MMDVMHost-Private/M17Utils.cpp

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2020-12-15 16:21:07 +00:00
/*
* Copyright (C) 2020,2021 by Jonathan Naylor G4KLX
2020-12-15 16:21:07 +00:00
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* 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 General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include "M17Utils.h"
#include "M17Defines.h"
#include <cassert>
const std::string M17_CHARS = " ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-/.";
const unsigned char BIT_MASK_TABLE[] = { 0x80U, 0x40U, 0x20U, 0x10U, 0x08U, 0x04U, 0x02U, 0x01U };
#define WRITE_BIT1(p,i,b) p[(i)>>3] = (b) ? (p[(i)>>3] | BIT_MASK_TABLE[(i)&7]) : (p[(i)>>3] & ~BIT_MASK_TABLE[(i)&7])
#define READ_BIT1(p,i) (p[(i)>>3] & BIT_MASK_TABLE[(i)&7])
void CM17Utils::encodeCallsign(const std::string& callsign, unsigned char* encoded)
{
assert(encoded != NULL);
unsigned int len = callsign.size();
if (len > 9U)
len = 9U;
uint64_t enc = 0ULL;
for (int i = len - 1; i >= 0; i--) {
size_t pos = M17_CHARS.find(callsign[i]);
if (pos == std::string::npos)
pos = 0ULL;
enc *= 40ULL;
enc += pos;
}
encoded[0U] = (enc >> 40) & 0xFFU;
encoded[1U] = (enc >> 32) & 0xFFU;
encoded[2U] = (enc >> 24) & 0xFFU;
encoded[3U] = (enc >> 16) & 0xFFU;
encoded[4U] = (enc >> 8) & 0xFFU;
encoded[5U] = (enc >> 0) & 0xFFU;
}
void CM17Utils::decodeCallsign(const unsigned char* encoded, std::string& callsign)
{
assert(encoded != NULL);
callsign.clear();
uint64_t enc =
(uint64_t(encoded[0U]) << 40) +
(uint64_t(encoded[1U]) << 32) +
(uint64_t(encoded[2U]) << 24) +
(uint64_t(encoded[3U]) << 16) +
(uint64_t(encoded[4U]) << 8) +
(uint64_t(encoded[5U]) << 0);
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if (enc >= 262144000000000ULL) // 40^9
return;
while (enc > 0ULL) {
callsign += " ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-/."[enc % 40ULL];
enc /= 40ULL;
}
}
void CM17Utils::splitFragmentLICH(const unsigned char* data, unsigned int& frag1, unsigned int& frag2, unsigned int& frag3, unsigned int& frag4)
{
assert(data != NULL);
frag1 = frag2 = frag3 = frag4 = 0x00U;
unsigned int offset = 0U;
unsigned int MASK = 0x800U;
for (unsigned int i = 0U; i < (M17_LICH_FRAGMENT_LENGTH_BITS / 4U); i++, offset++, MASK >>= 1) {
bool b = READ_BIT1(data, offset) != 0x00U;
if (b)
frag1 |= MASK;
}
MASK = 0x800U;
for (unsigned int i = 0U; i < (M17_LICH_FRAGMENT_LENGTH_BITS / 4U); i++, offset++, MASK >>= 1) {
bool b = READ_BIT1(data, offset) != 0x00U;
if (b)
frag2 |= MASK;
}
MASK = 0x800U;
for (unsigned int i = 0U; i < (M17_LICH_FRAGMENT_LENGTH_BITS / 4U); i++, offset++, MASK >>= 1) {
bool b = READ_BIT1(data, offset) != 0x00U;
if (b)
frag3 |= MASK;
}
MASK = 0x800U;
for (unsigned int i = 0U; i < (M17_LICH_FRAGMENT_LENGTH_BITS / 4U); i++, offset++, MASK >>= 1) {
bool b = READ_BIT1(data, offset) != 0x00U;
if (b)
