mirror of
https://github.com/zeromq/libzmq.git
synced 2024-12-28 07:58:14 +08:00
203 lines
7.8 KiB
Markdown
203 lines
7.8 KiB
Markdown
# wepoll - epoll for windows
|
|
|
|
[![][ci status badge]][ci status link]
|
|
|
|
This library implements the [epoll][man epoll] API for Windows
|
|
applications. It is fast and scalable, and it closely resembles the API
|
|
and behavior of Linux' epoll.
|
|
|
|
## Rationale
|
|
|
|
Unlike Linux, OS X, and many other operating systems, Windows doesn't
|
|
have a good API for receiving socket state notifications. It only
|
|
supports the `select` and `WSAPoll` APIs, but they
|
|
[don't scale][select scale] and suffer from
|
|
[other issues][wsapoll broken].
|
|
|
|
Using I/O completion ports isn't always practical when software is
|
|
designed to be cross-platform. Wepoll offers an alternative that is
|
|
much closer to a drop-in replacement for software that was designed
|
|
to run on Linux.
|
|
|
|
## Features
|
|
|
|
* Can poll 100000s of sockets efficiently.
|
|
* Fully thread-safe.
|
|
* Multiple threads can poll the same epoll port.
|
|
* Sockets can be added to multiple epoll sets.
|
|
* All epoll events (`EPOLLIN`, `EPOLLOUT`, `EPOLLPRI`, `EPOLLRDHUP`)
|
|
are supported.
|
|
* Level-triggered and one-shot (`EPOLLONESTHOT`) modes are supported
|
|
* Trivial to embed: you need [only two files][dist].
|
|
|
|
## Limitations
|
|
|
|
* Only works with sockets.
|
|
* Edge-triggered (`EPOLLET`) mode isn't supported.
|
|
|
|
## How to use
|
|
|
|
The library is [distributed][dist] as a single source file
|
|
([wepoll.c][wepoll.c]) and a single header file ([wepoll.h][wepoll.h]).<br>
|
|
Compile the .c file as part of your project, and include the header wherever
|
|
needed.
|
|
|
|
## Compatibility
|
|
|
|
* Requires Windows Vista or higher.
|
|
* Can be compiled with recent versions of MSVC, Clang, and GCC.
|
|
|
|
## API
|
|
|
|
### General remarks
|
|
|
|
* The epoll port is a `HANDLE`, not a file descriptor.
|
|
* All functions set both `errno` and `GetLastError()` on failure.
|
|
* For more extensive documentation, see the [epoll(7) man page][man epoll],
|
|
and the per-function man pages that are linked below.
|
|
|
|
### epoll_create/epoll_create1
|
|
|
|
```c
|
|
HANDLE epoll_create(int size);
|
|
HANDLE epoll_create1(int flags);
|
|
```
|
|
|
|
* Create a new epoll instance (port).
|
|
* `size` is ignored but most be greater than zero.
|
|
* `flags` must be zero as there are no supported flags.
|
|
* Returns `NULL` on failure.
|
|
* [Linux man page][man epoll_create]
|
|
|
|
### epoll_close
|
|
|
|
```c
|
|
int epoll_close(HANDLE ephnd);
|
|
```
|
|
|
|
* Close an epoll port.
|
|
* Do not attempt to close the epoll port with `close()`,
|
|
`CloseHandle()` or `closesocket()`.
|
|
|
|
### epoll_ctl
|
|
|
|
```c
|
|
int epoll_ctl(HANDLE ephnd,
|
|
int op,
|
|
SOCKET sock,
|
|
struct epoll_event* event);
|
|
```
|
|
|
|
* Control which socket events are monitored by an epoll port.
|
|
* `ephnd` must be a HANDLE created by
|
|
[`epoll_create()`](#epoll_createepoll_create1) or
|
|
[`epoll_create1()`](#epoll_createepoll_create1).
|
|
* `op` must be one of `EPOLL_CTL_ADD`, `EPOLL_CTL_MOD`, `EPOLL_CTL_DEL`.
|
|
* `sock` must be a valid socket created by [`socket()`][msdn socket],
|
|
[`WSASocket()`][msdn wsasocket], or [`accept()`][msdn accept].
|
|
* `event` should be a pointer to a [`struct epoll_event`](#struct-epoll_event).<br>
|
|
If `op` is `EPOLL_CTL_DEL` then the `event` parameter is ignored, and it
|
|
may be `NULL`.
|
|
* Returns 0 on success, -1 on failure.
|
|
* It is recommended to always explicitly remove a socket from its epoll
|
|
set using `EPOLL_CTL_DEL` *before* closing it.<br>
|
|
As on Linux, closed sockets are automatically removed from the epoll set, but
|
|
wepoll may not be able to detect that a socket was closed until the next call
|
|
to [`epoll_wait()`](#epoll_wait).
|
|
* [Linux man page][man epoll_ctl]
|
|
|
|
### epoll_wait
|
|
|
|
```c
|
|
int epoll_wait(HANDLE ephnd,
|
|
struct epoll_event* events,
|
|
int maxevents,
|
|
int timeout);
|
|
```
|
|
|
|
* Receive socket events from an epoll port.
