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(Coding System Basics): Clarify previous change.

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Richard M. Stallman 2005-04-01 22:08:47 +00:00
parent 1ee49a88dd
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2 changed files with 16 additions and 13 deletions
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@ -1,3 +1,7 @@
2005-04-01 Richard M. Stallman <rms@gnu.org>
* nonascii.texi (Coding System Basics): Clarify previous change.
2005-04-01 Kenichi Handa <handa@m17n.org>
* nonascii.texi (Coding System Basics): Describe about rondtrip

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lispref/nonascii.texi
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@ -628,11 +628,11 @@ characters; for example, there are three coding systems for the Cyrillic
conversion, but some of them leave the choice unspecified---to be chosen
heuristically for each file, based on the data.
In general, a coding system doesn't guarantee a roundtrip identity,
i.e. decoding followed by encoding in the same coding system can
result in the different byte sequence. But there are several coding
systems that go guarantee that the result will be the same as what you
originally decoded. They are:
In general, a coding system doesn't guarantee roundtrip identity:
decoding text then encoding the result in the same coding system can
produce a different byte sequence from the one you originally decoded.
However, the following coding systems do guarantee that the result
will be the same as what you originally decoded:
@quotation
chinese-big5 chinese-iso-8bit cyrillic-iso-8bit emacs-mule
@ -641,14 +641,13 @@ iso-latin-4 iso-latin-5 iso-latin-8 iso-latin-9 iso-safe
japanese-iso-8bit japanese-shift-jis korean-iso-8bit raw-text
@end quotation
Likewise, a coding systme doesn't guarantee the other way of roundtrip
identity, i.e. encoding buffer text into a coding system followed by
decoding again with the same coding system will produce the different
buffer text. For instance, when you encode Latin-2 characters by
@code{utf-8} and decode it back by the same coding system, you'll get
Unicode charactes (of charset @code{mule-unicode-0100-24ff}), and when
you encode Unicode characters by @code{iso-latin-2} and decode it back
by the same coding system, you'll get Latin-2 characters.
Encoding buffer text and then decoding the result can also fail to
reproduce the original text. For instance, when you encode Latin-2
characters with @code{utf-8} and decode the result using the same
coding system, you'll get Unicode characters (of charset
@code{mule-unicode-0100-24ff}). When you encode Unicode characters
with @code{iso-latin-2} and decode them back with the same coding
system, you'll get Latin-2 characters.
@cindex end of line conversion
@dfn{End of line conversion} handles three different conventions used