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mqtt/org/eclipse/paho/mqttv5/client/security/SimpleBase64Encoder.java

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+/*******************************************************************************
+ * Copyright (c) 2009, 2014 IBM Corp.
+ *
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v2.0
+ * and Eclipse Distribution License v1.0 which accompany this distribution. 
+ *
+ * The Eclipse Public License is available at 
+ *    https://www.eclipse.org/legal/epl-2.0
+ * and the Eclipse Distribution License is available at 
+ *   https://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * Contributors:
+ *    Dave Locke - initial API and implementation and/or initial documentation
+ */
+package org.eclipse.paho.mqttv5.client.security;
+
+public class SimpleBase64Encoder {
+
+	// if this string is changed, then the decode method must also be adapted.
+	private static final String PWDCHARS_STRING = "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
+	private static final char[] PWDCHARS_ARRAY = PWDCHARS_STRING.toCharArray();
+
+	/**
+	 * Encodes an array of byte into a string of printable ASCII characters
+	 * using a base-64 encoding.
+	 * @param bytes The array of bytes to e encoded
+	 * @return The encoded array.
+	 */
+	public static String encode(byte[] bytes) {
+		// Allocate a string buffer.
+		int len = bytes.length;
+		final StringBuffer encoded = new StringBuffer((len+2)/3*4);		
+		int i=0;
+		int j=len;
+		while(j>=3){
+			encoded.append(to64((((bytes[i] & 0xff) << 16)
+				| (int) ((bytes[i+1] & 0xff) << 8) | (int) (bytes[i+2] & 0xff)),4));
+			i+=3;
+			j-=3;
+		}
+		// j==2 | j==1 | j==0
+		if(j==2) {
+			// there is a rest of 2 bytes. This encodes into 3 chars.
+			encoded.append(to64(((bytes[i] &0xff)<<8) | ((bytes[i+1] & 0xff)),3));
+		}
+		if(j==1) {
+			// there is a rest of 1 byte. This encodes into 1 char.
+			encoded.append(to64(((bytes[i] & 0xff)),2));
+		}
+		return encoded.toString();
+	}
+
+	public static byte[] decode(String string) {
+		byte[] encoded=string.getBytes();
+		int len=encoded.length;
+		byte[] decoded=new byte[len*3/4];
+		int i=0;
+		int j=len;
+		int k=0;
+		while(j>=4) {
+			long d=from64(encoded, i, 4);
+			j-=4;
+			i+=4;
+			for(int l=2;l>=0;l--) {
+				decoded[k+l]=(byte) (d & 0xff);
+				d=d >>8;
+			}
+			k+=3;
+		}
+		// j==3 | j==2 
+		if(j==3) {
+			long d=from64(encoded, i, 3);
+			for(int l=1;l>=0;l--) {
+				decoded[k+l]=(byte) (d & 0xff);
+				d=d >>8;
+			}			
+		}
+		if(j==2) {
+			long d=from64(encoded, i, 2);
+			decoded[k]=(byte) (d & 0xff);
+		}			
+		return decoded;
+	}
+
+	/* the core conding routine. Translates an input integer into
+	 * a string of the given length.*/
+	private final static String to64(long input, int size) {
+		final StringBuffer result = new StringBuffer(size);
+		while (size > 0) {
+			size--;
+			result.append(PWDCHARS_ARRAY[((int) (input & 0x3f))]);
+			input = input >> 6;
+		}
+		return result.toString();
+	}
+
+	/*
+	 * The reverse operation of to64
+	 */
+	private final static long from64(byte[] encoded, int idx, int size) {
+		long res=0;
+		int f=0;
+		while(size>0) {
+			size--;
+			long r=0;
+			// convert encoded[idx] back into a 6-bit value.
+			byte d=encoded[idx++];
+			if(d=='/') {
+				r=1;
+			}
+			if(d>='0' && d<='9') {
+				r=2+d-'0';
+			}
+			if(d>='A' && d<='Z') {
+				r=12+d-'A';
+			}
+			if(d>='a' && d<='z') {
+				r=38+d-'a';
+			}
+			res=res+((long)r << f);
+			f+=6;
+		}
+		return res;
+	}
+
+}