mem3.c

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    void *p = memsys3Checkout(mem.iMaster, mem.szMaster);
    mem.iMaster = 0;
    mem.szMaster = 0;
    mem.mnMaster = 0;
    return p;
  }else{
    /* Split the master block.  Return the tail. */
    int newi;
    newi = mem.iMaster + mem.szMaster - nBlock;
    assert( newi > mem.iMaster+1 );
    mem.aPool[mem.iMaster+mem.szMaster-1].u.hdr.prevSize = -nBlock;
    mem.aPool[newi-1].u.hdr.size = -nBlock;
    mem.szMaster -= nBlock;
    mem.aPool[newi-1].u.hdr.prevSize = mem.szMaster;
    mem.aPool[mem.iMaster-1].u.hdr.size = mem.szMaster;
    if( mem.szMaster < mem.mnMaster ){
      mem.mnMaster = mem.szMaster;
    }
    return (void*)&mem.aPool[newi];
  }
}

/*
** *pRoot is the head of a list of free chunks of the same size
** or same size hash.  In other words, *pRoot is an entry in either
** mem.aiSmall[] or mem.aiHash[].  
**
** This routine examines all entries on the given list and tries
** to coalesce each entries with adjacent free chunks.  
**
** If it sees a chunk that is larger than mem.iMaster, it replaces 
** the current mem.iMaster with the new larger chunk.  In order for
** this mem.iMaster replacement to work, the master chunk must be
** linked into the hash tables.  That is not the normal state of
** affairs, of course.  The calling routine must link the master
** chunk before invoking this routine, then must unlink the (possibly
** changed) master chunk once this routine has finished.
*/
static void memsys3Merge(int *pRoot){
  int iNext, prev, size, i;

  assert( sqlite3_mutex_held(mem.mutex) );
  for(i=*pRoot; i>0; i=iNext){
    iNext = mem.aPool[i].u.list.next;
    size = mem.aPool[i-1].u.hdr.size;
    assert( size>0 );
    if( mem.aPool[i-1].u.hdr.prevSize>0 ){
      memsys3UnlinkFromList(i, pRoot);
      prev = i - mem.aPool[i-1].u.hdr.prevSize;
      assert( prev>=0 );
      if( prev==iNext ){
        iNext = mem.aPool[prev].u.list.next;
      }
      memsys3Unlink(prev);
      size = i + size - prev;
      mem.aPool[prev-1].u.hdr.size = size;
      mem.aPool[prev+size-1].u.hdr.prevSize = size;
      memsys3Link(prev);
      i = prev;
    }
    if( size>mem.szMaster ){
      mem.iMaster = i;
      mem.szMaster = size;
    }
  }
}

/*
** Return a block of memory of at least nBytes in size.
** Return NULL if unable.
*/
static void *memsys3Malloc(int nByte){
  int i;
  int nBlock;
  int toFree;

  assert( sqlite3_mutex_held(mem.mutex) );
  assert( sizeof(Mem3Block)==8 );
  if( nByte<=0 ){
    nBlock = 2;
  }else{
    nBlock = (nByte + 15)/8;
  }
  assert( nBlock >= 2 );

  /* STEP 1:
  ** Look for an entry of the correct size in either the small
  ** chunk table or in the large chunk hash table.  This is
  ** successful most of the time (about 9 times out of 10).
  */
  if( nBlock <= MX_SMALL ){
    i = mem.aiSmall[nBlock-2];
    if( i>0 ){
      memsys3UnlinkFromList(i, &mem.aiSmall[nBlock-2]);
      return memsys3Checkout(i, nBlock);
    }
  }else{
    int hash = nBlock % N_HASH;
    for(i=mem.aiHash[hash]; i>0; i=mem.aPool[i].u.list.next){
      if( mem.aPool[i-1].u.hdr.size==nBlock ){
        memsys3UnlinkFromList(i, &mem.aiHash[hash]);
        return memsys3Checkout(i, nBlock);
      }
    }
  }

  /* STEP 2:
  ** Try to satisfy the allocation by carving a piece off of the end
  ** of the master chunk.  This step usually works if step 1 fails.
  */
  if( mem.szMaster>=nBlock ){
    return memsys3FromMaster(nBlock);
  }


  /* STEP 3:  
  ** Loop through the entire memory pool.  Coalesce adjacent free
  ** chunks.  Recompute the master chunk as the largest free chunk.
  ** Then try again to satisfy the allocation by carving a piece off
  ** of the end of the master chunk.  This step happens very
  ** rarely (we hope!)
  */
  for(toFree=nBlock*16; toFree<SQLITE_MEMORY_SIZE*2; toFree *= 2){
    memsys3OutOfMemory(toFree);
    if( mem.iMaster ){
      memsys3Link(mem.iMaster);
      mem.iMaster = 0;
      mem.szMaster = 0;
    }
    for(i=0; i<N_HASH; i++){
      memsys3Merge(&mem.aiHash[i]);
    }
    for(i=0; i<MX_SMALL-1; i++){
      memsys3Merge(&mem.aiSmall[i]);
    }
    if( mem.szMaster ){
      memsys3Unlink(mem.iMaster);
      if( mem.szMaster>=nBlock ){
        return memsys3FromMaster(nBlock);
      }
    }
  }

  /* If none of the above worked, then we fail. */
  return 0;
}

/*
** Free an outstanding memory allocation.
*/
void memsys3Free(void *pOld){
  Mem3Block *p = (Mem3Block*)pOld;
  int i;
  int size;
  assert( sqlite3_mutex_held(mem.mutex) );
  assert( p>mem.aPool && p<&mem.aPool[SQLITE_MEMORY_SIZE/8] );
  i = p - mem.aPool;
  size = -mem.aPool[i-1].u.hdr.size;
  assert( size>=2 );
  assert( mem.aPool[i+size-1].u.hdr.prevSize==-size );
  mem.aPool[i-1].u.hdr.size = size;
  mem.aPool[i+size-1].u.hdr.prevSize = size;
  memsys3Link(i);

