fiber.hh revision 12846:f863a61d8b16
1/* 2 * Copyright 2018 Google, Inc. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions are 6 * met: redistributions of source code must retain the above copyright 7 * notice, this list of conditions and the following disclaimer; 8 * redistributions in binary form must reproduce the above copyright 9 * notice, this list of conditions and the following disclaimer in the 10 * documentation and/or other materials provided with the distribution; 11 * neither the name of the copyright holders nor the names of its 12 * contributors may be used to endorse or promote products derived from 13 * this software without specific prior written permission. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 18 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 19 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 20 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 21 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 25 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26 * 27 * Authors: Gabe Black 28 */ 29 30#ifndef __BASE_FIBER_HH__ 31#define __BASE_FIBER_HH__ 32 33// ucontext functions (like getcontext, setcontext etc) have been marked 34// as deprecated and are hence hidden in latest macOS releases. 35// By defining _XOPEN_SOURCE we make them available at compilation time. 36#if defined(__APPLE__) && defined(__MACH__) 37#define _XOPEN_SOURCE 600 38#include <ucontext.h> 39#undef _XOPEN_SOURCE 40#else 41#include <ucontext.h> 42#endif 43 44#include <cstddef> 45#include <cstdint> 46 47/** 48 * This class represents a fiber, which is a light weight sort of thread which 49 * is cooperatively scheduled and runs sequentially with other fibers, swapping 50 * in and out of a single actual thread of execution. 51 * 52 * To define your own threads, create a subclass of Fiber and override its 53 * main() function to do what you want your fiber to do. You can start it by 54 * calling its run() method which will stop your execution and start the other 55 * fiber in your place. 56 * 57 * If your main() function ends, that fiber will automatically switch to either 58 * the primary fiber, or to a particular fiber you specified at construction 59 * time, and your fiber is considered finished. 60 */ 61 62class Fiber 63{ 64 public: 65 const static size_t DefaultStackSize = 0x50000; 66 67 /// stack_size is the size of the stack available to this fiber. 68 /// link points to another fiber which will start executing when this 69 /// fiber's main function returns. 70 Fiber(size_t stack_size=DefaultStackSize); 71 Fiber(Fiber *link, size_t stack_size=DefaultStackSize); 72 73 virtual ~Fiber(); 74 75 /// Start executing the fiber represented by this object. This function 76 /// will "return" when the current fiber is switched back to later on. 77 void run(); 78 79 /// Returns whether the "main" function of this fiber has finished. 80 /// 81 bool finished() const { return _finished; }; 82 83 /// Get a pointer to the current running Fiber. 84 /// 85 static Fiber *currentFiber(); 86 /// Get a pointer to the primary Fiber. 87 /// This Fiber represents the thread of execution started by the OS, and 88 /// which has a Fiber attached to it after the fact. 89 static Fiber *primaryFiber(); 90 91 protected: 92 /// This method is called when this fiber is first run. Override it to 93 /// give your fiber something to do. When main returns, the fiber will 94 /// mark itself as finished and switch to its link fiber. 95 virtual void main() = 0; 96 97 void setStarted() { started = true; } 98 99 private: 100 static void entryTrampoline(); 101 void start(); 102 103 ucontext_t ctx; 104 Fiber *link; 105 106 // The stack for this context, or a nullptr if allocated elsewhere. 107 uint8_t *stack; 108 size_t stackSize; 109 110 bool started; 111 bool _finished; 112 void createContext(); 113}; 114 115#endif // __BASE_FIBER_HH__ 116