package File::Compare;

use 5.006;
use strict;
use warnings;
our($VERSION, @ISA, @EXPORT, @EXPORT_OK, $Too_Big);

require Exporter;

$VERSION = '1.1006';
@ISA = qw(Exporter);
@EXPORT = qw(compare);
@EXPORT_OK = qw(cmp compare_text);

$Too_Big = 1024 * 1024 * 2;

sub croak {
require Carp;
goto &Carp::croak;
}

sub compare {
croak("Usage: compare( file1, file2 [, buffersize]) ")
unless(@_ == 2 || @_ == 3);

my ($from,$to,$size) = @_;
my $text_mode = defined($size) && (ref($size) eq 'CODE' || $size < 0);

my ($fromsize,$closefrom,$closeto);
local (*FROM, *TO);

croak("from undefined") unless (defined $from);
croak("to undefined") unless (defined $to);

if (ref($from) &&
(UNIVERSAL::isa($from,'GLOB') || UNIVERSAL::isa($from,'IO::Handle'))) {
*FROM = *$from;
} elsif (ref(\$from) eq 'GLOB') {
*FROM = $from;
} else {
open(FROM,"<",$from) or goto fail_open1;
unless ($text_mode) {
binmode FROM;
$fromsize = -s FROM;
}
$closefrom = 1;
}

if (ref($to) &&
(UNIVERSAL::isa($to,'GLOB') || UNIVERSAL::isa($to,'IO::Handle'))) {
*TO = *$to;
} elsif (ref(\$to) eq 'GLOB') {
*TO = $to;
} else {
open(TO,"<",$to) or goto fail_open2;
binmode TO unless $text_mode;
$closeto = 1;
}

if (!$text_mode && $closefrom && $closeto) {
# If both are opened files we know they differ if their size differ
goto fail_inner if $fromsize != -s TO;
}

if ($text_mode) {
local $/ = "\n";
my ($fline,$tline);
while (defined($fline = <FROM>)) {
goto fail_inner unless defined($tline = <TO>);
if (ref $size) {
# $size contains ref to comparison function
goto fail_inner if &$size($fline, $tline);
} else {
goto fail_inner if $fline ne $tline;
}
}
goto fail_inner if defined($tline = <TO>);
}
else {
unless (defined($size) && $size > 0) {
$size = $fromsize || -s TO || 0;
$size = 1024 if $size < 512;
$size = $Too_Big if $size > $Too_Big;
}

my ($fr,$tr,$fbuf,$tbuf);
$fbuf = $tbuf = '';
while(defined($fr = read(FROM,$fbuf,$size)) && $fr > 0) {
unless (defined($tr = read(TO,$tbuf,$fr)) && $tbuf eq $fbuf) {
goto fail_inner;
}
}
goto fail_inner if defined($tr = read(TO,$tbuf,$size)) && $tr > 0;
}

close(TO) || goto fail_open2 if $closeto;
close(FROM) || goto fail_open1 if $closefrom;

return 0;

# All of these contortions try to preserve error messages...
fail_inner:
close(TO) || goto fail_open2 if $closeto;
close(FROM) || goto fail_open1 if $closefrom;

return 1;

fail_open2:
if ($closefrom) {
my $status = $!;
$! = 0;
close FROM;
$! = $status unless $!;
}
fail_open1:
return -1;
}

sub cmp;
*cmp = \&compare;

sub compare_text {
my ($from,$to,$cmp) = @_;
croak("Usage: compare_text( file1, file2 [, cmp-function])")
unless @_ == 2 || @_ == 3;
croak("Third arg to compare_text() function must be a code reference")
if @_ == 3 && ref($cmp) ne 'CODE';

# Using a negative buffer size puts compare into text_mode too
$cmp = -1 unless defined $cmp;
compare($from, $to, $cmp);
}

1;

__END__

=head1 NAME

File::Compare - Compare files or filehandles

=head1 SYNOPSIS

use File::Compare;

if (compare("file1","file2") == 0) {
print "They're equal\n";
}

=head1 DESCRIPTION

The File::Compare::compare function compares the contents of two
sources, each of which can be a file or a file handle. It is exported
from File::Compare by default.

File::Compare::cmp is a synonym for File::Compare::compare. It is
exported from File::Compare only by request.

File::Compare::compare_text does a line by line comparison of the two
files. It stops as soon as a difference is detected. compare_text()
accepts an optional third argument: This must be a CODE reference to
a line comparison function, which returns 0 when both lines are considered
equal. For example:

compare_text($file1, $file2)

is basically equivalent to

compare_text($file1, $file2, sub {$_[0] ne $_[1]} )

=head1 RETURN

File::Compare::compare and its sibling functions return 0 if the files
are equal, 1 if the files are unequal, or -1 if an error was encountered.

=head1 AUTHOR

File::Compare was written by Nick Ing-Simmons.
Its original documentation was written by Chip Salzenberg.

=cut