/*

 ** 2001 September 15

 **

 ** 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.

 **

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

 **

 ** Memory allocation functions used throughout sqlite.

 **

 ** $Id: malloc.c,v 1.45 2008/10/12 00:27:53 shane Exp $

 */

 #include "sqliteInt.h"

 #include <stdarg.h>

 #include <ctype.h>

 /*

 ** This routine runs when the memory allocator sees that the

 ** total memory allocation is about to exceed the soft heap

 ** limit.

 */

 static void softHeapLimitEnforcer(

   void *NotUsed, 

   sqlite3_int64 inUse,

   int allocSize

 ){

   sqlite3_release_memory(allocSize);

 }

 /*

 ** Set the soft heap-size limit for the library. Passing a zero or 

 ** negative value indicates no limit.

 */

 void sqlite3_soft_heap_limit(int n){

   sqlite3_uint64 iLimit;

   int overage;

   if( n<0 ){

     iLimit = 0;

   }else{

     iLimit = n;

   }

   sqlite3_initialize();

   if( iLimit>0 ){

     sqlite3MemoryAlarm(softHeapLimitEnforcer, 0, iLimit);

   }else{

     sqlite3MemoryAlarm(0, 0, 0);

   }

   overage = sqlite3_memory_used() - n;

   if( overage>0 ){

     sqlite3_release_memory(overage);

   }

 }

 /*

 ** Attempt to release up to n bytes of non-essential memory currently

 ** held by SQLite. An example of non-essential memory is memory used to

 ** cache database pages that are not currently in use.

 */

 int sqlite3_release_memory(int n){

 #ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT

   int nRet = 0;

 #if 0

   nRet += sqlite3VdbeReleaseMemory(n);

 #endif

   nRet += sqlite3PcacheReleaseMemory(n-nRet);

   return nRet;

 #else

   return SQLITE_OK;

 #endif

 }

 /*

 ** State information local to the memory allocation subsystem.

 */

 static SQLITE_WSD struct Mem0Global {

   /* Number of free pages for scratch and page-cache memory */

   u32 nScratchFree;

   u32 nPageFree;

   sqlite3_mutex *mutex;         /* Mutex to serialize access */

   /*

   ** The alarm callback and its arguments.  The mem0.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;

   /*

   ** Pointers to the end of sqlite3GlobalConfig.pScratch and

   ** sqlite3GlobalConfig.pPage to a block of memory that records

   ** which pages are available.

   */

   u32 *aScratchFree;

   u32 *aPageFree;

 } mem0 = { 62560955 };

 #define mem0 GLOBAL(struct Mem0Global, mem0)

 /*

 ** Initialize the memory allocation subsystem.

 */

 int sqlite3MallocInit(void){

   if( sqlite3GlobalConfig.m.xMalloc==0 ){

     sqlite3MemSetDefault();

   }

   memset(&mem0, 0, sizeof(mem0));

   if( sqlite3GlobalConfig.bCoreMutex ){

     mem0.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM);

   }

   if( sqlite3GlobalConfig.pScratch && sqlite3GlobalConfig.szScratch>=100

       && sqlite3GlobalConfig.nScratch>=0 ){

     int i;

     sqlite3GlobalConfig.szScratch -= 4;

     mem0.aScratchFree = (u32*)&((char*)sqlite3GlobalConfig.pScratch)

                   [sqlite3GlobalConfig.szScratch*sqlite3GlobalConfig.nScratch];

     for(i=0; i<sqlite3GlobalConfig.nScratch; i++){ mem0.aScratchFree[i] = i; }

     mem0.nScratchFree = sqlite3GlobalConfig.nScratch;

   }else{

     sqlite3GlobalConfig.pScratch = 0;

     sqlite3GlobalConfig.szScratch = 0;

   }

   if( sqlite3GlobalConfig.pPage && sqlite3GlobalConfig.szPage>=512

       && sqlite3GlobalConfig.nPage>=1 ){

     int i;

     int overhead;

     int sz = sqlite3GlobalConfig.szPage;

     int n = sqlite3GlobalConfig.nPage;

     overhead = (4*n + sz - 1)/sz;

     sqlite3GlobalConfig.nPage -= overhead;

     mem0.aPageFree = (u32*)&((char*)sqlite3GlobalConfig.pPage)

