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[chromium-blink-merge.git] / third_party / sqlite / sqlite-src-3080704 / src / mem3.c
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1 /*
2 ** 2007 October 14
3 **
4 ** The author disclaims copyright to this source code. In place of
5 ** a legal notice, here is a blessing:
6 **
7 ** May you do good and not evil.
8 ** May you find forgiveness for yourself and forgive others.
9 ** May you share freely, never taking more than you give.
11 *************************************************************************
12 ** This file contains the C functions that implement a memory
13 ** allocation subsystem for use by SQLite.
15 ** This version of the memory allocation subsystem omits all
16 ** use of malloc(). The SQLite user supplies a block of memory
17 ** before calling sqlite3_initialize() from which allocations
18 ** are made and returned by the xMalloc() and xRealloc()
19 ** implementations. Once sqlite3_initialize() has been called,
20 ** the amount of memory available to SQLite is fixed and cannot
21 ** be changed.
23 ** This version of the memory allocation subsystem is included
24 ** in the build only if SQLITE_ENABLE_MEMSYS3 is defined.
26 #include "sqliteInt.h"
29 ** This version of the memory allocator is only built into the library
30 ** SQLITE_ENABLE_MEMSYS3 is defined. Defining this symbol does not
31 ** mean that the library will use a memory-pool by default, just that
32 ** it is available. The mempool allocator is activated by calling
33 ** sqlite3_config().
35 #ifdef SQLITE_ENABLE_MEMSYS3
38 ** Maximum size (in Mem3Blocks) of a "small" chunk.
40 #define MX_SMALL 10
44 ** Number of freelist hash slots
46 #define N_HASH 61
49 ** A memory allocation (also called a "chunk") consists of two or
50 ** more blocks where each block is 8 bytes. The first 8 bytes are
51 ** a header that is not returned to the user.
53 ** A chunk is two or more blocks that is either checked out or
54 ** free. The first block has format u.hdr. u.hdr.size4x is 4 times the
55 ** size of the allocation in blocks if the allocation is free.
56 ** The u.hdr.size4x&1 bit is true if the chunk is checked out and
57 ** false if the chunk is on the freelist. The u.hdr.size4x&2 bit
58 ** is true if the previous chunk is checked out and false if the
59 ** previous chunk is free. The u.hdr.prevSize field is the size of
60 ** the previous chunk in blocks if the previous chunk is on the
61 ** freelist. If the previous chunk is checked out, then
62 ** u.hdr.prevSize can be part of the data for that chunk and should
63 ** not be read or written.
65 ** We often identify a chunk by its index in mem3.aPool[]. When
66 ** this is done, the chunk index refers to the second block of
67 ** the chunk. In this way, the first chunk has an index of 1.
68 ** A chunk index of 0 means "no such chunk" and is the equivalent
69 ** of a NULL pointer.
71 ** The second block of free chunks is of the form u.list. The
72 ** two fields form a double-linked list of chunks of related sizes.
73 ** Pointers to the head of the list are stored in mem3.aiSmall[]
74 ** for smaller chunks and mem3.aiHash[] for larger chunks.
76 ** The second block of a chunk is user data if the chunk is checked
77 ** out. If a chunk is checked out, the user data may extend into
78 ** the u.hdr.prevSize value of the following chunk.
80 typedef struct Mem3Block Mem3Block;
81 struct Mem3Block {
82 union {
83 struct {
84 u32 prevSize; /* Size of previous chunk in Mem3Block elements */
85 u32 size4x; /* 4x the size of current chunk in Mem3Block elements */
86 } hdr;
87 struct {
88 u32 next; /* Index in mem3.aPool[] of next free chunk */
89 u32 prev; /* Index in mem3.aPool[] of previous free chunk */
90 } list;
91 } u;
95 ** All of the static variables used by this module are collected
96 ** into a single structure named "mem3". This is to keep the
97 ** static variables organized and to reduce namespace pollution
98 ** when this module is combined with other in the amalgamation.
100 static SQLITE_WSD struct Mem3Global {
102 ** Memory available for allocation. nPool is the size of the array
103 ** (in Mem3Blocks) pointed to by aPool less 2.
105 u32 nPool;
106 Mem3Block *aPool;
109 ** True if we are evaluating an out-of-memory callback.
111 int alarmBusy;
114 ** Mutex to control access to the memory allocation subsystem.
