base64 study

src_biz_source_code_base64Coder_Base64Coder.java

// Copyright 2003-2010 Christian d'Heureuse, Inventec Informatik AG, Zurich, Switzerland
// www.source-code.biz, www.inventec.ch/chdh
//
// This module is multi-licensed and may be used under the terms
// of any of the following licenses:
//
//  EPL, Eclipse Public License, V1.0 or later, http://www.eclipse.org/legal
//  LGPL, GNU Lesser General Public License, V2.1 or later, http://www.gnu.org/licenses/lgpl.html
//  GPL, GNU General Public License, V2 or later, http://www.gnu.org/licenses/gpl.html
//  AL, Apache License, V2.0 or later, http://www.apache.org/licenses
//  BSD, BSD License, http://www.opensource.org/licenses/bsd-license.php
//  MIT, MIT License, http://www.opensource.org/licenses/MIT
//
// Please contact the author if you need another license.
// This module is provided "as is", without warranties of any kind.

package biz.source_code.base64Coder;

/**
 * A Base64 encoder/decoder.
 * 
 * <p>
 * This class is used to encode and decode data in Base64 format as described in
 * RFC 1521.
 * 
 * <p>
 * Project home page: <a
 * href="http://www.source-code.biz/base64coder/java/">www.
 * source-code.biz/base64coder/java</a><br>
 * Author: Christian d'Heureuse, Inventec Informatik AG, Zurich, Switzerland<br>
 * Multi-licensed: EPL / LGPL / GPL / AL / BSD / MIT.
 */
public class Base64Coder {

	// The line separator string of the operating system.
	private static final String systemLineSeparator = System
			.getProperty("line.separator");

	// Mapping table from 6-bit nibbles to Base64 characters.
	private static final char[] map1 = new char[64];
	static {
		int i = 0;
		for (char c = 'A'; c <= 'Z'; c++)
			map1[i++] = c;
		for (char c = 'a'; c <= 'z'; c++)
			map1[i++] = c;
		for (char c = '0'; c <= '9'; c++)
			map1[i++] = c;
		map1[i++] = '+';
		map1[i++] = '/';
	}

	// Mapping table from Base64 characters to 6-bit nibbles.
	private static final byte[] map2 = new byte[128];
	static {
		for (int i = 0; i < map2.length; i++)
			map2[i] = -1;
		for (int i = 0; i < 64; i++)
			map2[map1[i]] = (byte) i;
	}

	/**
	 * Encodes a string into Base64 format. No blanks or line breaks are
	 * inserted.
	 * 
	 * @param s
	 *            A String to be encoded.
	 * @return A String containing the Base64 encoded data.
	 */
	public static String encodeString(String s) {
		return new String(encode(s.getBytes()));
	}

	/**
	 * Encodes a byte array into Base 64 format and breaks the output into lines
	 * of 76 characters. This method is compatible with
	 * <code>sun.misc.BASE64Encoder.encodeBuffer(byte[])</code>.
	 * 
	 * @param in
	 *            An array containing the data bytes to be encoded.
	 * @return A String containing the Base64 encoded data, broken into lines.
	 */
	public static String encodeLines(byte[] in) {
		return encodeLines(in, 0, in.length, 76, systemLineSeparator);
	}

	/**
	 * Encodes a byte array into Base 64 format and breaks the output into
	 * lines.
	 * 
	 * @param in
	 *            An array containing the data bytes to be encoded.
	 * @param iOff
	 *            Offset of the first byte in <code>in</code> to be processed.
	 * @param iLen
	 *            Number of bytes to be processed in <code>in</code>, starting
	 *            at <code>iOff</code>.
	 * @param lineLen
	 *            Line length for the output data. Should be a multiple of 4.
	 * @param lineSeparator
	 *            The line separator to be used to separate the output lines.
	 * @return A String containing the Base64 encoded data, broken into lines.
	 */
	public static String encodeLines(byte[] in, int iOff, int iLen,
			int lineLen, String lineSeparator) {
		int blockLen = (lineLen * 3) / 4;
		if (blockLen <= 0)
			throw new IllegalArgumentException();
		int lines = (iLen + blockLen - 1) / blockLen;
		int bufLen = ((iLen + 2) / 3) * 4 + lines * lineSeparator.length();
		StringBuilder buf = new StringBuilder(bufLen);
		int ip = 0;
		while (ip < iLen) {
			int l = Math.min(iLen - ip, blockLen);
			buf.append(encode(in, iOff + ip, l));
			buf.append(lineSeparator);
			ip += l;
		}
		return buf.toString();
	}

