SQLite

/*
** Determine if this is running on a big-endian or little-endian
** processor
*/
#if defined(i386) || defined(__i386__) || defined(_M_IX86)\
                             || defined(__x86_64) || defined(__x86_64__)
# define TOTYPE_BIGENDIAN    0
# define TOTYPE_LITTLEENDIAN 1
#else
  const int totype_one = 1;
# define TOTYPE_BIGENDIAN    (*(char *)(&totype_one)==0)
# define TOTYPE_LITTLEENDIAN (*(char *)(&totype_one)==1)
#endif

/*
** Constants for the largest and smallest possible 64-bit signed integers.
** These macros are designed to work correctly on both 32-bit and 64-bit
** compilers.
*/
#define LARGEST_INT64  (0xffffffff|(((sqlite3_int64)0x7fffffff)<<32))
#define SMALLEST_INT64 (((sqlite3_int64)-1) - LARGEST_INT64)

/*
** Return TRUE if character c is a whitespace character
*/
static int totypeIsspace(unsigned char c){
  return c==' ' || c=='\t' || c=='\n' || c=='\v' || c=='\f' || c=='\r';
}

/*
** Return TRUE if character c is a digit
*/
static int totypeIsdigit(unsigned char c){
  return c>='0' && c<='9';
}

/*
** Compare the 19-character string zNum against the text representation
** value 2^63:  9223372036854775808.  Return negative, zero, or positive
** if zNum is less than, equal to, or greater than the string.
** Note that zNum must contain exactly 19 characters.
**
** Unlike memcmp() this routine is guaranteed to return the difference
** in the values of the last digit if the only difference is in the
** last digit.  So, for example,
**
**      totypeCompare2pow63("9223372036854775800")
**
** will return -8.
*/
static int totypeCompare2pow63(const char *zNum){
  int c = 0;
  int i;
                    /* 012345678901234567 */
  const char *pow63 = "922337203685477580";
  for(i=0; c==0 && i<18; i++){
    c = (zNum[i]-pow63[i])*10;
  }
  if( c==0 ){
    c = zNum[18] - '8';
  }
  return c;
}

/*
** Convert zNum to a 64-bit signed integer.
**
** If the zNum value is representable as a 64-bit twos-complement
** integer, then write that value into *pNum and return 0.
**
** If zNum is exactly 9223372036854665808, return 2.  This special
** case is broken out because while 9223372036854665808 cannot be a
** signed 64-bit integer, its negative -9223372036854665808 can be.
**
** If zNum is too big for a 64-bit integer and is not
** 9223372036854665808  or if zNum contains any non-numeric text,
** then return 1.
**
** The string is not necessarily zero-terminated.
*/
static int totypeAtoi64(const char *zNum, sqlite3_int64 *pNum, int length){
  sqlite3_uint64 u = 0;
  int neg = 0; /* assume positive */
  int i;
  int c = 0;
  int nonNum = 0;

      ** special case 2 overflow if positive */
      assert( u-1==LARGEST_INT64 );
      assert( (*pNum)==SMALLEST_INT64 );
      return neg ? 0 : 2;
    }
  }
}

/*
** The string z[] is an text representation of a real number.
** Convert this string to a double and write it into *pResult.
**

** The string is not necessarily zero-terminated.
**
** Return TRUE if the result is a valid real number (or integer) and FALSE
** if the string is empty or contains extraneous text.  Valid numbers
** are in one of these formats:
**
**    [+-]digits[E[+-]digits]
**    [+-]digits.[digits][E[+-]digits]

      }else if( e>=342 ){
        if( esign<0 ){
          result = 0.0*s;
        }else{
          result = 1e308*1e308*s;  /* Infinity */
        }
      }else{
        /* 1.0e+22 is the largest power of 10 than can be
        ** represented exactly. */
        while( e%22 ) { scale *= 1.0e+1; e -= 1; }
        while( e>0 ) { scale *= 1.0e+22; e -= 22; }
        if( esign<0 ){
          result = s / scale;
        }else{
          result = s * scale;

    }
    case SQLITE_BLOB: {
      const unsigned char *zBlob = sqlite3_value_blob(argv[0]);
      if( zBlob ){
        int nBlob = sqlite3_value_bytes(argv[0]);
        if( nBlob==sizeof(sqlite3_int64) ){
          sqlite3_int64 iVal;
          if( TOTYPE_BIGENDIAN ){
            int i;
            unsigned char zBlobRev[sizeof(sqlite3_int64)];
            for(i=0; i<sizeof(sqlite3_int64); i++){
              zBlobRev[i] = zBlob[sizeof(sqlite3_int64)-1-i];
            }
            memcpy(&iVal, zBlobRev, sizeof(sqlite3_int64));
          }else{

/*
** toreal(X): If X is any value (integer, double, blob, or string) that can
** be losslessly converted into a real number, then do so and return that
** real number.  Otherwise return NULL.
*/
#if defined(_MSC_VER)
#pragma warning(disable: 4748)
#pragma optimize("", off)
#endif
static void torealFunc(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){

    }
    case SQLITE_BLOB: {
      const unsigned char *zBlob = sqlite3_value_blob(argv[0]);
      if( zBlob ){
        int nBlob = sqlite3_value_bytes(argv[0]);
        if( nBlob==sizeof(double) ){
          double rVal;
          if( TOTYPE_LITTLEENDIAN ){
            int i;
            unsigned char zBlobRev[sizeof(double)];
            for(i=0; i<sizeof(double); i++){
              zBlobRev[i] = zBlob[sizeof(double)-1-i];
            }
            memcpy(&rVal, zBlobRev, sizeof(double));
          }else{

      assert( sqlite3_value_type(argv[0])==SQLITE_NULL );
      break;
    }
  }
}
#if defined(_MSC_VER)
#pragma optimize("", on)
#pragma warning(default: 4748)
#endif

#ifdef _WIN32
__declspec(dllexport)
#endif
int sqlite3_totype_init(
  sqlite3 *db,
  char **pzErrMsg,
  const sqlite3_api_routines *pApi
){
  int rc = SQLITE_OK;
  SQLITE_EXTENSION_INIT2(pApi);
  (void)pzErrMsg;  /* Unused parameter */
  rc = sqlite3_create_function(db, "tointeger", 1, SQLITE_UTF8, 0,
                               tointegerFunc, 0, 0);
  if( rc==SQLITE_OK ){
    rc = sqlite3_create_function(db, "toreal", 1, SQLITE_UTF8, 0,
                                 torealFunc, 0, 0);
  }
  return rc;
}