                   [sqlite3GlobalConfig.szPage*sqlite3GlobalConfig.nPage];

     for(i=0; i<sqlite3GlobalConfig.nPage; i++){ mem0.aPageFree[i] = i; }

     mem0.nPageFree = sqlite3GlobalConfig.nPage;

   }else{

     sqlite3GlobalConfig.pPage = 0;

     sqlite3GlobalConfig.szPage = 0;

   }

   return sqlite3GlobalConfig.m.xInit(sqlite3GlobalConfig.m.pAppData);

 }

 /*

 ** Deinitialize the memory allocation subsystem.

 */

 void sqlite3MallocEnd(void){

   if( sqlite3GlobalConfig.m.xShutdown ){

   sqlite3GlobalConfig.m.xShutdown(sqlite3GlobalConfig.m.pAppData);

   }

   memset(&mem0, 0, sizeof(mem0));

 }

 /*

 ** Return the amount of memory currently checked out.

 */

 sqlite3_int64 sqlite3_memory_used(void){

   int n, mx;

   sqlite3_int64 res;

   sqlite3_status(SQLITE_STATUS_MEMORY_USED, &n, &mx, 0);

   res = (sqlite3_int64)n;  /* Work around bug in Borland C. Ticket #3216 */

   return res;

 }

 /*

 ** 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){

   int n, mx;

   sqlite3_int64 res;

   sqlite3_status(SQLITE_STATUS_MEMORY_USED, &n, &mx, resetFlag);

   res = (sqlite3_int64)mx;  /* Work around bug in Borland C. Ticket #3216 */

   return res;

 }

 /*

 ** Change the alarm callback

 */

 int sqlite3MemoryAlarm(

   void(*xCallback)(void *pArg, sqlite3_int64 used,int N),

   void *pArg,

   sqlite3_int64 iThreshold

 ){

   sqlite3_mutex_enter(mem0.mutex);

   mem0.alarmCallback = xCallback;

   mem0.alarmArg = pArg;

   mem0.alarmThreshold = iThreshold;

   sqlite3_mutex_leave(mem0.mutex);

   return SQLITE_OK;

 }

 #ifndef SQLITE_OMIT_DEPRECATED

 /*

 ** Deprecated external interface.  Internal/core SQLite code

 ** should call sqlite3MemoryAlarm.

 */

 int sqlite3_memory_alarm(

   void(*xCallback)(void *pArg, sqlite3_int64 used,int N),

   void *pArg,

   sqlite3_int64 iThreshold

 ){

   return sqlite3MemoryAlarm(xCallback, pArg, iThreshold);

 }

 #endif

 /*

 ** Trigger the alarm 

 */

 static void sqlite3MallocAlarm(int nByte){

   void (*xCallback)(void*,sqlite3_int64,int);

   sqlite3_int64 nowUsed;

   void *pArg;

   if( mem0.alarmCallback==0 || mem0.alarmBusy  ) return;

   mem0.alarmBusy = 1;

   xCallback = mem0.alarmCallback;

   nowUsed = sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED);

   pArg = mem0.alarmArg;

   sqlite3_mutex_leave(mem0.mutex);

   xCallback(pArg, nowUsed, nByte);

   sqlite3_mutex_enter(mem0.mutex);

   mem0.alarmBusy = 0;

 }

 /*

 ** Do a memory allocation with statistics and alarms.  Assume the

 ** lock is already held.

 */

 static int mallocWithAlarm(int n, void **pp){

   int nFull;

   void *p;

   assert( sqlite3_mutex_held(mem0.mutex) );

   nFull = sqlite3GlobalConfig.m.xRoundup(n);

   sqlite3StatusSet(SQLITE_STATUS_MALLOC_SIZE, n);

   if( mem0.alarmCallback!=0 ){

     int nUsed = sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED);

     if( nUsed+nFull >= mem0.alarmThreshold ){

       sqlite3MallocAlarm(nFull);

