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