1 // Copyright 2022 The Abseil Authors
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // https://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 #include <cstdint>
16 #include <memory>
17
18 #include "absl/base/config.h"
19 #include "absl/crc/crc32c.h"
20 #include "absl/crc/internal/crc_memcpy.h"
21
22 namespace absl {
23 ABSL_NAMESPACE_BEGIN
24 namespace crc_internal {
25
Compute(void * __restrict dst,const void * __restrict src,std::size_t length,crc32c_t initial_crc) const26 absl::crc32c_t FallbackCrcMemcpyEngine::Compute(void* __restrict dst,
27 const void* __restrict src,
28 std::size_t length,
29 crc32c_t initial_crc) const {
30 constexpr size_t kBlockSize = 8192;
31 absl::crc32c_t crc = initial_crc;
32
33 const char* src_bytes = reinterpret_cast<const char*>(src);
34 char* dst_bytes = reinterpret_cast<char*>(dst);
35
36 // Copy + CRC loop - run 8k chunks until we are out of full chunks. CRC
37 // then copy was found to be slightly more efficient in our test cases.
38 std::size_t offset = 0;
39 for (; offset + kBlockSize < length; offset += kBlockSize) {
40 crc = absl::ExtendCrc32c(crc,
41 absl::string_view(src_bytes + offset, kBlockSize));
42 memcpy(dst_bytes + offset, src_bytes + offset, kBlockSize);
43 }
44
45 // Save some work if length is 0.
46 if (offset < length) {
47 std::size_t final_copy_size = length - offset;
48 crc = absl::ExtendCrc32c(
49 crc, absl::string_view(src_bytes + offset, final_copy_size));
50 memcpy(dst_bytes + offset, src_bytes + offset, final_copy_size);
51 }
52
53 return crc;
54 }
55
56 // Compile the following only if we don't have
57 #ifndef ABSL_INTERNAL_HAVE_X86_64_ACCELERATED_CRC_MEMCPY_ENGINE
58
GetArchSpecificEngines()59 CrcMemcpy::ArchSpecificEngines CrcMemcpy::GetArchSpecificEngines() {
60 CrcMemcpy::ArchSpecificEngines engines;
61 engines.temporal = new FallbackCrcMemcpyEngine();
62 engines.non_temporal = new FallbackCrcMemcpyEngine();
63 return engines;
64 }
65
GetTestEngine(int,int)66 std::unique_ptr<CrcMemcpyEngine> CrcMemcpy::GetTestEngine(int /*vector*/,
67 int /*integer*/) {
68 return std::make_unique<FallbackCrcMemcpyEngine>();
69 }
70
71 #endif // ABSL_INTERNAL_HAVE_X86_64_ACCELERATED_CRC_MEMCPY_ENGINE
72
73 } // namespace crc_internal
74 ABSL_NAMESPACE_END
75 } // namespace absl
76