Io

io: async IO library based on event loop

Description: Async IO library which is based on IO read/write requests, which can be submitted to the IO queue and if file descriptor (socket, pipe, whatever) is ready to perform read/write - completion will be called.

E.g. reads/writes from socket can be done as following:

    struct io_queue q;
    struct io_req req;
    void *poller;
    int err;

    io_queue_init(&q);

    /* Create event loop poller */
    err = poller_create(&poller);
    assert(err == 0);

    /* Bind queue with one side of the socket */
    err = io_queue_bind(&q, poller, sock);
    assert(err == 0);

    /* Init read request, in case of completion on_read() will be called */
    io_req_init(&req, &q, REQ_RD, NULL, on_read);
    req.buf = (struct io_buf){
        .iov[0] = {
            .iov_base = NULL, /* buffer should be allocated */
            .iov_len  = 10    /* want to read 10 bytes */
        },
        .iov_num  = 1,        /* we have only one buffer */
        .is_vari_len = false  /* read exactly what is told, i.e. 10 bytes */
    };

    /* Submit request, i.e. put it to the submission list */
    err = io_queue_submit(&req);
    assert(err == 0);

    while (1) {
        struct poller_item *items[16];
        int i;

        err = poller_wait(poller, items, ARRAY_SIZE(items), INT_MAX);
        if (err == 0)
             continue;
        else if (err < 0) {
             printf("poller_wait() failed, errno=%d\n", -err);
             break;
        }

        /* Handle events */
        for (i = 0; i < err; i++) {
            err = poller_do_action(poller, items[i]);
            if (err)
                /* We are done. */
                break;
        }
    }

    io_req_deinit(&req);
    io_queue_unbind(&q);
    poller_destroy(poller);


Exactly using the same pattern all other types of file descriptors can
be used.  See io-test.c for details, where signalfd is shown as example.

The nice thing about this is that any other protocol can be implemented
as a stack, e.g. zmtp-test.c accepts ZMTP (ZeroMQ) REQ sockets.

Why? o No threads. o No C++, no Java. o Plain C. o Single point of wait and control. o Event driven.

Howto: $ make

then

$ ./io-test

or

$ ./zmtp-test

Author: Roman Pen r.peniaev@gmail.com