SQLite

  int (*xIsDirWritable)(char*);
  int (*xSyncDirectory)(const char*);
  int (*xTempFileName)(char*);

  int  (*xRandomSeed)(char*);
  int  (*xSleep)(int ms);
  int  (*xCurrentTime)(double*);

  void (*xEnterMutex)(void);
  void (*xLeaveMutex)(void);
  void *(*xThreadSpecificData)(int);

  void *(*xMalloc)(int);
  void *(*xRealloc)(void *, int);
  void (*xFree)(void *);
  int (*xAllocationSize)(void *);
} sqlite3Os;


/*
** The semi-published API for setting and getting methods from the 
** global sqlite3OsVtbl structure. Neither sqlite3_os_routine_XXX() function
** is intriniscally thread-safe.

*/
#ifdef SQLITE_TEST
int sqlite3_open_file_count = 0;
#define OpenCounter(X)  sqlite3_open_file_count+=(X)
#else
#define OpenCounter(X)
#endif

/*
** genericMalloc
** genericRealloc
** genericOsFree
** genericAllocationSize
**
** Implementation of the os level dynamic memory allocation interface in terms
** of the standard malloc(), realloc() and free() found in many operating
** systems. No rocket science here.
*/
static void *genericMalloc(int n){
  char *p = (char *)malloc(n+8);
  assert(n>0);
  assert(sizeof(int)<=8);
  if( p ){
    *(int *)p = n;
  }
  return (void *)(p + 8);
}
static void *genericRealloc(void *p, int n){
  char *p2 = ((char *)p - 8);
  assert(n>0);
  p2 = realloc(p2, n+8);
  if( p2 ){
    *(int *)p2 = n;
  }
  return (void *)((char *)p2 + 8);
}
static void genericFree(void *p){
  assert(p);
  free((void *)((char *)p - 8));
}
static int genericAllocationSize(void *p){
  return *(int *)((char *)p - 8);
}

** This function is called automatically when a thread exists to delete
** the threads SqliteTsd structure. 
**
** Because the SqliteTsd structure is required by higher level routines
** such as sqliteMalloc() we use OsFree() and OsMalloc() directly to
** allocate the thread specific data.
*/
#ifdef SQLITE_UNIX_THREADS
static void deleteTsd(void *pTsd){
  sqlite3Os.xFree(pTsd);
}
#endif

/* 
** The first time this function is called from a specific thread, nByte 
** bytes of data area are allocated and zeroed. A pointer to the new 
** allocation is returned to the caller. 
**
** Each subsequent call to this function from the thread returns the same

      keyInit = 1;
    }
    sqlite3Os.xLeaveMutex();
  }

  pTsd = (SqliteTsd *)pthread_getspecific(key);
  if( !pTsd ){
    pTsd = sqlite3Os.xMalloc(sizeof(SqliteTsd));
    if( pTsd ){
      memset(pTsd, 0, sizeof(SqliteTsd));
      pthread_setspecific(key, pTsd);
    }
  }
  return pTsd;
#else
  static char tsd[sizeof(SqliteTsd)];
  static int isInit = 0;
  assert( nByte==sizeof(SqliteTsd) );
  if( !isInit ){
    memset(tsd, 0, sizeof(SqliteTsd));
    isInit = 1;
  }
  return (void *)tsd;
#endif

  IF_DISKIO( unixSyncDirectory ),
  IF_DISKIO( unixTempFileName ),
  unixRandomSeed,
  unixSleep,
  unixCurrentTime,
  unixEnterMutex,
  unixLeaveMutex,
  unixThreadSpecificData,
  genericMalloc,
  genericRealloc,
  genericFree,
  genericAllocationSize
};



#endif /* OS_UNIX */

  IF_DISKIO( winSyncDirectory ),
  IF_DISKIO( winTempFileName ),
  winRandomSeed,
  winSleep,
  winCurrentTime,
  winEnterMutex,
  winLeaveMutex,
  winThreadSpecificData,
  genericMalloc,
  genericRealloc,
  genericFree,
  genericAllocationSize
};