	/**
	 * Encodes a byte array into Base64 format. No blanks or line breaks are
	 * inserted in the output.
	 * 
	 * @param in
	 *            An array containing the data bytes to be encoded.
	 * @return A character array containing the Base64 encoded data.
	 */
	public static char[] encode(byte[] in) {
		return encode(in, 0, in.length);
	}

	/**
	 * Encodes a byte array into Base64 format. No blanks or line breaks are
	 * inserted in the output.
	 * 
	 * @param in
	 *            An array containing the data bytes to be encoded.
	 * @param iLen
	 *            Number of bytes to process in <code>in</code>.
	 * @return A character array containing the Base64 encoded data.
	 */
	public static char[] encode(byte[] in, int iLen) {
		return encode(in, 0, iLen);
	}

	/**
	 * Encodes a byte array into Base64 format. No blanks or line breaks are
	 * inserted in the output.
	 * 
	 * @param in
	 *            An array containing the data bytes to be encoded.
	 * @param iOff
	 *            Offset of the first byte in <code>in</code> to be processed.
	 * @param iLen
	 *            Number of bytes to process in <code>in</code>, starting at
	 *            <code>iOff</code>.
	 * @return A character array containing the Base64 encoded data.
	 */
	public static char[] encode(byte[] in, int iOff, int iLen) {
		int oDataLen = (iLen * 4 + 2) / 3; // output length without padding
		int oLen = ((iLen + 2) / 3) * 4; // output length including padding
		char[] out = new char[oLen];
		int ip = iOff;
		int iEnd = iOff + iLen;
		int op = 0;
		while (ip < iEnd) {
			int i0 = in[ip++] & 0xff;
			int i1 = ip < iEnd ? in[ip++] & 0xff : 0;
			int i2 = ip < iEnd ? in[ip++] & 0xff : 0;
			//Verify bitwise review to explanation on this operators
			int o0 = i0 >>> 2;
			int o1 = ((i0 & 3) << 4) | (i1 >>> 4);
			int o2 = ((i1 & 0xf) << 2) | (i2 >>> 6);
			int o3 = i2 & 0x3F;
			out[op++] = map1[o0];
			out[op++] = map1[o1];
			out[op] = op < oDataLen ? map1[o2] : '=';
			op++;
			out[op] = op < oDataLen ? map1[o3] : '=';
			op++;
		}
		return out;
	}

	/**
	 * Decodes a string from Base64 format. No blanks or line breaks are allowed
	 * within the Base64 encoded input data.
	 * 
	 * @param s
	 *            A Base64 String to be decoded.
	 * @return A String containing the decoded data.
	 * @throws IllegalArgumentException
	 *             If the input is not valid Base64 encoded data.
	 */
	public static String decodeString(String s) {
		return new String(decode(s));
	}

	/**
	 * Decodes a byte array from Base64 format and ignores line separators, tabs
	 * and blanks. CR, LF, Tab and Space characters are ignored in the input
	 * data. This method is compatible with
	 * <code>sun.misc.BASE64Decoder.decodeBuffer(String)</code>.
	 * 
	 * @param s
	 *            A Base64 String to be decoded.
	 * @return An array containing the decoded data bytes.
	 * @throws IllegalArgumentException
	 *             If the input is not valid Base64 encoded data.
	 */
	public static byte[] decodeLines(String s) {
		char[] buf = new char[s.length()];
		int p = 0;
		for (int ip = 0; ip < s.length(); ip++) {
			char c = s.charAt(ip);
			if (c != ' ' && c != '\r' && c != '\n' && c != '\t')
				buf[p++] = c;
		}
		return decode(buf, 0, p);
	}