116 sqlite3_mutex *mutex;
119 ** The minimum amount of free space that we have seen.
121 u32 mnMaster;
124 ** iMaster is the index of the master chunk. Most new allocations
125 ** occur off of this chunk. szMaster is the size (in Mem3Blocks)
126 ** of the current master. iMaster is 0 if there is not master chunk.
127 ** The master chunk is not in either the aiHash[] or aiSmall[].
129 u32 iMaster;
130 u32 szMaster;
133 ** Array of lists of free blocks according to the block size
134 ** for smaller chunks, or a hash on the block size for larger
135 ** chunks.
137 u32 aiSmall[MX_SMALL-1]; /* For sizes 2 through MX_SMALL, inclusive */
138 u32 aiHash[N_HASH]; /* For sizes MX_SMALL+1 and larger */
139 } mem3 = { 97535575 };
141 #define mem3 GLOBAL(struct Mem3Global, mem3)
144 ** Unlink the chunk at mem3.aPool[i] from list it is currently
145 ** on. *pRoot is the list that i is a member of.
147 static void memsys3UnlinkFromList(u32 i, u32 *pRoot){
148 u32 next = mem3.aPool[i].u.list.next;
149 u32 prev = mem3.aPool[i].u.list.prev;
150 assert( sqlite3_mutex_held(mem3.mutex) );
151 if( prev==0 ){
152 *pRoot = next;
153 }else{
154 mem3.aPool[prev].u.list.next = next;
156 if( next ){
157 mem3.aPool[next].u.list.prev = prev;
159 mem3.aPool[i].u.list.next = 0;
160 mem3.aPool[i].u.list.prev = 0;
164 ** Unlink the chunk at index i from
165 ** whatever list is currently a member of.
167 static void memsys3Unlink(u32 i){
168 u32 size, hash;
169 assert( sqlite3_mutex_held(mem3.mutex) );
170 assert( (mem3.aPool[i-1].u.hdr.size4x & 1)==0 );
171 assert( i>=1 );
172 size = mem3.aPool[i-1].u.hdr.size4x/4;
173 assert( size==mem3.aPool[i+size-1].u.hdr.prevSize );
174 assert( size>=2 );
175 if( size <= MX_SMALL ){
176 memsys3UnlinkFromList(i, &mem3.aiSmall[size-2]);
177 }else{
178 hash = size % N_HASH;
179 memsys3UnlinkFromList(i, &mem3.aiHash[hash]);
184 ** Link the chunk at mem3.aPool[i] so that is on the list rooted
185 ** at *pRoot.
187 static void memsys3LinkIntoList(u32 i, u32 *pRoot){
188 assert( sqlite3_mutex_held(mem3.mutex) );
189 mem3.aPool[i].u.list.next = *pRoot;
190 mem3.aPool[i].u.list.prev = 0;
191 if( *pRoot ){
192 mem3.aPool[*pRoot].u.list.prev = i;
194 *pRoot = i;
198 ** Link the chunk at index i into either the appropriate
199 ** small chunk list, or into the large chunk hash table.
201 static void memsys3Link(u32 i){
202 u32 size, hash;
203 assert( sqlite3_mutex_held(mem3.mutex) );
204 assert( i>=1 );
205 assert( (mem3.aPool[i-1].u.hdr.size4x & 1)==0 );
206 size = mem3.aPool[i-1].u.hdr.size4x/4;
207 assert( size==mem3.aPool[i+size-1].u.hdr.prevSize );
208 assert( size>=2 );
209 if( size <= MX_SMALL ){
210 memsys3LinkIntoList(i, &mem3.aiSmall[size-2]);
211 }else{
212 hash = size % N_HASH;
213 memsys3LinkIntoList(i, &mem3.aiHash[hash]);
218 ** If the STATIC_MEM mutex is not already held, obtain it now. The mutex
219 ** will already be held (obtained by code in malloc.c) if
220 ** sqlite3GlobalConfig.bMemStat is true.
222 static void memsys3Enter(void){
223 if( sqlite3GlobalConfig.bMemstat==0 && mem3.mutex==0 ){
224 mem3.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM);
226 sqlite3_mutex_enter(mem3.mutex);
228 static void memsys3Leave(void){
229 sqlite3_mutex_leave(mem3.mutex);
233 ** Called when we are unable to satisfy an allocation of nBytes.
