Re: If invalid string should crash(was:string need to be robust)
%u Wrote: I agree with a), but not b), Can't find anything in unicode standard says you can use the low surrogate like that According to: http://www.cl.cam.ac.uk/~mgk25/ According to ISO 10646-1:2000, sections D.7 and 2.3c, a device receiving UTF-8 shall interpret a malformed sequence in the same way that it interprets a character that is outside the adopted subset and characters that are not within the adopted subset shall be indicated to the user by a receiving device. A quite commonly used approach in UTF-8 decoders is to replace any malformed UTF-8 sequence by a replacement character (U+FFFD), which looks a bit like an inverted question mark, or a similar symbol. Refer to this file for the above quote: http://www.cl.cam.ac.uk/~mgk25/ucs/examples/UTF-8-test.txt
Re: If invalid string should crash(was:string need to be robust)
Thank you Jussi, But still this is not part of the standard, U+FFFD is a commonly used approach, while the U+DC80..U+DCFF is also a common solution for that(http://en.wikipedia.org/wiki/Utf8#Invalid_byte_sequences), different approach solve different problems. I think the current problem in D is that std.utf module is ill defined, it's not designed to make developer's life easier. It just make the developers to ignore the case that utf8 string can be invalid. --ZY Zhou == Quote from Jussi Jumppanen (jus...@zeusedit.com)'s article %u Wrote: I agree with a), but not b), Can't find anything in unicode standard says you can use the low surrogate like that According to: http://www.cl.cam.ac.uk/~mgk25/ According to ISO 10646-1:2000, sections D.7 and 2.3c, a device receiving UTF-8 shall interpret a malformed sequence in the same way that it interprets a character that is outside the adopted subset and characters that are not within the adopted subset shall be indicated to the user by a receiving device. A quite commonly used approach in UTF-8 decoders is to replace any malformed UTF-8 sequence by a replacement character (U+FFFD), which looks a bit like an inverted question mark, or a similar symbol. Refer to this file for the above quote: http://www.cl.cam.ac.uk/~mgk25/ucs/examples/UTF-8-test.txt
Re: If invalid string should crash(was:string need to be robust)
On 03/14/2011 07:55 AM, ZY Zhou wrote: Thank you Jussi, But still this is not part of the standard, U+FFFD is a commonly used approach, while the U+DC80..U+DCFF is also a common solution for that(http://en.wikipedia.org/wiki/Utf8#Invalid_byte_sequences), different approach solve different problems. I am surprised of some of your very affirmative statements (all along the thread). None of the string processing libs I have met use the approach you propose here, which is replacing invalid input by other invalid data (surrogate values). On the other hand, the replacement character (0xFFFD) evoked by Jussi (which I also proposed in a previous post) is a valid Unicode code point; same for free user-avalable areas. I think the current problem in D is that std.utf module is ill defined, it's not designed to make developer's life easier. It just make the developers to ignore the case that utf8 string can be invalid. On the contrary, D perfectly deals with invalid input by signalling it to you programmer. It is not ignored, which would be the worse approach. What to do with invalid input belongs to your application's logic (as pointed by Jonathan); you are demanding D standard libs to do your job at your place, exactly the way you want it, using an incorrect approach. Denis --ZY Zhou == Quote from Jussi Jumppanen (jus...@zeusedit.com)'s article %u Wrote: I agree with a), but not b), Can't find anything in unicode standard says you can use the low surrogate like that According to: http://www.cl.cam.ac.uk/~mgk25/ According to ISO 10646-1:2000, sections D.7 and 2.3c, a device receiving UTF-8 shall interpret a malformed sequence in the same way that it interprets a character that is outside the adopted subset and characters that are not within the adopted subset shall be indicated to the user by a receiving device. A quite commonly used approach in UTF-8 decoders is to replace any malformed UTF-8 sequence by a replacement character (U+FFFD), which looks a bit like an inverted question mark, or a similar symbol. Refer to this file for the above quote: http://www.cl.cam.ac.uk/~mgk25/ucs/examples/UTF-8-test.txt -- _ vita es estrany spir.wikidot.com
Re: If invalid string should crash(was:string need to be robust)
Jussi Jumppanen Wrote: %u Wrote: I agree with a), but not b), Can't find anything in unicode standard says you can use the low surrogate like that According to: http://www.cl.cam.ac.uk/~mgk25/ According to ISO 10646-1:2000, sections D.7 and 2.3c, a device receiving UTF-8 shall interpret a malformed sequence in the same way that it interprets a character that is outside the adopted subset and characters that are not within the adopted subset shall be indicated to the user by a receiving device. A quite commonly used approach in UTF-8 decoders is to replace any malformed UTF-8 sequence by a replacement character (U+FFFD), which looks a bit like an inverted question mark, or a similar symbol. Refer to this file for the above quote: http://www.cl.cam.ac.uk/~mgk25/ucs/examples/UTF-8-test.txt Sounds like a text rendering guideline rather than a text processing guideline.
Re: If invalid string should crash(was:string need to be robust)
ZY Zhou rin...@gmail.com wrote:
But for the following case, it is complete wrong if it crash at line 3:
Why? That is the point where you are actually saying 'I care about
individual characters in this string'.
1: char[] c = [0xA0];
2: string s = c.idup;
3: foreach(dchar d; s){}
The expected result is either:
a) crash at line 2, c is not valid utf
and can't be converted to string
A char[] is just as bound by the rules as is string (which is simply
immutable(char)[]). Thus the program should feel free to expect it
to contain valid utf-8 data. Validating each string upon every single
copy operation is unacceptable overhead.
or:
b) don't crash, and d = 0xDCA0;
b is unacceptable in the general case. It may be good for your specific
situation, but in general, it is simply ignoring an error.
--
Simen
If invalid string should crash(was:string need to be robust)
Hi,
invalid utf8 code always break my program, so I suggest if invalid code in
utf8 need to be converted to dchar, use the low surrogate code
points(DC80~DCFF) instead of crashing the program. But many people here don't
like this idea, you think exception is the right thing. OK, let me ask you a
question:
Do you always try/catch for invalid utf when reading a file?
I believe you don't, you simply don't care.
While the text file is invalid, this use case itself is valid. Should a
browser crash on a web page with charset=utf8 but has invalid utf8 code in it?
Exception doesn't help either, using them in this case is almost like writing
a utf8 decoder yourself.
Anyway, since I'm already using my own utf decoder, I don't care if you agree
with me or not.
But for the following case, it is complete wrong if it crash at line 3:
1: char[] c = [0xA0];
2: string s = c.idup;
3: foreach(dchar d; s){}
The expected result is either:
a) crash at line 2, c is not valid utf
and can't be converted to string
or:
b) don't crash, and d = 0xDCA0;
--ZY Zhou
Re: If invalid string should crash(was:string need to be robust)
But for the following case, it is complete wrong if it crash at line 3:
1: char[] c = [0xA0];
2: string s = c.idup;
3: foreach(dchar d; s){}
The expected result is either:
a) crash at line 2, c is not valid utf and can't be converted to string
or:
b) don't crash, and d = 0xDCA0;
I agree with a), but not b), Can't find anything in unicode standard says you
can
use the low surrogate like that
