src/lib/ioloop-select.c

/* Copyright (c) 2002-2018 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "ioloop-private.h"

#ifdef IOLOOP_SELECT

#ifdef HAVE_SYS_SELECT_H
#  include <sys/select.h> /* According to POSIX 1003.1-2001 */
#endif
#include <sys/time.h>
#include <unistd.h>

struct ioloop_handler_context {
    int highest_fd;
    fd_set read_fds, write_fds, except_fds;
    fd_set tmp_read_fds, tmp_write_fds, tmp_except_fds;
};

static void update_highest_fd(struct ioloop *ioloop)
{
    struct ioloop_handler_context *ctx = ioloop->handler_context;
        struct io_file *io;
    int max_highest_fd;

        max_highest_fd = ctx->highest_fd-1;
    ctx->highest_fd = -1;

    for (io = ioloop->io_files; io != NULL; io = io->next) {
        if (io->fd <= ctx->highest_fd)
            continue;

        ctx->highest_fd = io->fd;

        if (ctx->highest_fd == max_highest_fd)
            break;
    }
}

void io_loop_handler_init(struct ioloop *ioloop,
              unsigned int initial_fd_count ATTR_UNUSED)
{
    struct ioloop_handler_context *ctx;

    ioloop->handler_context = ctx = i_new(struct ioloop_handler_context, 1);
    ctx->highest_fd = -1;
        FD_ZERO(&ctx->read_fds);
    FD_ZERO(&ctx->write_fds);
    FD_ZERO(&ctx->except_fds);
}

void io_loop_handler_deinit(struct ioloop *ioloop)
{
        i_free(ioloop->handler_context);
}

void io_loop_handle_add(struct io_file *io)
{
    struct ioloop_handler_context *ctx = io->io.ioloop->handler_context;
    enum io_condition condition = io->io.condition;
    int fd = io->fd;

    i_assert(fd >= 0);

    if (fd >= FD_SETSIZE)
        i_fatal("fd %d too large for select()", fd);

        if ((condition & (IO_READ | IO_ERROR)) != 0)
        FD_SET(fd, &ctx->read_fds);
        if ((condition & IO_WRITE) != 0)
        FD_SET(fd, &ctx->write_fds);
    FD_SET(fd, &ctx->except_fds);

    if (io->fd > ctx->highest_fd)
        ctx->highest_fd = io->fd;
}

void io_loop_handle_remove(struct io_file *io, bool closed ATTR_UNUSED)
{
    struct ioloop_handler_context *ctx = io->io.ioloop->handler_context;
    enum io_condition condition = io->io.condition;
    int fd = io->fd;

    i_assert(fd >= 0 && fd < FD_SETSIZE);

    if ((condition & (IO_READ | IO_ERROR)) != 0)
        FD_CLR(fd, &ctx->read_fds);
        if ((condition & IO_WRITE) != 0)
        FD_CLR(fd, &ctx->write_fds);

    if (!FD_ISSET(fd, &ctx->read_fds) && !FD_ISSET(fd, &ctx->write_fds)) {
        FD_CLR(fd, &ctx->except_fds);

        /* check if we removed the highest fd */
        if (io->fd == ctx->highest_fd)
            update_highest_fd(io->io.ioloop);
    }
    i_free(io);
}

#define io_check_condition(ctx, fd, cond) \
    ((FD_ISSET((fd), &(ctx)->tmp_read_fds) && ((cond) & (IO_READ|IO_ERROR)) != 0) || \
     (FD_ISSET((fd), &(ctx)->tmp_write_fds) && ((cond) & IO_WRITE) != 0) || \
     (FD_ISSET((fd), &(ctx)->tmp_except_fds)))

void io_loop_handler_run_internal(struct ioloop *ioloop)
{
    struct ioloop_handler_context *ctx = ioloop->handler_context;
    struct timeval tv;
    struct io_file *io;
    int ret;

    /* get the time left for next timeout task */
    io_loop_get_wait_time(ioloop, &tv);

    memcpy(&ctx->tmp_read_fds, &ctx->read_fds, sizeof(fd_set));
    memcpy(&ctx->tmp_write_fds, &ctx->write_fds, sizeof(fd_set));
    memcpy(&ctx->tmp_except_fds, &ctx->except_fds, sizeof(fd_set));

    ret = select(ctx->highest_fd + 1, &ctx->tmp_read_fds,
             &ctx->tmp_write_fds, &ctx->tmp_except_fds, &tv);
    if (ret < 0 && errno != EINTR)
        i_warning("select() : %m");

    /* execute timeout handlers */
        io_loop_handle_timeouts(ioloop);

    if (ret <= 0 || !ioloop->running) {
                /* no I/O events */
        return;
    }

    io = ioloop->io_files;
    for (; io != NULL && ret > 0; io = ioloop->next_io_file) {
                ioloop->next_io_file = io->next;

        if (io_check_condition(ctx, io->fd, io->io.condition)) {
            ret--;
            io_loop_call_io(&io->io);
        }
    }
}

#endif