On 02/17/2011 07:25 AM, Avi Kivity wrote:
On 02/17/2011 03:10 PM, Anthony Liguori wrote:
On 02/17/2011 06:23 AM, Avi Kivity wrote:
On 02/17/2011 02:12 PM, Anthony Liguori wrote:
(btw what happens in a non-UTF-8 locale? I guess we should just
reject unencodable strings).
While QEMU is mostly ASCII internally, for the purposes of the JSON
parser, we always encode and decode UTF-8. We reject invalid UTF-8
sequences. But since JSON is string-encoded unicode, we can always
decode a JSON string to valid UTF-8 as long as the string is well
formed.
That is wrong. If the user passes a Unicode filename it is expected
to be translated to the current locale encoding for the purpose of,
say, filename lookup.
QEMU does not support anything but UTF-8.
Since when?
AFAICT, JSON string conversion is the only place where there is any
dependency on UTF-8. Anything else should just work.
That's pretty common with Unix software. I don't think any modern
Unix platform actually uses UCS2 or UTF-16. It's either ascii or UTF-8.
Most/all Linux distributions support UTF-8 as well as a zillion other
encodings (single-byte ASCII + another charset, or multi-byte charsets
for languages with many characters.
Maybe there's some confusion here. UTF-8 is an encoding, not a locale.
The common encodings are ASCII, UTF-8, UCS2, UTF-16, and UTF-32.
An application has to explicitly support an encoding. It is not
transparent. UCS2/UTF-16 means that strings are not 'const char *'s but
'const wchar_t *' where typedef unsigned short wchar_t;.
QEMU assumes, in lots of places that strings are single-byte NUL
terminated. Basically, any use of snprintf, printf, strcpy, strlen,
etc. pretty much tie you to ASCII/UTF-8. You can have a single NUL byte
as part of a valid UCS2 string.
The only place it even matters is Windows and Windows has ASCII and
UTF-16 versions of their APIs. So on Windows, non-ASCII characters
won't be handled correctly (yet another one of the many issues with
Windows support in QEMU). UTF-8 is self-recovering though so it
degrades gracefully.
It matters on Linux with el_GR.iso88597, for example.
The whole series of iso8859 (8-bit encodings) are officially abandoned
in favor of UCS and encodings that support the full UCS code page
(UTF-8/UTF-16).
I see no strong reason to try and support deprecated encodings when
there are perfectly valid replacements like el_GR.utf8.
Regards,
Anthony Liguori
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