malloc.c

最新的sqlite3.6.2源代码

      mem0.aScratchFree[mem0.nScratchFree++] = i;
      sqlite3StatusAdd(SQLITE_STATUS_SCRATCH_USED, -1);
      sqlite3_mutex_leave(mem0.mutex);
    }
  }
}

/*
** Allocate memory to be used by the page cache.  Make use of the
** memory buffer provided by SQLITE_CONFIG_PAGECACHE if there is one
** and that memory is of the right size and is not completely
** consumed.  Otherwise, failover to sqlite3Malloc().
*/
#if 0
void *sqlite3PageMalloc(int n){
  void *p;
  assert( n>0 );
  assert( (n & (n-1))==0 );
  assert( n>=512 && n<=32768 );

  if( sqlite3Config.szPage<n ){
    goto page_overflow;
  }else{  
    sqlite3_mutex_enter(mem0.mutex);
    if( mem0.nPageFree==0 ){
      sqlite3_mutex_leave(mem0.mutex);
      goto page_overflow;
    }else{
      int i;
      i = mem0.aPageFree[--mem0.nPageFree];
      sqlite3_mutex_leave(mem0.mutex);
      i *= sqlite3Config.szPage;
      sqlite3StatusSet(SQLITE_STATUS_PAGECACHE_SIZE, n);
      sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_USED, 1);
      p = (void*)&((char*)sqlite3Config.pPage)[i];
    }
  }
  return p;

page_overflow:
  if( sqlite3Config.bMemstat ){
    sqlite3_mutex_enter(mem0.mutex);
    sqlite3StatusSet(SQLITE_STATUS_PAGECACHE_SIZE, n);
    n = mallocWithAlarm(n, &p);
    if( p ) sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_OVERFLOW, n);
    sqlite3_mutex_leave(mem0.mutex);
  }else{
    p = sqlite3Config.m.xMalloc(n);
  }
  return p;    
}
void sqlite3PageFree(void *p){
  if( p ){
    if( sqlite3Config.pPage==0
           || p<sqlite3Config.pPage
           || p>=(void*)mem0.aPageFree ){
      /* In this case, the page allocation was obtained from a regular 
      ** call to sqlite3_mem_methods.xMalloc() (a page-cache-memory 
      ** "overflow"). Free the block with sqlite3_mem_methods.xFree().
      */
      if( sqlite3Config.bMemstat ){
        int iSize = sqlite3MallocSize(p);
        sqlite3_mutex_enter(mem0.mutex);
        sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_OVERFLOW, -iSize);
        sqlite3StatusAdd(SQLITE_STATUS_MEMORY_USED, -iSize);
        sqlite3Config.m.xFree(p);
        sqlite3_mutex_leave(mem0.mutex);
      }else{
        sqlite3Config.m.xFree(p);
      }
    }else{
      /* The page allocation was allocated from the sqlite3Config.pPage
      ** buffer. In this case all that is add the index of the page in
      ** the sqlite3Config.pPage array to the set of free indexes stored
      ** in the mem0.aPageFree[] array.
      */
      int i;
      i = (u8 *)p - (u8 *)sqlite3Config.pPage;
      i /= sqlite3Config.szPage;
      assert( i>=0 && i<sqlite3Config.nPage );
      sqlite3_mutex_enter(mem0.mutex);
      assert( mem0.nPageFree<sqlite3Config.nPage );
      mem0.aPageFree[mem0.nPageFree++] = i;
      sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_USED, -1);
      sqlite3_mutex_leave(mem0.mutex);
#if !defined(NDEBUG) && 0
      /* Assert that a duplicate was not just inserted into aPageFree[]. */
      for(i=0; i<mem0.nPageFree-1; i++){
        assert( mem0.aPageFree[i]!=mem0.aPageFree[mem0.nPageFree-1] );
      }
#endif
    }
  }
}
#endif

/*
** TRUE if p is a lookaside memory allocation from db
*/
static int isLookaside(sqlite3 *db, void *p){
  return db && p && p>=db->lookaside.pStart && p<db->lookaside.pEnd;
}

