137 lines
3.6 KiB
C++
137 lines
3.6 KiB
C++
/*
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* Copyright (C) 2014 Jared Boone, ShareBrained Technology, Inc.
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* Copyright (C) 2017 Furrtek
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*
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* This file is part of PortaPack.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; see the file COPYING. If not, write to
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* the Free Software Foundation, Inc., 51 Franklin Street,
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* Boston, MA 02110-1301, USA.
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*/
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#ifndef __ADSB_FRAME_H__
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#define __ADSB_FRAME_H__
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#include <cstring>
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#include <string>
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#include <cstdint>
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namespace adsb {
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alignas(4) const uint8_t adsb_preamble[16] = {1, 0, 1, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0};
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alignas(4) const char icao_id_lut[65] = "#ABCDEFGHIJKLMNOPQRSTUVWXYZ##### ###############0123456789######";
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class ADSBFrame {
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public:
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uint8_t get_DF() {
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return (raw_data[0] >> 3);
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}
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uint8_t get_msg_type() {
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return (raw_data[4] >> 3);
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}
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uint8_t get_msg_sub() {
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return (raw_data[4] & 7);
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}
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uint8_t get_sil_value() {
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return ((raw_data[10] >> 6) & 0b11); // 83-84 bits
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}
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uint32_t get_ICAO_address() {
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return (raw_data[1] << 16) + (raw_data[2] << 8) + raw_data[3];
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}
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void set_rx_timestamp(uint32_t timestamp) {
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rx_timestamp = timestamp;
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}
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uint32_t get_rx_timestamp() {
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return rx_timestamp;
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}
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void clear() {
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index = 0;
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memset(raw_data, 0, 14);
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}
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void push_byte(uint8_t byte) {
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if (index >= 14)
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return;
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raw_data[index++] = byte;
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}
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uint8_t* get_raw_data() const {
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return (uint8_t*)raw_data;
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}
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void make_CRC() {
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uint32_t computed_CRC = compute_CRC();
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// Insert CRC in frame
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raw_data[11] = (computed_CRC >> 16) & 0xFF;
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raw_data[12] = (computed_CRC >> 8) & 0xFF;
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raw_data[13] = computed_CRC & 0xFF;
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}
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bool check_CRC() {
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uint32_t computed_CRC = compute_CRC();
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if ((raw_data[11] != ((computed_CRC >> 16) & 0xFF)) ||
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(raw_data[12] != ((computed_CRC >> 8) & 0xFF)) ||
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(raw_data[13] != (computed_CRC & 0xFF))) return false;
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return true;
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}
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bool empty() {
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return (index == 0);
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}
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private:
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static const uint8_t adsb_preamble[16];
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static const char icao_id_lut[65];
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alignas(4) uint8_t index{0};
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alignas(4) uint8_t raw_data[14]{}; // 112 bits at most
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uint32_t rx_timestamp{};
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uint32_t compute_CRC() {
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uint8_t adsb_crc[14] = {0}; // Temp buffer
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uint8_t b, c, s, bitn;
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const uint32_t crc_poly = 0x1205FFF;
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// Copy frame data
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memcpy(adsb_crc, raw_data, 11);
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// Compute CRC
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for (c = 0; c < 11; c++) {
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for (b = 0; b < 8; b++) {
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if ((adsb_crc[c] << b) & 0x80) {
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for (s = 0; s < 25; s++) {
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bitn = (c * 8) + b + s;
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if ((crc_poly >> s) & 1) adsb_crc[bitn >> 3] ^= (0x80 >> (bitn & 7));
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}
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}
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}
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}
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return (adsb_crc[11] << 16) + (adsb_crc[12] << 8) + adsb_crc[13];
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}
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};
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} /* namespace adsb */
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#endif /*__ADSB_FRAME_H__*/
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