dvander@1645: /*
dvander@1645: ** 2007 August 14
dvander@1645: **
dvander@1645: ** The author disclaims copyright to this source code.  In place of
dvander@1645: ** a legal notice, here is a blessing:
dvander@1645: **
dvander@1645: **    May you do good and not evil.
dvander@1645: **    May you find forgiveness for yourself and forgive others.
dvander@1645: **    May you share freely, never taking more than you give.
dvander@1645: **
dvander@1645: *************************************************************************
dvander@1645: ** This file contains the C functions that implement a memory
dvander@1645: ** allocation subsystem for use by SQLite.  
dvander@1645: **
dvander@1645: ** $Id$
dvander@1645: */
dvander@1645: 
dvander@1645: /*
dvander@1645: ** This version of the memory allocator is the default.  It is
dvander@1645: ** used when no other memory allocator is specified using compile-time
dvander@1645: ** macros.
dvander@1645: */
dvander@1645: #if !defined(SQLITE_MEMDEBUG) && !defined(SQLITE_OMIT_MEMORY_ALLOCATION)
dvander@1645: 
dvander@1645: /*
dvander@1645: ** We will eventually construct multiple memory allocation subsystems
dvander@1645: ** suitable for use in various contexts:
dvander@1645: **
dvander@1645: **    *  Normal multi-threaded builds
dvander@1645: **    *  Normal single-threaded builds
dvander@1645: **    *  Debugging builds
dvander@1645: **
dvander@1645: ** This initial version is suitable for use in normal multi-threaded
dvander@1645: ** builds.  We envision that alternative versions will be stored in
dvander@1645: ** separate source files.  #ifdefs will be used to select the code from
dvander@1645: ** one of the various memN.c source files for use in any given build.
dvander@1645: */
dvander@1645: #include "sqliteInt.h"
dvander@1645: 
dvander@1645: /*
dvander@1645: ** All of the static variables used by this module are collected
dvander@1645: ** into a single structure named "mem".  This is to keep the
dvander@1645: ** static variables organized and to reduce namespace pollution
dvander@1645: ** when this module is combined with other in the amalgamation.
dvander@1645: */
dvander@1645: static struct {
dvander@1645:   /*
dvander@1645:   ** The alarm callback and its arguments.  The mem.mutex lock will
dvander@1645:   ** be held while the callback is running.  Recursive calls into
dvander@1645:   ** the memory subsystem are allowed, but no new callbacks will be
dvander@1645:   ** issued.  The alarmBusy variable is set to prevent recursive
dvander@1645:   ** callbacks.
dvander@1645:   */
dvander@1645:   sqlite3_int64 alarmThreshold;
dvander@1645:   void (*alarmCallback)(void*, sqlite3_int64,int);
dvander@1645:   void *alarmArg;
dvander@1645:   int alarmBusy;
dvander@1645:   
dvander@1645:   /*
dvander@1645:   ** Mutex to control access to the memory allocation subsystem.
dvander@1645:   */
dvander@1645:   sqlite3_mutex *mutex;
dvander@1645:   
dvander@1645:   /*
dvander@1645:   ** Current allocation and high-water mark.
dvander@1645:   */
dvander@1645:   sqlite3_int64 nowUsed;
dvander@1645:   sqlite3_int64 mxUsed;
dvander@1645:   
dvander@1645:  
dvander@1645: } mem;
dvander@1645: 
dvander@1645: /*
dvander@1645: ** Enter the mutex mem.mutex. Allocate it if it is not already allocated.
dvander@1645: */
dvander@1645: static void enterMem(void){
dvander@1645:   if( mem.mutex==0 ){
dvander@1645:     mem.mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MEM);
dvander@1645:   }
dvander@1645:   sqlite3_mutex_enter(mem.mutex);
dvander@1645: }
dvander@1645: 
dvander@1645: /*
dvander@1645: ** Return the amount of memory currently checked out.
dvander@1645: */
dvander@1645: sqlite3_int64 sqlite3_memory_used(void){
dvander@1645:   sqlite3_int64 n;
dvander@1645:   enterMem();
dvander@1645:   n = mem.nowUsed;
dvander@1645:   sqlite3_mutex_leave(mem.mutex);  
dvander@1645:   return n;
dvander@1645: }
dvander@1645: 
dvander@1645: /*
dvander@1645: ** Return the maximum amount of memory that has ever been
dvander@1645: ** checked out since either the beginning of this process
dvander@1645: ** or since the most recent reset.
