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isutf8: implement RFC 3629

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reject surrogate pairs (U+D800 to U+DFFF)
reject greater than U+10FFFF
This commit is contained in:
wingdeans 2023-12-28 15:41:29 -05:00
parent 8a8fc9a65f
commit a39caefc8b
1 changed files with 15 additions and 3 deletions
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18
libc/str/isutf8.c
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@ -27,8 +27,8 @@ static const char kUtf8Dispatch[] = {
1, 1, 1, 1, 1, 1, 1, 1, // 0320
1, 1, 1, 1, 1, 1, 1, 1, // 0330
2, 3, 3, 3, 3, 3, 3, 3, // 0340 utf8-3
3, 3, 3, 3, 3, 3, 3, 3, // 0350
4, 5, 5, 5, 5, 0, 0, 0, // 0360 utf8-4
3, 3, 3, 3, 3, 4, 3, 3, // 0350
5, 6, 6, 6, 7, 0, 0, 0, // 0360 utf8-4
0, 0, 0, 0, 0, 0, 0, 0, // 0370
};
@ -93,6 +93,7 @@ bool32 isutf8(const void *data, size_t size) {
return false; // overlong
}
// fallthrough
case 3:
case3:
if (p + 2 <= e && //
(p[0] & 0300) == 0200 && //
@ -103,11 +104,17 @@ bool32 isutf8(const void *data, size_t size) {
return false; // missing cont
}
case 4:
if (p < e && (*p & 040)) {
return false; // utf-16 surrogate
}
goto case3;
case 5:
if (p < e && (*p & 0377) < 0220) {
return false; // overlong
}
// fallthrough
case 5:
case 6:
case6:
if (p + 3 <= e && //
(((uint32_t)(p[+2] & 0377) << 030 | //
(uint32_t)(p[+1] & 0377) << 020 | //
@ -119,6 +126,11 @@ bool32 isutf8(const void *data, size_t size) {
} else {
return false; // missing cont
}
case 7:
if (p < e && (*p & 0x3F) > 0xF) {
return false; // over limit
}
goto case6;
default:
__builtin_unreachable();
}