applydiff

#!/usr/bin/perl
#
#  Apply a diff file. Patch used to do this, but it doesn`t seem
#  to work any more.
#
#  Syntax:
#  applydiff <filename> <patchfile> [options]
#
#  where possible options are
#
#  -b or --backup: Make a backup of the original file
#  -R or --reverse: Reverse the changes (useful for testing)
#
#  Options can occur anywhere on the line, but <filename> must
#  come before <patchfile>.
#
#  E. Anderson
#  April 27, 2018
#
   $backup = 0;
   $reverse = 0;
   $olddir = "<";
   @filelist = ();
   while( @ARGV ) {
      $_ = shift;
      chomp;
      ARGVCASE: {
         if( /^-b/ || /^--backup/ ) {
            $backup = 1; last ARGVCASE;
         }
         if( /^-R/ || /^--reverse/ ) {
            $reverse = 1; $olddir = ">"; last ARGVCASE;
         }
         @filelist = (@filelist, $_);
      }
   }

   if( ! defined( $filelist[0] ) ) {
      die "Syntax: applydiff [-b|--backup] [-R|--reverse] <filename> <patchfile>\n";
   } else {
      $fname = $filelist[0];
   }
   if( ! defined( $filelist[1] ) ) {
      die "Syntax: applydiff [-b|--backup] [-R|--reverse] <filename> <patchfile>\n";
   } else {
      $pfile = $filelist[1];
   }
   $tfile = `mktemp -p .`;
   chomp( $tfile );
   open( FN, $fname ) || die "Could not open file $fname\n";
   open( PF, $pfile ) || die "Could not open file $pfile\n";
   open( TF, ">$tfile" );
   $ifile = 1;
   while( $pline=<PF> ) {
      chomp( $pline );
#
#     Diff output should be in the form
#       <old range><op><new range>
#     where the range may be a single number like 114 or a range
#     like 126,140. Anything else is an error. The operations are
#       a -- append new lines
#       c -- replace old lines with new lines
#       d -- delete old lines
#
      $ll = length($pline);
      $first = 1;
#
#     Find the operator (a, c, or d)
#
      for( $ic=0; $ic<$ll; $ic++ ) {
         $op = substr( $pline, $ic, 1 );
         if( $op eq "a" || $op eq "c" || $op eq "d" ) { last; }
      }
      if( $ic >= $ll ) {
         close( FN ); close( PF ); close( TF );
         die "Unrecognized diff syntax: $pline\n";
      }
#
#     Get the indices ic1:ic2 and jc1:jc2 of the old and new ranges
#
      $ofr = substr( $pline, 0, $ic );
      $nfr = substr( $pline, $ic+1, length( $pline )-($ic+1) );
      $icom = index( $ofr, "," );
      if( $icom < 0 ) {
         $ic1 = $ofr;
         $ic2 = $ofr;
      } else {
         $ic1 = int( substr( $ofr, 0, $icom ) );
         $ic2 = int( substr( $ofr, $icom+1, length( $ofr )-($icom+1) ) );
      }
      $jcom = index( $nfr, "," );
      if( $jcom < 0 ) {
         $jc1 = $nfr;
         $jc2 = $nfr;
      } else {
         $jc1 = int( substr( $nfr, 0, $jcom ) );
         $jc2 = int( substr( $nfr, $jcom+1, length( $nfr )-($jcom+1) ) );
      }
#
#     Swap ic and jc indices if reversing.
#
      if( $reverse ) {
         $i = $ic1; $j = $jc1;
         $ic1 = $j; $jc1 = $i;
         $i = $ic2; $j = $jc2;
         $ic2 = $j; $jc2 = $i;
         if( $op eq "a" ) {
            $op = "d";
         } elsif( $op eq "d" ) {
            $op = "a";
         }
      }
#
#     Read and print lines of fname up to or including line ic1
#
      if( $op eq "a" ) {
         $i2 = $ic1 + 1;
      } else {
         $i2 = $ic1;
      }
      for( $i=$ifile; $i<$i2; $i++ ) {
         $fline = <FN>;
         $ifile++;
         printf TF "%s", $fline;
