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