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.

    10 **

    11 *************************************************************************

    12 ** This file contains the C functions that implement a memory

    13 ** allocation subsystem for use by SQLite. 

    14 **

    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.

    22 **

    23 ** This version of the memory allocation subsystem is included

    24 ** in the build only if SQLITE_ENABLE_MEMSYS3 is defined.

    25 **

    26 ** $Id: mem3.c,v 1.20 2008/07/18 18:56:17 drh Exp $

    27 */

    28 #include "sqliteInt.h"

    29 

    30 /*

    31 ** This version of the memory allocator is only built into the library

    32 ** SQLITE_ENABLE_MEMSYS3 is defined. Defining this symbol does not

    33 ** mean that the library will use a memory-pool by default, just that

    34 ** it is available. The mempool allocator is activated by calling

    35 ** sqlite3_config().

    36 */

    37 #ifdef SQLITE_ENABLE_MEMSYS3

    38 

    39 /*

    40 ** Maximum size (in Mem3Blocks) of a "small" chunk.

    41 */

    42 #define MX_SMALL 10

    43 

    44 

    45 /*

    46 ** Number of freelist hash slots

    47 */

    48 #define N_HASH  61

    49 

    50 /*

    51 ** A memory allocation (also called a "chunk") consists of two or 

    52 ** more blocks where each block is 8 bytes.  The first 8 bytes are 

    53 ** a header that is not returned to the user.

    54 **

    55 ** A chunk is two or more blocks that is either checked out or

    56 ** free.  The first block has format u.hdr.  u.hdr.size4x is 4 times the

    57 ** size of the allocation in blocks if the allocation is free.

    58 ** The u.hdr.size4x&1 bit is true if the chunk is checked out and

    59 ** false if the chunk is on the freelist.  The u.hdr.size4x&2 bit

    60 ** is true if the previous chunk is checked out and false if the

    61 ** previous chunk is free.  The u.hdr.prevSize field is the size of

    62 ** the previous chunk in blocks if the previous chunk is on the

    63 ** freelist. If the previous chunk is checked out, then

    64 ** u.hdr.prevSize can be part of the data for that chunk and should

    65 ** not be read or written.

    66 **

    67 ** We often identify a chunk by its index in mem3.aPool[].  When

    68 ** this is done, the chunk index refers to the second block of

    69 ** the chunk.  In this way, the first chunk has an index of 1.

    70 ** A chunk index of 0 means "no such chunk" and is the equivalent

    71 ** of a NULL pointer.

    72 **

    73 ** The second block of free chunks is of the form u.list.  The

    74 ** two fields form a double-linked list of chunks of related sizes.

    75 ** Pointers to the head of the list are stored in mem3.aiSmall[] 

    76 ** for smaller chunks and mem3.aiHash[] for larger chunks.

    77 **

    78 ** The second block of a chunk is user data if the chunk is checked 

    79 ** out.  If a chunk is checked out, the user data may extend into

    80 ** the u.hdr.prevSize value of the following chunk.

    81 */

    82 typedef struct Mem3Block Mem3Block;

    83 struct Mem3Block {

    84   union {

    85     struct {

    86       u32 prevSize;   /* Size of previous chunk in Mem3Block elements */

    87       u32 size4x;     /* 4x the size of current chunk in Mem3Block elements */

    88     } hdr;

    89     struct {

    90       u32 next;       /* Index in mem3.aPool[] of next free chunk */

    91       u32 prev;       /* Index in mem3.aPool[] of previous free chunk */

    92     } list;

    93   } u;

    94 };

    95 

    96 /*

    97 ** All of the static variables used by this module are collected

    98 ** into a single structure named "mem3".  This is to keep the

    99 ** static variables organized and to reduce namespace pollution

   100 ** when this module is combined with other in the amalgamation.

   101 */

   102 static struct {

   103   /*

   104   ** True if we are evaluating an out-of-memory callback.

   105   */

   106   int alarmBusy;

   107   

   108   /*

   109   ** Mutex to control access to the memory allocation subsystem.

   110   */

   111   sqlite3_mutex *mutex;

   112   

   113   /*

   114   ** The minimum amount of free space that we have seen.

