# IO::Pipe.pm
#
# Copyright (c) 1996-8 Graham Barr <[email protected]>. All rights reserved.
# This program is free software; you can redistribute it and/or
# modify it under the same terms as Perl itself.

package IO::Pipe;

use 5.006_001;

use IO::Handle;
use strict;
our($VERSION);
use Carp;
use Symbol;

$VERSION = "1.13";

sub new {
my $type = shift;
my $class = ref($type) || $type || "IO::Pipe";
@_ == 0 || @_ == 2 or croak "usage: new $class [READFH, WRITEFH]";

my $me = bless gensym(), $class;

my($readfh,$writefh) = @_ ? @_ : $me->handles;

pipe($readfh, $writefh)
or return undef;

@{*$me} = ($readfh, $writefh);

$me;
}

sub handles {
@_ == 1 or croak 'usage: $pipe->handles()';
(IO::Pipe::End->new(), IO::Pipe::End->new());
}

my $do_spawn = $^O eq 'os2' || $^O eq 'MSWin32';

sub _doit {
my $me = shift;
my $rw = shift;

my $pid = $do_spawn ? 0 : fork();

if($pid) { # Parent
return $pid;
}
elsif(defined $pid) { # Child or spawn
my $fh;
my $io = $rw ? \*STDIN : \*STDOUT;
my ($mode, $save) = $rw ? "r" : "w";
if ($do_spawn) {
require Fcntl;
$save = IO::Handle->new_from_fd($io, $mode);
my $handle = shift;
# Close in child:
unless ($^O eq 'MSWin32') {
fcntl($handle, Fcntl::F_SETFD(), 1) or croak "fcntl: $!";
}
$fh = $rw ? ${*$me}[0] : ${*$me}[1];
} else {
shift;
$fh = $rw ? $me->reader() : $me->writer(); # close the other end
}
bless $io, "IO::Handle";
$io->fdopen($fh, $mode);
$fh->close;

if ($do_spawn) {
$pid = eval { system 1, @_ }; # 1 == P_NOWAIT
my $err = $!;

$io->fdopen($save, $mode);
$save->close or croak "Cannot close $!";
croak "IO::Pipe: Cannot spawn-NOWAIT: $err" if not $pid or $pid < 0;
return $pid;
} else {
exec @_ or
croak "IO::Pipe: Cannot exec: $!";
}
}
else {
croak "IO::Pipe: Cannot fork: $!";
}

# NOT Reached
}

sub reader {
@_ >= 1 or croak 'usage: $pipe->reader( [SUB_COMMAND_ARGS] )';
my $me = shift;

return undef
unless(ref($me) || ref($me = $me->new));

my $fh = ${*$me}[0];
my $pid;
$pid = $me->_doit(0, $fh, @_)
if(@_);

close ${*$me}[1];
bless $me, ref($fh);
*$me = *$fh; # Alias self to handle
$me->fdopen($fh->fileno,"r")
unless defined($me->fileno);
bless $fh; # Really wan't un-bless here
${*$me}{'io_pipe_pid'} = $pid
if defined $pid;

$me;
}

sub writer {
@_ >= 1 or croak 'usage: $pipe->writer( [SUB_COMMAND_ARGS] )';
my $me = shift;

return undef
unless(ref($me) || ref($me = $me->new));

my $fh = ${*$me}[1];
my $pid;
$pid = $me->_doit(1, $fh, @_)
if(@_);

close ${*$me}[0];
bless $me, ref($fh);
*$me = *$fh; # Alias self to handle
$me->fdopen($fh->fileno,"w")
unless defined($me->fileno);
bless $fh; # Really wan't un-bless here
${*$me}{'io_pipe_pid'} = $pid
if defined $pid;

$me;
}

package IO::Pipe::End;

our(@ISA);

@ISA = qw(IO::Handle);

sub close {
my $fh = shift;
my $r = $fh->SUPER::close(@_);

waitpid(${*$fh}{'io_pipe_pid'},0)
if(defined ${*$fh}{'io_pipe_pid'});

$r;
}

1;

__END__

=head1 NAME

IO::Pipe - supply object methods for pipes

=head1 SYNOPSIS

use IO::Pipe;

$pipe = new IO::Pipe;

if($pid = fork()) { # Parent
$pipe->reader();

while(<$pipe>) {
...
}

}
elsif(defined $pid) { # Child
$pipe->writer();

print $pipe ...
}

or

$pipe = new IO::Pipe;

$pipe->reader(qw(ls -l));

while(<$pipe>) {
...
}

=head1 DESCRIPTION

C<IO::Pipe> provides an interface to creating pipes between
processes.

=head1 CONSTRUCTOR

=over 4

=item new ( [READER, WRITER] )

Creates an C<IO::Pipe>, which is a reference to a newly created symbol
(see the C<Symbol> package). C<IO::Pipe::new> optionally takes two
arguments, which should be objects blessed into C<IO::Handle>, or a
subclass thereof. These two objects will be used for the system call
to C<pipe>. If no arguments are given then method C<handles> is called
on the new C<IO::Pipe> object.

These two handles are held in the array part of the GLOB until either
C<reader> or C<writer> is called.

=back

=head1 METHODS

=over 4

=item reader ([ARGS])

The object is re-blessed into a sub-class of C<IO::Handle>, and becomes a
handle at the reading end of the pipe. If C<ARGS> are given then C<fork>
is called and C<ARGS> are passed to exec.

=item writer ([ARGS])

The object is re-blessed into a sub-class of C<IO::Handle>, and becomes a
handle at the writing end of the pipe. If C<ARGS> are given then C<fork>
is called and C<ARGS> are passed to exec.

=item handles ()

This method is called during construction by C<IO::Pipe::new>
on the newly created C<IO::Pipe> object. It returns an array of two objects
blessed into C<IO::Pipe::End>, or a subclass thereof.

=back

=head1 SEE ALSO

L<IO::Handle>

=head1 AUTHOR

Graham Barr. Currently maintained by the Perl Porters. Please report all
bugs to <[email protected]>.

=head1 COPYRIGHT

Copyright (c) 1996-8 Graham Barr <[email protected]>. All rights reserved.
This program is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.

=cut