/*
** Return the size of a memory allocation previously obtained from
** sqlite3Malloc() or sqlite3_malloc().
*/
int sqlite3MallocSize(void *p){
  return sqlite3Config.m.xSize(p);
}
int sqlite3DbMallocSize(sqlite3 *db, void *p){
  if( isLookaside(db, p) ){
    return db->lookaside.sz;
  }else{
    return sqlite3Config.m.xSize(p);
  }
}

/*
** Free memory previously obtained from sqlite3Malloc().
*/
void sqlite3_free(void *p){
  if( p==0 ) return;
  if( sqlite3Config.bMemstat ){
    sqlite3_mutex_enter(mem0.mutex);
    sqlite3StatusAdd(SQLITE_STATUS_MEMORY_USED, -sqlite3MallocSize(p));
    sqlite3Config.m.xFree(p);
    sqlite3_mutex_leave(mem0.mutex);
  }else{
    sqlite3Config.m.xFree(p);
  }
}

/*
** Free memory that might be associated with a particular database
** connection.
*/
void sqlite3DbFree(sqlite3 *db, void *p){
  if( isLookaside(db, p) ){
    LookasideSlot *pBuf = (LookasideSlot*)p;
    pBuf->pNext = db->lookaside.pFree;
    db->lookaside.pFree = pBuf;
    db->lookaside.nOut--;
  }else{
    sqlite3_free(p);
  }
}

/*
** Change the size of an existing memory allocation
*/
void *sqlite3Realloc(void *pOld, int nBytes){
  int nOld, nNew;
  void *pNew;
  if( pOld==0 ){
    return sqlite3Malloc(nBytes);
  }
  if( nBytes<=0 ){
    sqlite3_free(pOld);
    return 0;
  }
  nOld = sqlite3MallocSize(pOld);
  if( sqlite3Config.bMemstat ){
    sqlite3_mutex_enter(mem0.mutex);
    sqlite3StatusSet(SQLITE_STATUS_MALLOC_SIZE, nBytes);
    nNew = sqlite3Config.m.xRoundup(nBytes);
    if( nOld==nNew ){
      pNew = pOld;
    }else{
      if( sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED)+nNew-nOld >= 
            mem0.alarmThreshold ){
        sqlite3MallocAlarm(nNew-nOld);
      }
      pNew = sqlite3Config.m.xRealloc(pOld, nNew);
      if( pNew==0 && mem0.alarmCallback ){
        sqlite3MallocAlarm(nBytes);
        pNew = sqlite3Config.m.xRealloc(pOld, nNew);
      }
      if( pNew ){
        nNew = sqlite3MallocSize(pNew);
        sqlite3StatusAdd(SQLITE_STATUS_MEMORY_USED, nNew-nOld);
      }
    }
    sqlite3_mutex_leave(mem0.mutex);
  }else{
    pNew = sqlite3Config.m.xRealloc(pOld, nBytes);
  }
  return pNew;
}

/*
** The public interface to sqlite3Realloc.  Make sure that the memory
** subsystem is initialized prior to invoking sqliteRealloc.
*/
void *sqlite3_realloc(void *pOld, int n){
#ifndef SQLITE_OMIT_AUTOINIT
  if( sqlite3_initialize() ) return 0;
#endif
  return sqlite3Realloc(pOld, n);
}


/*
** Allocate and zero memory.
*/ 
void *sqlite3MallocZero(int n){
  void *p = sqlite3Malloc(n);
  if( p ){
    memset(p, 0, n);
  }
  return p;
}

/*
** Allocate and zero memory.  If the allocation fails, make
** the mallocFailed flag in the connection pointer.
*/
void *sqlite3DbMallocZero(sqlite3 *db, int n){
  void *p = sqlite3DbMallocRaw(db, n);
  if( p ){
    memset(p, 0, n);
  }
  return p;
}

/*
** Allocate and zero memory.  If the allocation fails, make
** the mallocFailed flag in the connection pointer.
*/
void *sqlite3DbMallocRaw(sqlite3 *db, int n){
  void *p;
  if( db ){
    LookasideSlot *pBuf;
    if( db->mallocFailed ){
      return 0;
    }
    if( db->lookaside.bEnabled && n<=db->lookaside.sz
         && (pBuf = db->lookaside.pFree)!=0 ){
      db->lookaside.pFree = pBuf->pNext;
      db->lookaside.nOut++;
      if( db->lookaside.nOut>db->lookaside.mxOut ){
        db->lookaside.mxOut = db->lookaside.nOut;
      }
      return (void*)pBuf;
    }
  }
  p = sqlite3Malloc(n);
  if( !p && db ){
    db->mallocFailed = 1;
  }
  return p;
}

