path: root/comm/OLD/dgram.cc

/*
 *	The Unix Channel
 *
 *	by Michel Beaudouin-Lafon
 *
 *	Copyright 1990-1993
 *	Laboratoire de Recherche en Informatique (LRI)
 *
 *	Reliable datagrams - to be updated
 *
 *	$Id$
 *	$CurLog$
 */

#include "MsgBuffer.h"
#include "dgram.h"
#include "error.h"

#include <sys/ioctl.h>
#include <errno.h>
#include <stdlib.h>
#include <memory.h>

// needed only if DEBUG is active
#include <stdio.h>
#define DEBUG	//**//
bool	DGTrace = FALSE;

/*?class UchDGRAM
The class \typ{UchDGRAM} is derived from \typ{UchDatagram}.
It adds to a datagram a simple protocol to ensure that all messages sent are received.
It does not prevent message duplication, neither does he ensure that the messages are
received in the order they are sent.

Each message is sent along with a tag number. The sender keeps each message it sends
until it receives an acknowledge for it.
When a message is received, an acknowledge is sent back.
Unacknowledged messages are resent at regular intervals.
If a message is not acknowledged after a given number of retries, it is simply discarded.
?*/

struct PENDING {
	UchMsgBuffer*	outBuf;
	pUchAddress	toAddr;
	short		retries;	// for pending
	lword		id;	// for input
	
	PENDING (UchMsgBuffer* b, UchAddress* a, int r = 0)	{ outBuf = b; toAddr = a; retries = r; id = 0;}
	~PENDING ()					{ delete outBuf; toAddr = 0; }
};

/*?hidden?*/
void
UchDGRAM_TIMER :: Handle (Millisecond)
{
if (DGTrace) printf ("*** TimeOut ***\n");
	dgram.Expired ();
}

/*?nodoc?*/
UchDGRAM_TIMER :: UchDGRAM_TIMER (UchDGRAM& dg)
: CcuBaseTimer (0),
  dgram (dg)
{
}

UchDGRAM_TIMER :: ~UchDGRAM_TIMER ()
{
}

/*?hidden?*/
void
UchDGRAM :: Init ()
{
	npending = 0;
	ninput = 0;
	fromAddr = 0;
	retry = 5;
	resend = FALSE;
	locked = 0;
	timeout = 1000;
	sync = FALSE;
}

/*?nextdoc?*/
UchDGRAM :: UchDGRAM ()
: pending (2), input (), timer (*this)
{
	Init ();
}

/*?
Same constructors as for the class \typ{UchDatagram};
?*/
UchDGRAM :: UchDGRAM (UchAddress* b, UchAddress* c)
: UchDatagram (b, c), pending (2), input (), timer (*this)
{
	Init ();
}

/*?
The destructor of \typ{UchDGRAM} discards all pending and input messages.
A derived class could call \fun{Drain} in its destructor to send all pending messages,
and it could call \fun{Receive} while \fun{NumInput} is non null.
?*/
UchDGRAM :: ~UchDGRAM ()
{
	timer.Stop ();
	if (! npending)
		return;
	CcuIdIterOf <PENDING> iter = pending;
	while (++iter) {
		RemovePending (iter.CurId ());
		if (! npending)
			break;
	}
	if (ninput) {
		CcuListIterOf <PENDING> li (input);
		while (++li)
			delete *li;

		input.Clear ();
	}
}

static const	byte DGRAM_ERR = 0;
static const	byte DGRAM_SEND = 1;
static const	byte DGRAM_ACK = 2;

//	GetInput reads an incoming message
//		if its an ack, it is processed
//		if it is a normal message, it is stored in the input list
//	CheckInput calls GetInput wile there is something to read
//	WaitInput returns when a message is in the input list
//	Wait waits for the acknowledge of a particular id

/*?hidden?*/
int
UchDGRAM :: GetInput (int len)
{
	UchMsgBuffer* buf = new UchMsgBuffer (len);
	int n;
	while ((n = UchDatagram :: Receive (*buf)) == -1 && errno == EINTR)
DEBUG	SysError (ErrWarn, "UchDGRAM::GetInput")
		;
	if (n < 0) {
		SysError (ErrWarn, "UchDGRAM::GetInput");
		delete buf;
		return DGRAM_ERR;
	}
DEBUG	if (DGTrace) printf ("UchDGRAM :: GetInput : received %d bytes\n", buf->BufLength ());
	
	lword id;
	buf->Get (id);
	byte s;
	buf->Get (s);
DEBUG	if (DGTrace) printf ("UchDGRAM :: GetInput : id %x byte %d\n", id, s);
	
	if (s == DGRAM_ACK) {
DEBUG	if (DGTrace) printf ("UchDGRAM :: GetInput : acknowledged %x\n", id);
		RemovePending (id);
		delete buf;
		return DGRAM_ACK;
	}
	
