mdb.c 144 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
8
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
/*
 * Copyright 2011 Howard Chu, Symas Corp.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted only as authorized by the OpenLDAP
 * 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.
 */
Howard Chu's avatar
Howard Chu committed
35
36
37
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/param.h>
Howard Chu's avatar
Howard Chu committed
38
39
40
#ifdef _WIN32
#include <windows.h>
#else
Howard Chu's avatar
Howard Chu committed
41
42
43
44
45
#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
46
#include <fcntl.h>
Howard Chu's avatar
Howard Chu committed
47
#endif
Howard Chu's avatar
Howard Chu committed
48
49
50

#include <assert.h>
#include <errno.h>
51
#include <limits.h>
Howard Chu's avatar
Howard Chu committed
52
53
54
55
56
57
58
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
59
60
61

#ifndef _WIN32
#include <pthread.h>
Howard Chu's avatar
Howard Chu committed
62
63
64
65
66
67
68
69
70
71
72
73
74
#ifdef __APPLE__
#include <semaphore.h>
#endif
#endif

#ifndef BYTE_ORDER
#define BYTE_ORDER	__BYTE_ORDER
#endif
#ifndef LITTLE_ENDIAN
#define LITTLE_ENDIAN	__LITTLE_ENDIAN
#endif
#ifndef BIG_ENDIAN
#define BIG_ENDIAN	__BIG_ENDIAN
75
76
77
78
79
#endif

#include "mdb.h"
#include "midl.h"

Howard Chu's avatar
Howard Chu committed
80
81
#if (BYTE_ORDER == LITTLE_ENDIAN) == (BYTE_ORDER == BIG_ENDIAN)
# error "Unknown or unsupported endianness (BYTE_ORDER)"
82
83
84
85
#elif (-6 & 5) || CHAR_BIT != 8 || UINT_MAX < 0xffffffff || ULONG_MAX % 0xFFFF
# error "Two's complement, reasonably sized integer types, please"
#endif

86
87
88
89
/** @defgroup internal	MDB Internals
 *	@{
 */
/** @defgroup compat	Windows Compatibility Macros
Howard Chu's avatar
Howard Chu committed
90
91
92
93
 *	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.
94
95
 *	@{
 */
Howard Chu's avatar
Howard Chu committed
96
97
98
99
100
#ifdef _WIN32
#define pthread_t	DWORD
#define pthread_mutex_t	HANDLE
#define pthread_key_t	DWORD
#define pthread_self()	GetCurrentThreadId()
Hallvard Furuseth's avatar
Hallvard Furuseth committed
101
#define pthread_key_create(x,y)	(*(x) = TlsAlloc())
Howard Chu's avatar
Howard Chu committed
102
103
104
105
106
#define pthread_key_delete(x)	TlsFree(x)
#define pthread_getspecific(x)	TlsGetValue(x)
#define pthread_setspecific(x,y)	TlsSetValue(x,y)
#define pthread_mutex_unlock(x)	ReleaseMutex(x)
#define pthread_mutex_lock(x)	WaitForSingleObject(x, INFINITE)
Hallvard Furuseth's avatar
Hallvard Furuseth committed
107
108
109
110
#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
111
#define getpid()	GetCurrentProcessId()
Hallvard Furuseth's avatar
Hallvard Furuseth committed
112
#define	fdatasync(fd)	(!FlushFileBuffers(fd))
Howard Chu's avatar
Howard Chu committed
113
#define	ErrCode()	GetLastError()
Hallvard Furuseth's avatar
Hallvard Furuseth committed
114
#define GET_PAGESIZE(x) {SYSTEM_INFO si; GetSystemInfo(&si); (x) = si.dwPageSize;}
Howard Chu's avatar
Howard Chu committed
115
116
#define	close(fd)	CloseHandle(fd)
#define	munmap(ptr,len)	UnmapViewOfFile(ptr)
Howard Chu's avatar
Howard Chu committed
117
118
119
120
121
122
123
#else
#ifdef __APPLE__
#define LOCK_MUTEX_R(env)	sem_wait((env)->me_rmutex)
#define UNLOCK_MUTEX_R(env)	sem_post((env)->me_rmutex)
#define LOCK_MUTEX_W(env)	sem_wait((env)->me_wmutex)
#define UNLOCK_MUTEX_W(env)	sem_post((env)->me_wmutex)
#define fdatasync(fd)	fsync(fd)
Howard Chu's avatar
Howard Chu committed
124
#else
Howard Chu's avatar
Howard Chu committed
125
126
	/** Lock the reader mutex.
	 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
127
#define LOCK_MUTEX_R(env)	pthread_mutex_lock(&(env)->me_txns->mti_mutex)
Howard Chu's avatar
Howard Chu committed
128
129
	/** Unlock the reader mutex.
	 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
130
#define UNLOCK_MUTEX_R(env)	pthread_mutex_unlock(&(env)->me_txns->mti_mutex)
Howard Chu's avatar
Howard Chu committed
131
132
133
134
135

	/** 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
136
#define LOCK_MUTEX_W(env)	pthread_mutex_lock(&(env)->me_txns->mti_wmutex)
Howard Chu's avatar
Howard Chu committed
137
138
	/** Unlock the writer mutex.
	 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
139
#define UNLOCK_MUTEX_W(env)	pthread_mutex_unlock(&(env)->me_txns->mti_wmutex)
Howard Chu's avatar
Howard Chu committed
140
#endif	/* __APPLE__ */
Howard Chu's avatar
Howard Chu committed
141
142
143

	/** Get the error code for the last failed system function.
	 */
Howard Chu's avatar
Howard Chu committed
144
#define	ErrCode()	errno
Howard Chu's avatar
Howard Chu committed
145
146
147
148
149

	/** An abstraction for a file handle.
	 *	On POSIX systems file handles are small integers. On Windows
	 *	they're opaque pointers.
	 */
Howard Chu's avatar
Howard Chu committed
150
#define	HANDLE	int
Howard Chu's avatar
Howard Chu committed
151
152
153
154
155

	/**	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
156
#define INVALID_HANDLE_VALUE	(-1)
Howard Chu's avatar
Howard Chu committed
157
158
159
160
161

	/** 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
162
#define	GET_PAGESIZE(x)	((x) = sysconf(_SC_PAGE_SIZE))
Howard Chu's avatar
Howard Chu committed
163
#endif
Howard Chu's avatar
Howard Chu committed
164

Howard Chu's avatar
Howard Chu committed
165
166
167
168
#if defined(_WIN32) || defined(__APPLE__)
#define MNAME_LEN	32
#endif