     }

   }

   p = sqlite3GlobalConfig.m.xMalloc(nFull);

   if( p==0 && mem0.alarmCallback ){

     sqlite3MallocAlarm(nFull);

     p = sqlite3GlobalConfig.m.xMalloc(nFull);

   }

   if( p ){

     nFull = sqlite3MallocSize(p);

     sqlite3StatusAdd(SQLITE_STATUS_MEMORY_USED, nFull);

   }

   *pp = p;

   return nFull;

 }

 /*

 ** Allocate memory.  This routine is like sqlite3_malloc() except that it

 ** assumes the memory subsystem has already been initialized.

 */

 void *sqlite3Malloc(int n){

   void *p;

   if( n<=0 ){

     p = 0;

   }else if( sqlite3GlobalConfig.bMemstat ){

     sqlite3_mutex_enter(mem0.mutex);

     mallocWithAlarm(n, &p);

     sqlite3_mutex_leave(mem0.mutex);

   }else{

     p = sqlite3GlobalConfig.m.xMalloc(n);

   }

   return p;

 }

 /*

 ** This version of the memory allocation is for use by the application.

 ** First make sure the memory subsystem is initialized, then do the

 ** allocation.

 */

 void *sqlite3_malloc(int n){

 #ifndef SQLITE_OMIT_AUTOINIT

   if( sqlite3_initialize() ) return 0;

 #endif

   return sqlite3Malloc(n);

 }

 /*

 ** Each thread may only have a single outstanding allocation from

 ** xScratchMalloc().  We verify this constraint in the single-threaded

 ** case by setting scratchAllocOut to 1 when an allocation

 ** is outstanding clearing it when the allocation is freed.

 */

 #if SQLITE_THREADSAFE==0 && !defined(NDEBUG)

 static int scratchAllocOut = 0;

 #endif

 /*

 ** Allocate memory that is to be used and released right away.

 ** This routine is similar to alloca() in that it is not intended

 ** for situations where the memory might be held long-term.  This

 ** routine is intended to get memory to old large transient data

 ** structures that would not normally fit on the stack of an

 ** embedded processor.

 */

 void *sqlite3ScratchMalloc(int n){

   void *p;

   assert( n>0 );

 #if SQLITE_THREADSAFE==0 && !defined(NDEBUG)

   /* Verify that no more than one scratch allocation per thread

   ** is outstanding at one time.  (This is only checked in the

   ** single-threaded case since checking in the multi-threaded case

   ** would be much more complicated.) */

   assert( scratchAllocOut==0 );

 #endif

   if( sqlite3GlobalConfig.szScratch<n ){

     goto scratch_overflow;

   }else{  

     sqlite3_mutex_enter(mem0.mutex);

     if( mem0.nScratchFree==0 ){

       sqlite3_mutex_leave(mem0.mutex);

       goto scratch_overflow;

     }else{

       int i;

       i = mem0.aScratchFree[--mem0.nScratchFree];

       i *= sqlite3GlobalConfig.szScratch;

       sqlite3StatusAdd(SQLITE_STATUS_SCRATCH_USED, 1);

       sqlite3StatusSet(SQLITE_STATUS_SCRATCH_SIZE, n);

       sqlite3_mutex_leave(mem0.mutex);

       p = (void*)&((char*)sqlite3GlobalConfig.pScratch)[i];

     }

   }

 #if SQLITE_THREADSAFE==0 && !defined(NDEBUG)

   scratchAllocOut = p!=0;

 #endif

   return p;

 scratch_overflow:

   if( sqlite3GlobalConfig.bMemstat ){

     sqlite3_mutex_enter(mem0.mutex);

     sqlite3StatusSet(SQLITE_STATUS_SCRATCH_SIZE, n);

     n = mallocWithAlarm(n, &p);

     if( p ) sqlite3StatusAdd(SQLITE_STATUS_SCRATCH_OVERFLOW, n);

     sqlite3_mutex_leave(mem0.mutex);

