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-rw-r--r--src/simdutf8check.h237
1 files changed, 237 insertions, 0 deletions
diff --git a/src/simdutf8check.h b/src/simdutf8check.h
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+++ b/src/simdutf8check.h
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+/**
+ * https://github.com/lemire/fastvalidate-utf-8
+ */
+
+#ifndef SIMDUTF8CHECK_H
+#define SIMDUTF8CHECK_H
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <x86intrin.h>
+
+#include "base/lnav_log.hh"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * 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
+ *
+ */
+
+// all byte values must be no larger than 0xF4
+static 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 __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 __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 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 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 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 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 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;
+}
+
+static bool validate_utf8_fast(const char *src, size_t len, ssize_t *len_out)
+{
+ size_t i = 0, orig_len = len;
+ __m128i has_error = _mm_setzero_si128();
+ __m128i lfchars = _mm_set1_epi8('\n');
+ __m128i lfresult = _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);
+ lfresult = _mm_cmpeq_epi8(current_bytes, lfchars);
+ if (_mm_movemask_epi8(lfresult)) {
+ for (; src[i] != '\n'; i++) {
+ }
+ len = i;
+ break;
+ }
+ }
+ }
+
+ //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);
+ for (; i < len && src[i] != '\n'; i++) {
+ }
+ } 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);
+ }
+
+ if (i < orig_len && src[i] == '\n') {
+ *len_out = i;
+ }
+
+ return _mm_testz_si128(has_error, has_error);
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif