#!/usr/bin/perl
#
# Clean a text file of stealth whitespace
#

use bytes;

$name = 'cleanfile';

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
    $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);

    @blanks = ();
    @lines  = ();

    while ( defined($line = <FILE>) ) {
	$line =~ s/[ \t\r\n]*$/\n/;

	if ( $line eq "\n" ) {
	    push(@blanks, $line);
	} else {
	    push(@lines, @blanks);
	    push(@lines, $line);
	    @blanks = ();
	}
    }

    # Any blanks at the end of the file are discarded

    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);
}