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lib::MIME::Decoder::NBit

Section: User Contributed Perl Documentation (3)
Updated: perl 5.004, patch 04
Index

NAME

MIME::Decoder::NBit - encode/decode a ``7bit'' or ``8bit'' stream

SYNOPSIS

A generic decoder object; see the MIME::Decoder manpage for usage.

DESCRIPTION

This is a MIME::Decoder subclass for the 7bit and 8bit contenttransfer encodings. These are not ``encodings'' per se: rather, theyare simply assertions of the content of the message.From RFC-2045 Section 6.2.:

   Three transformations are currently defined: identity, the "quoted-   printable" encoding, and the "base64" encoding.  The domains are   "binary", "8bit" and "7bit".

   The Content-Transfer-Encoding values "7bit", "8bit", and "binary" all   mean that the identity (i.e. NO) encoding transformation has been   performed.  As such, they serve simply as indicators of the domain of   the body data, and provide useful information about the sort of   encoding that might be needed for transmission in a given transport   system.

In keeping with this: as of MIME-tools 4.x, this class does no modification of its input when encoding; all it does is attempt to detect violations of the 7bit/8bit assertion, and issue a warning (one per message) if any are found.

Legal 7bit data

RFC-2045 Section 2.7 defines legal 7bit data:

   "7bit data" refers to data that is all represented as relatively   short lines with 998 octets or less between CRLF line separation   sequences [RFC-821].  No octets with decimal values greater than 127   are allowed and neither are NULs (octets with decimal value 0).  CR   (decimal value 13) and LF (decimal value 10) octets only occur as   part of CRLF line separation sequences.

Legal 8bit data

RFC-2045 Section 2.8 defines legal 8bit data:

   "8bit data" refers to data that is all represented as relatively   short lines with 998 octets or less between CRLF line separation   sequences [RFC-821]), but octets with decimal values greater than 127   may be used.  As with "7bit data" CR and LF octets only occur as part   of CRLF line separation sequences and no NULs are allowed.

How decoding is done

The decoder does a line-by-line pass-through from input to output,leaving the data unchanged except that an end-of-line sequence ofCRLF is converted to a newline ``\n''. Given the line-oriented natureof 7bit and 8bit, this seems relatively sensible.

How encoding is done

The encoder does a line-by-line pass-through from input to output,and simply attempts to detect violations of the 7bit/8bitdomain. The default action is to warn once per encoding if violationsare detected; the warnings may be silenced with the QUIET configurationof the MIME::ToolUtils manpage.

Note: this is a major departure from MIME-tools 3.x, which usedto split long lines are perform 8-to-7 mappings for you. But so longas you weren't dependent on these features, things should still workfor you. If you were counting on this automatic fixup, you should switch your encoding to quoted-printable.

AUTHOR

VERSION

$Revision: 4.103 $ $Date: 1998/01/10 04:24:45 $

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