package MIME::Decoder; =head1 NAME MIME::Decoder - an object for decoding the body part of a MIME stream =head1 SYNOPSIS Before reading further, you should see L to make sure that you understand where this module fits into the grand scheme of things. Go on, do it now. I'll wait. Ready? Ok... =head2 Decoding a data stream Here's a simple filter program to read quoted-printable data from STDIN (until EOF) and write the decoded data to STDOUT: use MIME::Decoder; $decoder = new MIME::Decoder 'quoted-printable' or die "unsupported"; $decoder->decode(\*STDIN, \*STDOUT); =head2 Encoding a data stream Here's a simple filter program to read binary data from STDIN (until EOF) and write base64-encoded data to STDOUT: use MIME::Decoder; $decoder = new MIME::Decoder 'base64' or die "unsupported"; $decoder->encode(\*STDIN, \*STDOUT); =head2 Non-standard encodings You can B your own decoders so that MIME::Decoder will know about them: use MyBase64Decoder; install MyBase64Decoder 'base64'; You can also B if a given encoding is supported: if (supported MIME::Decoder 'x-uuencode') { ### we can uuencode! } =head1 DESCRIPTION This abstract class, and its private concrete subclasses (see below) provide an OO front end to the actions of... =over 4 =item * Decoding a MIME-encoded stream =item * Encoding a raw data stream into a MIME-encoded stream. =back The constructor for MIME::Decoder takes the name of an encoding (C, C<7bit>, etc.), and returns an instance of a I of MIME::Decoder whose C method will perform the appropriate decoding action, and whose C method will perform the appropriate encoding action. =cut ### Pragmas: use strict; use vars qw($VERSION %DecoderFor); ### System modules: use FileHandle; use IPC::Open2; ### Kit modules: use MIME::Tools qw(:config :msgs); use IO::Wrap; use Carp; #------------------------------ # # Globals # #------------------------------ ### The stream decoders: %DecoderFor = ( ### Standard... '7bit' => 'MIME::Decoder::NBit', '8bit' => 'MIME::Decoder::NBit', 'base64' => 'MIME::Decoder::Base64', 'binary' => 'MIME::Decoder::Binary', 'none' => 'MIME::Decoder::Binary', 'quoted-printable' => 'MIME::Decoder::QuotedPrint', ### Non-standard... 'x-uu' => 'MIME::Decoder::UU', 'x-uuencode' => 'MIME::Decoder::UU', ### This was removed, since I fear that x-gzip != x-gzip64... ### 'x-gzip' => 'MIME::Decoder::Gzip64', ### This is no longer installed by default, since not all folks have gzip: ### 'x-gzip64' => 'MIME::Decoder::Gzip64', ); ### The package version, both in 1.23 style *and* usable by MakeMaker: $VERSION = substr q$Revision: 1.1 $, 10; ### Me: my $ME = 'MIME::Decoder'; #------------------------------ =head1 PUBLIC INTERFACE =head2 Standard interface If all you are doing is I this class, here's all you'll need... =over 4 =cut #------------------------------ =item new ENCODING I Create and return a new decoder object which can handle the given ENCODING. my $decoder = new MIME::Decoder "7bit"; Returns the undefined value if no known decoders are appropriate. =cut sub new { my ($class, @args) = @_; my ($encoding) = @args; my ($concrete_name, $concrete_path); ### Coerce the type to be legit: $encoding = lc($encoding || ''); ### Get the class: ($concrete_name = $DecoderFor{$encoding}) or return undef; ($concrete_path = $concrete_name.'.pm') =~ s{::}{/}g; ### Create the new object (if we can): my $self = { MD_Encoding => lc($encoding) }; require $concrete_path; bless $self, $concrete_name; $self->init(@args); } #------------------------------ =item best ENCODING I Exactly like new(), except that this defaults any unsupported encoding to "binary", after raising a suitable warning (it's a fatal error if there's no binary decoder). my $decoder = best MIME::Decoder "x-gzip64"; Will either return a decoder, or a raise a fatal exception. =cut sub best { my ($class, $enc, @args) = @_; my $self = $class->new($enc, @args); if (!$self) { usage "unsupported encoding '$enc': using 'binary'"; $self = $class->new('binary') || croak "ack! no binary decoder!"; } $self; } #------------------------------ =item decode INSTREAM,OUTSTREAM I Decode the document waiting in the input handle INSTREAM, writing the decoded information to the output handle OUTSTREAM. Read the section in this document on I/O handles for more information about the arguments. Note that you can still supply old-style unblessed filehandles for INSTREAM and OUTSTREAM. Returns true on success, throws exception on failure. =cut sub decode { my ($self, $in, $out) = @_; ### Set up the default input record separator to be CRLF: ### $in->input_record_separator("\012\015"); ### Coerce old-style filehandles to legit objects, and do it! $in = wraphandle($in); $out = wraphandle($out); ### Invoke back-end method to do the work: $self->decode_it($in, $out) || die "$ME: ".