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Overview
Comment:Performance enhancement in sqlite3AtoF(). About 8% faster.
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SHA3-256: 81721aa54587e20d031d528fb6b74d91671a6e950fa926dc63f4284466e70f0e
User & Date: drh 2019-05-25 18:17:53.260
Context
2019-05-27
00:29
Improved rounding even on systems with an 8-byte "long double" type. (check-in: 15202aee15 user: drh tags: trunk)
2019-05-25
18:17
Performance enhancement in sqlite3AtoF(). About 8% faster. (check-in: 81721aa545 user: drh tags: trunk)
17:41
Use "long double" literals to initialize an array of "long double" objects. (check-in: 2e2ebad3ab user: drh tags: trunk)
Changes
Side-by-Side Diff Ignore Whitespace Patch
Changes to src/util.c.
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  int sign = 1;    /* sign of significand */
  i64 s = 0;       /* significand */
  int d = 0;       /* adjust exponent for shifting decimal point */
  int esign = 1;   /* sign of exponent */
  int e = 0;       /* exponent */
  int eValid = 1;  /* True exponent is either not used or is well-formed */
  double result;
  int nDigits = 0;
  int nDigit = 0;  /* Number of digits processed */
  int nonNum = 0;  /* True if input contains UTF16 with high byte non-zero */

  assert( enc==SQLITE_UTF8 || enc==SQLITE_UTF16LE || enc==SQLITE_UTF16BE );
  *pResult = 0.0;   /* Default return value, in case of an error */

  if( enc==SQLITE_UTF8 ){
    incr = 1;
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    sign = -1;
    z+=incr;
  }else if( *z=='+' ){
    z+=incr;
  }

  /* copy max significant digits to significand */
  while( z<zEnd && sqlite3Isdigit(*z) && s<((LARGEST_INT64-9)/10) ){
  while( z<zEnd && sqlite3Isdigit(*z) ){
    s = s*10 + (*z - '0');
    z+=incr; nDigits++;
    z+=incr; nDigit++;
  }

  /* skip non-significant significand digits
  ** (increase exponent by d to shift decimal left) */
  while( z<zEnd && sqlite3Isdigit(*z) ){ z+=incr; nDigits++; d++; }
    if( s>=((LARGEST_INT64-9)/10) ){
      /* skip non-significant significand digits
      ** (increase exponent by d to shift decimal left) */
      while( z<zEnd && sqlite3Isdigit(*z) ){ z+=incr; d++; }
    }
  }
  if( z>=zEnd ) goto do_atof_calc;

  /* if decimal point is present */
  if( *z=='.' ){
    z+=incr;
    /* copy digits from after decimal to significand
    ** (decrease exponent by d to shift decimal right) */
    while( z<zEnd && sqlite3Isdigit(*z) ){
      if( s<((LARGEST_INT64-9)/10) ){
        s = s*10 + (*z - '0');
        d--;
        nDigit++;
      }
      z+=incr; nDigits++;
      z+=incr;
    }
  }
  if( z>=zEnd ) goto do_atof_calc;

  /* if exponent is present */
  if( *z=='e' || *z=='E' ){
    z+=incr;
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    }
  }

  /* store the result */
  *pResult = result;

  /* return true if number and no extra non-whitespace chracters after */
  return z==zEnd && nDigits>0 && eValid && nonNum==0;
  return z==zEnd && nDigit>0 && eValid && nonNum==0;
#else
  return !sqlite3Atoi64(z, pResult, length, enc);
#endif /* SQLITE_OMIT_FLOATING_POINT */
}

/*
** Compare the 19-character string zNum against the text representation
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