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The Tor Browser
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crc_non_temporal_memcpy.cc (3365B)

      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 <cstddef>
     16 
     17 #include "absl/base/config.h"
     18 #include "absl/crc/crc32c.h"
     19 #include "absl/crc/internal/crc_memcpy.h"
     20 #include "absl/crc/internal/non_temporal_memcpy.h"
     21 #include "absl/strings/string_view.h"
     22 
     23 namespace absl {
     24 ABSL_NAMESPACE_BEGIN
     25 namespace crc_internal {
     26 
     27 crc32c_t CrcNonTemporalMemcpyEngine::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  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.
     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    non_temporal_store_memcpy(dst_bytes + offset, src_bytes + offset,
     43                              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 = ExtendCrc32c(crc,
     50                       absl::string_view(src_bytes + offset, final_copy_size));
     51 
     52    non_temporal_store_memcpy(dst_bytes + offset, src_bytes + offset,
     53                              final_copy_size);
     54  }
     55 
     56  return crc;
     57 }
     58 
     59 crc32c_t CrcNonTemporalMemcpyAVXEngine::Compute(void* __restrict dst,
     60                                                const void* __restrict src,
     61                                                std::size_t length,
     62                                                crc32c_t initial_crc) const {
     63  constexpr size_t kBlockSize = 8192;
     64  crc32c_t crc = initial_crc;
     65 
     66  const char* src_bytes = reinterpret_cast<const char*>(src);
     67  char* dst_bytes = reinterpret_cast<char*>(dst);
     68 
     69  // Copy + CRC loop - run 8k chunks until we are out of full chunks.
     70  std::size_t offset = 0;
     71  for (; offset + kBlockSize < length; offset += kBlockSize) {
     72    crc = ExtendCrc32c(crc, absl::string_view(src_bytes + offset, kBlockSize));
     73 
     74    non_temporal_store_memcpy_avx(dst_bytes + offset, src_bytes + offset,
     75                                  kBlockSize);
     76  }
     77 
     78  // Save some work if length is 0.
     79  if (offset < length) {
     80    std::size_t final_copy_size = length - offset;
     81    crc = ExtendCrc32c(crc,
     82                       absl::string_view(src_bytes + offset, final_copy_size));
     83 
     84    non_temporal_store_memcpy_avx(dst_bytes + offset, src_bytes + offset,
     85                                  final_copy_size);
     86  }
     87 
     88  return crc;
     89 }
     90 
     91 }  // namespace crc_internal
     92 ABSL_NAMESPACE_END
     93 }  // namespace absl