/*
* 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 com.android.email.codec.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>
*
* @author Apache Software Foundation
* @version $Id $
* @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045</a>
* @since 1.0-dev
*/
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.
* 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.
*/
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 || offset + 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, flushing any remaining bytes that must be encoded. The
* underlying stream is flushed but not closed.
*/
public void close() throws IOException {
// Notify encoder of EOF (-1).
if (doEncode) {
base64.encode(singleByte, 0, -1);
} else {
base64.decode(singleByte, 0, -1);
}
flush();
}
}
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