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Java example source code file (CharacterEncoder.java)
The CharacterEncoder.java Java example source code/* * Copyright (c) 1995, 2005, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ 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; import java.nio.ByteBuffer; /** * 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. 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. * * @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 protected int bytesPerAtom(); /** Return the number of bytes that can be encoded per line */ abstract protected int bytesPerLine(); /** * Encode the prefix for the entire buffer. By default is simply * opens the PrintStream for use by the other functions. */ protected void encodeBufferPrefix(OutputStream aStream) throws IOException { pStream = new PrintStream(aStream); } /** * Encode the suffix for the entire buffer. */ protected void encodeBufferSuffix(OutputStream aStream) throws IOException { } /** * Encode the prefix that starts every output line. */ protected 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. */ protected void encodeLineSuffix(OutputStream aStream) throws IOException { pStream.println(); } /** Encode one "atom" of information into characters. */ abstract protected 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, but does not print the line suffix for a final * line that is shorter than bytesPerLine(). */ public void encode(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 == 0) { 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); } } if (numBytes < bytesPerLine()) { break; } else { encodeLineSuffix(outStream); } } encodeBufferSuffix(outStream); } /** * Encode the buffer in <i>aBuffer and write the encoded * result to the OutputStream <i>aStream. */ public void encode(byte aBuffer[], OutputStream aStream) throws IOException { ByteArrayInputStream inStream = new ByteArrayInputStream(aBuffer); encode(inStream, aStream); } /** * A 'streamless' version of encode that simply takes a buffer of * bytes and returns a string containing the encoded buffer. */ public String encode(byte aBuffer[]) { ByteArrayOutputStream outStream = new ByteArrayOutputStream(); ByteArrayInputStream inStream = new ByteArrayInputStream(aBuffer); String retVal = null; try { encode(inStream, outStream); // explicit ascii->unicode conversion retVal = outStream.toString("8859_1"); } catch (Exception IOException) { // This should never happen. throw new Error("CharacterEncoder.encode internal error"); } return (retVal); } /** * Return a byte array from the remaining bytes in this ByteBuffer. * <P> * The ByteBuffer's position will be advanced to ByteBuffer's limit. * <P> * To avoid an extra copy, the implementation will attempt to return the * byte array backing the ByteBuffer. If this is not possible, a * new byte array will be created. */ private byte [] getBytes(ByteBuffer bb) { /* * This should never return a BufferOverflowException, as we're * careful to allocate just the right amount. */ byte [] buf = null; /* * If it has a usable backing byte buffer, use it. Use only * if the array exactly represents the current ByteBuffer. */ if (bb.hasArray()) { byte [] tmp = bb.array(); if ((tmp.length == bb.capacity()) && (tmp.length == bb.remaining())) { buf = tmp; bb.position(bb.limit()); } } if (buf == null) { /* * This class doesn't have a concept of encode(buf, len, off), * so if we have a partial buffer, we must reallocate * space. */ buf = new byte[bb.remaining()]; /* * position() automatically updated */ bb.get(buf); } return buf; } /** * Encode the <i>aBuffer ByteBuffer and write the encoded * result to the OutputStream <i>aStream. * <P> * The ByteBuffer's position will be advanced to ByteBuffer's limit. */ public void encode(ByteBuffer aBuffer, OutputStream aStream) throws IOException { byte [] buf = getBytes(aBuffer); encode(buf, aStream); } /** * A 'streamless' version of encode that simply takes a ByteBuffer * and returns a string containing the encoded buffer. * <P> * The ByteBuffer's position will be advanced to ByteBuffer's limit. */ public String encode(ByteBuffer aBuffer) { byte [] buf = getBytes(aBuffer); return encode(buf); } /** * 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. It differs from encode in that it will add the * line at the end of a final line that is shorter than bytesPerLine(). */ 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 == 0) { 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 and write the encoded * result to the OutputStream <i>aStream. */ 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("CharacterEncoder.encodeBuffer internal error"); } return (outStream.toString()); } /** * Encode the <i>aBuffer ByteBuffer and write the encoded * result to the OutputStream <i>aStream. * <P> * The ByteBuffer's position will be advanced to ByteBuffer's limit. */ public void encodeBuffer(ByteBuffer aBuffer, OutputStream aStream) throws IOException { byte [] buf = getBytes(aBuffer); encodeBuffer(buf, aStream); } /** * A 'streamless' version of encode that simply takes a ByteBuffer * and returns a string containing the encoded buffer. * <P> * The ByteBuffer's position will be advanced to ByteBuffer's limit. */ public String encodeBuffer(ByteBuffer aBuffer) { byte [] buf = getBytes(aBuffer); return encodeBuffer(buf); } } Other Java examples (source code examples)Here is a short list of links related to this Java CharacterEncoder.java source code file: |
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