1 /* 2 * Copyright (C) 2021 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef INCLUDE_PERFETTO_TRACING_INTERNAL_FNV1A_H_ 18 #define INCLUDE_PERFETTO_TRACING_INTERNAL_FNV1A_H_ 19 20 #include <cstddef> 21 #include <cstdint> 22 23 namespace perfetto { 24 namespace internal { 25 26 // Constexpr functions to compute a 64-bit hash of the input data. The algorithm 27 // used is FNV-1a as it is fast and easy to implement and has relatively few 28 // collisions. 29 // 30 // WARNING: This hash function should not be used for any cryptographic purpose. 31 32 static constexpr uint64_t kFnv1a64OffsetBasis = 0xcbf29ce484222325; 33 static constexpr uint64_t kFnv1a64Prime = 0x100000001b3; 34 Fnv1a(const char * s)35static constexpr inline uint64_t Fnv1a(const char* s) { 36 uint64_t ret = kFnv1a64OffsetBasis; 37 for (; *s; s++) { 38 ret = ret ^ static_cast<uint8_t>(*s); 39 ret *= kFnv1a64Prime; 40 } 41 return ret; 42 } 43 Fnv1a(const void * data,size_t size)44static constexpr inline uint64_t Fnv1a(const void* data, size_t size) { 45 uint64_t ret = kFnv1a64OffsetBasis; 46 const uint8_t* s = static_cast<const uint8_t*>(data); 47 for (size_t i = 0; i < size; i++) { 48 ret = ret ^ s[i]; 49 ret *= kFnv1a64Prime; 50 } 51 return ret; 52 } 53 54 } // namespace internal 55 } // namespace perfetto 56 57 #endif // INCLUDE_PERFETTO_TRACING_INTERNAL_FNV1A_H_ 58