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/*
** 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 the C functions that implement a memory
** allocation subsystem for use by SQLite.
**
** $Id: mem1.c,v 1.10 2007/09/02 17:50:35 drh Exp $
*/
/*
** This version of the memory allocator is the default. It is
** used when no other memory allocator is specified using compile-time
** macros.
*/
#if !defined(SQLITE_MEMDEBUG) && !defined(SQLITE_OMIT_MEMORY_ALLOCATION)
/*
** We will eventually construct multiple memory allocation subsystems
** suitable for use in various contexts:
**
** * Normal multi-threaded builds
** * Normal single-threaded builds
** * Debugging builds
**
** This initial version is suitable for use in normal multi-threaded
** builds. We envision that alternative versions will be stored in
** separate source files. #ifdefs will be used to select the code from
** one of the various memN.c source files for use in any given build.
*/
#include "sqliteInt.h"
/*
** All of the static variables used by this module are collected
** into a single structure named "mem". This is to keep the
** static variables organized and to reduce namespace pollution
** when this module is combined with other in the amalgamation.
*/
static struct {
/*
** The alarm callback and its arguments. The mem.mutex lock will
** be held while the callback is running. Recursive calls into
** the memory subsystem are allowed, but no new callbacks will be
** issued. The alarmBusy variable is set to prevent recursive
** callbacks.
*/
sqlite3_int64 alarmThreshold;
void (*alarmCallback)(void*, sqlite3_int64,int);
void *alarmArg;
int alarmBusy;
/*
** Mutex to control access to the memory allocation subsystem.
*/
sqlite3_mutex *mutex;
/*
** Current allocation and high-water mark.
*/
sqlite3_int64 nowUsed;
sqlite3_int64 mxUsed;
} mem;
/*
** Enter the mutex mem.mutex. Allocate it if it is not already allocated.
*/
static void enterMem(void){
if( mem.mutex==0 ){
mem.mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MEM);
}
sqlite3_mutex_enter(mem.mutex);
}
/*
** Return the amount of memory currently checked out.
*/
sqlite3_int64 sqlite3_memory_used(void){
sqlite3_int64 n;
enterMem();
n = mem.nowUsed;
sqlite3_mutex_leave(mem.mutex);
return n;
}
/*
** Return the maximum amount of memory that has ever been
** checked out since either the beginning of this process
** or since the most recent reset.
*/
sqlite3_int64 sqlite3_memory_highwater(int resetFlag){
sqlite3_int64 n;
enterMem();
n = mem.mxUsed;
if( resetFlag ){
mem.mxUsed = mem.nowUsed;
}
sqlite3_mutex_leave(mem.mutex);
return n;
}
/*
** Change the alarm callback
*/
int sqlite3_memory_alarm(
void(*xCallback)(void *pArg, sqlite3_int64 used,int N),
void *pArg,
sqlite3_int64 iThreshold
){
enterMem();
mem.alarmCallback = xCallback;
mem.alarmArg = pArg;
mem.alarmThreshold = iThreshold;
sqlite3_mutex_leave(mem.mutex);
return SQLITE_OK;
}
/*
** Trigger the alarm
*/
static void sqlite3MemsysAlarm(int nByte){
void (*xCallback)(void*,sqlite3_int64,int);
sqlite3_int64 nowUsed;
void *pArg;
if( mem.alarmCallback==0 || mem.alarmBusy ) return;
mem.alarmBusy = 1;
xCallback = mem.alarmCallback;
nowUsed = mem.nowUsed;
pArg = mem.alarmArg;
sqlite3_mutex_leave(mem.mutex);
xCallback(pArg, nowUsed, nByte);
sqlite3_mutex_enter(mem.mutex);
mem.alarmBusy = 0;
}
/*
** Allocate nBytes of memory
*/
void *sqlite3_malloc(int nBytes){
sqlite3_int64 *p = 0;
if( nBytes>0 ){
enterMem();
if( mem.alarmCallback!=0 && mem.nowUsed+nBytes>=mem.alarmThreshold ){
sqlite3MemsysAlarm(nBytes);
}
p = malloc(nBytes+8);
if( p==0 ){
sqlite3MemsysAlarm(nBytes);
p = malloc(nBytes+8);
}
if( p ){
p[0] = nBytes;
p++;
mem.nowUsed += nBytes;
if( mem.nowUsed>mem.mxUsed ){
mem.mxUsed = mem.nowUsed;
}
}
sqlite3_mutex_leave(mem.mutex);
}
return (void*)p;
}
/*
** Free memory.
*/
void sqlite3_free(void *pPrior){
sqlite3_int64 *p;
int nByte;
if( pPrior==0 ){
return;
}
assert( mem.mutex!=0 );
p = pPrior;
p--;
nByte = (int)*p;
sqlite3_mutex_enter(mem.mutex);
mem.nowUsed -= nByte;
free(p);
sqlite3_mutex_leave(mem.mutex);
}
/*
** Change the size of an existing memory allocation
*/
void *sqlite3_realloc(void *pPrior, int nBytes){
int nOld;
sqlite3_int64 *p;
if( pPrior==0 ){
return sqlite3_malloc(nBytes);
}
if( nBytes<=0 ){
sqlite3_free(pPrior);
return 0;
}
p = pPrior;
p--;
nOld = (int)p[0];
assert( mem.mutex!=0 );
sqlite3_mutex_enter(mem.mutex);
if( mem.nowUsed+nBytes-nOld>=mem.alarmThreshold ){
sqlite3MemsysAlarm(nBytes-nOld);
}
p = realloc(p, nBytes+8);
if( p==0 ){
sqlite3MemsysAlarm(nBytes);
p = realloc(p, nBytes+8);
}
if( p ){
p[0] = nBytes;
p++;
mem.nowUsed += nBytes-nOld;
if( mem.nowUsed>mem.mxUsed ){
mem.mxUsed = mem.nowUsed;
}
}
sqlite3_mutex_leave(mem.mutex);
return (void*)p;
}
#endif /* !SQLITE_MEMDEBUG && !SQLITE_OMIT_MEMORY_ALLOCATION */
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