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/*

 * 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: 1.1.1.1 $

 *     $Date: 2001-05-18 11:16:46 $

 *

 *   Project: ANGEL

 *

 *     Title: Character based packet transmission engine

 */

#include <stdarg.h>    /* ANSI varargs support */

#include "angel.h"     /* Angel system definitions */

#include "angel_endian.h"    /* Endian independant memory access macros */

#include "crc.h"       /* crc generation definitions and headers */

#include "rxtx.h"

#include "channels.h"

#include "buffers.h"

#include "logging.h"

/* definitions to describe the engines state */

#define N_STX           0x0  /* first 2 bits for N_ */

#define N_BODY          0x1

#define N_ETX           0x2

#define N_IDLE          0x3

#define N_MASK          0x3 /* mask for the Encapsulator state */

#define E_PLAIN         (0x0 << 2) /* 3rd bit for E_ */

#define E_ESC           (0x1 << 2) /* 3rd bit for E_ */

#define E_MASK          (0x1 << 2) /* mask for the Escaper state */

#define F_HEAD          (0x0 << 3) /* 4th and 5th bits for F_ */

#define F_DATA          (0x1 << 3) 

#define F_CRC           (0x1 << 4)

#define F_MASK          (0x3 << 3) /* mask for the Escaper state */

static unsigned char escape(unsigned char ch_in, struct te_state *txstate);

void Angel_TxEngineInit(const struct re_config *txconfig,

                        const struct data_packet *packet,

                        struct te_state *txstate){

  IGNORE(packet);

  txstate->tx_state = N_STX | E_PLAIN | F_HEAD;

  txstate->field_c = 0;

  txstate->encoded = 0;

  txstate->config = txconfig;

  txstate->crc = 0;

}

te_status Angel_TxEngine(const struct data_packet *packet,

                         struct te_state *txstate,

                         unsigned char *tx_ch){

  /* TODO: gaurd on long/bad packets */

  /*

   * encapsulate the packet, framing has been moved from a seperate

   * function into the encapsulation routine as it needed too much

   * inherited state for it to be sensibly located elsewhere

   */

  switch ((txstate->tx_state) & N_MASK){

  case N_STX:

#ifdef DO_TRACE

    __rt_trace("txe-stx ");

#endif

    txstate->tx_state = (txstate->tx_state & ~N_MASK) | N_BODY;

    *tx_ch = txstate->config->stx;

    txstate->field_c = 3; /* set up for the header */

    txstate->crc = startCRC32; /* set up basic crc */

    return TS_IN_PKT;

  case N_BODY:{

    switch (txstate->tx_state & F_MASK) {

    case F_HEAD:

#ifdef DO_TRACE

    __rt_trace("txe-head ");

#endif

      if (txstate->field_c == 3) {

        /* send type */

        *tx_ch = escape(packet->type, txstate);

        return TS_IN_PKT;

      }

      else {

        *tx_ch = escape((packet->len >> (txstate->field_c - 1) * 8) & 0xff,

                      txstate);

          if (txstate->field_c == 0) {

            /* move on to the next state */

            txstate->tx_state = (txstate->tx_state & ~F_MASK) | F_DATA;

            txstate->field_c = packet->len;

          }

        return TS_IN_PKT;

      }

    case F_DATA:

#ifdef DO_TRACE

    __rt_trace("txe-data ");

#endif

      *tx_ch = escape(packet->data[packet->len - txstate->field_c], txstate);

      if (txstate->field_c == 0) {

        /* move on to the next state */

        txstate->tx_state = (txstate->tx_state & ~F_MASK) | F_CRC;

        txstate->field_c = 4;

      }

      return TS_IN_PKT;

    case F_CRC:

#ifdef DO_TRACE

    __rt_trace("txe-crc ");

#endif

     *tx_ch = escape((txstate->crc >> ((txstate->field_c - 1) * 8)) & 0xff,

                      txstate);

      if (txstate->field_c == 0) {

#ifdef DO_TRACE

        __rt_trace("txe crc = 0x%x\n", txstate->crc);

#endif

        /* move on to the next state */

        txstate->tx_state = (txstate->tx_state & ~N_MASK) | N_ETX;

      }

      return TS_IN_PKT;

    }

  }

  case N_ETX:

#ifdef DO_TRACE

    __rt_trace("txe-etx\n");

#endif

    txstate->tx_state = (txstate->tx_state & ~N_MASK) | N_IDLE;

    *tx_ch = txstate->config->etx;

    return TS_DONE_PKT;

  default:

#ifdef DEBUG

    __rt_info("tx default\n");

#endif

    txstate->tx_state = (txstate->tx_state & ~N_MASK) | N_IDLE;

    return TS_IDLE;

  }

  /* stop a silly -Wall warning */

  return (te_status)-1;

}

/*

 * crc generation occurs in the escape function because it is the only

 * place where we know that we're putting a real char into the buffer

 * rather than an escaped one.

 * We must be careful here not to update the crc when we're sending it

 */

static unsigned char escape(unsigned char ch_in, struct te_state *txstate) {

   if (((txstate->tx_state) & E_MASK) == E_ESC) {

      /* char has been escaped so send the real char */

#ifdef DO_TRACE

     __rt_trace("txe-echar ");

#endif

      txstate->tx_state = (txstate->tx_state & ~E_MASK) | E_PLAIN;

      txstate->field_c--;

      if ((txstate->tx_state & F_MASK) != F_CRC)

        txstate->crc = crc32( &ch_in, 1, txstate->crc);

      return ch_in | serial_ESCAPE;

   }

   if ((ch_in < 32) && ((txstate->config->esc_set & (1 << ch_in)) != 0)) {

     /* char needs escaping */

#ifdef DO_TRACE

     __rt_trace("txe-esc ");

#endif

     txstate->tx_state = (txstate->tx_state & ~E_MASK) | E_ESC;

     return txstate->config->esc;

   }

   /* must be a char that can be sent plain */

   txstate->field_c--;

   if ((txstate->tx_state & F_MASK) != F_CRC)

     txstate->crc = crc32(&ch_in, 1, txstate->crc);

   return ch_in;

}

/* EOF tx.c */