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vlc_towc(): unroll multibyte sequence decoding, fix overlong detection

This commit is contained in:
Rémi Denis-Courmont 2011-04-30 16:40:05 +03:00
parent 8a1afb86f7
commit 31d1aa76f9
1 changed files with 44 additions and 29 deletions
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73
src/text/unicode.c
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@ -225,59 +225,74 @@ int utf8_fprintf( FILE *stream, const char *fmt, ... )
*/
size_t vlc_towc (const char *str, uint32_t *restrict pwc)
{
uint8_t *ptr = (uint8_t *)str;
uint8_t *ptr = (uint8_t *)str, c;
uint32_t cp;
assert (str != NULL);
uint8_t c = ptr[0];
if (unlikely(c == '\0'))
{
*pwc = 0;
return 0;
}
c = *ptr;
if (unlikely(c > 0xF4))
return -1;
int charlen = clz8 (c ^ 0xFF);
switch (charlen)
{
case 0: // 7-bit ASCII character -> OK
case 0: // 7-bit ASCII character -> short cut
*pwc = c;
return 1;
return c != '\0';
case 1: // continuation byte -> error
return -1;
case 2:
if (unlikely(c < 0xC2)) // ASCII overlong
return -1;
cp = (c & 0x1F) << 6;
break;
case 3:
cp = (c & 0x0F) << 12;
break;
case 4:
cp = (c & 0x07) << 16;
break;
default:
assert (0);
}
assert (charlen >= 2 && charlen <= 4);
uint32_t cp = c & ~((0xff >> (7 - charlen)) << (7 - charlen));
for (int i = 1; i < charlen; i++)
{
assert (cp < (1 << 26));
c = ptr[i];
if (unlikely((c >> 6) != 2)) // not a continuation byte
return -1;
cp = (cp << 6) | (ptr[i] & 0x3f);
}
/* Unrolled continuation bytes decoding */
switch (charlen)
{
case 4:
if (unlikely(cp > 0x10FFFF)) // beyond Unicode
c = *++ptr;
if (unlikely((c >> 6) != 2)) // not a continuation byte
return -1;
cp |= (c & 0x3f) << 12;
if (unlikely(cp >= 0x110000)) // beyond Unicode range
return -1;
/* fall through */
case 3:
c = *++ptr;
if (unlikely((c >> 6) != 2)) // not a continuation byte
return -1;
cp |= (c & 0x3f) << 6;
if (unlikely(cp >= 0xD800 && cp < 0xC000)) // UTF-16 surrogate
return -1;
if (unlikely(cp < (1u << (5 * charlen - 4)))) // non-ASCII overlong
return -1;
/* fall through */
case 2:
if (unlikely(cp < 128)) // ASCII overlong
return -1;
if (unlikely(cp < (1u << (5 * charlen - 3)))) // overlong
c = *++ptr;
if (unlikely((c >> 6) != 2)) // not a continuation byte
return -1;
cp |= (c & 0x3f);
break;
}
*pwc = cp;
return charlen;
}