   }else{

     p = sqlite3GlobalConfig.m.xMalloc(n);

   }

 #if SQLITE_THREADSAFE==0 && !defined(NDEBUG)

   scratchAllocOut = p!=0;

 #endif

   return p;    

 }

 void sqlite3ScratchFree(void *p){

   if( p ){

 #if SQLITE_THREADSAFE==0 && !defined(NDEBUG)

     /* Verify that no more than one scratch allocation per thread

     ** is outstanding at one time.  (This is only checked in the

     ** single-threaded case since checking in the multi-threaded case

     ** would be much more complicated.) */

     assert( scratchAllocOut==1 );

     scratchAllocOut = 0;

 #endif

     if( sqlite3GlobalConfig.pScratch==0

            || p<sqlite3GlobalConfig.pScratch

            || p>=(void*)mem0.aScratchFree ){

       if( sqlite3GlobalConfig.bMemstat ){

         int iSize = sqlite3MallocSize(p);

         sqlite3_mutex_enter(mem0.mutex);

         sqlite3StatusAdd(SQLITE_STATUS_SCRATCH_OVERFLOW, -iSize);

         sqlite3StatusAdd(SQLITE_STATUS_MEMORY_USED, -iSize);

         sqlite3GlobalConfig.m.xFree(p);

         sqlite3_mutex_leave(mem0.mutex);

       }else{

         sqlite3GlobalConfig.m.xFree(p);

       }

     }else{

       int i;

       i = (u8 *)p - (u8 *)sqlite3GlobalConfig.pScratch;

       i /= sqlite3GlobalConfig.szScratch;

       assert( i>=0 && i<sqlite3GlobalConfig.nScratch );

       sqlite3_mutex_enter(mem0.mutex);

       assert( mem0.nScratchFree<sqlite3GlobalConfig.nScratch );

       mem0.aScratchFree[mem0.nScratchFree++] = i;

       sqlite3StatusAdd(SQLITE_STATUS_SCRATCH_USED, -1);

       sqlite3_mutex_leave(mem0.mutex);

     }

   }

 }

 /*

 ** Allocate memory to be used by the page cache.  Make use of the

 ** memory buffer provided by SQLITE_CONFIG_PAGECACHE if there is one

 ** and that memory is of the right size and is not completely

 ** consumed.  Otherwise, failover to sqlite3Malloc().

 */

 #if 0

 void *sqlite3PageMalloc(int n){

   void *p;

   assert( n>0 );

   assert( (n & (n-1))==0 );

   assert( n>=512 && n<=32768 );

   if( sqlite3GlobalConfig.szPage<n ){

     goto page_overflow;

   }else{  

     sqlite3_mutex_enter(mem0.mutex);

     if( mem0.nPageFree==0 ){

       sqlite3_mutex_leave(mem0.mutex);

       goto page_overflow;

     }else{

       int i;

       i = mem0.aPageFree[--mem0.nPageFree];

       sqlite3_mutex_leave(mem0.mutex);

       i *= sqlite3GlobalConfig.szPage;

       sqlite3StatusSet(SQLITE_STATUS_PAGECACHE_SIZE, n);

       sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_USED, 1);

       p = (void*)&((char*)sqlite3GlobalConfig.pPage)[i];

     }

   }

   return p;

 page_overflow:

   if( sqlite3GlobalConfig.bMemstat ){

     sqlite3_mutex_enter(mem0.mutex);

     sqlite3StatusSet(SQLITE_STATUS_PAGECACHE_SIZE, n);

     n = mallocWithAlarm(n, &p);

     if( p ) sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_OVERFLOW, n);

     sqlite3_mutex_leave(mem0.mutex);

   }else{

     p = sqlite3GlobalConfig.m.xMalloc(n);

   }

   return p;    