frag4 |= MASK;
}
}
void CM17Utils::splitFragmentLICHFEC(const unsigned char* data, unsigned int& frag1, unsigned int& frag2, unsigned int& frag3, unsigned int& frag4)
{
assert(data != NULL);
frag1 = frag2 = frag3 = frag4 = 0x00U;
unsigned int offset = 0U;
unsigned int MASK = 0x800000U;
for (unsigned int i = 0U; i < (M17_LICH_FRAGMENT_FEC_LENGTH_BITS / 4U); i++, offset++, MASK >>= 1) {
bool b = READ_BIT1(data, offset) != 0x00U;
if (b)
frag1 |= MASK;
}
MASK = 0x800000U;
for (unsigned int i = 0U; i < (M17_LICH_FRAGMENT_FEC_LENGTH_BITS / 4U); i++, offset++, MASK >>= 1) {
bool b = READ_BIT1(data, offset) != 0x00U;
if (b)
frag2 |= MASK;
}
MASK = 0x800000U;
for (unsigned int i = 0U; i < (M17_LICH_FRAGMENT_FEC_LENGTH_BITS / 4U); i++, offset++, MASK >>= 1) {
bool b = READ_BIT1(data, offset) != 0x00U;
if (b)
frag3 |= MASK;
}
MASK = 0x800000U;
for (unsigned int i = 0U; i < (M17_LICH_FRAGMENT_FEC_LENGTH_BITS / 4U); i++, offset++, MASK >>= 1) {
bool b = READ_BIT1(data, offset) != 0x00U;
if (b)
frag4 |= MASK;
}
}
void CM17Utils::combineFragmentLICH(unsigned int frag1, unsigned int frag2, unsigned int frag3, unsigned int frag4, unsigned char* data)
{
assert(data != NULL);
unsigned int offset = 0U;
unsigned int MASK = 0x800U;
for (unsigned int i = 0U; i < (M17_LICH_FRAGMENT_LENGTH_BITS / 4U); i++, offset++, MASK >>= 1) {
bool b = (frag1 & MASK) == MASK;
WRITE_BIT1(data, offset, b);
}
MASK = 0x800U;
for (unsigned int i = 0U; i < (M17_LICH_FRAGMENT_LENGTH_BITS / 4U); i++, offset++, MASK >>= 1) {
bool b = (frag2 & MASK) == MASK;
WRITE_BIT1(data, offset, b);
}
MASK = 0x800U;
for (unsigned int i = 0U; i < (M17_LICH_FRAGMENT_LENGTH_BITS / 4U); i++, offset++, MASK >>= 1) {
bool b = (frag3 & MASK) == MASK;
WRITE_BIT1(data, offset, b);
}
MASK = 0x800U;
for (unsigned int i = 0U; i < (M17_LICH_FRAGMENT_LENGTH_BITS / 4U); i++, offset++, MASK >>= 1) {
bool b = (frag4 & MASK) == MASK;
WRITE_BIT1(data, offset, b);
}
}
void CM17Utils::combineFragmentLICHFEC(unsigned int frag1, unsigned int frag2, unsigned int frag3, unsigned int frag4, unsigned char* data)
{
assert(data != NULL);
unsigned int offset = 0U;
unsigned int MASK = 0x800000U;
for (unsigned int i = 0U; i < (M17_LICH_FRAGMENT_FEC_LENGTH_BITS / 4U); i++, offset++, MASK >>= 1) {
bool b = (frag1 & MASK) == MASK;
WRITE_BIT1(data, offset, b);
}
MASK = 0x800000U;
for (unsigned int i = 0U; i < (M17_LICH_FRAGMENT_FEC_LENGTH_BITS / 4U); i++, offset++, MASK >>= 1) {
bool b = (frag2 & MASK) == MASK;
WRITE_BIT1(data, offset, b);
}
MASK = 0x800000U;
for (unsigned int i = 0U; i < (M17_LICH_FRAGMENT_FEC_LENGTH_BITS / 4U); i++, offset++, MASK >>= 1) {
bool b = (frag3 & MASK) == MASK;
WRITE_BIT1(data, offset, b);
}
MASK = 0x800000U;
for (unsigned int i = 0U; i < (M17_LICH_FRAGMENT_FEC_LENGTH_BITS / 4U); i++, offset++, MASK >>= 1) {
bool b = (frag4 & MASK) == MASK;
WRITE_BIT1(data, offset, b);
}
}