On Wed, Jan 8, 2014 at 10:33 PM, Fedor Indutny <[email protected]> wrote:
> Hey people!
>
> I'm currently trying to work around problem with receiving fds over
> IPC pipe on SmartOS. The thing is that SmartOS may concatenate
> multiple fds and emit them at once in a single SCM_RIGHTS message.
>
> I decided to queue them up on a stream instance, but notifying users
> about pending fds requires an API change. Initially, I thought about
> passing NULL-buffer as a `read2_cb` with zero `nread`, when there's
> pending fd (see:
> https://github.com/joyent/libuv/pull/1056/files#diff-56343bd7ad8bf449c2693082fb3e4081R379
> ). But we are afraid that many users are not prepared for such
> circumstances, and, considering that this situation is quite rare and
> platform-specific, users may not ever observe it, when developing
> their apps.
>
> Thus, I want to collect some feedback from you, people! Please let me
> know if it'll break existing code for you, or if you have any better
> ideas for this!
>
> Cheers,
> Fedor.
Here is a suggestion: make it explicit in the API. How about changing
the prototype of uv_read2_cb from:
void (*)(uv_pipe_t* pipe, ssize_t nread, const uv_buf_t* buf,
uv_handle_type type);
To something like:
void (*)(uv_pipe_t* pipe, ssize_t nread, const uv_buf_t* buf,
unsigned npending);
And then have the user execute the following code:
for (i = 0; i < npending; i++) {
uv_handle_type type = uv_pipe_pending_handle_type(pipe);
if (type == UV_TCP) {
uv_tcp_t* tcp_handle = /* ... */;
uv_tcp_init(pipe->loop, tcp_handle);
uv_accept((uv_stream_t*) pipe, tcp_handle);
} else if (type == UV_PIPE) {
// etc.
}
}
Maybe shuffle the uv_read2_cb parameters around so that code still
using the old function prototype will fail to build. Not everyone
compiles with -Wall -Wextra or pays attention to the warnings it
generates.
You could even drop the uv_read2_cb prototype altogether, replace it
with uv_read_cb and have the user call uv_pipe_pending_handles_count()
from his callback.
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