	PENDING* p = new PENDING (buf, FAddr);
	p->id = id;
	input.Append (p);
	ninput++;
	return DGRAM_SEND;
}

/*?hidden?*/
bool
UchDGRAM :: CheckInput ()
{
	// get any pending messages
	for (;;) {
		lword	np;
		if (ioctl (FilDes (), FIONREAD, (char*) &np) < 0)
			return FALSE;
DEBUG	if (DGTrace) if (np) printf ("UchDGRAM :: CheckInput : FIONREAD says %d\n", np);
		if (np == 0)
			break;
		if (GetInput (int (np)) == DGRAM_ERR)
			return FALSE;
	}
	return TRUE;
}

/*?hidden?*/
bool
UchDGRAM :: WaitInput ()
{
	// check the input queue
	if (ninput)
		return TRUE;
	
	// check pending input
	if (! CheckInput ())
		return FALSE;
	
	// block until something
	while (! ninput)
		if (GetInput (2048) == DGRAM_ERR)	// *** arbitrary max size
			return FALSE;
	return TRUE;
}

/*?hidden?*/
bool
UchDGRAM :: Wait (lword id)
{
DEBUG	if (DGTrace) printf ("UchDGRAM::Wait %x\n", id);
	bool ret = FALSE;
	bool loop = TRUE;
	Lock ();
	
	PENDING* pend;
	while (loop) {
		if (! CheckInput ())
			break;
		
		// did we receive the ack ?
		pend = pending.Get (id);
		if (! pend) {
			ret = TRUE;
			break;
		}
		
		if (resend) {
DEBUG	if (DGTrace) printf ("UchDGRAM::Wait : resending\n");
			if (pend->retries <= 0) {
				RemovePending (id);
				break;
			}
			
			int n = SendBuffer (* pend->outBuf, *pend->toAddr);
			if (n < 0)
				break;
			--pend->retries;
			resend = FALSE;
		} else
DEBUG	if (DGTrace) printf ("UchDGRAM::Wait : waiting\n"),
			timer.Wait ();	// sets resend to TRUE
	}
	Unlock ();
DEBUG	if (DGTrace) printf ("UchDGRAM::Wait : %s\n", ret ? "done" : "failed");
	return ret;
}

//	SendAck sends an acknowledge
//	Expired is called when the resend timer has expired
//	PrepareToSend returns a buffer with the header set,
//		and adds it to the pending set
//	SendBuffer sends a buffer, handling interrupted sys calls
//	RemovePending removes a pending message from the table
/*?hidden?*/
void
UchDGRAM :: SendAck (lword id, UchAddress& addr)
{
	UchMsgBuffer buf;
	buf.Append (id);
	buf.Append (DGRAM_ACK);
	SendBuffer (buf, addr);
	fromAddr = & addr;
DEBUG	if (DGTrace) printf ("UchDGRAM :: SendAck : acknowledging %x\n", id);
}

/*?hidden?*/
void
UchDGRAM :: Expired ()
{
	if (locked)
		resend = TRUE;
	else
		Resend ();
}

/*?hidden?*/
UchMsgBuffer*
UchDGRAM :: PrepareToSend (UchAddress& to, int retries)
{
	UchMsgBuffer* obuf = new UchMsgBuffer;
/*
UchInetAddress* ia = (UchInetAddress*) &to;
UchAddress* toCopy = new UchInetAddress (ia->Host (), ia->Port ());
*/
	if (retries == 0)
		retries = retry;
	PENDING* out = new PENDING (obuf, &to /*toCopy*/, retries);
	outId = pending.Store (out);
	
