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Diffstat (limited to 'nuttx/fs/fs_select.c')
-rw-r--r-- | nuttx/fs/fs_select.c | 239 |
1 files changed, 239 insertions, 0 deletions
diff --git a/nuttx/fs/fs_select.c b/nuttx/fs/fs_select.c new file mode 100644 index 000000000..e40c5bc13 --- /dev/null +++ b/nuttx/fs/fs_select.c @@ -0,0 +1,239 @@ +/**************************************************************************** + * fs/fs_select.c + * + * Copyright (C) 2008-2009, 2012 Gregory Nutt. All rights reserved. + * Author: Gregory Nutt <gnutt@nuttx.org> + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in + * the documentation and/or other materials provided with the + * distribution. + * 3. Neither the name NuttX nor the names of its contributors may be + * used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS + * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE + * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, + * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS + * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED + * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN + * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + * + ****************************************************************************/ + +/**************************************************************************** + * Included Files + ****************************************************************************/ + +#include <nuttx/config.h> + +#include <sys/select.h> + +#include <string.h> +#include <poll.h> +#include <time.h> +#include <errno.h> +#include <assert.h> +#include <debug.h> + +#include <nuttx/kmalloc.h> +#include <nuttx/fs/fs.h> + +#include "fs_internal.h" + +#ifndef CONFIG_DISABLE_POLL + +/**************************************************************************** + * Pre-processor Definitions + ****************************************************************************/ + +/**************************************************************************** + * Private Functions + ****************************************************************************/ + +/**************************************************************************** + * Public Functions + ****************************************************************************/ + +/**************************************************************************** + * Name: select + * + * Description: + * select() allows a program to monitor multiple file descriptors, waiting + * until one or more of the file descriptors become "ready" for some class + * of I/O operation (e.g., input possible). A file descriptor is + * considered ready if it is possible to perform the corresponding I/O + * operation (e.g., read(2)) without blocking. + * + * NOTE: poll() is the fundamental API for performing such monitoring + * operation under NuttX. select() is provided for compatibility and + * is simply a layer of added logic on top of poll(). As such, select() + * is more wasteful of resources and poll() is the recommended API to be + * used. + * + * Input parameters: + * nfds - the maximum fd number (+1) of any descriptor in any of the + * three sets. + * readfds - the set of descriptions to monitor for read-ready events + * writefds - the set of descriptions to monitor for write-ready events + * exceptfds - the set of descriptions to monitor for error events + * timeout - Return at this time if none of these events of interest + * occur. + * + * Return: + * 0: Timer expired + * >0: The number of bits set in the three sets of descriptors + * -1: An error occurred (errno will be set appropriately) + * + ****************************************************************************/ + +int select(int nfds, FAR fd_set *readfds, FAR fd_set *writefds, + FAR fd_set *exceptfds, FAR struct timeval *timeout) +{ + struct pollfd *pollset; + int fd; + int npfds; + int msec; + int ndx; + int ret; + + /* Allocate the descriptor list for poll() */ + + pollset = (struct pollfd *)kzalloc(nfds * sizeof(struct pollfd)); + if (!pollset) + { + set_errno(ENOMEM); + return ERROR; + } + + /* Initialize the descriptor list for poll() */ + + for (fd = 0, npfds = 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[npfds].fd = fd; + pollset[npfds].events |= POLLIN; + incr = 1; + } + + /* The writefds set holds the set of FDs that the caller can be assured + * of writing to without blocking. + */ + + if (writefds && FD_ISSET(fd, writefds)) + { + pollset[npfds].fd = fd; + pollset[npfds].events |= POLLOUT; + incr = 1; + } + + /* The exceptfds set holds the set of FDs that are watched for exceptions */ + + if (exceptfds && FD_ISSET(fd, exceptfds)) + { + pollset[npfds].fd = fd; + incr = 1; + } + + npfds += incr; + } + + /* Convert the timeout to milliseconds */ + + msec = timeout->tv_sec * 1000 + timeout->tv_usec / 1000; + + /* Then let poll do all of the real work. */ + + ret = poll(pollset, npfds, msec); + + /* Now set up the return values */ + + if (readfds) + { + memset(readfds, 0, sizeof(fd_set)); + } + + if (writefds) + { + memset(writefds, 0, sizeof(fd_set)); + } + + if (exceptfds) + { + memset(exceptfds, 0, sizeof(fd_set)); + } + + /* 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++; + } + } + } + } + + kfree(pollset); + return ret; +} + +#endif /* CONFIG_DISABLE_POLL */ + |