/* 
 * Copyright (C) 1995 Advanced RISC Machines Limited. All rights reserved.
 * 
 * This software may be freely used, copied, modified, and distributed
 * provided that the above copyright notice is preserved in all copies of the
 * software.
 */

/*-*-C-*-
 *
 * $Revision: 1.2 $
 *     $Date: 1998/01/08 11:12:27 $
 *
 *
 *   Project: ANGEL
 *
 *     Title:  Character reception engine
 */

#include <stdarg.h>    /* ANSI varargs support */
#include "angel.h"     /* Angel system definitions */
#include "endian.h"    /* Endian independant memory access macros */
#include "crc.h"       /* crc generation definitions and headers */
#include "rxtx.h"
#include "channels.h"
#include "buffers.h"
#ifdef TARGET
#  include "devdriv.h"
#endif
#include "logging.h"

static re_status unexp_stx(struct re_state *rxstate);
static re_status unexp_etx(struct re_state *rxstate);

/* bitfield for the rx_engine state */
typedef enum rx_state_flag{
  RST_STX,
  RST_TYP,
  RST_LEN,
  RST_DAT,
  RST_CRC,
  RST_ETX,
  RST_ESC = (0x1 << 0x3)
} rx_state_flag;

void Angel_RxEngineInit(const struct re_config *rxconfig,
                        struct re_state *rxstate)
{
  rxstate->rx_state = RST_STX;
  rxstate->field_c = 0;
  rxstate->index = 0;
  rxstate->crc = 0;
  rxstate->error = RE_OKAY;
  rxstate->config = rxconfig;
}

re_status Angel_RxEngine(unsigned char new_ch, struct data_packet *packet,
                         struct re_state *rxstate)
{
  /*
   * TODO: add the flow control bits in
   * Note: We test for the data field in a seperate case so we can
   * completely avoid entering the switch for most chars
   */

  /* see if we're expecting a escaped char */
  if ((rxstate->rx_state & RST_ESC) == RST_ESC)
  {
    /* unescape the char and unset the flag*/
    new_ch &= ~serial_ESCAPE;
#ifdef DO_TRACE
    __rt_trace("rxe-echar-%2x ", new_ch);
#endif
    rxstate->rx_state &= ~RST_ESC;
  }
  else if ( (1 << new_ch) & rxstate->config->esc_set )
  {
    /* see if the incoming char is a special one */
    if (new_ch == rxstate->config->esc)
    {
#ifdef DO_TRACE
      __rt_trace("rxe-esc ");
#endif
      rxstate->rx_state |= RST_ESC;
      return RS_IN_PKT;
    }
    else
    {
      /*
       * must be a normal packet so do some unexpected etx/stx checking
       * we haven't been told to escape or received an escape so unless
       * we are expecting an stx or etx then we can take the unexpected 
       * stx/etx trap
       */
      if ((new_ch == (rxstate->config->stx)) && (rxstate->rx_state != RST_STX))
        return unexp_stx(rxstate);
      if ((new_ch == (rxstate->config->etx)) && (rxstate->rx_state != RST_ETX))
        return unexp_etx(rxstate);
    }
  }

  if (rxstate->rx_state == RST_DAT)
  {
    /*
     * do this to speed up the common case, no real penalty for
     * other cases 
     */
#ifdef DO_TRACE
    __rt_trace("rxe-dat ");
#endif

    rxstate->crc = crc32(&new_ch, 1, rxstate->crc);
    (packet->data)[rxstate->index++] = (unsigned int)new_ch & 0xff;

    if (rxstate->index == packet->len)
      rxstate->rx_state = RST_CRC;

    return RS_IN_PKT;
  }

  /*
   * Now that the common case is out of the way we can test for everything
   * else without worrying quite so much about the speed, changing the
   * order to len,crc,stx,etx,typ might gain a tiny bit of speed but lets
   * leave that for the moment
   */
  switch (rxstate->rx_state)
  {
    case RST_STX:
      if (new_ch == rxstate->config->stx)
      {
        rxstate->rx_state = RST_TYP;
        rxstate->error = RE_OKAY;
        rxstate->crc = startCRC32;
        rxstate->index = 0;
        return RS_IN_PKT;
      }
      else
      {
        rxstate->error = RE_OKAY;
        return RS_WAIT_PKT;
      }

    case RST_TYP:
      packet->type = (DevChanID)new_ch;
      rxstate->rx_state = RST_LEN;
      rxstate->error = RE_OKAY;
      rxstate->field_c = 0; /* set up here for the length that follows */
#ifdef DO_TRACE 
      __rt_trace("rxe-type-%2x ", packet->type);
#endif
      rxstate->crc = crc32(&new_ch, 1, rxstate->crc);

      return RS_IN_PKT;

    case RST_LEN:
      rxstate->crc = crc32(&new_ch, 1, rxstate->crc);

      if (rxstate->field_c++ == 0)
      {
        /* first length byte */
        packet->len = ((unsigned int)new_ch) << 8;
        return RS_IN_PKT;
      }
      else
      {
        /* got the whole legth */
        packet->len |= new_ch;
#ifdef DO_TRACE
        __rt_trace("rxe-len-%4x\n", packet->len);
#endif

