Protocol Buffers - Google's data interchange format (grpc依赖)
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458 lines
17 KiB
458 lines
17 KiB
// Copyright 2022 Google LLC |
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// |
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// Use of this source code is governed by an MIT-style |
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// license that can be found in the LICENSE file or at |
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// https://opensource.org/licenses/MIT. |
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/* This is a wrapper for the Google range-sse.cc algorithm which checks whether a |
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* sequence of bytes is a valid UTF-8 sequence and finds the longest valid prefix of |
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* the UTF-8 sequence. |
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* |
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* The key difference is that it checks for as much ASCII symbols as possible |
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* and then falls back to the range-sse.cc algorithm. The changes to the |
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* algorithm are cosmetic, mostly to trick the clang compiler to produce optimal |
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* code. |
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* |
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* For API see the utf8_validity.h header. |
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*/ |
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#include "utf8_validity.h" |
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#include <cstddef> |
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#include <cstdint> |
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#include "absl/strings/ascii.h" |
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#include "absl/strings/string_view.h" |
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#ifdef __SSE4_1__ |
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#include <emmintrin.h> |
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#include <smmintrin.h> |
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#include <tmmintrin.h> |
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#endif |
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namespace utf8_range { |
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namespace { |
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inline uint64_t UNALIGNED_LOAD64(const void* p) { |
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uint64_t t; |
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memcpy(&t, p, sizeof t); |
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return t; |
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} |
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inline bool TrailByteOk(const char c) { |
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return static_cast<int8_t>(c) <= static_cast<int8_t>(0xBF); |
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} |
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/* If ReturnPosition is false then it returns 1 if |data| is a valid utf8 |
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* sequence, otherwise returns 0. |
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* If ReturnPosition is set to true, returns the length in bytes of the prefix |
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of |data| that is all structurally valid UTF-8. |
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*/ |
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template <bool ReturnPosition> |
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size_t ValidUTF8Span(const char* data, const char* end) { |
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/* We return err_pos in the loop which is always 0 if !ReturnPosition */ |
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size_t err_pos = 0; |
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size_t codepoint_bytes = 0; |
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/* The early check is done because of early continue's on codepoints of all |
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* sizes, i.e. we first check for ascii and if it is, we call continue, then |
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* for 2 byte codepoints, etc. This is done in order to reduce indentation and |
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* improve readability of the codepoint validity check. |
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*/ |
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while (data + codepoint_bytes < end) { |
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if (ReturnPosition) { |
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err_pos += codepoint_bytes; |
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} |
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data += codepoint_bytes; |
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const size_t len = end - data; |
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const unsigned char byte1 = data[0]; |
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/* We do not skip many ascii bytes at the same time as this function is |
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used for tail checking (< 16 bytes) and for non x86 platforms. We also |
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don't think that cases where non-ASCII codepoints are followed by ascii |
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happen often. For small strings it also introduces some penalty. For |
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purely ascii UTF8 strings (which is the overwhelming case) we call |
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SkipAscii function which is multiplatform and extremely fast. |
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*/ |
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/* [00..7F] ASCII -> 1 byte */ |
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if (absl::ascii_isascii(byte1)) { |
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codepoint_bytes = 1; |
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continue; |
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} |
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/* [C2..DF], [80..BF] -> 2 bytes */ |
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if (len >= 2 && byte1 >= 0xC2 && byte1 <= 0xDF && TrailByteOk(data[1])) { |
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codepoint_bytes = 2; |
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continue; |
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} |
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if (len >= 3) { |
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const unsigned char byte2 = data[1]; |
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const unsigned char byte3 = data[2]; |
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/* Is byte2, byte3 between [0x80, 0xBF] |
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* Check for 0x80 was done above. |
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*/ |
