Flow.cpp (2245B)
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 #include <stdint.h> 18 #ifdef XP_WIN 19 # include <windows.h> 20 #else 21 # include <time.h> 22 # include <unistd.h> 23 #endif 24 25 #include "mozilla/Flow.h" 26 27 // Some infrastructure that we use for computing a per process UUID 28 29 // FNV-1a hasher 30 // We use this to construct a randomish UUID by hashing the PID and the 31 // current time. 32 // 33 // It's probably not the best choice of hasher but it works for Perfetto 34 // so it's good enough for us. 35 struct Hasher { 36 static const uint64_t kOffsetBasis = 14695981039346656037ULL; 37 static const uint64_t kPrime = 1099511628211ULL; 38 39 uint64_t hash = kOffsetBasis; 40 41 void Update(const void* data, size_t size) { 42 const uint8_t* ptr = static_cast<const uint8_t*>(data); 43 for (size_t i = 0; i < size; ++i) { 44 hash ^= ptr[i]; 45 hash *= kPrime; 46 } 47 } 48 void Update(uint64_t value) { Update(&value, sizeof(value)); } 49 void Update(uint32_t value) { Update(&value, sizeof(value)); } 50 51 uint64_t Get() const { return hash; } 52 }; 53 54 static uint64_t CurrentTime() { 55 #ifdef XP_WIN 56 return GetTickCount64(); 57 #else 58 timespec ts; 59 clock_gettime(CLOCK_MONOTONIC, &ts); 60 return ts.tv_sec * 1000 + ts.tv_nsec / 1000000; 61 #endif 62 } 63 64 static uint64_t CurrentPID() { 65 #ifdef XP_WIN 66 return GetCurrentProcessId(); 67 #else 68 return getpid(); 69 #endif 70 } 71 72 // This is inspired by the perfetto code in TrackRegistry::ComputeProcessUuid 73 uint64_t ComputeProcessUUID() { 74 auto pid = CurrentPID(); 75 auto time = CurrentTime(); 76 Hasher hasher; 77 hasher.Update(pid); 78 hasher.Update(time); 79 return hasher.Get(); 80 } 81 82 MFBT_DATA uint64_t gProcessUUID; 83 84 MFBT_API void Flow::Init() { gProcessUUID = ComputeProcessUUID(); }