	/**
	 * Decodes a byte array from Base64 format. No blanks or line breaks are
	 * allowed within the Base64 encoded input data.
	 * 
	 * @param s
	 *            A Base64 String to be decoded.
	 * @return An array containing the decoded data bytes.
	 * @throws IllegalArgumentException
	 *             If the input is not valid Base64 encoded data.
	 */
	public static byte[] decode(String s) {
		return decode(s.toCharArray());
	}

	/**
	 * Decodes a byte array from Base64 format. No blanks or line breaks are
	 * allowed within the Base64 encoded input data.
	 * 
	 * @param in
	 *            A character array containing the Base64 encoded data.
	 * @return An array containing the decoded data bytes.
	 * @throws IllegalArgumentException
	 *             If the input is not valid Base64 encoded data.
	 */
	public static byte[] decode(char[] in) {
		return decode(in, 0, in.length);
	}

	/**
	 * Decodes a byte array from Base64 format. No blanks or line breaks are
	 * allowed within the Base64 encoded input data.
	 * 
	 * @param in
	 *            A character array containing the Base64 encoded data.
	 * @param iOff
	 *            Offset of the first character in <code>in</code> to be
	 *            processed.
	 * @param iLen
	 *            Number of characters to process in <code>in</code>, starting
	 *            at <code>iOff</code>.
	 * @return An array containing the decoded data bytes.
	 * @throws IllegalArgumentException
	 *             If the input is not valid Base64 encoded data.
	 */
	public static byte[] decode(char[] in, int iOff, int iLen) {
		if (iLen % 4 != 0)
			throw new IllegalArgumentException(
					"Length of Base64 encoded input string is not a multiple of 4.");
		while (iLen > 0 && in[iOff + iLen - 1] == '=')
			iLen--;
		int oLen = (iLen * 3) / 4;
		byte[] out = new byte[oLen];
		int ip = iOff;
		int iEnd = iOff + iLen;
		int op = 0;
		while (ip < iEnd) {
			int i0 = in[ip++];
			int i1 = in[ip++];
			int i2 = ip < iEnd ? in[ip++] : 'A';
			int i3 = ip < iEnd ? in[ip++] : 'A';
			if (i0 > 127 || i1 > 127 || i2 > 127 || i3 > 127)
				throw new IllegalArgumentException(
						"Illegal character in Base64 encoded data.");
			int b0 = map2[i0];
			int b1 = map2[i1];
			int b2 = map2[i2];
			int b3 = map2[i3];
			if (b0 < 0 || b1 < 0 || b2 < 0 || b3 < 0)
				throw new IllegalArgumentException(
						"Illegal character in Base64 encoded data.");
			int o0 = (b0 << 2) | (b1 >>> 4);
			int o1 = ((b1 & 0xf) << 4) | (b2 >>> 2);
			int o2 = ((b2 & 3) << 6) | b3;
			out[op++] = (byte) o0;
			if (op < oLen)
				out[op++] = (byte) o1;
			if (op < oLen)
				out[op++] = (byte) o2;
		}
		return out;
	}

	// Dummy constructor.
	private Base64Coder() {
	}

} // end class Base64Coder

src_biz_source_code_base64Coder_BitwiseReview.java

package biz.source_code.base64Coder;

/**
 * Check for reference
 * http://docs.oracle.com/javase/specs/jls/se7/html/jls-15.html#jls-15.19
 * http://en.wikipedia.org/wiki/Bitwise_operation#Shifts_in_Java
 * 
 * @author jzamora02
 *
 */
public class BitwiseReview {

	private static final String ZEROS = "00000";
	
	public static void main(String... args){

		int bitmask = 0x000F;
	    int val = 0x2222;
	    
