cdigest.java

说明： 1、里面有什么： 1.1、org.bouncycastle.*下的所有软件是bouncycastle组织开发的软件包 1.2、org.infosecurity.*下的软件包括

package org.infosecurity.cryptography;
import org.infosecurity.cryptography.*;
/**
 * <p>Title: 摘要算法的抽象类 </p>
 * <p>Description: 摘要算法的抽象类 </p>
 * <p>Copyright: Copyright (c) 2003</p>
 * <p>Company:bouncycastle org </p>
 */
public abstract class CDigest
    implements IDigest
{
    private byte[]  xBuf;
    private int     xBufOff;

    private long    byteCount;
    // 1.构造
	protected CDigest()
	{
		xBuf = new byte[4];
		xBufOff = 0;
	}
	protected CDigest(CDigest t)
	{
        xBuf = new byte[t.xBuf.length];
		System.arraycopy(t.xBuf, 0, xBuf, 0, t.xBuf.length);

		xBufOff = t.xBufOff;
		byteCount = t.byteCount;
	}

    // 2.输入一个字节的数据

    public void update(
        byte in)
    {
        xBuf[xBufOff++] = in;
        // 填充满一个4个字节了
        if (xBufOff == xBuf.length)
        {
            processWord(xBuf, 0);
            xBufOff = 0;
        }

        byteCount++;
    }

    public void update(
        byte[]  in,
        int     inOff,
        int     len)
    {
        //
        // fill the current word
        //
        while ((xBufOff != 0) && (len > 0))
        {
            update(in[inOff]);

            inOff++;
            len--;
        }

        //
        // process whole words.
        //
        while (len > xBuf.length)
        {
            processWord(in, inOff);

            inOff += xBuf.length;
            len -= xBuf.length;
            byteCount += xBuf.length;
        }

        //
        // load in the remainder.
        //
        while (len > 0)
        {
            update(in[inOff]);

            inOff++;
            len--;
        }
    }
    // 3.完成
    public void finish()
    {
        // 每一个字节是8位

        long    bitLength = (byteCount << 3);

        //
        // 附加填充比特一个1，多个0，直到len mod 512 = 448
        //1000,0000B=128
        update((byte)128);

        while (xBufOff != 0)
        {
            update((byte)0);
        }
        // 最后填充8字节(64bit)的长度信息
        processLength(bitLength);
        // 处理最后一块
        processBlock();
    }

    public void reset()
    {
        byteCount = 0;

        xBufOff = 0;
		for ( int i = 0; i < xBuf.length; i++ ) {
			xBuf[i] = 0;
		}
    }

    protected abstract void processWord(byte[] in, int inOff);

    protected abstract void processLength(long bitLength);

    protected abstract void processBlock();
}