[ragel-users] Re: Fixing an edge case

[Adrian Thurston]

Sorry, this was sloppy ... the question mark in the diff machine can be removed.

-Adrian

Adrian Thurston wrote:
> Hi Matt, try the attached file. The important part is in diff machine. The
> first alternative handles the edge case of an empty diff. The second part
> handles the regular case.
> 
> -Adrian
> 
> > 
> jinclude <stdio.h>
> 
> %%{
>     machine diff;
>     action count_line {}
>     action mark {}
>     action add_line {}
>     action push {}
>     action push_zero {}
>     action pop_hunk_spec {}
>     action copy_to_filespec {}
>     action enter_hunk { printf("  enter_hunk\n"); }
>     action exit_hunk {  printf("  exit_hunk\n"); }
>     action enter_diff { printf("enter_diff\n"); }
>     action exit_diff { printf("exit_diff\n"); }
>     action empty_diff { printf("  this diff is empty\n"); }
>     action binary_diff {}
>     action error {}
> 
>     nbsp = space - '\n' %count_line;
>     lineChar = extend - '\n';
>     
>     diffLine =         ( '\\' lineChar* '\n' %count_line ) |
>         ( ' ' | '-' | '+' ) >mark         lineChar* '\n' @add_line
> %count_line;
>     
>     separator = '='+ '\n' %count_line;
>     
>     oldFile = '---' lineChar+ '\n' %count_line;
>     newFile = '+++' lineChar+ '\n' %count_line;
>     
>     range = ( '-' | '+' ) ( digit+ >mark %push ) ( ' ' %push_zero
>             @{ fhold; }  | ',' ( digit+ >mark %push ) );
>     
>     hunkHeader = '@@' nbsp* range nbsp+ range nbsp* '@@' '\n'
>         @pop_hunk_spec %count_line;
>     
>     hunkBody = diffLine+;
>     
>     hunk = hunkHeader >enter_hunk hunkBody %exit_hunk %/exit_hunk;
>     
>     fileName = ( lineChar+ ) >mark %copy_to_filespec;
>     
>     fileSpec = "Index:" nbsp+ fileName '\n'+ @count_line;
>     
>     diffHeader = fileSpec separator;
>     
>     diffBody = hunk*;
>     
>     binaryDiff = 'C' lineChar+ '\n' %count_line lineChar+ '\n'
>         %binary_diff %count_line;
>     
>     textDiff = oldFile newFile diffBody;
>     
>     diff = (
>         diffHeader %empty_diff %/empty_diff |
>         diffHeader ( binaryDiff | textDiff ) ?
>     )
>     >enter_diff    %exit_diff %/exit_diff;
>     
>     main := diff* $!error;
> }%%
> 
> %% write data;
> 
> int main()
> {
>     static char buf[2000000];
>     int len = fread( buf, 1, sizeof(buf), stdin );
>     printf( "%i\n", len );
> 
>     int cs;
>     char *p = buf, *pe = buf+len;
>     %%{
>         write init;
>         write exec;
>     }%%
> 
>     if ( cs < diff_first_final )
>         printf(" ERROR \n" );
>     else {
>         %% write eof;
>     }
>     return 0;
> }
>