$self->encoding." decoding failed\n"; 1; } #------------------------------ =item encode INSTREAM,OUTSTREAM I Encode the document waiting in the input filehandle INSTREAM, writing the encoded information to the output stream OUTSTREAM. Read the section in this document on I/O handles for more information about the arguments. Note that you can still supply old-style unblessed filehandles for INSTREAM and OUTSTREAM. Returns true on success, throws exception on failure. =cut sub encode { my ($self, $in, $out) = @_; ### Coerce old-style filehandles to legit objects, and do it! $in = wraphandle($in); $out = wraphandle($out); ### Invoke back-end method to do the work: $self->encode_it($in, $out) || die "$ME: ".$self->encoding." encoding failed\n"; } #------------------------------ =item encoding I Return the encoding that this object was created to handle, coerced to all lowercase (e.g., C<"base64">). =cut sub encoding { shift->{MD_Encoding}; } #------------------------------ =item head [HEAD] I Completely optional: some decoders need to know a little about the file they are encoding/decoding; e.g., x-uu likes to have the filename. The HEAD is any object which responds to messages like: $head->mime_attr('content-disposition.filename'); =cut sub head { my ($self, $head) = @_; $self->{MD_Head} = $head if @_ > 1; $self->{MD_Head}; } #------------------------------ =item supported [ENCODING] I With one arg (an ENCODING name), returns truth if that encoding is currently handled, and falsity otherwise. The ENCODING will be automatically coerced to lowercase: if (supported MIME::Decoder '7BIT') { ### yes, we can handle it... } else { ### drop back six and punt... } With no args, returns a reference to a hash of all available decoders, where the key is the encoding name (all lowercase, like '7bit'), and the value is true (it happens to be the name of the class that handles the decoding, but you probably shouldn't rely on that). You may safely modify this hash; it will I change the way the module performs its lookups. Only C can do that. I =cut sub supported { my ($class, $decoder) = @_; defined($decoder) ? $DecoderFor{lc($decoder)}: { %DecoderFor }; } #------------------------------ =back =head2 Subclass interface If you are writing (or installing) a new decoder subclass, there are some other methods you'll need to know about: =over 4 =cut #------------------------------ =item decode_it INSTREAM,OUTSTREAM I The back-end of the B method. It takes an input handle opened for reading (INSTREAM), and an output handle opened for writing (OUTSTREAM). If you are writing your own decoder subclass, you must override this method in your class. Your method should read from the input handle via C or C, decode this input, and print the decoded data to the output handle via C. You may do this however you see fit, so long as the end result is the same. Note that unblessed references and globrefs are automatically turned into I/O handles for you by C, so you don't need to worry about it. Your method must return either C (to indicate failure), or C<1> (to indicate success). It may also throw an exception to indicate failure. =cut sub decode_it { die "attempted to use abstract 'decode_it' method!"; } #------------------------------ =item encode_it INSTREAM,OUTSTREAM I The back-end of the B method. It takes an input handle opened for reading (INSTREAM), and an output handle opened for writing (OUTSTREAM). If you are writing your own decoder subclass, you must override this method in your class. Your method should read from the input handle via C or C, encode this input, and print the encoded data to the output handle via C. You may do this however you see fit, so long as the end result is the same. Note that unblessed references and globrefs are automatically turned into I/O handles for you by C, so you don't need to worry about it. Your method must return either C (to indicate failure), or C<1> (to indicate success). It may also throw an exception to indicate failure. =cut sub encode_it { die "attempted to use abstract 'encode_it' method!"; } #------------------------------ =item filter IN, OUT, COMMAND... I If your decoder involves an external program, you can invoke them easily through this method. The command must be a "filter": a command that reads input from its STDIN (which will come from the IN argument) and writes output to its STDOUT (which will go to the OUT argument). For example, here's a decoder that un-gzips its data: sub decode_it { my ($self, $in, $out) = @_; $self->filter($in, $out, "gzip -d -"); } The usage is similar to IPC::Open2::open2 (which it uses internally), so you can specify COMMAND as a single argument