169
/** @} */
Howard Chu's avatar
Howard Chu committed
170

171
#ifndef _WIN32
Howard Chu's avatar
Howard Chu committed
172
173
174
175
176
177
/**	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
178
179
180
181
182
183
 * 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
184
185
#endif

Howard Chu's avatar
Howard Chu committed
186
187
188
189
190
191
192
193
	/** 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.
	 */
194
typedef ID	pgno_t;
Hallvard Furuseth's avatar
Hallvard Furuseth committed
195

196
197
198
	/** A transaction ID.
	 *	See struct MDB_txn.mt_txnid for details.
	 */
199
typedef ID	txnid_t;
Hallvard Furuseth's avatar
Hallvard Furuseth committed
200

Howard Chu's avatar
Howard Chu committed
201
202
203
/** @defgroup debug	Debug Macros
 *	@{
 */
204
#ifndef DEBUG
Howard Chu's avatar
Howard Chu committed
205
206
207
208
	/**	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).
	 */
209
#define DEBUG 0
210
#endif
Howard Chu's avatar
Howard Chu committed
211

212
213
214
#if !(__STDC_VERSION__ >= 199901L || defined(__GNUC__))
# define DPRINTF	(void)	/* Vararg macros may be unsupported */
#elif DEBUG
Howard Chu's avatar
Howard Chu committed
215
216
	/**	Print a debug message with printf formatting. */
# define DPRINTF(fmt, ...)	/**< Requires 2 or more args */ \
217
	fprintf(stderr, "%s:%d " fmt "\n", __func__, __LINE__, __VA_ARGS__)
Howard Chu's avatar
Howard Chu committed
218
#else
219
# define DPRINTF(fmt, ...)	((void) 0)
Howard Chu's avatar
Howard Chu committed
220
#endif
Howard Chu's avatar
Howard Chu committed
221
222
223
	/**	Print a debug string.
	 *	The string is printed literally, with no format processing.
	 */
224
#define DPUTS(arg)	DPRINTF("%s", arg)
Howard Chu's avatar
Howard Chu committed
225
/** @} */
Howard Chu's avatar
Howard Chu committed
226

Howard Chu's avatar
Howard Chu committed
227
228
229
	/** 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
230
	 *	The #GET_PAGESIZE() macro is used to get the actual size.
Howard Chu's avatar
Howard Chu committed
231
232
233
234
235
236
237
238
	 *
	 *	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
239
#define PAGESIZE	 4096
Howard Chu's avatar
Howard Chu committed
240
241
242
243
244
245
246
247
248
249
250
251
252

	/** 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
253
#define MDB_MINKEYS	 2
Howard Chu's avatar
Howard Chu committed
254
255
256
257
258

	/**	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
259
#define MDB_MAGIC	 0xBEEFC0DE
Howard Chu's avatar
Howard Chu committed
260
261

	/**	The version number for a database's file format. */
Howard Chu's avatar
Howard Chu committed
262
#define MDB_VERSION	 1
Howard Chu's avatar
Howard Chu committed
263
264
265
266
267
268

	/**	The maximum size of a key in the database.
	 *	While data items have essentially unbounded size, we require that
	 *	keys all fit onto a regular page. This limit could be raised a bit
	 *	further if needed; to something just under #PAGESIZE / #MDB_MINKEYS.
	 */
Howard Chu's avatar
Howard Chu committed
269
#define MAXKEYSIZE	 511
Howard Chu's avatar
Howard Chu committed
270

Howard Chu's avatar
Howard Chu committed
271
#if DEBUG
Howard Chu's avatar
Howard Chu committed
272
273
274
275
276
277
278
279
280
	/**	A key buffer.
	 *	@ingroup debug
	 *	This is used for printing a hex dump of a key's contents.
	 */
#define DKBUF	char kbuf[(MAXKEYSIZE*2+1)]
	/**	Display a key in hex.
	 *	@ingroup debug
	 *	Invoke a function to display a key in hex.
	 */
Howard Chu's avatar
Howard Chu committed
281
282
#define	DKEY(x)	mdb_dkey(x, kbuf)
#else
283
#define	DKBUF	typedef int dummy_kbuf	/* so we can put ';' after */
Howard Chu's avatar
Howard Chu committed
284
285
#define DKEY(x)
#endif
Howard Chu's avatar
Howard Chu committed
286

Howard Chu's avatar
Howard Chu committed
287
288
289
290
291
/**	@defgroup lazylock	Lazy Locking
 *	Macros for locks that are't actually needed.
 *	The DB view is always consistent because all writes are wrapped in
 *	the wmutex. Finer-grained locks aren't necessary.
 *	@{
Howard Chu's avatar
Howard Chu committed
292
293
 */
#ifndef	LAZY_LOCKS
Howard Chu's avatar
Howard Chu committed
294
	/**	Use lazy locking. I.e., don't lock these accesses at all. */
Howard Chu's avatar
Howard Chu committed
295
296
297
#define	LAZY_LOCKS	1
#endif
#if	LAZY_LOCKS
Howard Chu's avatar
Howard Chu committed
298
	/** Grab the reader lock */
Howard Chu's avatar
Howard Chu committed
299
#define	LAZY_MUTEX_LOCK(x)
Howard Chu's avatar
Howard Chu committed
300
	/** Release the reader lock */
Howard Chu's avatar
Howard Chu committed
301
#define	LAZY_MUTEX_UNLOCK(x)
Howard Chu's avatar
Howard Chu committed
302
	/** Release the DB table reader/writer lock */
Howard Chu's avatar
Howard Chu committed
303
#define	LAZY_RWLOCK_UNLOCK(x)
Howard Chu's avatar
Howard Chu committed
304
	/** Grab the DB table write lock */
Howard Chu's avatar
Howard Chu committed
305
#define	LAZY_RWLOCK_WRLOCK(x)
Howard Chu's avatar
Howard Chu committed
306
	/** Grab the DB table read lock */
Howard Chu's avatar
Howard Chu committed
307
#define	LAZY_RWLOCK_RDLOCK(x)
308
	/** Declare the DB table rwlock.  Should not be followed by ';'. */
Howard Chu's avatar
Howard Chu committed
309
#define	LAZY_RWLOCK_DEF(x)
Howard Chu's avatar
Howard Chu committed
310
	/** Initialize the DB table rwlock */
Howard Chu's avatar
Howard Chu committed
311
#define	LAZY_RWLOCK_INIT(x,y)
Howard Chu's avatar
Howard Chu committed
312
	/**	Destroy the DB table rwlock */
Howard Chu's avatar
Howard Chu committed
313
314
315
316
317
318
319
#define	LAZY_RWLOCK_DESTROY(x)
#else
#define	LAZY_MUTEX_LOCK(x)		pthread_mutex_lock(x)
#define	LAZY_MUTEX_UNLOCK(x)	pthread_mutex_unlock(x)
#define	LAZY_RWLOCK_UNLOCK(x)	pthread_rwlock_unlock(x)
#define	LAZY_RWLOCK_WRLOCK(x)	pthread_rwlock_wrlock(x)
#define	LAZY_RWLOCK_RDLOCK(x)	pthread_rwlock_rdlock(x)
320
#define	LAZY_RWLOCK_DEF(x)		pthread_rwlock_t	x;
Howard Chu's avatar
Howard Chu committed
321
322
323
#define	LAZY_RWLOCK_INIT(x,y)	pthread_rwlock_init(x,y)
#define	LAZY_RWLOCK_DESTROY(x)	pthread_rwlock_destroy(x)
#endif
Howard Chu's avatar
Howard Chu committed
324
/** @} */
Howard Chu's avatar
Howard Chu committed
325

