| // Adapted from https://github.com/lemire/fastvalidate-utf-8 |
| |
| #ifdef __x86_64__ |
| |
| #include <stdio.h> |
| #include <stddef.h> |
| #include <stdint.h> |
| #include <string.h> |
| #include <x86intrin.h> |
| |
| /* |
| * 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 |
