Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.apache.commons.codec_1_4.binary; import java.io.FilterOutputStream; import java.io.IOException; import java.io.OutputStream; /** * Provides Base64 encoding and decoding in a streaming fashion (unlimited size). When encoding the default lineLength * is 76 characters and the default lineEnding is CRLF, but these can be overridden by using the appropriate * constructor. * <p> * The default behaviour of the Base64OutputStream is to ENCODE, whereas the default behaviour of the Base64InputStream * is to DECODE. But this behaviour can be overridden by using a different constructor. * </p> * <p> * This class implements section <cite>6.8. Base64 Content-Transfer-Encoding</cite> from RFC 2045 <cite>Multipurpose * Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies</cite> by Freed and Borenstein. * </p> * <p> * Since this class operates directly on byte streams, and not character streams, it is hard-coded to only encode/decode * character encodings which are compatible with the lower 127 ASCII chart (ISO-8859-1, Windows-1252, UTF-8, etc). * </p> * * @author Apache Software Foundation * @version $Id: Base64OutputStream.java 799806 2009-08-01 04:33:17Z ggregory $ * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045</a> * @since 1.4 */ public class Base64OutputStream extends FilterOutputStream { private final boolean doEncode; private final Base64 base64; private final byte[] singleByte = new byte[1]; /** * Creates a Base64OutputStream such that all data written is Base64-encoded to the original provided OutputStream. * * @param out * OutputStream to wrap. */ public Base64OutputStream(OutputStream out) { this(out, true); } /** * Creates a Base64OutputStream such that all data written is either Base64-encoded or Base64-decoded to the * original provided OutputStream. * * @param out * OutputStream to wrap. * @param doEncode * true if we should encode all data written to us, false if we should decode. */ public Base64OutputStream(OutputStream out, boolean doEncode) { super(out); this.doEncode = doEncode; this.base64 = new Base64(); } /** * Creates a Base64OutputStream such that all data written is either Base64-encoded or Base64-decoded to the * original provided OutputStream. * * @param out * OutputStream to wrap. * @param doEncode * true if we should encode all data written to us, false if we should decode. * @param lineLength * If doEncode is true, each line of encoded data will contain lineLength characters (rounded down to * nearest multiple of 4). If lineLength <=0, the encoded data is not divided into lines. If doEncode is * false, lineLength is ignored. * @param lineSeparator * If doEncode is true, each line of encoded data will be terminated with this byte sequence (e.g. \r\n). * If lineLength <= 0, the lineSeparator is not used. If doEncode is false lineSeparator is ignored. */ public Base64OutputStream(OutputStream out, boolean doEncode, int lineLength, byte[] lineSeparator) { super(out); this.doEncode = doEncode; this.base64 = new Base64(lineLength, lineSeparator); } /** * Writes the specified <code>byte</code> to this output stream. * * @param i * source byte * @throws IOException * if an I/O error occurs. */ public void write(int i) throws IOException { singleByte[0] = (byte) i; write(singleByte, 0, 1); } /** * Writes <code>len</code> bytes from the specified <code>b</code> array starting at <code>offset</code> to this * output stream. * * @param b * source byte array * @param offset * where to start reading the bytes * @param len * maximum number of bytes to write * * @throws IOException * if an I/O error occurs. * @throws NullPointerException * if the byte array parameter is null * @throws IndexOutOfBoundsException * if offset, len or buffer size are invalid */ public void write(byte b[], int offset, int len) throws IOException { if (b == null) { throw new NullPointerException(); } else if (offset < 0 || len < 0) { throw new IndexOutOfBoundsException(); } else if (offset > b.length || offset + len > b.length) { throw new IndexOutOfBoundsException(); } else if (len > 0) { if (doEncode) { base64.encode(b, offset, len); } else { base64.decode(b, offset, len); } flush(false); } } /** * Flushes this output stream and forces any buffered output bytes to be written out to the stream. If propogate is * true, the wrapped stream will also be flushed. * * @param propogate * boolean flag to indicate whether the wrapped OutputStream should also be flushed. * @throws IOException * if an I/O error occurs. */ private void flush(boolean propogate) throws IOException { int avail = base64.avail(); if (avail > 0) { byte[] buf = new byte[avail]; int c = base64.readResults(buf, 0, avail); if (c > 0) { out.write(buf, 0, c); } } if (propogate) { out.flush(); } } /** * Flushes this output stream and forces any buffered output bytes to be written out to the stream. * * @throws IOException * if an I/O error occurs. */ public void flush() throws IOException { flush(true); } /** * Closes this output stream and releases any system resources associated with the stream. * * @throws IOException * if an I/O error occurs. */ public void close() throws IOException { // Notify encoder of EOF (-1). if (doEncode) { base64.encode(singleByte, 0, -1); } else { base64.decode(singleByte, 0, -1); } flush(); out.close(); } }