MIME::Decoder man page on SuSE

Man page or keyword search:  
man Server   14857 pages
apropos Keyword Search (all sections)
Output format
SuSE logo
[printable version]

MIME::Decoder(3)      User Contributed Perl Documentation     MIME::Decoder(3)

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;

perl v5.10.0			  2008-06-30		      MIME::Decoder(3)
[top]

List of man pages available for SuSE

Copyright (c) for man pages and the logo by the respective OS vendor.

For those who want to learn more, the polarhome community provides shell access and support.

[legal] [privacy] [GNU] [policy] [cookies] [netiquette] [sponsors] [FAQ]
Tweet
Polarhome, production since 1999.
Member of Polarhome portal.
Based on Fawad Halim's script.
....................................................................
Vote for polarhome
Free Shell Accounts :: the biggest list on the net