path: root/comm/Multiplexer.cc

/*
 *	The Unix Channel
 *
 *	by Michel Beaudouin-Lafon
 *
 *	Copyright 1990-1993
 *	Laboratoire de Recherche en Informatique (LRI)
 *
 *	Channel sets, or multiplexers
 *
 *	$Id$
 *	$CurLog$
 */

#include "Multiplexer.h"
#include "TimeOut.h"
#include "Signal.h"

#include <signal.h>	// for NSIG
#include <sys/errno.h>
#include <sys/time.h>
#include <sys/socket.h>

#include <stdlib.h>
#include <stdio.h>
#include <memory.h>

#if defined(__hpux) && !defined(__GNUG__)
#define FD_SET_TYPE(x) ((int*) x)
#else
#define FD_SET_TYPE(x) (x)
#endif

extern int	errno;

#ifndef FD_SET
#ifndef NFDBITS
#define	FD_SET(n, p)	((p)->fds_bits[0] |= (1 << (n)))
#define	FD_CLR(n, p)	((p)->fds_bits[0] &= ~(1 << (n)))
#define	FD_ISSET(n, p)	((p)->fds_bits[0] & (1 << (n)))
#define	FD_ZERO(p)	((p)->fds_bits[0] = 0)
#else
#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)	memset((char *)(p), 0, sizeof(*(p)))
#endif
#endif


/*?class UchMultiplexer
An object of class \typ{UchMultiplexer} is a set of channels.
Some of the channels in the set are active, others can be inactive.
A channel set can be scanned so that the functions \fun{HandleRead}
and \fun{HandleWrite} are called for each active channel that is ready to read or write.
The functions \fun{HandleSelect} of each channel is called before actually scanning
so that each channel can perform a background task or buffer input/output.
This provides a level of abstraction over the Unix \fun{select} system call.
Note that the functions that take an integer file descriptor as argument can be passed
a \typ{FILDES} or a \typ{UchChannel} because the corresponding conversion operators are defined.

The class \typ{^{pCHAN_SET}} implements smart pointers to channel sets.
Smart pointers behave like pointers but they manage a reference count on the
pointed to objects for an automatic reclaim of dynamically allocated objects.
?*/

//	constructor: initialize states
//

/*?
Create an empty channel set.
?*/
UchMultiplexer :: UchMultiplexer ()
: Channels (new pUchChannel [NFILE]),
  Timers (),
  ReadCount (0),
  WriteCount (0),
  SelectCount (0),
  Looping (FALSE),
  SigFired (FALSE),
  TimeOut (-1),
  Handlers (new UchBaseSignalHandler* [NSIG]),
  NbSignals (new int [NSIG])
{
	FD_ZERO (&ReadMask);
	FD_ZERO (&WriteMask);
	FD_ZERO (&SelectMask);
	memset (Handlers, 0, NSIG * sizeof (UchBaseSignalHandler*));
	memset (NbSignals, 0, NSIG * sizeof (int));
}

/*?nodoc?*/
UchMultiplexer :: ~UchMultiplexer ()
{
#ifdef CPLUS_BUG4
	delete [NFILE] Channels;
#else
	delete [] Channels;
	delete [] NbSignals;
	delete [] Handlers;
#endif
	Channels = 0;
}

/*?
Add a channel to the set.
Note that the argument is a pointer to the channel; no copy is made by this function.
If a channel with the same file descriptor as the one being added is already in the set,
the old channel is first removed, thus calling \fun{RemoveNotify} for that channel.
The virtual function \fun{AddNotify} is called before actually adding the channel
to the set.
?*/
void
UchMultiplexer :: Add (UchChannel* chan)
{
	int fd = chan->FilDes ();
	if (fd < 0)
		return;
	pUchChannel ochan = Channels [fd];
	if (ochan)
		Remove (fd);
	chan->AddNotify (*this);
	AddNotify (chan);
	Channels [fd] = chan;
	SetMasks (fd, chan->IOMode ());
}

pUchChannel NIL_CHAN (0);

/*?
Remove a channel from the set.
The virtual function \fun{RemoveNotify} is called before actually removing the channel
from the set.
?*/
void
UchMultiplexer :: Remove (int fd)
{
	if (fd < 0)
		return;
	UchChannel* ch = Channels [fd];
	if (ch) {
		ch->RemoveNotify (*this);
		RemoveNotify (ch);
		SetMasks (fd, IONone);
		Channels [fd] = 0;
	}
}

/*?
Remove all channels from this channel set.
This function calls \fun{Remove} for all channels of the set.
This is a way of exiting from \fun{LoopScan}.
?*/
void
UchMultiplexer :: RemoveAll ()
{
	for (int fd = 0; fd < NFILE; fd++)
		Remove (fd);
}

/*?
Change the mode of a channel in the set.
Mode \var{IONone} makes the channel inactive (without removing it).
The virtual function \fun{SetModeNotify} is called before actually changing
the mode of the channel.
?*/
void
UchMultiplexer :: SetMode (int fd, IOMODE mode)
{
	if (fd < 0)
		return;
	