 }

 void sqlite3PageFree(void *p){

   if( p ){

     if( sqlite3GlobalConfig.pPage==0

            || p<sqlite3GlobalConfig.pPage

            || p>=(void*)mem0.aPageFree ){

       /* In this case, the page allocation was obtained from a regular 

       ** call to sqlite3_mem_methods.xMalloc() (a page-cache-memory 

       ** "overflow"). Free the block with sqlite3_mem_methods.xFree().

       */

       if( sqlite3GlobalConfig.bMemstat ){

         int iSize = sqlite3MallocSize(p);

         sqlite3_mutex_enter(mem0.mutex);

         sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_OVERFLOW, -iSize);

         sqlite3StatusAdd(SQLITE_STATUS_MEMORY_USED, -iSize);

         sqlite3GlobalConfig.m.xFree(p);

         sqlite3_mutex_leave(mem0.mutex);

       }else{

         sqlite3GlobalConfig.m.xFree(p);

       }

     }else{

       /* The page allocation was allocated from the sqlite3GlobalConfig.pPage

       ** buffer. In this case all that is add the index of the page in

       ** the sqlite3GlobalConfig.pPage array to the set of free indexes stored

       ** in the mem0.aPageFree[] array.

       */

       int i;

       i = (u8 *)p - (u8 *)sqlite3GlobalConfig.pPage;

       i /= sqlite3GlobalConfig.szPage;

       assert( i>=0 && i<sqlite3GlobalConfig.nPage );

       sqlite3_mutex_enter(mem0.mutex);

       assert( mem0.nPageFree<sqlite3GlobalConfig.nPage );

       mem0.aPageFree[mem0.nPageFree++] = i;

       sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_USED, -1);

       sqlite3_mutex_leave(mem0.mutex);

 #if !defined(NDEBUG) && 0

       /* Assert that a duplicate was not just inserted into aPageFree[]. */

       for(i=0; i<mem0.nPageFree-1; i++){

         assert( mem0.aPageFree[i]!=mem0.aPageFree[mem0.nPageFree-1] );

       }

 #endif

     }

   }

 }

 #endif

 /*

 ** TRUE if p is a lookaside memory allocation from db

 */

 #ifndef SQLITE_OMIT_LOOKASIDE

 static int isLookaside(sqlite3 *db, void *p){

   return db && p && p>=db->lookaside.pStart && p<db->lookaside.pEnd;

 }

 #else

 #define isLookaside(A,B) 0

 #endif

 /*

 ** Return the size of a memory allocation previously obtained from

 ** sqlite3Malloc() or sqlite3_malloc().

 */

 int sqlite3MallocSize(void *p){

   return sqlite3GlobalConfig.m.xSize(p);

 }

 int sqlite3DbMallocSize(sqlite3 *db, void *p){

   if( isLookaside(db, p) ){

     return db->lookaside.sz;

   }else{

     return sqlite3GlobalConfig.m.xSize(p);

   }

 }

 /*

 ** Free memory previously obtained from sqlite3Malloc().

 */

 void sqlite3_free(void *p){

   if( p==0 ) return;

   if( sqlite3GlobalConfig.bMemstat ){

     sqlite3_mutex_enter(mem0.mutex);

     sqlite3StatusAdd(SQLITE_STATUS_MEMORY_USED, -sqlite3MallocSize(p));

     sqlite3GlobalConfig.m.xFree(p);

     sqlite3_mutex_leave(mem0.mutex);

   }else{

     sqlite3GlobalConfig.m.xFree(p);

   }

 }

 /*

 ** Free memory that might be associated with a particular database

 ** connection.

 */

 void sqlite3DbFree(sqlite3 *db, void *p){

   if( isLookaside(db, p) ){

     LookasideSlot *pBuf = (LookasideSlot*)p;

     pBuf->pNext = db->lookaside.pFree;

     db->lookaside.pFree = pBuf;

     db->lookaside.nOut--;

   }else{

     sqlite3_free(p);

   }

 }

 /*

 ** Change the size of an existing memory allocation

 */

 void *sqlite3Realloc(void *pOld, int nBytes){

   int nOld, nNew;

   void *pNew;

   if( pOld==0 ){

     return sqlite3Malloc(nBytes);