235 static void memsys3OutOfMemory(int nByte){
236 if( !mem3.alarmBusy ){
237 mem3.alarmBusy = 1;
238 assert( sqlite3_mutex_held(mem3.mutex) );
239 sqlite3_mutex_leave(mem3.mutex);
240 sqlite3_release_memory(nByte);
241 sqlite3_mutex_enter(mem3.mutex);
242 mem3.alarmBusy = 0;
248 ** Chunk i is a free chunk that has been unlinked. Adjust its
249 ** size parameters for check-out and return a pointer to the
250 ** user portion of the chunk.
252 static void *memsys3Checkout(u32 i, u32 nBlock){
253 u32 x;
254 assert( sqlite3_mutex_held(mem3.mutex) );
255 assert( i>=1 );
256 assert( mem3.aPool[i-1].u.hdr.size4x/4==nBlock );
257 assert( mem3.aPool[i+nBlock-1].u.hdr.prevSize==nBlock );
258 x = mem3.aPool[i-1].u.hdr.size4x;
259 mem3.aPool[i-1].u.hdr.size4x = nBlock*4 | 1 | (x&2);
260 mem3.aPool[i+nBlock-1].u.hdr.prevSize = nBlock;
261 mem3.aPool[i+nBlock-1].u.hdr.size4x |= 2;
262 return &mem3.aPool[i];
266 ** Carve a piece off of the end of the mem3.iMaster free chunk.
267 ** Return a pointer to the new allocation. Or, if the master chunk
268 ** is not large enough, return 0.
270 static void *memsys3FromMaster(u32 nBlock){
271 assert( sqlite3_mutex_held(mem3.mutex) );
272 assert( mem3.szMaster>=nBlock );
273 if( nBlock>=mem3.szMaster-1 ){
274 /* Use the entire master */
275 void *p = memsys3Checkout(mem3.iMaster, mem3.szMaster);
276 mem3.iMaster = 0;
277 mem3.szMaster = 0;
278 mem3.mnMaster = 0;
279 return p;
280 }else{
281 /* Split the master block. Return the tail. */
282 u32 newi, x;
283 newi = mem3.iMaster + mem3.szMaster - nBlock;
284 assert( newi > mem3.iMaster+1 );
285 mem3.aPool[mem3.iMaster+mem3.szMaster-1].u.hdr.prevSize = nBlock;
286 mem3.aPool[mem3.iMaster+mem3.szMaster-1].u.hdr.size4x |= 2;
287 mem3.aPool[newi-1].u.hdr.size4x = nBlock*4 + 1;
288 mem3.szMaster -= nBlock;
289 mem3.aPool[newi-1].u.hdr.prevSize = mem3.szMaster;
290 x = mem3.aPool[mem3.iMaster-1].u.hdr.size4x & 2;
291 mem3.aPool[mem3.iMaster-1].u.hdr.size4x = mem3.szMaster*4 | x;
292 if( mem3.szMaster < mem3.mnMaster ){
293 mem3.mnMaster = mem3.szMaster;
295 return (void*)&mem3.aPool[newi];
300 ** *pRoot is the head of a list of free chunks of the same size
301 ** or same size hash. In other words, *pRoot is an entry in either
302 ** mem3.aiSmall[] or mem3.aiHash[].
304 ** This routine examines all entries on the given list and tries
305 ** to coalesce each entries with adjacent free chunks.
307 ** If it sees a chunk that is larger than mem3.iMaster, it replaces
308 ** the current mem3.iMaster with the new larger chunk. In order for
309 ** this mem3.iMaster replacement to work, the master chunk must be
310 ** linked into the hash tables. That is not the normal state of
311 ** affairs, of course. The calling routine must link the master
312 ** chunk before invoking this routine, then must unlink the (possibly
313 ** changed) master chunk once this routine has finished.
315 static void memsys3Merge(u32 *pRoot){
316 u32 iNext, prev, size, i, x;
318 assert( sqlite3_mutex_held(mem3.mutex) );
319 for(i=*pRoot; i>0; i=iNext){
320 iNext = mem3.aPool[i].u.list.next;
321 size = mem3.aPool[i-1].u.hdr.size4x;
322 assert( (size&1)==0 );
323 if( (size&2)==0 ){
324 memsys3UnlinkFromList(i, pRoot);
325 assert( i > mem3.aPool[i-1].u.hdr.prevSize );
326 prev = i - mem3.aPool[i-1].u.hdr.prevSize;
327 if( prev==iNext ){
328 iNext = mem3.aPool[prev].u.list.next;
330 memsys3Unlink(prev);
331 size = i + size/4 - prev;
332 x = mem3.aPool[prev-1].u.hdr.size4x & 2;
333 mem3.aPool[prev-1].u.hdr.size4x = size*4 | x;
334 mem3.aPool[prev+size-1].u.hdr.prevSize = size;
335 memsys3Link(prev);
336 i = prev;
337 }else{
338 size /= 4;
340 if( size>mem3.szMaster ){
341 mem3.iMaster = i;
342 mem3.szMaster = size;
348 ** Return a block of memory of at least nBytes in size.
