/* Hey EMACS -*- linux-c -*- */

/*  libcalccables - link cable library, a part of the CalcForge project
 *  Copyright (C) 1999-2005  Romain Lievin
 *
 *  This program 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.
 *
 *  This program 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 this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

/* "VTi" virtual link cable unit */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

/* 
   This part use Shared Memory Segment for implementing two circular buffers
   between 2 program which use this lib. Each segment is attached 2 times.
   Convention used: 0 is an emulator and 1 is a linking program.
   One shm is used for transferring information from 0 to 1 and the other
   shm is used for transferring from 1 to 0.
   shm0: W -> R
   shm1: R <- W
*/

#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>

#include "../calccables.h"
#include "../logging.h"
#include "../error.h"
#include "../gettext.h"
#include "detect.h"

#define BUF_SIZE 1*1024

/* Circular buffer (0: Emu-TIGCC, 1: CalcForgeLP) */
typedef struct
{
    uint8_t buf[BUF_SIZE];
    int start;
    int end;
} LinkBuffer;

/* Shm variables */
static key_t ipc_key[2];	// IPC key
static int shmid[2];		// Shm ID
static LinkBuffer *shm[2];	// Shm address

static LinkBuffer* send_buf[2];	// Swapped buffer
static LinkBuffer* recv_buf[2];

static int vti_prepare(CableHandle *h)
{
    // in fact, address & device are unused
    switch(h->port)
    {
    case PORT_0:	// automatic setting
	h->address = 0; //ref_cnt;
	break;
    case PORT_1:	// forced setting, for compatibility
    case PORT_3: 
	h->address = 0; h->device = strdup("0->1"); 
	break;
    case PORT_2:
    case PORT_4:
	h->address = 1; h->device = strdup("1->0"); 
	break;
    default: return ERR_ILLEGAL_ARG;
    }
    
    return 0;
}

static int vti_open(CableHandle *h)
{
    int i;
    
    /* Get a unique (if possible) key */
    for (i = 0; i < 2; i++) 
    {
	if ((ipc_key[i] = ftok("/tmp", i)) == -1) 
	{
	    calccables_warning("unable to get unique key (ftok).\n");
	    return ERR_VTI_IPCKEY;
	}
    }
    
    /* Open a shared memory segment */
    for (i = 0; i < 2; i++) 
    {
	if ((shmid[i] = shmget(ipc_key[i], sizeof(LinkBuffer), 
			       IPC_CREAT | 0666)) == -1) 
	{
	    calccables_warning("unable to open shared memory (shmget).\n");
	    return ERR_VTI_SHMGET;
	}
    }
    
    /* Attach the shm */
    for (i = 0; i < 2; i++) 
    {
	if ((shm[i] = shmat(shmid[i], NULL, 0)) == NULL) 
	{
	    calccables_warning("unable to attach shared memory (shmat).\n");
	    return ERR_VTI_SHMAT;
	}
    }
    
    /* Swap shm */
    send_buf[0] = shm[0];		// 0 -> 1: writing
    recv_buf[0] = shm[1];		// 0 <- 1: reading
    send_buf[1] = shm[1];		// 1 -> 0: writing
    recv_buf[1] = shm[0];		// 1 <- 0: reading

    for (i = 0; i < 2; i++)
	shm[i]->start = shm[i]->end = 0;

    return 0;
}

static int vti_close(CableHandle *h)
{
    int i;
    
    /* Detach segment */
    for (i = 0; i < 2; i++) 
    {
	if (shmdt(shm[i]) == -1) 
	{
	    calccables_warning("shmdt\n");
	    return ERR_VTI_SHMDT;
	}
	
	/* and destroy it */
	if (shmctl(shmid[i], IPC_RMID, NULL) == -1) 
	{
	    calccables_warning("shmctl\n");
	    return ERR_VTI_SHMCTL;
	}
    }
    
    return 0;
}

static int vti_reset(CableHandle *h)
{
	int i;
	
	for (i = 0; i < 2; i++) 
	    shm[i]->start = shm[i]->end = 0;
	
	return 0;
}

static int vti_put(CableHandle *h, uint8_t *data, uint32_t len)
{
    int p = h->address;
    int i;
    tiTIME clk;
    
    for(i = 0; i < len; i++)
    {
	TO_START(clk);
	do 
	{
	    if (TO_ELAPSED(clk, h->timeout))
		return ERR_WRITE_TIMEOUT;
	}
	while (((send_buf[p]->end + 1) & 255) == send_buf[p]->start);
	
	send_buf[p]->buf[send_buf[p]->end] = data[i];
	send_buf[p]->end = (send_buf[p]->end + 1) & 255;
    }
    
    return 0;
}

static int vti_get(CableHandle *h, uint8_t *data, uint32_t len)
{
    int p = h->address;
    int i;
    tiTIME clk;
    
    for(i = 0; i < len; i++)
    {
	TO_START(clk);
	do 
	{
	    if (TO_ELAPSED(clk, h->timeout))
		return ERR_READ_TIMEOUT;
	}
	while (recv_buf[p]->start == recv_buf[p]->end);
	
	
	data[i] = recv_buf[p]->buf[recv_buf[p]->start];
	recv_buf[p]->start = (recv_buf[p]->start + 1) & 255;
    }
    
    return 0;
}

static int vti_probe(CableHandle *h)
{
	return 0;
}

static int vti_check(CableHandle *h, int *status)
{
    int p = h->address;
    *status = !(recv_buf[p]->start == recv_buf[p]->end);
    return 0;
}

static int vti_set_red_wire(CableHandle *h, int b)
{
	return 0;
}

static int vti_set_white_wire(CableHandle *h, int b)
{
	return 0;
}

static int vti_get_red_wire(CableHandle *h)
{
	return 1;
}

static int vti_get_white_wire(CableHandle *h)
{
	return 1;
}

const CableFncts cable_vti = 
{
	CABLE_VTI,
	"VTI",
	N_("Virtual TI"),
	N_("Virtual link for VTi"),
	0,
	&vti_prepare,
	&vti_open, &vti_close, &vti_reset, &vti_probe, NULL,
	&vti_put, &vti_get, &vti_check,
	&vti_set_red_wire, &vti_set_white_wire,
	&vti_get_red_wire, &vti_get_white_wire,
};