MMDVMHost-Private/EmbeddedLC.cpp

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2016-01-14 18:45:04 +00:00
/*
* Copyright (C) 2015 by Jonathan Naylor G4KLX
*
* 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 "EmbeddedLC.h"
#include "Hamming.h"
#include "Utils.h"
#include "CRC.h"
#include "Log.h"
#include <cstdio>
#include <cassert>
#include <cstring>
CEmbeddedLC::CEmbeddedLC() :
m_rawLC(NULL),
m_state(LCS_NONE)
{
m_rawLC = new bool[128U];
}
CEmbeddedLC::~CEmbeddedLC()
{
delete[] m_rawLC;
}
// Add LC data (which may consist of 4 blocks) to the data store
CLC* CEmbeddedLC::addData(const unsigned char* data, unsigned char lcss)
{
assert(data != NULL);
bool rawData[40U];
CUtils::byteToBitsBE(data[14U], rawData + 0U);
CUtils::byteToBitsBE(data[15U], rawData + 8U);
CUtils::byteToBitsBE(data[16U], rawData + 16U);
CUtils::byteToBitsBE(data[17U], rawData + 24U);
CUtils::byteToBitsBE(data[18U], rawData + 32U);
// Is this the first block of a 4 block embedded LC ?
if (lcss == 1U) {
for (unsigned int a = 0U; a < 32U; a++)
m_rawLC[a] = rawData[a + 4U];
// Show we are ready for the next LC block
m_state = LCS_FIRST;
return NULL;
}
// Is this the 2nd block of a 4 block embedded LC ?
if (lcss == 3U && m_state == LCS_FIRST) {
for (unsigned int a = 0U; a < 32U; a++)
m_rawLC[a + 32U] = rawData[a + 4U];
// Show we are ready for the next LC block
m_state = LCS_SECOND;
return NULL;
}
// Is this the 3rd block of a 4 block embedded LC ?
if (lcss == 3U && m_state == LCS_SECOND) {
for (unsigned int a = 0U; a < 32U; a++)
m_rawLC[a + 64U] = rawData[a + 4U];
// Show we are ready for the final LC block
m_state = LCS_THIRD;
return NULL;
}
// Is this the final block of a 4 block embedded LC ?
if (lcss == 2U && m_state == LCS_THIRD) {
for (unsigned int a = 0U; a < 32U; a++)
m_rawLC[a + 96U] = rawData[a + 4U];
// Process the complete data block
return processMultiBlockEmbeddedLC();
}
// Is this a single block embedded LC
if (lcss == 0U) {
processSingleBlockEmbeddedLC(rawData + 4U);
return NULL;
}
return NULL;
}
void CEmbeddedLC::setData(const CLC& lc)
{
bool lcData[72U];
lc.getData(lcData);
unsigned int crc;
CCRC::encodeFiveBit(lcData, crc);
bool data[128U];
::memset(data, 0x00U, 128U * sizeof(bool));
data[106U] = (crc & 0x01U) == 0x01U;
data[90U] = (crc & 0x02U) == 0x02U;
data[74U] = (crc & 0x04U) == 0x04U;
data[58U] = (crc & 0x08U) == 0x08U;
data[42U] = (crc & 0x10U) == 0x10U;
unsigned int b = 0U;
for (unsigned int a = 0U; a < 11U; a++, b++)
data[a] = lcData[b];
for (unsigned int a = 16U; a < 27U; a++, b++)
data[a] = lcData[b];
for (unsigned int a = 32U; a < 42U; a++, b++)
data[a] = lcData[b];
for (unsigned int a = 48U; a < 58U; a++, b++)
data[a] = lcData[b];
for (unsigned int a = 64U; a < 74U; a++, b++)
data[a] = lcData[b];
for (unsigned int a = 80U; a < 90U; a++, b++)
data[a] = lcData[b];
for (unsigned int a = 96U; a < 106U; a++, b++)
data[a] = lcData[b];
// Hamming (16,11,4) check each row except the last one
for (unsigned int a = 0U; a < 112U; a += 16U)
CHamming::encode16114(data + a);
// Add the parity bits for each column
