source: vendor/perl/5.8.8/t/io/crlf.t

#!./perl -w

BEGIN {
    chdir 't' if -d 't';
    @INC = qw(. ../lib);
}

use Config;

require "test.pl";

my $file = "crlf$$.dat";
END {
    1 while unlink($file);
}

if (find PerlIO::Layer 'perlio') {
    plan(tests => 16);
    ok(open(FOO,">:crlf",$file));
    ok(print FOO 'a'.((('a' x 14).qq{\n}) x 2000) || close(FOO));
    ok(open(FOO,"<:crlf",$file));

    my $text;
    { local $/; $text = <FOO> }
    is(count_chars($text, "\015\012"), 0);
    is(count_chars($text, "\n"), 2000);

    binmode(FOO);
    seek(FOO,0,0);
    { local $/; $text = <FOO> }
    is(count_chars($text, "\015\012"), 2000);

    SKIP:
    {
        skip("miniperl can't rely on loading PerlIO::scalar")
        if $ENV{PERL_CORE_MINITEST};
        skip("no PerlIO::scalar") unless $Config{extensions} =~ m!\bPerlIO/scalar\b!;
        require PerlIO::scalar;
        my $fcontents = join "", map {"$_\015\012"} "a".."zzz";
        open my $fh, "<:crlf", \$fcontents;
        local $/ = "xxx";
        local $_ = <$fh>;
        my $pos = tell $fh; # pos must be behind "xxx", before "\nxxy\n"
        seek $fh, $pos, 0;
        $/ = "\n";
        $s = <$fh>.<$fh>;
        ok($s eq "\nxxy\n");
    }

    ok(close(FOO));

    # binmode :crlf should not cumulate.
    # Try it first once and then twice so that even UNIXy boxes
    # get to exercise this, for DOSish boxes even once is enough.
    # Try also pushing :utf8 first so that there are other layers
    # in between (this should not matter: CRLF layers still should
    # not accumulate).
    for my $utf8 ('', ':utf8') {
        for my $binmode (1..2) {
            open(FOO, ">$file");
            # require PerlIO; print PerlIO::get_layers(FOO), "\n";
            binmode(FOO, "$utf8:crlf") for 1..$binmode;
            # require PerlIO; print PerlIO::get_layers(FOO), "\n";
            print FOO "Hello\n";
            close FOO;
            open(FOO, "<$file");
            binmode(FOO);
            my $foo = scalar <FOO>;
            close FOO;
            print join(" ", "#", map { sprintf("%02x", $_) } unpack("C*", $foo)),
            "\n";
            ok($foo =~ /\x0d\x0a$/);
            ok($foo !~ /\x0d\x0d/);
        }
    }
}
else {
    skip_all("No perlio, so no :crlf");
}

sub count_chars {
    my($text, $chars) = @_;
    my $seen = 0;
    $seen++ while $text =~ /$chars/g;
    return $seen;
}