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/*
* Copyright 2018 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "crc.hpp"
namespace blobs
{
void Crc16::clear()
{
value = crc16Initial;
}
// Origin: security/crypta/ipmi/portable/ipmi_utils.c
void Crc16::compute(const uint8_t* bytes, uint32_t length)
{
if (!bytes)
{
return;
}
const int kExtraRounds = 2;
const uint16_t kLeftBit = 0x8000;
uint16_t crc = value;
size_t i, j;
for (i = 0; i < length + kExtraRounds; ++i)
{
for (j = 0; j < 8; ++j)
{
bool xor_flag = crc & kLeftBit;
crc <<= 1;
// If this isn't an extra round and the current byte's j'th bit
// from the left is set, increment the CRC.
if (i < length && bytes[i] & (1 << (7 - j)))
{
crc++;
}
if (xor_flag)
{
crc ^= crc16Ccitt;
}
}
}
value = crc;
}
uint16_t Crc16::get() const
{
return value;
}
} // namespace blobs
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