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.IX Title "MIME::Decoder::NBit 3pm"
.TH MIME::Decoder::NBit 3pm 2024-02-09 "perl v5.38.2" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH NAME
MIME::Decoder::NBit \- encode/decode a "7bit" or "8bit" stream
.SH SYNOPSIS
.IX Header "SYNOPSIS"
A generic decoder object; see MIME::Decoder for usage.
.SH DESCRIPTION
.IX Header "DESCRIPTION"
This is a MIME::Decoder subclass for the \f(CW\*(C`7bit\*(C'\fR and \f(CW\*(C`8bit\*(C'\fR content
transfer encodings.  These are not "encodings" per se: rather, they
are simply assertions of the content of the message.
From RFC\-2045 Section 6.2.:
.PP
.Vb 3
\&   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.
.Ve
.PP
In keeping with this: as of MIME-tools 4.x, 
\&\fIthis class does no modification of its input when encoding;\fR 
all it does is attempt to \fIdetect violations\fR of the 7bit/8bit assertion, 
and issue a warning (one per message) if any are found.
.SS "Legal 7bit data"
.IX Subsection "Legal 7bit data"
RFC\-2045 Section 2.7 defines legal \f(CW\*(C`7bit\*(C'\fR data:
.PP
.Vb 6
\&   "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.
.Ve
.SS "Legal 8bit data"
.IX Subsection "Legal 8bit data"
RFC\-2045 Section 2.8 defines legal \f(CW\*(C`8bit\*(C'\fR data:
.PP
.Vb 5
\&   "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.
.Ve
.SS "How decoding is done"
.IX Subsection "How decoding is done"
The \fBdecoder\fR does a line-by-line pass-through from input to output,
leaving the data unchanged \fIexcept\fR that an end-of-line sequence of
CRLF is converted to a newline "\en".  Given the line-oriented nature
of 7bit and 8bit, this seems relatively sensible.
.SS "How encoding is done"
.IX Subsection "How encoding is done"
The \fBencoder\fR does a line-by-line pass-through from input to output,
and simply attempts to \fIdetect\fR violations of the \f(CW\*(C`7bit\*(C'\fR/\f(CW\*(C`8bit\*(C'\fR
domain.  The default action is to warn once per encoding if violations
are detected; the warnings may be silenced with the QUIET configuration
of MIME::Tools.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
MIME::Decoder
.SH AUTHOR
.IX Header "AUTHOR"
Eryq (\fIeryq@zeegee.com\fR), ZeeGee Software Inc (\fIhttp://www.zeegee.com\fR).
.PP
All rights reserved.  This program is free software; you can redistribute 
it and/or modify it under the same terms as Perl itself.