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181 | /* GATE PROJECT LICENSE:
+----------------------------------------------------------------------------+
| Copyright(c) 2018-2025, Stefan Meislinger <sm@opengate.at> |
| All rights reserved. |
| |
| Redistribution and use in source and binary forms, with or without |
| modification, are permitted provided that the following conditions are met:|
| |
| 1. Redistributions of source code must retain the above copyright notice, |
| this list of conditions and the following disclaimer. |
| 2. Redistributions in binary form must reproduce the above copyright |
| notice, this list of conditions and the following disclaimer in the |
| documentation and/or other materials provided with the distribution. |
| |
| THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"|
| AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| ARE DISCLAIMED.IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE |
| LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
| CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
| SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
| INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
| CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
| ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF |
| THE POSSIBILITY OF SUCH DAMAGE. |
+----------------------------------------------------------------------------+
*/
#include "gate/encode/crchash.h"
#include "gate/memalloc.h"
/* https://de.wikipedia.org/wiki/Zyklische_Redundanzpr%C3%BCfung */
void gate_crc32_init(gate_crc32_t* crc32hash)
{
crc32hash->value = 0;
}
#define CRC32POLY 0x04C11DB7
void gate_crc32_update(gate_crc32_t* crc32hash, void const* databuffer, unsigned databufferlength)
{
unsigned char const* ptr_data = (unsigned char const*)databuffer;
unsigned char chr;<--- The scope of the variable 'chr' can be reduced. [+]The scope of the variable 'chr' can be reduced. Warning: Be careful when fixing this message, especially when there are inner loops. Here is an example where cppcheck will write that the scope for 'i' can be reduced:
void f(int x)
{
int i = 0;
if (x) {
// it's safe to move 'int i = 0;' here
for (int n = 0; n < 10; ++n) {
// it is possible but not safe to move 'int i = 0;' here
do_something(&i);
}
}
}
When you see this message it is always safe to reduce the variable scope 1 level.
unsigned n;
while (databufferlength-- > 0)
{
chr = *ptr_data;
for (n = 0; n != 8; ++n)
{
if (((crc32hash->value >> 31u) & 1u) != ((chr >> n) & 1u))
{
crc32hash->value = (crc32hash->value << 1) ^ CRC32POLY;
}
else
{
crc32hash->value = (crc32hash->value << 1);
}
}
++ptr_data;
}
}
void gate_crc32_finish(gate_crc32_t* crc32hash, gate_crc32_result_t* resulthashbuffer)
{
resulthashbuffer->hash[0] = (unsigned char)((crc32hash->value >> 24) & 0x0ff);
resulthashbuffer->hash[1] = (unsigned char)((crc32hash->value >> 16) & 0x0ff);
resulthashbuffer->hash[2] = (unsigned char)((crc32hash->value >> 8) & 0x0ff);
resulthashbuffer->hash[3] = (unsigned char)((crc32hash->value) & 0x0ff);
}
#define GATE_CRC16_MODE_NORMAL 1
#define GATE_CRC16_MODE_NORMAL_SWAP 2
#define GATE_CRC16_MODE_REVERSE 3
#define GATE_CRC16_MODE_REVERSE_SWAP 4
gate_crc16_t gate_crc16hash_arc = { 0x0000, 0xa001, GATE_CRC16_MODE_REVERSE };
gate_crc16_t gate_crc16hash_modbus = { 0xffff, 0xa001, GATE_CRC16_MODE_REVERSE };
gate_crc16_t gate_crc16hash_kermit = { 0x0000, 0x8408, GATE_CRC16_MODE_REVERSE_SWAP };
gate_crc16_t gate_crc16hash_xmodem = { 0x0000, 0x1021, GATE_CRC16_MODE_NORMAL };
gate_crc16_t gate_crc16hash_ccitt = { 0xffff, 0x1021, GATE_CRC16_MODE_NORMAL };
void gate_crc16_init(gate_crc16_t* crc16hash, unsigned crc16type)
{
switch (crc16type)
{
case GATE_CRC16_TYPE_ARC: *crc16hash = gate_crc16hash_arc; break;
case GATE_CRC16_TYPE_KERMIT: *crc16hash = gate_crc16hash_kermit; break;
case GATE_CRC16_TYPE_CCITT_FALSE: *crc16hash = gate_crc16hash_ccitt; break;
case GATE_CRC16_TYPE_XMODEM: *crc16hash = gate_crc16hash_xmodem; break;
default:
case GATE_CRC16_TYPE_MODBUS: *crc16hash = gate_crc16hash_modbus; break;
}
}
/* http://www.nongnu.org/avr-libc/user-manual/group__util__crc.html#gaca726c22a1900f9bad52594c8846115f
uses a regular polynomial representation
*/
static void gate_crc16_add_data_normal(unsigned short* crcvalue, unsigned short mask, char const* buffer, unsigned int bufferlen)
{
unsigned ndx;
while (bufferlen--)
{
unsigned char data = (unsigned char)(*(buffer++));
*crcvalue ^= ((unsigned short)data) << 8;
for (ndx = 0; ndx != 8; ++ndx)
{
if (*crcvalue & 0x8000)
{
*crcvalue = (*crcvalue << 1) ^ mask;
}
else
{
*crcvalue <<= 1;
}
}
}
}
/* http://de.wikipedia.org/wiki/Zyklische_Redundanzpr%C3%BCfung
uses a reversed polynomial representation
*/
static void gate_crc16_add_data_reverse(unsigned short* crcvalue, unsigned short mask, char const* buffer, unsigned int bufferlen)
{
unsigned int len;
unsigned int ndx;
for (len = bufferlen; len > 0; --len, ++buffer)
{
*crcvalue = *crcvalue ^ (unsigned short)(unsigned char)(*buffer);
for (ndx = 0; ndx != 8; ++ndx)
{
if ((*crcvalue & 1) != 0)
{
*crcvalue = (*crcvalue >> 1) ^ mask;
}
else
{
*crcvalue >>= 1;
}
}
}
}
void gate_crc16_update(gate_crc16_t* crc16hash, void const* databuffer, unsigned databufferlength)
{
switch (crc16hash->mode)
{
case GATE_CRC16_MODE_REVERSE:
case GATE_CRC16_MODE_REVERSE_SWAP:
gate_crc16_add_data_reverse(&crc16hash->value, crc16hash->mask, databuffer, databufferlength);
break;
case GATE_CRC16_MODE_NORMAL:
case GATE_CRC16_MODE_NORMAL_SWAP:
gate_crc16_add_data_normal(&crc16hash->value, crc16hash->mask, databuffer, databufferlength);
break;
}
}
void gate_crc16_finish(gate_crc16_t* crc16hash, gate_crc16_result_t* resulthashbuffer)
{
switch (crc16hash->mode)
{
case GATE_CRC16_MODE_REVERSE:
case GATE_CRC16_MODE_NORMAL:
resulthashbuffer->hash[0] = (unsigned char)((crc16hash->value & 0xff00) >> 8);
resulthashbuffer->hash[1] = (unsigned char)(crc16hash->value & 0x00ff);
break;
case GATE_CRC16_MODE_NORMAL_SWAP:
case GATE_CRC16_MODE_REVERSE_SWAP:
resulthashbuffer->hash[0] = (unsigned char)(crc16hash->value & 0x00ff);
resulthashbuffer->hash[1] = (unsigned char)((crc16hash->value & 0xff00) >> 8);
break;
}
}
|