	    // prints "2"	    
	    System.out.println("Bitmask " + (val & bitmask));
   
	    val = 0xF00F;
	    //The unsigned right shift operator ">>>" shifts a zero into the leftmost 
	    //position, while the leftmost position after ">>" depends on sign extension.
	    for(int i=0;i<10;i++){
	    	System.out.format(i+" %h - ",val); //%n platform independent newline character
	    	System.out.format("%d%n",val); //%n platform independent newline character
	    	val = val >>> 1; //BE CAREFULL YOU ARE SHIFTING ONE POSITION	    	
	    }
	    
	    //Keep in mind
	    //If n is positive, then the result is the same as that of n >> s.
	    //If n is negative and the type of the left-hand operand is int, then the result is equal to that of the expression (n >> s) + (2 << ~s).
	    //If n is negative and the type of the left-hand operand is long, then the result is equal to that of the expression (n >> s) + (2L << ~s).
	    
	    
	    val = 0xF00F;
	    //The unsigned right shift operator ">>>" shifts a zero into the leftmost 
	    //position, while the leftmost position after ">>" depends on sign extension.
	    for(int j=0;j<10;j++){
	    	System.out.format(j+" %h - ",val); //%n platform independent newline character
	    	System.out.format("%d%n",val); //%n platform independent newline character
	    	val = val >> 1;	    	
	    }	    

	    System.out.println(Integer.toBinaryString(0xF00F));
	    System.out.println(Integer.toBinaryString(0xF00F>>>1));
	    
	    System.out.println(Integer.toBinaryString(-1));
	    System.out.println(Integer.toBinaryString(-1>>>30));
	    
	    //See http://docs.oracle.com/javase/specs/jls/se7/html/jls-15.html#jls-15.19
    	//If the promoted type of the left-hand operand is int, only the five lowest-order 
	    //bits of the right-hand operand are used as the shift distance. It is as if the right-hand operand 
	    //were subjected to a bitwise logical AND operator & (�15.22.1) with the mask value 0x1f (0b11111). 
	    //The shift distance actually used is therefore always in the range 0 to 31, INCLUSIVE.
	    //that is -1 >>> 32 is equivalent to -1 >>> 0 and -1 >>> 33 is equivalent to -1 >>> 1 and,
	    //especially confusing, -1 >>> -1 is equivalent to -1 >>> 31
	    System.out.println(Integer.toBinaryString(-1>>>32));
	    
	}
	
	
	
	/**
	 * Formats the string to the specified length using the padString and padded either left (PAD_LEFT) or right (PAD_RIGHT)
	 * @param str
	 * @param len
	 * @param padStr
	 * @param padLeft true if pad left, false otherwise (use constants PAD_LEFT, PAD_RIGHT)
	 * @return
	 */
	private static String formatStrLen(final String str, final int len) {
		return str == null || str.length() == 0 ? ZEROS.substring(0, len) :
				str.length() >= len ? str : ZEROS.substring(str.length(), len) + str;
	}
    
    
}

src_operations_file_Tipical.java

package operations.file;


import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Arrays;
import java.util.List;
import java.util.Scanner;

/**
 * Java 7 File IO
 * @author jzamora02
 *
 */
public class Tipical {
  
  public static void main(String... aArgs) throws IOException{
	  Tipical text = new Tipical();
    
    //treat as a small file
    List<String> lines = text.readSmallTextFile(FILE_NAME);
    //log(lines);    
    //text.writeSmallTextFile(lines, FILE_NAME);
    
    //treat as a large file - use some buffering
    //text.readLargerTextFile(FILE_NAME);
    //lines = Arrays.asList("Down to the Waterline", "Water of Love");
    text.writeLargerTextFile(OUTPUT_FILE_NAME, lines);   

  }

  final static String FILE_NAME = "C:\\temp\\test.txt";
  final static String OUTPUT_FILE_NAME = "C:\\temp\\output.txt";
  final static Charset ENCODING = StandardCharsets.UTF_8;
  