for (unsigned int a = 0U; a < 16U; a++)
data[a + 112U] = data[a + 0U] ^ data[a + 16U] ^ data[a + 32U] ^ data[a + 48U] ^ data[a + 64U] ^ data[a + 80U] ^ data[a + 96U];
// The data is packed downwards in columns
b = 0U;
for (unsigned int a = 0U; a < 128U; a++) {
m_rawLC[a] = data[b];
b += 16U;
if (b > 127U)
b -= 127U;
}
}
unsigned int CEmbeddedLC::getData(unsigned char* data, unsigned int n) const
{
assert(data != NULL);
if (n < 4U) {
bool bits[40U];
::memset(bits, 0x00U, 40U * sizeof(bool));
::memcpy(bits + 4U, m_rawLC + n * 32U, 32U * sizeof(bool));
unsigned char bytes[5U];
CUtils::bitsToByteBE(bits + 0U, bytes[0U]);
CUtils::bitsToByteBE(bits + 8U, bytes[1U]);
CUtils::bitsToByteBE(bits + 16U, bytes[2U]);
CUtils::bitsToByteBE(bits + 24U, bytes[3U]);
CUtils::bitsToByteBE(bits + 32U, bytes[4U]);
data[14U] = (data[14U] & 0xF0U) | (bytes[0U] & 0x0FU);
data[15U] = bytes[1U];
data[16U] = bytes[2U];
data[17U] = bytes[3U];
data[18U] = (data[18U] & 0x0FU) | (bytes[4U] & 0xF0U);
} else {
data[14U] &= 0xF0U;
data[15U] = 0x00U;
data[16U] = 0x00U;
data[17U] = 0x00U;
data[18U] &= 0x0FU;
}
switch (n) {
case 0U:
return 1U;
case 1U:
case 2U:
return 3U;
case 3U:
return 2U;
default:
return 0U;
}
}
// Unpack and error check an embedded LC
CLC* CEmbeddedLC::processMultiBlockEmbeddedLC()
{
// The data is unpacked downwards in columns
bool data[128U];
::memset(data, 0x00U, 128U * sizeof(bool));
unsigned int b = 0U;
for (unsigned int a = 0U; a < 128U; a++) {
data[b] = m_rawLC[a];
b += 16U;
if (b > 127U)
b -= 127U;
}
// Hamming (16,11,4) check each row except the last one
for (unsigned int a = 0U; a < 112U; a += 16U) {
if (!CHamming::decode16114(data + a)) {
::LogDebug("Hamming decode of a row of the Embedded LC failed");
return NULL;
}
}
// Check the parity bits
for (unsigned int a = 0U; a < 16U; a++) {
bool parity = data[a + 0U] ^ data[a + 16U] ^ data[a + 32U] ^ data[a + 48U] ^ data[a + 64U] ^ data[a + 80U] ^ data[a + 96U] ^ data[a + 112U];
if (parity) {
::LogDebug("Parity check of a column of the Embedded LC failed");
return NULL;
}
}
// We have passed the Hamming check so extract the actual payload
bool lcData[72U];
b = 0U;
for (unsigned int a = 0U; a < 11U; a++, b++)
lcData[b] = data[a];
for (unsigned int a = 16U; a < 27U; a++, b++)
lcData[b] = data[a];
for (unsigned int a = 32U; a < 42U; a++, b++)
lcData[b] = data[a];
for (unsigned int a = 48U; a < 58U; a++, b++)
lcData[b] = data[a];
for (unsigned int a = 64U; a < 74U; a++, b++)
lcData[b] = data[a];
for (unsigned int a = 80U; a < 90U; a++, b++)
lcData[b] = data[a];
for (unsigned int a = 96U; a < 106U; a++, b++)
lcData[b] = data[a];
// Extract the 5 bit CRC
unsigned int crc = 0U;
if (data[42]) crc += 16U;
if (data[58]) crc += 8U;
if (data[74]) crc += 4U;
if (data[90]) crc += 2U;
if (data[106]) crc += 1U;
// Now CRC check this
if (!CCRC::checkFiveBit(lcData, crc)) {
::LogDebug("Checksum of the Embedded LC failed");
return NULL;
}
return new CLC(lcData);
}
// Deal with a single block embedded LC
void CEmbeddedLC::processSingleBlockEmbeddedLC(const bool* data)
{
// Nothing interesting, or just NULL (I think)
}