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if (!TrailByteOk(byte2) || !TrailByteOk(byte3)) { |
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return err_pos; |
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} |
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if (/* E0, A0..BF, 80..BF */ |
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((byte1 == 0xE0 && byte2 >= 0xA0) || |
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/* E1..EC, 80..BF, 80..BF */ |
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(byte1 >= 0xE1 && byte1 <= 0xEC) || |
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/* ED, 80..9F, 80..BF */ |
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(byte1 == 0xED && byte2 <= 0x9F) || |
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/* EE..EF, 80..BF, 80..BF */ |
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(byte1 >= 0xEE && byte1 <= 0xEF))) { |
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codepoint_bytes = 3; |
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continue; |
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} |
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if (len >= 4) { |
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const unsigned char byte4 = data[3]; |
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/* Is byte4 between 0x80 ~ 0xBF */ |
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if (!TrailByteOk(byte4)) { |
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return err_pos; |
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} |
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if (/* F0, 90..BF, 80..BF, 80..BF */ |
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((byte1 == 0xF0 && byte2 >= 0x90) || |
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/* F1..F3, 80..BF, 80..BF, 80..BF */ |
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(byte1 >= 0xF1 && byte1 <= 0xF3) || |
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/* F4, 80..8F, 80..BF, 80..BF */ |
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(byte1 == 0xF4 && byte2 <= 0x8F))) { |
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codepoint_bytes = 4; |
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continue; |
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} |
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} |
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} |
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return err_pos; |
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} |
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if (ReturnPosition) { |
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err_pos += codepoint_bytes; |
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} |
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/* if ReturnPosition is false, this returns 1. |
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* if ReturnPosition is true, this returns err_pos. |
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*/ |
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return err_pos + (1 - ReturnPosition); |
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} |
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/* Returns the number of bytes needed to skip backwards to get to the first |
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byte of codepoint. |
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*/ |
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inline int CodepointSkipBackwards(int32_t codepoint_word) { |
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const int8_t* const codepoint = |
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reinterpret_cast<const int8_t*>(&codepoint_word); |
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if (!TrailByteOk(codepoint[3])) { |
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return 1; |
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} else if (!TrailByteOk(codepoint[2])) { |
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return 2; |
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} else if (!TrailByteOk(codepoint[1])) { |
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return 3; |
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} |
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return 0; |
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} |
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/* Skipping over ASCII as much as possible, per 8 bytes. It is intentional |
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as most strings to check for validity consist only of 1 byte codepoints. |
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*/ |
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inline const char* SkipAscii(const char* data, const char* end) { |
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while (8 <= end - data && |
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(UNALIGNED_LOAD64(data) & 0x8080808080808080) == 0) { |
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data += 8; |
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} |
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while (data < end && absl::ascii_isascii(*data)) { |
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++data; |
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} |
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return data; |
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} |
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template <bool ReturnPosition> |
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size_t ValidUTF8(const char* data, size_t len) { |
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if (len == 0) return 1 - ReturnPosition; |
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const char* const end = data + len; |
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data = SkipAscii(data, end); |
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/* SIMD algorithm always outperforms the naive version for any data of |
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length >=16. |
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*/ |
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if (end - data < 16) { |
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return (ReturnPosition ? (data - (end - len)) : 0) + |
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ValidUTF8Span<ReturnPosition>(data, end); |
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} |
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#ifndef __SSE4_1__ |
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return (ReturnPosition ? (data - (end - len)) : 0) + |
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ValidUTF8Span<ReturnPosition>(data, end); |
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#else |
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/* This code checks that utf-8 ranges are structurally valid 16 bytes at once |
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* using superscalar instructions. |
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* The mapping between ranges of codepoint and their corresponding utf-8 |
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* sequences is below. |
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*/ |
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/* |
