一个非常简单，但是实用的协程实现，使用Windows的*Fiber函数族（linux可以稍微改一下用*context函数族）。

fco.h

#ifndef _MSC_VER
#error "this fast coroutine library only supports MSVC building chain"
#endif#include <Windows.h>
#include <cstdint>
#include <map>namespace fco {
static constexpr int ERR_NOT_EXIST_CO = -1;enum Status {READY,  // Set up to READY when fco::newco() calledAWAIT,  // Set up to AWAIT when fco::yield() called
};struct Scheduler;
struct Coroutine;struct Coroutine {void (*task)(Scheduler*, void*);void* userData;char status;LPVOID winFiber;
};struct Scheduler {std::map<int, Coroutine*> coroutines;int currentIdx;LPVOID main;
};void __stdcall __entry(LPVOID lpParameter);Scheduler* initialize();void destroy(Scheduler* s);int newco(Scheduler* scheduler, void (*task)(Scheduler*, void*),void* userData);void resume(Scheduler* s, int coid);void yield(Scheduler* scheduler);int current(Scheduler* scheduler);}  // namespace fco

fco.cpp

#include "fco.h"// Initialize fco library, return a global scheduler
fco::Scheduler* fco::initialize() {Scheduler* sched = new Scheduler;sched->currentIdx = ERR_NOT_EXIST_CO;sched->main = ConvertThreadToFiber(NULL);return sched;
}// Release all resources
void fco::destroy(Scheduler* s) {for (auto& c : s->coroutines) {DeleteFiber(c.second->winFiber);}delete s;
}// This is should NEVER BE called on user land
void __stdcall fco::__entry(LPVOID lpParameter) {// Execute the task of current coroutineScheduler* s = (Scheduler*)lpParameter;Coroutine* currentCo = s->coroutines[s->currentIdx];(currentCo->task)(s, currentCo->userData);// Clean up executed tasks->coroutines.erase(s->coroutines.find(s->currentIdx));s->currentIdx = ERR_NOT_EXIST_CO;currentCo->status = Status::READY;DeleteFiber(currentCo->winFiber);delete currentCo;// Switch to entry functionSwitchToFiber(s->main);
}// Create new coroutine and return an unique identity
int fco::newco(Scheduler* scheduler, void (*task)(fco::Scheduler*, void*),void* userData) {Coroutine* co = new Coroutine;co->task = task;co->userData = userData;co->winFiber = CreateFiber(0, __entry, scheduler);if (co->winFiber == NULL) {return ERR_NOT_EXIST_CO;}co->status = Status::READY;int newCoId =scheduler->coroutines.size() != 0? scheduler->coroutines.end().operator--().operator*().first + 1: 0;scheduler->coroutines.insert(std::make_pair(newCoId, co));return newCoId;
}// Resume suspended coroutine by given coid
void fco::resume(fco::Scheduler* scheduler, int coid) {if (coid < 0) {return;}Coroutine* co = scheduler->coroutines[coid];if (co->status == Status::READY || co->status == Status::AWAIT) {scheduler->currentIdx = coid;scheduler->coroutines[scheduler->currentIdx]->status = Status::AWAIT;co->status = Status::READY;SwitchToFiber(co->winFiber);}
}// Yield CPU time to main coroutine
void fco::yield(fco::Scheduler* scheduler) {Coroutine* co = scheduler->coroutines[scheduler->currentIdx];co->status = Status::AWAIT;scheduler->currentIdx = ERR_NOT_EXIST_CO;SwitchToFiber(scheduler->main);
}// Get current running coroutine identity
int fco::current(Scheduler* scheduler) { return scheduler->currentIdx; }

example

• hello world

#include <cstdlib>
#include <ctime>
#include <iostream>
#include <vector>
#include "fco.h"void bar(fco::Scheduler* s, void* param) {for (int i = 0; i < 5; i++) {std::cout << "world\n";fco::yield(s);}
}int main() {fco::Scheduler* s = fco::initialize();int barFunc = fco::newco(s, bar, nullptr);for (int i = 0; i < 5; i++) {std::cout << "hello\n";fco::resume(s, barFunc);}fco::destroy(s);return 0;
}

• 生产者消费者模型

#include <cstdlib>
#include <ctime>
#include <iostream>
#include <vector>
#include "fco.h"std::vector<int> vec;void producer(fco::Scheduler* s, void* param) {while (vec.size() < 10) {int resource = rand();std::cout << "Producing " << resource << "\n";vec.push_back(resource);}fco::resume(s, (int)param);fco::yield(s);
}void consumer(fco::Scheduler* s, void* param) {int producerCo = fco::newco(s, producer, (void*)fco::current(s));while (true) {while (!vec.empty()) {int resource = vec.back();vec.pop_back();std::cout << "Consuming " << resource << "\n";}fco::resume(s, producerCo);}
}void factory() {fco::Scheduler* s = fco::initialize();int consumerCo = fco::newco(s, consumer, nullptr);fco::resume(s, consumerCo);fco::destroy(s);
}int main() {srand((int)time(0));factory();system("pause");return 0;
}