#endif /* OS_WIN */

**
*************************************************************************
** Utility functions used throughout sqlite.
**
** This file contains functions for allocating memory, comparing
** strings, and stuff like that.
**
** $Id: util.c,v 1.154 2005/12/15 10:50:54 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include "os.h"
#include <stdarg.h>
#include <ctype.h>

/*

** The function sqlite3FreeX performs the same task as sqlite3Free and is
** guaranteed to be a real function.
**
** The above APIs are implemented in terms of the functions provided at the Os
** level (not in this file). The Os level interface is never accessed directly
** by code outside of this file.
**
**     sqlite3Os.xMalloc()
**     sqlite3Os.xRealloc()
**     sqlite3Os.xFree()
**     sqlite3Os.xAllocationSize()
**
** Functions sqlite3MallocRaw() and sqlite3Realloc() may invoke 
** sqlite3_release_memory() if a call to sqlite3Os.xMalloc() or
** sqlite3Os.xRealloc() fails. Function sqlite3Malloc() usually invokes
** sqlite3MallocRaw().
**
** MALLOC TEST WRAPPER ARCHITECTURE
**
** The test wrapper provides extra test facilities to ensure the library 
** does not leak memory and handles the failure of the underlying (Os level)
** allocation system correctly. It is only present if the library is 
** compiled with the SQLITE_MEMDEBUG macro set.
**
**     * Guardposts to detect overwrites.
**     * Ability to cause a specific Malloc() or Realloc() to fail.
**     * Audit outstanding memory allocations (i.e check for leaks).
*/





































/*
** TODO!
*/
#define sqlite3_release_memory(x) 0

#ifdef SQLITE_MEMDEBUG
/*--------------------------------------------------------------------------

*/ 

#define TESTALLOC_OFFSET_GUARD1(p)    (sizeof(void *) * 2)
#define TESTALLOC_OFFSET_DATA(p) ( \
  TESTALLOC_OFFSET_GUARD1(p) + sizeof(u32) * TESTALLOC_NGUARD \
)
#define TESTALLOC_OFFSET_GUARD2(p) ( \
  TESTALLOC_OFFSET_DATA(p) + sqlite3Os.xAllocationSize(p) - TESTALLOC_OVERHEAD \
)
#define TESTALLOC_OFFSET_LINENUMBER(p) ( \
  TESTALLOC_OFFSET_GUARD2(p) + sizeof(u32) * TESTALLOC_NGUARD \
)
#define TESTALLOC_OFFSET_FILENAME(p) ( \
  TESTALLOC_OFFSET_LINENUMBER(p) + sizeof(u32) \
)

      return 1;
    }
  }
  return 0;
}

/*
** The argument is a pointer returned by sqlite3Os.xMalloc() or xRealloc().
** assert() that the first and last (TESTALLOC_NGUARD*4) bytes are set to the
** values set by the applyGuards() function.
*/
static void checkGuards(u32 *p)
{
  int i;
  char *zAlloc = (char *)p;

    u32 guard = 0;
    memcpy(&guard, &z[i*sizeof(u32)], sizeof(u32));
    assert(guard==0xdead3344);
  }
}

/*
** The argument is a pointer returned by sqlite3Os.xMalloc() or Realloc(). The
** first and last (TESTALLOC_NGUARD*4) bytes are set to known values for use as 
** guard-posts.
*/
static void applyGuards(u32 *p)
{
  int i;
  char *z;

  Tcl_IncrRefCount(pRes);

  for(p=pTsd->pFirst; p; p=((void **)p)[1]){
    Tcl_Obj *pEntry = Tcl_NewObj();
    Tcl_Obj *pStack = Tcl_NewObj();
    char *z;
    u32 iLine;
    int nBytes = sqlite3Os.xAllocationSize(p) - TESTALLOC_OVERHEAD;
    char *zAlloc = (char *)p;
    int i;

    Tcl_ListObjAppendElement(0, pEntry, Tcl_NewIntObj(nBytes));

    z = &zAlloc[TESTALLOC_OFFSET_FILENAME(p)];
    Tcl_ListObjAppendElement(0, pEntry, Tcl_NewStringObj(z, -1));

