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Comment:Micro-optimization in lookslike* functions, proving that LOOK_CR can be expressed as (LOOK_LONE_CR | LOOK_CRLF) and LOOK_LF as (LOOK_LONE_LF | LOOK_CRLF). This saves 6 assembler-instructions in the loops. Ready to be reviewed.
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Timelines: family | ancestors | descendants | both | pending-review
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SHA1: 13c796a496ba77ebcddc776e636cedc54954c9cf
User & Date: jan.nijtmans 2015-11-12 11:37:02
Context
2015-12-21
08:49
merge trunk check-in: 255327f0 user: jan.nijtmans tags: pending-review
2015-11-12
11:37
Micro-optimization in lookslike* functions, proving that LOOK_CR can be expressed as (LOOK_LONE_CR | LOOK_CRLF) and LOOK_LF as (LOOK_LONE_LF | LOOK_CRLF). This saves 6 assembler-instructions in the loops. Ready to be reviewed. check-in: 13c796a4 user: jan.nijtmans tags: pending-review
11:32
re-shuffle LOOK_XXX flags such that LOOK_CR and LOOK_LF are last check-in: b29b7fd3 user: jan.nijtmans tags: pending-review
Changes
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Changes to src/lookslike.c.

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#define LOOK_CRLF    ((int)0x00000008) /* One or more CR/LF pairs were found. */
#define LOOK_LONG    ((int)0x00000010) /* An over length line was found. */
#define LOOK_ODD     ((int)0x00000020) /* An odd number of bytes was found. */
#define LOOK_SHORT   ((int)0x00000040) /* Unable to perform full check. */
#define LOOK_INVALID ((int)0x00000080) /* Invalid sequence was found. */
#define LOOK_BINARY  (LOOK_NUL | LOOK_LONG | LOOK_SHORT) /* May be binary. */
#define LOOK_EOL     (LOOK_LONE_CR | LOOK_LONE_LF | LOOK_CRLF) /* Line seps. */
#define LOOK_CR      ((int)0x00000100) /* One or more CR chars. */
#define LOOK_LF      ((int)0x00000200) /* One or more LF chars. */
#endif /* INTERFACE */


/*
** This function attempts to scan each logical line within the blob to
** determine the type of content it appears to contain.  The return value
** is a combination of one or more of the LOOK_XXX flags (see above):
................................................................................
  int j, c, flags = LOOK_NONE;  /* Assume UTF-8 text, prove otherwise */

  if( n==0 ) return flags;  /* Empty file -> text */
  c = *z;
  if( c==0 ){
    flags |= LOOK_NUL;  /* NUL character in a file -> binary */
  }else if( c=='\r' ){
    flags |= LOOK_CR;
    if( n<=1 || z[1]!='\n' ){
      flags |= LOOK_LONE_CR;  /* More chars, next char is not LF */
    }
  }
  j = (c!='\n');
  if( !j ) flags |= (LOOK_LF | LOOK_LONE_LF);  /* Found LF as first char */
  while( !(flags&stopFlags) && --n>0 ){
    int c2 = c;
    c = *++z; ++j;
    if( c==0 ){
      flags |= LOOK_NUL;  /* NUL character in a file -> binary */
    }else if( c=='\n' ){
      flags |= LOOK_LF;
      if( c2=='\r' ){
        flags |= (LOOK_CR | LOOK_CRLF);  /* Found LF preceded by CR */
      }else{
        flags |= LOOK_LONE_LF;
      }
      if( j>LENGTH_MASK ){
        flags |= LOOK_LONG;  /* Very long line -> binary */
      }
      j = 0;
    }else if( c=='\r' ){
      flags |= LOOK_CR;
      if( n<=1 || z[1]!='\n' ){
        flags |= LOOK_LONE_CR;  /* More chars, next char is not LF */
      }
    }
  }
  if( n ){
    flags |= LOOK_SHORT;  /* The whole blob was not examined */
................................................................................
  c = *z;
  if( bReverse ){
    c = UTF16_SWAP(c);
  }
  if( c==0 ){
    flags |= LOOK_NUL;  /* NUL character in a file -> binary */
  }else if( c=='\r' ){
    flags |= LOOK_CR;
    if( n<(2*sizeof(WCHAR_T)) || UTF16_SWAP_IF(bReverse, z[1])!='\n' ){
      flags |= LOOK_LONE_CR;  /* More chars, next char is not LF */
    }
  }
  j = (c!='\n');
  if( !j ) flags |= (LOOK_LF | LOOK_LONE_LF);  /* Found LF as first char */
  while( !(flags&stopFlags) && ((n-=sizeof(WCHAR_T))>=sizeof(WCHAR_T)) ){
    int c2 = c;
    c = *++z;
    if( bReverse ){
      c = UTF16_SWAP(c);
    }
    ++j;
    if( c==0 ){
      flags |= LOOK_NUL;  /* NUL character in a file -> binary */
    }else if( c=='\n' ){
      flags |= LOOK_LF;
      if( c2=='\r' ){
        flags |= (LOOK_CR | LOOK_CRLF);  /* Found LF preceded by CR */
      }else{
        flags |= LOOK_LONE_LF;
      }
      if( j>UTF16_LENGTH_MASK ){
        flags |= LOOK_LONG;  /* Very long line -> binary */
      }
      j = 0;
    }else if( c=='\r' ){
      flags |= LOOK_CR;
      if( n<(2*sizeof(WCHAR_T)) || UTF16_SWAP_IF(bReverse, z[1])!='\n' ){
        flags |= LOOK_LONE_CR;  /* More chars, next char is not LF */
      }
    }
  }
  if( n ){
    flags |= LOOK_SHORT;  /* The whole blob was not examined */







