table definition. */
Howard Chu's avatar
Howard Chu committed
539
typedef struct MDB_txninfo {
Howard Chu's avatar
Howard Chu committed
540
541
542
543
544
	union {
		MDB_txbody mtb;
#define mti_magic	mt1.mtb.mtb_magic
#define mti_version	mt1.mtb.mtb_version
#define mti_mutex	mt1.mtb.mtb_mutex
Howard Chu's avatar
Howard Chu committed
545
#define mti_rmname	mt1.mtb.mtb_rmname
Howard Chu's avatar
Howard Chu committed
546
547
548
549
550
#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 {
551
#if defined(_WIN32) || defined(MDB_USE_POSIX_SEM)
Howard Chu's avatar
Howard Chu committed
552
		char mt2_wmname[MNAME_LEN];
Howard Chu's avatar
Howard Chu committed
553
554
#define	mti_wmname	mt2.mt2_wmname
#else
Howard Chu's avatar
Howard Chu committed
555
556
		pthread_mutex_t	mt2_wmutex;
#define mti_wmutex	mt2.mt2_wmutex
Howard Chu's avatar
Howard Chu committed
557
#endif
558
		char pad[(MNAME_LEN+CACHELINE-1) & ~(CACHELINE-1)];
Howard Chu's avatar
Howard Chu committed
559
560
	} mt2;
	MDB_reader	mti_readers[1];
Howard Chu's avatar
Howard Chu committed
561
} MDB_txninfo;
Howard Chu's avatar
Howard Chu committed
562
/** @} */
Howard Chu's avatar
Howard Chu committed
563

Howard Chu's avatar
Howard Chu committed
564
/** Common header for all page types.
Howard Chu's avatar
Howard Chu committed
565
 * Overflow records occupy a number of contiguous pages with no
Howard Chu's avatar
Howard Chu committed
566
567
 * headers on any page after the first.
 */
Howard Chu's avatar
Howard Chu committed
568
typedef struct MDB_page {
569
570
#define	mp_pgno	mp_p.p_pgno
#define	mp_next	mp_p.p_next
Howard Chu's avatar
Howard Chu committed
571
	union {
572
573
574
		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
575
	uint16_t	mp_pad;
Howard Chu's avatar
Howard Chu committed
576
577
578
579
580
/**	@defgroup mdb_page	Page Flags
 *	@ingroup internal
 *	Flags for the page headers.
 *	@{
 */
Howard Chu's avatar
Howard Chu committed
581
582
583
584
585
586
#define	P_BRANCH	 0x01		/**< branch page */
#define	P_LEAF		 0x02		/**< leaf page */
#define	P_OVERFLOW	 0x04		/**< overflow page */
#define	P_META		 0x08		/**< meta page */
#define	P_DIRTY		 0x10		/**< dirty page */
#define	P_LEAF2		 0x20		/**< for #MDB_DUPFIXED records */
Howard Chu's avatar
Howard Chu committed
587
#define	P_SUBP		 0x40		/**< for #MDB_DUPSORT sub-pages */
Howard Chu's avatar
Howard Chu committed
588
#define	P_KEEP		 0x8000		/**< leave this page alone during spill */
Howard Chu's avatar
Howard Chu committed
589
/** @} */
Howard Chu's avatar
Howard Chu committed
590
	uint16_t	mp_flags;		/**< @ref mdb_page */
591
592
593
#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
594
	union {
Howard Chu's avatar
Howard Chu committed
595
		struct {
596
597
598
599
600
			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
601
	indx_t		mp_ptrs[1];		/**< dynamic size */
Howard Chu's avatar
Howard Chu committed
602
603
} MDB_page;

Howard Chu's avatar
Howard Chu committed
604
	/** Size of the page header, excluding dynamic data at the end */
605
#define PAGEHDRSZ	 ((unsigned) offsetof(MDB_page, mp_ptrs))
Howard Chu's avatar
Howard Chu committed
606

Howard Chu's avatar
Howard Chu committed
607
608
609
610
	/** 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
611
#define NUMKEYS(p)	 (((p)->mp_lower - PAGEHDRSZ) >> 1)
Howard Chu's avatar
Howard Chu committed
612
613

