/*

** 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 1.34 2008/08/05 17:53:23 drh 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 ){

    sqlite3_memory_alarm(softHeapLimitEnforcer, 0, iLimit);

  }else{

    sqlite3_memory_alarm(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 = sqlite3VdbeReleaseMemory(n);

  nRet += sqlite3PagerReleaseMemory(n-nRet);

  return nRet;

#else

  return SQLITE_OK;

#endif

}

/*

** State information local to the memory allocation subsystem.

*/

static struct {

  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 sqlite3Config.pScratch and

  ** sqlite3Config.pPage to a block of memory that records

  ** which pages are available.

  */

  u32 *aScratchFree;

  u32 *aPageFree;

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

  u32 nScratchFree;

  u32 nPageFree;

} mem0;

/*

** Initialize the memory allocation subsystem.

*/

int sqlite3MallocInit(void){

  if( sqlite3Config.m.xMalloc==0 ){

    sqlite3MemSetDefault();

  }

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

  if( sqlite3Config.bCoreMutex ){

    mem0.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM);

  }

  if( sqlite3Config.pScratch && sqlite3Config.szScratch>=100

      && sqlite3Config.nScratch>=0 ){

    int i;

    sqlite3Config.szScratch -= 4;

    mem0.aScratchFree = (u32*)&((char*)sqlite3Config.pScratch)

                  [sqlite3Config.szScratch*sqlite3Config.nScratch];

    for(i=0; i<sqlite3Config.nScratch; i++){ mem0.aScratchFree[i] = i; }

    mem0.nScratchFree = sqlite3Config.nScratch;

  }else{

    sqlite3Config.pScratch = 0;

    sqlite3Config.szScratch = 0;

  }

  if( sqlite3Config.pPage && sqlite3Config.szPage>=512

      && sqlite3Config.nPage>=1 ){

    int i;

    int overhead;

    int sz = sqlite3Config.szPage;

    int n = sqlite3Config.nPage;

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

    sqlite3Config.nPage -= overhead;

    mem0.aPageFree = (u32*)&((char*)sqlite3Config.pPage)

                  [sqlite3Config.szPage*sqlite3Config.nPage];

    for(i=0; i<sqlite3Config.nPage; i++){ mem0.aPageFree[i] = i; }

    mem0.nPageFree = sqlite3Config.nPage;

  }else{

    sqlite3Config.pPage = 0;

    sqlite3Config.szPage = 0;

  }

  return sqlite3Config.m.xInit(sqlite3Config.m.pAppData);

}

/*

** Deinitialize the memory allocation subsystem.

*/

void sqlite3MallocEnd(void){

  sqlite3Config.m.xShutdown(sqlite3Config.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 sqlite3_memory_alarm(

  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;

}

/*

** 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 = sqlite3Config.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 = sqlite3Config.m.xMalloc(nFull);

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

    sqlite3MallocAlarm(nFull);

    p = sqlite3Config.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( sqlite3Config.bMemstat ){

    sqlite3_mutex_enter(mem0.mutex);

    mallocWithAlarm(n, &p);

    sqlite3_mutex_leave(mem0.mutex);

  }else{

    p = sqlite3Config.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( sqlite3Config.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];

      sqlite3_mutex_leave(mem0.mutex);

      i *= sqlite3Config.szScratch;

      sqlite3StatusAdd(SQLITE_STATUS_SCRATCH_USED, 1);

      sqlite3StatusSet(SQLITE_STATUS_SCRATCH_SIZE, n);

      p = (void*)&((char*)sqlite3Config.pScratch)[i];

    }

  }

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

  scratchAllocOut = p!=0;

#endif

  return p;

scratch_overflow:

  if( sqlite3Config.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 = sqlite3Config.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( sqlite3Config.pScratch==0

           || p<sqlite3Config.pScratch

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

      if( sqlite3Config.bMemstat ){

        int iSize = sqlite3MallocSize(p);

        sqlite3_mutex_enter(mem0.mutex);

        sqlite3StatusAdd(SQLITE_STATUS_SCRATCH_OVERFLOW, -iSize);

        sqlite3StatusAdd(SQLITE_STATUS_MEMORY_USED, -iSize);

        sqlite3Config.m.xFree(p);

        sqlite3_mutex_leave(mem0.mutex);

      }else{

        sqlite3Config.m.xFree(p);

      }

    }else{

      int i;

      i = (u8 *)p - (u8 *)sqlite3Config.pScratch;

      i /= sqlite3Config.szScratch;

      assert( i>=0 && i<sqlite3Config.nScratch );

      sqlite3_mutex_enter(mem0.mutex);

      assert( mem0.nScratchFree<sqlite3Config.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().

