/*************************************************************************
This file is part of aOS.

aOS 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.

aOS 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 aOS; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

Copyright 2001, 2002 Anssi Ylätalo
**************************************************************************
Modified by BRL
--init mailbox message to NULL
--set mmsg to NULL after it has been read
Added by BRL
-- aos_mbox_accept  : no wait

*/
//#include "aos.h"
//===================================================================
/* Create and initialize a mailbox */
aos_mcb *aos_mbox_create( void )
{
	aos_mcb	*mcb_new; 

	mcb_new = 0;                   	         
	AOS_ENTER_CRITICAL;
	mcb_new = (aos_mcb *)aos_ctbl.mcb_free_list;				/* Save pointer to next free mcb */
	if( mcb_new ) {												/* mcbs left? */
		mcb_new->mmsg = NULL;		//added by BRL to init mailbox
		aos_ctbl.mcb_free_list = (aos_mcb *)mcb_new->next_mcb;	/* Yes, release mcb from freelist */
		mcb_new->next_mcb = (aos_mcb *)aos_ctbl.mcb_used_list;	/* Link new mcb into mcb used list */
		aos_ctbl.mcb_used_list = (aos_mcb *)mcb_new;  
  	mcb_new->mrecv 		= (aos_scb *)aos_sem_create( 0 );			/* Semaphore for receiving messages */                                                                        
  	mcb_new->msend 		= (aos_scb *)aos_sem_create( 1 );			/* Semaphore for sending messages */                                                                        
		mcb_new->mmsg			= (void *)0;													/* Clear message pointer */
	}	                                       
	AOS_EXIT_CRITICAL;
	return( mcb_new );
}

//===================================================================         
/* Send a message to mailbox */
void aos_mbox_send( aos_mcb *mcb, void *msg )
{                                                             
	aos_wait( (aos_scb *)mcb->msend );		/* Is there room in the mailbox */
	mcb->mmsg = msg;						/* Put message in the mailbox */			
	aos_signal( (aos_scb *)mcb->mrecv );	/* Signal the queue's receive semaphore */
}

//===================================================================                             
/* Receive a message from mailbox */
void *aos_mbox_recv( aos_mcb *mcb )
{
	void *msg;          
	
	aos_wait( (aos_scb *)mcb->mrecv );		/* Wait for a message */
	msg = mcb->mmsg;                      	/* Get the message from mailbox */
	mcb->mmsg = NULL;						//and wipe the old message
	aos_signal( (aos_scb *)mcb->msend );	/* Signal the queue's sending semaphore */	

	return( msg );		
}

//=================================================================== 
//receive a message without waiting
//You MUST check the retrun value to see if it is NULL
void *aos_mbox_accept( aos_mcb *mcb )
{
    void *msg;
    AOS_ENTER_CRITICAL;
	msg = mcb->mmsg;               	/* Get the message from mailbox */
    if (msg!=NULL) {				//if there is a message
    	 mcb->mmsg = NULL ;         //clear the mailbox
    	 aos_signal( (aos_scb *)mcb->msend );	/* Signal the sending semaphore */	
    }
    return msg;
    AOS_EXIT_CRITICAL;
}