	/** The amount of space remaining in the page */
Howard Chu's avatar
Howard Chu committed
614
#define SIZELEFT(p)	 (indx_t)((p)->mp_upper - (p)->mp_lower)
Howard Chu's avatar
Howard Chu committed
615
616

	/** The percentage of space used in the page, in tenths of a percent. */
Howard Chu's avatar
Howard Chu committed
617
618
#define PAGEFILL(env, p) (1000L * ((env)->me_psize - PAGEHDRSZ - SIZELEFT(p)) / \
				((env)->me_psize - PAGEHDRSZ))
Howard Chu's avatar
Howard Chu committed
619
620
621
622
623
624
	/** 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
625
#define IS_LEAF(p)	 F_ISSET((p)->mp_flags, P_LEAF)
Howard Chu's avatar
Howard Chu committed
626
	/** Test if a page is a LEAF2 page */
Howard Chu's avatar
Howard Chu committed
627
#define IS_LEAF2(p)	 F_ISSET((p)->mp_flags, P_LEAF2)
Howard Chu's avatar
Howard Chu committed
628
	/** Test if a page is a branch page */
Howard Chu's avatar
Howard Chu committed
629
#define IS_BRANCH(p)	 F_ISSET((p)->mp_flags, P_BRANCH)
Howard Chu's avatar
Howard Chu committed
630
	/** Test if a page is an overflow page */
Howard Chu's avatar
Howard Chu committed
631
#define IS_OVERFLOW(p)	 F_ISSET((p)->mp_flags, P_OVERFLOW)
Howard Chu's avatar
Howard Chu committed
632
633
	/** 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
634

Howard Chu's avatar
Howard Chu committed
635
	/** The number of overflow pages needed to store the given size. */
636
#define OVPAGES(size, psize)	((PAGEHDRSZ-1 + (size)) / (psize) + 1)
Howard Chu's avatar
Howard Chu committed
637

Howard Chu's avatar
Howard Chu committed
638
639
640
641
642
643
	/** Header for a single key/data pair within a page.
	 * We guarantee 2-byte alignment for nodes.
	 */
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
644
	 * is also used for pgno. (Branch nodes have no flags).
Howard Chu's avatar
Howard Chu committed
645
	 * They are in host byte order in case that lets some
646
	 * accesses be optimized into a 32-bit word access.
Howard Chu's avatar
Howard Chu committed
647
	 */
Howard Chu's avatar
Howard Chu committed
648
649
#define mn_lo mn_offset[BYTE_ORDER!=LITTLE_ENDIAN]
#define mn_hi mn_offset[BYTE_ORDER==LITTLE_ENDIAN] /**< part of dsize or pgno */
Howard Chu's avatar
Howard Chu committed
650
651
652
653
654
655
	unsigned short	mn_offset[2];	/**< storage for #mn_lo and #mn_hi */
/** @defgroup mdb_node Node Flags
 *	@ingroup internal
 *	Flags for node headers.
 *	@{
 */
Howard Chu's avatar
Howard Chu committed
656
657
658
#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
659
660

/** valid flags for #mdb_node_add() */
661
#define	NODE_ADD_FLAGS	(F_DUPDATA|F_SUBDATA|MDB_RESERVE|MDB_APPEND)
Howard Chu's avatar
Howard Chu committed
662

Howard Chu's avatar
Howard Chu committed
663
664
/** @} */
	unsigned short	mn_flags;		/**< @ref mdb_node */
Howard Chu's avatar
Howard Chu committed
665
666
667
668
669
670
671
	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)

672
673
674
	/** 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
675
	/** Size of a node in a branch page with a given key.
Howard Chu's avatar
Howard Chu committed
676
677
678
679
	 *	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
680
	/** Size of a node in a leaf page with a given key and data.
Howard Chu's avatar
Howard Chu committed
681
682
683
684
	 *	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
685
	/** Address of node \b i in page \b p */
Howard Chu's avatar
Howard Chu committed
686
687
688
689
690
691
692
693
694
#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 */
695
696
697
#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
698
699
700
	/** Set the page number in a branch node */
#define SETPGNO(node,pgno)	do { \
	(node)->mn_lo = (pgno) & 0xffff; (node)->mn_hi = (pgno) >> 16; \
701
	if (PGNO_TOPWORD) (node)->mn_flags = (pgno) >> PGNO_TOPWORD; } while(0)
Howard Chu's avatar
Howard Chu committed
702
703
704
705
706
707
708
709
710