   115   */

   116   u32 mnMaster;

   117 

   118   /*

   119   ** iMaster is the index of the master chunk.  Most new allocations

   120   ** occur off of this chunk.  szMaster is the size (in Mem3Blocks)

   121   ** of the current master.  iMaster is 0 if there is not master chunk.

   122   ** The master chunk is not in either the aiHash[] or aiSmall[].

   123   */

   124   u32 iMaster;

   125   u32 szMaster;

   126 

   127   /*

   128   ** Array of lists of free blocks according to the block size 

   129   ** for smaller chunks, or a hash on the block size for larger

   130   ** chunks.

   131   */

   132   u32 aiSmall[MX_SMALL-1];   /* For sizes 2 through MX_SMALL, inclusive */

   133   u32 aiHash[N_HASH];        /* For sizes MX_SMALL+1 and larger */

   134 

   135   /*

   136   ** Memory available for allocation. nPool is the size of the array

   137   ** (in Mem3Blocks) pointed to by aPool less 2.

   138   */

   139   u32 nPool;

   140   Mem3Block *aPool;

   141 } mem3;

   142 

   143 /*

   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.

   146 */

   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;

   155   }

   156   if( next ){

   157     mem3.aPool[next].u.list.prev = prev;

   158   }

   159   mem3.aPool[i].u.list.next = 0;

   160   mem3.aPool[i].u.list.prev = 0;

   161 }

   162 

   163 /*

   164 ** Unlink the chunk at index i from 

   165 ** whatever list is currently a member of.

   166 */

   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]);

   180   }

   181 }

   182 

   183 /*

   184 ** Link the chunk at mem3.aPool[i] so that is on the list rooted

   185 ** at *pRoot.

   186 */

   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;

   193   }

   194   *pRoot = i;

   195 }

   196 

   197 /*

   198 ** Link the chunk at index i into either the appropriate

   199 ** small chunk list, or into the large chunk hash table.

   200 */

   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]);

   214   }

   215 }

   216 

   217 /*

   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 ** sqlite3Config.bMemStat is true.

   221 */

   222 static void memsys3Enter(void){

   223   if( sqlite3Config.bMemstat==0 && mem3.mutex==0 ){

   224     mem3.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM);

   225   }

   226   sqlite3_mutex_enter(mem3.mutex);

   227 }

   228 static void memsys3Leave(void){

   229   sqlite3_mutex_leave(mem3.mutex);

   230 }

   231 

   232 /*

   233 ** Called when we are unable to satisfy an allocation of nBytes.

   234 */

   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;

   243   }

   244 }

   245 

   246 

   247 /*

   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.

   251 */

   252 static void *memsys3Checkout(u32 i, int 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];

   263 }

   264 

   265 /*

   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.

   269 */

   270 static void *memsys3FromMaster(int 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;

   294     }

   295     return (void*)&mem3.aPool[newi];

   296   }

   297 }

   298 

   299 /*

   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[].  

   303 **

   304 ** This routine examines all entries on the given list and tries

   305 ** to coalesce each entries with adjacent free chunks.  

   306 **

   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.

   314 */

   315 static void memsys3Merge(u32 *pRoot){

   316   u32 iNext, prev, size, i, x;

   317 

   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;

   329       }

   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;

   339     }

   340     if( size>mem3.szMaster ){

   341       mem3.iMaster = i;

   342       mem3.szMaster = size;

   343     }

   344   }

   345 }

   346 

   347 /*

   348 ** Return a block of memory of at least nBytes in size.

   349 ** Return NULL if unable.

   350 **

   351 ** This function assumes that the necessary mutexes, if any, are

   352 ** already held by the caller. Hence "Unsafe".

   353 */

   354 static void *memsys3MallocUnsafe(int nByte){

   355   u32 i;

   356   int nBlock;

   357   int toFree;

   358 

   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;

   365   }

   366   assert( nBlock>=2 );

   367 

   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).

   372   */

   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);

   378     }

   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);

   385       }

   386     }

   387   }

   388 

   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.