  //For smaller files

  /**
   Note: the javadoc of Files.readAllLines says it's intended for small
   files. But its implementation uses buffering, so it's likely good 
   even for fairly large files.
  */  
  List<String> readSmallTextFile(String aFileName) throws IOException {
    Path path = Paths.get(aFileName);
    return Files.readAllLines(path, ENCODING);
  }
  
  void writeSmallTextFile(List<String> aLines, String aFileName) throws IOException {
    Path path = Paths.get(aFileName);
    Files.write(path, aLines, ENCODING);
  }

  //For larger files
  
  void readLargerTextFile(String aFileName) throws IOException {
    Path path = Paths.get(aFileName);
    try (Scanner scanner =  new Scanner(path, ENCODING.name())){
      while (scanner.hasNextLine()){
        //process each line in some way
        log(scanner.nextLine());
      }      
    }
  }
  
  void readLargerTextFileAlternate(String aFileName) throws IOException {
    Path path = Paths.get(aFileName);
    try (BufferedReader reader = Files.newBufferedReader(path, ENCODING)){
      String line = null;
      while ((line = reader.readLine()) != null) {
        //process each line in some way
        log(line);
      }      
    }
  }
  
  void writeLargerTextFile(String aFileName, List<String> aLines) throws IOException {
    Path path = Paths.get(aFileName);
    try (BufferedWriter writer = Files.newBufferedWriter(path, ENCODING)){
      for(String line : aLines){
        
        splitLines(60,line,writer);
        
      }
    }
  }

  void splitLines(int length,String line,BufferedWriter writer) throws IOException
  {
  	int index = 0;
  	String temporal = "";
  	if (line.length() > length) {
  		
  		index = line.indexOf(" ",length);
  		if(index > 0){
  			temporal = line.substring(0,index);
  		} else {
  			temporal = line.substring(0,length);
  			index = length;
  		}

  		writer.write(temporal);
  		writer.newLine();

  		splitLines( length,line.substring(index+1,line.length()),writer );

  	} else {
  		writer.write(line);
  		writer.newLine();
  		return;
  	}

  }



  private static void log(Object aMsg){
    System.out.println(String.valueOf(aMsg));
  }
  
} 

src_samples_Base64FileDecoder.java

// Sample program to decode a Base64 text file into a binary file.
// Author: Christian d'Heureuse (www.source-code.biz)
package samples;
import biz.source_code.base64Coder.Base64Coder;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.OutputStream;

public class Base64FileDecoder {

public static void main (String args[]) throws IOException {
   if (args.length != 2) {
      System.out.println ("Command line parameters: inputFileName outputFileName");
      System.exit (9); }
   decodeFile (args[0], args[1]); }

private static void decodeFile (String inputFileName, String outputFileName) throws IOException {
   BufferedReader in = null;
   BufferedOutputStream out = null;
   try {
      in = new BufferedReader(new FileReader(inputFileName));
      out = new BufferedOutputStream(new FileOutputStream(outputFileName));
      decodeStream (in, out);
      out.flush(); }
    finally {
      if (in != null) in.close();
      if (out != null) out.close(); }}

private static void decodeStream (BufferedReader in, OutputStream out) throws IOException {
   while (true) {
      String s = in.readLine();
      if (s == null) break;
      byte[] buf = Base64Coder.decodeLines(s);
      out.write (buf); }}

} // end class Base64FileDecoder

src_samples_Base64FileEncoder.java

// Sample program to encode a binary file into a Base64 text file.
// Author: Christian d'Heureuse (www.source-code.biz)
package samples;

import biz.source_code.base64Coder.Base64Coder;
import java.io.BufferedInputStream;
import java.io.BufferedWriter;
import java.io.FileInputStream;
import java.io.FileWriter;
import java.io.InputStream;
import java.io.IOException;

public class Base64FileEncoder {

	public static void main(String args[]) throws IOException {
		if (args.length != 2) {
			System.out
					.println("Command line parameters: inputFileName outputFileName");
			System.exit(9);
		}
		encodeFile(args[0], args[1]);
	}