	SetModeNotify (Channels [fd], mode);
	SetMasks (fd, mode);
	Channels [fd] -> SetMode (mode);
}


// update the masks when channel fd changes its mode
//
/*?hidden?*/
void
UchMultiplexer :: SetMasks (int fd, IOMODE mode)
{
	if (mode & IORead) {
		if (! FD_ISSET (fd, &ReadMask)) {
			ReadCount ++;
			FD_SET (fd, &ReadMask);
		}
	} else {
		if (FD_ISSET (fd, &ReadMask)) {
			FD_CLR (fd, &ReadMask);
			ReadCount --;
		}
	}
	
	if (mode & IOWrite) {
		if (! FD_ISSET (fd, &WriteMask)) {
			WriteCount ++;
			FD_SET (fd, &WriteMask);
		}
	} else {
		if (FD_ISSET (fd, &WriteMask)) {
			FD_CLR (fd, &WriteMask);
			WriteCount --;
		}
	}
	
	if (mode & IOSelect) {
		if (! FD_ISSET (fd, &SelectMask)) {
			SelectCount ++;
			FD_SET (fd, &SelectMask);
		}
	} else {
		if (FD_ISSET (fd, &SelectMask)) {
			FD_CLR (fd, &SelectMask);
			SelectCount --;
		}
	}
	
}

/*?nextdoc?*/
void
UchMultiplexer :: AddNotify (UchChannel*)
{
	// nothing
}

/*?nextdoc?*/
void
UchMultiplexer :: RemoveNotify (UchChannel*)
{
	// nothing
}

/*?
This function calls the select handler of each channel of the set in select mode.
It returns TRUE as soon as one select handler returns true,
else it returns FALSE when the select handlers have been called.
?*/
bool
UchMultiplexer :: HandleSelect ()
{
	int	fd, nfd;
	
	if (fd0 >= NFILE)
		fd0 = 0;
	for (fd = fd0++, nfd = SelectCount; nfd; (fd < NFILE) ? fd++ : (fd = 0)) {
		if (! FD_ISSET (fd, &SelectMask))
			continue;
		if (Channels [fd] -> HandleSelect ())
			return TRUE;
		nfd--;
		if (! Looping)
			return FALSE;
	}
	return FALSE;
}

/*?
These virtual functions are called by the functions \fun{Add}, \fun{Remove}
(and thus \fun{RemoveAll}) and \fun{SetMode}.
They provide hooks for application that need to take special action when the
set changes. They are called before the corresponding action is actually
carried out.
By default these functions do nothing.
?*/
void
UchMultiplexer :: SetModeNotify (UchChannel*, IOMODE)
{
	// nothing
}

////// should add signal handling
/*?nextdoc?*/
int
UchMultiplexer :: Scan (bool nointr, bool poll)
{
	fd_set rmsk, wmsk;
	int nfd, ret = -1;
	register int fd;
	struct timeval tout;
	struct timeval* timeout = 0;
	
	if (poll) {
		timeout = &tout;
		tout.tv_sec = tout.tv_usec = 0;
	}
	
	while (ret <= 0) {
		CcuCoreTimer::Fire (&Timers);
	
		if (ReadCount == 0 && WriteCount == 0 && SelectCount == 0)
			return 0;
		
		for (fd = 0, nfd = SelectCount; nfd; fd++) {
			if (! FD_ISSET (fd, &SelectMask))
				continue;
			UchChannel* ch = Channels [fd];
			if (ch && ch->HandleSelect ())
				return -2;
			nfd--;
		}
	
//printf ("Scan: read %x, write %x, TimeOut %d", ReadMask, WriteMask, TimeOut);
		rmsk = ReadMask;
		wmsk = WriteMask;
		if (!poll && TimeOut != -1) {
			CcuTimeStamp now;
			Millisecond delay = TimeOut - now;
//printf (", timeout in %d ms", delay);
			tout.tv_sec = delay / 1000;
			tout.tv_usec = 1000 * (delay % 1000);
			timeout = &tout;
		}
//printf ("\n");
		
		ret = select (NFILE, FD_SET_TYPE(&rmsk) /*read*/,  FD_SET_TYPE(&wmsk) /*write*/, 0 /*except*/, timeout);
		if (ret < 0 || ret == 0 && poll) {
//printf ("select failed: %d, errno %d\n", ret, errno);
			if (nointr && ret == -1 && errno == EINTR)
				continue;
			return ret;
		}
	}
	
	for (fd = 0, nfd = ret; nfd; fd++) {
//printf ("Scan: handle %d: r %d, w %d\n", fd, FD_ISSET (fd, &rmsk), FD_ISSET (fd, &wmsk));
		if (FD_ISSET (fd, &wmsk)) {
			nfd --;
			UchChannel* ch = Channels [fd];
			if (ch)
				ch->HandleWrite ();
		}
		if (FD_ISSET (fd, &rmsk)) {
			nfd--;
			UchChannel* ch = Channels [fd];
			if (ch)
				ch->HandleRead ();
		}
	}
	