	/** 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
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
	/** 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
735
736
737
738
739
740
741
	/** 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)))

	/** Set the \b node's key into \b key, if requested. */
Howard Chu's avatar
Howard Chu committed
742
#define MDB_GET_KEY(node, key)	{ if ((key) != NULL) { \
Hallvard Furuseth's avatar
Hallvard Furuseth committed
743
	(key)->mv_size = NODEKSZ(node); (key)->mv_data = NODEKEY(node); } }
Howard Chu's avatar
Howard Chu committed
744
745

	/** Information about a single database in the environment. */
Howard Chu's avatar
Howard Chu committed
746
typedef struct MDB_db {
Howard Chu's avatar
Howard Chu committed
747
	uint32_t	md_pad;		/**< also ksize for LEAF2 pages */
748
	uint16_t	md_flags;	/**< @ref mdb_dbi_open */
Howard Chu's avatar
Howard Chu committed
749
	uint16_t	md_depth;	/**< depth of this tree */
750
751
752
753
	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
754
	pgno_t		md_root;		/**< the root page of this tree */
Howard Chu's avatar
Howard Chu committed
755
756
} MDB_db;

757
	/** mdb_dbi_open flags */
758
759
#define MDB_VALID	0x8000		/**< DB handle is valid, for me_dbflags */
#define PERSISTENT_FLAGS	(0xffff & ~(MDB_VALID))
760
761
762
#define VALID_FLAGS	(MDB_REVERSEKEY|MDB_DUPSORT|MDB_INTEGERKEY|MDB_DUPFIXED|\
	MDB_INTEGERDUP|MDB_REVERSEDUP|MDB_CREATE)

Howard Chu's avatar
Howard Chu committed
763
	/** Handle for the DB used to track free pages. */
Howard Chu's avatar
Howard Chu committed
764
#define	FREE_DBI	0
Howard Chu's avatar
Howard Chu committed
765
	/** Handle for the default DB. */
Howard Chu's avatar
Howard Chu committed
766
767
#define	MAIN_DBI	1

Howard Chu's avatar
Howard Chu committed
768
769
	/** Meta page content. */
typedef struct MDB_meta {
Hallvard Furuseth's avatar
Hallvard Furuseth committed
770
		/** Stamp identifying this as an MDB file. It must be set
Howard Chu's avatar
Howard Chu committed
771
		 *	to #MDB_MAGIC. */
Howard Chu's avatar
Howard Chu committed
772
	uint32_t	mm_magic;
Howard Chu's avatar
Howard Chu committed
773
		/** Version number of this lock file. Must be set to #MDB_VERSION. */
Howard Chu's avatar
Howard Chu committed
774
	uint32_t	mm_version;
Howard Chu's avatar
Howard Chu committed
775
776
777
778
	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
779
#define	mm_psize	mm_dbs[0].md_pad
Howard Chu's avatar
Howard Chu committed
780
	/** Any persistent environment flags. @ref mdb_env */
Howard Chu's avatar
Howard Chu committed
781
#define	mm_flags	mm_dbs[0].md_flags
Howard Chu's avatar
Howard Chu committed
782
	pgno_t		mm_last_pg;			/**< last used page in file */
783
	txnid_t		mm_txnid;			/**< txnid that committed this page */
Howard Chu's avatar
Howard Chu committed
784
785
} MDB_meta;

786
787
788
789
790
791
792
793
794
795
796
797
798
799
	/** Buffer for a stack-allocated dirty page.
	 *	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.
	 */
typedef union MDB_pagebuf {
	char		mb_raw[MDB_PAGESIZE];
	MDB_page	mb_page;
	struct {
		char		mm_pad[PAGEHDRSZ];
		MDB_meta	mm_meta;
	} mb_metabuf;
} MDB_pagebuf;

Howard Chu's avatar
Howard Chu committed
800
801
802
803
804
805
806
807
808
	/** 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 */
809
	void		*md_relctx;		/**< user-provided context for md_rel */
Howard Chu's avatar
Howard Chu committed
810
} MDB_dbx;
Howard Chu's avatar
Howard Chu committed
811

