diff options
Diffstat (limited to 'src/freedv_data_channel.c')
| -rw-r--r-- | src/freedv_data_channel.c | 314 |
1 files changed, 314 insertions, 0 deletions
diff --git a/src/freedv_data_channel.c b/src/freedv_data_channel.c new file mode 100644 index 0000000..7d361a1 --- /dev/null +++ b/src/freedv_data_channel.c @@ -0,0 +1,314 @@ +/*---------------------------------------------------------------------------*\ + + FILE........: freedv_data_channel.c + AUTHOR......: Jeroen Vreeken + DATE CREATED: 03 March 2016 + + Data channel for ethernet like packets in freedv VHF frames. + Currently designed for- + * 2 control bits per frame + * 4 byte counter bits per frame + * 64 bits of data per frame + +\*---------------------------------------------------------------------------*/ + +/* + Copyright (C) 2016 Jeroen Vreeken + + All rights reserved. + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU Lesser General Public License version 2.1, as + published by the Free Software Foundation. This program is + distributed in the hope that it will be useful, but WITHOUT ANY + WARRANTY; without even the implied warranty of MERCHANTABILITY or + FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public + License for more details. + + You should have received a copy of the GNU Lesser General Public License + along with this program; if not, see <http://www.gnu.org/licenses/>. +*/ + +#include "freedv_data_channel.h" + +#include <stdlib.h> +#include <string.h> + +static unsigned char fdc_header_bcast[6] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff }; + +/* CCIT CRC table (0x1201 polynomal) */ +static unsigned short fdc_crc_table[256] = { + 0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf, + 0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7, + 0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e, + 0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876, + 0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd, + 0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5, + 0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c, + 0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974, + 0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb, + 0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3, + 0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a, + 0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72, + 0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9, + 0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1, + 0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738, + 0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70, + 0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7, + 0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff, + 0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036, + 0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e, + 0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5, + 0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd, + 0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134, + 0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c, + 0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3, + 0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb, + 0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232, + 0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a, + 0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1, + 0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9, + 0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330, + 0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78 +}; + +static unsigned short fdc_crc(unsigned char *buffer, size_t len) +{ + unsigned short crc = 0xffff; + size_t i; + + for (i = 0; i < len; i++, buffer++) { + crc = (crc >> 8) ^ fdc_crc_table[(crc ^ *buffer) & 0xff]; + } + + return crc ^ 0xffff; +} + +/* CRC4 0x03 polynomal */ +static unsigned char fdc_crc4(unsigned char *buffer, size_t len) +{ + unsigned char crc = 0x0f; + size_t i; + + for (i = 0; i < len; i++, buffer++) { + int shift; + + for (shift = 7; shift <= 0; shift--) { + crc <<= 1; + if ((*buffer >> shift) & 0x1) + crc |= 1; + if (crc & 0x10) + crc ^= 0x03; + } + } + + return crc & 0x0f; +} + +struct freedv_data_channel *freedv_data_channel_create(void) +{ + struct freedv_data_channel *fdc; + + fdc = (struct freedv_data_channel *) calloc(1, sizeof(struct freedv_data_channel)); + if (fdc == NULL) + return NULL; + + freedv_data_set_header(fdc, fdc_header_bcast); + + memcpy(fdc->rx_header, fdc->tx_header, 8); + + return fdc; +} + +void freedv_data_channel_destroy(struct freedv_data_channel *fdc) +{ + free(fdc); +} + + +void freedv_data_set_cb_rx(struct freedv_data_channel *fdc, freedv_data_callback_rx cb, void *state) +{ + fdc->cb_rx = cb; + fdc->cb_rx_state = state; +} + +void freedv_data_set_cb_tx(struct freedv_data_channel *fdc, freedv_data_callback_tx