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// Copyright 2022 The Abseil Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include <cstdint>
#include <memory>
#include "absl/base/config.h"
#include "absl/crc/crc32c.h"
#include "absl/crc/internal/crc_memcpy.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace crc_internal {
absl::crc32c_t FallbackCrcMemcpyEngine::Compute(void* __restrict dst,
const void* __restrict src,
std::size_t length,
crc32c_t initial_crc) const {
constexpr size_t kBlockSize = 8192;
absl::crc32c_t crc = initial_crc;
const char* src_bytes = reinterpret_cast<const char*>(src);
char* dst_bytes = reinterpret_cast<char*>(dst);
// Copy + CRC loop - run 8k chunks until we are out of full chunks. CRC
// then copy was found to be slightly more efficient in our test cases.
std::size_t offset = 0;
for (; offset + kBlockSize < length; offset += kBlockSize) {
crc = absl::ExtendCrc32c(crc,
absl::string_view(src_bytes + offset, kBlockSize));
memcpy(dst_bytes + offset, src_bytes + offset, kBlockSize);
}
// Save some work if length is 0.
if (offset < length) {
std::size_t final_copy_size = length - offset;
crc = absl::ExtendCrc32c(
crc, absl::string_view(src_bytes + offset, final_copy_size));
memcpy(dst_bytes + offset, src_bytes + offset, final_copy_size);
}
return crc;
}
// Compile the following only if we don't have
#ifndef ABSL_INTERNAL_HAVE_X86_64_ACCELERATED_CRC_MEMCPY_ENGINE
CrcMemcpy::ArchSpecificEngines CrcMemcpy::GetArchSpecificEngines() {
CrcMemcpy::ArchSpecificEngines engines;
engines.temporal = new FallbackCrcMemcpyEngine();
engines.non_temporal = new FallbackCrcMemcpyEngine();
return engines;
}
std::unique_ptr<CrcMemcpyEngine> CrcMemcpy::GetTestEngine(int /*vector*/,
int /*integer*/) {
return std::make_unique<FallbackCrcMemcpyEngine>();
}
#endif // ABSL_INTERNAL_HAVE_X86_64_ACCELERATED_CRC_MEMCPY_ENGINE
} // namespace crc_internal
ABSL_NAMESPACE_END
} // namespace absl
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