mgf1bytesgenerator.java

java 文件下载器。可自定义

// Decompiled by Jad v1.5.8e2. Copyright 2001 Pavel Kouznetsov.
// Jad home page: http://kpdus.tripod.com/jad.html
// Decompiler options: packimports(3) fieldsfirst ansi space 
// Source File Name:   MGF1BytesGenerator.java

package org.bouncycastle.crypto.generators;

import org.bouncycastle.crypto.*;
import org.bouncycastle.crypto.params.MGFParameters;

public class MGF1BytesGenerator
	implements DerivationFunction
{

	private Digest digest;
	private byte seed[];
	private int hLen;

	public MGF1BytesGenerator(Digest digest)
	{
		this.digest = digest;
		hLen = digest.getDigestSize();
	}

	public void init(DerivationParameters param)
	{
		if (!(param instanceof MGFParameters))
		{
			throw new IllegalArgumentException("MGF parameters required for MGF1Generator");
		} else
		{
			MGFParameters p = (MGFParameters)param;
			seed = p.getSeed();
			return;
		}
	}

	public Digest getDigest()
	{
		return digest;
	}

	private void ItoOSP(int i, byte sp[])
	{
		sp[0] = (byte)(i >>> 24);
		sp[1] = (byte)(i >>> 16);
		sp[2] = (byte)(i >>> 8);
		sp[3] = (byte)(i >>> 0);
	}

	public int generateBytes(byte out[], int outOff, int len)
		throws DataLengthException, IllegalArgumentException
	{
		byte hashBuf[] = new byte[hLen];
		byte C[] = new byte[4];
		int counter = 0;
		digest.reset();
		do
		{
			ItoOSP(counter, C);
			digest.update(seed, 0, seed.length);
			digest.update(C, 0, C.length);
			digest.doFinal(hashBuf, 0);
			System.arraycopy(hashBuf, 0, out, outOff + counter * hLen, hLen);
		} while (++counter < len / hLen);
		if (counter * hLen < len)
		{
			ItoOSP(counter, C);
			digest.update(seed, 0, seed.length);
			digest.update(C, 0, C.length);
			digest.doFinal(hashBuf, 0);
			System.arraycopy(hashBuf, 0, out, outOff + counter * hLen, len - counter * hLen);
		}
		return len;
	}
}