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/*
* The Unix Channel
*
* by Michel Beaudouin-Lafon
*
* Copyright 1990-1993
* Laboratoire de Recherche en Informatique (LRI)
*
* Client side: services
*
* $Id$
* $CurLog$
*/
#include "Service.h"
/*?class UchService
An object of class \typ{UchService} (derived from \typ{UchMsgStream}) exists in a client process
to represent the server it is connected to.
The class \typ{UchService} is virtual: you must create subclasses that redefine
at least \fun{NewMessage} from class \fun{UchMsgStream}, and if necessary \fun{ConvertAnswer}.
\fun{NewMessage} should decipher the incoming message, transform it into an event,
and put in into the event queue with \fun{PutEvent}.
It can also handle non event messages (for instance errors).
?*/
/*?class UchMsgQueue
An event queue is a linked list of events.
Events are normally appended to the end of the queue and extracted from the beginning.
?*/
/*?nodoc?*/
UchMsgQueue :: UchMsgQueue ()
: CcuSmartData (),
Queue ()
{
}
/*?nodoc?*/
UchMsgQueue :: ~UchMsgQueue ()
{
}
#ifdef DOC
/*?
Append an event to the queue.
?*/
void
UchMsgQueue :: Put (UchMessage* msg)
{
}
/*?
Put an event back in the queue (therefore it becomes the first event of the queue).
?*/
void
UchMsgQueue :: PutBack (UchMessage* msg)
{
}
/*?
Return the first event from the queue and remove it.
?*/
UchMessage*
UchMsgQueue :: Get ()
{
}
/*?
Return the first event from the queue without removing it.
?*/
UchMessage*
UchMsgQueue :: Peek ()
{
}
#endif /* DOC */
/*?
Construct an empty service.
?*/
UchService :: UchService ()
: UchMsgStream (),
EvQueue (0)
{
}
/*?
Construct a service connected to address \var{a}.
?*/
UchService :: UchService (UchAddress* a)
: UchMsgStream (0, a),
EvQueue (0)
{
}
/*?nodoc?*/
UchService :: UchService (const UchService& s)
: UchMsgStream (s),
EvQueue (s.EvQueue)
{
}
/*?nodoc?*/
UchService :: ~UchService ()
{
EvQueue = 0; // deletes it
}
/*?nodoc?*/
UchChannel*
UchService :: Copy () const
{
return new UchService (*this);
}
/*?
Set the event queue to be used to store the incoming events.
If not set, a default event queue is created.
This function is intended to share a queue between several servers.
?*/
void
UchService :: SetEvQueue (UchMsgQueue* evq)
{
EvQueue = evq;
}
/*?nextdoc?*/
UchMessage*
UchService :: PeekEvent (bool wait)
{
Flush ();
if (!EvQueue)
EvQueue = new UchMsgQueue;
UchMessage* ev = EvQueue->Peek ();
if (ev || ! wait)
return ev;
while (! ev) {
HandleRead ();
ev = EvQueue->Peek ();
}
return ev;
}
/*?
These functions flush the output buffer, and check the events already in the queue.
If there is at least one, it is returned;
\fun{GetEvent} also removes it from the event queue.
If the event queue is empty and \var{wait} is true, the function blocks until an event arrives,
else it returns 0 without blocking.
These functions also create the event queue if it was not set with \fun{SetEvQueue}.
?*/
UchMessage*
UchService :: GetEvent (bool wait)
{
Flush ();
if (!EvQueue)
EvQueue = new UchMsgQueue;
UchMessage* ev = EvQueue->Get ();
if (ev || ! wait)
return ev;
while (! ev) {
HandleRead ();
ev = EvQueue->Get ();
}
return ev;
}
/*?nextdoc?*/
void
UchService :: PutEvent (UchMessage* ev)
{
if (! EvQueue)
EvQueue = new UchMsgQueue;
EvQueue->Put (ev);
}
/*?
These functions are similar to the functions \fun{Put} and \fun{PutBack}
on the event queue of the server.
They create the event queue if it was not set with \fun{SetEvQueue},
and set the event's server.
?*/
void
UchService :: PutBackEvent (UchMessage* ev)
{
if (! EvQueue)
EvQueue = new UchMsgQueue;
EvQueue->PutBack (ev);
}
/*?class UchEventMsg
\typ{UchEventMsg} is the base class for event messages to be used with
\typ{UchService}s. The difference between an \typ{UchEventMsg} and a
\typ{UchMessage} lies in the function \fun{Activate}: event messages
add themselves to the event queue.
?*/
/*?nodoc?*/
UchEventMsg :: UchEventMsg ()
{
}
/*?nodoc?*/
UchEventMsg :: ~UchEventMsg ()
{
}
/*?nodoc?*/
bool
UchEventMsg :: Activate (UchMsgStream& s, bool)
{
UchService* svc = (UchService*) &s;
svc->PutEvent (this);
return true;
}
/*?class UchGenMsg
This is a sample derived class of \typ{UchEventMsg}.
It defines events that contain a pointer to a \typ{UchMessage}.
This message must be allocated dynamically because it is deleted by the destructor.
The virtual functions \fun{ReadFrom} and \fun{WriteTo} are defined to act upon the message stored in the event.
The following example fetches a word from the input buffer,
creates a message depending on its value
(\typ{FOO\_MSG} and \typ{BAR\_MSG} have been derived from \typ{UchMessage}),
and transfers the data from the buffer to the event with \fun{Get}.
This piece of code typically appears in the body
of \fun{NewMessage}:
\begin{ccode}
UchGenMsg* ev = new UchGenMsg;
sword type;
if (! buf.Peek (&type))
return;
switch (type) {
case Foo :
ev->SetMsg (new FOO_MSG);
break;
case Bar :
ev->SetMsg (new BAR_MSG);
break;
...
}
if (!buf.Get (ev))
// protocol error
PutEvent (ev);
\end{ccode}
?*/
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