116 lines
3.3 KiB
Markdown
116 lines
3.3 KiB
Markdown
# wepoll - epoll for windows
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This library implements the
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[epoll](http://man7.org/linux/man-pages/man7/epoll.7.html) API for
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Windows applications. It attempts to be efficient, and to match the
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Linux API and as closely as possible.
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## Rationale
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Unlike Linux, OS X, and many other operating systems, Windows doesn't
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have a good API for receiving socket state notifications. It only
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supports the `select` and `WSAPoll` APIs, but they
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[don't scale](https://daniel.haxx.se/docs/poll-vs-select.html)
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and suffer from
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[other issues](https://daniel.haxx.se/blog/2012/10/10/wsapoll-is-broken/).
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Using I/O completion ports isn't always practical when software is
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designed to be cross-platform. Wepoll offers an alternative that is
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much closer to a drop-in replacement for software that was designed
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to run on Linux.
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## Features
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* can poll 100000s of sockets efficiently
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* fully thread safe
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* multiple threads can poll the same epoll port
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* sockets can be added to multiple epoll sets
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* polling for `EPOLLIN`, `EPOLLOUT`, `EPOLLPRI`, `EPOLLRDHUP`,
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`EPOLLHUP`, and `EPOLLERR` events
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* `EPOLLONESTHOT` flag
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## Limitations
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* only works with sockets
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* some modes not suported: `EPOLLET`, `EPOLLEXCLUSIVE`
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## How to use
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The library is distributed as a single source file (wepoll.c) and a
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single header file (wepoll.h). Compile the .c file as part of your
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project, and include the header wherever needed.
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## Compatibility
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* Requires Windows 7 or higher.
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* Can be compiled with recent versions of MSVC and Clang.
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* GCC (mingw) should work (but is untested).
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## API notes
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### General
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* The epoll port is a `HANDLE`, not a file descriptor.
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* All functions set both `errno` and `GetLastError()` on failure.
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### epoll_create/epoll_create1
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```c
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HANDLE epoll_create(int size);
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HANDLE epoll_create1(int flags);
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```
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* Create a new epoll instance (port).
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* `size` is ignored but most be greater than zero.
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* `flags` must be zero as there are no supported flags.
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* Returns `INVALID_HANDLE_VALUE` on failure.
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* [man page](http://man7.org/linux/man-pages/man2/epoll_create.2.html)
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### epoll_close
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```c
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int epoll_close(HANDLE ephnd);
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```
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* Close an epoll port.
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* Do not attempt to close the epoll port with `close()`,
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`CloseHandle()` or `closesocket()`.
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### epoll_ctl
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```c
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int epoll_ctl(HANDLE ephnd,
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int op,
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SOCKET sock,
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struct epoll_event* event);
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```
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* Control which socket events are monitored by an epoll port.
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* `ephnd` must be a HANDLE created by `epoll_create` or `epoll_create1`.
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* `op` must be one of `EPOLL_CTL_ADD`, `EPOLL_CTL_MOD`, `EPOLL_CTL_DEL`.
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* It is recommended to always explicitly remove a socket from its epoll
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set using `EPOLL_CTL_MOD` *before* closing it. As on Linux, sockets
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are automatically removed from the epoll set when they are closed, but
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wepoll may not be able to detect this until the next call to
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`epoll_wait()`.
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* TODO: expand
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* [man page](http://man7.org/linux/man-pages/man2/epoll_ctl.2.html)
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### epoll_wait
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```c
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int epoll_wait(HANDLE ephnd,
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struct epoll_event* events,
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int maxevents,
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int timeout);
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```
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* Receive socket events from an epoll port.
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* Returns
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- -1 on failure
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- 0 when a timeout occurs
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- ≥1 the number of evens received
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* TODO: expand
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* [man page](http://man7.org/linux/man-pages/man2/epoll_wait.2.html)
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