*/
size_t vlc_towc (const char *str, uint32_t *restrict pwc)
{
- uint8_t *ptr = (uint8_t *)str;
- assert (str != NULL);
-
- uint8_t c = ptr[0];
+ uint8_t *ptr = (uint8_t *)str, c;
+ uint32_t cp;
- if (unlikely(c == '\0'))
- {
- *pwc = 0;
- return 0;
- }
+ assert (str != NULL);
+ 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;
- }
- assert (charlen >= 2 && charlen <= 4);
+ case 2:
+ if (unlikely(c < 0xC2)) // ASCII overlong
+ return -1;
+ cp = (c & 0x1F) << 6;
+ break;
- uint32_t cp = c & ~((0xff >> (7 - charlen)) << (7 - charlen));
- for (int i = 1; i < charlen; i++)
- {
- assert (cp < (1 << 26));
- c = ptr[i];
+ case 3:
+ cp = (c & 0x0F) << 12;
+ break;
- if (unlikely((c >> 6) != 2)) // not a continuation byte
- return -1;
+ case 4:
+ cp = (c & 0x07) << 16;
+ break;
- cp = (cp << 6) | (ptr[i] & 0x3f);
+ default:
+ assert (0);
}
+ /* 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;
- case 2:
- if (unlikely(cp < 128)) // ASCII overlong
+ if (unlikely(cp < (1u << (5 * charlen - 4)))) // non-ASCII overlong
return -1;
- if (unlikely(cp < (1u << (5 * charlen - 3)))) // overlong
+ /* fall through */
+ case 2:
+ c = *++ptr;
+ if (unlikely((c >> 6) != 2)) // not a continuation byte
return -1;
+ cp |= (c & 0x3f);
+ break;
}
+
*pwc = cp;
return charlen;
}