mirror of https://github.com/tstack/lnav.git
238 lines
8.0 KiB
C
238 lines
8.0 KiB
C
/**
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* https://github.com/lemire/fastvalidate-utf-8
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*/
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#ifndef SIMDUTF8CHECK_H
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#define SIMDUTF8CHECK_H
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#include <stdbool.h>
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#include <stddef.h>
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#include <stdint.h>
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#include <x86intrin.h>
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#include "base/lnav_log.hh"
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#ifdef __cplusplus
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extern "C" {
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#endif
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/*
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* legal utf-8 byte sequence
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* http://www.unicode.org/versions/Unicode6.0.0/ch03.pdf - page 94
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*
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* Code Points 1st 2s 3s 4s
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* U+0000..U+007F 00..7F
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* U+0080..U+07FF C2..DF 80..BF
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* U+0800..U+0FFF E0 A0..BF 80..BF
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* U+1000..U+CFFF E1..EC 80..BF 80..BF
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* U+D000..U+D7FF ED 80..9F 80..BF
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* U+E000..U+FFFF EE..EF 80..BF 80..BF
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* U+10000..U+3FFFF F0 90..BF 80..BF 80..BF
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* U+40000..U+FFFFF F1..F3 80..BF 80..BF 80..BF
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* U+100000..U+10FFFF F4 80..8F 80..BF 80..BF
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*
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*/
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// all byte values must be no larger than 0xF4
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static void checkSmallerThan0xF4(__m128i current_bytes,
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__m128i *has_error)
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{
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// unsigned, saturates to 0 below max
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*has_error = _mm_or_si128(*has_error,
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_mm_subs_epu8(current_bytes,
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_mm_set1_epi8(0xF4)));
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}
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static __m128i continuationLengths(__m128i high_nibbles)
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{
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return _mm_shuffle_epi8(
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_mm_setr_epi8(1, 1, 1, 1, 1, 1, 1, 1, // 0xxx (ASCII)
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0, 0, 0, 0, // 10xx (continuation)
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2, 2, // 110x
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3, // 1110
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4), // 1111, next should be 0 (not checked here)
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high_nibbles);
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}
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static __m128i carryContinuations(__m128i initial_lengths,
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__m128i previous_carries)
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{
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__m128i right1 = _mm_subs_epu8(
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_mm_alignr_epi8(initial_lengths, previous_carries, 16 - 1),
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_mm_set1_epi8(1));
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__m128i sum = _mm_add_epi8(initial_lengths, right1);
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__m128i right2 = _mm_subs_epu8(
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_mm_alignr_epi8(sum, previous_carries, 16 - 2),
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_mm_set1_epi8(2));
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return _mm_add_epi8(sum, right2);
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}
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static void checkContinuations(__m128i initial_lengths,
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__m128i carries,
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__m128i *has_error)
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{
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// overlap || underlap
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// carry > length && length > 0 || !(carry > length) && !(length > 0)
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// (carries > length) == (lengths > 0)
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__m128i overunder = _mm_cmpeq_epi8(
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_mm_cmpgt_epi8(carries, initial_lengths),
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_mm_cmpgt_epi8(initial_lengths, _mm_setzero_si128()));
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*has_error = _mm_or_si128(*has_error, overunder);
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}
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// when 0xED is found, next byte must be no larger than 0x9F
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// when 0xF4 is found, next byte must be no larger than 0x8F
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// next byte must be continuation, ie sign bit is set, so signed < is ok
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static void checkFirstContinuationMax(__m128i current_bytes,
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__m128i off1_current_bytes,
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__m128i *has_error)
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{
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__m128i maskED = _mm_cmpeq_epi8(off1_current_bytes, _mm_set1_epi8(0xED));
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__m128i maskF4 = _mm_cmpeq_epi8(off1_current_bytes, _mm_set1_epi8(0xF4));
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__m128i badfollowED = _mm_and_si128(
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_mm_cmpgt_epi8(current_bytes, _mm_set1_epi8(0x9F)),
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maskED);
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__m128i badfollowF4 = _mm_and_si128(
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_mm_cmpgt_epi8(current_bytes, _mm_set1_epi8(0x8F)),
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maskF4);
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*has_error = _mm_or_si128(*has_error,
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_mm_or_si128(badfollowED, badfollowF4));
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}
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// map off1_hibits => error condition
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// hibits off1 cur
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// C => < C2 && true
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// E => < E1 && < A0
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// F => < F1 && < 90
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// else false && false
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static void checkOverlong(__m128i current_bytes,
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__m128i off1_current_bytes,
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__m128i hibits,
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__m128i previous_hibits,
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__m128i *has_error)
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{