   }

   if( nBytes<=0 ){

     sqlite3_free(pOld);

     return 0;

   }

   nOld = sqlite3MallocSize(pOld);

   if( sqlite3GlobalConfig.bMemstat ){

     sqlite3_mutex_enter(mem0.mutex);

     sqlite3StatusSet(SQLITE_STATUS_MALLOC_SIZE, nBytes);

     nNew = sqlite3GlobalConfig.m.xRoundup(nBytes);

     if( nOld==nNew ){

       pNew = pOld;

     }else{

       if( sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED)+nNew-nOld >= 

             mem0.alarmThreshold ){

         sqlite3MallocAlarm(nNew-nOld);

       }

       pNew = sqlite3GlobalConfig.m.xRealloc(pOld, nNew);

       if( pNew==0 && mem0.alarmCallback ){

         sqlite3MallocAlarm(nBytes);

         pNew = sqlite3GlobalConfig.m.xRealloc(pOld, nNew);

       }

       if( pNew ){

         nNew = sqlite3MallocSize(pNew);

         sqlite3StatusAdd(SQLITE_STATUS_MEMORY_USED, nNew-nOld);

       }

     }

     sqlite3_mutex_leave(mem0.mutex);

   }else{

     pNew = sqlite3GlobalConfig.m.xRealloc(pOld, nBytes);

   }

   return pNew;

 }

 /*

 ** The public interface to sqlite3Realloc.  Make sure that the memory

 ** subsystem is initialized prior to invoking sqliteRealloc.

 */

 void *sqlite3_realloc(void *pOld, int n){

 #ifndef SQLITE_OMIT_AUTOINIT

   if( sqlite3_initialize() ) return 0;

 #endif

   return sqlite3Realloc(pOld, n);

 }

 /*

 ** Allocate and zero memory.

 */ 

 void *sqlite3MallocZero(int n){

   void *p = sqlite3Malloc(n);

   if( p ){

     memset(p, 0, n);

   }

   return p;

 }

 /*

 ** Allocate and zero memory.  If the allocation fails, make

 ** the mallocFailed flag in the connection pointer.

 */

 void *sqlite3DbMallocZero(sqlite3 *db, int n){

   void *p = sqlite3DbMallocRaw(db, n);

   if( p ){

     memset(p, 0, n);

   }

   return p;

 }

 /*

 ** Allocate and zero memory.  If the allocation fails, make

 ** the mallocFailed flag in the connection pointer.

 **

 ** If db!=0 and db->mallocFailed is true (indicating a prior malloc

 ** failure on the same database connection) then always return 0.

 ** Hence for a particular database connection, once malloc starts

 ** failing, it fails consistently until mallocFailed is reset.

 ** This is an important assumption.  There are many places in the

 ** code that do things like this:

 **

 **         int *a = (int*)sqlite3DbMallocRaw(db, 100);

 **         int *b = (int*)sqlite3DbMallocRaw(db, 200);

 **         if( b ) a[10] = 9;

 **

 ** In other words, if a subsequent malloc (ex: "b") worked, it is assumed

 ** that all prior mallocs (ex: "a") worked too.

 */

 void *sqlite3DbMallocRaw(sqlite3 *db, int n){

   void *p;

 #ifndef SQLITE_OMIT_LOOKASIDE

   if( db ){

     LookasideSlot *pBuf;

     if( db->mallocFailed ){

       return 0;

     }

     if( db->lookaside.bEnabled && n<=db->lookaside.sz

          && (pBuf = db->lookaside.pFree)!=0 ){

       db->lookaside.pFree = pBuf->pNext;

       db->lookaside.nOut++;

       if( db->lookaside.nOut>db->lookaside.mxOut ){

         db->lookaside.mxOut = db->lookaside.nOut;

       }

       return (void*)pBuf;

     }

   }

 #else

   if( db && db->mallocFailed ){

     return 0;

   }

 #endif

   p = sqlite3Malloc(n);

   if( !p && db ){

     db->mallocFailed = 1;

   }

   return p;