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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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/* First we compute the type for each byte, as given by the table below. |
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* This type will be used as an index later on. |
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*/ |
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/* |
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* Index Min Max Byte Type |
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* 0 00 7F Single byte sequence |
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* 1,2,3 80 BF Second, third and fourth byte for many of the sequences. |
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* 4 A0 BF Second byte after E0 |
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* 5 80 9F Second byte after ED |
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* 6 90 BF Second byte after F0 |
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* 7 80 8F Second byte after F4 |
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* 8 C2 F4 First non ASCII byte |
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* 9..15 7F 80 Invalid byte |
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*/ |
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/* After the first step we compute the index for all bytes, then we permute |
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the bytes according to their indices to check the ranges from the range |
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table. |
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* The range for a given type can be found in the range_min_table and |
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range_max_table, the range for type/index X is in range_min_table[X] ... |
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range_max_table[X]. |
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*/ |
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/* Algorithm: |
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* Put index zero to all bytes. |
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* Find all non ASCII characters, give them index 8. |
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* For each tail byte in a codepoint sequence, give it an index corresponding |
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to the 1 based index from the end. |
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* If the first byte of the codepoint is in the [C0...DF] range, we write |
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index 1 in the following byte. |
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* If the first byte of the codepoint is in the range [E0...EF], we write |
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indices 2 and 1 in the next two bytes. |
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* If the first byte of the codepoint is in the range [F0...FF] we write |
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indices 3,2,1 into the next three bytes. |
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* For finding the number of bytes we need to look at high nibbles (4 bits) |
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and do the lookup from the table, it can be done with shift by 4 + shuffle |
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instructions. We call it `first_len`. |
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* Then we shift first_len by 8 bits to get the indices of the 2nd bytes. |
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* Saturating sub 1 and shift by 8 bits to get the indices of the 3rd bytes. |
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* Again to get the indices of the 4th bytes. |
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* Take OR of all that 4 values and check within range. |
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*/ |
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/* For example: |
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* input C3 80 68 E2 80 20 A6 F0 A0 80 AC 20 F0 93 80 80 |
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* first_len 1 0 0 2 0 0 0 3 0 0 0 0 3 0 0 0 |
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* 1st byte 8 0 0 8 0 0 0 8 0 0 0 0 8 0 0 0 |
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* 2nd byte 0 1 0 0 2 0 0 0 3 0 0 0 0 3 0 0 // Shift + sub |
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* 3rd byte 0 0 0 0 0 1 0 0 0 2 0 0 0 0 2 0 // Shift + sub |
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* 4th byte 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 1 // Shift + sub |
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* Index 8 1 0 8 2 1 0 8 3 2 1 0 8 3 2 1 // OR of results |
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*/ |
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/* Checking for errors: |
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* Error checking is done by looking up the high nibble (4 bits) of each byte |
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against an error checking table. |
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* Because the lookup value for the second byte depends of the value of the |
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first byte in codepoint, we use saturated operations to adjust the index. |
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* Specifically we need to add 2 for E0, 3 for ED, 3 for F0 and 4 for F4 to |
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match the correct index. |
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* If we subtract from all bytes EF then EO -> 241, ED -> 254, F0 -> 1, |
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F4 -> 5 |
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* Do saturating sub 240, then E0 -> 1, ED -> 14 and we can do lookup to |
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match the adjustment |
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* Add saturating 112, then F0 -> 113, F4 -> 117, all that were > 16 will |
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be more 128 and lookup in ef_fe_table will return 0 but for F0 |
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and F4 it will be 4 and 5 accordingly |
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*/ |
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/* |
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* Then just check the appropriate ranges with greater/smaller equal |
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instructions. Check tail with a naive algorithm. |
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* To save from previous 16 byte checks we just align previous_first_len to |
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get correct continuations of the codepoints. |
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*/ |
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/* |
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* Map high nibble of "First Byte" to legal character length minus 1 |
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* 0x00 ~ 0xBF --> 0 |
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* 0xC0 ~ 0xDF --> 1 |
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* 0xE0 ~ 0xEF --> 2 |