	public static void encodeFile(String inputFileName, String outputFileName)
			throws IOException {
		BufferedInputStream in = null;
		BufferedWriter out = null;
		try {
			in = new BufferedInputStream(new FileInputStream(inputFileName));
			out = new BufferedWriter(new FileWriter(outputFileName));
			encodeStream(in, out);
			out.flush();
		} finally {
			if (in != null)
				in.close();
			if (out != null)
				out.close();
		}
	}

	public static void encodeStream(InputStream in, BufferedWriter out)
			throws IOException {
		int lineLength = 72;
		byte[] buf = new byte[lineLength / 4 * 3];
		while (true) {
			int len = in.read(buf);
			if (len <= 0)
				break;
			out.write(Base64Coder.encode(buf, 0, len));
			out.newLine();
		}
	}

} // end class Base64FileEncoder

src_test_TestBase64Coder.java

// Tests for the Base64Coder class.
package test;

import biz.source_code.base64Coder.Base64Coder;
import java.util.Random;
import static org.junit.Assert.fail;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertArrayEquals;
import org.junit.Test;

public class TestBase64Coder {

// Test Base64Coder with constant strings.

@Test
public void test1() {
   check ("Aladdin:open sesame", "QWxhZGRpbjpvcGVuIHNlc2FtZQ==");  // example from RFC 2617
   check ("", "");
   check ("Man", "TWFu"); //Wikipedia example
   check ("1", "MQ==");
   check ("22", "MjI=");
   check ("333", "MzMz");
   check ("4444", "NDQ0NA==");
   check ("55555", "NTU1NTU=");
   check ("abc:def", "YWJjOmRlZg=="); }

private static void check (String plainText, String base64Text) 
{
   String s1 = Base64Coder.encodeString(plainText);
   String s2 = Base64Coder.decodeString(base64Text);
   if (!s1.equals(base64Text) || !s2.equals(plainText))
      fail ("Check failed for \""+plainText+"\" / \""+base64Text+"\"."); 
}



// Test Base64Coder against sun.misc.BASE64Encoder/Decoder with random data.
// Line length below 76.
@Test
public void test2() throws Exception {
   final int maxLineLen = 76 - 1;                          // the Sun encoder adds a CR/LF when a line is longer
   final int maxDataBlockLen = (maxLineLen*3) / 4;
   sun.misc.BASE64Encoder sunEncoder = new sun.misc.BASE64Encoder();
   sun.misc.BASE64Decoder sunDecoder = new sun.misc.BASE64Decoder();
   Random rnd = new Random(0x538afb92);
   for (int i=0; i<50000; i++) {
      int len = rnd.nextInt(maxDataBlockLen+1);
      byte[] b0 = new byte[len];
      rnd.nextBytes(b0);
      String e1 = new String(Base64Coder.encode(b0));
      String e2 = sunEncoder.encode(b0);
      assertEquals (e2, e1);
      byte[] b1 = Base64Coder.decode(e1);
      byte[] b2 = sunDecoder.decodeBuffer(e2);
      assertArrayEquals (b0, b1);
      assertArrayEquals (b0, b2); }}

// Test Base64Coder line encoding/decoding against sun.misc.BASE64Encoder/Decoder
// with random data.
@Test
public void test3() throws Exception {
   final int maxDataBlockLen = 512;
   sun.misc.BASE64Encoder sunEncoder = new sun.misc.BASE64Encoder();
   sun.misc.BASE64Decoder sunDecoder = new sun.misc.BASE64Decoder();
   Random rnd = new Random(0x39ac7d6e);
   for (int i=0; i<10000; i++) {
      int len = rnd.nextInt(maxDataBlockLen+1);
      byte[] b0 = new byte[len];
      rnd.nextBytes(b0);
      String e1 = new String(Base64Coder.encodeLines(b0));
      String e2 = sunEncoder.encodeBuffer(b0);
      assertEquals (e2, e1);
      byte[] b1 = Base64Coder.decodeLines(e1);
      byte[] b2 = sunDecoder.decodeBuffer(e2);
      assertArrayEquals (b0, b1);
      assertArrayEquals (b0, b2); }}

} // end class TestBase64Coder