Howard Chu's avatar
Howard Chu committed
326
327
328
	/** An invalid page number.
	 *	Mainly used to denote an empty tree.
	 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
329
#define P_INVALID	 (~0UL)
Howard Chu's avatar
Howard Chu committed
330

Howard Chu's avatar
Howard Chu committed
331
	/** Test if a flag \b f is set in a flag word \b w. */
Howard Chu's avatar
Howard Chu committed
332
333
#define F_ISSET(w, f)	 (((w) & (f)) == (f))

Howard Chu's avatar
Howard Chu committed
334
335
336
337
	/**	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
338
339
typedef uint16_t	 indx_t;

Howard Chu's avatar
Howard Chu committed
340
341
342
343
	/**	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
344
345
#define DEFAULT_MAPSIZE	1048576

Howard Chu's avatar
Howard Chu committed
346
347
348
349
350
351
352
353
354
355
/**	@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.
 *
 *	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
356
357
 *	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
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
 *	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.
 *
 *	@todo We don't actually do such coalescing yet, we grab pages from one
 *	old transaction at a time.
 *	@{
 */
	/**	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
395
#ifndef CACHELINE
Howard Chu's avatar
Howard Chu committed
396
#define CACHELINE	64
Howard Chu's avatar
Howard Chu committed
397
398
#endif

Howard Chu's avatar
Howard Chu committed
399
400
401
402
403
404
405
406
	/**	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
407
typedef struct MDB_rxbody {
Howard Chu's avatar
Howard Chu committed
408
409
410
411
412
413
414
	/**	The current Transaction ID when this transaction began.
	 *	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.
	 */
415
	txnid_t		mrb_txnid;
Howard Chu's avatar
Howard Chu committed
416
	/** The process ID of the process owning this reader txn. */
Howard Chu's avatar
Howard Chu committed
417
	pid_t		mrb_pid;
Howard Chu's avatar
Howard Chu committed
418
	/** The thread ID of the thread owning this txn. */
Howard Chu's avatar
Howard Chu committed
419
420
421
	pthread_t	mrb_tid;
} MDB_rxbody;

Howard Chu's avatar
Howard Chu committed
422
	/** The actual reader record, with cacheline padding. */
Howard Chu's avatar
Howard Chu committed
423
typedef struct MDB_reader {
Howard Chu's avatar
Howard Chu committed
424
425
	union {
		MDB_rxbody mrx;
Howard Chu's avatar
Howard Chu committed
426
		/** shorthand for mrb_txnid */
Howard Chu's avatar
Howard Chu committed
427
428
429
#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
430
		/** cache line alignment */
Howard Chu's avatar
Howard Chu committed
431
432
		char pad[(sizeof(MDB_rxbody)+CACHELINE-1) & ~(CACHELINE-1)];
	} mru;
Howard Chu's avatar
Howard Chu committed
433
434
} MDB_reader;

Howard Chu's avatar
Howard Chu committed
435
436
437
438
439
440
441
442
443
444
445
	/** 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
	 *	processes can grab them. This same approach will also be used on
	 *	MacOSX/Darwin (using named semaphores) since MacOSX doesn't support
	 *	process-shared POSIX mutexes.
	 */
Howard Chu's avatar
Howard Chu committed
446
typedef struct MDB_txbody {
Howard Chu's avatar
Howard Chu committed
447
448
		/** Stamp identifying this as an MDB lock file. It must be set
		 *	to #MDB_MAGIC. */
Howard Chu's avatar
Howard Chu committed
449
	uint32_t	mtb_magic;
Howard Chu's avatar
Howard Chu committed
450
		/** Version number of this lock file. Must be set to #MDB_VERSION. */
Howard Chu's avatar
Howard Chu committed
451
	uint32_t	mtb_version;
Howard Chu's avatar
Howard Chu committed
452
453
#if defined(_WIN32) || defined(__APPLE__)
	char	mtb_rmname[MNAME_LEN];
Howard Chu's avatar
Howard Chu committed
454
#else
Howard Chu's avatar
Howard Chu committed
455
456
457
		/** Mutex protecting access to this table.
		 *	This is the reader lock that #LOCK_MUTEX_R acquires.
		 */
Howard Chu's avatar
Howard Chu committed
458
	pthread_mutex_t	mtb_mutex;
Howard Chu's avatar
Howard Chu committed
459
#endif
Howard Chu's avatar
Howard Chu committed
460
461
462
463
		/**	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.
		 */
464
	txnid_t		mtb_txnid;
Howard Chu's avatar
Howard Chu committed
465
466
467
468
		/** 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.
		 */
469
	unsigned	mtb_numreaders;
Howard Chu's avatar
Howard Chu committed
470
471
472
473
		/**	The ID of the most recent meta page in the database.
		 *	This is recorded here only for convenience; the value can always
		 *	be determined by reading the main database meta pages.
		 */
Howard Chu's avatar
Howard Chu committed
474
	uint32_t	mtb_me_toggle;
Howard Chu's avatar
Howard Chu committed
475
476
} MDB_txbody;

