/*
 * Copyright (c) 2004, Yannick Verschueren
 * Copyright (c) 2004, Communications and remote sensing Laboratory, Universite catholique de Louvain, Belgium
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS `AS IS'
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <stdio.h>
#include <stdlib.h>

#include "cio.h"


/*
 * Read the information contains in VBAS [JPP/JPT stream message header]
 * Store information (7 bits) in value
 *
 */ 
unsigned int jpt_read_VBAS_info(unsigned int value)
{
  char elmt;

  elmt = cio_read(1);
  while ((elmt >> 7) == 1)
    {
      value = value << 7;
      value |= (elmt & 0x7f);
      elmt = cio_read(1);
    }
  value = value << 7;
  value |= (elmt & 0x7f);
  
  return value;
}

/*
 * Read the message header for a JPP/JPT - stream
 *
 */
void jpt_read_Msg_Header()
{
  char elmt, Class, CSn, last_byte, Aux;
  unsigned int ID=0, Class_ID=0, CSn_ID=0, Msg_offset=0, Msg_length=0, Layer_nb;
  
  /* ------------- */
  /* VBAS : Bin-ID */
  /* ------------- */
  elmt = cio_read(1);
  
  /* See for Class and CSn */
  switch((elmt>>5) & 0x03) 
    {
    case 0:
      fprintf(stderr,"Forbidden value encounter in message header !!\n");
      break;
    case 1:
      Class = 0;
      CSn = 0;
      break;
    case 2:
      Class = 1;
      CSn = 0;
      break;
    case 3:
      Class = 1;
      CSn = 1;
      break;
    default :
      break;
    }
  
  /* see information on bits 'c' [p 10 : A.2.1 general, ISO/IEC FCD 15444-9] */ 
  if (((elmt>>3) & 0x01) == 1)
    last = 1;

  /* In-class identifier */
  ID |= (elmt & 0x0f);
  if ((elmt>>7)==1)
    ID = jpt_read_VBAS_info(ID);
  
  /* ------------ */
  /* VBAS : Class */
  /* ------------ */
  if (Class==1)
    {
      Class_ID = jpt_read_VBAS_info(Class_ID);
    } else
      {
	/* 0 si pas de precedent message */
	/* inchange sinon */
      }

  /* ---------- */
  /* VBAS : CSn */
  /* ---------- */
  if (CSn==1)
    {
      CSn_ID = jpt_read_VBAS_info(CSn_ID);
    } else
      {
	/* 0 si pas de precedent message */
	/* inchange sinon */
      }

  /* ----------------- */
  /* VBAS : Msg_offset */
  /* ----------------- */
  Msg_offset = jpt_read_VBAS_info(Msg_offset);

  /* ----------------- */
  /* VBAS : Msg_length */
  /* ----------------- */
  Msg_length = jpt_read_VBAS_info(Msg_length);

  /* ---------- */
  /* VBAS : Aux */
  /* ---------- */  
  if (CSn_ID == 1)
    Layer_nb = jpt_read_VBAS_info(Layer_nb);
}