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using System;
using System.Collections.Generic;
using System.Text;
namespace Apewer.Internals
{
class CRC16
{
public static CRC16 Instance = new CRC16();
const ushort origin = 0xFFFF;
const ushort polynomial = 0xA001;
ushort[] table = new ushort[256];
public CRC16()
{
ushort value, temp;
for (ushort i = 0; i < table.Length; ++i)
{
value = 0;
temp = i;
for (byte j = 0; j < 8; ++j)
{
if (((value ^ temp) & 0x0001) != 0)
{
value = (ushort)((value >> 1) ^ polynomial);
}
else
{
value >>= 1;
}
temp >>= 1;
}
table[i] = value;
}
}
public ushort Compute(byte[] bytes)
{
ushort crc = origin;
for (int i = 0; i < bytes.Length; ++i)
{
byte index = (byte)(crc ^ bytes[i]);
crc = (ushort)((crc >> 8) ^ table[index]);
}
return crc;
}
}
}