Howard Chu's avatar
Howard Chu committed
477
	/** The actual reader table definition. */
Howard Chu's avatar
Howard Chu committed
478
typedef struct MDB_txninfo {
Howard Chu's avatar
Howard Chu committed
479
480
481
482
483
	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
484
#define mti_rmname	mt1.mtb.mtb_rmname
Howard Chu's avatar
Howard Chu committed
485
486
#define mti_txnid	mt1.mtb.mtb_txnid
#define mti_numreaders	mt1.mtb.mtb_numreaders
Howard Chu's avatar
Howard Chu committed
487
#define mti_me_toggle	mt1.mtb.mtb_me_toggle
Howard Chu's avatar
Howard Chu committed
488
489
490
		char pad[(sizeof(MDB_txbody)+CACHELINE-1) & ~(CACHELINE-1)];
	} mt1;
	union {
Howard Chu's avatar
Howard Chu committed
491
492
#if defined(_WIN32) || defined(__APPLE__)
		char mt2_wmname[MNAME_LEN];
Howard Chu's avatar
Howard Chu committed
493
494
#define	mti_wmname	mt2.mt2_wmname
#else
Howard Chu's avatar
Howard Chu committed
495
496
		pthread_mutex_t	mt2_wmutex;
#define mti_wmutex	mt2.mt2_wmutex
Howard Chu's avatar
Howard Chu committed
497
#endif
Howard Chu's avatar
Howard Chu committed
498
499
500
		char pad[(sizeof(pthread_mutex_t)+CACHELINE-1) & ~(CACHELINE-1)];
	} mt2;
	MDB_reader	mti_readers[1];
Howard Chu's avatar
Howard Chu committed
501
} MDB_txninfo;
Howard Chu's avatar
Howard Chu committed
502
/** @} */
Howard Chu's avatar
Howard Chu committed
503

Howard Chu's avatar
Howard Chu committed
504
/** Common header for all page types.
Howard Chu's avatar
Howard Chu committed
505
 * Overflow records occupy a number of contiguous pages with no
Howard Chu's avatar
Howard Chu committed
506
507
 * headers on any page after the first.
 */
Howard Chu's avatar
Howard Chu committed
508
typedef struct MDB_page {
509
510
#define	mp_pgno	mp_p.p_pgno
#define	mp_next	mp_p.p_next
Howard Chu's avatar
Howard Chu committed
511
	union {
512
513
514
		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
515
	uint16_t	mp_pad;
Howard Chu's avatar
Howard Chu committed
516
517
518
519
520
/**	@defgroup mdb_page	Page Flags
 *	@ingroup internal
 *	Flags for the page headers.
 *	@{
 */
Howard Chu's avatar
Howard Chu committed
521
522
523
524
525
526
#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
527
#define	P_SUBP		 0x40		/**< for #MDB_DUPSORT sub-pages */
Howard Chu's avatar
Howard Chu committed
528
/** @} */
Howard Chu's avatar
Howard Chu committed
529
	uint16_t	mp_flags;		/**< @ref mdb_page */
530
531
532
#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
533
	union {
Howard Chu's avatar
Howard Chu committed
534
		struct {
535
536
537
538
539
			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
540
	indx_t		mp_ptrs[1];		/**< dynamic size */
Howard Chu's avatar
Howard Chu committed
541
542
} MDB_page;

Howard Chu's avatar
Howard Chu committed
543
	/** Size of the page header, excluding dynamic data at the end */
544
#define PAGEHDRSZ	 ((unsigned) offsetof(MDB_page, mp_ptrs))
Howard Chu's avatar
Howard Chu committed
545

Howard Chu's avatar
Howard Chu committed
546
547
548
549
	/** 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
550
#define NUMKEYS(p)	 (((p)->mp_lower - PAGEHDRSZ) >> 1)
Howard Chu's avatar
Howard Chu committed
551
552

	/** The amount of space remaining in the page */
Howard Chu's avatar
Howard Chu committed
553
#define SIZELEFT(p)	 (indx_t)((p)->mp_upper - (p)->mp_lower)
Howard Chu's avatar
Howard Chu committed
554
555

	/** The percentage of space used in the page, in tenths of a percent. */
Howard Chu's avatar
Howard Chu committed
556
557
#define PAGEFILL(env, p) (1000L * ((env)->me_psize - PAGEHDRSZ - SIZELEFT(p)) / \
				((env)->me_psize - PAGEHDRSZ))
Howard Chu's avatar
Howard Chu committed
558
559
560
561
562
563
	/** 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
564
#define IS_LEAF(p)	 F_ISSET((p)->mp_flags, P_LEAF)
Howard Chu's avatar
Howard Chu committed
565
	/** Test if a page is a LEAF2 page */
Howard Chu's avatar
Howard Chu committed
566
#define IS_LEAF2(p)	 F_ISSET((p)->mp_flags, P_LEAF2)
Howard Chu's avatar
Howard Chu committed
567
	/** Test if a page is a branch page */
Howard Chu's avatar
Howard Chu committed
568
#define IS_BRANCH(p)	 F_ISSET((p)->mp_flags, P_BRANCH)
Howard Chu's avatar
Howard Chu committed
569
	/** Test if a page is an overflow page */
Howard Chu's avatar
Howard Chu committed
570
#define IS_OVERFLOW(p)	 F_ISSET((p)->mp_flags, P_OVERFLOW)
Howard Chu's avatar
Howard Chu committed
571
572
	/** 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
573

Howard Chu's avatar
Howard Chu committed
574
	/** The number of overflow pages needed to store the given size. */
575
#define OVPAGES(size, psize)	((PAGEHDRSZ-1 + (size)) / (psize) + 1)
Howard Chu's avatar
Howard Chu committed
576

Howard Chu's avatar
Howard Chu committed
577
578
579
580
581
582
	/** 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
583
	 * is also used for pgno. (Branch nodes have no flags).
Howard Chu's avatar
Howard Chu committed
584
	 * They are in host byte order in case that lets some
585
	 * accesses be optimized into a 32-bit word access.
Howard Chu's avatar
Howard Chu committed
586
	 */
Howard Chu's avatar
Howard Chu committed
587
588
#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
589
590
591
592
593
594
	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
595
596
597
#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
598
599
/** @} */
	unsigned short	mn_flags;		/**< @ref mdb_node */
Howard Chu's avatar
Howard Chu committed
600
601
602
603
604
605
606
	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)

607
608
609
	/** 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
610
	/** Size of a node in a branch page with a given key.
Howard Chu's avatar
Howard Chu committed
611
612
613
614
	 *	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
615
	/** Size of a node in a leaf page with a given key and data.
Howard Chu's avatar
Howard Chu committed
616
617
618
619
	 *	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
620
	/** Address of node \b i in page \b p */
Howard Chu's avatar
Howard Chu committed
621
622
623
624
625
626
627
628
629
#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 */
630
631
632
#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
633
634
635
	/** Set the page number in a branch node */
#define SETPGNO(node,pgno)	do { \
	(node)->mn_lo = (pgno) & 0xffff; (node)->mn_hi = (pgno) >> 16; \
636
	if (PGNO_TOPWORD) (node)->mn_flags = (pgno) >> PGNO_TOPWORD; } while(0)
Howard Chu's avatar
Howard Chu committed
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652