cb, void *state) +{ + fdc->cb_tx = cb; + fdc->cb_tx_state = state; +} + +void freedv_data_channel_rx_frame(struct freedv_data_channel *fdc, unsigned char *data, size_t size, int from_bit, int bcast_bit, int crc_bit, int end_bits) +{ + int copy_bits; + if (end_bits) { + copy_bits = end_bits; + } else { + copy_bits = size; + } + + /* New packet? */ + if (fdc->packet_rx_cnt == 0) { + /* Does the packet have a compressed from field? */ + if (from_bit) { + /* Compressed from: take the previously received header */ + memcpy(fdc->packet_rx + fdc->packet_rx_cnt, fdc->rx_header, 6); + fdc->packet_rx_cnt += 6; + } + if (bcast_bit) { + if (!from_bit) { + /* Copy from header and modify size and end_bits accordingly */ + memcpy(fdc->packet_rx + fdc->packet_rx_cnt, data, 6); + fdc->packet_rx_cnt += 6; + copy_bits -= 6; + if (copy_bits < 0) + copy_bits = 0; + data += 6; + } + /* Compressed to: fill in broadcast address */ + memcpy(fdc->packet_rx + fdc->packet_rx_cnt, fdc_header_bcast, sizeof(fdc_header_bcast)); + fdc->packet_rx_cnt += 6; + } + if (crc_bit) { + unsigned char calc_crc = fdc_crc4(data, size); + if (calc_crc == end_bits) { + /* It is a single header field, remember it for later */ + memcpy(fdc->rx_header, data, 6); + memcpy(fdc->packet_rx + 6, data, 6); + memcpy(fdc->packet_rx, fdc_header_bcast, 6); + if (fdc->cb_rx) { + fdc->cb_rx(fdc->cb_rx_state, fdc->packet_rx, 12); + } + } + fdc->packet_rx_cnt = 0; + return; + } + } + + if (fdc->packet_rx_cnt + copy_bits >= FREEDV_DATA_CHANNEL_PACKET_MAX) { + /* Something went wrong... this can not be a real packet */ + fdc->packet_rx_cnt = 0; + return; + } + + memcpy(fdc->packet_rx + fdc->packet_rx_cnt, data, copy_bits); + fdc->packet_rx_cnt += copy_bits; + + if (end_bits != 0 && fdc->packet_rx_cnt >= 2) { + unsigned short calc_crc = fdc_crc(fdc->packet_rx, fdc->packet_rx_cnt - 2); + unsigned short rx_crc; + rx_crc = fdc->packet_rx[fdc->packet_rx_cnt - 1] << 8; + rx_crc |= fdc->packet_rx[fdc->packet_rx_cnt - 2]; + + if (rx_crc == calc_crc) { + if (fdc->packet_rx_cnt == size) { + /* It is a single header field, remember it for later */ + memcpy(fdc->rx_header, fdc->packet_rx, 6); + } + + /* callback */ + if (fdc->cb_rx) { + unsigned char tmp[6]; + memcpy(tmp, fdc->packet_rx, 6); + memcpy(fdc->packet_rx, fdc->packet_rx + 6, 6); + memcpy(fdc->packet_rx + 6, tmp, 6); + + size_t size = fdc->packet_rx_cnt - 2; + if (size < 12) { + size = 12; + memcpy(fdc->packet_rx, fdc_header_bcast, 6); + } + fdc->cb_rx(fdc->cb_rx_state, fdc->packet_rx, size); + } + } + fdc->packet_rx_cnt = 0; + } +} + +void freedv_data_channel_tx_frame(struct freedv_data_channel *fdc, unsigned char *data, size_t size, int *from_bit, int *bcast_bit, int *crc_bit, int *end_bits) +{ + *from_bit = 0; + *bcast_bit = 0; + *crc_bit = 0; + + if (!fdc->packet_tx_size) { + fdc->packet_tx_cnt = 0; + + if (fdc->cb_tx) { + fdc->packet_tx_size = FREEDV_DATA_CHANNEL_PACKET_MAX; + fdc->cb_tx(fdc->cb_tx_state, fdc->packet_tx, &fdc->packet_tx_size); + } + if (!fdc->packet_tx_size) { + /* Nothing to send, insert a header frame */ + memcpy(fdc->packet_tx, fdc->tx_header, size); + if (size < 8) { + *end_bits = fdc_crc4(fdc->tx_header, size); + *crc_bit = 1; + memcpy(data, fdc->tx_header, size); + + return; + } else { + fdc->packet_tx_size = size; + } + } else { + /* new packet */ + unsigned short crc; + unsigned char tmp[6]; + + *from_bit = !memcmp(fdc->packet_tx + 6, fdc->tx_header, 6); + *bcast_bit = !memcmp(fdc->packet_tx, fdc_header_bcast, 6); + + memcpy(tmp, fdc->packet_tx, 6); + memcpy(fdc->packet_tx, fdc->packet_tx + 6, 6); + memcpy(fdc->packet_tx + 6, tmp, 6); + + crc = fdc_crc(fdc->packet_tx, fdc->packet_tx_size); + + fdc->packet_tx[fdc->packet_tx_size] = crc & 0xff; + fdc->packet_tx_size++; + fdc->packet_tx[fdc->packet_tx_size] = (crc >> 8) & 0xff; + fdc->packet_tx_size++; + + if (*from_bit) { + fdc->packet_tx_cnt = 6; + } else { + if (*bcast_bit) { + memcpy(fdc->packet_tx + 6, fdc->packet_tx, 6); + } + } + if (*bcast_bit) { + fdc->packet_tx_cnt += 6; + } + } + } + if (fdc->packet_tx_size) { + int copy = fdc->packet_tx_size - fdc->packet_tx_cnt; + + if (copy > size) { + copy = size; + *end_bits = 0; + } else { + *end_bits = copy; + fdc->packet_tx_size = 0; + } + memcpy(data, fdc->packet_tx + fdc->packet_tx_cnt, copy); + fdc->packet_tx_cnt += copy; + } +} + +void freedv_data_set_header(struct freedv_data_channel *fdc, unsigned char *header) +{ + unsigned short crc = fdc_crc(header, 6); + + memcpy(fdc->tx_header, header, 6); + fdc->tx_header[6] = crc & 0xff; + fdc->tx_header[7] = (crc >> 8) & 0xff; +} + +int freedv_data_get_n_tx_frames(struct freedv_data_channel *fdc, size_t size) +{ + if (fdc->packet_tx_size == 0) + return 0; + /* packet will be send in 'size' byte frames */ + return (fdc->packet_tx_size - fdc->packet_tx_cnt + size-1) / size; +} |