七牛C#语言hash或者etag值计算代码

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication2
{
class QETag
{
private int CHUNK_SIZE = 1 << 22;

public byte[] sha1(byte[] data)  {
return System.Security.Cryptography.SHA1.Create().ComputeHash(data);
}

public String urlSafeBase64Encode(byte[] data) {
String encodedString = Convert.ToBase64String(data);
encodedString = encodedString.Replace('+', '-').Replace('/', '_');
return encodedString;
}
static void Main(string[] args)
{
Console.WriteLine("Usage: qetag <path>-----" + @"c:\test\MyTest.txt");
string path = Console.ReadLine();
QETag etag = new QETag();
try {
Console.WriteLine(etag.calcETag(path));
} catch (Exception ex) {
Console.WriteLine("Unsupported algorithm:" + ex.Message);
}

Console.WriteLine("algorithm-hash-etag");
Console.Read();
}
public String calcETag(String path)
{
if (File.Exists(path))
{
File.Delete(path);
}
String etag = "";
FileStream fs ;
using ( fs= File.Create(path))
{
Byte[] info = new UTF8Encoding(true).GetBytes("This is some text in the file.");
fs.Write(info, 0, info.Length);
}
fs = File.OpenRead(path);
long fileLength = fs.Length;
if (fileLength <= CHUNK_SIZE)
{
byte[] fileData = new byte[(int)fileLength];
fs.Read(fileData, 0, (int)fileLength);
byte[] sha1Data = sha1(fileData);
int sha1DataLen = sha1Data.Length;
byte[] hashData = new byte[sha1DataLen + 1];

System.Array.Copy(sha1Data, 0, hashData, 1, sha1DataLen);
hashData[0] = 0x16;
etag = urlSafeBase64Encode(hashData);
}
else
{
int chunkCount = (int)(fileLength / CHUNK_SIZE);
if (fileLength % CHUNK_SIZE != 0)
{
chunkCount += 1;
}
byte[] allSha1Data = new byte[0];
for (int i = 0; i < chunkCount; i++)
{
byte[] chunkData = new byte[CHUNK_SIZE];
int bytesReadLen = fs.Read(chunkData, 0, CHUNK_SIZE);
byte[] bytesRead = new byte[bytesReadLen];
System.Array.Copy(chunkData, 0, bytesRead, 0, bytesReadLen);
byte[] chunkDataSha1 = sha1(bytesRead);
byte[] newAllSha1Data = new byte[chunkDataSha1.Length
+ allSha1Data.Length ];
System.Array.Copy(allSha1Data, 0, newAllSha1Data, 0,
allSha1Data.Length );
System.Array.Copy(chunkDataSha1, 0, newAllSha1Data,
allSha1Data.Length , chunkDataSha1.Length );
allSha1Data = newAllSha1Data;
}
byte[] allSha1DataSha1 = sha1(allSha1Data);
byte[] hashData = new byte[allSha1DataSha1.Length  + 1];
System.Array.Copy(allSha1DataSha1, 0, hashData, 1,
allSha1DataSha1.Length );
hashData[0] = (byte)0x96;
etag = urlSafeBase64Encode(hashData);
}
fs.Close();
return etag;

}
}
}