/****************************************************************************
 * apps/system/zmodem/zm_proto.c
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The
 * ASF licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the
 * License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 ****************************************************************************/

/* References:
 *   "The ZMODEM Inter Application File Transfer Protocol", Chuck Forsberg,
 *    Omen Technology Inc., October 14, 1988
 */

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <stdio.h>
#include <crc16.h>
#include <crc32.h>

#include "zm.h"

/****************************************************************************
 * Public Data
 ****************************************************************************/

/* Paragraph 8.4.  Session Abort Sequence
 *
 * "If the receiver is receiving data in streaming mode, the Attn sequence
 *  is executed to interrupt data transmission before the Cancel sequence is
 *  sent.  The Cancel sequence consists of eight CAN characters and ten
 *  backspace characters.  ZMODEM only requires five Cancel characters, the
 *  other three are "insurance".
 *
 * "The trailing backspace characters attempt to erase the effects of the
 *  CAN characters if they are received by a command interpreter.
 */

const uint8_t g_canistr[CANISTR_SIZE] =
{
  /* Eight CAN characters */

  ASCII_CAN, ASCII_CAN, ASCII_CAN, ASCII_CAN, ASCII_CAN, ASCII_CAN,
  ASCII_CAN, ASCII_CAN,

  /* Ten backspace characters */

  ASCII_BS,  ASCII_BS,  ASCII_BS,  ASCII_BS,  ASCII_BS,  ASCII_BS,
  ASCII_BS,  ASCII_BS,  ASCII_BS,  ASCII_BS
};

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: zm_putzdle
 *
 * Description:
 *   Transfer a value to a buffer performing ZDLE escaping if necessary.
 *
 * Input Parameters:
 *   pzm - Zmodem session state
 *   buffer - Buffer in which to add the possibly escaped character
 *   ch - The raw, unescaped character to be added
 *
 ****************************************************************************/

FAR uint8_t *zm_putzdle(FAR struct zm_state_s *pzm, FAR uint8_t *buffer,
                        uint8_t ch)
{
  uint8_t ch7 = ch & 0x7f;

  /* Check if this character requires ZDLE escaping.
   *
   * The Zmodem protocol requires that CAN(ZDLE), DLE, XON, XOFF and a CR
   * following '@' be escaped.
   */

  if (ch   == ZDLE ||
      ch7  == ASCII_DLE ||
      ch7  == ASCII_DC1 ||
      ch7  == ASCII_DC3 ||
      ch7  == ASCII_GS ||
      (ch7 == '\r' && (pzm->flags & ZM_FLAG_ATSIGN)  != 0) ||
      (ch7 <  ' '  && (pzm->flags & ZM_FLAG_ESCCTRL) != 0) ||
      ch7  == ASCII_DEL ||
      ch   == 0xff
      )
    {
      /* Yes... save the data link escape the character */

      *buffer++ = ZDLE;

      /* And modify the character itself as appropriate  */

      if (ch == ASCII_DEL)
        {
          ch = ZRUB0;
        }
      else if (ch == 0xff)
        {
          ch = ZRUB1;
        }
      else
        {
          ch ^= 0x40;
        }
    }

  /* Save the possibly escaped character */

  *buffer++ = ch;

  /* Check if the character is the AT sign */

  if (ch7 == '@')
    {
      pzm->flags |= ZM_FLAG_ATSIGN;
    }
  else
    {
      pzm->flags &= ~ZM_FLAG_ATSIGN;
    }

  return buffer;
}

/****************************************************************************
 * Name: zm_senddata
 *
 * Description:
 *   Send data to the remote peer performing CRC operations as required
 *   (ZBIN or ZBIN32 format assumed, ZCRCW terminator is always used)
 *
 * Input Parameters:
 *   pzm    - Zmodem session state
 *   buffer - Buffer of data to be sent
 *   buflen - The number of bytes in buffer to be sent
 *
 ****************************************************************************/

int zm_senddata(FAR struct zm_state_s *pzm, FAR const uint8_t *buffer,
                size_t buflen)
{
  uint8_t *ptr = pzm->scratch;
  ssize_t nwritten;
  uint32_t crc;
  uint8_t zbin;
  uint8_t term;
  int i;

  /* Make select ZBIN or ZBIN32 format and the ZCRCW terminator */

  if ((pzm->flags & ZM_FLAG_CRC32) != 0)
    {
      zbin = ZBIN32;
      crc  = 0xffffffff;
    }
  else
    {
      zbin = ZBIN;
      crc  = 0;
    }

  term = ZCRCW;
  zmdbg("zbin=%c, buflen=%zu, term=%c flags=%04x\n",
        zbin, buflen, term, pzm->flags);

