base64.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:   Base64.java

package org.bouncycastle.util.encoders;

import java.io.IOException;
import java.io.OutputStream;

public class Base64
{

	private static final byte encodingTable[] = {
		65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 
		75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 
		85, 86, 87, 88, 89, 90, 97, 98, 99, 100, 
		101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 
		111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 
		121, 122, 48, 49, 50, 51, 52, 53, 54, 55, 
		56, 57, 43, 47
	};
	private static final byte decodingTable[];

	public Base64()
	{
	}

	public static byte[] encode(byte data[])
	{
		int modulus = data.length % 3;
		byte bytes[];
		if (modulus == 0)
			bytes = new byte[(4 * data.length) / 3];
		else
			bytes = new byte[4 * (data.length / 3 + 1)];
		int dataLength = data.length - modulus;
		int i = 0;
		for (int j = 0; i < dataLength; j += 4)
		{
			int a1 = data[i] & 0xff;
			int a2 = data[i + 1] & 0xff;
			int a3 = data[i + 2] & 0xff;
			bytes[j] = encodingTable[a1 >>> 2 & 0x3f];
			bytes[j + 1] = encodingTable[(a1 << 4 | a2 >>> 4) & 0x3f];
			bytes[j + 2] = encodingTable[(a2 << 2 | a3 >>> 6) & 0x3f];
			bytes[j + 3] = encodingTable[a3 & 0x3f];
			i += 3;
		}

		switch (modulus)
		{
		case 1: // '\001'
		{
			int d1 = data[data.length - 1] & 0xff;
			int b1 = d1 >>> 2 & 0x3f;
			int b2 = d1 << 4 & 0x3f;
			bytes[bytes.length - 4] = encodingTable[b1];
			bytes[bytes.length - 3] = encodingTable[b2];
			bytes[bytes.length - 2] = 61;
			bytes[bytes.length - 1] = 61;
			break;
		}

		case 2: // '\002'
		{
			int d1 = data[data.length - 2] & 0xff;
			int d2 = data[data.length - 1] & 0xff;
			int b1 = d1 >>> 2 & 0x3f;
			int b2 = (d1 << 4 | d2 >>> 4) & 0x3f;
			int b3 = d2 << 2 & 0x3f;
			bytes[bytes.length - 4] = encodingTable[b1];
			bytes[bytes.length - 3] = encodingTable[b2];
			bytes[bytes.length - 2] = encodingTable[b3];
			bytes[bytes.length - 1] = 61;
			break;
		}
		}
		return bytes;
	}

	public static byte[] decode(byte data[])
	{
		if (data.length == 0)
			return data;
		byte bytes[];
		if (data[data.length - 2] == 61)
			bytes = new byte[(data.length / 4 - 1) * 3 + 1];
		else
		if (data[data.length - 1] == 61)
			bytes = new byte[(data.length / 4 - 1) * 3 + 2];
		else
			bytes = new byte[(data.length / 4) * 3];
		int i = 0;
		for (int j = 0; i < data.length - 4; j += 3)
		{
			byte b1 = decodingTable[data[i]];
			byte b2 = decodingTable[data[i + 1]];
			byte b3 = decodingTable[data[i + 2]];
			byte b4 = decodingTable[data[i + 3]];
			bytes[j] = (byte)(b1 << 2 | b2 >> 4);
			bytes[j + 1] = (byte)(b2 << 4 | b3 >> 2);
			bytes[j + 2] = (byte)(b3 << 6 | b4);
			i += 4;
		}

		if (data[data.length - 2] == 61)
		{
			byte b1 = decodingTable[data[data.length - 4]];
			byte b2 = decodingTable[data[data.length - 3]];
			bytes[bytes.length - 1] = (byte)(b1 << 2 | b2 >> 4);
		} else
		if (data[data.length - 1] == 61)
		{
			byte b1 = decodingTable[data[data.length - 4]];
			byte b2 = decodingTable[data[data.length - 3]];
			byte b3 = decodingTable[data[data.length - 2]];
			bytes[bytes.length - 2] = (byte)(b1 << 2 | b2 >> 4);
			bytes[bytes.length - 1] = (byte)(b2 << 4 | b3 >> 2);
		} else
		{
			byte b1 = decodingTable[data[data.length - 4]];
			byte b2 = decodingTable[data[data.length - 3]];
			byte b3 = decodingTable[data[data.length - 2]];
			byte b4 = decodingTable[data[data.length - 1]];
			bytes[bytes.length - 3] = (byte)(b1 << 2 | b2 >> 4);
			bytes[bytes.length - 2] = (byte)(b2 << 4 | b3 >> 2);
			bytes[bytes.length - 1] = (byte)(b3 << 6 | b4);
		}
		return bytes;
	}