Howard Chu's avatar
Howard Chu committed
812
813
814
815
	/** A database transaction.
	 *	Every operation requires a transaction handle.
	 */
struct MDB_txn {
816
817
	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
818
819
820
821
822
	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.
	 */
823
	txnid_t		mt_txnid;
Howard Chu's avatar
Howard Chu committed
824
825
826
	MDB_env		*mt_env;		/**< the DB environment */
	/** The list of pages that became unused during this transaction.
	 */
827
	MDB_IDL		mt_free_pgs;
Howard Chu's avatar
Howard Chu committed
828
829
830
831
	/** The list of dirty pages we temporarily wrote to disk
	 *	because the dirty list was full.
	 */
	MDB_IDL		mt_spill_pgs;
Howard Chu's avatar
Howard Chu committed
832
	union {
833
834
		MDB_ID2L	dirty_list;	/**< for write txns: modified pages */
		MDB_reader	*reader;	/**< this thread's reader table slot or NULL */
Howard Chu's avatar
Howard Chu committed
835
836
837
838
839
	} 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
840
841
842
843
844
845
/** @defgroup mt_dbflag	Transaction DB Flags
 *	@ingroup internal
 * @{
 */
#define DB_DIRTY	0x01		/**< DB was written in this txn */
#define DB_STALE	0x02		/**< DB record is older than txnID */
846
#define DB_NEW		0x04		/**< DB handle opened in this txn */
847
#define DB_VALID	0x08		/**< DB handle is valid, see also #MDB_VALID */
Howard Chu's avatar
Howard Chu committed
848
/** @} */
849
	/** In write txns, array of cursors for each DB */
Howard Chu's avatar
Howard Chu committed
850
	MDB_cursor	**mt_cursors;
Howard Chu's avatar
Howard Chu committed
851
852
	/** Array of flags for each DB */
	unsigned char	*mt_dbflags;
Howard Chu's avatar
Howard Chu committed
853
854
855
	/**	Number of DB records in use. This number only ever increments;
	 *	we don't decrement it when individual DB handles are closed.
	 */
856
	MDB_dbi		mt_numdbs;
Howard Chu's avatar
Howard Chu committed
857

Howard Chu's avatar
Howard Chu committed
858
859
860
861
/** @defgroup mdb_txn	Transaction Flags
 *	@ingroup internal
 *	@{
 */
Howard Chu's avatar
Howard Chu committed
862
863
#define MDB_TXN_RDONLY		0x01		/**< read-only transaction */
#define MDB_TXN_ERROR		0x02		/**< an error has occurred */
864
#define MDB_TXN_DIRTY		0x04		/**< must write, even if dirty list is empty */
Howard Chu's avatar
Howard Chu committed
865
#define MDB_TXN_SPILLS		0x08		/**< txn or a parent has spilled pages */
Howard Chu's avatar
Howard Chu committed
866
867
/** @} */
	unsigned int	mt_flags;		/**< @ref mdb_txn */
Howard Chu's avatar
Howard Chu committed
868
	/** dirty_list maxsize - # of allocated pages allowed, including in parent txns */
869
	unsigned int	mt_dirty_room;
Howard Chu's avatar
Howard Chu committed
870
871
872
873
874
	/** Tracks which of the two meta pages was used at the start
	 * 	of this transaction.
	 */
	unsigned int	mt_toggle;
};
Howard Chu's avatar
Howard Chu committed
875

Howard Chu's avatar
Howard Chu committed
876
/** Enough space for 2^32 nodes with minimum of 2 keys per node. I.e., plenty.
877
878
879
 * 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
880
#define CURSOR_STACK		 32
Howard Chu's avatar
Howard Chu committed
881

