cleanpatch: a script to clean up stealth whitespace added by a patch

#!/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;

#

# 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 "\n" || $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;

}

$name = basename($0);

foreach $f ( @ARGV ) {

    print STDERR "$name: $f\n";

    if (! -f $f) {

	print STDERR "$f: not a file\n";

	next;

    }

    if (!open(FILE, '+<', $f)) {

	print STDERR "$name: Cannot open file: $f: $!\n";

	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\n";

	next;

    }

    seek(FILE, 0, 0);

    $in_bytes = 0;

    $out_bytes = 0;

    @lines  = ();

    $in_hunk = 0;

    $err = 0;

    while ( defined($line = <FILE>) ) {

	$in_bytes += length($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);

		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\n";

		$err = 1;

		last;

	    }

	    if ($plus_lines < 0 || $minus_lines < 0) {

		print STDERR "$name: $f: malformed patch\n";

		$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 "+\n") {

			$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\n",

				 $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\n";

	$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: $!\n";

	    }

	}

    }

    close(FILE);

}