/*
 * Copyright (c) 1996 Gunther Schadow.  All rights reserved.
 *
 * 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#pragma implementation
#include "FdSet.h"
#include <sys/time.h>
#include <unistd.h>
#include <stdarg.h>

/*
  It is likely that other systems than BSD declare fd_set slightly
  differently causing some headache when this is ported. For your
  reference here are the BSD declarations from <sys/types.h>:
  
> #ifndef _POSIX_SOURCE
> #define NBBY	8		// number of bits in a byte
> 
> 
> // Select uses bit masks of file descriptors in longs.  These macros
> // manipulate such bit fields (the filesystem macros use chars).
> // FD_SETSIZE may be defined by the user, but the default here should
> // be enough for most uses.
>
> #ifndef FD_SETSIZE
> #define FD_SETSIZE	256
> #endif
> 
> typedef long	fd_mask;
> #define NFDBITS (sizeof(fd_mask) * NBBY)	// bits per mask
> 
> #ifndef howmany
> #define howmany(x, y) (((x)+((y)-1))/(y))
> #endif
>
> typedef struct fd_set {
>   fd_mask fds_bits[howmany(FD_SETSIZE, NFDBITS)];
> } fd_set;
>
> #define FD_SET(n, p) ((p)->fds_bits[(n)/NFDBITS] |= (1 << ((n) % NFDBITS)))
> #define FD_CLR(n, p) ((p)->fds_bits[(n)/NFDBITS] &= ~(1 << ((n) % NFDBITS)))
> #define FD_ISSET(n, p) ((p)->fds_bits[(n)/NFDBITS] & (1 << ((n) % NFDBITS)))
> #define FD_ZERO(p) bzero((char *)(p), sizeof(*(p)))
*/

// loosen the dependency (a good place for `#ifdef's!)
const int bps = FD_SETSIZE;        // bits per set
const int bpm = NFDBITS;           // bits per mask
const int mps = howmany(bps, bpm); // masks per set

int FdSet::next(int n) const
{
  n++;
  int im = n / bpm;
  int ib = n % bpm;

  do {
    fd_mask m = fds_bits[im];
    if(m != 0)
      for(fd_mask tm = 1 << ib; ib < bpm; ib++, tm <<= 1)
	if(m & tm) return im * bpm + ib;
    im++; ib = 0;
  } while(im < mps);    
  return -1;
}

int FdSet::prev(int n) const
{
  if(n == -1) n = bps;
  n--;
  int im = n / bpm;
  int ib = n % bpm;

  do {
    fd_mask m = fds_bits[im];
    if(m != 0)
      for(fd_mask tm = 1 << ib; ib >= 0; ib--, tm >>= 1)
	if(m & tm) return im * bpm + ib;
    im--; ib = bpm - 1;
  } while(im >= 0);    
  return -1;
}

#include <iostream.h>

FdSet::FdSet(int fd ...)
{
  va_list ap;
  FD_ZERO(this);
  for(va_start(ap, fd); fd > -1; fd = va_arg(ap, int))
    FD_SET(fd, this);
  va_end(ap);
}

int FdSet::select(FdSet *r, FdSet *w, FdSet *e, u_int sec, u_int usec) const
{
  struct timeval tv = {sec, usec};
  if(r != NULL) *r = *this;
  if(w != NULL) *w = *this;
  if(e != NULL) *e = *this;
  return ::select(nfds(), r, w, e, &tv);
}

int FdSet::select(FdSet *r, FdSet *w, FdSet *e) const
{
  if(r != NULL) *r = *this;
  if(w != NULL) *w = *this;
  if(e != NULL) *e = *this;
  return ::select(nfds(), r, w, e, NULL);
}

/*
 * Test your port with this function:
 */
#ifdef FD_SET_TESTME

#include <iostream.h>

main()
{
  FdSet fds;
  fds.set(4);
  fds.set(19);
  fds.set(23);
  fds.set(36);
  fds.set(100);
  fds.set(200);
  fds.set(250);
  int fd;
  for(fd = fds.first(); fd >= 0; fd = fds.next(fd))
    cout << fd << ", " << flush;
  cout << endl;
  for(fd = fds.last(); fd >= 0; fd = fds.prev(fd))
    cout << fd << ", " << flush;
  cout << endl;
  fds.zero();
  fds.set(0);
  fds.set(1);
  fds.set(2);
  FdSet r, w, e;
  int n = fds.select(&r, &w, &e);
  cout << "select returned " << n << endl;
  cout << endl << "read:      ";
  for( fd = r.first(); fd >= 0; fd = r.next(fd))
    cout << fd << ", " << flush;
  cout << endl << "write:     ";
  for( fd = w.first(); fd >= 0; fd = w.next(fd))
    cout << fd << ", " << flush;
  cout << endl << "exception: ";
  for( fd = e.first(); fd >= 0; fd = e.next(fd))
    cout << fd << ", " << flush;
  cout << endl;
}

#endif