  /* Try to expand the master using the newly freed chunk */
  if( mem.iMaster ){
    while( mem.aPool[mem.iMaster-1].u.hdr.prevSize>0 ){
      size = mem.aPool[mem.iMaster-1].u.hdr.prevSize;
      mem.iMaster -= size;
      mem.szMaster += size;
      memsys3Unlink(mem.iMaster);
      mem.aPool[mem.iMaster-1].u.hdr.size = mem.szMaster;
      mem.aPool[mem.iMaster+mem.szMaster-1].u.hdr.prevSize = mem.szMaster;
    }
    while( mem.aPool[mem.iMaster+mem.szMaster-1].u.hdr.size>0 ){
      memsys3Unlink(mem.iMaster+mem.szMaster);
      mem.szMaster += mem.aPool[mem.iMaster+mem.szMaster-1].u.hdr.size;
      mem.aPool[mem.iMaster-1].u.hdr.size = mem.szMaster;
      mem.aPool[mem.iMaster+mem.szMaster-1].u.hdr.prevSize = mem.szMaster;
    }
  }
}

/*
** Allocate nBytes of memory
*/
void *sqlite3_malloc(int nBytes){
  sqlite3_int64 *p = 0;
  if( nBytes>0 ){
    memsys3Enter();
    p = memsys3Malloc(nBytes);
    sqlite3_mutex_leave(mem.mutex);
  }
  return (void*)p; 
}

/*
** Free memory.
*/
void sqlite3_free(void *pPrior){
  if( pPrior==0 ){
    return;
  }
  assert( mem.mutex!=0 );
  sqlite3_mutex_enter(mem.mutex);
  memsys3Free(pPrior);
  sqlite3_mutex_leave(mem.mutex);  
}

/*
** Change the size of an existing memory allocation
*/
void *sqlite3_realloc(void *pPrior, int nBytes){
  int nOld;
  void *p;
  if( pPrior==0 ){
    return sqlite3_malloc(nBytes);
  }
  if( nBytes<=0 ){
    sqlite3_free(pPrior);
    return 0;
  }
  assert( mem.mutex!=0 );
  nOld = memsys3Size(pPrior);
  if( nBytes<=nOld && nBytes>=nOld-128 ){
    return pPrior;
  }
  sqlite3_mutex_enter(mem.mutex);
  p = memsys3Malloc(nBytes);
  if( p ){
    if( nOld<nBytes ){
      memcpy(p, pPrior, nOld);
    }else{
      memcpy(p, pPrior, nBytes);
    }
    memsys3Free(pPrior);
  }
  sqlite3_mutex_leave(mem.mutex);
  return p;
}

/*
** Open the file indicated and write a log of all unfreed memory 
** allocations into that log.
*/
void sqlite3_memdebug_dump(const char *zFilename){
#ifdef SQLITE_DEBUG
  FILE *out;
  int i, j, size;
  if( zFilename==0 || zFilename[0]==0 ){
    out = stdout;
  }else{
    out = fopen(zFilename, "w");
    if( out==0 ){
      fprintf(stderr, "** Unable to output memory debug output log: %s **\n",
                      zFilename);
      return;
    }
  }
  memsys3Enter();
  fprintf(out, "CHUNKS:\n");
  for(i=1; i<=SQLITE_MEMORY_SIZE/8; i+=size){
    size = mem.aPool[i-1].u.hdr.size;
    if( size>=-1 && size<=1 ){
      fprintf(out, "%p size error\n", &mem.aPool[i]);
      assert( 0 );
      break;
    }
    if( mem.aPool[i+(size<0?-size:size)-1].u.hdr.prevSize!=size ){
      fprintf(out, "%p tail size does not match\n", &mem.aPool[i]);
      assert( 0 );
      break;
    }
    if( size<0 ){
      size = -size;
      fprintf(out, "%p %6d bytes checked out\n", &mem.aPool[i], size*8-8);
    }else{
      fprintf(out, "%p %6d bytes free%s\n", &mem.aPool[i], size*8-8,
                  i==mem.iMaster ? " **master**" : "");
    }
  }
  for(i=0; i<MX_SMALL-1; i++){
    if( mem.aiSmall[i]==0 ) continue;
    fprintf(out, "small(%2d):", i);
    for(j = mem.aiSmall[i]; j>0; j=mem.aPool[j].u.list.next){
      fprintf(out, " %p(%d)", &mem.aPool[j], mem.aPool[j-1].u.hdr.size*8-8);
    }
    fprintf(out, "\n"); 
  }
  for(i=0; i<N_HASH; i++){
    if( mem.aiHash[i]==0 ) continue;
    fprintf(out, "hash(%2d):", i);
    for(j = mem.aiHash[i]; j>0; j=mem.aPool[j].u.list.next){
      fprintf(out, " %p(%d)", &mem.aPool[j], mem.aPool[j-1].u.hdr.size*8-8);
    }
    fprintf(out, "\n"); 
  }
  fprintf(out, "master=%d\n", mem.iMaster);
  fprintf(out, "nowUsed=%d\n", SQLITE_MEMORY_SIZE - mem.szMaster*8);
  fprintf(out, "mxUsed=%d\n", SQLITE_MEMORY_SIZE - mem.mnMaster*8);
  sqlite3_mutex_leave(mem.mutex);
  if( out==stdout ){
    fflush(stdout);
  }else{
    fclose(out);
  }
#endif
}


#endif /* !SQLITE_MEMORY_SIZE */