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slip.c
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slip.c
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/*
The MIT License (MIT)
Copyright (c) 2017 Marcin Borowicz <[email protected]>
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/
#include "slip.h"
#include <stddef.h>
#include <assert.h>
static const uint16_t crc_table[256] = {
0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5,
0x60c6, 0x70e7, 0x8108, 0x9129, 0xa14a, 0xb16b,
0xc18c, 0xd1ad, 0xe1ce, 0xf1ef, 0x1231, 0x0210,
0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6,
0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c,
0xf3ff, 0xe3de, 0x2462, 0x3443, 0x0420, 0x1401,
0x64e6, 0x74c7, 0x44a4, 0x5485, 0xa56a, 0xb54b,
0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d,
0x3653, 0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6,
0x5695, 0x46b4, 0xb75b, 0xa77a, 0x9719, 0x8738,
0xf7df, 0xe7fe, 0xd79d, 0xc7bc, 0x48c4, 0x58e5,
0x6886, 0x78a7, 0x0840, 0x1861, 0x2802, 0x3823,
0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969,
0xa90a, 0xb92b, 0x5af5, 0x4ad4, 0x7ab7, 0x6a96,
0x1a71, 0x0a50, 0x3a33, 0x2a12, 0xdbfd, 0xcbdc,
0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a,
0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03,
0x0c60, 0x1c41, 0xedae, 0xfd8f, 0xcdec, 0xddcd,
0xad2a, 0xbd0b, 0x8d68, 0x9d49, 0x7e97, 0x6eb6,
0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70,
0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a,
0x9f59, 0x8f78, 0x9188, 0x81a9, 0xb1ca, 0xa1eb,
0xd10c, 0xc12d, 0xf14e, 0xe16f, 0x1080, 0x00a1,
0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067,
0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c,
0xe37f, 0xf35e, 0x02b1, 0x1290, 0x22f3, 0x32d2,
0x4235, 0x5214, 0x6277, 0x7256, 0xb5ea, 0xa5cb,
0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d,
0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466, 0x6447,
0x5424, 0x4405, 0xa7db, 0xb7fa, 0x8799, 0x97b8,
0xe75f, 0xf77e, 0xc71d, 0xd73c, 0x26d3, 0x36f2,
0x0691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634,
0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9,
0xb98a, 0xa9ab, 0x5844, 0x4865, 0x7806, 0x6827,
0x18c0, 0x08e1, 0x3882, 0x28a3, 0xcb7d, 0xdb5c,
0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a,
0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1, 0x1ad0,
0x2ab3, 0x3a92, 0xfd2e, 0xed0f, 0xdd6c, 0xcd4d,
0xbdaa, 0xad8b, 0x9de8, 0x8dc9, 0x7c26, 0x6c07,
0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0x0cc1,
0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba,
0x8fd9, 0x9ff8, 0x6e17, 0x7e36, 0x4e55, 0x5e74,
0x2e93, 0x3eb2, 0x0ed1, 0x1ef0
};
static uint16_t calc_crc_ccitt(uint8_t byte, uint16_t crc_old)
{
uint8_t index;
uint16_t crc;
index = (uint8_t)(byte ^ (crc_old >> 8));
crc = (uint16_t)(crc_table[index] ^ (crc_old << 8));
return crc;
}
static void reset_rx(slip_handler_s *slip)
{
assert(slip != NULL);
slip->state = SLIP_STATE_NORMAL;
slip->size = 0;
slip->crc = slip->descriptor->crc_seed;
}
slip_error_t slip_init(slip_handler_s *slip, const slip_descriptor_s *descriptor)
{
assert(slip != NULL);
assert(descriptor != NULL);
assert(descriptor->buf != NULL);
assert(descriptor->recv_message != NULL);
assert(descriptor->write_byte != NULL);
slip->descriptor = descriptor;
reset_rx(slip);
return SLIP_NO_ERROR;
}
static slip_error_t put_byte_to_buffer(slip_handler_s *slip, uint8_t byte)
{
slip_error_t error = SLIP_NO_ERROR;
assert(slip != NULL);
if (slip->size >= slip->descriptor->buf_size) {
error = SLIP_ERROR_BUFFER_OVERFLOW;
reset_rx(slip);
} else {
slip->descriptor->buf[slip->size++] = byte;
slip->crc = calc_crc_ccitt(byte, slip->crc);
slip->state = SLIP_STATE_NORMAL;
}
return error;
}
slip_error_t slip_read_byte(slip_handler_s *slip, uint8_t byte)
{
slip_error_t error = SLIP_NO_ERROR;
assert(slip != NULL);
switch (slip->state) {
case SLIP_STATE_NORMAL:
switch (byte) {
case SLIP_SPECIAL_BYTE_END:
if (slip->size >= 2) {
if (slip->crc == 0) {
slip->descriptor->recv_message(
slip->descriptor->buf,
slip->size - 2
);
} else {
error = SLIP_ERROR_CRC_MISMATCH;
}
}
reset_rx(slip);
break;
case SLIP_SPECIAL_BYTE_ESC:
slip->state = SLIP_STATE_ESCAPED;
break;
default:
error = put_byte_to_buffer(slip, byte);
break;
}
break;
case SLIP_STATE_ESCAPED:
switch (byte) {
case SLIP_ESCAPED_BYTE_END:
byte = SLIP_SPECIAL_BYTE_END;
break;
case SLIP_ESCAPED_BYTE_ESC:
byte = SLIP_SPECIAL_BYTE_ESC;
break;
default:
error = SLIP_ERROR_UNKNOWN_ESCAPED_BYTE;
reset_rx(slip);
break;
}
if (error != SLIP_NO_ERROR)
break;
error = put_byte_to_buffer(slip, byte);
break;
}
return error;
}
static uint8_t write_encoded_byte(slip_handler_s *slip, uint8_t byte)
{
uint8_t escape = 0;
assert(slip != NULL);
switch (byte) {
case SLIP_SPECIAL_BYTE_END:
byte = SLIP_ESCAPED_BYTE_END;
escape = 1;
break;
case SLIP_SPECIAL_BYTE_ESC:
byte = SLIP_ESCAPED_BYTE_ESC;
escape = 1;
break;
}
if (escape != 0) {
if (slip->descriptor->write_byte(SLIP_SPECIAL_BYTE_ESC) == 0)
return 0;
}
if (slip->descriptor->write_byte(byte) == 0)
return 0;
return 1;
}
slip_error_t slip_send_message(slip_handler_s *slip, uint8_t *data, uint32_t size)
{
uint32_t i;
uint8_t byte;
uint8_t crc_buf[2];
uint16_t crc;
assert(data != NULL);
assert(slip != NULL);
if (slip->descriptor->write_byte(SLIP_SPECIAL_BYTE_END) == 0)
return SLIP_ERROR_BUFFER_OVERFLOW;
crc = slip->descriptor->crc_seed;
for (i = 0; i < size; i++) {
byte = data[i];
crc = calc_crc_ccitt(byte, crc);
if (write_encoded_byte(slip, byte) == 0)
return SLIP_ERROR_BUFFER_OVERFLOW;
}
crc_buf[0] = (uint8_t) (crc >> 8);
crc_buf[1] = (uint8_t) (crc & 0xFF);
for (i = 0; i < 2; i++) {
byte = crc_buf[i];
if (write_encoded_byte(slip, byte) == 0)
return SLIP_ERROR_BUFFER_OVERFLOW;
}
if (slip->descriptor->write_byte(SLIP_SPECIAL_BYTE_END) == 0)
return SLIP_ERROR_BUFFER_OVERFLOW;
return SLIP_NO_ERROR;
}