355 lines
12 KiB
Java
355 lines
12 KiB
Java
/*
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* Copyright (c) 1995, 2005, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package sun.misc;
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import java.io.InputStream;
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import java.io.ByteArrayInputStream;
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import java.io.OutputStream;
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import java.io.ByteArrayOutputStream;
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import java.io.PrintStream;
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import java.io.IOException;
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import java.nio.ByteBuffer;
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/**
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* This class defines the encoding half of character encoders.
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* A character encoder is an algorithim for transforming 8 bit binary
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* data into text (generally 7 bit ASCII or 8 bit ISO-Latin-1 text)
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* for transmition over text channels such as e-mail and network news.
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*
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* The character encoders have been structured around a central theme
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* that, in general, the encoded text has the form:
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*
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* <pre>
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* [Buffer Prefix]
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* [Line Prefix][encoded data atoms][Line Suffix]
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* [Buffer Suffix]
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* </pre>
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*
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* In the CharacterEncoder and CharacterDecoder classes, one complete
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* chunk of data is referred to as a <i>buffer</i>. Encoded buffers
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* are all text, and decoded buffers (sometimes just referred to as
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* buffers) are binary octets.
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*
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* To create a custom encoder, you must, at a minimum, overide three
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* abstract methods in this class.
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* <DL>
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* <DD>bytesPerAtom which tells the encoder how many bytes to
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* send to encodeAtom
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* <DD>encodeAtom which encodes the bytes sent to it as text.
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* <DD>bytesPerLine which tells the encoder the maximum number of
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* bytes per line.
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* </DL>
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*
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* Several useful encoders have already been written and are
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* referenced in the See Also list below.
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*
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* @author Chuck McManis
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* @see CharacterDecoder;
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* @see UCEncoder
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* @see UUEncoder
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* @see BASE64Encoder
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*/
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public abstract class CharacterEncoder {
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/** Stream that understands "printing" */
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protected PrintStream pStream;
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/** Return the number of bytes per atom of encoding */
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abstract protected int bytesPerAtom();
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/** Return the number of bytes that can be encoded per line */
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abstract protected int bytesPerLine();
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/**
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* Encode the prefix for the entire buffer. By default is simply
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* opens the PrintStream for use by the other functions.
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*/
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protected void encodeBufferPrefix(OutputStream aStream) throws IOException {
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pStream = new PrintStream(aStream);
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}
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/**
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* Encode the suffix for the entire buffer.
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*/
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protected void encodeBufferSuffix(OutputStream aStream) throws IOException {
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}
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/**
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* Encode the prefix that starts every output line.
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*/
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protected void encodeLinePrefix(OutputStream aStream, int aLength)
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throws IOException {
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}
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/**
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* Encode the suffix that ends every output line. By default
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* this method just prints a <newline> into the output stream.
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*/
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protected void encodeLineSuffix(OutputStream aStream) throws IOException {
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pStream.println();
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}
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/** Encode one "atom" of information into characters. */
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abstract protected void encodeAtom(OutputStream aStream, byte someBytes[],
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int anOffset, int aLength) throws IOException;
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/**
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* This method works around the bizarre semantics of BufferedInputStream's
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* read method.
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*/
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protected int readFully(InputStream in, byte buffer[])
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throws java.io.IOException {
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for (int i = 0; i < buffer.length; i++) {
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int q = in.read();
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if (q == -1)
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return i;
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buffer[i] = (byte)q;
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}
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return buffer.length;
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}
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/**
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* Encode bytes from the input stream, and write them as text characters
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* to the output stream. This method will run until it exhausts the
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* input stream, but does not print the line suffix for a final
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* line that is shorter than bytesPerLine().
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*/
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public void encode(InputStream inStream, OutputStream outStream)
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throws IOException {
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int j;
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int numBytes;
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byte tmpbuffer[] = new byte[bytesPerLine()];
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encodeBufferPrefix(outStream);
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while (true) {
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numBytes = readFully(inStream, tmpbuffer);
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if (numBytes == 0) {
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break;
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}
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encodeLinePrefix(outStream, numBytes);
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for (j = 0; j < numBytes; j += bytesPerAtom()) {
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if ((j + bytesPerAtom()) <= numBytes) {
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encodeAtom(outStream, tmpbuffer, j, bytesPerAtom());
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} else {
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encodeAtom(outStream, tmpbuffer, j, (numBytes)- j);
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}
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}
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if (numBytes < bytesPerLine()) {
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break;
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} else {
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encodeLineSuffix(outStream);
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}
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}
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encodeBufferSuffix(outStream);
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}
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/**
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* Encode the buffer in <i>aBuffer</i> and write the encoded
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* result to the OutputStream <i>aStream</i>.
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*/
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public void encode(byte aBuffer[], OutputStream aStream)
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throws IOException {
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ByteArrayInputStream inStream = new ByteArrayInputStream(aBuffer);
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encode(inStream, aStream);
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}
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/**
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* A 'streamless' version of encode that simply takes a buffer of
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* bytes and returns a string containing the encoded buffer.