        /* check that the length is ok */
        if (packet->len == 0)
        {
          /* empty pkt */
          rxstate->field_c = 0;
          rxstate->rx_state = RST_CRC;
          return RS_IN_PKT;
        }
        else
        {
          if (packet->data == NULL)
          {
            /* need to alloc the data buffer */
            if (!rxstate->config->ba_callback(
                packet, rxstate->config->ba_data)) {
              rxstate->rx_state = RST_STX;
              rxstate->error = RE_INTERNAL;
              return RS_BAD_PKT;
            }
          }

          if (packet->len > packet->buf_len)
          {
            /* pkt bigger than buffer */
            rxstate->field_c = 0;
            rxstate->rx_state = RST_STX;
            rxstate->error = RE_LEN;
            return RS_BAD_PKT;
          }
          else
          {
            /* packet ok */
            rxstate->field_c = 0;
            rxstate->rx_state = RST_DAT;
            return RS_IN_PKT;
          }
        }
      }

    case RST_DAT:
      /* dummy case (dealt with earlier) */
#ifdef ASSERTIONS_ENABLED
      __rt_warning("ERROR: hit RST_dat in switch\n");
#endif
      rxstate->rx_state = RST_STX;
      rxstate->error = RE_INTERNAL;
      return RS_BAD_PKT;

    case RST_CRC:
      if (rxstate->field_c == 0)
        packet->crc = 0;

      packet->crc |= (new_ch & 0xFF) << ((3 - rxstate->field_c) * 8);
      rxstate->field_c++;

      if (rxstate->field_c == 4)
      {
        /* last crc field */
        rxstate->field_c = 0;
        rxstate->rx_state = RST_ETX;
#ifdef DO_TRACE
        __rt_trace("rxe-rcrc-%8x ", packet->crc);
#endif
      }

      return RS_IN_PKT;

    case RST_ETX:
      if (new_ch == rxstate->config->etx)
      {
#if defined(DEBUG) && !defined(NO_PKT_DATA)
        {
          int c;
# ifdef DO_TRACE
          __rt_trace("\n");
# endif
          __rt_info("RXE Data =");
          for (c=0; c < packet->len; c++)
            __rt_info("%02x", packet->data[c]);
          __rt_info("\n"); 
        }
#endif

        /* check crc */
        if (rxstate->crc == packet->crc)
        {
          /* crc ok */
          rxstate->rx_state = RST_STX;
          rxstate->field_c = 0;
          return RS_GOOD_PKT;
        }
        else
        {
#ifdef ASSERTIONS_ENABLED
          __rt_warning("Bad crc, rx calculates it should be 0x%x\n", rxstate->crc);
#endif
          rxstate->rx_state = RST_STX;
          rxstate->error = RE_CRC;
          return RS_BAD_PKT;
        }
      }
      else if (new_ch == rxstate->config->stx)
        return unexp_stx(rxstate);
      else
      {
        rxstate->rx_state = RST_STX;
        rxstate->error = RE_NETX;
        return RS_BAD_PKT;
      }

    default:
#ifdef ASSERTIONS_ENABLED
      __rt_warning("ERROR fell through rxengine\n");
#endif
      rxstate->rx_state = RST_STX;
      rxstate->error = RE_INTERNAL;
      return RS_BAD_PKT;
  }
}

static re_status unexp_stx(struct re_state *rxstate)
{
#ifdef ASSERTIONS_ENABLED
  __rt_warning("Unexpected stx\n");
#endif
  rxstate->crc = startCRC32;
  rxstate->index = 0;
  rxstate->rx_state = RST_TYP;
  rxstate->error = RE_U_STX;
  rxstate->field_c = 0;
  return RS_BAD_PKT;
}

static re_status unexp_etx(struct re_state *rxstate)
{
#ifdef ASSERTIONS_ENABLED
  __rt_warning("Unexpected etx, rxstate: index= 0x%2x, field_c=0x%2x, state=0x%2x\n", rxstate->index, rxstate->field_c, rxstate->rx_state);
#endif
  rxstate->crc = 0;
  rxstate->index = 0;
  rxstate->rx_state = RST_STX;
  rxstate->error = RE_U_ETX;
  rxstate->field_c = 0;
  return RS_BAD_PKT;
}

/*
 * This can be used as the buffer allocation callback for the rx engine,
 * and makes use of angel_DD_GetBuffer() [in devdrv.h]. 
 *
 * Saves duplicating this callback function in every device driver that
 * uses the rx engine.
 *
 * Note that this REQUIRES that the device id is installed as ba_data
 * in the rx engine config structure for the driver.
 */
bool angel_DD_RxEng_BufferAlloc( struct data_packet *packet, void *cb_data )
{
#ifdef TARGET
    DeviceID devid = (DeviceID)cb_data;
#else
    IGNORE(cb_data);
#endif

    if ( packet->type < DC_NUM_CHANNELS )
    {
        /* request a buffer down from the channels layer */
#ifdef TARGET
        packet->data = angel_DD_GetBuffer( devid, packet->type,
                                           packet->len              );
#else
        packet->data = malloc(packet->len);
#endif
        if ( packet->data == NULL )
           return FALSE;
        else
        {
            packet->buf_len = packet->len;
            return TRUE;
        }
    }
    else
    {
        /* bad type field */
        return FALSE;
    }
}

/* EOF rx.c */