	public static byte[] decode(String data)
	{
		if (data.length() == 0)
			return new byte[0];
		byte bytes[];
		if (data.charAt(data.length() - 2) == '=')
			bytes = new byte[(data.length() / 4 - 1) * 3 + 1];
		else
		if (data.charAt(data.length() - 1) == '=')
			bytes = new byte[(data.length() / 4 - 1) * 3 + 2];
		else
			bytes = new byte[(data.length() / 4) * 3];
		int i = 0;
		for (int j = 0; i < data.length() - 4; j += 3)
		{
			byte b1 = decodingTable[data.charAt(i)];
			byte b2 = decodingTable[data.charAt(i + 1)];
			byte b3 = decodingTable[data.charAt(i + 2)];
			byte b4 = decodingTable[data.charAt(i + 3)];
			bytes[j] = (byte)(b1 << 2 | b2 >> 4);
			bytes[j + 1] = (byte)(b2 << 4 | b3 >> 2);
			bytes[j + 2] = (byte)(b3 << 6 | b4);
			i += 4;
		}

		if (data.charAt(data.length() - 2) == '=')
		{
			byte b1 = decodingTable[data.charAt(data.length() - 4)];
			byte b2 = decodingTable[data.charAt(data.length() - 3)];
			bytes[bytes.length - 1] = (byte)(b1 << 2 | b2 >> 4);
		} else
		if (data.charAt(data.length() - 1) == '=')
		{
			byte b1 = decodingTable[data.charAt(data.length() - 4)];
			byte b2 = decodingTable[data.charAt(data.length() - 3)];
			byte b3 = decodingTable[data.charAt(data.length() - 2)];
			bytes[bytes.length - 2] = (byte)(b1 << 2 | b2 >> 4);
			bytes[bytes.length - 1] = (byte)(b2 << 4 | b3 >> 2);
		} else
		{
			byte b1 = decodingTable[data.charAt(data.length() - 4)];
			byte b2 = decodingTable[data.charAt(data.length() - 3)];
			byte b3 = decodingTable[data.charAt(data.length() - 2)];
			byte b4 = decodingTable[data.charAt(data.length() - 1)];
			bytes[bytes.length - 3] = (byte)(b1 << 2 | b2 >> 4);
			bytes[bytes.length - 2] = (byte)(b2 << 4 | b3 >> 2);
			bytes[bytes.length - 1] = (byte)(b3 << 6 | b4);
		}
		return bytes;
	}

	public static int decode(String data, OutputStream out)
		throws IOException
	{
		if (data.length() == 0)
			return 0;
		int length;
		if (data.charAt(data.length() - 2) == '=')
			length = (data.length() / 4 - 1) * 3 + 1;
		else
		if (data.charAt(data.length() - 1) == '=')
			length = (data.length() / 4 - 1) * 3 + 2;
		else
			length = (data.length() / 4) * 3;
		int i = 0;
		for (int j = 0; i < data.length() - 4; j += 3)
		{
			byte b1 = decodingTable[data.charAt(i)];
			byte b2 = decodingTable[data.charAt(i + 1)];
			byte b3 = decodingTable[data.charAt(i + 2)];
			byte b4 = decodingTable[data.charAt(i + 3)];
			out.write(b1 << 2 | b2 >> 4);
			out.write(b2 << 4 | b3 >> 2);
			out.write(b3 << 6 | b4);
			i += 4;
		}

		if (data.charAt(data.length() - 2) == '=')
		{
			byte b1 = decodingTable[data.charAt(data.length() - 4)];
			byte b2 = decodingTable[data.charAt(data.length() - 3)];
			out.write(b1 << 2 | b2 >> 4);
		} else
		if (data.charAt(data.length() - 1) == '=')
		{
			byte b1 = decodingTable[data.charAt(data.length() - 4)];
			byte b2 = decodingTable[data.charAt(data.length() - 3)];
			byte b3 = decodingTable[data.charAt(data.length() - 2)];
			out.write(b1 << 2 | b2 >> 4);
			out.write(b2 << 4 | b3 >> 2);
		} else
		{
			byte b1 = decodingTable[data.charAt(data.length() - 4)];
			byte b2 = decodingTable[data.charAt(data.length() - 3)];
			byte b3 = decodingTable[data.charAt(data.length() - 2)];
			byte b4 = decodingTable[data.charAt(data.length() - 1)];
			out.write(b1 << 2 | b2 >> 4);
			out.write(b2 << 4 | b3 >> 2);
			out.write(b3 << 6 | b4);
		}
		return length;
	}

	static 
	{
		decodingTable = new byte[128];
		for (int i = 65; i <= 90; i++)
			decodingTable[i] = (byte)(i - 65);

		for (int i = 97; i <= 122; i++)
			decodingTable[i] = (byte)((i - 97) + 26);

		for (int i = 48; i <= 57; i++)
			decodingTable[i] = (byte)((i - 48) + 52);

		decodingTable[43] = 62;
		decodingTable[47] = 63;
	}
}