177 lines
4.2 KiB
C
177 lines
4.2 KiB
C
/*
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* Copyright (c) 2006-2021, RT-Thread Development Team
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Change Logs:
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* Date Author Notes
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* 2016-12-28 Bernard first version
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*/
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#include <rtthread.h>
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#include <poll.h>
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#include <sys/select.h>
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static void fdszero(fd_set *set, int nfds)
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{
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fd_mask *m;
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int n;
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/*
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The 'sizeof(fd_set)' of the system space may differ from user space,
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so the actual size of the 'fd_set' is determined here with the parameter 'nfds'
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*/
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m = (fd_mask *)set;
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for (n = 0; n < nfds; n += (sizeof(fd_mask) * 8))
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{
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rt_memset(m, 0, sizeof(fd_mask));
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m ++;
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}
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}
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int select(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, struct timeval *timeout)
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{
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int fd;
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int npfds;
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int msec;
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int ndx;
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int ret;
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struct pollfd *pollset = RT_NULL;
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/* How many pollfd structures do we need to allocate? */
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for (fd = 0, npfds = 0; fd < nfds; fd++)
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{
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/* Check if any monitor operation is requested on this fd */
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if ((readfds && FD_ISSET(fd, readfds)) ||
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(writefds && FD_ISSET(fd, writefds)) ||
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(exceptfds && FD_ISSET(fd, exceptfds)))
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{
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npfds++;
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}
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}
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/* Allocate the descriptor list for poll() */
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if (npfds > 0)
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{
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pollset = (struct pollfd *)rt_calloc(npfds, sizeof(struct pollfd));
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if (!pollset)
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{
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return -1;
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}
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}
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/* Initialize the descriptor list for poll() */
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for (fd = 0, ndx = 0; fd < nfds; fd++)
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{
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int incr = 0;
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/* The readfs set holds the set of FDs that the caller can be assured
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* of reading from without blocking. Note that POLLHUP is included as
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* a read-able condition. POLLHUP will be reported at the end-of-file
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* or when a connection is lost. In either case, the read() can then
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* be performed without blocking.
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*/
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if (readfds && FD_ISSET(fd, readfds))
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{
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pollset[ndx].fd = fd;
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pollset[ndx].events |= POLLIN;
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incr = 1;
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}
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if (writefds && FD_ISSET(fd, writefds))
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{
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pollset[ndx].fd = fd;
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pollset[ndx].events |= POLLOUT;
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incr = 1;
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}
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if (exceptfds && FD_ISSET(fd, exceptfds))
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{
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pollset[ndx].fd = fd;
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incr = 1;
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}
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ndx += incr;
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}
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RT_ASSERT(ndx == npfds);
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/* Convert the timeout to milliseconds */
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if (timeout)
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{
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msec = timeout->tv_sec * 1000 + timeout->tv_usec / 1000;
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}
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else
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{
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msec = -1;
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}
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/* Then let poll do all of the real work. */
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ret = poll(pollset, npfds, msec);
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/* Now set up the return values */
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if (readfds)
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{
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fdszero(readfds, nfds);
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}
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if (writefds)
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{
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fdszero(writefds, nfds);
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}
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if (exceptfds)
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{
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fdszero(exceptfds, nfds);
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}
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/* Convert the poll descriptor list back into selects 3 bitsets */
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if (ret > 0)
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{
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ret = 0;
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for (ndx = 0; ndx < npfds; ndx++)
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{
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/* Check for read conditions. Note that POLLHUP is included as a
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* read condition. POLLHUP will be reported when no more data will
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* be available (such as when a connection is lost). In either
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* case, the read() can then be performed without blocking.
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*/
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if (readfds)
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{
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if (pollset[ndx].revents & (POLLIN | POLLHUP))
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{
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FD_SET(pollset[ndx].fd, readfds);
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ret++;
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}
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}
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/* Check for write conditions */
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if (writefds)
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{
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if (pollset[ndx].revents & POLLOUT)
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{
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FD_SET(pollset[ndx].fd, writefds);
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ret++;
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}
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}
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/* Check for exceptions */
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if (exceptfds)
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{
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if (pollset[ndx].revents & POLLERR)
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{
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FD_SET(pollset[ndx].fd, exceptfds);
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ret++;
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}
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}
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}
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}
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if (pollset) rt_free(pollset);
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return ret;
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}
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