base64encoder.java

数字图书馆的互操作接口

// Base64Encoder.java
// $Id: Base64Encoder.java,v 1.1 1999/07/17 01:53:29 melnik Exp $
// (c) COPYRIGHT MIT and INRIA, 1996.
// Please first read the full copyright statement in file COPYRIGHT.html

package org.w3c.tools.codec ;

import java.io.* ;

/**
 * BASE64 encoder implementation.
 * This object takes as parameter an input stream and an output stream. It
 * encodes the input stream, using the BASE64 encoding rules, as defined
 * in <a href="http://ds.internic.net/rfc/rfc1521.txt">MIME specification</a>
 * and emit the resulting data to the output stream.
 * @see w3c.tools.codec.Base64Decoder
 */

public class Base64Encoder {
    private static final int BUFFER_SIZE = 1024 ;
    private static byte encoding[] =
    {
	'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',		// 0-7
	'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',		// 8-15
	'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 	// 16-23
	'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',		// 24-31
	'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',		// 32-39
	'o', 'p', 'q', 'r', 's', 't', 'u', 'v',		// 40-47
	'w', 'x', 'y', 'z', '0', '1', '2', '3',		// 48-55
	'4', '5', '6', '7', '8', '9', '+', '/',		// 56-63
	'='						// 64
    };

    InputStream  in  = null ;
    OutputStream out = null ;
    boolean      stringp = false ;

    private final int get1(byte buf[], int off) {
	return (buf[off] & 0xfc) >> 2 ;
    }

    private final int get2(byte buf[], int off) {
	return ((buf[off]&0x3) << 4) | ((buf[off+1]&0xf0) >>> 4) ;
    }

    private final int get3(byte buf[], int off) {
	return ((buf[off+1] & 0x0f) << 2) | ((buf[off+2] & 0xc0) >>> 6) ;
    }

    private static final int get4(byte buf[], int off) {
	return buf[off+2] & 0x3f ;
    }

    /**
     * Process the data: encode the input stream to the output stream.
     * This method runs through the input stream, encoding it to the output
     * stream.
     * @exception IOException If we weren't able to access the input stream or
     *    the output stream.
     */

    public void process ()
	throws IOException
    {
	byte buffer[] = new byte[BUFFER_SIZE] ;
	int  got      = -1 ;
	int  off      = 0 ;
	int  count    = 0 ;
	while ((got = in.read(buffer, off, BUFFER_SIZE-off)) > 0) {
	    if ( got >= 3 ) {
		got += off;
		off  = 0;
		while (off + 3 <= got) {
		    int c1 = get1(buffer,off) ;
		    int c2 = get2(buffer,off) ;
		    int c3 = get3(buffer,off) ;
		    int c4 = get4(buffer,off) ;
		    switch (count) {
		      case 73:
			  out.write(encoding[c1]);
			  out.write(encoding[c2]);
			  out.write(encoding[c3]);
			  out.write ('\n') ;
			  out.write(encoding[c4]) ;
			  count = 1 ;
			  break ;
		      case 74:
			  out.write(encoding[c1]);
			  out.write(encoding[c2]);
			  out.write ('\n') ;
			  out.write(encoding[c3]);
			  out.write(encoding[c4]) ;
			  count = 2 ;
			  break ;
		      case 75:
			  out.write(encoding[c1]);
			  out.write ('\n') ;
			  out.write(encoding[c2]);
			  out.write(encoding[c3]);
			  out.write(encoding[c4]) ;
			  count = 3 ;
			  break ;
		      case 76:
			  out.write('\n') ;
			  out.write(encoding[c1]);
			  out.write(encoding[c2]);
			  out.write(encoding[c3]);
			  out.write(encoding[c4]) ;
			  count = 4 ;
			  break ;
		      default:
			  out.write(encoding[c1]);
			  out.write(encoding[c2]);
			  out.write(encoding[c3]);
			  out.write(encoding[c4]) ;
			  count += 4 ;
			  break ;
		    }
		    off += 3 ;
		}
		// Copy remaining bytes to beginning of buffer:
		for ( int i = 0 ; i < 3 ;i++)
		    buffer[i] = (i < got-off) ? buffer[off+i] : ((byte) 0) ;
		off = got-off ;
	    } else {
		// Total read amount is less then 3 bytes:
		off += got;
	    }
	}
	// Manage the last bytes, from 0 to off:
	switch (off) {
	  case 1:
	      out.write(encoding[get1(buffer, 0)]) ;
	      out.write(encoding[get2(buffer, 0)]) ;
	      out.write('=') ;
	      out.write('=') ;
	      break ;
	  case 2:
	      out.write(encoding[get1(buffer, 0)]);
	      out.write(encoding[get2(buffer, 0)]);
	      out.write(encoding[get3(buffer, 0)]);
	      out.write('=');
	}
	return ;
    }

    /**
     * Encode the content of this encoder, as a string.
     * This methods encode the String content, that was provided at creation
     * time, following the BASE64 rules, as specified in the rfc1521.
     * @return A String, reprenting the encoded content of the input String.
     */

    public String processString () {
	if ( ! stringp )
	    throw new RuntimeException (this.getClass().getName()
					+ "[processString]"
					+ "invalid call (not a String)");
	try {
	    process() ;
	} catch (IOException e) {
	}
	return ((ByteArrayOutputStream) out).toString() ;
    }

    /**
     * Create a new Base64 encoder, to encode the given string.
     * @param input The String to be encoded.
     */

    public Base64Encoder (String input) {
	byte bytes[] = input.getBytes () ;
	this.stringp = true ;
	this.in      = new ByteArrayInputStream(bytes) ;
	this.out     = new ByteArrayOutputStream () ;
    }

    /**
     * Create a new Base64 encoder, encoding input to output.
     * @param in The input stream to be encoded.
     * @param out The output stream, to write encoded data to.
     */

    public Base64Encoder (InputStream in, OutputStream out) {
	this.in      = in ;
	this.out     = out ;
	this.stringp = false ;
    }

    /**
     * Testing the encoder.
     * Run with one argument, prints the encoded version of it.
     */

    public static void main (String args[]) {
    /*
	if ( args.length != 1 ) {
	    System.out.println ("Base64Encoder <string>") ;
	    System.exit (0) ;
	}
    */
	Base64Encoder b = new Base64Encoder ("ajfas;7ldke,jas;7ldk,jas;dlkjsa;dflkjsadf;lk,jsadf;lkasjdf;lkajs;alksjd;a7slkj;7salkdejf;7salkdejf;s7adkjwplkjoieuoeirujakldejflasdkejflasdfjoasidjfasdoijasdfoaskihdjfasoidfjwejjnz123245j832d23242ds23e234sdda3qfdasd23df342eewf23r45f") ;
	System.out.println ("["+b.processString()+"]") ;
	// joe:eoj -> am9lOmVvag==
	// 12345678:87654321 -> MTIzNDU2Nzg6ODc2NTQzMjE=
    }
}