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Fixed TransportCRC compatibility with CRC-16-CCITT

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This commit is contained in:
Pavel Kirienko 2014-02-26 09:45:06 +04:00
parent a6ab9c416f
commit 887ee64d54
3 changed files with 39 additions and 26 deletions
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30
libuavcan/include/uavcan/internal/transport/crc.hpp
View File

@ -4,6 +4,7 @@
#pragma once
#include <cassert>
#include <stdint.h>
namespace uavcan
@ -11,8 +12,16 @@ namespace uavcan
/**
* CRC-16-CCITT
* Initial value: 0x0000
* Coefficient: 0x1021
* Initial value: 0xFFFF
* Poly: 0x1021
* Reverse: no
* Output xor: 0
*
* import crcmod
* crc = crcmod.predefined.Crc('crc-ccitt-false')
* crc.update('123456789')
* crc.hexdigest()
* '29B1'
*/
class TransportCRC
{
@ -23,17 +32,26 @@ public:
enum { NumBytes = 2 };
TransportCRC()
: value_(0x0000)
: value_(0xFFFF)
{ }
TransportCRC(const uint8_t* bytes, unsigned int len)
: value_(0x0000)
: value_(0xFFFF)
{
add(bytes, len);
}
uint16_t add(uint8_t byte);
uint16_t add(const uint8_t* bytes, unsigned int len);
void add(uint8_t byte)
{
value_ = ((value_ << 8) ^ Table[((value_ >> 8) ^ byte) & 0xFF]) & 0xFFFF;
}
void add(const uint8_t* bytes, unsigned int len)
{
assert(bytes);
while (len--)
add(*bytes++);
}
uint16_t get() const { return value_; }
};

14
libuavcan/src/transport/crc.cpp
View File

@ -45,18 +45,4 @@ const uint16_t TransportCRC::Table[256] =
0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0x0ed1, 0x1ef0
};
uint16_t TransportCRC::add(uint8_t byte)
{
value_ = (value_ << 8) ^ Table[((value_ >> 8) ^ byte) & 0xFF];
return value_;
}
uint16_t TransportCRC::add(const uint8_t* bytes, unsigned int len)
{
assert(bytes);
while (len--)
add(*bytes++);
return value_;
}
}

21
libuavcan/test/transport/crc.cpp
View File

@ -2,25 +2,34 @@
* Copyright (C) 2014 Pavel Kirienko <pavel.kirienko@gmail.com>
*/
#include <algorithm>
#include <gtest/gtest.h>
#include <uavcan/internal/transport/crc.hpp>
/*
import crcmod
crc = crcmod.predefined.Crc('crc-ccitt-false')
crc.update('123')
crc.hexdigest()
'5BCE'
crc.update('456789')
crc.hexdigest()
'29B1'
*/
TEST(TransportCRC, Correctness)
{
uavcan::TransportCRC crc;
ASSERT_EQ(0x0000, crc.get());
ASSERT_EQ(0xFFFF, crc.get());
crc.add('1');
crc.add('2');
crc.add('3');
ASSERT_EQ(38738, crc.get());
ASSERT_EQ(0x5BCE, crc.get());
crc.add(reinterpret_cast<const uint8_t*>("Foobar"), 6);
ASSERT_EQ(53881, crc.get());
crc.add(reinterpret_cast<const uint8_t*>("456789"), 6);
ASSERT_EQ(0x29B1, crc.get());
// Initializing constructor
ASSERT_EQ(crc.get(), uavcan::TransportCRC(reinterpret_cast<const uint8_t*>("123Foobar"), 9).get());
ASSERT_EQ(crc.get(), uavcan::TransportCRC(reinterpret_cast<const uint8_t*>("123456789"), 9).get());
}