Fixed bug #896 SDL-1.2
authorSam Lantinga <slouken@libsdl.org>
Fri, 11 Dec 2009 08:00:57 +0000
branchSDL-1.2
changeset 4388 1524d3237820
parent 4387 72d3b4fd918b
child 4389 c6c3a6e7db46
Fixed bug #896

John Popplewell 2009-12-08 23:05:50 PST

Originally reported by AKFoerster on the mailing list.

Error decoding UTF8 Russian text to UTF-16LE on Windows, but specifically on
platforms without iconv support (the default on Windows).

Valid UTF8 characters are flagged as being overlong and then substituted by the
UNKNOWN_UNICODE character.

After studying the testiconv.c example program, reading the RFCs and putting
some printf statements in SDL_iconv.c the problem is in a test for 'Maximum
overlong sequences', specifically 4.2.1, which is carried out by the following
code:

} else if ( p[0] >= 0xC0 ) {
if ( (p[0] & 0xE0) != 0xC0 ) {
/* Skip illegal sequences
return SDL_ICONV_EILSEQ;
*/
ch = UNKNOWN_UNICODE;
} else {
if ( (p[0] & 0xCE) == 0xC0 ) { <<<<<<<< here
overlong = SDL_TRUE;
}
ch = (Uint32)(p[0] & 0x1F);
left = 1;
}
} else {

Here is the 2-byte encoding of a character in range 00000080 - 000007FF
110xxxxx 10xxxxxx

The line in question is supposed to be checking for an overlong sequence which
would be less than
11000001 10111111

which should be represented as a single byte.

BUT, the mask value (0xCE) is wrong, it isn't checking the top-most bit:
11000001 value
11001110 mask (incorrect)
^
and should be (0xDE):
11000001 value
11011110 mask (correct)

making the above code:

} else if ( p[0] >= 0xC0 ) {
if ( (p[0] & 0xE0) != 0xC0 ) {
/* Skip illegal sequences
return SDL_ICONV_EILSEQ;
*/
ch = UNKNOWN_UNICODE;
} else {
if ( (p[0] & 0xDE) == 0xC0 ) { <<<<<<<< here
overlong = SDL_TRUE;
}
ch = (Uint32)(p[0] & 0x1F);
left = 1;
}
} else {

I can supply a test program and/or a patch if required,

best regards,
John Popplewell
src/stdlib/SDL_iconv.c
--- a/src/stdlib/SDL_iconv.c	Thu Dec 03 04:20:46 2009 +0000
+++ b/src/stdlib/SDL_iconv.c	Fri Dec 11 08:00:57 2009 +0000
@@ -383,7 +383,7 @@
 						*/
 						ch = UNKNOWN_UNICODE;
 					} else {
-						if ( (p[0] & 0xCE) == 0xC0 ) {
+						if ( (p[0] & 0xDE) == 0xC0 ) {
 							overlong = SDL_TRUE;
 						}
 						ch = (Uint32)(p[0] & 0x1F);