	/** 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)

	/** 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. */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
653
654
#define MDB_SET_KEY(node, key)	{ if ((key) != NULL) { \
	(key)->mv_size = NODEKSZ(node); (key)->mv_data = NODEKEY(node); } }
Howard Chu's avatar
Howard Chu committed
655
656

	/** Information about a single database in the environment. */
Howard Chu's avatar
Howard Chu committed
657
typedef struct MDB_db {
Howard Chu's avatar
Howard Chu committed
658
659
660
	uint32_t	md_pad;		/**< also ksize for LEAF2 pages */
	uint16_t	md_flags;	/**< @ref mdb_open */
	uint16_t	md_depth;	/**< depth of this tree */
661
662
663
664
	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
665
	pgno_t		md_root;		/**< the root page of this tree */
Howard Chu's avatar
Howard Chu committed
666
667
} MDB_db;

Howard Chu's avatar
Howard Chu committed
668
	/** Handle for the DB used to track free pages. */
Howard Chu's avatar
Howard Chu committed
669
#define	FREE_DBI	0
Howard Chu's avatar
Howard Chu committed
670
	/** Handle for the default DB. */
Howard Chu's avatar
Howard Chu committed
671
672
#define	MAIN_DBI	1

Howard Chu's avatar
Howard Chu committed
673
674
675
676
	/** Meta page content. */
typedef struct MDB_meta {
		/** Stamp identifying this as an MDB data file. It must be set
		 *	to #MDB_MAGIC. */
Howard Chu's avatar
Howard Chu committed
677
	uint32_t	mm_magic;
Howard Chu's avatar
Howard Chu committed
678
		/** Version number of this lock file. Must be set to #MDB_VERSION. */
Howard Chu's avatar
Howard Chu committed
679
	uint32_t	mm_version;
Howard Chu's avatar
Howard Chu committed
680
681
682
683
	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
684
#define	mm_psize	mm_dbs[0].md_pad
Howard Chu's avatar
Howard Chu committed
685
	/** Any persistent environment flags. @ref mdb_env */
Howard Chu's avatar
Howard Chu committed
686
#define	mm_flags	mm_dbs[0].md_flags
Howard Chu's avatar
Howard Chu committed
687
	pgno_t		mm_last_pg;			/**< last used page in file */
688
	txnid_t		mm_txnid;			/**< txnid that committed this page */
Howard Chu's avatar
Howard Chu committed
689
690
} MDB_meta;

Howard Chu's avatar
Howard Chu committed
691
692
693
694
695
696
697
698
699
700
701
702
	/** Auxiliary DB info.
	 *	The information here is mostly static/read-only. There is
	 *	only a single copy of this record in the environment.
	 *	The \b md_dirty flag is not read-only, but only a write
	 *	transaction can ever update it, and only write transactions
	 *	need to worry about it.
	 */
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 */
703
	void		*md_relctx;		/**< user-provided context for md_rel */
Howard Chu's avatar
Howard Chu committed
704
705
706
	MDB_dbi	md_parent;			/**< parent DB of a sub-DB */
	unsigned int	md_dirty;	/**< TRUE if DB was written in this txn */
} MDB_dbx;
Howard Chu's avatar
Howard Chu committed
707

Howard Chu's avatar
Howard Chu committed
708
709
710
711
712
713
714
715
716
	/** A database transaction.
	 *	Every operation requires a transaction handle.
	 */
struct MDB_txn {
	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.
	 */
717
	txnid_t		mt_txnid;
Howard Chu's avatar
Howard Chu committed
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
	MDB_env		*mt_env;		/**< the DB environment */
	/** The list of pages that became unused during this transaction.
	 *	This is an #IDL.
	 */
	pgno_t		*mt_free_pgs;
	union {
		ID2L	dirty_list;	/**< modified pages */
		MDB_reader	*reader;	/**< this thread's slot in the reader table */
	} 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;
	/**	Number of DB records in use. This number only ever increments;
	 *	we don't decrement it when individual DB handles are closed.
	 */
734
	MDB_dbi		mt_numdbs;
Howard Chu's avatar
Howard Chu committed
735

Howard Chu's avatar
Howard Chu committed
736
737
738
739
/** @defgroup mdb_txn	Transaction Flags
 *	@ingroup internal
 *	@{
 */
Howard Chu's avatar
Howard Chu committed
740
741
#define MDB_TXN_RDONLY		0x01		/**< read-only transaction */
#define MDB_TXN_ERROR		0x02		/**< an error has occurred */
Howard Chu's avatar
Howard Chu committed
742
743
/** @} */
	unsigned int	mt_flags;		/**< @ref mdb_txn */
Howard Chu's avatar
Howard Chu committed
744
745
746
747
748
	/** 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
749

Howard Chu's avatar
Howard Chu committed
750
/** Enough space for 2^32 nodes with minimum of 2 keys per node. I.e., plenty.
751
752
753
 * 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
754
#define CURSOR_STACK		 32
Howard Chu's avatar
Howard Chu committed
755

Howard Chu's avatar
Howard Chu committed
756
struct MDB_xcursor;
757

Howard Chu's avatar
Howard Chu committed
758
	/** Cursors are used for all DB operations */
Howard Chu's avatar
Howard Chu committed
759
struct MDB_cursor {
Howard Chu's avatar
Howard Chu committed
760
	/** Context used for databases with #MDB_DUPSORT, otherwise NULL */
Howard Chu's avatar
Howard Chu committed
761
	struct MDB_xcursor	*mc_xcursor;
Howard Chu's avatar
Howard Chu committed
762
	/** The transaction that owns this cursor */
Howard Chu's avatar
Howard Chu committed
763
	MDB_txn		*mc_txn;
Howard Chu's avatar
Howard Chu committed
764
	/** The database handle this cursor operates on */
Howard Chu's avatar
Howard Chu committed
765
	MDB_dbi		mc_dbi;
766
767
768
769
	/** 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
770
771
	unsigned short 	mc_snum;	/**< number of pushed pages */
	unsigned short	mc_top;		/**< index of top page, mc_snum-1 */
Howard Chu's avatar
Howard Chu committed
772
773
774
775
776
/** @defgroup mdb_cursor	Cursor Flags
 *	@ingroup internal
 *	Cursor state flags.
 *	@{
 */
Howard Chu's avatar
Howard Chu committed
777
778
#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
779
780
/** @} */
	unsigned int	mc_flags;	/**< @ref mdb_cursor */
Howard Chu's avatar
Howard Chu committed
781
782
	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
783
784
};

