/*
    SyscallMsg.c, Copyright 1999 (c) by George Fankhauser,
    Swiss Federal Institute of Technology,
    Computer Engineering and Networks Laboratory.

    TOPSY -- A Teachable Operating System.
             Implementation of a tiny and simple
             micro kernel for teaching purposes.

    For further information, please visit http://www.tik.ee.ethz.ch/~topsy

    This software is provided under the terms of the GNU General Public Licence.

    A full copy of the GNU GPL is provided in the file COPYING found in the 
    development root of Topsy.
*/
/*
	*** empty log message ***
	
	Revision 1.3  1999/05/19 14:30:47  gfa
	ome linux tweakin' done...

	Revision 1.2  1999/05/13 17:06:05  jeker
	Initial revision

*/
  
#include "Messages.h"  
#include "Syscall.h"  

#include "Unix.h"

/* message passing, usually performed by traps, is mapped to unix signals 
 * 
 * the unused USR1 (SEND) and USR2 (RECV) signals are used for this purpose
 *
 * signals are, like exceptions and interrupts, centrally dispatched in
 * generalExceptionHandler(). other signals are used for task switching and
 * preemption (SIGALARM).
 */

SyscallError tmMsgSend(ThreadId to, Message* msg)
{
    msg->from = to;

    kill(getpid(), SEND);

#ifdef sparc
    asm("mov %g7,%i0");		// replaces the return
#endif				// on other architectures, the return register
}				// stays the same (g7 is a hack; see Unix.h)


SyscallError 
tmMsgRecv(ThreadId* from, MessageId msgId, Message* msg, int timeOut)
{
    msg->from = *from;
    msg->id = msgId;
    
    kill(getpid(), RECV);
       
    *from = msg->from;		// from id stored by kernel in msg->from

#ifdef sparc
    asm("mov %g7,%i0");		// replaces the return
#endif				// on other architectures, the return register
}				// stays the same


Boolean testAndSet(Boolean* lockvar)
{
    Boolean ret;

    // turn off signals/clock
    sigset_t set, oldset;
    
    // save old mask
    sigprocmask(SIG_SETMASK, NULL, &oldset);

    // block all sigs
    sigfillset(&set);
    sigprocmask(SIG_SETMASK, &set, NULL);
    if (*lockvar == FALSE) {
	*lockvar = TRUE;
	ret = TRUE;
    }
    else {
	ret = FALSE;
    }
    // restore old mask
    sigprocmask(SIG_SETMASK, &oldset, NULL);

    return ret;
}