NAME¶
quoted-printable - Encoding "quoted-printable"
SYNOPSIS¶
package require
Tcl ?8.2?
package require
Trf ?2.1.3?
quoted-printable ?
options...? ?
data?
DESCRIPTION¶
The command
quoted-printable is one of several data encodings provided by
the package
trf. See
trf-intro for an overview of the whole
package.
Printable ASCII characters are largely untouched. Otherwise a three-character
encoding sequence is used. This is MIME's compromise encoding. See RFC 2045 (
http://www.rfc-editor.org/rfc/rfc2045.txt) for its definition.
- quoted-printable ?options...?
?data?
- -mode encode|decode
- This option has to be present and is always understood by
the encoding.
For immediate mode the argument value specifies the operation to use.
For an attached encoding it specifies the operation to use for
writing. Reading will automatically use the reverse operation. See
section IMMEDIATE versus ATTACHED for explanations of these two
terms.
Beyond the argument values listed above all unique abbreviations are
recognized too.
Encode converts from arbitrary (most likely binary) data into the
described representation, decode does the reverse .
- -attach channel
- The presence/absence of this option determines the main
operation mode of the transformation.
If present the transformation will be stacked onto the channel whose
handle was given to the option and run in attached mode. More about
this in section IMMEDIATE versus ATTACHED.
If the option is absent the transformation is used in immediate mode
and the options listed below are recognized. More about this in section
IMMEDIATE versus ATTACHED.
- -in channel
- This options is legal if and only if the transformation is
used in immediate mode. It provides the handle of the channel the
data to transform has to be read from.
If the transformation is in immediate mode and this option is absent
the data to transform is expected as the last argument to the
transformation.
- -out channel
- This options is legal if and only if the transformation is
used in immediate mode. It provides the handle of the channel the
generated transformation result is written to.
If the transformation is in immediate mode and this option is absent
the generated data is returned as the result of the command itself.
The transformation distinguishes between two main ways of using it. These are
the
immediate and
attached operation modes.
For the
attached mode the option
-attach is used to associate the
transformation with an existing channel. During the execution of the command
no transformation is performed, instead the channel is changed in such a way,
that from then on all data written to or read from it passes through the
transformation and is modified by it according to the definition above. This
attachment can be revoked by executing the command
unstack for the
chosen channel. This is the only way to do this at the Tcl level.
In the second mode, which can be detected by the absence of option
-attach, the transformation immediately takes data from either its
commandline or a channel, transforms it, and returns the result either as
result of the command, or writes it into a channel. The mode is named after
the immediate nature of its execution.
Where the data is taken from, and delivered to, is governed by the presence and
absence of the options
-in and
-out. It should be noted that
this ability to immediately read from and/or write to a channel is an historic
artifact which was introduced at the beginning of Trf's life when Tcl version
7.6 was current as this and earlier versions have trouble to deal with \0
characters embedded into either input or output.
SEE ALSO¶
ascii85, base64, bin, hex, oct, otp_words, quoted-printable, trf-intro, uuencode
KEYWORDS¶
encoding, mime, quoted-printable, rfc 2045
COPYRIGHT¶
Copyright (c) 1996-2003, Andreas Kupries <andreas_kupries@users.sourceforge.net>