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__m128i off1_hibits = _mm_alignr_epi8(hibits, previous_hibits, 16 - 1);
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__m128i initial_mins = _mm_shuffle_epi8(
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_mm_setr_epi8(-128, -128, -128, -128, -128, -128, -128, -128,
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-128, -128, -128, -128, // 10xx => false
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0xC2, -128, // 110x
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0xE1, // 1110
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0xF1),
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off1_hibits);
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__m128i initial_under = _mm_cmpgt_epi8(initial_mins, off1_current_bytes);
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__m128i second_mins = _mm_shuffle_epi8(
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_mm_setr_epi8(-128, -128, -128, -128, -128, -128, -128, -128,
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-128, -128, -128, -128, // 10xx => false
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127, 127, // 110x => true
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0xA0, // 1110
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0x90),
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off1_hibits);
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__m128i second_under = _mm_cmpgt_epi8(second_mins, current_bytes);
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*has_error = _mm_or_si128(*has_error,
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_mm_and_si128(initial_under, second_under));
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}
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struct processed_utf_bytes {
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__m128i rawbytes;
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__m128i high_nibbles;
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__m128i carried_continuations;
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};
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static void count_nibbles(__m128i bytes,
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struct processed_utf_bytes *answer)
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{
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answer->rawbytes = bytes;
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answer->high_nibbles = _mm_and_si128(_mm_srli_epi16(bytes, 4),
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_mm_set1_epi8(0x0F));
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}
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// check whether the current bytes are valid UTF-8
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// at the end of the function, previous gets updated
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static struct processed_utf_bytes
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checkUTF8Bytes(__m128i current_bytes, struct processed_utf_bytes *previous,
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__m128i *has_error)
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{
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struct processed_utf_bytes pb;
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count_nibbles(current_bytes, &pb);
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checkSmallerThan0xF4(current_bytes, has_error);
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__m128i initial_lengths = continuationLengths(pb.high_nibbles);
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pb.carried_continuations = carryContinuations(
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initial_lengths,
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previous->carried_continuations);
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checkContinuations(initial_lengths, pb.carried_continuations, has_error);
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__m128i off1_current_bytes =
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_mm_alignr_epi8(pb.rawbytes, previous->rawbytes, 16 - 1);
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checkFirstContinuationMax(current_bytes, off1_current_bytes,
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has_error);
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checkOverlong(current_bytes, off1_current_bytes,
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pb.high_nibbles, previous->high_nibbles, has_error);
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return pb;
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}
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static bool validate_utf8_fast(const char *src, size_t len, ssize_t *len_out)
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{
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size_t i = 0, orig_len = len;
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__m128i has_error = _mm_setzero_si128();
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__m128i lfchars = _mm_set1_epi8('\n');
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__m128i lfresult = _mm_setzero_si128();
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struct processed_utf_bytes previous = {.rawbytes = _mm_setzero_si128(),
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.high_nibbles = _mm_setzero_si128(),
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.carried_continuations = _mm_setzero_si128()};
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if (len >= 16) {
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for (; i <= len - 16; i += 16) {
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__m128i current_bytes = _mm_loadu_si128(
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(const __m128i *) (src + i));
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previous = checkUTF8Bytes(current_bytes, &previous, &has_error);
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lfresult = _mm_cmpeq_epi8(current_bytes, lfchars);
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if (_mm_movemask_epi8(lfresult)) {
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for (; src[i] != '\n'; i++) {
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}
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len = i;
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break;
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}
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}
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}
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//last part
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if (i < len) {
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char buffer[16];
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memset(buffer, 0, 16);
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memcpy(buffer, src + i, len - i);
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__m128i current_bytes = _mm_loadu_si128((const __m128i *) (buffer));
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previous = checkUTF8Bytes(current_bytes, &previous, &has_error);
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for (; i < len && src[i] != '\n'; i++) {
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}
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} else {
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has_error = _mm_or_si128(_mm_cmpgt_epi8(previous.carried_continuations,
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_mm_setr_epi8(9, 9, 9, 9, 9, 9,
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9, 9, 9, 9, 9, 9,
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9, 9, 9, 1)),
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has_error);
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}
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if (i < orig_len && src[i] == '\n') {
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*len_out = i;
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}
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return _mm_testz_si128(has_error, has_error);
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}
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#ifdef __cplusplus
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}
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#endif
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#endif
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