sl@0: /*
sl@0: ** 2007 August 14
sl@0: **
sl@0: ** The author disclaims copyright to this source code.  In place of
sl@0: ** a legal notice, here is a blessing:
sl@0: **
sl@0: **    May you do good and not evil.
sl@0: **    May you find forgiveness for yourself and forgive others.
sl@0: **    May you share freely, never taking more than you give.
sl@0: **
sl@0: *************************************************************************
sl@0: **
sl@0: ** This file contains low-level memory allocation drivers for when
sl@0: ** SQLite will use the standard C-library malloc/realloc/free interface
sl@0: ** to obtain the memory it needs.
sl@0: **
sl@0: ** This file contains implementations of the low-level memory allocation
sl@0: ** routines specified in the sqlite3_mem_methods object.
sl@0: **
sl@0: ** $Id: mem1.c,v 1.26 2008/09/01 18:34:20 danielk1977 Exp $
sl@0: */
sl@0: #include "sqliteInt.h"
sl@0: 
sl@0: /*
sl@0: ** This version of the memory allocator is the default.  It is
sl@0: ** used when no other memory allocator is specified using compile-time
sl@0: ** macros.
sl@0: */
sl@0: #ifdef SQLITE_SYSTEM_MALLOC
sl@0: 
sl@0: /*
sl@0: ** Like malloc(), but remember the size of the allocation
sl@0: ** so that we can find it later using sqlite3MemSize().
sl@0: **
sl@0: ** For this low-level routine, we are guaranteed that nByte>0 because
sl@0: ** cases of nByte<=0 will be intercepted and dealt with by higher level
sl@0: ** routines.
sl@0: */
sl@0: static void *sqlite3MemMalloc(int nByte){
sl@0:   sqlite3_int64 *p;
sl@0:   assert( nByte>0 );
sl@0:   nByte = (nByte+7)&~7;
sl@0:   p = malloc( nByte+8 );
sl@0:   if( p ){
sl@0:     p[0] = nByte;
sl@0:     p++;
sl@0:   }
sl@0:   return (void *)p;
sl@0: }
sl@0: 
sl@0: /*
sl@0: ** Like free() but works for allocations obtained from sqlite3MemMalloc()
sl@0: ** or sqlite3MemRealloc().
sl@0: **
sl@0: ** For this low-level routine, we already know that pPrior!=0 since
sl@0: ** cases where pPrior==0 will have been intecepted and dealt with
sl@0: ** by higher-level routines.
sl@0: */
sl@0: static void sqlite3MemFree(void *pPrior){
sl@0:   sqlite3_int64 *p = (sqlite3_int64*)pPrior;
sl@0:   assert( pPrior!=0 );
sl@0:   p--;
sl@0:   free(p);
sl@0: }
sl@0: 
sl@0: /*
sl@0: ** Like realloc().  Resize an allocation previously obtained from
sl@0: ** sqlite3MemMalloc().
sl@0: **
sl@0: ** For this low-level interface, we know that pPrior!=0.  Cases where
sl@0: ** pPrior==0 while have been intercepted by higher-level routine and
sl@0: ** redirected to xMalloc.  Similarly, we know that nByte>0 becauses
sl@0: ** cases where nByte<=0 will have been intercepted by higher-level
sl@0: ** routines and redirected to xFree.
sl@0: */
sl@0: static void *sqlite3MemRealloc(void *pPrior, int nByte){
sl@0:   sqlite3_int64 *p = (sqlite3_int64*)pPrior;
sl@0:   assert( pPrior!=0 && nByte>0 );
sl@0:   nByte = (nByte+7)&~7;
sl@0:   p = (sqlite3_int64*)pPrior;
sl@0:   p--;
sl@0:   p = realloc(p, nByte+8 );
sl@0:   if( p ){
sl@0:     p[0] = nByte;
sl@0:     p++;
sl@0:   }
sl@0:   return (void*)p;
sl@0: }
sl@0: 
sl@0: /*
sl@0: ** Report the allocated size of a prior return from xMalloc()
sl@0: ** or xRealloc().
sl@0: */
sl@0: static int sqlite3MemSize(void *pPrior){
sl@0:   sqlite3_int64 *p;
sl@0:   if( pPrior==0 ) return 0;
sl@0:   p = (sqlite3_int64*)pPrior;
sl@0:   p--;
sl@0:   return p[0];
sl@0: }
sl@0: 
sl@0: /*
sl@0: ** Round up a request size to the next valid allocation size.
sl@0: */
sl@0: static int sqlite3MemRoundup(int n){
sl@0:   return (n+7) & ~7;
sl@0: }
sl@0: 
sl@0: /*
sl@0: ** Initialize this module.
sl@0: */
sl@0: static int sqlite3MemInit(void *NotUsed){
sl@0:   return SQLITE_OK;
sl@0: }
sl@0: 
sl@0: /*
sl@0: ** Deinitialize this module.
sl@0: */
sl@0: static void sqlite3MemShutdown(void *NotUsed){
sl@0:   return;
sl@0: }
sl@0: 
sl@0: const sqlite3_mem_methods *sqlite3MemGetDefault(void){
sl@0:   static const sqlite3_mem_methods defaultMethods = {
sl@0:      sqlite3MemMalloc,
sl@0:      sqlite3MemFree,
sl@0:      sqlite3MemRealloc,
sl@0:      sqlite3MemSize,
sl@0:      sqlite3MemRoundup,
sl@0:      sqlite3MemInit,
sl@0:      sqlite3MemShutdown,
sl@0:      0
sl@0:   };
sl@0:   return &defaultMethods;
sl@0: }
sl@0: 
sl@0: /*
sl@0: ** This routine is the only routine in this file with external linkage.
sl@0: **
sl@0: ** Populate the low-level memory allocation function pointers in
sl@0: ** sqlite3GlobalConfig.m with pointers to the routines in this file.
sl@0: */
sl@0: void sqlite3MemSetDefault(void){
sl@0:   sqlite3_config(SQLITE_CONFIG_MALLOC, sqlite3MemGetDefault());
sl@0: }
sl@0: 
sl@0: #endif /* SQLITE_SYSTEM_MALLOC */