X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FPerlIO.pm;h=5777679bfaaeff3e13b3729fa479f34cd53c7820;hb=ce4f4a1cb8714c6c6c3c7b002c9830a7cafc6780;hp=672efb2324356ddd641f509b975df976c52a28fb;hpb=80fea0d2bcf08e174a74010b6dc3b53a2700dacd;p=p5sagit%2Fp5-mst-13.2.git diff --git a/lib/PerlIO.pm b/lib/PerlIO.pm index 672efb2..5777679 100644 --- a/lib/PerlIO.pm +++ b/lib/PerlIO.pm @@ -1,6 +1,6 @@ package PerlIO; -our $VERSION = '1.01'; +our $VERSION = '1.02'; # Map layer name to package that defines it our %alias; @@ -24,6 +24,8 @@ sub import } } +sub F_UTF8 () { 0x8000 } + 1; __END__ @@ -113,20 +115,20 @@ to a such a stream. =item raw The C<:raw> layer is I as being identical to calling -C - the stream is made suitable for passing binary -data i.e. each byte is passed as-is. The stream will still be -buffered. Unlike earlier versions of perl C<:raw> is I just the -inverse of C<:crlf> - other layers which would affect the binary nature of -the stream are also removed or disabled. +C - the stream is made suitable for passing binary data +i.e. each byte is passed as-is. The stream will still be +buffered. Unlike in the earlier versions of Perl C<:raw> is I +just the inverse of C<:crlf> - other layers which would affect the +binary nature of the stream are also removed or disabled. The implementation of C<:raw> is as a pseudo-layer which when "pushed" pops itself and then any layers which do not declare themselves as suitable for binary data. (Undoing :utf8 and :crlf are implemented by clearing -flags rather than poping layers but that is an implementation detail.) +flags rather than popping layers but that is an implementation detail.) As a consequence of the fact that C<:raw> normally pops layers -it usually only makes sense to have it as the only or first element in a -layer specification. When used as the first element it provides +it usually only makes sense to have it as the only or first element in +a layer specification. When used as the first element it provides a known base on which to build e.g. open($fh,":raw:utf8",...) @@ -151,6 +153,31 @@ A more elegant (and safer) interface is needed. =back +=head2 Custom Layers + +It is possible to write custom layers in addition to the above builtin +ones, both in C/XS and Perl. Two such layers (and one example written +in Perl using the latter) come with the Perl distribution. + +=over 4 + +=item :encoding + +Use C<:encoding(ENCODING)> either in open() or binmode() to install +a layer that does transparently character set and encoding transformations, +for example from Shift-JIS to Unicode. Note that under C +an C<:encoding> also enables C<:utf8>. See L +for more information. + +=item :via + +Use C<:via(MODULE)> either in open() or binmode() to install a layer +that does whatever transformation (for example compression / +decompression, encryption / decryption) to the filehandle. +See L for more information. + +=back + =head2 Alternatives to raw To get a binary stream an alternate method is to use: @@ -177,7 +204,7 @@ translation for text files then the default layers are : level layer.) Otherwise if C found out how to do "fast" IO using system's -stdio, then the default layers are : +stdio, then the default layers are: unix stdio @@ -188,8 +215,8 @@ Otherwise the default layers are These defaults may change once perlio has been better tested and tuned. The default can be overridden by setting the environment variable -PERLIO to a space separated list of layers (unix or platform low level -layer is always pushed first). +PERLIO to a space separated list of layers (C or platform low +level layer is always pushed first). This can be used to see the effect of/bugs in the various layers e.g. @@ -197,13 +224,70 @@ This can be used to see the effect of/bugs in the various layers e.g. PERLIO=stdio ./perl harness PERLIO=perlio ./perl harness +For the various value of PERLIO see L. + +=head2 Querying the layers of filehandle + +The following returns the B of the PerlIO layers on a filehandle. + + my @layers = PerlIO::get_layers($fh); # Or FH, *FH, "FH". + +The layers are returned in the order an open() or binmode() call would +use them. Note that the "default stack" depends on the operating +system and on the perl version. + +The following table summarizes the default layers on UNIX-like and +DOS-like platforms and depending on the setting of the C<$ENV{PERLIO}>: + + PERLIO UNIX-like DOS-like + + unset / "" unix perlio / stdio [1] unix crlf + stdio unix perlio / stdio [1] stdio + perlio unix perlio unix perlio + mmap unix mmap unix mmap + + # [1] "stdio" if Configure found out how to do "fast stdio" (depends + # on the stdio implementation) and in Perl 5.8, otherwise "unix perlio" + +By default the layers from the input side of the filehandle is +returned, to get the output side use the optional C argument: + + my @layers = PerlIO::get_layers($fh, output => 1); + +(Usually the layers are identical on either side of a filehandle but +for example with sockets there may be differences, or if you have +been using the C pragma.) + +There is no set_layers(), nor does get_layers() return a tied array +mirroring the stack, or anything fancy like that. This is not +accidental or unintentional. The PerlIO layer stack is a bit more +complicated than just a stack (see for example the behaviour of C<:raw>). +You are supposed to use open() and binmode() to manipulate the stack. + +B + +The arguments to layers are by default returned in parenthesis after +the name of the layer, and certain layers (like C) are not real +layers but instead flags on real layers: to get all of these returned +separately use the optional C argument: + + my @layer_and_args_and_flags = PerlIO::get_layers($fh, details => 1); + +The result will be up to be three times the number of layers: +the first element will be a name, the second element the arguments +(unspecified arguments will be C), the third element the flags, +the fourth element a name again, and so forth. + +B + =head1 AUTHOR Nick Ing-Simmons Enick@ing-simmons.netE =head1 SEE ALSO -L, L, L, L, L +L, L, L, L, +L =cut