Howard Chu's avatar
Howard Chu committed
785
786
787
788
	/** 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.
789
	 */
Howard Chu's avatar
Howard Chu committed
790
typedef struct MDB_xcursor {
Howard Chu's avatar
Howard Chu committed
791
	/** A sub-cursor for traversing the Dup DB */
Howard Chu's avatar
Howard Chu committed
792
	MDB_cursor mx_cursor;
793
794
795
796
	/** 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
797
798
} MDB_xcursor;

Howard Chu's avatar
Howard Chu committed
799
800
801
802
803
804
805
	/** A set of pages freed by an earlier transaction. */
typedef struct MDB_oldpages {
	/** Usually we only read one record from the FREEDB at a time, but
	 *	in case we read more, this will chain them together.
	 */
	struct MDB_oldpages *mo_next;
	/**	The ID of the transaction in which these pages were freed. */
806
	txnid_t		mo_txnid;
Howard Chu's avatar
Howard Chu committed
807
808
809
810
811
	/** An #IDL of the pages */
	pgno_t		mo_pages[1];	/* dynamic */
} MDB_oldpages;

	/** The database environment. */
Howard Chu's avatar
Howard Chu committed
812
struct MDB_env {
Howard Chu's avatar
Howard Chu committed
813
814
815
	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
816
	/** Failed to update the meta page. Probably an I/O error. */
Howard Chu's avatar
Howard Chu committed
817
#define	MDB_FATAL_ERROR	0x80000000U
Howard Chu's avatar
Howard Chu committed
818
	uint32_t 	me_flags;		/**< @ref mdb_env */
Howard Chu's avatar
Howard Chu committed
819
820
	uint32_t	me_extrapad;	/**< unused for now */
	unsigned int	me_maxreaders;	/**< size of the reader table */
821
822
	MDB_dbi		me_numdbs;		/**< number of DBs opened */
	MDB_dbi		me_maxdbs;		/**< size of the DB table */
Howard Chu's avatar
Howard Chu committed
823
824
825
826
827
828
829
830
	char		*me_path;		/**< path to the DB files */
	char		*me_map;		/**< the memory map of the data file */
	MDB_txninfo	*me_txns;		/**< the memory map of the lock file */
	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 */
Hallvard Furuseth's avatar
Hallvard Furuseth committed
831
	unsigned int	me_psize;	/**< size of a page, from #GET_PAGESIZE */
Howard Chu's avatar
Howard Chu committed
832
833
834
835
836
837
838
	unsigned int	me_db_toggle;	/**< which DB table is current */
	MDB_dbx		*me_dbxs;		/**< array of static DB info */
	MDB_db		*me_dbs[2];		/**< two arrays of MDB_db info */
	MDB_oldpages *me_pghead;	/**< list of old page records */
	pthread_key_t	me_txkey;	/**< thread-key for readers */
	MDB_page	*me_dpages;		/**< list of malloc'd blocks for re-use */
	/** IDL of pages that became unused in a write txn */
839
	pgno_t		me_free_pgs[MDB_IDL_UM_SIZE];
Howard Chu's avatar
Howard Chu committed
840
	/** ID2L of pages that were written during a write txn */
Howard Chu's avatar
Howard Chu committed
841
	ID2			me_dirty_list[MDB_IDL_UM_SIZE];
Howard Chu's avatar
Howard Chu committed
842
	/** rwlock for the DB tables, if #LAZY_LOCKS is false */
843
	LAZY_RWLOCK_DEF(me_dblock)
Howard Chu's avatar
Howard Chu committed
844
845
846
847
#ifdef _WIN32
	HANDLE		me_rmutex;		/* Windows mutexes don't reside in shared mem */
	HANDLE		me_wmutex;
#endif
Howard Chu's avatar
Howard Chu committed
848
849
850
851
#ifdef __APPLE__
	sem_t		*me_rmutex;		/* Apple doesn't support shared mutexes */
	sem_t		*me_wmutex;
#endif
Howard Chu's avatar
Howard Chu committed
852
};
Howard Chu's avatar
Howard Chu committed
853
854
	/** max number of pages to commit in one writev() call */
#define MDB_COMMIT_PAGES	 64
Howard Chu's avatar
Howard Chu committed
855

Howard Chu's avatar
Howard Chu committed
856
static MDB_page *mdb_page_alloc(MDB_cursor *mc, int num);
Howard Chu's avatar
Howard Chu committed
857
static MDB_page *mdb_page_new(MDB_cursor *mc, uint32_t flags, int num);
Howard Chu's avatar
Howard Chu committed
858
static int 		mdb_page_touch(MDB_cursor *mc);
Howard Chu's avatar
Howard Chu committed
859

Howard Chu's avatar
Howard Chu committed
860
static int  mdb_page_get(MDB_txn *txn, pgno_t pgno, MDB_page **mp);
Howard Chu's avatar
Howard Chu committed
861
static int  mdb_page_search_root(MDB_cursor *mc,
862
			    MDB_val *key, int modify);
Howard Chu's avatar
Howard Chu committed
863
static int  mdb_page_search(MDB_cursor *mc,
864
			    MDB_val *key, int modify);
Howard Chu's avatar
Howard Chu committed
865
866
867
static int	mdb_page_merge(MDB_cursor *csrc, MDB_cursor *cdst);
static int	mdb_page_split(MDB_cursor *mc, MDB_val *newkey, MDB_val *newdata,
				pgno_t newpgno);
Howard Chu's avatar
Howard Chu committed
868

Howard Chu's avatar
Howard Chu committed
869
870
871
static int  mdb_env_read_header(MDB_env *env, MDB_meta *meta);
static int  mdb_env_read_meta(MDB_env *env, int *which);
static int  mdb_env_write_meta(MDB_txn *txn);
Howard Chu's avatar
Howard Chu committed
872

Howard Chu's avatar
Howard Chu committed
873
874
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,
875
			    MDB_val *key, MDB_val *data, pgno_t pgno, uint8_t flags);
Howard Chu's avatar
Howard Chu committed
876
static void mdb_node_del(MDB_page *mp, indx_t indx, int ksize);
Howard Chu's avatar
Howard Chu committed
877
static void mdb_node_shrink(MDB_page *mp, indx_t indx);
Howard Chu's avatar
Howard Chu committed
878
static int	mdb_node_move(MDB_cursor *csrc, MDB_cursor *cdst);
Howard Chu's avatar
Howard Chu committed
879
static int  mdb_node_read(MDB_txn *txn, MDB_node *leaf, MDB_val *data);
Howard Chu's avatar
Howard Chu committed
880
881
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
882

