126 lines
3.3 KiB
C++
126 lines
3.3 KiB
C++
// ------------------------------------------------------------------------
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// kvu_fd_io.cpp: Helper functions for reading from, writing to and
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// waiting on UNIX file descriptors.
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//
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// Copyright (C) 2002 Kai Vehmanen
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//
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// This program is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 2 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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// ------------------------------------------------------------------------
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#include <unistd.h> /* POSIX: read()/write() */
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#include <sys/poll.h> /* XPG4-UNIX: poll() */
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#include "kvu_fd_io.h"
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/**
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* Attempts to read up to 'count' bytes from file descriptor 'fd'
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* into the buffer starting at 'buf'. If no data is available
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* for reading, up to 'timeout' milliseconds will be waited.
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* A negative value means infinite timeout.
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*/
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ssize_t kvu_fd_read(int fd, void *buf, size_t count, int timeout)
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{
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int nfds = 1;
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struct pollfd ufds;
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ssize_t rescount = 0;
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ufds.fd = fd;
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ufds.events = POLLIN | POLLPRI;
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ufds.revents = 0;
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int ret = poll(&ufds, nfds, timeout);
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if (ret > 0) {
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if (ufds.revents & POLLIN ||
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ufds.revents & POLLPRI) {
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rescount = ::read(fd, buf, count);
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}
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}
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else if (ret == 0) {
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/* timeout */
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rescount = -1;
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}
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return(rescount);
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}
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/**
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* Attempts to write up to 'count' bytes to file descriptor 'fd'
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* from the buffer starting at 'buf'. If no space is available
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* for writing, up to 'timeout' milliseconds will be waited.
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* A negative value means infinite timeout.
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*/
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ssize_t kvu_fd_write(int fd, const void *buf, size_t count, int timeout)
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{
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int nfds = 1;
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struct pollfd ufds;
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ssize_t rescount = 0;
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ufds.fd = fd;
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ufds.events = POLLOUT;
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ufds.revents = 0;
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int ret = poll(&ufds, nfds, timeout);
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if (ret > 0) {
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if (ufds.revents & POLLOUT) {
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rescount = ::write(fd, buf, count);
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}
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}
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else if (ret == 0) {
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/* timeout */
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rescount = -1;
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}
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return(rescount);
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}
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/**
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* Blocks until state of file descriptor 'fd'
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* changes. State changes include 'fd' becoming
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* readable, writing or an error condition.
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* A maximum of 'timeout' milliseconds will be
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* waited. A negative value means infinite timeout.
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*
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* @return returns 1 for success, 0 for timeout
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* and -1 on error
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*/
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int kvu_fd_wait(int fd, int timeout)
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{
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int nfds = 1;
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struct pollfd ufds;
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ufds.fd = fd;
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ufds.events = POLLIN | POLLPRI | POLLOUT;
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ufds.revents = 0;
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int ret = poll(&ufds, nfds, timeout);
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if (ret > 0) {
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if (ufds.revents & POLLERR ||
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ufds.revents & POLLHUP ||
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ufds.revents & POLLNVAL) {
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/* error */
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return(-1);
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}
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else {
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/* success */
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return(1);
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}
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}
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else if (ret == 0) {
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/* timeout */
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return(0);
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}
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/* error */
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return(-1);
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}
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