SQLite

  assert( db==0 || db->pnBytesFreed==0 );
#ifndef SQLITE_OMIT_LOOKASIDE
  if( db ){
    LookasideSlot *pBuf;
    if( db->mallocFailed ){
      return 0;
    }
    if( db->lookaside.bEnabled ){
      if( n>db->lookaside.sz ){
        db->lookaside.anStat[1]++;
      }else if( (pBuf = db->lookaside.pFree)==0 ){
        db->lookaside.anStat[2]++;
      }else{
        db->lookaside.pFree = pBuf->pNext;
        db->lookaside.nOut++;
        db->lookaside.anStat[0]++;
        if( db->lookaside.nOut>db->lookaside.mxOut ){
          db->lookaside.mxOut = db->lookaside.nOut;
        }
        return (void*)pBuf;
      }
    }
  }
#else
  if( db && db->mallocFailed ){
    return 0;
  }
#endif

** The [sqlite3_db_status()] interface will return a non-zero error code
** if a discontinued or unsupported verb is invoked.
**
** <dl>
** ^(<dt>SQLITE_DBSTATUS_LOOKASIDE_USED</dt>
** <dd>This parameter returns the number of lookaside memory slots currently
** checked out.</dd>)^
**
** ^(<dt>SQLITE_DBSTATUS_LOOKASIDE_HIT</dt>
** <dd>This parameter returns the number malloc attempts that were 
** satisfied using lookaside memory. Only the high-water value is meaningful;
** the current value is always zero.
** checked out.</dd>)^
**
** ^(<dt>SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE</dt>
** <dd>This parameter returns the number malloc attempts that might have
** been satisfied using lookaside memory but failed due to the amount of
** memory requested being larger than the lookaside slot size.
** Only the high-water value is meaningful;
** the current value is always zero.
** checked out.</dd>)^
**
** ^(<dt>SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL</dt>
** <dd>This parameter returns the number malloc attempts that might have
** been satisfied using lookaside memory but failed due to all lookaside
** memory already being in use.
** Only the high-water value is meaningful;
** the current value is always zero.
** checked out.</dd>)^
**
** ^(<dt>SQLITE_DBSTATUS_CACHE_USED</dt>
** <dd>This parameter returns the approximate number of of bytes of heap
** memory used by all pager caches associated with the database connection.)^
** ^The highwater mark associated with SQLITE_DBSTATUS_CACHE_USED is always 0.
**
** ^(<dt>SQLITE_DBSTATUS_SCHEMA_USED</dt>

** <dd>This parameter returns the approximate number of of bytes of heap
** and lookaside memory used by all prepared statements associated with
** the database connection.)^
** ^The highwater mark associated with SQLITE_DBSTATUS_STMT_USED is always 0.
** </dd>
** </dl>
*/
#define SQLITE_DBSTATUS_LOOKASIDE_USED       0
#define SQLITE_DBSTATUS_CACHE_USED           1
#define SQLITE_DBSTATUS_SCHEMA_USED          2
#define SQLITE_DBSTATUS_STMT_USED            3
#define SQLITE_DBSTATUS_LOOKASIDE_HIT        4
#define SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE  5
#define SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL  6
#define SQLITE_DBSTATUS_MAX                  6   /* Largest defined DBSTATUS */


/*
** CAPI3REF: Prepared Statement Status
**
** ^(Each prepared statement maintains various
** [SQLITE_STMTSTATUS_SORT | counters] that measure the number

*/
struct Lookaside {
  u16 sz;                 /* Size of each buffer in bytes */
  u8 bEnabled;            /* False to disable new lookaside allocations */
  u8 bMalloced;           /* True if pStart obtained from sqlite3_malloc() */
  int nOut;               /* Number of buffers currently checked out */
  int mxOut;              /* Highwater mark for nOut */
  int anStat[3];          /* 0: hits.  1: size misses.  2: full misses */
  LookasideSlot *pFree;   /* List of available buffers */
  void *pStart;           /* First byte of available memory space */
  void *pEnd;             /* First byte past end of available space */
};
struct LookasideSlot {
  LookasideSlot *pNext;    /* Next buffer in the list of free buffers */
};

      *pCurrent = db->lookaside.nOut;
      *pHighwater = db->lookaside.mxOut;
      if( resetFlag ){
        db->lookaside.mxOut = db->lookaside.nOut;
      }
      break;
    }

    case SQLITE_DBSTATUS_LOOKASIDE_HIT:
    case SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE:
    case SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL: {
      testcase( op==SQLITE_DBSTATUS_LOOKASIDE_HIT );
      testcase( op==SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE );
      testcase( op==SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL );
      assert( (op-SQLITE_DBSTATUS_LOOKASIDE_HIT)>=0 );
      assert( (op-SQLITE_DBSTATUS_LOOKASIDE_HIT)<3 );
      *pCurrent = 0;
      *pHighwater = db->lookaside.anStat[op - SQLITE_DBSTATUS_LOOKASIDE_HIT];
      if( resetFlag ){
        db->lookaside.anStat[op - SQLITE_DBSTATUS_LOOKASIDE_HIT] = 0;
      }
      break;
    }

    /* 
    ** Return an approximation for the amount of memory currently used
    ** by all pagers associated with the given database connection.  The
    ** highwater mark is meaningless and is returned as zero.
    */
    case SQLITE_DBSTATUS_CACHE_USED: {