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/*
* slip.c
* ------
* SLIP send/recv code, based on RFC 1055
*
* Copyright (c) 2016, NORDUnet A/S All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
* - Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* - 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.
*
* - Neither the name of the NORDUnet nor the names of its contributors may
* be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* 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
* HOLDER 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 "slip_internal.h"
/* SLIP special character codes
*/
#define END 0300 /* indicates end of packet */
#define ESC 0333 /* indicates byte stuffing */
#define ESC_END 0334 /* ESC ESC_END means END data byte */
#define ESC_ESC 0335 /* ESC ESC_ESC means ESC data byte */
#ifndef HAL_SLIP_DEBUG
#define HAL_SLIP_DEBUG 0
#endif
#if HAL_SLIP_DEBUG
#include <stdio.h>
#define check(op) do { const hal_error_t _err_ = (op); if (_err_ != HAL_OK) { printf("%s returned %d (%s)\n", #op, _err_, hal_error_string(_err_)); return _err_; } } while (0)
#else
#define check(op) do { const hal_error_t _err_ = (op); if (_err_ != HAL_OK) { return _err_; } } while (0)
#endif
/* Send a single character with SLIP escaping.
*/
hal_error_t hal_slip_send_char(const uint8_t c)
{
switch (c) {
case END:
check(hal_serial_send_char(ESC));
check(hal_serial_send_char(ESC_END));
break;
case ESC:
check(hal_serial_send_char(ESC));
check(hal_serial_send_char(ESC_ESC));
break;
default:
check(hal_serial_send_char(c));
}
return HAL_OK;
}
/* Send a message with SLIP framing.
*/
hal_error_t hal_slip_send(const uint8_t * const buf, const size_t len)
{
/* send an initial END character to flush out any data that may
* have accumulated in the receiver due to line noise
*/
check(hal_serial_send_char(END));
/* for each byte in the packet, send the appropriate character
* sequence
*/
for (size_t i = 0; i < len; ++i) {
hal_error_t ret;
if ((ret = hal_slip_send_char(buf[i])) != HAL_OK)
return ret;
}
/* tell the receiver that we're done sending the packet
*/
check(hal_serial_send_char(END));
return HAL_OK;
}
/* Receive a single character into a buffer, with SLIP un-escaping
*/
hal_error_t hal_slip_process_char(uint8_t c, uint8_t * const buf, size_t * const len, const size_t maxlen, int * const complete)
{
#define buf_push(c) do { if (*len < maxlen) buf[(*len)++] = c; } while (0)
static int esc_flag = 0;
*complete = 0;
switch (c) {
case END:
if (*len)
*complete = 1;
break;
case ESC:
esc_flag = 1;
break;
default:
if (esc_flag) {
esc_flag = 0;
switch (c) {
case ESC_END:
buf_push(END);
break;
case ESC_ESC:
buf_push(ESC);
break;
default:
buf_push(c);
}
}
else {
buf_push(c);
}
break;
}
return HAL_OK;
}
hal_error_t hal_slip_recv_char(uint8_t * const buf, size_t * const len, const size_t maxlen, int * const complete)
{
uint8_t c;
check(hal_serial_recv_char(&c));
return hal_slip_process_char(c, buf, len, maxlen, complete);
}
/* Receive a message with SLIP framing, blocking mode.
*/
hal_error_t hal_slip_recv(uint8_t * const buf, size_t * const len, const size_t maxlen)
{
int complete;
hal_error_t ret;
while (1) {
ret = hal_slip_recv_char(buf, len, maxlen, &complete);
if ((ret != HAL_OK) || complete)
return ret;
}
}
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