  Tcl_SetObjResult(interp, pRes);
  Tcl_DecrRefCount(pRes);
  return TCL_OK;
}
#endif

/*
** This is the test layer's wrapper around sqlite3Os.xMalloc().
*/
static void * OSMALLOC(int n){
  if( !failMalloc() ){
    u32 *p;
    p = (u32 *)sqlite3Os.xMalloc(n + TESTALLOC_OVERHEAD);
    assert(p);
    sqlite3_nMalloc++;
    applyGuards(p);
    linkAlloc(p);
    return (void *)(&p[TESTALLOC_NGUARD + 2*sizeof(void *)/sizeof(u32)]);
  }
  return 0;
}

/*
** This is the test layer's wrapper around sqlite3Os.xFree(). The argument is a
** pointer to the space allocated for the application to use.
*/
void OSFREE(void *pFree){
  u32 *p = (u32 *)getOsPointer(pFree);   /* p points to Os level allocation */
  checkGuards(p);
  unlinkAlloc(p);
  sqlite3Os.xFree(p);
  sqlite3_nFree++;
}

/*
** This is the test layer's wrapper around sqlite3Os.xRealloc().
*/
void * OSREALLOC(void *pRealloc, int n){
  if( !failMalloc() ){
    u32 *p = (u32 *)getOsPointer(pRealloc);
    checkGuards(p);
    p = sqlite3Os.xRealloc(p, n + TESTALLOC_OVERHEAD);
    applyGuards(p);
    relinkAlloc(p);
    return (void *)(&p[TESTALLOC_NGUARD + 2*sizeof(void *)/sizeof(u32)]);
  }
  return 0;
}

void OSMALLOC_FAILED(){
  sqlite3Tsd()->isFail = 0;
}

int OSSIZEOF(void *p){
  if( p ){
    return sqlite3Os.xAllocationSize(p) - TESTALLOC_OVERHEAD;
  }
  return 0;
}

#else
#define OSMALLOC(x) sqlite3Os.xMalloc(x)
#define OSREALLOC(x,y) sqlite3Os.xRealloc(x,y)
#define OSFREE(x) sqlite3Os.xFree(x)
#define OSSIZEOF(x) sqlite3Os.xAllocationSize(x)
#define OSMALLOC_FAILED()
#endif
/*
** End code for memory allocation system test layer.
**--------------------------------------------------------------------------*/

/*
** The handleSoftLimit() function is called before each call to 
** sqlite3Os.xMalloc() or xRealloc(). The parameter 'n' is the number of
** extra bytes about to be allocated (for Realloc() this means the size of the
** new allocation less the size of the old allocation). If the extra allocation
** means that the total memory allocated to SQLite in this thread would exceed
** the limit set by sqlite3_soft_heap_limit(), then sqlite3_release_memory() is
** called to try to avoid this. No indication of whether or not this is
** successful is returned to the caller.
**

}
#else
#define handleSoftLimit()
#endif

/*
** Allocate and return N bytes of uninitialised memory by calling
** sqlite3Os.xMalloc(). If the Malloc() call fails, attempt to free memory 
** by calling sqlite3_release_memory().
*/
void *sqlite3MallocRaw(int n){
  SqliteTsd *pTsd = sqlite3Tsd();
  void *p = 0;
  if( n>0 && !pTsd->mallocFailed ){
    handleSoftLimit(n);
    while( !(p = OSMALLOC(n)) && sqlite3_release_memory(n) );
    if( !p ){
      sqlite3Tsd()->mallocFailed = 1;
      OSMALLOC_FAILED();
    }
  }
  return p;
}

/*
** Resize the allocation at p to n bytes by calling sqlite3Os.xRealloc(). The
** pointer to the new allocation is returned.  If the Realloc() call fails,
** attempt to free memory by calling sqlite3_release_memory().
*/
void *sqlite3Realloc(void *p, int n){
  SqliteTsd *pTsd = sqlite3Tsd();
  if( pTsd->mallocFailed ){
    return 0;