From: Jarkko Hietaniemi Date: Mon, 28 May 2001 15:09:24 +0000 (+0000) Subject: Linerewrapping. X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=d151aa0ec14d76b1fc090f7a4c70252742dc3539;p=p5sagit%2Fp5-mst-13.2.git Linerewrapping. p4raw-id: //depot/perl@10249 --- diff --git a/lib/open.pm b/lib/open.pm index 1aef904..c90181b 100644 --- a/lib/open.pm +++ b/lib/open.pm @@ -59,57 +59,61 @@ open - perl pragma to set default disciplines for input and output =head1 DESCRIPTION -Full-fledged support for I/O disciplines is now implemented provided perl is -configured to use PerlIO as its IO system (which is now the default). +Full-fledged support for I/O disciplines is now implemented provided +Perl is configured to use PerlIO as its IO system (which is now the +default). The C pragma serves as one of the interfaces to declare default "layers" (aka disciplines) for all I/O. The C pragma is used to declare one or more default layers for -I/O operations. Any open(), readpipe() (aka qx//) and similar operators -found within the lexical scope of this pragma will use the declared defaults. +I/O operations. Any open(), readpipe() (aka qx//) and similar +operators found within the lexical scope of this pragma will use the +declared defaults. -When open() is given an explicit list of layers they are appended to the -list declared using this pragma. +When open() is given an explicit list of layers they are appended to +the list declared using this pragma. Directory handles may also support disciplines in future. =head1 NONPERLIO FUNCTIONALITY -If perl is not built to use PerlIO as its IO system then only the two pseudo-disciplines -":raw" and ":crlf" are available. +If Perl is not built to use PerlIO as its IO system then only the two +pseudo-disciplines ":raw" and ":crlf" are available. 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 -no-ops on platforms where binmode() is a no-op, but perform their -functions everywhere if PerlIO is enabled. +platforms, including Windows). These two disciplines are no-ops on +platforms where binmode() is a no-op, but perform their functions +everywhere if PerlIO is enabled. =head1 IMPLEMENTATION DETAILS -There are two package variables C<%layers> and C<@layers> which -are mainly manipulated by C code in F, but are visible -to the nosy: +There are two package variables C<%layers> and C<@layers> which are +mainly manipulated by C code in F, but are visible to the +nosy: print "Have ",join(',',keys %open::layers),"\n"; print "Using ",join(',',@open::layers),"\n"; -The C<%open::layers> hash is a record of the available "layers" that may be pushed -onto a C stream. The values of the hash are perl objects, of class C -which are created by the C code in F. As yet there is nothing useful you -can do with the objects at the perl level. - -The C<@open::layers> array is the current set of layers and their arguments. -The array consists of layer => argument pairs and I always have even number of -entries and the even entries I be C objects or perl will "die" -when it attempts to open a filehandle. In most cases the odd entry will be C, -but in the case of (say) ":encoding(iso-8859-1)" it will be 'iso-8859-1'. These +The C<%open::layers> hash is a record of the available "layers" that +may be pushed onto a C stream. The values of the hash are Perl +objects, of class C which are created by the C code in +F. As yet there is nothing useful you can do with the +objects at the perl level. + +The C<@open::layers> array is the current set of layers and their +arguments. The array consists of layer => argument pairs and I +always have even number of entries and the even entries I be +C objects or Perl will "die" when it attempts to open a +filehandle. In most cases the odd entry will be C, but in the +case of (say) ":encoding(iso-8859-1)" it will be 'iso-8859-1'. These argument entries are currently restricted to being strings. -When a new C stream is opened, the C code looks at the -array to determine the default layers to be pushed. So with care it is possible -to manipulate the default layer "stack": +When a new C stream is opened, the C code looks at the array +to determine the default layers to be pushed. So with care it is +possible to manipulate the default layer "stack": splice(@PerlIO::layers,-2,2); push(@PerlIO::layers,$PerlIO::layers{'stdio'} => undef);