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Diffstat (limited to 'components/libc/posix/src/select.c')
| -rw-r--r-- | components/libc/posix/src/select.c | 180 |
1 files changed, 180 insertions, 0 deletions
diff --git a/components/libc/posix/src/select.c b/components/libc/posix/src/select.c new file mode 100644 index 0000000000..25cda0f0d1 --- /dev/null +++ b/components/libc/posix/src/select.c @@ -0,0 +1,180 @@ +/* + * Copyright (c) 2006-2021, RT-Thread Development Team + * + * SPDX-License-Identifier: Apache-2.0 + * + * Change Logs: + * Date Author Notes + * 2016-12-28 Bernard first version + */ +#include <rtthread.h> +#include <poll.h> +#include <sys/select.h> + +#ifdef RT_USING_POSIX + +static void fdszero(fd_set *set, int nfds) +{ + fd_mask *m; + int n; + + /* + The 'sizeof(fd_set)' of the system space may differ from user space, + so the actual size of the 'fd_set' is determined here with the parameter 'nfds' + */ + m = (fd_mask *)set; + for (n = 0; n < nfds; n += (sizeof(fd_mask) * 8)) + { + rt_memset(m, 0, sizeof(fd_mask)); + m ++; + } +} + +int select(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, struct timeval *timeout) +{ + int fd; + int npfds; + int msec; + int ndx; + int ret; + struct pollfd *pollset = RT_NULL; + + /* How many pollfd structures do we need to allocate? */ + for (fd = 0, npfds = 0; fd < nfds; fd++) + { + /* Check if any monitor operation is requested on this fd */ + if ((readfds && FD_ISSET(fd, readfds)) || + (writefds && FD_ISSET(fd, writefds)) || + (exceptfds && FD_ISSET(fd, exceptfds))) + { + npfds++; + } + } + + /* Allocate the descriptor list for poll() */ + if (npfds > 0) + { + pollset = (struct pollfd *)rt_calloc(npfds, sizeof(struct pollfd)); + if (!pollset) + { + return -1; + } + } + + /* Initialize the descriptor list for poll() */ + for (fd = 0, ndx = 0; fd < nfds; fd++) + { + int incr = 0; + + /* The readfs set holds the set of FDs that the caller can be assured + * of reading from without blocking. Note that POLLHUP is included as + * a read-able condition. POLLHUP will be reported at the end-of-file + * or when a connection is lost. In either case, the read() can then + * be performed without blocking. + */ + + if (readfds && FD_ISSET(fd, readfds)) + { + pollset[ndx].fd = fd; + pollset[ndx].events |= POLLIN; + incr = 1; + } + + if (writefds && FD_ISSET(fd, writefds)) + { + pollset[ndx].fd = fd; + pollset[ndx].events |= POLLOUT; + incr = 1; + } + + if (exceptfds && FD_ISSET(fd, exceptfds)) + { + pollset[ndx].fd = fd; + incr = 1; + } + + ndx += incr; + } + + RT_ASSERT(ndx == npfds); + + /* Convert the timeout to milliseconds */ + if (timeout) + { + msec = timeout->tv_sec * 1000 + timeout->tv_usec / 1000; + } + else + { + msec = -1; + } + + /* Then let poll do all of the real work. */ + + ret = poll(pollset, npfds, msec); + + /* Now set up the return values */ + if (readfds) + { + fdszero(readfds, nfds); + } + + if (writefds) + { + fdszero(writefds, nfds); + } + + if (exceptfds) + { + fdszero(exceptfds, nfds); + } + + /* Convert the poll descriptor list back into selects 3 bitsets */ + + if (ret > 0) + { + ret = 0; + for (ndx = 0; ndx < npfds; ndx++) + { + /* Check for read conditions. Note that POLLHUP is included as a + * read condition. POLLHUP will be reported when no more data will + * be available (such as when a connection is lost). In either + * case, the read() can then be performed without blocking. + */ + + if (readfds) + { + if (pollset[ndx].revents & (POLLIN | POLLHUP)) + { + FD_SET(pollset[ndx].fd, readfds); + ret++; + } + } + + /* Check for write conditions */ + if (writefds) + { + if (pollset[ndx].revents & POLLOUT) + { + FD_SET(pollset[ndx].fd, writefds); + ret++; + } + } + + /* Check for exceptions */ + if (exceptfds) + { + if (pollset[ndx].revents & POLLERR) + { + FD_SET(pollset[ndx].fd, exceptfds); + ret++; + } + } + } + } + + if (pollset) rt_free(pollset); + + return ret; +} + +#endif |