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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
// fakepoll.h
// poll using select
// Warning: a call to this poll() takes about 4K of stack space.
// Greg Parker gparker@cs.stanford.edu December 2000
// This code is in the public domain and may be copied or modified without
// permission.
// Located at <http://www.sealiesoftware.com/fakepoll.h>.
#include "pal/palinternal.h"
#include "pal/fakepoll.h"
#include "pal/dbgmsg.h"
#include <errno.h>
#include <string.h>
#include <limits.h>
#include <sys/types.h>
#include <sys/time.h>
#include <unistd.h>
SET_DEFAULT_DEBUG_CHANNEL(POLL);
int poll(struct pollfd *pollSet, int pollCount, int pollTimeout)
{
struct timeval tv;
struct timeval *tvp;
fd_set readFDs, writeFDs, exceptFDs;
fd_set *readp, *writep, *exceptp;
struct pollfd *pollEnd, *p;
int selected;
int result;
int maxFD;
if (!pollSet) {
pollEnd = NULL;
readp = NULL;
writep = NULL;
exceptp = NULL;
maxFD = 0;
}
else {
pollEnd = pollSet + pollCount;
readp = &readFDs;
writep = &writeFDs;
exceptp = &exceptFDs;
FD_ZERO(readp);
FD_ZERO(writep);
FD_ZERO(exceptp);
// Find the biggest fd in the poll set
maxFD = 0;
for (p = pollSet; p < pollEnd; p++) {
if (p->fd > maxFD) maxFD = p->fd;
}
if (maxFD >= FD_SETSIZE) {
// At least one fd is too big
errno = EINVAL;
return -1;
}
// Transcribe flags from the poll set to the fd sets
for (p = pollSet; p < pollEnd; p++) {
if (p->fd < 0) {
// Negative fd checks nothing and always reports zero
} else {
if (p->events & POLLIN) FD_SET(p->fd, readp);
if (p->events & POLLOUT) FD_SET(p->fd, writep);
if (p->events != 0) FD_SET(p->fd, exceptp);
// POLLERR is never set coming in; poll() always reports errors.
// But don't report if we're not listening to anything at all.
}
}
}
// poll timeout is in milliseconds. Convert to struct timeval.
// poll timeout == -1 : wait forever : select timeout of NULL
// poll timeout == 0 : return immediately : select timeout of zero
if (pollTimeout >= 0) {
tv.tv_sec = pollTimeout / 1000;
tv.tv_usec = (pollTimeout % 1000) * 1000;
tvp = &tv;
} else {
tvp = NULL;
}
selected = select(maxFD+1, readp, writep, exceptp, tvp);
if (selected < 0) {
// Error during select
result = -1;
}
else if (selected > 0) {
// Select found something
// Transcribe result from fd sets to poll set.
// Also count the number of selected fds. poll returns the
// number of ready fds; select returns the number of bits set.
int polled = 0;
for (p = pollSet; p < pollEnd; p++) {
p->revents = 0;
if (p->fd > -1) {
// Check p->events before setting p->revents. If we
// have multiple pollfds with the same fd, we want to
// set the appropriate revents value for each pollfd.
if (FD_ISSET(p->fd, readp) && (p->events & POLLIN))
p->revents |= POLLIN;
if (FD_ISSET(p->fd, writep) && (p->events & POLLOUT))
p->revents |= POLLOUT;
if (FD_ISSET(p->fd, exceptp) && (p->events != 0))
p->revents |= POLLERR;
if (p->revents) polled++;
}
}
result = polled;
}
else {
// selected == 0, select timed out before anything happened
// Clear all result bits and return zero.
for (p = pollSet; p < pollEnd; p++) {
p->revents = 0;
}
result = 0;
}
return result;
}
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