/*
    SimOSConsole.c, Copyright  (c) by 
    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.
*/
/*
	
	File:                  $Source: /usr/drwho/vault/cvs/topsy/Topsy/IO/Drivers/SimOSConsole.c,v $
 	Author(s):             
 	Affiliation:           ETH Zuerich, TIK
 	Version:               $Revision: 1.4 $
 	Creation Date:         
 	Last Date of Change:   $Date: 1999/12/13 21:48:26 $      by: $Author: ruf $
	
	
	$Log: SimOSConsole.c,v $
	Revision 1.4  1999/12/13 21:48:26  ruf
	GNU General Public Licence Update
	
	Revision 1.3  1999/10/31 14:42:45  jeker
	first fixes for SimOS
	
	Revision 1.2  1999/10/23 14:19:44  jeker
	first cleanup for R4k support

*/

#include "Drivers/SimOSConsole.h"
#include "Messages.h"
#include "IODevice.h"

#define CONSOLE_BUFFER_SIZE 128

/* There is no reason why this should not be static. BTW, read_pos and
 * write_pos store the total number of characters read/written, which,
 * theoretically, is a bug (as they may overflow), but, in practice, I
 * doubt anyone is going to ever send 2GB of characters in a single session,
 * and the code is much cleaner this way. -- PZ */
static char console_buffer[CONSOLE_BUFFER_SIZE];
static int  read_pos = 0, write_pos = 0;

/* Interrupt handler. */
void simos_console_handler(IODevice this) 
{
	if (write_pos - read_pos >= CONSOLE_BUFFER_SIZE)
		WARNING("Console buffer overflow\n");
	else {
		console_buffer[write_pos++ % CONSOLE_BUFFER_SIZE]
			= simos_console->data;
	}
}

/* Initialization routine. */
Error simos_console_init(IODevice this) 
{
	simos_console->intr_status = CONS_INT_RX; /* Enable console interrupts. */
	return IO_INITOK;
}

/* Read data from the buffer. */
Error simos_console_read(IODevice this, ThreadId threadId, 
		char* buffer, long int* size) 
{
	int i = 0;

	while (read_pos < write_pos && write_pos - read_pos < *size)
		buffer[i++] = console_buffer[read_pos++ % CONSOLE_BUFFER_SIZE];
	*size = i;
	return IO_READOK;
}


Error simos_console_write(IODevice this, ThreadId threadId,
		char* buffer, long int* size) 
{
	while ((*size) > 0) {
		simos_console->data = *buffer++;
		--*size;
	}
	return IO_WRITEOK;
}

Error simos_console_close(IODevice this) 
{
	/* this message is forwarded from ioThread */

	/* release buffers if any */

	/* disable console interrupts */
	simos_console->intr_status = 0;

	return IO_CLOSEOK;
}