   392   */

   393   if( mem3.szMaster>=nBlock ){

   394     return memsys3FromMaster(nBlock);

   395   }

   396 

   397 

   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!)

   404   */

   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;

   411     }

   412     for(i=0; i<N_HASH; i++){

   413       memsys3Merge(&mem3.aiHash[i]);

   414     }

   415     for(i=0; i<MX_SMALL-1; i++){

   416       memsys3Merge(&mem3.aiSmall[i]);

   417     }

   418     if( mem3.szMaster ){

   419       memsys3Unlink(mem3.iMaster);

   420       if( mem3.szMaster>=nBlock ){

   421         return memsys3FromMaster(nBlock);

   422       }

   423     }

   424   }

   425 

   426   /* If none of the above worked, then we fail. */

   427   return 0;

   428 }

   429 

   430 /*

   431 ** Free an outstanding memory allocation.

   432 **

   433 ** This function assumes that the necessary mutexes, if any, are

   434 ** already held by the caller. Hence "Unsafe".

   435 */

   436 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);

   450 

   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;

   461     }

   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;

   468     }

   469   }

   470 }

   471 

   472 /*

   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.

   476 */

   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;

   483 }

   484 

   485 /*

   486 ** Round up a request size to the next valid allocation size.

   487 */

   488 static int memsys3Roundup(int n){

   489   if( n<=12 ){

   490     return 12;

   491   }else{

   492     return ((n+11)&~7) - 4;

   493   }

   494 }

   495 

   496 /*

   497 ** Allocate nBytes of memory.

   498 */

   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; 

   506 }

   507 

   508 /*

   509 ** Free memory.

   510 */

   511 void memsys3Free(void *pPrior){

   512   assert( pPrior );

   513   memsys3Enter();

   514   memsys3FreeUnsafe(pPrior);

   515   memsys3Leave();

   516 }

   517 

   518 /*

   519 ** Change the size of an existing memory allocation

   520 */

   521 void *memsys3Realloc(void *pPrior, int nBytes){

   522   int nOld;

   523   void *p;

   524   if( pPrior==0 ){

   525     return sqlite3_malloc(nBytes);

   526   }

   527   if( nBytes<=0 ){

   528     sqlite3_free(pPrior);

   529     return 0;

   530   }

   531   nOld = memsys3Size(pPrior);

   532   if( nBytes<=nOld && nBytes>=nOld-128 ){

   533     return pPrior;

   534   }

   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);

   542     }

   543     memsys3FreeUnsafe(pPrior);

   544   }

   545   memsys3Leave();

   546   return p;

   547 }

   548 

   549 /*

   550 ** Initialize this module.

   551 */

   552 static int memsys3Init(void *NotUsed){

   553   if( !sqlite3Config.pHeap ){

   554     return SQLITE_ERROR;

   555   }

   556 

   557   /* Store a pointer to the memory block in global structure mem3. */

   558   assert( sizeof(Mem3Block)==8 );

   559   mem3.aPool = (Mem3Block *)sqlite3Config.pHeap;

   560   mem3.nPool = (sqlite3Config.nHeap / sizeof(Mem3Block)) - 2;

   561 

   562   /* Initialize the master block. */

   563   mem3.szMaster = mem3.nPool;

   564   mem3.mnMaster = mem3.szMaster;

   565   mem3.iMaster = 1;

   566   mem3.aPool[0].u.hdr.size4x = (mem3.szMaster<<2) + 2;

   567   mem3.aPool[mem3.nPool].u.hdr.prevSize = mem3.nPool;

   568   mem3.aPool[mem3.nPool].u.hdr.size4x = 1;

   569 

   570   return SQLITE_OK;

   571 }

   572 

   573 /*

   574 ** Deinitialize this module.

   575 */

   576 static void memsys3Shutdown(void *NotUsed){

   577   return;

   578 }

   579 

   580 

   581 

   582 /*

   583 ** Open the file indicated and write a log of all unfreed memory 

   584 ** allocations into that log.

