| // Copyright 2019 The Chromium Authors |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "base/metrics/crc32.h" |
| #include "third_party/zlib/zlib.h" |
| |
| namespace base { |
| |
| uint32_t Crc32(uint32_t sum, span<const uint8_t> data) { |
| if (data.empty()) { |
| return sum; |
| } |
| |
| // Make sure zlib checks CPU features before further calls to crc32_z. |
| // zlib's crc32_z implementation says it's a convention to call |
| // crc32(0, NULL, 0); before making calls to crc32(), so it uses it as |
| // a place to cache CPU features if needed. |
| // There's no need to cache the results, since there's an internal zlib |
| // caching mechanism, so this function will just return if called multiple |
| // times. |
| (void)crc32_z(0L, Z_NULL, 0); |
| |
| return static_cast<uint32_t>( |
| (~crc32_z((~sum) & 0xffffffff, data.data(), data.size())) & 0xffffffff); |
| } |
| |
| } // namespace base |
