/*

 ** 2007 August 14

 **

 ** The author disclaims copyright to this source code.  In place of

 ** a legal notice, here is a blessing:

 **

 **    May you do good and not evil.

 **    May you find forgiveness for yourself and forgive others.

 **    May you share freely, never taking more than you give.

 **

 *************************************************************************

 **

 ** This file contains low-level memory allocation drivers for when

 ** SQLite will use the standard C-library malloc/realloc/free interface

 ** to obtain the memory it needs.

 **

 ** This file contains implementations of the low-level memory allocation

 ** routines specified in the sqlite3_mem_methods object.

 **

 ** $Id: mem1.c,v 1.26 2008/09/01 18:34:20 danielk1977 Exp $

 */

 #include "sqliteInt.h"

 /*

 ** This version of the memory allocator is the default.  It is

 ** used when no other memory allocator is specified using compile-time

 ** macros.

 */

 #ifdef SQLITE_SYSTEM_MALLOC

 /*

 ** Like malloc(), but remember the size of the allocation

 ** so that we can find it later using sqlite3MemSize().

 **

 ** For this low-level routine, we are guaranteed that nByte>0 because

 ** cases of nByte<=0 will be intercepted and dealt with by higher level

 ** routines.

 */

 static void *sqlite3MemMalloc(int nByte){

   sqlite3_int64 *p;

   assert( nByte>0 );

   nByte = (nByte+7)&~7;

   p = malloc( nByte+8 );

   if( p ){

     p[0] = nByte;

     p++;

   }

   return (void *)p;

 }

 /*

 ** Like free() but works for allocations obtained from sqlite3MemMalloc()

 ** or sqlite3MemRealloc().

 **

 ** For this low-level routine, we already know that pPrior!=0 since

 ** cases where pPrior==0 will have been intecepted and dealt with

 ** by higher-level routines.

 */

 static void sqlite3MemFree(void *pPrior){

   sqlite3_int64 *p = (sqlite3_int64*)pPrior;

   assert( pPrior!=0 );

   p--;

   free(p);

 }

 /*

 ** Like realloc().  Resize an allocation previously obtained from

 ** sqlite3MemMalloc().

 **

 ** For this low-level interface, we know that pPrior!=0.  Cases where

 ** pPrior==0 while have been intercepted by higher-level routine and

 ** redirected to xMalloc.  Similarly, we know that nByte>0 becauses

 ** cases where nByte<=0 will have been intercepted by higher-level

 ** routines and redirected to xFree.

 */

 static void *sqlite3MemRealloc(void *pPrior, int nByte){

   sqlite3_int64 *p = (sqlite3_int64*)pPrior;

   assert( pPrior!=0 && nByte>0 );

   nByte = (nByte+7)&~7;

   p = (sqlite3_int64*)pPrior;

   p--;

   p = realloc(p, nByte+8 );

   if( p ){

     p[0] = nByte;

     p++;

   }

   return (void*)p;

 }

 /*

 ** Report the allocated size of a prior return from xMalloc()

 ** or xRealloc().

 */

 static int sqlite3MemSize(void *pPrior){

   sqlite3_int64 *p;

   if( pPrior==0 ) return 0;

   p = (sqlite3_int64*)pPrior;

   p--;

   return p[0];

 }

 /*

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

 */

 static int sqlite3MemRoundup(int n){

   return (n+7) & ~7;

 }

 /*

 ** Initialize this module.

 */

 static int sqlite3MemInit(void *NotUsed){

   return SQLITE_OK;

 }

 /*

 ** Deinitialize this module.

 */

 static void sqlite3MemShutdown(void *NotUsed){

   return;

 }

 const sqlite3_mem_methods *sqlite3MemGetDefault(void){

   static const sqlite3_mem_methods defaultMethods = {

      sqlite3MemMalloc,

      sqlite3MemFree,

      sqlite3MemRealloc,

      sqlite3MemSize,

      sqlite3MemRoundup,

      sqlite3MemInit,

      sqlite3MemShutdown,

      0

   };

   return &defaultMethods;

 }

 /*

 ** This routine is the only routine in this file with external linkage.

 **

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

 ** sqlite3GlobalConfig.m with pointers to the routines in this file.

 */

 void sqlite3MemSetDefault(void){

   sqlite3_config(SQLITE_CONFIG_MALLOC, sqlite3MemGetDefault());

 }

 #endif /* SQLITE_SYSTEM_MALLOC */