  /* Transfer the data to the I/O buffer, accumulating the CRC */

  while (buflen-- > 0)
    {
      if (zbin == ZBIN)
        {
          crc = (uint32_t)crc16part(buffer, 1, (uint16_t)crc);
        }
      else /* zbin = ZBIN32 */
        {
          crc = crc32part(buffer, 1, crc);
        }

      ptr = zm_putzdle(pzm, ptr, *buffer++);
    }

  /* Trasnfer the data link escape character (without updating the CRC) */

  *ptr++ = ZDLE;

  /* Transfer the terminating character, updating the CRC */

  if (zbin == ZBIN)
    {
      crc = crc16part((FAR const uint8_t *)&term, 1, crc);
    }
  else
    {
      crc = crc32part((FAR const uint8_t *)&term, 1, crc);
    }

  *ptr++ = term;

  /* Calculate and transfer the final CRC value */

  if (zbin == ZBIN)
    {
      ptr = zm_putzdle(pzm, ptr, (crc >> 8) & 0xff);
      ptr = zm_putzdle(pzm, ptr, crc & 0xff);
    }
  else
    {
      crc = ~crc;
      for (i = 0; i < 4; i++, crc >>= 8)
        {
          ptr = zm_putzdle(pzm, ptr, crc & 0xff);
        }
    }

  /* Send the header */

  nwritten = zm_remwrite(pzm->remfd, pzm->scratch, ptr - pzm->scratch);
  return nwritten < 0 ? (int)nwritten : OK;
}

/****************************************************************************
 * Name: zm_sendhexhdr
 *
 * Description:
 *   Send a ZHEX header to the remote peer performing CRC operations as
 *   necessary.
 *
 *   Hex header:
 *     ZPAD ZPAD ZDLE ZHEX type f3/p0 f2/p1 f1/p2 f0/p3 crc1 crc2 CR LF [XON]
 *     Payload length: 16 (14 hex digits, cr, lf, ignoring optional XON)
 *
 * Input Parameters:
 *   pzm    - Zmodem session state
 *   type   - Header type {ZRINIT, ZRQINIT, ZDATA, ZACK, ZNAK, ZCRC, ZRPOS,
 *            ZCOMPL, ZEOF, ZFIN}
 *   buffer - 4-byte buffer of data to be sent
 *
 * Assumptions:
 *   The allocated I/O buffer is available to buffer file data.
 *
 ****************************************************************************/

int zm_sendhexhdr(FAR struct zm_state_s *pzm, int type,
                  FAR const uint8_t *buffer)
{
  FAR uint8_t *ptr;
  ssize_t nwritten;
  uint16_t crc;
  int i;

  zmdbg("Sending type %d: %02x %02x %02x %02x\n",
       type, buffer[0], buffer[1], buffer[2], buffer[3]);

  /* ZPAD ZPAD ZDLE ZHEX */

  ptr = pzm->scratch;
  *ptr++ = ZPAD;
  *ptr++ = ZPAD;
  *ptr++ = ZDLE;
  *ptr++ = ZHEX;

  /* type */

  crc = crc16part((FAR const uint8_t *)&type, 1, 0);
  ptr = zm_puthex8(ptr, type);

  /* f3/p0 f2/p1 f1/p2 f0/p3 */

  crc = crc16part(buffer, 4, crc);
  for (i = 0; i < 4; i++)
    {
      ptr = zm_puthex8(ptr, *buffer++);
    }

  /* crc-1 crc-2 */

  ptr = zm_puthex8(ptr, (crc >> 8) & 0xff);
  ptr = zm_puthex8(ptr, crc & 0xff);

  /* CR LF */

  *ptr++ = '\r';
  *ptr++ = '\n';

  /* [XON] */

  if (type != ZACK && type != ZFIN)
    {
      *ptr++ = ASCII_XON;
    }

  /* Send the header */

  nwritten = zm_remwrite(pzm->remfd, pzm->scratch, ptr - pzm->scratch);
  return nwritten < 0 ? (int)nwritten : OK;
}

/****************************************************************************
 * Name: zm_sendbin16hdr
 *
 * Description:
 *   Send a ZBIN header to the remote peer performing CRC operations as
 *   necessary.  Normally called indirectly through zm_sendbinhdr().
 *
 *   16-bit binary header:
 *     ZPAD ZDLE ZBIN type f3/p0 f2/p1 f1/p2 f0/p3 crc-1 crc-2
 *     Payload length: 7 (type, 4 bytes data, 2 byte CRC)
 *
 * Input Parameters:
 *   pzm    - Zmodem session state
 *   type   - Header type {ZSINIT, ZFILE, ZDATA, ZDATA}
 *   buffer - 4-byte buffer of data to be sent
 *
 * Assumptions:
 *   The allocated I/O buffer is available to buffer file data.
 *
 ****************************************************************************/

int zm_sendbin16hdr(FAR struct zm_state_s *pzm, int type,
                    FAR const uint8_t *buffer)
{
  FAR uint8_t *ptr;
  ssize_t nwritten;
  uint16_t crc;
  int buflen;
  int i;

  zmdbg("Sending type %d: %02x %02x %02x %02x\n",
       type, buffer[0], buffer[1], buffer[2], buffer[3]);