*/

void *sqlite3PageMalloc(int n){

  void *p;

  assert( n>0 );

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

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

  if( sqlite3Config.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 *= sqlite3Config.szPage;

      sqlite3StatusSet(SQLITE_STATUS_PAGECACHE_SIZE, n);

      sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_USED, 1);

      p = (void*)&((char*)sqlite3Config.pPage)[i];

    }

  }

  return p;

page_overflow:

  if( sqlite3Config.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 = sqlite3Config.m.xMalloc(n);

  }

  return p;    

}

void sqlite3PageFree(void *p){

  if( p ){

    if( sqlite3Config.pPage==0

           || p<sqlite3Config.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( sqlite3Config.bMemstat ){

        int iSize = sqlite3MallocSize(p);

        sqlite3_mutex_enter(mem0.mutex);

        sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_OVERFLOW, -iSize);

        sqlite3StatusAdd(SQLITE_STATUS_MEMORY_USED, -iSize);

        sqlite3Config.m.xFree(p);

        sqlite3_mutex_leave(mem0.mutex);

      }else{

        sqlite3Config.m.xFree(p);

      }

    }else{

      /* The page allocation was allocated from the sqlite3Config.pPage

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

      ** the sqlite3Config.pPage array to the set of free indexes stored

      ** in the mem0.aPageFree[] array.

      */

      int i;

      i = (u8 *)p - (u8 *)sqlite3Config.pPage;

      i /= sqlite3Config.szPage;

      assert( i>=0 && i<sqlite3Config.nPage );

      sqlite3_mutex_enter(mem0.mutex);

      assert( mem0.nPageFree<sqlite3Config.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

    }

  }

}

/*

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

*/

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

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

}

/*

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

** sqlite3Malloc() or sqlite3_malloc().

*/

int sqlite3MallocSize(void *p){

  return sqlite3Config.m.xSize(p);

}

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

  if( isLookaside(db, p) ){

    return db->lookaside.sz;

  }else{

    return sqlite3Config.m.xSize(p);

  }

}

/*

** Free memory previously obtained from sqlite3Malloc().

*/

void sqlite3_free(void *p){

  if( p==0 ) return;

  if( sqlite3Config.bMemstat ){

    sqlite3_mutex_enter(mem0.mutex);

    sqlite3StatusAdd(SQLITE_STATUS_MEMORY_USED, -sqlite3MallocSize(p));

    sqlite3Config.m.xFree(p);

    sqlite3_mutex_leave(mem0.mutex);

  }else{

    sqlite3Config.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( sqlite3Config.bMemstat ){

    sqlite3_mutex_enter(mem0.mutex);

    sqlite3StatusSet(SQLITE_STATUS_MALLOC_SIZE, nBytes);

    nNew = sqlite3Config.m.xRoundup(nBytes);

    if( nOld==nNew ){

      pNew = pOld;

    }else{

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

            mem0.alarmThreshold ){

        sqlite3MallocAlarm(nNew-nOld);

      }

      pNew = sqlite3Config.m.xRealloc(pOld, nNew);

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

        sqlite3MallocAlarm(nBytes);

        pNew = sqlite3Config.m.xRealloc(pOld, nNew);

      }

      if( pNew ){

        nNew = sqlite3MallocSize(pNew);

        sqlite3StatusAdd(SQLITE_STATUS_MEMORY_USED, nNew-nOld);

      }

    }

    sqlite3_mutex_leave(mem0.mutex);

  }else{

    pNew = sqlite3Config.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.

*/

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

  void *p;

  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;

    }

  }

  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 ){

    sqlite3Error(db, SQLITE_NOMEM, 0);

    db->mallocFailed = 0;

    rc = SQLITE_NOMEM;

  }

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

}