 }

 /*

 ** Resize the block of memory pointed to by p to n bytes. If the

 ** resize fails, set the mallocFailed flag in the connection object.

 */

 void *sqlite3DbRealloc(sqlite3 *db, void *p, int n){

   void *pNew = 0;

   if( db->mallocFailed==0 ){

     if( p==0 ){

       return sqlite3DbMallocRaw(db, n);

     }

     if( isLookaside(db, p) ){

       if( n<=db->lookaside.sz ){

         return p;

       }

       pNew = sqlite3DbMallocRaw(db, n);

       if( pNew ){

         memcpy(pNew, p, db->lookaside.sz);

         sqlite3DbFree(db, p);

       }

     }else{

       pNew = sqlite3_realloc(p, n);

       if( !pNew ){

         db->mallocFailed = 1;

       }

     }

   }

   return pNew;

 }

 /*

 ** Attempt to reallocate p.  If the reallocation fails, then free p

 ** and set the mallocFailed flag in the database connection.

 */

 void *sqlite3DbReallocOrFree(sqlite3 *db, void *p, int n){

   void *pNew;

   pNew = sqlite3DbRealloc(db, p, n);

   if( !pNew ){

     sqlite3DbFree(db, p);

   }

   return pNew;

 }

 /*

 ** Make a copy of a string in memory obtained from sqliteMalloc(). These 

 ** functions call sqlite3MallocRaw() directly instead of sqliteMalloc(). This

 ** is because when memory debugging is turned on, these two functions are 

 ** called via macros that record the current file and line number in the

 ** ThreadData structure.

 */

 char *sqlite3DbStrDup(sqlite3 *db, const char *z){

   char *zNew;

   size_t n;

   if( z==0 ){

     return 0;

   }

   n = strlen(z)+1;

   assert( (n&0x7fffffff)==n );

   zNew = sqlite3DbMallocRaw(db, (int)n);

   if( zNew ){

     memcpy(zNew, z, n);

   }

   return zNew;

 }

 char *sqlite3DbStrNDup(sqlite3 *db, const char *z, int n){

   char *zNew;

   if( z==0 ){

     return 0;

   }

   assert( (n&0x7fffffff)==n );

   zNew = sqlite3DbMallocRaw(db, n+1);

   if( zNew ){

     memcpy(zNew, z, n);

     zNew[n] = 0;

   }

   return zNew;

 }

 /*

 ** Create a string from the zFromat argument and the va_list that follows.

 ** Store the string in memory obtained from sqliteMalloc() and make *pz

 ** point to that string.

 */

 void sqlite3SetString(char **pz, sqlite3 *db, const char *zFormat, ...){

   va_list ap;

   char *z;

   va_start(ap, zFormat);

   z = sqlite3VMPrintf(db, zFormat, ap);

   va_end(ap);

   sqlite3DbFree(db, *pz);

   *pz = z;

 }

 /*

 ** This function must be called before exiting any API function (i.e. 

 ** returning control to the user) that has called sqlite3_malloc or

 ** sqlite3_realloc.

 **

 ** The returned value is normally a copy of the second argument to this

 ** function. However, if a malloc() failure has occured since the previous

 ** invocation SQLITE_NOMEM is returned instead. 

 **

 ** If the first argument, db, is not NULL and a malloc() error has occured,

 ** then the connection error-code (the value returned by sqlite3_errcode())

 ** is set to SQLITE_NOMEM.

 */

 int sqlite3ApiExit(sqlite3* db, int rc){

   /* If the db handle is not NULL, then we must hold the connection handle

   ** mutex here. Otherwise the read (and possible write) of db->mallocFailed 

   ** is unsafe, as is the call to sqlite3Error().

   */

   assert( !db || sqlite3_mutex_held(db->mutex) );

   if( db && (db->mallocFailed || rc==SQLITE_IOERR_NOMEM) ){

     sqlite3Error(db, SQLITE_NOMEM, 0);

     db->mallocFailed = 0;

     rc = SQLITE_NOMEM;

   }

   return rc & (db ? db->errMask : 0xff);

 }