#!/usr/bin/perl -w
  #
  # Clean a patch file -- or directory of patch files -- of stealth whitespace.
  # WARNING: this can be a highly destructive operation.  Use with caution.
  #
  
  use bytes;
  use File::Basename;
  
  # Default options
  $max_width = 79;
  
  # Clean up space-tab sequences, either by removing spaces or
  # replacing them with tabs.
  sub clean_space_tabs($)
  {
      no bytes;			# Tab alignment depends on characters
  
      my($li) = @_;
      my($lo) = '';
      my $pos = 0;
      my $nsp = 0;
      my($i, $c);
  
      for ($i = 0; $i < length($li); $i++) {
  	$c = substr($li, $i, 1);
  	if ($c eq "\t") {
  	    my $npos = ($pos+$nsp+8) & ~7;
  	    my $ntab = ($npos >> 3) - ($pos >> 3);
  	    $lo .= "\t" x $ntab;
  	    $pos = $npos;
  	    $nsp = 0;
  	} elsif ($c eq "
  " || $c eq "\r") {
  	    $lo .= " " x $nsp;
  	    $pos += $nsp;
  	    $nsp = 0;
  	    $lo .= $c;
  	    $pos = 0;
  	} elsif ($c eq " ") {
  	    $nsp++;
  	} else {
  	    $lo .= " " x $nsp;
  	    $pos += $nsp;
  	    $nsp = 0;
  	    $lo .= $c;
  	    $pos++;
  	}
      }
      $lo .= " " x $nsp;
      return $lo;
  }
  
  # Compute the visual width of a string
  sub strwidth($) {
      no bytes;			# Tab alignment depends on characters
  
      my($li) = @_;
      my($c, $i);
      my $pos = 0;
      my $mlen = 0;
  
      for ($i = 0; $i < length($li); $i++) {
  	$c = substr($li,$i,1);
  	if ($c eq "\t") {
  	    $pos = ($pos+8) & ~7;
  	} elsif ($c eq "
  ") {
  	    $mlen = $pos if ($pos > $mlen);
  	    $pos = 0;
  	} else {
  	    $pos++;
  	}
      }
  
      $mlen = $pos if ($pos > $mlen);
      return $mlen;
  }
  
  $name = basename($0);
  
  @files = ();
  
  while (defined($a = shift(@ARGV))) {
      if ($a =~ /^-/) {
  	if ($a eq '-width' || $a eq '-w') {
  	    $max_width = shift(@ARGV)+0;
  	} else {
  	    print STDERR "Usage: $name [-width #] files...
  ";
  	    exit 1;
  	}
      } else {
  	push(@files, $a);
      }
  }
  
  foreach $f ( @files ) {
      print STDERR "$name: $f
  ";
  
      if (! -f $f) {
  	print STDERR "$f: not a file
  ";
  	next;
      }
  
      if (!open(FILE, '+<', $f)) {
  	print STDERR "$name: Cannot open file: $f: $!
  ";
  	next;
      }
  
      binmode FILE;
  
      # First, verify that it is not a binary file; consider any file
      # with a zero byte to be a binary file.  Is there any better, or
      # additional, heuristic that should be applied?
      $is_binary = 0;
  
      while (read(FILE, $data, 65536) > 0) {
  	if ($data =~ /\0/) {
  	    $is_binary = 1;
  	    last;
  	}
      }
  
      if ($is_binary) {
  	print STDERR "$name: $f: binary file
  ";
  	next;
      }
  
      seek(FILE, 0, 0);
  
      $in_bytes = 0;
      $out_bytes = 0;
      $lineno = 0;
  
      @lines  = ();
  
      $in_hunk = 0;
      $err = 0;
  
      while ( defined($line = <FILE>) ) {
  	$lineno++;
  	$in_bytes += length($line);
  
  	if (!$in_hunk) {
  	    if ($line =~
  		/^\@\@\s+\-([0-9]+),([0-9]+)\s+\+([0-9]+),([0-9]+)\s\@\@/) {
  		$minus_lines = $2;
  		$plus_lines = $4;
  		if ($minus_lines || $plus_lines) {
  		    $in_hunk = 1;
  		    @hunk_lines = ($line);
  		}
  	    } else {
  		push(@lines, $line);
  		$out_bytes += length($line);
  	    }
  	} else {
  	    # We're in a hunk
  
  	    if ($line =~ /^\+/) {
  		$plus_lines--;
  
  		$text = substr($line, 1);
  		$text =~ s/[ \t\r]*$//;		# Remove trailing spaces
  		$text = clean_space_tabs($text);
  
  		$l_width = strwidth($text);
  		if ($max_width && $l_width > $max_width) {
  		    print STDERR
  			"$f:$lineno: adds line exceeds $max_width ",
  			"characters ($l_width)
  ";
  		}
  
  		push(@hunk_lines, '+'.$text);
  	    } elsif ($line =~ /^\-/) {
  		$minus_lines--;
  		push(@hunk_lines, $line);
  	    } elsif ($line =~ /^ /) {
  		$plus_lines--;
  		$minus_lines--;
  		push(@hunk_lines, $line);
  	    } else {
  		print STDERR "$name: $f: malformed patch
  ";
  		$err = 1;
  		last;
  	    }
  
  	    if ($plus_lines < 0 || $minus_lines < 0) {
  		print STDERR "$name: $f: malformed patch
  ";
  		$err = 1;
  		last;
  	    } elsif ($plus_lines == 0 && $minus_lines == 0) {
  		# End of a hunk.  Process this hunk.
  		my $i;
  		my $l;
  		my @h = ();
  		my $adj = 0;
  		my $done = 0;
  
  		for ($i = scalar(@hunk_lines)-1; $i > 0; $i--) {
  		    $l = $hunk_lines[$i];
  		    if (!$done && $l eq "+
  ") {
  			$adj++; # Skip this line
  		    } elsif ($l =~ /^[ +]/) {
  			$done = 1;
  			unshift(@h, $l);
  		    } else {
  			unshift(@h, $l);
  		    }
  		}
  
  		$l = $hunk_lines[0];  # Hunk header
  		undef @hunk_lines;    # Free memory
  
  		if ($adj) {
  		    die unless
  			($l =~ /^\@\@\s+\-([0-9]+),([0-9]+)\s+\+([0-9]+),([0-9]+)\s\@\@(.*)$/);
  		    my $mstart = $1;
  		    my $mlin = $2;
  		    my $pstart = $3;
  		    my $plin = $4;
  		    my $tail = $5; # doesn't include the final newline
  
  		    $l = sprintf("@@ -%d,%d +%d,%d @@%s
  ",
  				 $mstart, $mlin, $pstart, $plin-$adj,
  				 $tail);
  		}
  		unshift(@h, $l);
  
  		# Transfer to the output array
  		foreach $l (@h) {
  		    $out_bytes += length($l);
  		    push(@lines, $l);
  		}
  
  		$in_hunk = 0;
  	    }
  	}
      }
  
      if ($in_hunk) {
  	print STDERR "$name: $f: malformed patch
  ";
  	$err = 1;
      }
  
      if (!$err) {
  	if ($in_bytes != $out_bytes) {
  	    # Only write to the file if changed
  	    seek(FILE, 0, 0);
  	    print FILE @lines;
  
  	    if ( !defined($where = tell(FILE)) ||
  		 !truncate(FILE, $where) ) {
  		die "$name: Failed to truncate modified file: $f: $!
  ";
  	    }
  	}
      }
  
      close(FILE);
  }