// 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 <cstring>

#include <memory>

#include "absl/base/config.h"

#include "absl/crc/crc32c.h"

#include "absl/crc/internal/crc_memcpy.h"

#include "absl/strings/string_view.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

#if !defined(ABSL_INTERNAL_HAVE_X86_64_ACCELERATED_CRC_MEMCPY_ENGINE) && \

    !defined(ABSL_INTERNAL_HAVE_ARM_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 &&

        // !ABSL_INTERNAL_HAVE_ARM_ACCELERATED_CRC_MEMCPY_ENGINE

}  // namespace crc_internal

ABSL_NAMESPACE_END

}  // namespace absl