      }
#
#     If reversing, read the patch file and save its lines to a buffer.
#
      if( $reverse && ( $op eq "c" || $op eq "a" ) ) {
         for( $j = $jc1; $j <= $jc2; $j++ ) {
            $pline = <PF>;
            chomp($pline);
            if( substr( $pline, 0, 1 ) ne "<" ) {
               close( FN ); close( PF ); close( TF );
               die "Expected leading '< ' in diff output\n",
                   "Unrecognized diff spec: $pline\n";
            }
            $buffer[$j-$jc1] = substr( $pline, 2, length($pline)-2 );
         }
      }
#
#     Read and skip lines of fname if they match the diff output.
#     Punt if they do not match.
#
      if( $op eq "c" || $op eq "d" ) {
         for( $i=$ic1; $i<=$ic2; $i++ ) {
            $fline = <FN>;
            chomp( $fline );
            $pline = <PF>;
            if( $first && substr( $pline, 0, 3 ) eq "---" ) {
               $pline = <PF>; $first = 0;
            }
            chomp( $pline );
            $ifile++;
            if( substr( $pline, 0, 1 ) ne $olddir ) {
               close( FN ); close( PF ); close( TF );
               die "Expected leading '$olddir' in diff output\n",
                   "Unrecognized diff spec: $pline\n";
            }
            if( strcmpitb( $fline, substr( $pline, 2, length($pline)-2 ) ) == 0 ) {
               close( FN ); close( PF ); close( TF );
               printf "Diff syntax does not match line %d of file\n", $i;
               printf "File contains: %s\n", $fline;
               printf "Diff contains: %s\n", substr( $pline, 2, length($pline)-2 );
               die;
            }
         }
      }
      if( $op eq "c" || $op eq "a" ) {
         if( $reverse ) {
#
#           If reversing, print the substitute lines from the buffer.
#
            for( $j=$jc1; $j<=$jc2; $j++ ) {
               printf TF "%s\n", $buffer[$j-$jc1];
            }
         } else {
#
#           Otherwise read and print the substitute lines from the diff output.
#
            for( $j=$jc1; $j<=$jc2; $j++ ) {
               $pline = <PF>;
               if( $first && substr( $pline, 0, 3 ) eq "---" ) {
                  $pline = <PF>; $first = 0;
               }
               chomp($pline);
               if( substr( $pline, 0, 1 ) ne ">" ) {
                  close( FN ); close( PF ); close( TF );
                  die "Expected leading '>' in diff output\n",
                      "Unrecognized diff spec: $pline\n";
               }
               printf TF "%s\n", substr( $pline, 2, length($pline)-2 );
            }
         }
      }
   }
   close( PF );
#
#  If we have reached the end of the diff file, read and print the remaining
#  lines of fname.
#
   while( $fline=<FN> ) {
      printf TF "%s", $fline;
   }
   close( $FN );
   close( $TF );
#
#  Overwrite the original file, optionally making a backup
#
   `/bin/chmod --reference=$fname $tfile`;
   if( $backup ) {
      `/bin/mv --backup $tfile $fname`; 
   } else {
      `/bin/mv $tfile $fname`; 
   }
sub strcmpitb{
#
#  See if string1 is the same as string2, ignoring trailing blanks.
#
   my($string1) = $_[0];
   my($string2) = $_[1];
   my($ls1) = length($string1);
   my($ls2) = length($string2);
   my($i,$i1,$i2,$first,$same);
   if( $ls1 < $ls2 ) {
      $i1 = $ls1;
      $i2 = $ls2;
      $first = 0;
   } else {
      $i1 = $ls2;
      $i2 = $ls1;
      $first = 1;
   }
   $same = 1;
   for( $i=0; $i<$i1; $i++ ) {
      $c1 = substr( $string1, $i, 1 );
      $c2 = substr( $string1, $i, 1 );
      if( $c1 ne $c2 ) {
         $same = 0; last;
      }
   }
   if( $same ) {
      while( $i<$i2 ) {
         if( $first ) {
            $c1 = substr( $string1, $i, 1 );
         } else {
            $c1 = substr( $string2, $i, 1 );
         }
         if( $c1 ne " " ) {
            $same = 0; last;
         }
         $i++;
      }
   }
   return $same;
}