	return ret;
}

/*?
Scan the channels in the set and call the channel's handlers.
First the select handler (\fun{UchChannel::HandleSelect}) of each channel with mode
\var{IOSelect} is called.
If it returns TRUE, \fun{Scan} exits immediately, while \fun{LoopScan} loops immediately.
If no select handler returns TRUE, the system call \fun{select} is used to poll or
wait for the channels that are ready.
When the select returns normally, the write handlers \fun{HandleWrite} of the
channels in mode \var{IOWrite} that are ready to write are called, and 
the read handlers (\fun{HandleRead}) of the channels in mode \fun{IORead}
that are ready to read are called.
If \var{nointr} is TRUE, ignore the interrupted system calls, else return an error
whenever the \fun{select} system call is interrupted.
If \var{poll} is TRUE, the call is non-blocking, else it is blocking.
\fun{Scan} calls \fun{select} only once;
it returns -2 if a select handler returns, it returns 0 if the channel set has no active channels,
else it returns the return code of \fun{select}.
\fun{LoopScan} calls \fun{select} repeatedly until \var{LoopEnd} is called, or
an error occurs, the channel set has no more active channel
This can occur because the select, read or write handler of a channel may remove
the channel or change its mode.
This is usually done when the read handler detects an end of file.
\fun{LoopScan} returns 0 when there are no more active channel in the set,
it returns -1 when an error occured (the code is in \var{errno}),
and it returns 1 if \fun{LoopEnd} was called.
?*/
int
UchMultiplexer :: LoopScan (bool nointr)
{
	fd_set rmsk, wmsk;
	register int nfd, fd;
	Looping = TRUE;
	
	for (fd0 = 0; Looping; fd0 < NFILE ? fd0++ : (fd0 = 0)) {
		/* First, handle signals */
		if (SigFired) {
			CcuSignalBlocker b (AllSigs);
			int c;
			for (int i = 0; i < NSIG; ++i)
				if (c = NbSignals [i]) {
					Handlers [i]->DeferredHandle (c);
					NbSignals [i] = 0;
					Handlers [i] = 0;
				}
		}

		/* Then, timers */
		CcuCoreTimer::Fire (&Timers);

		/* Then, I/Os */
		if (ReadCount == 0 && WriteCount == 0 && SelectCount == 0)
			return 0;
		
		for (fd = fd0, nfd = SelectCount; nfd; (fd < NFILE) ? fd++ : (fd = 0)) {
			if (! FD_ISSET (fd, &SelectMask))
				continue;
			UchChannel* ch = Channels [fd];
			if (ch && ch->HandleSelect ())
				break;
			nfd--;
			if (! Looping)
				return 1;
		}
		if (nfd)	// a handler returned TRUE.
			continue;
		
		rmsk = ReadMask;
		wmsk = WriteMask;
		struct timeval tv;
		struct timeval* timeout = 0;
		if (TimeOut != -1) {
			CcuTimeStamp now;
			Millisecond delay = TimeOut - now;
			tv.tv_sec = delay / 1000;
			tv.tv_usec = 1000 * (delay % 1000);
			timeout = &tv;
		}
		nfd = select (NFILE, FD_SET_TYPE(&rmsk) /*read*/, FD_SET_TYPE(&wmsk) /*write*/, 0 /*except*/, timeout);
		if (nfd < 0) {
			if (nointr && nfd == -1 && errno == EINTR)
				continue;
			return nfd;
		}

		for (fd = fd0; nfd; (fd < NFILE) ? fd++ : (fd = 0)) {
			if (FD_ISSET (fd, &wmsk)) {
				nfd--;
				Channels [fd] -> HandleWrite ();
				if (! Looping)
					return 1;
			}
			if (FD_ISSET (fd, &rmsk)) {
				nfd--;
				Channels [fd] -> HandleRead ();
				if (! Looping)
					return 1;
			}
		}
	}
	return 1;
}

//	string repr
//
/*?nodoc?*/
char*
UchMultiplexer :: StrRepr (char* buf)
{
	sprintf (buf, "R:%ux W:%ux", ReadMask, WriteMask);
	return buf;
}

#ifdef DOC
// fake entries for inline functions

/*?
This array operator returns a (smart) pointer to the channel corresponding to file descriptor \var{fd}.
If there is no such channel in this channel set, the operator returns NIL.
?*/
pUchChannel
UchMultiplexer :: operator [] (int fd)
{ }

/*?
Add a channel to the set.
Here the argument is a reference, and a dynamically allocated copy of it is actually added.
Compare with previous function.
?*/
void
UchMultiplexer :: Add (const UchChannel& ch)
{ }

/*?
This function makes \fun{LoopScan} exit immediately.
Thus it must be called from within a channel's handler.
?*/
void
UchMultiplexer :: LoopEnd ()
{ }

#endif /* DOC */

void
UchMultiplexer :: RegisterSignal (UchBaseSignalHandler& h)
{
	SigFired = TRUE;
	int sig = h.GetSignal () - 1;
	/* We have to work with arrays, because we are in a signal
	   handler, and we cannot use lists */
	Handlers [sig] = &h;
	NbSignals [sig]++;
}