
// fakepoll.h
// poll using select
// Warning: a call to this poll() takes about 4K of stack space.

// Greg Parker     gparker-web@sealiesoftware.com     December 2000
// This code is in the public domain and may be copied or modified without
// permission.

// Updated May 2002:
// * fix crash when an fd is less than 0
// * set errno=EINVAL if an fd is greater or equal to FD_SETSIZE
// * don't set POLLIN or POLLOUT in revents if it wasn't requested
//   in events (only happens when an fd is in the poll set twice)

#ifndef _FAKE_POLL_H
#define _FAKE_POLL_H

#include <limits.h>
#include <sys/types.h>
#include <sys/time.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>

typedef struct pollfd {
	int fd;                         /* file desc to poll */
	short events;                   /* events of interest on fd */
	short revents;                  /* events that occurred on fd */
} pollfd_t;


// poll flags
#define POLLIN  0x0001
#define POLLOUT 0x0004
#define POLLERR 0x0008

// synonyms
#define POLLNORM POLLIN
#define POLLPRI POLLIN
#define POLLRDNORM POLLIN
#define POLLRDBAND POLLIN
#define POLLWRNORM POLLOUT
#define POLLWRBAND POLLOUT

// ignored
#define POLLHUP 0x0010
#define POLLNVAL 0x0020

static inline 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 < 0) {
				// Negative fd always reports zero
			} else {
				if ((p->events & POLLIN)  &&  FD_ISSET (p->fd, readp)) {
					p->revents |= POLLIN;
				}
				if ((p->events & POLLOUT)  &&  FD_ISSET (p->fd, writep)) {
					p->revents |= POLLOUT;
				}
				if ((p->events != 0)  &&  FD_ISSET (p->fd, exceptp)) {
					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;
}

#endif