Howard Chu's avatar
Howard Chu committed
882
struct MDB_xcursor;
883

Howard Chu's avatar
Howard Chu committed
884
	/** Cursors are used for all DB operations */
Howard Chu's avatar
Howard Chu committed
885
struct MDB_cursor {
Howard Chu's avatar
Howard Chu committed
886
887
	/** Next cursor on this DB in this txn */
	MDB_cursor	*mc_next;
888
889
	/** Backup of the original cursor if this cursor is a shadow */
	MDB_cursor	*mc_backup;
Howard Chu's avatar
Howard Chu committed
890
	/** Context used for databases with #MDB_DUPSORT, otherwise NULL */
Howard Chu's avatar
Howard Chu committed
891
	struct MDB_xcursor	*mc_xcursor;
Howard Chu's avatar
Howard Chu committed
892
	/** The transaction that owns this cursor */
Howard Chu's avatar
Howard Chu committed
893
	MDB_txn		*mc_txn;
Howard Chu's avatar
Howard Chu committed
894
	/** The database handle this cursor operates on */
Howard Chu's avatar
Howard Chu committed
895
	MDB_dbi		mc_dbi;
896
897
898
899
	/** 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
900
901
	/** The @ref mt_dbflag for this database */
	unsigned char	*mc_dbflag;
Howard Chu's avatar
Howard Chu committed
902
	unsigned short 	mc_snum;	/**< number of pushed pages */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
903
	unsigned short	mc_top;		/**< index of top page, normally mc_snum-1 */
Howard Chu's avatar
Howard Chu committed
904
905
906
907
908
/** @defgroup mdb_cursor	Cursor Flags
 *	@ingroup internal
 *	Cursor state flags.
 *	@{
 */
Howard Chu's avatar
Howard Chu committed
909
910
#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
911
#define C_SUB	0x04			/**< Cursor is a sub-cursor */
Howard Chu's avatar
Howard Chu committed
912
#define C_SPLITTING	0x20		/**< Cursor is in page_split */
913
#define C_UNTRACK	0x40		/**< Un-track cursor when closing */
Howard Chu's avatar
Howard Chu committed
914
915
/** @} */
	unsigned int	mc_flags;	/**< @ref mdb_cursor */
Howard Chu's avatar
Howard Chu committed
916
917
	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
918
919
};

Howard Chu's avatar
Howard Chu committed
920
921
922
923
	/** 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.
924
	 */
Howard Chu's avatar
Howard Chu committed
925
typedef struct MDB_xcursor {
Howard Chu's avatar
Howard Chu committed
926
	/** A sub-cursor for traversing the Dup DB */
Howard Chu's avatar
Howard Chu committed
927
	MDB_cursor mx_cursor;
928
929
930
931
	/** 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
932
933
	/** The @ref mt_dbflag for this Dup DB */
	unsigned char mx_dbflag;
Howard Chu's avatar
Howard Chu committed
934
935
} MDB_xcursor;

936
937
	/** State of FreeDB old pages, stored in the MDB_env */
typedef struct MDB_pgstate {
938
939
	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 */
940
941
} MDB_pgstate;

