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Rework the LICH parity.

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This commit is contained in:
Jonathan Naylor 2018-03-20 19:19:18 +00:00
parent f11ed22000
commit 5a22b3d0a6
3 changed files with 46 additions and 20 deletions
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30
NXDNCRC.cpp
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@ -133,6 +133,25 @@ void CNXDNCRC::encodeCRC15(unsigned char* in, unsigned int length)
}
}
bool CNXDNCRC::checkLICHParity(unsigned char in)
{
bool newParity = createLICHParity(in);
bool oldParity = (in & 0x01U) == 0x01U;
return newParity == oldParity;
}
void CNXDNCRC::encodeLICHParity(unsigned char& in)
{
bool parity = createLICHParity(in);
if (parity)
in |= 0x01U;
else
in &= 0xFEU;
}
uint8_t CNXDNCRC::createCRC6(const unsigned char* in, unsigned int length)
{
uint8_t crc = 0x3FU;
@ -183,3 +202,14 @@ uint16_t CNXDNCRC::createCRC15(const unsigned char* in, unsigned int length)
return crc & 0x7FFFU;
}
bool CNXDNCRC::createLICHParity(unsigned char in)
{
switch (in & 0xF0U) {
case 0x80U:
case 0xB0U:
return true;
default:
return false;
}
}

4
NXDNCRC.h
View file

@ -33,10 +33,14 @@ public:
static bool checkCRC15(const unsigned char* in, unsigned int length);
static void encodeCRC15(unsigned char* in, unsigned int length);
static bool checkLICHParity(unsigned char in);
static void encodeLICHParity(unsigned char& in);
private:
static uint8_t createCRC6(const unsigned char* in, unsigned int length);
static uint16_t createCRC12(const unsigned char* in, unsigned int length);
static uint16_t createCRC15(const unsigned char* in, unsigned int length);
static bool createLICHParity(unsigned char in);
};
#endif

32
NXDNLICH.cpp
View file

@ -18,6 +18,7 @@
#include "NXDNDefines.h"
#include "NXDNLICH.h"
#include "NXDNCRC.h"
#include <cstdio>
#include <cassert>
@ -50,37 +51,26 @@ bool CNXDNLICH::decode(const unsigned char* bytes)
{
assert(bytes != NULL);
bool b[8U];
unsigned int offset1 = NXDN_FSW_LENGTH_BITS;
unsigned int offset2 = 7U;
for (unsigned int i = 0U; i < (NXDN_LICH_LENGTH_BITS / 2U); i++, offset1 += 2U, offset2--) {
b[offset2] = READ_BIT1(bytes, offset1);
WRITE_BIT1(m_lich, i, b[offset2]);
unsigned int offset = NXDN_FSW_LENGTH_BITS;
for (unsigned int i = 0U; i < (NXDN_LICH_LENGTH_BITS / 2U); i++, offset += 2U) {
bool b = READ_BIT1(bytes, offset);
WRITE_BIT1(m_lich, i, b);
}
bool parity = b[7U] ^ b[6U] ^ b[5U] ^ b[4U];
if (parity != b[0U])
return false;
return true;
return CNXDNCRC::checkLICHParity(m_lich[0U]);
}
void CNXDNLICH::encode(unsigned char* bytes)
{
assert(bytes != NULL);
bool b[8U];
unsigned int offset = 7U;
for (unsigned int i = 0U; i < (NXDN_LICH_LENGTH_BITS / 2U); i++, offset--)
b[offset] = READ_BIT1(m_lich, i);
b[0U] = b[7U] ^ b[6U] ^ b[5U] ^ b[4U];
CNXDNCRC::encodeLICHParity(m_lich[0U]);
unsigned int offset1 = NXDN_FSW_LENGTH_BITS;
unsigned int offset2 = 7U;
for (unsigned int i = 0U; i < (NXDN_LICH_LENGTH_BITS / 2U); i++, offset2--) {
WRITE_BIT1(bytes, offset1, b[offset2]);
bool b = READ_BIT1(m_lich, offset2);
WRITE_BIT1(bytes, offset1, b);
offset1++;
WRITE_BIT1(bytes, offset1, true);
offset1++;
@ -109,6 +99,8 @@ unsigned char CNXDNLICH::getDirection() const
unsigned char CNXDNLICH::getRaw() const
{
CNXDNCRC::encodeLICHParity(m_lich[0U]);
return m_lich[0U];
}
@ -127,7 +119,7 @@ void CNXDNLICH::setFCT(unsigned char usc)
void CNXDNLICH::setOption(unsigned char option)
{
m_lich[0U] &= 0xF3U;
m_lich[0u] |= (option << 2) & 0x0CU;
m_lich[0U] |= (option << 2) & 0x0CU;
}
void CNXDNLICH::setDirection(unsigned char direction)