// Adapted from https://github.com/lemire/fastvalidate-utf-8 #ifdef __x86_64__ #include #include #include #include #include /* * legal utf-8 byte sequence * http://www.unicode.org/versions/Unicode6.0.0/ch03.pdf - page 94 * * Code Points 1st 2s 3s 4s * U+0000..U+007F 00..7F * U+0080..U+07FF C2..DF 80..BF * U+0800..U+0FFF E0 A0..BF 80..BF * U+1000..U+CFFF E1..EC 80..BF 80..BF * U+D000..U+D7FF ED 80..9F 80..BF * U+E000..U+FFFF EE..EF 80..BF 80..BF * U+10000..U+3FFFF F0 90..BF 80..BF 80..BF * U+40000..U+FFFFF F1..F3 80..BF 80..BF 80..BF * U+100000..U+10FFFF F4 80..8F 80..BF 80..BF * */ #if 0 static void print128(const char *s, const __m128i *v128) { const unsigned char *v8 = (const unsigned char *)v128; if (s) printf("%s: ", s); for (int i = 0; i < 16; i++) printf("%02x ", v8[i]); printf("\n"); } #endif // all byte values must be no larger than 0xF4 static inline void checkSmallerThan0xF4(__m128i current_bytes, __m128i *has_error) { // unsigned, saturates to 0 below max *has_error = _mm_or_si128(*has_error, _mm_subs_epu8(current_bytes, _mm_set1_epi8(0xF4))); } static inline __m128i continuationLengths(__m128i high_nibbles) { return _mm_shuffle_epi8( _mm_setr_epi8(1, 1, 1, 1, 1, 1, 1, 1, // 0xxx (ASCII) 0, 0, 0, 0, // 10xx (continuation) 2, 2, // 110x 3, // 1110 4), // 1111, next should be 0 (not checked here) high_nibbles); } static inline __m128i carryContinuations(__m128i initial_lengths, __m128i previous_carries) { __m128i right1 = _mm_subs_epu8(_mm_alignr_epi8(initial_lengths, previous_carries, 16 - 1), _mm_set1_epi8(1)); __m128i sum = _mm_add_epi8(initial_lengths, right1); __m128i right2 = _mm_subs_epu8(_mm_alignr_epi8(sum, previous_carries, 16 - 2), _mm_set1_epi8(2)); return _mm_add_epi8(sum, right2); } static inline void checkContinuations(__m128i initial_lengths, __m128i carries, __m128i *has_error) { // overlap || underlap // carry > length && length > 0 || !(carry > length) && !(length > 0) // (carries > length) == (lengths > 0) __m128i overunder = _mm_cmpeq_epi8(_mm_cmpgt_epi8(carries, initial_lengths), _mm_cmpgt_epi8(initial_lengths, _mm_setzero_si128())); *has_error = _mm_or_si128(*has_error, overunder); } // when 0xED is found, next byte must be no larger than 0x9F // when 0xF4 is found, next byte must be no larger than 0x8F // next byte must be continuation, ie sign bit is set, so signed < is ok static inline void checkFirstContinuationMax(__m128i current_bytes, __m128i off1_current_bytes, __m128i *has_error) { __m128i maskED = _mm_cmpeq_epi8(off1_current_bytes, _mm_set1_epi8(0xED)); __m128i maskF4 = _mm_cmpeq_epi8(off1_current_bytes, _mm_set1_epi8(0xF4)); __m128i badfollowED = _mm_and_si128(_mm_cmpgt_epi8(current_bytes, _mm_set1_epi8(0x9F)), maskED); __m128i badfollowF4 = _mm_and_si128(_mm_cmpgt_epi8(current_bytes, _mm_set1_epi8(0x8F)), maskF4); *has_error = _mm_or_si128(*has_error, _mm_or_si128(badfollowED, badfollowF4)); } // map off1_hibits => error condition // hibits off1 cur // C => < C2 && true // E => < E1 && < A0 // F => < F1 && < 90 // else false && false static inline void checkOverlong(__m128i current_bytes, __m128i off1_current_bytes, __m128i hibits, __m128i previous_hibits, __m128i *has_error) { __m128i off1_hibits = _mm_alignr_epi8(hibits, previous_hibits, 16 - 1); __m128i initial_mins = _mm_shuffle_epi8( _mm_setr_epi8(-128, -128, -128, -128, -128, -128, -128, -128, -128, -128, -128, -128, // 10xx => false 0xC2, -128, // 110x 0xE1, // 1110 0xF1), off1_hibits); __m128i initial_under = _mm_cmpgt_epi8(initial_mins, off1_current_bytes); __m128i second_mins = _mm_shuffle_epi8( _mm_setr_epi8(-128, -128, -128, -128, -128, -128, -128, -128, -128, -128, -128, -128, // 10xx => false 127, 127, // 110x => true 0xA0, // 1110 0x90), off1_hibits); __m128i second_under = _mm_cmpgt_epi8(second_mins, current_bytes); *has_error = _mm_or_si128(*has_error, _mm_and_si128(initial_under, second_under)); } struct processed_utf_bytes { __m128i rawbytes; __m128i high_nibbles; __m128i carried_continuations; }; static inline void count_nibbles(__m128i bytes, struct processed_utf_bytes *answer) { answer->rawbytes = bytes; answer->high_nibbles = _mm_and_si128(_mm_srli_epi16(bytes, 4), _mm_set1_epi8(0x0F)); } // check whether the current bytes are valid UTF-8 // at the end of the function, previous gets updated static inline struct processed_utf_bytes checkUTF8Bytes(__m128i current_bytes, struct processed_utf_bytes *previous, __m128i *has_error) { struct processed_utf_bytes pb; count_nibbles(current_bytes, &pb); checkSmallerThan0xF4(current_bytes, has_error); __m128i initial_lengths = continuationLengths(pb.high_nibbles); pb.carried_continuations = carryContinuations(initial_lengths, previous->carried_continuations); checkContinuations(initial_lengths, pb.carried_continuations, has_error); __m128i off1_current_bytes = _mm_alignr_epi8(pb.rawbytes, previous->rawbytes, 16 - 1); checkFirstContinuationMax(current_bytes, off1_current_bytes, has_error); checkOverlong(current_bytes, off1_current_bytes, pb.high_nibbles, previous->high_nibbles, has_error); return pb; } /* Return 0 on success, -1 on error */ int utf8_lemire(const unsigned char *src, int len) { size_t i = 0; __m128i has_error = _mm_setzero_si128(); struct processed_utf_bytes previous = {.rawbytes = _mm_setzero_si128(), .high_nibbles = _mm_setzero_si128(), .carried_continuations = _mm_setzero_si128()}; if (len >= 16) { for (; i <= len - 16; i += 16) { __m128i current_bytes = _mm_loadu_si128((const __m128i *)(src + i)); previous = checkUTF8Bytes(current_bytes, &previous, &has_error); } } // last part if (i < len) { char buffer[16]; memset(buffer, 0, 16); memcpy(buffer, src + i, len - i); __m128i current_bytes = _mm_loadu_si128((const __m128i *)(buffer)); previous = checkUTF8Bytes(current_bytes, &previous, &has_error); } else { has_error = _mm_or_si128(_mm_cmpgt_epi8(previous.carried_continuations, _mm_setr_epi8(9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 1)), has_error); } return _mm_testz_si128(has_error, has_error) ? 0 : -1; } #endif