1.實現機制
1.1. switch-case
Protothread
最輕，但受限最大
1.2. setjmp/longjmp
StateThread採用這種方式
1.3. ucontext
1.4. boost::context
針對不同的arch用匯編實現的
http://www.boost.org/doc/libs/1_59_0/libs/context/doc/html/index.html
2.C的coroutine庫
Cgreenlet
coroutine
boost.coroutine
Protothreads
orchid
Statethread
Libco
coroutine_event
libconcurrency
setjmp-longjmp-ucontext-snippets
libcilkrts
libgo
libtask
3.cgreenlet
https://github.com/geertj/cgreenlet
cross-platfrm coroutine library for C/C++
cgreenlet introduce
https://github.com/geertj/cgreenlet/blob/master/doc/intro.txt
4.coroutine
https://github.com/cloudwu/coroutine/
5.protothread
http://dunkels.com/adam/pt/
6.coroutine_event
coroutine_event –它基於libevent，提供了基於協程的併發模型
在libevent的基礎上提供同步的接口，在獲得異步效率的同時提供更方便的編程方式
https://github.com/colaghost/coroutine_event
7.orchid
https://github.com/ioriiod0/orchid
orchid是一個構建於boost庫基礎上的C++庫，爲用戶提供基於協程的併發模型
8.Libco
libco是一個有趣的協程基礎庫,僅有的幾個函數接口 co_create/co_resume/co_yield 再配合 co_poll，可以支持同步或者異步的寫法，如線程庫一樣輕鬆，庫裏面提供了socket族函數的hook，使得後臺邏輯服務幾乎不用修改邏輯代碼就可以完成異步化改造。
http://code.tencent.com/libco.html
https://code.csdn.net/Tencent/libco
9.Statethread
The State Threads Library is a small application library which provides a foundation for writing fast and highly scalable Internet applications (such as web servers, proxy servers, mail transfer agents, and so on, really any network-data-driven application) on UNIX-like platforms. It combines the simplicity of the multithreaded programming paradigm, in which one thread supports each simultaneous connection, with the performance and scalability of an event-driven state machine architecture. In other words, this library offers a threading API for structuring an Internet application as a state machine.
http://state-threads.sourceforge.net/
http://sourceforge.net/projects/state-threads/
10.libconcurrency
https://code.google.com/p/libconcurrency/
11.setjmp-longjmp-ucontext-snippets
https://github.com/danluu/setjmp-longjmp-ucontext-snippets
12.libtask
http://swtch.com/libtask/
