using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Web;

namespace WeChat.CRC
{

public class CRC
{
#region CRC16
public static byte[] CRC16(byte[] data)
{
int len = data.Length;
if (len > 0)
{
ushort crc = 0xFFFF;

for (int i = 0; i < len; i++)
{
crc = (ushort)(crc ^ (data[i]));
for (int j = 0; j < 8; j++)
{
crc = (crc & 1) != 0 ? (ushort)((crc >> 1) ^ 0xA001) : (ushort)(crc >> 1);
}
}
byte hi = (byte)((crc & 0xFF00) >> 8); //高位置
byte lo = (byte)(crc & 0x00FF); //低位置

return new byte[] { hi, lo };
}
return new byte[] { 0, 0 };
}
#endregion

#region ToCRC16
public static string ToCRC16(string content)
{
return ToCRC16(content, Encoding.UTF8);
}

public static string ToCRC16(string content, bool isReverse)
{
return ToCRC16(content, Encoding.UTF8, isReverse);
}

public static string ToCRC16(string content, Encoding encoding)
{
return ByteToString(CRC16(encoding.GetBytes(content)), true);
}

public static string ToCRC16(string content, Encoding encoding, bool isReverse)
{
return ByteToString(CRC16(encoding.GetBytes(content)), isReverse);
}

public static string ToCRC16(byte[] data)
{
return ByteToString(CRC16(data), true);
}

public static string ToCRC16(byte[] data, bool isReverse)
{
return ByteToString(CRC16(data), isReverse);
}
#endregion

#region ToModbusCRC16
public static string ToModbusCRC16(string s)
{
return ToModbusCRC16(s, true);
}

public static string ToModbusCRC16(string s, bool isReverse)
{
return ByteToString(CRC16(StringToHexByte(s)), isReverse);
}

public static string ToModbusCRC16(byte[] data)
{
return ToModbusCRC16(data, true);
}

public static string ToModbusCRC16(byte[] data, bool isReverse)
{
return ByteToString(CRC16(data), isReverse);
}
#endregion

#region ByteToString
public static string ByteToString(byte[] arr, bool isReverse)
{
try
{
byte hi = arr[0], lo = arr[1];
return Convert.ToString(isReverse ? hi + lo * 0x100 : hi * 0x100 + lo, 16).ToUpper().PadLeft(4, '0');
}
catch (Exception ex) { throw (ex); }
}

public static string ByteToString(byte[] arr)
{
try
{
return ByteToString(arr, true);
}
catch (Exception ex) { throw (ex); }
}
#endregion

#region StringToHexString
public static string StringToHexString(string str)
{
StringBuilder s = new StringBuilder();
foreach (short c in str.ToCharArray())
{
s.Append(c.ToString("X4"));
}
return s.ToString();
}
#endregion

#region StringToHexByte
private static string ConvertChinese(string str)
{
StringBuilder s = new StringBuilder();
foreach (short c in str.ToCharArray())
{
if (c <= 0 || c >= 127)
{
s.Append(c.ToString("X4"));
}
else
{
s.Append((char)c);
}
}
return s.ToString();
}

private static string FilterChinese(string str)
{
StringBuilder s = new StringBuilder();
foreach (short c in str.ToCharArray())
{
if (c > 0 && c < 127)
{
s.Append((char)c);
}
}
return s.ToString();
}

/// <summary>
/// 字符串转16进制字符数组
/// </summary>
/// <param name="hex"></param>
/// <returns></returns>
public static byte[] StringToHexByte(string str)
{
return StringToHexByte(str, false);
}

/// <summary>
/// 字符串转16进制字符数组
/// </summary>
/// <param name="str"></param>
/// <param name="isFilterChinese">是否过滤掉中文字符</param>
/// <returns></returns>
public static byte[] StringToHexByte(string str, bool isFilterChinese)
{
string hex = isFilterChinese ? FilterChinese(str) : ConvertChinese(str);

//清除所有空格
hex = hex.Replace(" ", "");
//若字符个数为奇数，补一个0
hex += hex.Length % 2 != 0 ? "0" : "";

byte[] result = new byte[hex.Length / 2];
for (int i = 0, c = result.Length; i < c; i++)
{
result[i] = Convert.ToByte(hex.Substring(i * 2, 2), 16);
}
return result;
}
#endregion
}
}