87 lines
2.1 KiB
C
87 lines
2.1 KiB
C
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/*
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This source code is part of the AIS BlackToolkit.
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Unpacker.c allows you to build a NMEA sentece out of its payload. Normally used in combination with AIVDM_Encoder.
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Copyright 2013-2014 -- Embyte & Pastus
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; either version 2
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of the License, or (at your option) any later version.
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Usage example:
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$ ./AIVDM_Encoder.py --type=1 --vsize=30x10 | xargs -IA ./unpacker A 1 A
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*/
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#include <sstream>
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#include <ctype.h>
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#include <stdio.h>
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#include <iostream>
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#include <iomanip>
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#include <string.h>
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unsigned long unpack(char *buffer, int start, int length)
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{
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unsigned long ret = 0;
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for(int i = start; i < (start+length); i++) {
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ret <<= 1;
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ret |= (buffer[i] & 0x01);
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}
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return ret;
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}
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char nmea_checksum(std::string buffer)
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{
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unsigned int i = 0;
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char sum = 0x00;
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if(buffer[0] == '!') i++;
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for(; i < buffer.length(); i++) sum ^= buffer[i];
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return sum;
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}
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int main(int argc, char *argv[]) {
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if (argc<4) {
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std::cout << "\nUsage: ./unpacker binary_string enable_nmea channel\n";
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std::cout << "\nenable_nmea = 1 for full NMEA sentence, otherwise only payload is printed\n";
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std::cout << "channel = A/B\n\n";
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return 0;
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}
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int i;
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char asciidata[255];
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int len = strlen(argv[1]);
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int enable_nmea = (int) *argv[2] - 48;
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char channel = *argv[3];
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std::ostringstream d_payload;
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d_payload.str("");
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for(i = 0; i < len/6; i++) {
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asciidata[i] = unpack(argv[1], i*6, 6);
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if(asciidata[i] > 39) asciidata[i] += 8;
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asciidata[i] += 48;
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}
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if (enable_nmea)
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d_payload << "!AIVDM,1,1,," << channel << ",";
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for(int i = 0; i < len/6; i++)
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d_payload << asciidata[i];
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if (enable_nmea) {
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d_payload << ",0"; //number of bits to fill out 6-bit boundary
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char checksum = nmea_checksum(std::string(d_payload.str()));
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d_payload << "*" << std::setw(2) << std::setfill('0') << std::hex << std::uppercase << int(checksum);
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}
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std::cout << std::string(d_payload.str()) << std::endl;
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return 1;
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}
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