1 /* 2 * Copyright (c) 2024 Huawei Device Co., Ltd. 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 * http://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 16 #ifndef API_BASE_UTIL_COMPILE_TIME_HASHES_H 17 #define API_BASE_UTIL_COMPILE_TIME_HASHES_H 18 19 #include <cstdint> 20 21 #include <base/containers/type_traits.h> 22 #include <base/namespace.h> 23 BASE_BEGIN_NAMESPACE()24BASE_BEGIN_NAMESPACE() 25 namespace CompileTime { 26 constexpr uint64_t FNV_OFFSET_BASIS = 0xcbf29ce484222325ull; 27 constexpr uint64_t FNV_PRIME = 1099511628211ull; 28 29 constexpr uint64_t lo(uint64_t x) 30 { 31 return x & 0xFFFFFFFF; 32 } 33 34 constexpr uint64_t hi(uint64_t x) 35 { 36 return x >> 32ull; 37 } 38 39 constexpr uint64_t mulu64(uint64_t a, uint64_t b) 40 { 41 return 0 + (lo(a) * lo(b) & uint32_t(-1)) + 42 (((((hi(lo(a) * lo(b)) + lo(a) * hi(b)) & uint32_t(-1)) + hi(a) * lo(b)) & uint32_t(-1)) << 32ull); 43 } 44 45 inline constexpr uint64_t FNV1aHash(const char* const first, uint64_t hash = FNV_OFFSET_BASIS) 46 { 47 if (*first == 0) { 48 return hash; 49 } 50 hash ^= (uint64_t)*first; 51 // Using custom 64 bit multiply to silence "constant integer overflow" warning. 52 hash = mulu64(hash, FNV_PRIME); 53 return FNV1aHash(first + 1, hash); 54 } 55 } // namespace CompileTime 56 BASE_END_NAMESPACE() 57 #endif // API_BASE_UTIL_COMPILE_TIME_HASHES_H