异步 http 客户端库和 glib 事件循环

Question

A am looking for an asynchronous http client library with some specific need:

• It must be possible it implement it as a glibmm source
• It must be single threated
• It must have a lgpl, bsd, mit or similar license

In order to impement it as a glibmm source, one must have access to its file descriptor, create a Glib::PollFD object, and I should be good to go.

I have been looking at several libraries, which all have some problems:

• libcurl, can almost do what I want, in the multi source API it has a curl_multi_fdset function, which return fd_set's. The problem is that I can not figure out how I can convert a fd_set to one or more Glib::PollFD's
• Poco, has a HttpSessionClient which returns in istream, which I can not find a way to do unblocking read from.
• Boost::Asio require to use the io_service as event loop.

Can anyone overcome the problems I see with these tree libraries, or suggest alternative libraries?

Answer 1

Glib::PollFD::PollFD(int fd) is the constructor that you want. An fd_set is just a set of integer fds. The word "set" is used in the mathematical sense, ie no fd can occur more than once in a set, therefore they do not refer to it as an array or a list. An fd_set is just a fixed size buffer. Try it out by making an fd_set and adding some fds to it, then look at it in a debugger or just dump it out in hex.

This is a common patter in async programming where you need to join two async event loops. While you could poll two loops with a timeout, it is generally better to get the raw fds out of one event loop, and add them