More EBCDIC stuff:

[p5sagit/p5-mst-13.2.git] / lib / open.pm

diff --git a/lib/open.pm b/lib/open.pm
index da8a044..53ae308 100644 (file)
--- a/lib/open.pm
+++ b/lib/open.pm
@@ -1,4 +1,52 @@
 package open;
+use Carp;
+$open::hint_bits = 0x20000;
+
+use vars qw(%layers @layers);
+
+# Populate hash in non-PerlIO case
+%layers = (crlf => 1, raw => 0) unless (@layers);
+
+# warn join(',',keys %layers);
+
+our $VERSION = '1.00';
+
+sub import {
+    my ($class,@args) = @_;
+    croak("`use open' needs explicit list of disciplines") unless @args;
+    $^H |= $open::hint_bits;
+    my ($in,$out) = split(/\0/,(${^OPEN} || '\0'));
+    my @in  = split(/\s+/,$in);
+    my @out = split(/\s+/,$out);
+    while (@args) {
+       my $type = shift(@args);
+       my $discp = shift(@args);
+       my @val;
+       foreach my $layer (split(/\s+/,$discp)) {
+            $layer =~ s/^://;
+           unless(exists $layers{$layer}) {
+               carp("Unknown discipline layer '$layer'");
+           }
+           push(@val,":$layer");
+           if ($layer =~ /^(crlf|raw)$/) {
+               $^H{"open_$type"} = $layer;
+           }
+       }
+       if ($type eq 'IN') {
+           $in  = join(' ',@val);
+       }
+       elsif ($type eq 'OUT') {
+           $out = join(' ',@val);
+       }
+       else {
+           croak "Unknown discipline class '$type'";
+       }
+    }
+    ${^OPEN} = join('\0',$in,$out);
+}
+
+1;
+__END__
 
 =head1 NAME
 
@@ -6,31 +54,48 @@ open - perl pragma to set default disciplines for input and output
 
 =head1 SYNOPSIS
 
-    use open IN => ":any", OUT => ":utf8";     # unimplemented
+    use open IN => ":crlf", OUT => ":raw";
 
 =head1 DESCRIPTION
 
-NOTE: This pragma is not yet implemented.
-
 The open pragma is used to declare one or more default disciplines for
-I/O operations.  Any constructors for file, socket, pipe, or directory
-handles found within the lexical scope of this pragma will use the
-declared default.
+I/O operations.  Any open() and readpipe() (aka qx//) operators found
+within the lexical scope of this pragma will use the declared defaults.
+Neither open() with an explicit set of disciplines, nor sysopen() are
+influenced by this pragma.
 
-Handle constructors that are called with an explicit set of disciplines
-are not influenced by the declared defaults.
+Only the two pseudo-disciplines ":raw" and ":crlf" are currently
+available.
 
-The default disciplines so declared are available by the special
-discipline name ":def", and can be used within handle constructors
-that allow disciplines to be specified.  This makes it possible to
-stack new disciplines over the default ones.
+The ":raw" discipline corresponds to "binary mode" and the ":crlf"
+discipline corresponds to "text mode" on platforms that distinguish
+between the two modes when opening files (which is many DOS-like
+platforms, including Windows).  These two disciplines are currently
+no-ops on platforms where binmode() is a no-op, but will be
+supported everywhere in future.
 
-    open FH, "<:para :def", $file or die "can't open $file: $!";
+=head1 UNIMPLEMENTED FUNCTIONALITY
+
+Full-fledged support for I/O disciplines is currently unimplemented.
+When they are eventually supported, this pragma will serve as one of
+the interfaces to declare default disciplines for all I/O.
+
+In future, any default disciplines declared by this pragma will be
+available by the special discipline name ":DEFAULT", and could be used
+within handle constructors that allow disciplines to be specified.
+This would make it possible to stack new disciplines over the default
+ones.
+
+    open FH, "<:para :DEFAULT", $file or die "can't open $file: $!";
+
+Socket and directory handles will also support disciplines in
+future.
+
+Full support for I/O disciplines will enable all of the supported
+disciplines to work on all platforms.
 
 =head1 SEE ALSO
 
-L<perlunicode>, L<perlfunc/"open">
+L<perlfunc/"binmode">, L<perlfunc/"open">, L<perlunicode>
 
 =cut
-
-1;