   585 */

   586 #ifdef SQLITE_DEBUG

   587 void sqlite3Memsys3Dump(const char *zFilename){

   588   FILE *out;

   589   int i, j;

   590   u32 size;

   591   if( zFilename==0 || zFilename[0]==0 ){

   592     out = stdout;

   593   }else{

   594     out = fopen(zFilename, "w");

   595     if( out==0 ){

   596       fprintf(stderr, "** Unable to output memory debug output log: %s **\n",

   597                       zFilename);

   598       return;

   599     }

   600   }

   601   memsys3Enter();

   602   fprintf(out, "CHUNKS:\n");

   603   for(i=1; i<=mem3.nPool; i+=size/4){

   604     size = mem3.aPool[i-1].u.hdr.size4x;

   605     if( size/4<=1 ){

   606       fprintf(out, "%p size error\n", &mem3.aPool[i]);

   607       assert( 0 );

   608       break;

   609     }

   610     if( (size&1)==0 && mem3.aPool[i+size/4-1].u.hdr.prevSize!=size/4 ){

   611       fprintf(out, "%p tail size does not match\n", &mem3.aPool[i]);

   612       assert( 0 );

   613       break;

   614     }

   615     if( ((mem3.aPool[i+size/4-1].u.hdr.size4x&2)>>1)!=(size&1) ){

   616       fprintf(out, "%p tail checkout bit is incorrect\n", &mem3.aPool[i]);

   617       assert( 0 );

   618       break;

   619     }

   620     if( size&1 ){

   621       fprintf(out, "%p %6d bytes checked out\n", &mem3.aPool[i], (size/4)*8-8);

   622     }else{

   623       fprintf(out, "%p %6d bytes free%s\n", &mem3.aPool[i], (size/4)*8-8,

   624                   i==mem3.iMaster ? " **master**" : "");

   625     }

   626   }

   627   for(i=0; i<MX_SMALL-1; i++){

   628     if( mem3.aiSmall[i]==0 ) continue;

   629     fprintf(out, "small(%2d):", i);

   630     for(j = mem3.aiSmall[i]; j>0; j=mem3.aPool[j].u.list.next){

   631       fprintf(out, " %p(%d)", &mem3.aPool[j],

   632               (mem3.aPool[j-1].u.hdr.size4x/4)*8-8);

   633     }

   634     fprintf(out, "\n"); 

   635   }

   636   for(i=0; i<N_HASH; i++){

   637     if( mem3.aiHash[i]==0 ) continue;

   638     fprintf(out, "hash(%2d):", i);

   639     for(j = mem3.aiHash[i]; j>0; j=mem3.aPool[j].u.list.next){

   640       fprintf(out, " %p(%d)", &mem3.aPool[j],

   641               (mem3.aPool[j-1].u.hdr.size4x/4)*8-8);

   642     }

   643     fprintf(out, "\n"); 

   644   }

   645   fprintf(out, "master=%d\n", mem3.iMaster);

   646   fprintf(out, "nowUsed=%d\n", mem3.nPool*8 - mem3.szMaster*8);

   647   fprintf(out, "mxUsed=%d\n", mem3.nPool*8 - mem3.mnMaster*8);

   648   sqlite3_mutex_leave(mem3.mutex);

   649   if( out==stdout ){

   650     fflush(stdout);

   651   }else{

   652     fclose(out);

   653   }

   654 }

   655 #endif

   656 

   657 /*

   658 ** This routine is the only routine in this file with external 

   659 ** linkage.

   660 **

   661 ** Populate the low-level memory allocation function pointers in

   662 ** sqlite3Config.m with pointers to the routines in this file. The

   663 ** arguments specify the block of memory to manage.

   664 **

   665 ** This routine is only called by sqlite3_config(), and therefore

   666 ** is not required to be threadsafe (it is not).

   667 */

   668 const sqlite3_mem_methods *sqlite3MemGetMemsys3(void){

   669   static const sqlite3_mem_methods mempoolMethods = {

   670      memsys3Malloc,

   671      memsys3Free,

   672      memsys3Realloc,

   673      memsys3Size,

   674      memsys3Roundup,

   675      memsys3Init,

   676      memsys3Shutdown,

   677      0

   678   };

   679   return &mempoolMethods;

   680 }

   681 

   682 #endif /* SQLITE_ENABLE_MEMSYS3 */