84 lines
2.6 KiB
C++
84 lines
2.6 KiB
C++
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/*
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* Copyright (C) 2020 by Jonathan Naylor G4KLX
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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 of the License, or
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* (at your option) 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; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include "M17Utils.h"
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#include <cassert>
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void CM17Utils::encodeCallsign(const std::string& callsign, unsigned char* encoded)
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{
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assert(encoded != NULL);
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std::string call = callsign;
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call.resize(8U, ' ');
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uint64_t enc = 0ULL;
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for (int i = 7U; i >= 0; i--) {
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char c = call.at(i);
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enc *= 40ULL;
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// If speed is more important than code space, you can replace this with a lookup into a 256 byte array.
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if (c >= 'A' && c <= 'Z') // 1-26
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enc += c - 'A' + 1ULL;
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else if (c >= '0' && c <= '9') // 27-36
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enc += c - '0' + 27ULL;
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else if (c == '-') // 37
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enc += 37ULL;
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// These are just place holders. If other characters make more sense, change these.
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// Be sure to change them in the decode array below too.
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else if (c == '/') // 38
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enc += 38ULL;
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else if (c == '.') // 39
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enc += 39ULL;
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else
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// Invalid character or space, represented by 0, decoded as a space.
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enc += 0ULL;
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}
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encoded[0U] = enc >> 40;
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encoded[1U] = enc >> 32;
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encoded[2U] = enc >> 24;
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encoded[3U] = enc >> 16;
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encoded[4U] = enc >> 8;
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encoded[5U] = enc >> 0;
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}
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void CM17Utils::decodeCallsign(const unsigned char* encoded, std::string& callsign)
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{
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assert(encoded != NULL);
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callsign.empty();
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uint64_t enc = (uint64_t(encoded[5U]) << 40) +
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(uint64_t(encoded[4U]) << 32) +
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(uint64_t(encoded[3U]) << 24) +
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(uint64_t(encoded[2U]) << 16) +
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(uint64_t(encoded[1U]) << 8) +
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(uint64_t(encoded[0U]) << 0);
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if (enc >= 262144000000000ULL) // 40^9
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return;
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while (enc > 0ULL) {
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callsign += " ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-/."[enc % 40ULL];
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enc /= 40ULL;
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}
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}
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