DEBUG	if (DGTrace) printf ("UchDGRAM :: PrepareToSend : id %x\n", outId);
	obuf->Append (outId);
	obuf->Append (DGRAM_SEND);
	
	if (! npending) {
		timer.ChangePeriod (timeout);
		timer.Restart ();
	}
	npending++;

	return obuf;
}

/*?hidden?*/
int
UchDGRAM :: SendBuffer (UchMsgBuffer& buf, UchAddress& addr)
{
	int n;
	while ((n = UchDatagram :: Send (buf, addr, TRUE)) == -1 && errno == EINTR)
DEBUG	SysError (ErrWarn, "UchDGRAM::SendBuffer")
		;
	return n;
}

/*?hidden?*/
void
UchDGRAM :: RemovePending (lword id)
{
	PENDING* pend = pending.Get (id);
	if (! pend) {
		Error (ErrWarn, "Receive", "unrecognized ACK");
		return;
	}
	pending.Remove (id);
	delete pend;
	npending--;
	if (npending == 0)
		timer.Stop ();
}

//----------------	the public functions

/*?nextdoc?*/
int
UchDGRAM :: Send (byte* buf, int len, UchAddress& to, bool ack, int retries)
{
DEBUG	if (DGTrace) printf ("UchDGRAM :: Send\n");
	Lock ();
	UchMsgBuffer* obuf = PrepareToSend (to, retries);
	obuf->Append (buf, len);
	int n = SendBuffer (*obuf, to);
	CheckInput ();
	int ret = (ack || sync) ? (Wait (outId) ? n : -1) : n;
	Unlock ();
	return ret;
}

/*?nextdoc?*/
int
UchDGRAM :: Receive (byte* buf, int len)
{
DEBUG	if (DGTrace) printf ("UchDGRAM :: Receive\n");
	if (! WaitInput ())
		return -1;
	PENDING* p = input.RemoveFirst ();
	ninput--;
	int n = p->outBuf->BufLength ();
	if (len < n)
		n = len;
	memcpy (buf, p->outBuf->Buffer (), n);
	SendAck (p->id, *p->toAddr);
	delete p;
DEBUG	if (DGTrace) printf ("UchDGRAM :: Receive : received %d bytes\n", n);
	return n;
}

/*?nextdoc?*/
int
UchDGRAM :: Reply (byte* buf, int len, bool ack, int retries)
{
	if (! fromAddr)
		return -1;
	return Send (buf, len, *fromAddr, ack, retries);
}

/*?nextdoc?*/
int
UchDGRAM :: Send (UchMsgBuffer& buf, UchAddress& to, bool peek, bool ack, int retries)
{
DEBUG	if (DGTrace) printf ("UchDGRAM :: Send\n");
	Lock ();
	UchMsgBuffer* obuf = PrepareToSend (to, retries);
	obuf->Append (buf.Buffer (), buf.BufLength ());
	if (! peek)
		buf.Flush ();
	int n = SendBuffer (*obuf, to);
	CheckInput ();
	int ret = (ack || sync) ? (Wait (outId) ? n : -1) : n;
	Unlock ();
	return ret;
}

/*?nextdoc?*/
int
UchDGRAM :: Receive (UchMsgBuffer& buf)
{
DEBUG	if (DGTrace) printf ("UchDGRAM :: Receive\n");
	if (! WaitInput ())
		return -1;
	PENDING* p = input.RemoveFirst ();
	ninput--;
	int n = p->outBuf->BufLength ();
	buf.Append (p->outBuf->Buffer (), n);
	SendAck (p->id, *p->toAddr);
	delete p;
DEBUG	if (DGTrace) printf ("UchDGRAM :: Receive : received buffer %d bytes\n", n);
	return n;
}

/*?
These functions are similar to the same functions in the class \typ{UchDatagram},
except that they manage messages acknowledgement.
\fun{Send} saves the message in a buffer so that it can be resent if no acknowledge
is received.
\fun{Receive} acknowledges the received message.
\fun{Reply} sends the message to the sender of the last received message.
If \var{ack} is TRUE, the acknowledge of the message is waited for.
In that case, \fun{Send} returns -1 if the acknowledge is not received.
If \var{retries} is non zero, it specifies a number of retries for this message
different from the default retry number of this dgram.
?*/
int
UchDGRAM :: Reply (UchMsgBuffer& buf, bool peek, bool ack, int retries)
{
	if (! fromAddr)
		return -1;
	return Send (buf, *fromAddr, peek, ack, retries);
}

