/// <summary> /// 提供用于计算指定文件哈希值的方法 /// <example>例如计算文件的MD5值: /// <code> /// String hashMd5=HashHelper.ComputeMD5("MyFile.txt"); /// </code> /// </example> /// <example>例如计算文件的CRC32值: /// <code> /// String hashCrc32 = HashHelper.ComputeCRC32("MyFile.txt"); /// </code> /// </example> /// <example>例如计算文件的SHA1值: /// <code> /// String hashSha1 =HashHelper.ComputeSHA1("MyFile.txt"); /// </code> /// </example> /// </summary> public sealed class HashHelper { /// <summary> /// 计算指定文件的MD5值 /// </summary> /// <param name="fileName">指定文件的完全限定名称</param> /// <returns>返回值的字符串形式</returns> public static String ComputeMD5(String fileName) { String hashMD5 = String.Empty; //检查文件是否存在，如果文件存在则进行计算，否则返回空值 if (System.IO.File.Exists(fileName)) { using (System.IO.FileStream fs = new System.IO.FileStream(fileName, System.IO.FileMode.Open, System.IO.FileAccess.Read)) { //计算文件的MD5值 System.Security.Cryptography.MD5 calculator=System.Security.Cryptography.MD5.Create(); Byte[] buffer = calculator.ComputeHash(fs); calculator.Clear(); //将字节数组转换成十六进制的字符串形式 StringBuilder stringBuilder = new StringBuilder(); for (int i = 0; i < buffer.Length; i++) { stringBuilder.Append(buffer[i].ToString("x2")); } hashMD5= stringBuilder.ToString(); }//关闭文件流 }//结束计算 return hashMD5; }//ComputeMD5 /// <summary> /// 计算指定文件的CRC32值 /// </summary> /// <param name="fileName">指定文件的完全限定名称</param> /// <returns>返回值的字符串形式</returns> public static String ComputeCRC32(String fileName) { String hashCRC32 = String.Empty; //检查文件是否存在，如果文件存在则进行计算，否则返回空值 if (System.IO.File.Exists(fileName)) { using (System.IO.FileStream fs = new System.IO.FileStream(fileName, System.IO.FileMode.Open, System.IO.FileAccess.Read)) { //计算文件的CSC32值 Crc32 calculator = new Crc32(); Byte[] buffer = calculator.ComputeHash(fs); calculator.Clear(); //将字节数组转换成十六进制的字符串形式 StringBuilder stringBuilder = new StringBuilder(); for (int i = 0; i < buffer.Length; i++) { stringBuilder.Append(buffer[i].ToString("x2")); } hashCRC32 = stringBuilder.ToString(); }//关闭文件流 } return hashCRC32; }//ComputeCRC32 /// <summary> /// 计算指定文件的SHA1值 /// </summary> /// <param name="fileName">指定文件的完全限定名称</param> /// <returns>返回值的字符串形式</returns> public static String ComputeSHA1(String fileName) { String hashSHA1 = String.Empty; //检查文件是否存在，如果文件存在则进行计算，否则返回空值 if (System.IO.File.Exists(fileName)) { using (System.IO.FileStream fs = new System.IO.FileStream(fileName, System.IO.FileMode.Open, System.IO.FileAccess.Read)) { //计算文件的SHA1值 System.Security.Cryptography.SHA1 calculator = System.Security.Cryptography.SHA1.Create(); Byte[] buffer = calculator.ComputeHash(fs); calculator.Clear(); //将字节数组转换成十六进制的字符串形式 StringBuilder stringBuilder = new StringBuilder(); for (int i = 0; i < buffer.Length; i++) { stringBuilder.Append(buffer[i].ToString("x2")); } hashSHA1 = stringBuilder.ToString(); }//关闭文件流 } return hashSHA1; }//ComputeSHA1 }//end class: HashHelper /// <summary> /// 提供 CRC32 算法的实现 /// </summary> public class Crc32 : System.Security.Cryptography.HashAlgorithm { public const UInt32 DefaultPolynomial = 0xedb88320; public const UInt32 DefaultSeed = 0xffffffff; private UInt32 hash; private UInt32 seed; private UInt32[] table; private static UInt32[] defaultTable; public Crc32() { table = InitializeTable(DefaultPolynomial); seed = DefaultSeed; Initialize(); } public Crc32(UInt32 polynomial, UInt32 seed) { table = InitializeTable(polynomial); this.seed = seed; Initialize(); } public override void Initialize() { hash = seed; } protected override void HashCore(byte[] buffer, int start, int length) { hash = CalculateHash(table, hash, buffer, start, length); } protected override byte[] HashFinal() { byte[] hashBuffer = UInt32ToBigEndianBytes(~hash); this.HashValue = hashBuffer; return hashBuffer; } public static UInt32 Compute(byte[] buffer) { return ~CalculateHash(InitializeTable(DefaultPolynomial), DefaultSeed, buffer, 0, buffer.Length); } public static UInt32 Compute(UInt32 seed, byte[] buffer) { return ~CalculateHash(InitializeTable(DefaultPolynomial), seed, buffer, 0, buffer.Length); } public static UInt32 Compute(UInt32 polynomial, UInt32 seed, byte[] buffer) { return ~CalculateHash(InitializeTable(polynomial), seed, buffer, 0, buffer.Length); } private static UInt32[] InitializeTable(UInt32 polynomial) { if (polynomial == DefaultPolynomial && defaultTable != null) { return defaultTable; } UInt32[] createTable = new UInt32[256]; for (int i = 0; i < 256; i++) { UInt32 entry = (UInt32)i; for (int j = 0; j < 8; j++) { if ((entry & 1) == 1) entry = (entry >> 1) ^ polynomial; else entry = entry >> 1; } createTable[i] = entry; } if (polynomial == DefaultPolynomial) { defaultTable = createTable; } return createTable; } private static UInt32 CalculateHash(UInt32[] table, UInt32 seed, byte[] buffer, int start, int size) { UInt32 crc = seed; for (int i = start; i < size; i++) { unchecked { crc = (crc >> 8) ^ table[buffer[i] ^ crc & 0xff]; } } return crc; } private byte[] UInt32ToBigEndianBytes(UInt32 x) { return new byte[] { (byte)((x >> 24) & 0xff), (byte)((x >> 16) & 0xff), (byte)((x >> 8) & 0xff), (byte)(x & 0xff) }; } }//end class: Crc32