883
static int	mdb_rebalance(MDB_cursor *mc);
Howard Chu's avatar
Howard Chu committed
884
static int	mdb_update_key(MDB_page *mp, indx_t indx, MDB_val *key);
885

Howard Chu's avatar
Howard Chu committed
886
887
static void	mdb_cursor_pop(MDB_cursor *mc);
static int	mdb_cursor_push(MDB_cursor *mc, MDB_page *mp);
888

Howard Chu's avatar
Howard Chu committed
889
static int	mdb_cursor_del0(MDB_cursor *mc, MDB_node *leaf);
Howard Chu's avatar
Howard Chu committed
890
static int	mdb_cursor_sibling(MDB_cursor *mc, int move_right);
891
892
893
894
895
896
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
897

Howard Chu's avatar
Howard Chu committed
898
static void	mdb_cursor_init(MDB_cursor *mc, MDB_txn *txn, MDB_dbi dbi, MDB_xcursor *mx);
Howard Chu's avatar
Howard Chu committed
899
static void	mdb_xcursor_init0(MDB_cursor *mc);
900
static void	mdb_xcursor_init1(MDB_cursor *mc, MDB_node *node);
Howard Chu's avatar
Howard Chu committed
901

Howard Chu's avatar
Howard Chu committed
902
903
static void mdb_default_cmp(MDB_txn *txn, MDB_dbi dbi);

Howard Chu's avatar
Howard Chu committed
904
/** @cond */
Howard Chu's avatar
Howard Chu committed
905
static MDB_cmp_func	mdb_cmp_memn, mdb_cmp_memnr, mdb_cmp_int, mdb_cmp_cint, mdb_cmp_long;
Howard Chu's avatar
Howard Chu committed
906
/** @endcond */
Howard Chu's avatar
Howard Chu committed
907

Howard Chu's avatar
Howard Chu committed
908
909
910
911
912
913
#ifdef _WIN32
static SECURITY_DESCRIPTOR mdb_null_sd;
static SECURITY_ATTRIBUTES mdb_all_sa;
static int mdb_sec_inited;
#endif

Howard Chu's avatar
Howard Chu committed
914
/** Return the library version info. */
Howard Chu's avatar
Howard Chu committed
915
char *
Howard Chu's avatar
Howard Chu committed
916
mdb_version(int *major, int *minor, int *patch)
Howard Chu's avatar
Howard Chu committed
917
{
Howard Chu's avatar
Howard Chu committed
918
919
920
	if (major) *major = MDB_VERSION_MAJOR;
	if (minor) *minor = MDB_VERSION_MINOR;
	if (patch) *patch = MDB_VERSION_PATCH;
Howard Chu's avatar
Howard Chu committed
921
922
923
	return MDB_VERSION_STRING;
}

Howard Chu's avatar
Howard Chu committed
924
/** Table of descriptions for MDB @ref errors */
Howard Chu's avatar
Howard Chu committed
925
static char *const mdb_errstr[] = {
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
	"MDB_KEYEXIST: Key/data pair already exists",
	"MDB_NOTFOUND: No matching key/data pair found",
	"MDB_PAGE_NOTFOUND: Requested page not found",
	"MDB_CORRUPTED: Located page was wrong type",
	"MDB_PANIC: Update of meta page failed",
	"MDB_VERSION_MISMATCH: Database environment version mismatch"
};

char *
mdb_strerror(int err)
{
	if (!err)
		return ("Successful return: 0");

	if (err >= MDB_KEYEXIST && err <= MDB_VERSION_MISMATCH)
Howard Chu's avatar
Howard Chu committed
941
		return mdb_errstr[err - MDB_KEYEXIST];
942
943
944
945

	return strerror(err);
}

946
#if DEBUG
Howard Chu's avatar
Howard Chu committed
947
948
949
950
951
/** Display a key in hexadecimal and return the address of the result.
 * @param[in] key the key to display
 * @param[in] buf the buffer to write into. Should always be #DKBUF.
 * @return The key in hexadecimal form.
 */
952
char *
Howard Chu's avatar
Howard Chu committed
953
954
955
956
957
958
959
mdb_dkey(MDB_val *key, char *buf)
{
	char *ptr = buf;
	unsigned char *c = key->mv_data;
	unsigned int i;
	if (key->mv_size > MAXKEYSIZE)
		return "MAXKEYSIZE";
Howard Chu's avatar
Howard Chu committed
960
961
962
	/* may want to make this a dynamic check: if the key is mostly
	 * printable characters, print it as-is instead of converting to hex.
	 */
963
#if 1
Howard Chu's avatar
Howard Chu committed
964
965
	for (i=0; i<key->mv_size; i++)
		ptr += sprintf(ptr, "%02x", *c++);
Howard Chu's avatar
Howard Chu committed
966
967
968
#else
	sprintf(buf, "%.*s", key->mv_size, key->mv_data);
#endif
Howard Chu's avatar
Howard Chu committed
969
970
	return buf;
}
971
#endif
Howard Chu's avatar
Howard Chu committed
972

Howard Chu's avatar
Howard Chu committed
973
int
Howard Chu's avatar
Howard Chu committed
974
mdb_cmp(MDB_txn *txn, MDB_dbi dbi, const MDB_val *a, const MDB_val *b)
Howard Chu's avatar
Howard Chu committed
975
{
Howard Chu's avatar
Howard Chu committed
976
	return txn->mt_dbxs[dbi].md_cmp(a, b);
Howard Chu's avatar
Howard Chu committed
977
978
979
980
981
982
983
}

int
mdb_dcmp(MDB_txn *txn, MDB_dbi dbi, const MDB_val *a, const MDB_val *b)
{
	if (txn->mt_dbxs[dbi].md_dcmp)
		return txn->mt_dbxs[dbi].md_dcmp(a, b);
Howard Chu's avatar
Howard Chu committed
984
	else
Howard Chu's avatar
Howard Chu committed
985
		return EINVAL;	/* too bad you can't distinguish this from a valid result */
Howard Chu's avatar
Howard Chu committed
986
987
}