Howard Chu's avatar
Howard Chu committed
942
	/** The database environment. */
Howard Chu's avatar
Howard Chu committed
943
struct MDB_env {
Howard Chu's avatar
Howard Chu committed
944
945
946
	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
947
	/** Failed to update the meta page. Probably an I/O error. */
Howard Chu's avatar
Howard Chu committed
948
#define	MDB_FATAL_ERROR	0x80000000U
Hallvard Furuseth's avatar
Hallvard Furuseth committed
949
950
	/** Some fields are initialized. */
#define	MDB_ENV_ACTIVE	0x20000000U
951
952
	/** me_txkey is set */
#define	MDB_ENV_TXKEY	0x10000000U
Howard Chu's avatar
Howard Chu committed
953
	uint32_t 	me_flags;		/**< @ref mdb_env */
954
	unsigned int	me_psize;	/**< size of a page, from #GET_PAGESIZE */
Howard Chu's avatar
Howard Chu committed
955
	unsigned int	me_maxreaders;	/**< size of the reader table */
956
	unsigned int	me_numreaders;	/**< max numreaders set by this env */
957
958
	MDB_dbi		me_numdbs;		/**< number of DBs opened */
	MDB_dbi		me_maxdbs;		/**< size of the DB table */
959
	pid_t		me_pid;		/**< process ID of this env */
Howard Chu's avatar
Howard Chu committed
960
961
	char		*me_path;		/**< path to the DB files */
	char		*me_map;		/**< the memory map of the data file */
962
	MDB_txninfo	*me_txns;		/**< the memory map of the lock file or NULL */
Howard Chu's avatar
Howard Chu committed
963
964
965
966
967
968
	MDB_meta	*me_metas[2];	/**< pointers to the two meta pages */
	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 */
969
	uint16_t	*me_dbflags;	/**< array of flags from MDB_db.md_flags */
Howard Chu's avatar
Howard Chu committed
970
	pthread_key_t	me_txkey;	/**< thread-key for readers */
971
972
973
	MDB_pgstate	me_pgstate;		/**< state of old pages from freeDB */
#	define		me_pglast	me_pgstate.mf_pglast
#	define		me_pghead	me_pgstate.mf_pghead
Howard Chu's avatar
Howard Chu committed
974
975
	MDB_page	*me_dpages;		/**< list of malloc'd blocks for re-use */
	/** IDL of pages that became unused in a write txn */
976
	MDB_IDL		me_free_pgs;
Hallvard Furuseth's avatar
Hallvard Furuseth committed
977
978
	/** ID2L of pages written during a write txn. Length MDB_IDL_UM_SIZE. */
	MDB_ID2L	me_dirty_list;
979
	/** Max number of freelist items that can fit in a single overflow page */
980
	int			me_maxfree_1pg;
Howard Chu's avatar
Howard Chu committed
981
982
	/** Max size of a node on a page */
	unsigned int	me_nodemax;
Howard Chu's avatar
Howard Chu committed
983
984
985
#ifdef _WIN32
	HANDLE		me_rmutex;		/* Windows mutexes don't reside in shared mem */
	HANDLE		me_wmutex;
986
987
#elif defined(MDB_USE_POSIX_SEM)
	sem_t		*me_rmutex;		/* Shared mutexes are not supported */
Howard Chu's avatar
Howard Chu committed
988
989
	sem_t		*me_wmutex;
#endif
Howard Chu's avatar
Howard Chu committed
990
};
991
992
993
994
995
996
997

	/** Nested transaction */
typedef struct MDB_ntxn {
	MDB_txn		mnt_txn;		/* the transaction */
	MDB_pgstate	mnt_pgstate;	/* parent transaction's saved freestate */
} MDB_ntxn;

Howard Chu's avatar
Howard Chu committed
998
999
	/** max number of pages to commit in one writev() call */
#define MDB_COMMIT_PAGES	 64
1000
1001
1002
1003
#if defined(IOV_MAX) && IOV_MAX < MDB_COMMIT_PAGES
#undef MDB_COMMIT_PAGES
#define MDB_COMMIT_PAGES	IOV_MAX
#endif
Howard Chu's avatar
Howard Chu committed
1004

1005
1006
1007
	/* max bytes to write in one call */
#define MAX_WRITE		(0x80000000U >> (sizeof(ssize_t) == 4))

1008
1009
1010
static int  mdb_page_alloc(MDB_cursor *mc, int num, MDB_page **mp);
static int  mdb_page_new(MDB_cursor *mc, uint32_t flags, int num, MDB_page **mp);
static int  mdb_page_touch(MDB_cursor *mc);
Howard Chu's avatar
Howard Chu committed
1011

1012
static int  mdb_page_get(MDB_txn *txn, pgno_t pgno, MDB_page **mp, int *lvl);
Howard Chu's avatar
Howard Chu committed
1013
static int  mdb_page_search_root(MDB_cursor *mc,
1014
			    MDB_val *key, int modify);
1015
1016
#define MDB_PS_MODIFY	1
#define MDB_PS_ROOTONLY	2
Howard Chu's avatar
Howard Chu committed
1017
static int  mdb_page_search(MDB_cursor *mc,
1018
			    MDB_val *key, int flags);
Howard Chu's avatar
Howard Chu committed
1019
static int	mdb_page_merge(MDB_cursor *csrc, MDB_cursor *cdst);
Howard Chu's avatar
Howard Chu committed
1020
1021

#define MDB_SPLIT_REPLACE	MDB_APPENDDUP	/**< newkey is not new */
Howard Chu's avatar
Howard Chu committed
1022
static int	mdb_page_split(MDB_cursor *mc, MDB_val *newkey, MDB_val *newdata,
Howard Chu's avatar
Howard Chu committed
1023
				pgno_t newpgno, unsigned int nflags);
Howard Chu's avatar
Howard Chu committed
1024

