/*

** 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 1.25 2008/07/25 08:49:00 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

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

*/

void sqlite3MemSetDefault(void){

  sqlite3_config(SQLITE_CONFIG_MALLOC, sqlite3MemGetDefault());

}

#endif /* SQLITE_SYSTEM_MALLOC */