base32.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:   Base32.java

package org.gudy.azureus2.core3.util;


public class Base32
{

	private static final String base32Chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
	private static final int base32Lookup[] = {
		255, 255, 26, 27, 28, 29, 30, 31, 255, 255, 
		255, 255, 255, 255, 255, 255, 255, 0, 1, 2, 
		3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 
		13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 
		23, 24, 25, 255, 255, 255, 255, 255, 255, 0, 
		1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 
		11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 
		21, 22, 23, 24, 25, 255, 255, 255, 255, 255
	};

	public Base32()
	{
	}

	public static String encode(byte bytes[])
	{
		int i = 0;
		int index = 0;
		int digit = 0;
		StringBuffer base32 = new StringBuffer(((bytes.length + 7) * 8) / 5);
		for (; i < bytes.length; base32.append("ABCDEFGHIJKLMNOPQRSTUVWXYZ234567".charAt(digit)))
		{
			int currByte = bytes[i] < 0 ? bytes[i] + 256 : ((int) (bytes[i]));
			if (index > 3)
			{
				int nextByte;
				if (i + 1 < bytes.length)
					nextByte = bytes[i + 1] < 0 ? bytes[i + 1] + 256 : ((int) (bytes[i + 1]));
				else
					nextByte = 0;
				digit = currByte & 255 >> index;
				index = (index + 5) % 8;
				digit <<= index;
				digit |= nextByte >> 8 - index;
				i++;
				continue;
			}
			digit = currByte >> 8 - (index + 5) & 0x1f;
			index = (index + 5) % 8;
			if (index == 0)
				i++;
		}

		return base32.toString();
	}

	public static byte[] decode(String base32)
	{
		byte bytes[] = new byte[(base32.length() * 5) / 8];
		if (bytes.length == 0)
			return bytes;
		int i = 0;
		int index = 0;
		int offset = 0;
		for (; i < base32.length(); i++)
		{
			int lookup = base32.charAt(i) - 48;
			if (lookup < 0 || lookup >= base32Lookup.length)
				continue;
			int digit = base32Lookup[lookup];
			if (digit == 255)
				continue;
			if (index <= 3)
			{
				index = (index + 5) % 8;
				if (index == 0)
				{
					bytes[offset] |= digit;
					if (++offset >= bytes.length)
						break;
				} else
				{
					bytes[offset] |= digit << 8 - index;
				}
				continue;
			}
			index = (index + 5) % 8;
			bytes[offset] |= digit >>> index;
			if (++offset >= bytes.length)
				break;
			bytes[offset] |= digit << 8 - index;
		}

		return bytes;
	}

}