Howard Chu's avatar
Howard Chu committed
1025
static int  mdb_env_read_header(MDB_env *env, MDB_meta *meta);
1026
static int  mdb_env_pick_meta(const MDB_env *env);
Howard Chu's avatar
Howard Chu committed
1027
static int  mdb_env_write_meta(MDB_txn *txn);
Hallvard Furuseth's avatar
Hallvard Furuseth committed
1028
1029
1030
#if !(defined(_WIN32) || defined(MDB_USE_POSIX_SEM)) /* Drop unused excl arg */
# define mdb_env_close0(env, excl) mdb_env_close1(env)
#endif
1031
static void mdb_env_close0(MDB_env *env, int excl);
Howard Chu's avatar
Howard Chu committed
1032

Howard Chu's avatar
Howard Chu committed
1033
1034
static MDB_node *mdb_node_search(MDB_cursor *mc, MDB_val *key, int *exactp);
static int  mdb_node_add(MDB_cursor *mc, indx_t indx,
Howard Chu's avatar
Howard Chu committed
1035
			    MDB_val *key, MDB_val *data, pgno_t pgno, unsigned int flags);
Howard Chu's avatar
Howard Chu committed
1036
static void mdb_node_del(MDB_page *mp, indx_t indx, int ksize);
Howard Chu's avatar
Howard Chu committed
1037
static void mdb_node_shrink(MDB_page *mp, indx_t indx);
Howard Chu's avatar
Howard Chu committed
1038
static int	mdb_node_move(MDB_cursor *csrc, MDB_cursor *cdst);
Howard Chu's avatar
Howard Chu committed
1039
static int  mdb_node_read(MDB_txn *txn, MDB_node *leaf, MDB_val *data);
Howard Chu's avatar
Howard Chu committed
1040
1041
static size_t	mdb_leaf_size(MDB_env *env, MDB_val *key, MDB_val *data);
static size_t	mdb_branch_size(MDB_env *env, MDB_val *key);
Howard Chu's avatar
Howard Chu committed
1042

1043
static int	mdb_rebalance(MDB_cursor *mc);
1044
static int	mdb_update_key(MDB_cursor *mc, MDB_val *key);
1045

Howard Chu's avatar
Howard Chu committed
1046
1047
static void	mdb_cursor_pop(MDB_cursor *mc);
static int	mdb_cursor_push(MDB_cursor *mc, MDB_page *mp);
1048

Howard Chu's avatar
Howard Chu committed
1049
static int	mdb_cursor_del0(MDB_cursor *mc, MDB_node *leaf);
Howard Chu's avatar
Howard Chu committed
1050
static int	mdb_cursor_sibling(MDB_cursor *mc, int move_right);
1051
1052
1053
1054
1055
1056
static int	mdb_cursor_next(MDB_cursor *mc, MDB_val *key, MDB_val *data, MDB_cursor_op op);
static int	mdb_cursor_prev(MDB_cursor *mc, MDB_val *key, MDB_val *data, MDB_cursor_op op);
static int	mdb_cursor_set(MDB_cursor *mc, MDB_val *key, MDB_val *data, MDB_cursor_op op,
				int *exactp);
static int	mdb_cursor_first(MDB_cursor *mc, MDB_val *key, MDB_val *data);
static int	mdb_cursor_last(MDB_cursor *mc, MDB_val *key, MDB_val *data);
Howard Chu's avatar
Howard Chu committed
1057

Howard Chu's avatar
Howard Chu committed
1058
static void	mdb_cursor_init(MDB_cursor *mc, MDB_txn *txn, MDB_dbi dbi, MDB_xcursor *mx);
Howard Chu's avatar
Howard Chu committed
1059
static void	mdb_xcursor_init0(MDB_cursor *mc);
1060
static void	mdb_xcursor_init1(MDB_cursor *mc, MDB_node *node);
Howard Chu's avatar
Howard Chu committed
1061

Howard Chu's avatar
Howard Chu committed
1062
static int	mdb_drop0(MDB_cursor *mc, int subs);
Howard Chu's avatar
Howard Chu committed
1063
1064
static void mdb_default_cmp(MDB_txn *txn, MDB_dbi dbi);