Java文件Hash类,实现对计算进度的监视以及多算法的同时计算

利用Java自带的MessageDigest来数据的Hash值非常方便,如:

MessageDigest messageDigest = MessageDigest.getInstance("MD5"); 
FileInputStream in = new FileInputStream(file); 
FileChannel ch = in.getChannel(); 
MappedByteBuffer byteBuffer = ch.map(FileChannel.MapMode.READ_ONLY, 0, file.length()); 
messageDigest.update(byteBuffer); 
return messageDigest.digest();  

 

但如果计算较大的数据则无法监视计算进度.于是我对数据的读取和处理进行了简单的封装,以达到通过注册监听器进行进度监视的目的.

关键部分代码如下:

    private void updateHash() throws IOException {
    boolean readToEnd = readLength == 0;
    byte[] bytesBuf = new byte[bufferSize];
    int readLen;
    while ((readToEnd || readCount < readLength)
        && (readLen = inputStream.read(bytesBuf)) > 0) {
        readCount += readLen;
        HashBuffer buf = new HashBuffer(bytesBuf, readLen, inputStream);
        for (HashProgressInterceptor itcp : ltcps) {
        itcp.bytesRead(buf, this);
        }
        if (!buf.isSkip()) {
        for (MessageDigest md : messageDigests) {
            md.update(buf.getData(), buf.getOffset(), buf.getLength());
        }
        }
    }
    byteArrayHash = new byte[messageDigests.length][];
    for (int i = 0; i < messageDigests.length; i++) {
        byteArrayHash[i] = messageDigests[i].digest();
    }
    }

 

原理很简单,就是每读取一些数据就调用监听器方法并传入信息参数.

使用方法:

1.通过抽象类HashCalc的工厂方法获取实例.

2.注册监听器(如果需要监视进度).

3.调用getHexStringHash()或getByteArrayHash()取得结果,这两个方法的区别仅是结果的形式不同.第一次调用这两个方法其中之一时会进行计算并缓存结果,之后再调用将直接返回缓存中的值.

 

import idv.takamachi660.util.hash.HashBuffer;
import idv.takamachi660.util.hash.HashCalc;
import idv.takamachi660.util.hash.HashProgressInterceptor;
import idv.takamachi660.util.hash.IHashCalc;

import java.io.File;
import java.io.IOException;
import java.security.MessageDigest;

public class FileHashDemo {

    public static void main(String[] args) throws IOException {
    long startTime = System.currentTimeMillis();
    IHashCalc hash = HashCalc.getFileInstance(
        "your file name here", "MD5", "SHA-1");
    hash.setBufferSize(5242880);
    // set buffer size to 5MB default value is 1MB
    hash.addHashProgressInterceptor(new HashProgressInterceptor() {
        @Override
        public void bytesRead(HashBuffer buffer, IHashCalc calc) {
        long finished = calc.getReadCount();
        long total = ((File) calc.getSource()).length();
        System.out.println(String.format("read %d bytes,%.2f%%", buffer
            .getLength(), finished * 100.0 / total));
        }
    });
    MessageDigest[] mds = hash.getMessageDigests();
    String[] results = hash.getHexStringHash();
    for (int i = 0; i < mds.length; i++) {
        System.out.println(mds[i].getAlgorithm() + "=" + results[i]);
    }
    System.out.println("spend " + (System.currentTimeMillis() - startTime)
        + "Millis");
    }
}

 

 

 

其他内容见doc.

/Files/takamachi660/Java_HashTools.zip