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package com.ksyun.api.sdk.utils;

import java.io.UnsupportedEncodingException;

public class Base64Helper {
 
    private static final String BASE64_CODE = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
            + "abcdefghijklmnopqrstuvwxyz" + "0123456789" + "+/";
    
    private static final int[] BASE64_DECODE = {
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
        52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1,
        -1,  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, -1, -1, -1, -1, -1,
        -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
        41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    };
    
    private static byte[] zeroPad(int length, byte[] bytes) {
        byte[] padded = new byte[length];
        System.arraycopy(bytes, 0, padded, 0, bytes.length);
        return padded;
    }

    public synchronized static String encode(byte[] buff) {
    	if (null == buff)
    		return null;
    	
    	StringBuilder strBuilder = new StringBuilder("");
    	int paddingCount = (3 - (buff.length % 3)) % 3;
        byte[] stringArray = zeroPad(buff.length + paddingCount, buff);
        for (int i = 0; i < stringArray.length; i += 3) {
            int j = ((stringArray[i] & 0xff) << 16) +
                ((stringArray[i + 1] & 0xff) << 8) + 
                (stringArray[i + 2] & 0xff);    
            strBuilder.append(BASE64_CODE.charAt((j >> 18) & 0x3f));
            strBuilder.append(BASE64_CODE.charAt((j >> 12) & 0x3f));
            strBuilder.append(BASE64_CODE.charAt((j >> 6) & 0x3f));
            strBuilder.append(BASE64_CODE.charAt(j & 0x3f));
        }
        int intPos = strBuilder.length();
        for (int i = paddingCount; i > 0; i --) {
            strBuilder.setCharAt(intPos - i, '=');
        }
        
        return strBuilder.toString();
    }
    
    public synchronized static String encode(String string, String encoding)
    	throws UnsupportedEncodingException {
    	if (null == string || null == encoding)
    		return null;
        byte[] stringArray = string.getBytes(encoding);
        return encode(stringArray);
    }

    public synchronized static String decode(String string, String encoding) throws 
    	UnsupportedEncodingException{
    	if (null == string || null == encoding)
    		return null;
    	int posIndex = 0;
        int decodeLen = string.endsWith( "==" ) ? (string.length() - 2) : 
        	string.endsWith( "=" ) ? (string.length() - 1) : string.length();
        byte[] buff = new byte[decodeLen *3 / 4];
        int count4 = decodeLen - decodeLen %4;
        for(int i = 0; i< count4; i += 4){
            int c0 = BASE64_DECODE[string.charAt( i )];
            int c1 = BASE64_DECODE[string.charAt( i + 1)];
            int c2 = BASE64_DECODE[string.charAt( i + 2)];
            int c3 = BASE64_DECODE[string.charAt( i + 3)];
            buff[posIndex ++ ] = (byte)(((c0 << 2) | (c1 >> 4)) & 0xFF);
            buff[posIndex ++ ] = (byte)((((c1 & 0xF) << 4) | (c2 >> 2)) & 0xFF);
            buff[posIndex ++ ] = (byte)((((c2 & 3) << 6) | c3) & 0xFF);
        }
        if (2 <= decodeLen%4) {
            int c0 = BASE64_DECODE[string.charAt(count4)];
            int c1 = BASE64_DECODE[string.charAt(count4 + 1)];
            buff[posIndex ++ ] = (byte)(((c0 << 2) | (c1 >> 4)) & 0xFF);
            if (3 == decodeLen%4) {
                int c2 = BASE64_DECODE[string.charAt( count4 + 2)];
                buff[posIndex ++ ] = (byte)((((c1 & 0xF) << 4) | (c2 >> 2)) & 0xFF);
            }
        }
        return new String(buff, encoding);
    }
}