  /* XPAD ZDLE ZBIN */

  ptr    = pzm->scratch;
  *ptr++ = ZPAD;
  *ptr++ = ZDLE;
  *ptr++ = ZBIN;

  /* type */

  crc = crc16part((FAR const uint8_t *)&type, 1, 0);
  ptr = zm_putzdle(pzm, ptr, type);

  /* f3/p0 f2/p1 f1/p2 f0/p3 */

  crc = crc16part(buffer, 4, crc);
  for (i = 0; i < 4; i++)
    {
      ptr = zm_putzdle(pzm, ptr, *buffer++);
    }

  /* crc-1 crc-2 */

  ptr = zm_putzdle(pzm, ptr, (crc >> 8) & 0xff);
  ptr = zm_putzdle(pzm, ptr, crc & 0xff);

  /* Send the header */

  buflen   = ptr - pzm->scratch;
  nwritten = zm_remwrite(pzm->remfd, pzm->scratch, buflen);
  return nwritten < 0 ? (int)nwritten : OK;
}

/****************************************************************************
 * Name: zm_sendbin32hdr
 *
 * Description:
 *   Send a ZBIN32 header to the remote peer performing CRC operations as
 *   necessary.  Normally called indirectly through zm_sendbinhdr().
 *
 *   32-bit inary header:
 *     ZPAD ZDLE ZBIN32 type f3/p0 f2/p1 f1/p2 f0/p3 crc-1 crc-2 crc-3 crc-4
 *     Payload length: 9 (type, 4 bytes data, 4 byte CRC)
 *
 * Input Parameters:
 *   pzm    - Zmodem session state
 *   type   - Header type {ZSINIT, ZFILE, ZDATA, ZDATA}
 *   buffer - 4-byte buffer of data to be sent
 *
 * Assumptions:
 *   The allocated I/O buffer is available to buffer file data.
 *
 ****************************************************************************/

int zm_sendbin32hdr(FAR struct zm_state_s *pzm, int type,
                    FAR const uint8_t *buffer)
{
  FAR uint8_t *ptr;
  ssize_t nwritten;
  uint32_t crc;
  int buflen;
  int i;

  zmdbg("Sending  type %d: %02x %02x %02x %02x\n",
        type, buffer[0], buffer[1], buffer[2], buffer[3]);

  /* XPAD ZDLE ZBIN32 */

  ptr = pzm->scratch;
  *ptr++ = ZPAD;
  *ptr++ = ZDLE;
  *ptr++ = ZBIN32;

  /* type */

  ptr = zm_putzdle(pzm, ptr, type);
  crc = crc32part((FAR const uint8_t *)&type, 1, 0xffffffffl);

  /* f3/p0 f2/p1 f1/p2 f0/p3 */

  crc = crc32part(buffer, 4, crc);
  for (i = 0; i < 4; i++)
    {
      ptr = zm_putzdle(pzm, ptr, *buffer++);
    }

  /* crc-1 crc-2 crc-3 crc-4 */

  crc = ~crc;
  for (i = 0; i < 4; i++, crc >>= 8)
    {
      ptr = zm_putzdle(pzm, ptr, crc & 0xff);
    }

  /* Send the header */

  buflen   = ptr - pzm->scratch;
  nwritten = zm_remwrite(pzm->remfd, pzm->scratch, buflen);
  return nwritten < 0 ? (int)nwritten : OK;
}

/****************************************************************************
 * Name: zm_sendbinhdr
 *
 * Description:
 *   Send a binary header to the remote peer.  This is a simple wrapper
 *   function for zm_sendbin16hdr() and zm_sendbin32hdr().  It decides on
 *   the correct CRC format and re-directs the call appropriately.
 *
 * Input Parameters:
 *   pzm    - Zmodem session state
 *   type   - Header type {ZSINIT, ZFILE, ZDATA, ZDATA}
 *   buffer - 4-byte buffer of data to be sent
 *
 * Assumptions:
 *   The allocated I/O buffer is available to buffer file data.
 *
 ****************************************************************************/

int zm_sendbinhdr(FAR struct zm_state_s *pzm, int type,
                  FAR const uint8_t *buffer)
{
  if ((pzm->flags & ZM_FLAG_CRC32) == 0)
    {
      return zm_sendbin16hdr(pzm, type, buffer);
    }
  else
    {
      return zm_sendbin32hdr(pzm, type, buffer);
    }
}