/*?nextdoc?*/
bool
UchDGRAM :: Send (UchMessage& msg, UchAddress& to, bool ack, int retries)
{
DEBUG	if (DGTrace) printf ("UchDGRAM :: Send message\n");
	Lock ();
	UchMsgBuffer* obuf = PrepareToSend (to, retries);
	obuf->Append (msg);
// int l;	
// printf ("outBuffer is %d bytes long\n", l = obuf->BufLength ());
// for (int i = 0; i < l; i++) printf ("%02x ", obuf->Buffer () [i]);
// printf ("\n");
	int n = SendBuffer (*obuf, to);
	CheckInput ();
	bool ret;
	if (ack || sync)
		ret = Wait (outId) ? TRUE : FALSE;
	else
		ret = bool (n != obuf->BufLength ());
	Unlock ();
	return ret;
}

/*?nextdoc?*/
bool
UchDGRAM :: Receive (UchMessage* msg)
{
DEBUG	if (DGTrace) printf ("UchDGRAM :: Receive message\n");
	if (! WaitInput ())
		return FALSE;
	PENDING* p = input.RemoveFirst ();
	ninput--;
// int n;	
// printf ("inBuffer is %d bytes long\n", n = p->outBuf->BufLength ());
// for (int i = 0; i < n; i++) printf ("%02x ", p->outBuf->Buffer () [i]);
// printf ("\n");
	if (! p->outBuf->Get (*msg))
		return FALSE;
	SendAck (p->id, *p->toAddr);
	delete p;
DEBUG	if (DGTrace) printf ("UchDGRAM :: Receive : received message\n");
	return TRUE;
}

/*?
These functions are similar to the previous functions except that they take
a \typ{UchMessage} as argument.
\fun{Send} converts the message in the output buffer.
If \var{ack} is TRUE, the acknowledge of the message is waited for.
In that case, \fun{Send} returns FALSE if the acknowledge is not received.
If \var{retries} is non zero, it specifies a number of retries for this message
different from the default retry number of this dgram.
\fun{Receive} converts the incoming data into the message passed as argument.
\fun{Reply} sends the message to the sender of the last received message.
See also the function \fun{NewMessage} to handle incoming messages.
?*/
bool
UchDGRAM :: Reply (UchMessage& msg, bool ack, int retries)
{
	if (! fromAddr)
		return FALSE;
	return Send (msg, *fromAddr, ack, retries);
}

//-----------------------
#if 0
bool
UchDGRAM :: Ask (UchMessage& msg, UchAddress& to)
{
DEBUG	if (DGTrace) printf ("UchDGRAM :: Ask\n");
	Lock ();
	UchMsgBuffer* obuf = PrepareToSend (to, DGRAM_ASK *******);
	obuf->Append (msg);
	int n = SendBuffer (*obuf, to);
	CheckInput ();
	bool ret = Wait (outId) ? TRUE : FALSE;
	if (ret) {
		// wait answer
		for (;;) {
			if (! WaitInput ())
				continue;
			PENDING* pend = input.Last ();
			if (pend->toAddr == to.............
		}
	}
	Unlock ();
	return ret;
}
#endif
//-----------------------

/*?
Resend all messages for which no acknowledge has been received.
If a UchMessage.has been resent more than the retry number, it is discarded.
When successive messages are to be sent to the same address, only the first
is resent, to avoid connection overflow.
?*/
void
UchDGRAM :: Resend ()
{
if (DGTrace) printf ("UchDGRAM::Resend\n");
	Lock ();
	if (npending)
		CheckInput ();
	if (! npending) {
		resend = FALSE;
		Unlock ();
		return;
	}
	
	UchAddress*	addr = 0;
	
	CcuIdIterOf <PENDING> iter = pending;
	while ( ++iter) {
		PENDING* pend = *iter;
		if (pend->retries <= 0) {
			// the output buffer contains the leading id and type
			UchMsgBuffer fake (*pend->outBuf);
			lword id;
			byte typ;
			fake.Get (id);
			fake.Get (typ);
			if (! DiscardNotify (fake, *pend->toAddr)) {
				pend->retries = retry;	// *** should be controllable ?
				continue;
			}
if (DGTrace) printf ("UchDGRAM::Resend : abandonning %x\n", iter.CurId ());
			RemovePending (iter.CurId ());
			if (! npending)
				break;
		} else
		if (addr != (UchAddress*) pend->toAddr) {
DEBUG	printf ("UchDGRAM::Resend : resending %x\n", iter.CurId ());
			SendBuffer (* pend->outBuf, *pend->toAddr);
			--pend->retries;
			addr = pend->toAddr;
			CheckInput ();
		}
DEBUG	else printf ("UchDGRAM::Resend : skipping %x\n", iter.CurId ());
	}
	
