using System;

using System.IO;

using System.Text;

/// <summary>

/// FileEncoding 的摘要说明

/// </summary>

namespace FileEncoding

{

/// <summary>

/// 获取文件的编码格式

/// </summary>

public class EncodingType

{

/// <summary>

/// 给定文件的路径，读取文件的二进制数据，判断文件的编码类型

/// </summary>

/// <param name="FILE_NAME">文件路径</param>

/// <returns>文件的编码类型</returns>

public static System.Text.Encoding GetType(string FILE_NAME)

{

FileStream fs = new FileStream(FILE_NAME, FileMode.Open, FileAccess.Read);

Encoding r = GetType(fs);

fs.Close();

return r;

}

/// <summary>

/// 通过给定的文件流，判断文件的编码类型

/// </summary>

/// <param name="fs">文件流</param>

/// <returns>文件的编码类型</returns>

public static System.Text.Encoding GetType(FileStream fs)

{

byte[] Unicode = new byte[] { 0xFF, 0xFE, 0x41 };

byte[] UnicodeBIG = new byte[] { 0xFE, 0xFF, 0x00 };

byte[] UTF8 = new byte[] { 0xEF, 0xBB, 0xBF }; //带BOM

Encoding reVal = Encoding.Default;

BinaryReader r = new BinaryReader(fs, System.Text.Encoding.Default);

int i;

int.TryParse(fs.Length.ToString(), out i);

byte[] ss = r.ReadBytes(i);

if (IsUTF8Bytes(ss) || (ss[] == 0xEF && ss[] == 0xBB && ss[] == 0xBF))

{

reVal = Encoding.UTF8;

}

else if (ss[] == 0xFE && ss[] == 0xFF && ss[] == 0x00)

{

reVal = Encoding.BigEndianUnicode;

}

else if (ss[] == 0xFF && ss[] == 0xFE && ss[] == 0x41)

{

reVal = Encoding.Unicode;

}

r.Close();

return reVal;

}

/// <summary>

/// 判断是否是不带 BOM 的 UTF8 格式

/// </summary>

/// <param name="data"></param>

/// <returns></returns>

private static bool IsUTF8Bytes(byte[] data)

{

int charByteCounter = ; //计算当前正分析的字符应还有的字节数

byte curByte; //当前分析的字节.

for (int i = ; i < data.Length; i++)

{

curByte = data[i];

if (charByteCounter == )

{

if (curByte >= 0x80)

{

//判断当前

while (((curByte <<= ) & 0x80) != )

{

charByteCounter++;

}

//标记位首位若为非0 则至少以2个1开始 如:110XXXXX...........1111110X

if (charByteCounter ==  || charByteCounter > )

{

return false;

}

}

}

else

{

//若是UTF-8 此时第一位必须为1

if ((curByte & 0xC0) != 0x80)

{

return false;

}

charByteCounter--;

}

}

if (charByteCounter > )

{

throw new Exception("非预期的byte格式");

}

return true;

}

}

}