349 ** Return NULL if unable.
351 ** This function assumes that the necessary mutexes, if any, are
352 ** already held by the caller. Hence "Unsafe".
354 static void *memsys3MallocUnsafe(int nByte){
355 u32 i;
356 u32 nBlock;
357 u32 toFree;
359 assert( sqlite3_mutex_held(mem3.mutex) );
360 assert( sizeof(Mem3Block)==8 );
361 if( nByte<=12 ){
362 nBlock = 2;
363 }else{
364 nBlock = (nByte + 11)/8;
366 assert( nBlock>=2 );
368 /* STEP 1:
369 ** Look for an entry of the correct size in either the small
370 ** chunk table or in the large chunk hash table. This is
371 ** successful most of the time (about 9 times out of 10).
373 if( nBlock <= MX_SMALL ){
374 i = mem3.aiSmall[nBlock-2];
375 if( i>0 ){
376 memsys3UnlinkFromList(i, &mem3.aiSmall[nBlock-2]);
377 return memsys3Checkout(i, nBlock);
379 }else{
380 int hash = nBlock % N_HASH;
381 for(i=mem3.aiHash[hash]; i>0; i=mem3.aPool[i].u.list.next){
382 if( mem3.aPool[i-1].u.hdr.size4x/4==nBlock ){
383 memsys3UnlinkFromList(i, &mem3.aiHash[hash]);
384 return memsys3Checkout(i, nBlock);
389 /* STEP 2:
390 ** Try to satisfy the allocation by carving a piece off of the end
391 ** of the master chunk. This step usually works if step 1 fails.
393 if( mem3.szMaster>=nBlock ){
394 return memsys3FromMaster(nBlock);
398 /* STEP 3:
399 ** Loop through the entire memory pool. Coalesce adjacent free
400 ** chunks. Recompute the master chunk as the largest free chunk.
401 ** Then try again to satisfy the allocation by carving a piece off
402 ** of the end of the master chunk. This step happens very
403 ** rarely (we hope!)
405 for(toFree=nBlock*16; toFree<(mem3.nPool*16); toFree *= 2){
406 memsys3OutOfMemory(toFree);
407 if( mem3.iMaster ){
408 memsys3Link(mem3.iMaster);
409 mem3.iMaster = 0;
410 mem3.szMaster = 0;
412 for(i=0; i<N_HASH; i++){
413 memsys3Merge(&mem3.aiHash[i]);
415 for(i=0; i<MX_SMALL-1; i++){
416 memsys3Merge(&mem3.aiSmall[i]);
418 if( mem3.szMaster ){
419 memsys3Unlink(mem3.iMaster);
420 if( mem3.szMaster>=nBlock ){
421 return memsys3FromMaster(nBlock);
426 /* If none of the above worked, then we fail. */
427 return 0;
431 ** Free an outstanding memory allocation.
433 ** This function assumes that the necessary mutexes, if any, are
434 ** already held by the caller. Hence "Unsafe".