dvander@1645: */
dvander@1645: sqlite3_int64 sqlite3_memory_highwater(int resetFlag){
dvander@1645:   sqlite3_int64 n;
dvander@1645:   enterMem();
dvander@1645:   n = mem.mxUsed;
dvander@1645:   if( resetFlag ){
dvander@1645:     mem.mxUsed = mem.nowUsed;
dvander@1645:   }
dvander@1645:   sqlite3_mutex_leave(mem.mutex);  
dvander@1645:   return n;
dvander@1645: }
dvander@1645: 
dvander@1645: /*
dvander@1645: ** Change the alarm callback
dvander@1645: */
dvander@1645: int sqlite3_memory_alarm(
dvander@1645:   void(*xCallback)(void *pArg, sqlite3_int64 used,int N),
dvander@1645:   void *pArg,
dvander@1645:   sqlite3_int64 iThreshold
dvander@1645: ){
dvander@1645:   enterMem();
dvander@1645:   mem.alarmCallback = xCallback;
dvander@1645:   mem.alarmArg = pArg;
dvander@1645:   mem.alarmThreshold = iThreshold;
dvander@1645:   sqlite3_mutex_leave(mem.mutex);
dvander@1645:   return SQLITE_OK;
dvander@1645: }
dvander@1645: 
dvander@1645: /*
dvander@1645: ** Trigger the alarm 
dvander@1645: */
dvander@1645: static void sqlite3MemsysAlarm(int nByte){
dvander@1645:   void (*xCallback)(void*,sqlite3_int64,int);
dvander@1645:   sqlite3_int64 nowUsed;
dvander@1645:   void *pArg;
dvander@1645:   if( mem.alarmCallback==0 || mem.alarmBusy  ) return;
dvander@1645:   mem.alarmBusy = 1;
dvander@1645:   xCallback = mem.alarmCallback;
dvander@1645:   nowUsed = mem.nowUsed;
dvander@1645:   pArg = mem.alarmArg;
dvander@1645:   sqlite3_mutex_leave(mem.mutex);
dvander@1645:   xCallback(pArg, nowUsed, nByte);
dvander@1645:   sqlite3_mutex_enter(mem.mutex);
dvander@1645:   mem.alarmBusy = 0;
dvander@1645: }
dvander@1645: 
dvander@1645: /*
dvander@1645: ** Allocate nBytes of memory
dvander@1645: */
dvander@1645: void *sqlite3_malloc(int nBytes){
dvander@1645:   sqlite3_int64 *p = 0;
dvander@1645:   if( nBytes>0 ){
dvander@1645:     enterMem();
dvander@1645:     if( mem.alarmCallback!=0 && mem.nowUsed+nBytes>=mem.alarmThreshold ){
dvander@1645:       sqlite3MemsysAlarm(nBytes);
dvander@1645:     }
dvander@1645:     p = malloc(nBytes+8);
dvander@1645:     if( p==0 ){
dvander@1645:       sqlite3MemsysAlarm(nBytes);
dvander@1645:       p = malloc(nBytes+8);
dvander@1645:     }
dvander@1645:     if( p ){
dvander@1645:       p[0] = nBytes;
dvander@1645:       p++;
dvander@1645:       mem.nowUsed += nBytes;
dvander@1645:       if( mem.nowUsed>mem.mxUsed ){
dvander@1645:         mem.mxUsed = mem.nowUsed;
dvander@1645:       }
dvander@1645:     }
dvander@1645:     sqlite3_mutex_leave(mem.mutex);
dvander@1645:   }
dvander@1645:   return (void*)p; 
dvander@1645: }
dvander@1645: 
dvander@1645: /*
dvander@1645: ** Free memory.
dvander@1645: */
dvander@1645: void sqlite3_free(void *pPrior){
dvander@1645:   sqlite3_int64 *p;
dvander@1645:   int nByte;
dvander@1645:   if( pPrior==0 ){
dvander@1645:     return;
dvander@1645:   }
dvander@1645:   assert( mem.mutex!=0 );
dvander@1645:   p = pPrior;
dvander@1645:   p--;
dvander@1645:   nByte = (int)*p;
dvander@1645:   sqlite3_mutex_enter(mem.mutex);
dvander@1645:   mem.nowUsed -= nByte;
dvander@1645:   free(p);
dvander@1645:   sqlite3_mutex_leave(mem.mutex);  
dvander@1645: }
dvander@1645: 
dvander@1645: /*
dvander@1645: ** Change the size of an existing memory allocation
dvander@1645: */
dvander@1645: void *sqlite3_realloc(void *pPrior, int nBytes){
dvander@1645:   int nOld;
dvander@1645:   sqlite3_int64 *p;
dvander@1645:   if( pPrior==0 ){
dvander@1645:     return sqlite3_malloc(nBytes);
dvander@1645:   }
dvander@1645:   if( nBytes<=0 ){
dvander@1645:     sqlite3_free(pPrior);
dvander@1645:     return 0;
dvander@1645:   }
dvander@1645:   p = pPrior;
dvander@1645:   p--;
dvander@1645:   nOld = (int)p[0];
dvander@1645:   assert( mem.mutex!=0 );
dvander@1645:   sqlite3_mutex_enter(mem.mutex);
dvander@1645:   if( mem.nowUsed+nBytes-nOld>=mem.alarmThreshold ){
dvander@1645:     sqlite3MemsysAlarm(nBytes-nOld);
dvander@1645:   }
dvander@1645:   p = realloc(p, nBytes+8);
dvander@1645:   if( p==0 ){
dvander@1645:     sqlite3MemsysAlarm(nBytes);
dvander@1645:     p = realloc(p, nBytes+8);
dvander@1645:   }
dvander@1645:   if( p ){
dvander@1645:     p[0] = nBytes;
dvander@1645:     p++;
dvander@1645:     mem.nowUsed += nBytes-nOld;
dvander@1645:     if( mem.nowUsed>mem.mxUsed ){
dvander@1645:       mem.mxUsed = mem.nowUsed;
dvander@1645:     }
dvander@1645:   }
dvander@1645:   sqlite3_mutex_leave(mem.mutex);
dvander@1645:   return (void*)p;
dvander@1645: }
dvander@1645: 
dvander@1645: #endif /* !SQLITE_MEMDEBUG && !SQLITE_OMIT_MEMORY_ALLOCATION */