1 /* 2 * Copyright (C) 2019 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_EXT_BASE_HASH_H_ 18 #define INCLUDE_PERFETTO_EXT_BASE_HASH_H_ 19 20 #include <stddef.h> 21 #include <stdint.h> 22 #include <type_traits> 23 24 namespace perfetto { 25 namespace base { 26 27 // A helper class which computes a 64-bit hash of the input data. 28 // The algorithm used is FNV-1a as it is fast and easy to implement and has 29 // relatively few collisions. 30 // WARNING: This hash function should not be used for any cryptographic purpose. 31 class Hash { 32 public: 33 // Creates an empty hash object Hash()34 Hash() {} 35 36 // Hashes a numeric value. 37 template < 38 typename T, 39 typename std::enable_if<std::is_arithmetic<T>::value, bool>::type = true> Update(T data)40 void Update(T data) { 41 Update(reinterpret_cast<const char*>(&data), sizeof(data)); 42 } 43 44 // Hashes a byte array. Update(const char * data,size_t size)45 void Update(const char* data, size_t size) { 46 for (size_t i = 0; i < size; i++) { 47 result_ ^= static_cast<uint8_t>(data[i]); 48 result_ *= kFnv1a64Prime; 49 } 50 } 51 digest()52 uint64_t digest() { return result_; } 53 54 private: 55 static constexpr uint64_t kFnv1a64OffsetBasis = 0xcbf29ce484222325; 56 static constexpr uint64_t kFnv1a64Prime = 0x100000001b3; 57 58 uint64_t result_ = kFnv1a64OffsetBasis; 59 }; 60 61 } // namespace base 62 } // namespace perfetto 63 64 #endif // INCLUDE_PERFETTO_EXT_BASE_HASH_H_ 65