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 <cstring>
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 #include "absl/strings/string_view.h"
22
23 namespace absl {
24 ABSL_NAMESPACE_BEGIN
25 namespace crc_internal {
26
Compute(void * __restrict dst,const void * __restrict src,std::size_t length,crc32c_t initial_crc) const27 absl::crc32c_t FallbackCrcMemcpyEngine::Compute(void* __restrict dst,
28 const void* __restrict src,
29 std::size_t length,
30 crc32c_t initial_crc) const {
31 constexpr size_t kBlockSize = 8192;
32 absl::crc32c_t crc = initial_crc;
33
34 const char* src_bytes = reinterpret_cast<const char*>(src);
35 char* dst_bytes = reinterpret_cast<char*>(dst);
36
37 // Copy + CRC loop - run 8k chunks until we are out of full chunks. CRC
38 // then copy was found to be slightly more efficient in our test cases.
39 std::size_t offset = 0;
40 for (; offset + kBlockSize < length; offset += kBlockSize) {
41 crc = absl::ExtendCrc32c(crc,
42 absl::string_view(src_bytes + offset, kBlockSize));
43 memcpy(dst_bytes + offset, src_bytes + offset, kBlockSize);
44 }
45
46 // Save some work if length is 0.
47 if (offset < length) {
48 std::size_t final_copy_size = length - offset;
49 crc = absl::ExtendCrc32c(
50 crc, absl::string_view(src_bytes + offset, final_copy_size));
51 memcpy(dst_bytes + offset, src_bytes + offset, final_copy_size);
52 }
53
54 return crc;
55 }
56
57 // Compile the following only if we don't have
58 #if !defined(ABSL_INTERNAL_HAVE_X86_64_ACCELERATED_CRC_MEMCPY_ENGINE) && \
59 !defined(ABSL_INTERNAL_HAVE_ARM_ACCELERATED_CRC_MEMCPY_ENGINE)
60
GetArchSpecificEngines()61 CrcMemcpy::ArchSpecificEngines CrcMemcpy::GetArchSpecificEngines() {
62 CrcMemcpy::ArchSpecificEngines engines;
63 engines.temporal = new FallbackCrcMemcpyEngine();
64 engines.non_temporal = new FallbackCrcMemcpyEngine();
65 return engines;
66 }
67
GetTestEngine(int,int)68 std::unique_ptr<CrcMemcpyEngine> CrcMemcpy::GetTestEngine(int /*vector*/,
69 int /*integer*/) {
70 return std::make_unique<FallbackCrcMemcpyEngine>();
71 }
72
73 #endif // !ABSL_INTERNAL_HAVE_X86_64_ACCELERATED_CRC_MEMCPY_ENGINE &&
74 // !ABSL_INTERNAL_HAVE_ARM_ACCELERATED_CRC_MEMCPY_ENGINE
75
76 } // namespace crc_internal
77 ABSL_NAMESPACE_END
78 } // namespace absl
79