Yes, your understanding is correct.
Basically, there is an external function which pushes an object into a job
queue. And another separate process running which reads off the queue.
The code is already setup to use pipe(), write(), read() and libev but I am
working on switching it to use libuv. I've had some more success using
uv_poll_t and pipe(), write(), read() but it sounds like uv_async_t might
be a more elegant solution. I will give it a try, thank you for help!
On Wednesday, December 29, 2021 at 6:13:36 AM UTC-5 Ben Noordhuis wrote:
> On Tue, Dec 28, 2021 at 10:29 PM Emmanuel Schmidbauer
> <e.schm...@gmail.com> wrote:
> >
> > Hello,
> > I'm trying to integrate existing code that uses pipe() and write() into
> libuv
> > I've been hacking my way through it as I'm not a libuv expert. But i've
> come up with a solution that works but maybe not "correct". The "publish"
> is an existing function that writes data to the pipe, it gets called by an
> external command. I would really appreciate if anyone could help me out
> with a "better" or "correct" way to implement this, thanks in advance.
> >
> > here is a snippet of "working" code:
> >
> > int *worker_pipes_fds = NULL;
> > int *worker_pipes = NULL;
> > uv_loop_t *loop;
> > uv_pipe_t apipe;
> > static int publish()
> > {
> > char *payload = "Hello World";
> > write(worker_pipes[0], &payload, sizeof(payload));
> > }
> > void alloc_buffer(uv_handle_t *handle, size_t len, uv_buf_t *buf)
> > {
> > uv_os_fd_t fd;
> > char *payload = NULL;
> > if (uv_fileno(handle, &fd) < 0) {
> > printf("could not get fd: %d\n", fd);
> > return;
> > }
> > read(fd, &payload, sizeof(payload));
> > printf("%s \n", payload);
> > }
> >
> > void read_pipe(uv_stream_t *client, ssize_t nread, const uv_buf_t *buf)
> > {
> > // empty
> > }
> > int worker_proc(int fd)
> > {
> > loop = uv_default_loop();
> > uv_pipe_init(loop, &apipe, 0);
> > uv_pipe_open(&apipe, fd);
> > uv_read_start((uv_stream_t *)&apipe, alloc_buffer, read_pipe);
> > uv_run(loop, UV_RUN_DEFAULT);
> > return 1;
> > }
> >
> > int start()
> > {
> > worker_pipes_fds = (int *)malloc(sizeof(int) * 2);
> > worker_pipes = (int *)malloc(sizeof(int) * 1);
> > worker_pipes_fds[0] = worker_pipes_fds[1] = -1;
> > if(pipe(&worker_pipes_fds[0]) < 0) {
> > return -1;
> > }
> > worker_pipes[0] = worker_pipes_fds[1];
> > worker_proc(worker_pipes_fds[0]);
> > }
>
> Do I understand correctly the idea is to have some a queue-like
> mechanism that wakes up the event loop when new items are added?
>
> Idiomatic libuv code would use uv_async_t coupled with a (optionally
> uv_mutex_t protected) data structure. The sender adds the item and
> calls uv_async_send(), the receiver pops it off in the uv_async_cb
> callback.
>
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