/*
** Resize the block of memory pointed to by p to n bytes. If the
** resize fails, set the mallocFailed flag in the connection object.
*/
void *sqlite3DbRealloc(sqlite3 *db, void *p, int n){
  void *pNew = 0;
  if( db->mallocFailed==0 ){
    if( p==0 ){
      return sqlite3DbMallocRaw(db, n);
    }
    if( isLookaside(db, p) ){
      if( n<=db->lookaside.sz ){
        return p;
      }
      pNew = sqlite3DbMallocRaw(db, n);
      if( pNew ){
        memcpy(pNew, p, db->lookaside.sz);
        sqlite3DbFree(db, p);
      }
    }else{
      pNew = sqlite3_realloc(p, n);
      if( !pNew ){
        db->mallocFailed = 1;
      }
    }
  }
  return pNew;
}

/*
** Attempt to reallocate p.  If the reallocation fails, then free p
** and set the mallocFailed flag in the database connection.
*/
void *sqlite3DbReallocOrFree(sqlite3 *db, void *p, int n){
  void *pNew;
  pNew = sqlite3DbRealloc(db, p, n);
  if( !pNew ){
    sqlite3DbFree(db, p);
  }
  return pNew;
}

/*
** Make a copy of a string in memory obtained from sqliteMalloc(). These 
** functions call sqlite3MallocRaw() directly instead of sqliteMalloc(). This
** is because when memory debugging is turned on, these two functions are 
** called via macros that record the current file and line number in the
** ThreadData structure.
*/
char *sqlite3DbStrDup(sqlite3 *db, const char *z){
  char *zNew;
  size_t n;
  if( z==0 ){
    return 0;
  }
  n = strlen(z)+1;
  assert( (n&0x7fffffff)==n );
  zNew = sqlite3DbMallocRaw(db, (int)n);
  if( zNew ){
    memcpy(zNew, z, n);
  }
  return zNew;
}
char *sqlite3DbStrNDup(sqlite3 *db, const char *z, int n){
  char *zNew;
  if( z==0 ){
    return 0;
  }
  assert( (n&0x7fffffff)==n );
  zNew = sqlite3DbMallocRaw(db, n+1);
  if( zNew ){
    memcpy(zNew, z, n);
    zNew[n] = 0;
  }
  return zNew;
}

/*
** Create a string from the zFromat argument and the va_list that follows.
** Store the string in memory obtained from sqliteMalloc() and make *pz
** point to that string.
*/
void sqlite3SetString(char **pz, sqlite3 *db, const char *zFormat, ...){
  va_list ap;
  char *z;

  va_start(ap, zFormat);
  z = sqlite3VMPrintf(db, zFormat, ap);
  va_end(ap);
  sqlite3DbFree(db, *pz);
  *pz = z;
}


/*
** This function must be called before exiting any API function (i.e. 
** returning control to the user) that has called sqlite3_malloc or
** sqlite3_realloc.
**
** The returned value is normally a copy of the second argument to this
** function. However, if a malloc() failure has occured since the previous
** invocation SQLITE_NOMEM is returned instead. 
**
** If the first argument, db, is not NULL and a malloc() error has occured,
** then the connection error-code (the value returned by sqlite3_errcode())
** is set to SQLITE_NOMEM.
*/
int sqlite3ApiExit(sqlite3* db, int rc){
  /* If the db handle is not NULL, then we must hold the connection handle
  ** mutex here. Otherwise the read (and possible write) of db->mallocFailed 
  ** is unsafe, as is the call to sqlite3Error().
  */
  assert( !db || sqlite3_mutex_held(db->mutex) );
  if( db && db->mallocFailed ){
    sqlite3Error(db, SQLITE_NOMEM, 0);
    db->mallocFailed = 0;
    rc = SQLITE_NOMEM;
  }
  return rc & (db ? db->errMask : 0xff);
}