or as an array. =cut sub filter { my ($self, $in, $out, @cmd) = @_; my $buf = ''; ### Make sure we've got MIME::IO-compliant objects: $in = wraphandle($in); $out = wraphandle($out); ### Open pipe: STDOUT->flush; ### very important, or else we get duplicate output! my $kidpid = open2(\*CHILDOUT, \*CHILDIN, @cmd) || die "open2 failed: $!"; ### Write all: while ($in->read($buf, 2048)) { print CHILDIN $buf } close \*CHILDIN; ### Read all: while (read(\*CHILDOUT, $buf, 2048)) { $out->print($buf) } close \*CHILDOUT; ### Wait for it: waitpid($kidpid,0) or die "couldn't reap child $kidpid"; 1; } #------------------------------ =item init ARGS... I Do any necessary initialization of the new instance, taking whatever arguments were given to C. Should return the self object on success, undef on failure. =cut sub init { $_[0]; } #------------------------------ =item install ENCODINGS... I. Install this class so that each encoding in ENCODINGS is handled by it: install MyBase64Decoder 'base64', 'x-base64super'; You should not override this method. =cut sub install { my $class = shift; $DecoderFor{lc(shift @_)} = $class while (@_); } #------------------------------ =item uninstall ENCODINGS... I. Uninstall support for encodings. This is a way to turn off the decoding of "experimental" encodings. For safety, always use MIME::Decoder directly: uninstall MIME::Decoder 'x-uu', 'x-uuencode'; You should not override this method. =cut sub uninstall { shift; $DecoderFor{lc(shift @_)} = undef while (@_); } 1; __END__ #------------------------------ =back =head1 DECODER SUBCLASSES You don't need to C<"use"> any other Perl modules; the following "standard" subclasses are included as part of MIME::Decoder: Class: Handles encodings: ------------------------------------------------------------ MIME::Decoder::Binary binary MIME::Decoder::NBit 7bit, 8bit MIME::Decoder::Base64 base64 MIME::Decoder::QuotedPrint quoted-printable The following "non-standard" subclasses are also included: Class: Handles encodings: ------------------------------------------------------------ MIME::Decoder::UU x-uu, x-uuencode MIME::Decoder::Gzip64 x-gzip64 ** requires gzip! =head1 NOTES =head2 Input/Output handles As of MIME-tools 2.0, this class has to play nice with the new MIME::Body class... which means that input and output routines cannot just assume that they are dealing with filehandles. Therefore, all that MIME::Decoder and its subclasses require (and, thus, all that they can assume) is that INSTREAMs and OUTSTREAMs are objects which respond to a subset of the messages defined in the IO::Handle interface; minimally: print getline read(BUF,NBYTES) For backwards compatibilty, if you supply a scalar filehandle name (like C<"STDOUT">) or an unblessed glob reference (like C<\*STDOUT>) where an INSTREAM or OUTSTREAM is expected, this package will automatically wrap it in an object that fits these criteria, via IO::Wrap. I =head2 Writing a decoder If you're experimenting with your own encodings, you'll probably want to write a decoder. Here are the basics: =over 4 =item 1. Create a module, like "MyDecoder::", for your decoder. Declare it to be a subclass of MIME::Decoder. =item 2. Create the following instance methods in your class, as described above: decode_it encode_it init =item 3. In your application program, activate your decoder for one or more encodings like this: require MyDecoder; install MyDecoder "7bit"; ### use MyDecoder to decode "7bit" install MyDecoder "x-foo"; ### also use MyDecoder to decode "x-foo" =back To illustrate, here's a custom decoder class for the C encoding: package MyQPDecoder; @ISA = qw(MIME::Decoder); use MIME::Decoder; use MIME::QuotedPrint; ### decode_it - the private decoding method sub decode_it { my ($self, $in, $out) = @_; while (defined($_ = $in->getline)) { my $decoded = decode_qp($_); $out->print($decoded); } 1; } ### encode_it - the private encoding method sub encode_it { my ($self, $in, $out) = @_; my ($buf, $nread) = ('', 0); while ($in->read($buf, 60)) { my $encoded = encode_qp($buf); $out->print($encoded); } 1; } That's it. The task was pretty simple because the C<"quoted-printable"> encoding can easily be converted line-by-line... as can even C<"7bit"> and C<"8bit"> (since all these encodings guarantee short lines, with a max of 1000 characters). The good news is: it is very likely that it will be similarly-easy to write a MIME::Decoder for any future standard encodings. The C<"binary"> decoder, however, really required block reads and writes: see L<"MIME::Decoder::Binary"> for details. =head1 AUTHOR Eryq (F), ZeeGee Software Inc (F). All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. =head1 VERSION $Revision: 1.1 $ $Date: 2004/04/09 17:04:46 $ =cut 1;