|
|
* `events` should point to a caller-allocated array of
|
|
[`epoll_event`](#struct-epoll_event) structs, which will receive the
|
|
reported events.
|
|
* `maxevents` is the maximum number of events that will be written to the
|
|
`events` array, and must be greater than zero.
|
|
* `timeout` specifies whether to block when no events are immediately available.
|
|
- `<0` block indefinitely
|
|
- `0` report any events that are already waiting, but don't block
|
|
- `≥1` block for at most N milliseconds
|
|
* Return value:
|
|
- `-1` an error occurred
|
|
- `0` timed out without any events to report
|
|
- `≥1` the number of events stored in the `events` buffer
|
|
* [Linux man page][man epoll_wait]
|
|
|
|
### struct epoll_event
|
|
|
|
```c
|
|
typedef union epoll_data {
|
|
void* ptr;
|
|
int fd;
|
|
uint32_t u32;
|
|
uint64_t u64;
|
|
SOCKET sock; /* Windows specific */
|
|
HANDLE hnd; /* Windows specific */
|
|
} epoll_data_t;
|
|
```
|
|
|
|
```c
|
|
struct epoll_event {
|
|
uint32_t events; /* Epoll events and flags */
|
|
epoll_data_t data; /* User data variable */
|
|
};
|
|
```
|
|
|
|
* The `events` field is a bit mask containing the events being
|
|
monitored/reported, and optional flags.<br>
|
|
Flags are accepted by [`epoll_ctl()`](#epoll_ctl), but they are not reported
|
|
back by [`epoll_wait()`](#epoll_wait).
|
|
* The `data` field can be used to associate application-specific information
|
|
with a socket; its value will be returned unmodified by
|
|
[`epoll_wait()`](#epoll_wait).
|
|
* [Linux man page][man epoll_ctl]
|
|
|
|
| Event | Description |
|
|
|---------------|----------------------------------------------------------------------|
|
|
| `EPOLLIN` | incoming data available, or incoming connection ready to be accepted |
|
|
| `EPOLLOUT` | ready to send data, or outgoing connection successfully established |
|
|
| `EPOLLRDHUP` | remote peer initiated graceful socket shutdown |
|
|
| `EPOLLPRI` | out-of-band data available for reading |
|
|
| `EPOLLERR` | socket error<sup>1</sup> |
|
|
| `EPOLLHUP` | socket hang-up<sup>1</sup> |
|
|
| `EPOLLRDNORM` | same as `EPOLLIN` |
|
|
| `EPOLLRDBAND` | same as `EPOLLPRI` |
|
|
| `EPOLLWRNORM` | same as `EPOLLOUT` |
|
|
| `EPOLLWRBAND` | same as `EPOLLOUT` |
|
|
| `EPOLLMSG` | never reported |
|
|
|
|
| Flag | Description |
|
|
|------------------|---------------------------|
|
|
| `EPOLLONESHOT` | report event(s) only once |
|
|
| `EPOLLET` | not supported by wepoll |
|
|
| `EPOLLEXCLUSIVE` | not supported by wepoll |
|
|
| `EPOLLWAKEUP` | not supported by wepoll |
|
|
|
|
<sup>1</sup>: the `EPOLLERR` and `EPOLLHUP` events may always be reported by
|
|
[`epoll_wait()`](#epoll_wait), regardless of the event mask that was passed to
|
|
[`epoll_ctl()`](#epoll_ctl).
|
|
|
|
|
|
[ci status badge]: https://ci.appveyor.com/api/projects/status/github/piscisaureus/wepoll?branch=master&svg=true
|
|
[ci status link]: https://ci.appveyor.com/project/piscisaureus/wepoll/branch/master
|
|
[dist]: https://github.com/piscisaureus/wepoll/tree/dist
|
|
[man epoll]: http://man7.org/linux/man-pages/man7/epoll.7.html
|
|
[man epoll_create]: http://man7.org/linux/man-pages/man2/epoll_create.2.html
|
|
[man epoll_ctl]: http://man7.org/linux/man-pages/man2/epoll_ctl.2.html
|
|
[man epoll_wait]: http://man7.org/linux/man-pages/man2/epoll_wait.2.html
|
|
[msdn accept]: https://msdn.microsoft.com/en-us/library/windows/desktop/ms737526(v=vs.85).aspx
|
|
[msdn socket]: https://msdn.microsoft.com/en-us/library/windows/desktop/ms740506(v=vs.85).aspx
|
|
[msdn wsasocket]: https://msdn.microsoft.com/en-us/library/windows/desktop/ms742212(v=vs.85).aspx
|
|
[select scale]: https://daniel.haxx.se/docs/poll-vs-select.html
|
|
[wsapoll broken]: https://daniel.haxx.se/blog/2012/10/10/wsapoll-is-broken/
|
|
[wepoll.c]: https://github.com/piscisaureus/wepoll/blob/dist/wepoll.c
|
|
[wepoll.h]: https://github.com/piscisaureus/wepoll/blob/dist/wepoll.h
|