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* 0xF0 ~ 0xFF --> 3 |
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*/ |
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const __m128i first_len_table = |
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_mm_setr_epi8(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 2, 3); |
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/* Map "First Byte" to 8-th item of range table (0xC2 ~ 0xF4) */ |
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const __m128i first_range_table = |
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_mm_setr_epi8(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 8, 8, 8, 8); |
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/* |
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* Range table, map range index to min and max values |
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*/ |
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const __m128i range_min_table = |
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_mm_setr_epi8(0x00, 0x80, 0x80, 0x80, 0xA0, 0x80, 0x90, 0x80, 0xC2, 0x7F, |
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0x7F, 0x7F, 0x7F, 0x7F, 0x7F, 0x7F); |
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const __m128i range_max_table = |
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_mm_setr_epi8(0x7F, 0xBF, 0xBF, 0xBF, 0xBF, 0x9F, 0xBF, 0x8F, 0xF4, 0x80, |
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0x80, 0x80, 0x80, 0x80, 0x80, 0x80); |
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/* |
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* Tables for fast handling of four special First Bytes(E0,ED,F0,F4), after |
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* which the Second Byte are not 80~BF. It contains "range index adjustment". |
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* +------------+---------------+------------------+----------------+ |
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* | First Byte | original range| range adjustment | adjusted range | |
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* +------------+---------------+------------------+----------------+ |
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* | E0 | 2 | 2 | 4 | |
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* +------------+---------------+------------------+----------------+ |
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* | ED | 2 | 3 | 5 | |
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* +------------+---------------+------------------+----------------+ |
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* | F0 | 3 | 3 | 6 | |
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* +------------+---------------+------------------+----------------+ |
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* | F4 | 4 | 4 | 8 | |
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* +------------+---------------+------------------+----------------+ |
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*/ |
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/* df_ee_table[1] -> E0, df_ee_table[14] -> ED as ED - E0 = 13 */ |
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// The values represent the adjustment in the Range Index table for a correct |
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// index. |
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const __m128i df_ee_table = |
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_mm_setr_epi8(0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0); |
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/* ef_fe_table[1] -> F0, ef_fe_table[5] -> F4, F4 - F0 = 4 */ |
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// The values represent the adjustment in the Range Index table for a correct |
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// index. |
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const __m128i ef_fe_table = |
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_mm_setr_epi8(0, 3, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0); |
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__m128i prev_input = _mm_set1_epi8(0); |
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__m128i prev_first_len = _mm_set1_epi8(0); |
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__m128i error = _mm_set1_epi8(0); |
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while (end - data >= 16) { |
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const __m128i input = |
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_mm_loadu_si128(reinterpret_cast<const __m128i*>(data)); |
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/* high_nibbles = input >> 4 */ |
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const __m128i high_nibbles = |
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_mm_and_si128(_mm_srli_epi16(input, 4), _mm_set1_epi8(0x0F)); |
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/* first_len = legal character length minus 1 */ |
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/* 0 for 00~7F, 1 for C0~DF, 2 for E0~EF, 3 for F0~FF */ |
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/* first_len = first_len_table[high_nibbles] */ |
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__m128i first_len = _mm_shuffle_epi8(first_len_table, high_nibbles); |
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/* First Byte: set range index to 8 for bytes within 0xC0 ~ 0xFF */ |
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/* range = first_range_table[high_nibbles] */ |
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__m128i range = _mm_shuffle_epi8(first_range_table, high_nibbles); |
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/* Second Byte: set range index to first_len */ |
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/* 0 for 00~7F, 1 for C0~DF, 2 for E0~EF, 3 for F0~FF */ |
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/* range |= (first_len, prev_first_len) << 1 byte */ |
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range = _mm_or_si128(range, _mm_alignr_epi8(first_len, prev_first_len, 15)); |
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/* Third Byte: set range index to saturate_sub(first_len, 1) */ |
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/* 0 for 00~7F, 0 for C0~DF, 1 for E0~EF, 2 for F0~FF */ |
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__m128i tmp1; |
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__m128i tmp2; |
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/* tmp1 = saturate_sub(first_len, 1) */ |
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tmp1 = _mm_subs_epu8(first_len, _mm_set1_epi8(1)); |
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/* tmp2 = saturate_sub(prev_first_len, 1) */ |
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tmp2 = _mm_subs_epu8(prev_first_len, _mm_set1_epi8(1)); |
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/* range |= (tmp1, tmp2) << 2 bytes */ |
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range = _mm_or_si128(range, _mm_alignr_epi8(tmp1, tmp2, 14)); |
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/* Fourth Byte: set range index to saturate_sub(first_len, 2) */ |
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/* 0 for 00~7F, 0 for C0~DF, 0 for E0~EF, 1 for F0~FF */ |