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*/
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public String encode(byte aBuffer[]) {
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ByteArrayOutputStream outStream = new ByteArrayOutputStream();
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ByteArrayInputStream inStream = new ByteArrayInputStream(aBuffer);
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String retVal = null;
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try {
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encode(inStream, outStream);
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// explicit ascii->unicode conversion
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retVal = outStream.toString("8859_1");
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} catch (Exception IOException) {
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// This should never happen.
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throw new Error("CharacterEncoder.encode internal error");
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}
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return (retVal);
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}
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/**
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* Return a byte array from the remaining bytes in this ByteBuffer.
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* <P>
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* The ByteBuffer's position will be advanced to ByteBuffer's limit.
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* <P>
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* To avoid an extra copy, the implementation will attempt to return the
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* byte array backing the ByteBuffer. If this is not possible, a
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* new byte array will be created.
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*/
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private byte [] getBytes(ByteBuffer bb) {
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/*
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* This should never return a BufferOverflowException, as we're
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* careful to allocate just the right amount.
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*/
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byte [] buf = null;
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/*
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* If it has a usable backing byte buffer, use it. Use only
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* if the array exactly represents the current ByteBuffer.
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*/
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if (bb.hasArray()) {
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byte [] tmp = bb.array();
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if ((tmp.length == bb.capacity()) &&
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(tmp.length == bb.remaining())) {
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buf = tmp;
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bb.position(bb.limit());
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}
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}
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if (buf == null) {
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/*
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* This class doesn't have a concept of encode(buf, len, off),
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* so if we have a partial buffer, we must reallocate
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* space.
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*/
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buf = new byte[bb.remaining()];
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/*
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* position() automatically updated
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*/
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bb.get(buf);
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}
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return buf;
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}
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/**
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* Encode the <i>aBuffer</i> ByteBuffer and write the encoded
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* result to the OutputStream <i>aStream</i>.
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* <P>
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* The ByteBuffer's position will be advanced to ByteBuffer's limit.
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*/
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public void encode(ByteBuffer aBuffer, OutputStream aStream)
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throws IOException {
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byte [] buf = getBytes(aBuffer);
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encode(buf, aStream);
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}
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/**
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* A 'streamless' version of encode that simply takes a ByteBuffer
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* and returns a string containing the encoded buffer.
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* <P>
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* The ByteBuffer's position will be advanced to ByteBuffer's limit.
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*/
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public String encode(ByteBuffer aBuffer) {
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byte [] buf = getBytes(aBuffer);
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return encode(buf);
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}
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/**
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* Encode bytes from the input stream, and write them as text characters
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* to the output stream. This method will run until it exhausts the
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* input stream. It differs from encode in that it will add the
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* line at the end of a final line that is shorter than bytesPerLine().
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*/
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public void encodeBuffer(InputStream inStream, OutputStream outStream)
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throws IOException {
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int j;
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int numBytes;
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byte tmpbuffer[] = new byte[bytesPerLine()];
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encodeBufferPrefix(outStream);
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while (true) {
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numBytes = readFully(inStream, tmpbuffer);
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if (numBytes == 0) {
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break;
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}
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encodeLinePrefix(outStream, numBytes);
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for (j = 0; j < numBytes; j += bytesPerAtom()) {
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if ((j + bytesPerAtom()) <= numBytes) {
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encodeAtom(outStream, tmpbuffer, j, bytesPerAtom());
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} else {
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encodeAtom(outStream, tmpbuffer, j, (numBytes)- j);
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}
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}
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encodeLineSuffix(outStream);
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if (numBytes < bytesPerLine()) {
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break;
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}
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}
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encodeBufferSuffix(outStream);
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}
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/**
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* Encode the buffer in <i>aBuffer</i> and write the encoded
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* result to the OutputStream <i>aStream</i>.
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*/
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public void encodeBuffer(byte aBuffer[], OutputStream aStream)
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throws IOException {
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ByteArrayInputStream inStream = new ByteArrayInputStream(aBuffer);
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encodeBuffer(inStream, aStream);
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}
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/**
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* A 'streamless' version of encode that simply takes a buffer of
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* bytes and returns a string containing the encoded buffer.
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*/
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public String encodeBuffer(byte aBuffer[]) {
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ByteArrayOutputStream outStream = new ByteArrayOutputStream();
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ByteArrayInputStream inStream = new ByteArrayInputStream(aBuffer);
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try {
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encodeBuffer(inStream, outStream);
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} catch (Exception IOException) {
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// This should never happen.
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throw new Error("CharacterEncoder.encodeBuffer internal error");
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}
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return (outStream.toString());
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}
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/**
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* Encode the <i>aBuffer</i> ByteBuffer and write the encoded
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* result to the OutputStream <i>aStream</i>.
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* <P>
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* The ByteBuffer's position will be advanced to ByteBuffer's limit.
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*/
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public void encodeBuffer(ByteBuffer aBuffer, OutputStream aStream)
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throws IOException {
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byte [] buf = getBytes(aBuffer);
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encodeBuffer(buf, aStream);
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}
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/**
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* A 'streamless' version of encode that simply takes a ByteBuffer
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* and returns a string containing the encoded buffer.
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* <P>
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* The ByteBuffer's position will be advanced to ByteBuffer's limit.
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*/
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public String encodeBuffer(ByteBuffer aBuffer) {
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byte [] buf = getBytes(aBuffer);
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return encodeBuffer(buf);
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}
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}
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