Howard Chu's avatar
Howard Chu committed
988
989
990
991
992
993
994
995
996
/** Allocate pages for writing.
 * If there are free pages available from older transactions, they
 * will be re-used first. Otherwise a new page will be allocated.
 * @param[in] mc cursor A cursor handle identifying the transaction and
 *	database for which we are allocating.
 * @param[in] num the number of pages to allocate.
 * @return Address of the allocated page(s). Requests for multiple pages
 *  will always be satisfied by a single contiguous chunk of memory.
 */
997
static MDB_page *
Howard Chu's avatar
Howard Chu committed
998
mdb_page_alloc(MDB_cursor *mc, int num)
Howard Chu's avatar
Howard Chu committed
999
{
1000
1001
	MDB_txn *txn = mc->mc_txn;
	MDB_page *np;
Howard Chu's avatar
Howard Chu committed
1002
	pgno_t pgno = P_INVALID;
1003
	ID2 mid;
Howard Chu's avatar
Howard Chu committed
1004

Howard Chu's avatar
Howard Chu committed
1005
1006
	if (txn->mt_txnid > 2) {

1007
		if (!txn->mt_env->me_pghead && mc->mc_dbi != FREE_DBI &&
Howard Chu's avatar
Howard Chu committed
1008
1009
			txn->mt_dbs[FREE_DBI].md_root != P_INVALID) {
			/* See if there's anything in the free DB */
1010
			MDB_cursor m2;
Howard Chu's avatar
Howard Chu committed
1011
			MDB_node *leaf;
1012
			txnid_t *kptr, oldest;
Howard Chu's avatar
Howard Chu committed
1013

Howard Chu's avatar
Howard Chu committed
1014
			mdb_cursor_init(&m2, txn, FREE_DBI, NULL);
Howard Chu's avatar
Howard Chu committed
1015
			mdb_page_search(&m2, NULL, 0);
1016
			leaf = NODEPTR(m2.mc_pg[m2.mc_top], 0);
1017
			kptr = (txnid_t *)NODEKEY(leaf);
Howard Chu's avatar
Howard Chu committed
1018

Howard Chu's avatar
Howard Chu committed
1019
1020
			{
				unsigned int i;
Howard Chu's avatar
Howard Chu committed
1021
1022
				oldest = txn->mt_txnid - 1;
				for (i=0; i<txn->mt_env->me_txns->mti_numreaders; i++) {
1023
					txnid_t mr = txn->mt_env->me_txns->mti_readers[i].mr_txnid;
Howard Chu's avatar
Howard Chu committed
1024
1025
					if (mr && mr < oldest)
						oldest = mr;
Howard Chu's avatar
Howard Chu committed
1026
1027
				}
			}
Howard Chu's avatar
Howard Chu committed
1028
1029
1030
1031
1032
1033
1034
1035

			if (oldest > *kptr) {
				/* It's usable, grab it.
				 */
				MDB_oldpages *mop;
				MDB_val data;
				pgno_t *idl;

Howard Chu's avatar
Howard Chu committed
1036
				mdb_node_read(txn, leaf, &data);
1037
				idl = (ID *) data.mv_data;
Howard Chu's avatar
Howard Chu committed
1038
1039
1040
1041
1042
1043
1044
1045
1046
				mop = malloc(sizeof(MDB_oldpages) + MDB_IDL_SIZEOF(idl) - sizeof(pgno_t));
				mop->mo_next = txn->mt_env->me_pghead;
				mop->mo_txnid = *kptr;
				txn->mt_env->me_pghead = mop;
				memcpy(mop->mo_pages, idl, MDB_IDL_SIZEOF(idl));

#if DEBUG > 1
				{
					unsigned int i;
1047
					DPRINTF("IDL read txn %zu root %zu num %zu",
Howard Chu's avatar
Howard Chu committed
1048
1049
						mop->mo_txnid, txn->mt_dbs[FREE_DBI].md_root, idl[0]);
					for (i=0; i<idl[0]; i++) {
1050
						DPRINTF("IDL %zu", idl[i+1]);
Howard Chu's avatar
Howard Chu committed
1051
1052
					}
				}
Howard Chu's avatar
Howard Chu committed
1053
#endif
Howard Chu's avatar
Howard Chu committed
1054
				/* drop this IDL from the DB */
1055
1056
1057
				m2.mc_ki[m2.mc_top] = 0;
				m2.mc_flags = C_INITIALIZED;
				mdb_cursor_del(&m2, 0);
Howard Chu's avatar
Howard Chu committed
1058
			}
Howard Chu's avatar
Howard Chu committed
1059
		}
Howard Chu's avatar
Howard Chu committed
1060
		if (txn->mt_env->me_pghead) {
Howard Chu's avatar
Howard Chu committed
1061
1062
			MDB_oldpages *mop = txn->mt_env->me_pghead;
			if (num > 1) {
1063
1064
1065
1066
				/* FIXME: For now, always use fresh pages. We
				 * really ought to search the free list for a
				 * contiguous range.
				 */
Howard Chu's avatar
Howard Chu committed
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
				;
			} else {
				/* peel pages off tail, so we only have to truncate the list */
				pgno = MDB_IDL_LAST(mop->mo_pages);
				if (MDB_IDL_IS_RANGE(mop->mo_pages)) {
					mop->mo_pages[2]++;
					if (mop->mo_pages[2] > mop->mo_pages[1])
						mop->mo_pages[0] = 0;
				} else {
					mop->mo_pages[0]--;
				}
				if (MDB_IDL_IS_ZERO(mop->mo_pages)) {
					txn->mt_env->me_pghead = mop->mo_next;
					free(mop);
				}
			}
		}
	}
Howard Chu's avatar
Howard Chu committed
1085

Howard Chu's avatar
Howard Chu committed
1086
1087
	if (pgno == P_INVALID) {
		/* DB size is maxed out */
1088
1089
		if (txn->mt_next_pgno + num >= txn->mt_env->me_maxpg) {
			assert(txn->mt_next_pgno + num < txn->mt_env->me_maxpg);
Howard Chu's avatar
Howard Chu committed
1090
			return NULL;
1091
		}
Howard Chu's avatar
Howard Chu committed
1092
	}
1093
	if (txn->mt_env->me_dpages && num == 1) {
1094
1095
		np = txn->mt_env->me_dpages;
		txn->mt_env->me_dpages = np->mp_next;
1096
	} else {
1097
		if ((np = malloc(txn->mt_env->me_psize * num )) == NULL)
1098
1099
			return NULL;
	}
Howard Chu's avatar
Howard Chu committed
1100
	if (pgno == P_INVALID) {
1101
		np->mp_pgno = txn->mt_next_pgno;
Howard Chu's avatar
Howard Chu committed
1102
1103
		txn->mt_next_pgno += num;
	} else {
1104
		np->mp_pgno = pgno;
Howard Chu's avatar
Howard Chu committed
1105