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#define LOOK_CRLF    ((int)0x00000008) /* One or more CR/LF pairs were found. */
#define LOOK_LONG    ((int)0x00000010) /* An over length line was found. */
#define LOOK_ODD     ((int)0x00000020) /* An odd number of bytes was found. */
#define LOOK_SHORT   ((int)0x00000040) /* Unable to perform full check. */
#define LOOK_INVALID ((int)0x00000080) /* Invalid sequence was found. */
#define LOOK_BINARY  (LOOK_NUL | LOOK_LONG | LOOK_SHORT) /* May be binary. */
#define LOOK_EOL     (LOOK_LONE_CR | LOOK_LONE_LF | LOOK_CRLF) /* Line seps. */
#define LOOK_CR      (LOOK_LONE_CR | LOOK_CRLF) /* One or more CR chars. */
#define LOOK_LF      (LOOK_LONE_LF | LOOK_CRLF) /* One or more LF chars. */
#endif /* INTERFACE */


/*
** This function attempts to scan each logical line within the blob to
** determine the type of content it appears to contain.  The return value
** is a combination of one or more of the LOOK_XXX flags (see above):
................................................................................
  int j, c, flags = LOOK_NONE;  /* Assume UTF-8 text, prove otherwise */

  if( n==0 ) return flags;  /* Empty file -> text */
  c = *z;
  if( c==0 ){
    flags |= LOOK_NUL;  /* NUL character in a file -> binary */
  }else if( c=='\r' ){

    if( n<=1 || z[1]!='\n' ){
      flags |= LOOK_LONE_CR;  /* More chars, next char is not LF */
    }
  }
  j = (c!='\n');
  if( !j ) flags |= (LOOK_LONE_LF);  /* Found LF as first char */
  while( !(flags&stopFlags) && --n>0 ){
    int c2 = c;
    c = *++z; ++j;
    if( c==0 ){
      flags |= LOOK_NUL;  /* NUL character in a file -> binary */
    }else if( c=='\n' ){

      if( c2=='\r' ){
        flags |= (LOOK_CRLF);  /* Found LF preceded by CR */
      }else{
        flags |= LOOK_LONE_LF;
      }
      if( j>LENGTH_MASK ){
        flags |= LOOK_LONG;  /* Very long line -> binary */
      }
      j = 0;
    }else if( c=='\r' ){

      if( n<=1 || z[1]!='\n' ){
        flags |= LOOK_LONE_CR;  /* More chars, next char is not LF */
      }
    }
  }
  if( n ){
    flags |= LOOK_SHORT;  /* The whole blob was not examined */
................................................................................
  c = *z;
  if( bReverse ){
    c = UTF16_SWAP(c);
  }
  if( c==0 ){
    flags |= LOOK_NUL;  /* NUL character in a file -> binary */
  }else if( c=='\r' ){

    if( n<(2*sizeof(WCHAR_T)) || UTF16_SWAP_IF(bReverse, z[1])!='\n' ){
      flags |= LOOK_LONE_CR;  /* More chars, next char is not LF */
    }
  }
  j = (c!='\n');
  if( !j ) flags |= (LOOK_LONE_LF);  /* Found LF as first char */
  while( !(flags&stopFlags) && ((n-=sizeof(WCHAR_T))>=sizeof(WCHAR_T)) ){
    int c2 = c;
    c = *++z;
    if( bReverse ){
      c = UTF16_SWAP(c);
    }
    ++j;
    if( c==0 ){
      flags |= LOOK_NUL;  /* NUL character in a file -> binary */
    }else if( c=='\n' ){

      if( c2=='\r' ){
        flags |= (LOOK_CRLF);  /* Found LF preceded by CR */
      }else{
        flags |= LOOK_LONE_LF;
      }
      if( j>UTF16_LENGTH_MASK ){
        flags |= LOOK_LONG;  /* Very long line -> binary */
      }
      j = 0;
    }else if( c=='\r' ){

      if( n<(2*sizeof(WCHAR_T)) || UTF16_SWAP_IF(bReverse, z[1])!='\n' ){
        flags |= LOOK_LONE_CR;  /* More chars, next char is not LF */
      }
    }
  }
  if( n ){
    flags |= LOOK_SHORT;  /* The whole blob was not examined */