/*
* @(#)CharacterEncoder.java 1.13 95/10/08 Chuck McManis
*
* Copyright (c) 1994 Sun Microsystems, Inc. All Rights Reserved.
*
* Permission to use, copy, modify, and distribute this software
* and its documentation for NON-COMMERCIAL purposes and without
* fee is hereby granted provided that this copyright notice
* appears in all copies. Please refer to the file "copyright.html"
* for further important copyright and licensing information.
*
* SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF
* THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
* TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
* PARTICULAR PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR
* ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR
* DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES.
*/
package sun.misc;
import java.io.InputStream;
import java.io.ByteArrayInputStream;
import java.io.OutputStream;
import java.io.ByteArrayOutputStream;
import java.io.PrintStream;
import java.io.IOException;
/**
* This class defines the encoding half of character encoders.
* A character encoder is an algorithim for transforming 8 bit binary
* data into text (generally 7 bit ASCII or 8 bit ISO-Latin-1 text)
* for transmition over text channels such as e-mail and network news.
*
* The character encoders have been structured around a central theme
* that, in general, the encoded text has the form:
*
* <pre>
* [Buffer Prefix]
* [Line Prefix][encoded data atoms][Line Suffix]
* [Buffer Suffix]
* </pre>
*
* In the CharacterEncoder and CharacterDecoder classes, one complete
* chunk of data is referred to as a <i>buffer</i>. Encoded buffers
* are all text, and decoded buffers (sometimes just referred to as
* buffers) are binary octets.
*
* To create a custom encoder, you must, at a minimum, overide three
* abstract methods in this class.
* <DL>
* <DD>bytesPerAtom which tells the encoder how many bytes to
* send to encodeAtom
* <DD>encodeAtom which encodes the bytes sent to it as text.
* <DD>bytesPerLine which tells the encoder the maximum number of
* bytes per line.
* </DL>
*
* Several useful encoders have already been written and are
* referenced in the See Also list below.
*
* @version 08 Oct 1995, 1.13
* @author Chuck McManis
* @see CharacterDecoder;
* @see UCEncoder
* @see UUEncoder
* @see BASE64Encoder
*/
public abstract class CharacterEncoder {
/** Stream that understands "printing" */
protected PrintStream pStream;
/** Return the number of bytes per atom of encoding */
abstract int bytesPerAtom();
/** Return the number of bytes that can be encoded per line */
abstract int bytesPerLine();
/**
* Encode the prefix for the entire buffer. By default is simply
* opens the PrintStream for use by the other functions.
*/
void encodeBufferPrefix(OutputStream aStream) throws IOException {
pStream = new PrintStream(aStream);
}
/**
* Encode the suffix for the entire buffer.
*/
void encodeBufferSuffix(OutputStream aStream) throws IOException { }
/**
* Encode the prefix that starts every output line.
*/
void encodeLinePrefix(OutputStream aStream, int aLength) throws IOException { }
/**
* Encode the suffix that ends every output line. By default
* this method just prints a <newline> into the output stream.
*/
void encodeLineSuffix(OutputStream aStream) throws IOException {
pStream.println();
}
/** Encode one "atom" of information into characters. */
abstract void encodeAtom(OutputStream aStream, byte someBytes[],
int anOffset, int aLength) throws IOException;
/**
* This method works around the bizarre semantics of BufferedInputStream's
* read method.
*/
protected int readFully(InputStream in, byte buffer[])
throws java.io.IOException {
for (int i = 0; i < buffer.length; i++) {
int q = in.read();
if (q == -1)
return i;
buffer[i] = (byte)q;
}
return buffer.length;
}
/**
* Encode bytes from the input stream, and write them as text characters
* to the output stream. This method will run until it exhausts the
* input stream.
*/
public void encodeBuffer(InputStream inStream, OutputStream outStream)
throws IOException {
int j;
int numBytes;
byte tmpbuffer[] = new byte[bytesPerLine()];
encodeBufferPrefix(outStream);
while (true) {
numBytes = readFully(inStream, tmpbuffer);
if (numBytes == -1) {
break;
}
encodeLinePrefix(outStream, numBytes);
for (j = 0; j < numBytes; j += bytesPerAtom()) {
if ((j + bytesPerAtom()) <= numBytes) {
encodeAtom(outStream, tmpbuffer, j, bytesPerAtom());
} else {
encodeAtom(outStream, tmpbuffer, j, (numBytes)- j);
}
}
encodeLineSuffix(outStream);
if (numBytes < bytesPerLine()) {
break;
}
}
encodeBufferSuffix(outStream);
}
/**
* Encode the buffer in <i>aBuffer</i> and write the encoded
* result to the OutputStream <i>aStream</i>.
*/
public void encodeBuffer(byte aBuffer[], OutputStream aStream) throws IOException {
ByteArrayInputStream inStream = new ByteArrayInputStream(aBuffer);
encodeBuffer(inStream, aStream);
}
/**
* A 'streamless' version of encode that simply takes a buffer of
* bytes and returns a string containing the encoded buffer.
*/
public String encodeBuffer(byte aBuffer[]) {
ByteArrayOutputStream outStream = new ByteArrayOutputStream();
ByteArrayInputStream inStream = new ByteArrayInputStream(aBuffer);
try {
encodeBuffer(inStream, outStream);
} catch (Exception IOException) {
// This should never happen.
throw new Error("ChracterEncoder::encodeBuffer internal error");
}
return (outStream.toString());
}
}