436 static void memsys3FreeUnsafe(void *pOld){
437 Mem3Block *p = (Mem3Block*)pOld;
438 int i;
439 u32 size, x;
440 assert( sqlite3_mutex_held(mem3.mutex) );
441 assert( p>mem3.aPool && p<&mem3.aPool[mem3.nPool] );
442 i = p - mem3.aPool;
443 assert( (mem3.aPool[i-1].u.hdr.size4x&1)==1 );
444 size = mem3.aPool[i-1].u.hdr.size4x/4;
445 assert( i+size<=mem3.nPool+1 );
446 mem3.aPool[i-1].u.hdr.size4x &= ~1;
447 mem3.aPool[i+size-1].u.hdr.prevSize = size;
448 mem3.aPool[i+size-1].u.hdr.size4x &= ~2;
449 memsys3Link(i);
451 /* Try to expand the master using the newly freed chunk */
452 if( mem3.iMaster ){
453 while( (mem3.aPool[mem3.iMaster-1].u.hdr.size4x&2)==0 ){
454 size = mem3.aPool[mem3.iMaster-1].u.hdr.prevSize;
455 mem3.iMaster -= size;
456 mem3.szMaster += size;
457 memsys3Unlink(mem3.iMaster);
458 x = mem3.aPool[mem3.iMaster-1].u.hdr.size4x & 2;
459 mem3.aPool[mem3.iMaster-1].u.hdr.size4x = mem3.szMaster*4 | x;
460 mem3.aPool[mem3.iMaster+mem3.szMaster-1].u.hdr.prevSize = mem3.szMaster;
462 x = mem3.aPool[mem3.iMaster-1].u.hdr.size4x & 2;
463 while( (mem3.aPool[mem3.iMaster+mem3.szMaster-1].u.hdr.size4x&1)==0 ){
464 memsys3Unlink(mem3.iMaster+mem3.szMaster);
465 mem3.szMaster += mem3.aPool[mem3.iMaster+mem3.szMaster-1].u.hdr.size4x/4;
466 mem3.aPool[mem3.iMaster-1].u.hdr.size4x = mem3.szMaster*4 | x;
467 mem3.aPool[mem3.iMaster+mem3.szMaster-1].u.hdr.prevSize = mem3.szMaster;
473 ** Return the size of an outstanding allocation, in bytes. The
474 ** size returned omits the 8-byte header overhead. This only
475 ** works for chunks that are currently checked out.
477 static int memsys3Size(void *p){
478 Mem3Block *pBlock;
479 if( p==0 ) return 0;
480 pBlock = (Mem3Block*)p;
481 assert( (pBlock[-1].u.hdr.size4x&1)!=0 );
482 return (pBlock[-1].u.hdr.size4x&~3)*2 - 4;
486 ** Round up a request size to the next valid allocation size.
488 static int memsys3Roundup(int n){
489 if( n<=12 ){
490 return 12;
491 }else{
492 return ((n+11)&~7) - 4;
497 ** Allocate nBytes of memory.
499 static void *memsys3Malloc(int nBytes){
500 sqlite3_int64 *p;
501 assert( nBytes>0 ); /* malloc.c filters out 0 byte requests */
502 memsys3Enter();
503 p = memsys3MallocUnsafe(nBytes);
504 memsys3Leave();
505 return (void*)p;
509 ** Free memory.
511 static void memsys3Free(void *pPrior){
512 assert( pPrior );
513 memsys3Enter();
514 memsys3FreeUnsafe(pPrior);
515 memsys3Leave();
519 ** Change the size of an existing memory allocation
521 static void *memsys3Realloc(void *pPrior, int nBytes){
522 int nOld;
523 void *p;
524 if( pPrior==0 ){
525 return sqlite3_malloc(nBytes);
527 if( nBytes<=0 ){
528 sqlite3_free(pPrior);
529 return 0;
531 nOld = memsys3Size(pPrior);
532 if( nBytes<=nOld && nBytes>=nOld-128 ){
533 return pPrior;
535 memsys3Enter();
536 p = memsys3MallocUnsafe(nBytes);
537 if( p ){
538 if( nOld<nBytes ){
539 memcpy(p, pPrior, nOld);
540 }else{
541 memcpy(p, pPrior, nBytes);
543 memsys3FreeUnsafe(pPrior);
545 memsys3Leave();
546 return p;
550 ** Initialize this module.
552 static int memsys3Init(void *NotUsed){
553 UNUSED_PARAMETER(NotUsed);
554 if( !sqlite3GlobalConfig.pHeap ){
555 return SQLITE_ERROR;
558 /* Store a pointer to the memory block in global structure mem3. */
559 assert( sizeof(Mem3Block)==8 );
560 mem3.aPool = (Mem3Block *)sqlite3GlobalConfig.pHeap;
561 mem3.nPool = (sqlite3GlobalConfig.nHeap / sizeof(Mem3Block)) - 2;
563 /* Initialize the master block. */
564 mem3.szMaster = mem3.nPool;
565 mem3.mnMaster = mem3.szMaster;
566 mem3.iMaster = 1;
567 mem3.aPool[0].u.hdr.size4x = (mem3.szMaster<<2) + 2;
568 mem3.aPool[mem3.nPool].u.hdr.prevSize = mem3.nPool;
569 mem3.aPool[mem3.nPool].u.hdr.size4x = 1;
571 return SQLITE_OK;
575 ** Deinitialize this module.