	resend = FALSE;
	Unlock ();
}

/*?
This virtual function is called whenever a pending message is about
to be discarded because no acknowledge has been received after
the the default number of retries.
If it returns FALSE, the message is not discarded and its retry count is reset to zero.
Returning FALSE is not very social.
The default action is to return TRUE, thus discarding the pending message.
?*/
bool
UchDGRAM :: DiscardNotify (UchMsgBuffer&, UchAddress&)
{
	return TRUE;
}

/*?
Set the interval between retries.
The default value is 1000 (1 second).
?*/
void
UchDGRAM :: SetRetryTime (Millisecond m)
{
	timeout = m;
	if (npending) {
		timer.ChangePeriod (m);
		timer.Restart ();
	}
}

/*?
Wait until all acknowledges have been received,
or until all messages have been discarded.
?*/
void
UchDGRAM :: Drain ()
{
	if (npending)
		CheckInput ();
	while (npending)
		timer.Wait ();
}

/*?
This virtual function is called by \fun{HandleRead}.
It must be redefined in a derived class if \fun{HandleRead} is to be used
(for instance if this \typ{UchDGRAM} is put in a channel set).
This function should convert the contents of the buffer into a message, and handle it.
It should return TRUE if the message was correctly handled, else FALSE.
Note that if it returns FALSE, the message will not be acknowledged, and thus it will
be resent later.
The default behaviour of this virtual function is to issue an error message and
to return TRUE.
?*/
bool
UchDGRAM :: NewMessage (UchMsgBuffer&)
{
	Error (ErrWarn, "UchDGRAM :: NewMessage", "should be defined in derived class");
	return TRUE;
}

/*?
This is an instance of the virtual function \fun{HandleRead} of class \typ{UchChannel}.
It calls the virtual function \fun{NewMessage} when a message is received.
If \fun{NewMessage} returns TRUE, an acknowledge is sent back.
This functions also handles incoming acknowledges.
?*/
void
UchDGRAM :: HandleRead ()
{
	if (! CheckInput ())
		return;
	if (! ninput)
		return;
	
DEBUG	if (DGTrace) printf (">>UchDGRAM :: HandleRead\n");
	PENDING* p = input.RemoveFirst ();
	ninput--;
	if (NewMessage (* p->outBuf))
		SendAck (p->id, *p->toAddr);
DEBUG	if (DGTrace) printf ("<<UchDGRAM :: HandleRead\n");
}

/*?
This is an instance of the virtual function \fun{HandleSelect} of class \typ{UchChannel}.
It calls the virtual function \fun{NewMessage} when a message is in the input buffer.
If \fun{NewMessage} returns TRUE, an acknowledge is sent back.
This functions also handles incoming acknowledges.
?*/
bool
UchDGRAM :: HandleSelect ()
{
	if (! ninput)
		return FALSE;
DEBUG	if (DGTrace) printf (">>UchDGRAM :: HandleSelect\n");
	PENDING* p = input.RemoveFirst ();
	ninput--;
	if (NewMessage (* p->outBuf))
		SendAck (p->id, *p->toAddr);
DEBUG	if (DGTrace) printf ("<<UchDGRAM :: HandleSelect\n");
	return TRUE;
}

#ifdef DOC
// fake entries for documentation

/*?
Return the number of pending messages
?*/
int
UchDGRAM :: NumPending ()
{ }

/*?
Return the number of waiting input messages
?*/
int
UchDGRAM :: NumInput ()
{ }

/*?
Set the number of times a message is resent until it is discarded.
The default value is 5.
?*/
void
UchDGRAM :: SetRetry (short r)
{ }

/*?
Set the synchronous mode of this \typ{UchDGRAM}.
If \var{s} is TRUE, the \fun{Send} functions always wait for the acknowledge of the messages.
The default value is FALSE.
?*/
void
UchDGRAM :: SetSync (bool s)
{ }

#endif /* DOC */