2 * Copyright 2017 Facebook, Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
17 #include <folly/Checksum.h>
18 #include <boost/crc.hpp>
19 #include <folly/CpuId.h>
20 #include <folly/detail/ChecksumDetail.h>
24 #if FOLLY_SSE_PREREQ(4, 2)
25 #include <nmmintrin.h>
33 crc32c_sw(const uint8_t* data, size_t nbytes, uint32_t startingChecksum);
34 #if FOLLY_SSE_PREREQ(4, 2)
36 // Fast SIMD implementation of CRC-32C for x86 with SSE 4.2
37 FOLLY_TARGET_ATTRIBUTE("sse4.2")
38 uint32_t crc32c_hw(const uint8_t *data, size_t nbytes,
39 uint32_t startingChecksum) {
40 uint32_t sum = startingChecksum;
43 // Process bytes one at a time until we reach an 8-byte boundary and can
44 // start doing aligned 64-bit reads.
45 static uintptr_t ALIGN_MASK = sizeof(uint64_t) - 1;
46 size_t mask = (size_t)((uintptr_t)data & ALIGN_MASK);
48 size_t limit = std::min(nbytes, sizeof(uint64_t) - mask);
49 while (offset < limit) {
50 sum = (uint32_t)_mm_crc32_u8(sum, data[offset]);
55 // Process 8 bytes at a time until we have fewer than 8 bytes left.
56 while (offset + sizeof(uint64_t) <= nbytes) {
57 const uint64_t* src = (const uint64_t*)(data + offset);
58 sum = uint32_t(_mm_crc32_u64(sum, *src));
59 offset += sizeof(uint64_t);
62 // Process any bytes remaining after the last aligned 8-byte block.
63 while (offset < nbytes) {
64 sum = (uint32_t)_mm_crc32_u8(sum, data[offset]);
71 crc32_sw(const uint8_t* data, size_t nbytes, uint32_t startingChecksum);
73 // Fast SIMD implementation of CRC-32 for x86 with pclmul
75 crc32_hw(const uint8_t* data, size_t nbytes, uint32_t startingChecksum) {
76 uint32_t sum = startingChecksum;
79 // Process unaligned bytes
80 if ((uintptr_t)data & 15) {
81 size_t limit = std::min(nbytes, -(uintptr_t)data & 15);
82 sum = crc32_sw(data, limit, sum);
88 sum = crc32_hw_aligned(sum, (const __m128i*)(data + offset), nbytes / 16);
89 offset += nbytes & ~15;
93 // Remaining unaligned bytes
94 return crc32_sw(data + offset, nbytes, sum);
97 bool crc32c_hw_supported() {
98 static folly::CpuId id;
102 bool crc32_hw_supported() {
103 static folly::CpuId id;
109 uint32_t crc32c_hw(const uint8_t *data, size_t nbytes,
110 uint32_t startingChecksum) {
111 throw std::runtime_error("crc32_hw is not implemented on this platform");
114 uint32_t crc32_hw(const uint8_t *data, size_t nbytes,
115 uint32_t startingChecksum) {
116 throw std::runtime_error("crc32_hw is not implemented on this platform");
119 bool crc32c_hw_supported() {
123 bool crc32_hw_supported() {
128 template <uint32_t CRC_POLYNOMIAL>
129 uint32_t crc_sw(const uint8_t* data, size_t nbytes, uint32_t startingChecksum) {
130 // Reverse the bits in the starting checksum so they'll be in the
131 // right internal format for Boost's CRC engine.
132 // O(1)-time, branchless bit reversal algorithm from
133 // http://graphics.stanford.edu/~seander/bithacks.html
134 startingChecksum = ((startingChecksum >> 1) & 0x55555555) |
135 ((startingChecksum & 0x55555555) << 1);
136 startingChecksum = ((startingChecksum >> 2) & 0x33333333) |
137 ((startingChecksum & 0x33333333) << 2);
138 startingChecksum = ((startingChecksum >> 4) & 0x0f0f0f0f) |
139 ((startingChecksum & 0x0f0f0f0f) << 4);
140 startingChecksum = ((startingChecksum >> 8) & 0x00ff00ff) |
141 ((startingChecksum & 0x00ff00ff) << 8);
142 startingChecksum = (startingChecksum >> 16) |
143 (startingChecksum << 16);
145 boost::crc_optimal<32, CRC_POLYNOMIAL, ~0U, 0, true, true> sum(
147 sum.process_bytes(data, nbytes);
148 return sum.checksum();
152 crc32c_sw(const uint8_t* data, size_t nbytes, uint32_t startingChecksum) {
153 constexpr uint32_t CRC32C_POLYNOMIAL = 0x1EDC6F41;
154 return crc_sw<CRC32C_POLYNOMIAL>(data, nbytes, startingChecksum);
158 crc32_sw(const uint8_t* data, size_t nbytes, uint32_t startingChecksum) {
159 constexpr uint32_t CRC32_POLYNOMIAL = 0x04C11DB7;
160 return crc_sw<CRC32_POLYNOMIAL>(data, nbytes, startingChecksum);
165 uint32_t crc32c(const uint8_t *data, size_t nbytes,
166 uint32_t startingChecksum) {
167 if (detail::crc32c_hw_supported()) {
168 return detail::crc32c_hw(data, nbytes, startingChecksum);
170 return detail::crc32c_sw(data, nbytes, startingChecksum);
174 uint32_t crc32(const uint8_t* data, size_t nbytes, uint32_t startingChecksum) {
175 if (detail::crc32_hw_supported()) {
176 return detail::crc32_hw(data, nbytes, startingChecksum);
178 return detail::crc32_sw(data, nbytes, startingChecksum);