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/* tmp1 = saturate_sub(first_len, 2) */ |
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tmp1 = _mm_subs_epu8(first_len, _mm_set1_epi8(2)); |
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/* tmp2 = saturate_sub(prev_first_len, 2) */ |
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tmp2 = _mm_subs_epu8(prev_first_len, _mm_set1_epi8(2)); |
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/* range |= (tmp1, tmp2) << 3 bytes */ |
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range = _mm_or_si128(range, _mm_alignr_epi8(tmp1, tmp2, 13)); |
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/* |
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* Now we have below range indices calculated |
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* Correct cases: |
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* - 8 for C0~FF |
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* - 3 for 1st byte after F0~FF |
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* - 2 for 1st byte after E0~EF or 2nd byte after F0~FF |
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* - 1 for 1st byte after C0~DF or 2nd byte after E0~EF or |
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* 3rd byte after F0~FF |
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* - 0 for others |
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* Error cases: |
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* >9 for non ascii First Byte overlapping |
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* E.g., F1 80 C2 90 --> 8 3 10 2, where 10 indicates error |
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*/ |
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/* Adjust Second Byte range for special First Bytes(E0,ED,F0,F4) */ |
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/* Overlaps lead to index 9~15, which are illegal in range table */ |
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__m128i shift1; |
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__m128i pos; |
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__m128i range2; |
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/* shift1 = (input, prev_input) << 1 byte */ |
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shift1 = _mm_alignr_epi8(input, prev_input, 15); |
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pos = _mm_sub_epi8(shift1, _mm_set1_epi8(0xEF)); |
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/* |
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* shift1: | EF F0 ... FE | FF 00 ... ... DE | DF E0 ... EE | |
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* pos: | 0 1 15 | 16 17 239| 240 241 255| |
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* pos-240: | 0 0 0 | 0 0 0 | 0 1 15 | |
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* pos+112: | 112 113 127| >= 128 | >= 128 | |
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*/ |
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tmp1 = _mm_subs_epu8(pos, _mm_set1_epi8(-16)); |
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range2 = _mm_shuffle_epi8(df_ee_table, tmp1); |
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tmp2 = _mm_adds_epu8(pos, _mm_set1_epi8(112)); |
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range2 = _mm_add_epi8(range2, _mm_shuffle_epi8(ef_fe_table, tmp2)); |
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range = _mm_add_epi8(range, range2); |
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/* Load min and max values per calculated range index */ |
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__m128i min_range = _mm_shuffle_epi8(range_min_table, range); |
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__m128i max_range = _mm_shuffle_epi8(range_max_table, range); |
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/* Check value range */ |
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if (ReturnPosition) { |
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error = _mm_cmplt_epi8(input, min_range); |
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error = _mm_or_si128(error, _mm_cmpgt_epi8(input, max_range)); |
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/* 5% performance drop from this conditional branch */ |
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if (!_mm_testz_si128(error, error)) { |
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break; |
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} |
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} else { |
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error = _mm_or_si128(error, _mm_cmplt_epi8(input, min_range)); |
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error = _mm_or_si128(error, _mm_cmpgt_epi8(input, max_range)); |
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} |
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prev_input = input; |
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prev_first_len = first_len; |
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data += 16; |
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} |
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/* If we got to the end, we don't need to skip any bytes backwards */ |
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if (ReturnPosition && (data - (end - len)) == 0) { |
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return ValidUTF8Span<true>(data, end); |
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} |
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/* Find previous codepoint (not 80~BF) */ |
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data -= CodepointSkipBackwards(_mm_extract_epi32(prev_input, 3)); |
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if (ReturnPosition) { |
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return (data - (end - len)) + ValidUTF8Span<true>(data, end); |
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} |
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/* Test if there was any error */ |
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if (!_mm_testz_si128(error, error)) { |
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return 0; |
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} |
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/* Check the tail */ |
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return ValidUTF8Span<false>(data, end); |
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#endif |
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} |
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} // namespace |
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bool IsStructurallyValid(absl::string_view str) { |
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return ValidUTF8</*ReturnPosition=*/false>(str.data(), str.size()); |
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} |
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size_t SpanStructurallyValid(absl::string_view str) { |
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return ValidUTF8</*ReturnPosition=*/true>(str.data(), str.size()); |
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} |
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} // namespace utf8_range
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