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SQLite training in Houston TX on 2019-11-05 (details)
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Overview
Comment:Faster and smaller implementation of sqlite3AtoF() based on a suggestion from Cezary H. Noweta.
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SHA3-256: fd2e0e7a770c2ce9355068aad1024c3d2861c104fd3be304a91c55ca742155fa
User & Date: drh 2017-12-26 14:46:20
Context
2017-12-27
18:19
Enhance the Lemon parser generator so that it creates a faster parser at the cost of slightly larger parser tables. Add the ability to measure coverage of the generated state machine when compiling with the -DYYCONVERGE option. In SQLite, add the SQLITE_TESTCTRL_PARSER_COVERAGE test-control to query the new parser coverage feature. check-in: 1b22b42e user: drh tags: trunk
2017-12-26
18:14
Merge bug fixes from trunk. check-in: d76e1206 user: drh tags: lemon-improvements
14:46
Faster and smaller implementation of sqlite3AtoF() based on a suggestion from Cezary H. Noweta. check-in: fd2e0e7a user: drh tags: trunk
14:32
Fix crashes that could occur if SQL NULL values were passed to the built-in FTS5 snippet function. Edit: breaks amalgamation builds. check-in: 6a790b67 user: dan tags: trunk
Changes
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Changes to src/util.c.

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    return 1;
  }
  a = (unsigned char *)zLeft;
  b = (unsigned char *)zRight;
  while( N-- > 0 && *a!=0 && UpperToLower[*a]==UpperToLower[*b]){ a++; b++; }
  return N<0 ? 0 : UpperToLower[*a] - UpperToLower[*b];
}



















/*
** The string z[] is an text representation of a real number.
** Convert this string to a double and write it into *pResult.
**
** The string z[] is length bytes in length (bytes, not characters) and
** uses the encoding enc.  The string is not necessarily zero-terminated.
................................................................................

    /* adjust the sign of significand */
    s = sign<0 ? -s : s;

    if( e==0 ){                                         /*OPTIMIZATION-IF-TRUE*/
      result = (double)s;
    }else{
      LONGDOUBLE_TYPE scale = 1.0;
      /* attempt to handle extremely small/large numbers better */
      if( e>307 ){                                      /*OPTIMIZATION-IF-TRUE*/
        if( e<342 ){                                    /*OPTIMIZATION-IF-TRUE*/
          while( e%308 ) { scale *= 1.0e+1; e -= 1; }
          if( esign<0 ){
            result = s / scale;
            result /= 1.0e+308;
          }else{
            result = s * scale;
            result *= 1.0e+308;
          }
................................................................................
            result = INFINITY*s;
#else
            result = 1e308*1e308*s;  /* Infinity */
#endif
          }
        }
      }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;
        }
      }
    }







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    return 1;
  }
  a = (unsigned char *)zLeft;
  b = (unsigned char *)zRight;
  while( N-- > 0 && *a!=0 && UpperToLower[*a]==UpperToLower[*b]){ a++; b++; }
  return N<0 ? 0 : UpperToLower[*a] - UpperToLower[*b];
}

/*
** Compute 10 to the E-th power.  Examples:  E==1 results in 10.
** E==2 results in 100.  E==50 results in 1.0e50.
**
** This routine only works for values of E between 1 and 341.
*/
static LONGDOUBLE_TYPE sqlite3Pow10(int E){
  LONGDOUBLE_TYPE x = 10.0;
  LONGDOUBLE_TYPE r = 1.0;
  while(1){
    if( E & 1 ) r *= x;
    E >>= 1;
    if( E==0 ) break;
    x *= x;
  }
  return r; 
}

/*
** The string z[] is an text representation of a real number.
** Convert this string to a double and write it into *pResult.
**
** The string z[] is length bytes in length (bytes, not characters) and
** uses the encoding enc.  The string is not necessarily zero-terminated.
................................................................................

    /* adjust the sign of significand */
    s = sign<0 ? -s : s;

    if( e==0 ){                                         /*OPTIMIZATION-IF-TRUE*/
      result = (double)s;
    }else{

      /* attempt to handle extremely small/large numbers better */
      if( e>307 ){                                      /*OPTIMIZATION-IF-TRUE*/
        if( e<342 ){                                    /*OPTIMIZATION-IF-TRUE*/
          LONGDOUBLE_TYPE scale = sqlite3Pow10(e-308);
          if( esign<0 ){
            result = s / scale;
            result /= 1.0e+308;
          }else{
            result = s * scale;
            result *= 1.0e+308;
          }
................................................................................
            result = INFINITY*s;
#else
            result = 1e308*1e308*s;  /* Infinity */
#endif
          }
        }
      }else{
        LONGDOUBLE_TYPE scale = sqlite3Pow10(e);



        if( esign<0 ){
          result = s / scale;
        }else{
          result = s * scale;
        }
      }
    }