Provided by: libmime-tools-perl_5.509-1_all bug

NAME

       MIME::Decoder - an object for decoding the body part of a MIME stream

SYNOPSIS

       Before reading further, you should see MIME::Tools 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...

   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);

   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);

   Non-standard encodings
       You can write and install your own decoders so that MIME::Decoder will know about them:

           use MyBase64Decoder;

           install MyBase64Decoder 'base64';

       You can also test if a given encoding is supported:

           if (supported MIME::Decoder 'x-uuencode') {
               ### we can uuencode!
           }

DESCRIPTION

       This abstract class, and its private concrete subclasses (see below) provide an OO front
       end to the actions of...

       •   Decoding a MIME-encoded stream

       •   Encoding a raw data stream into a MIME-encoded stream.

       The constructor for MIME::Decoder takes the name of an encoding ("base64", "7bit", etc.),
       and returns an instance of a subclass of MIME::Decoder whose "decode()" method will
       perform the appropriate decoding action, and whose "encode()" method will perform the
       appropriate encoding action.

PUBLIC INTERFACE

   Standard interface
       If all you are doing is using this class, here's all you'll need...

       new ENCODING
           Class method, constructor.  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.

       best ENCODING
           Class method, constructor.  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.

       decode INSTREAM,OUTSTREAM
           Instance method.  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.

       encode INSTREAM,OUTSTREAM
           Instance method.  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.

       encoding
           Instance method.  Return the encoding that this object was created to handle, coerced
           to all lowercase (e.g., "base64").

       head [HEAD]
           Instance method.  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');

       supported [ENCODING]
           Class method.  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 not change the way the module
           performs its lookups.  Only "install" can do that.

           Thanks to Achim Bohnet for suggesting this method.

   Subclass interface
       If you are writing (or installing) a new decoder subclass, there are some other methods
       you'll need to know about:

       decode_it INSTREAM,OUTSTREAM
           Abstract instance method.  The back-end of the decode 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 "getline()" or "read()",
           decode this input, and print the decoded data to the output handle via "print()".  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 "decode()", so you don't need to worry about it.

           Your method must return either "undef" (to indicate failure), or 1 (to indicate
           success).  It may also throw an exception to indicate failure.

       encode_it INSTREAM,OUTSTREAM
           Abstract instance method.  The back-end of the encode 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 "getline()" or "read()",
           encode this input, and print the encoded data to the output handle via "print()".  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 "encode()", so you don't need to worry about it.

           Your method must return either "undef" (to indicate failure), or 1 (to indicate
           success).  It may also throw an exception to indicate failure.

       filter IN, OUT, COMMAND...
           Class method, utility.  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.

       init ARGS...
           Instance method.  Do any necessary initialization of the new instance, taking whatever
           arguments were given to "new()".  Should return the self object on success, undef on
           failure.

       install ENCODINGS...
           Class method.  Install this class so that each encoding in ENCODINGS is handled by it:

               install MyBase64Decoder 'base64', 'x-base64super';

           You should not override this method.

       uninstall ENCODINGS...
           Class method.  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.

DECODER SUBCLASSES

       You don't need to "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!

NOTES

   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)

       Thanks to Achim Bohnet for suggesting this more-generic I/O model.

   Writing a decoder
       If you're experimenting with your own encodings, you'll probably want to write a decoder.
       Here are the basics:

       1.  Create a module, like "MyDecoder::", for your decoder.  Declare it to be a subclass of
           MIME::Decoder.

       2.  Create the following instance methods in your class, as described above:

               decode_it
               encode_it
               init

       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"

       To illustrate, here's a custom decoder class for the "quoted-printable" 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) = @_;
               local $_;
               while (defined($_ = $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 "quoted-printable" encoding can easily
       be converted line-by-line... as can even "7bit" and "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 "binary" decoder, however, really required block reads and writes: see
       "MIME::Decoder::Binary" for details.

SEE ALSO

       MIME::Tools, other MIME::Decoder subclasses.

AUTHOR

       Eryq (eryq@zeegee.com), ZeeGee Software Inc (http://www.zeegee.com).

       All rights reserved.  This program is free software; you can redistribute it and/or modify
       it under the same terms as Perl itself.

       1;