577 static void memsys3Shutdown(void *NotUsed){
578 UNUSED_PARAMETER(NotUsed);
579 mem3.mutex = 0;
580 return;
586 ** Open the file indicated and write a log of all unfreed memory
587 ** allocations into that log.
589 void sqlite3Memsys3Dump(const char *zFilename){
590 #ifdef SQLITE_DEBUG
591 FILE *out;
592 u32 i, j;
593 u32 size;
594 if( zFilename==0 || zFilename[0]==0 ){
595 out = stdout;
596 }else{
597 out = fopen(zFilename, "w");
598 if( out==0 ){
599 fprintf(stderr, "** Unable to output memory debug output log: %s **\n",
600 zFilename);
601 return;
604 memsys3Enter();
605 fprintf(out, "CHUNKS:\n");
606 for(i=1; i<=mem3.nPool; i+=size/4){
607 size = mem3.aPool[i-1].u.hdr.size4x;
608 if( size/4<=1 ){
609 fprintf(out, "%p size error\n", &mem3.aPool[i]);
610 assert( 0 );
611 break;
613 if( (size&1)==0 && mem3.aPool[i+size/4-1].u.hdr.prevSize!=size/4 ){
614 fprintf(out, "%p tail size does not match\n", &mem3.aPool[i]);
615 assert( 0 );
616 break;
618 if( ((mem3.aPool[i+size/4-1].u.hdr.size4x&2)>>1)!=(size&1) ){
619 fprintf(out, "%p tail checkout bit is incorrect\n", &mem3.aPool[i]);
620 assert( 0 );
621 break;
623 if( size&1 ){
624 fprintf(out, "%p %6d bytes checked out\n", &mem3.aPool[i], (size/4)*8-8);
625 }else{
626 fprintf(out, "%p %6d bytes free%s\n", &mem3.aPool[i], (size/4)*8-8,
627 i==mem3.iMaster ? " **master**" : "");
630 for(i=0; i<MX_SMALL-1; i++){
631 if( mem3.aiSmall[i]==0 ) continue;
632 fprintf(out, "small(%2d):", i);
633 for(j = mem3.aiSmall[i]; j>0; j=mem3.aPool[j].u.list.next){
634 fprintf(out, " %p(%d)", &mem3.aPool[j],
635 (mem3.aPool[j-1].u.hdr.size4x/4)*8-8);
637 fprintf(out, "\n");
639 for(i=0; i<N_HASH; i++){
640 if( mem3.aiHash[i]==0 ) continue;
641 fprintf(out, "hash(%2d):", i);
642 for(j = mem3.aiHash[i]; j>0; j=mem3.aPool[j].u.list.next){
643 fprintf(out, " %p(%d)", &mem3.aPool[j],
644 (mem3.aPool[j-1].u.hdr.size4x/4)*8-8);
646 fprintf(out, "\n");
648 fprintf(out, "master=%d\n", mem3.iMaster);
649 fprintf(out, "nowUsed=%d\n", mem3.nPool*8 - mem3.szMaster*8);
650 fprintf(out, "mxUsed=%d\n", mem3.nPool*8 - mem3.mnMaster*8);
651 sqlite3_mutex_leave(mem3.mutex);
652 if( out==stdout ){
653 fflush(stdout);
654 }else{
655 fclose(out);
657 #else
658 UNUSED_PARAMETER(zFilename);
659 #endif
663 ** This routine is the only routine in this file with external
664 ** linkage.
666 ** Populate the low-level memory allocation function pointers in
667 ** sqlite3GlobalConfig.m with pointers to the routines in this file. The
668 ** arguments specify the block of memory to manage.
670 ** This routine is only called by sqlite3_config(), and therefore
671 ** is not required to be threadsafe (it is not).
673 const sqlite3_mem_methods *sqlite3MemGetMemsys3(void){
674 static const sqlite3_mem_methods mempoolMethods = {
675 memsys3Malloc,
676 memsys3Free,
677 memsys3Realloc,
678 memsys3Size,
679 memsys3Roundup,
680 memsys3Init,
681 memsys3Shutdown,
684 return &mempoolMethods;
687 #endif /* SQLITE_ENABLE_MEMSYS3 */