12345678910111213141516171819202122232425262728293031323334353637383940414243 |
- // Copyright 2017 The Chromium Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style license that can be
- // found in the LICENSE file.
- #include "components/zucchini/crc32.h"
- #include <array>
- #include "base/check_op.h"
- namespace zucchini {
- namespace {
- std::array<uint32_t, 256> MakeCrc32Table() {
- constexpr uint32_t kCrc32Poly = 0xEDB88320;
- std::array<uint32_t, 256> crc32Table;
- for (uint32_t i = 0; i < 256; ++i) {
- uint32_t r = i;
- for (int j = 0; j < 8; ++j)
- r = (r >> 1) ^ (kCrc32Poly & ~((r & 1) - 1));
- crc32Table[i] = r;
- }
- return crc32Table;
- }
- } // namespace
- // Minimalistic CRC-32 implementation for Zucchini usage. Adapted from LZMA SDK
- // (found at third_party/lzma_sdk/C/7zCrc.c), which is public domain.
- uint32_t CalculateCrc32(const uint8_t* first, const uint8_t* last) {
- DCHECK_GE(last, first);
- static const std::array<uint32_t, 256> kCrc32Table = MakeCrc32Table();
- uint32_t ret = 0xFFFFFFFF;
- for (; first != last; ++first)
- ret = kCrc32Table[(ret ^ *first) & 0xFF] ^ (ret >> 8);
- return ret ^ 0xFFFFFFFF;
- }
- } // namespace zucchini
|