org.omnifaces.io.ResettableBufferedOutputStream Maven / Gradle / Ivy
/*
* Copyright OmniFaces
*
* Licensed 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
*
* https://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.omnifaces.io;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
/**
* This resettable buffered output stream will buffer everything until the given threshold buffer size, regardless of
* flush calls. Only when the specified threshold buffer size is exceeded, or when {@link #close()} is called, then the
* buffer will be actually flushed.
*
* There is a {@link #reset()} method which enables the developer to reset the buffer, as long as it's not flushed yet,
* which can be determined by {@link #isResettable()}.
*
* @author Bauke Scholtz
* @see ResettableBufferedWriter
*/
public class ResettableBufferedOutputStream extends OutputStream implements ResettableBuffer {
// Constants --------------------------------------------------------------------------------------------------
private static final String ERROR_CLOSED = "Stream is already closed.";
// Variables ------------------------------------------------------------------------------------------------------
private OutputStream output;
private ByteArrayOutputStream buffer;
private int thresholdBufferSize;
private int writtenBytes;
private boolean closed;
// Constructors ---------------------------------------------------------------------------------------------------
/**
* Construct a new resettable buffered output stream which forcibly buffers everything until the given threshold
* buffer size, regardless of flush calls and calls. You need to override {@link #createOutputStream(boolean)} when
* using this constructor.
* @param thresholdBufferSize The threshold buffer size.
*/
public ResettableBufferedOutputStream(int thresholdBufferSize) {
this(null, thresholdBufferSize);
}
/**
* Construct a new resettable buffered output stream which wraps the given output stream and forcibly buffers
* everything until the given threshold buffer size, regardless of flush calls. You do not need to override
* {@link #createOutputStream(boolean)} when using this constructor.
* @param output The wrapped output stream .
* @param thresholdBufferSize The threshold buffer size.
*/
public ResettableBufferedOutputStream(OutputStream output, int thresholdBufferSize) {
this.output = output;
this.thresholdBufferSize = thresholdBufferSize;
buffer = new ByteArrayOutputStream(thresholdBufferSize);
}
// Actions --------------------------------------------------------------------------------------------------------
@Override
public void write(int b) throws IOException {
write(new byte[] { (byte) b }, 0, 1);
}
@Override
public void write(byte[] bytes) throws IOException {
write(bytes, 0, bytes.length);
}
@Override
public void write(byte[] bytes, int offset, int length) throws IOException {
checkClosed();
if (isResettable()) {
writtenBytes += (length - offset);
if (writtenBytes > thresholdBufferSize) {
flushBuffer(true);
output.write(bytes, offset, length);
}
else {
buffer.write(bytes, offset, length);
}
}
else {
output.write(bytes, offset, length);
}
}
private void flushBuffer(boolean thresholdBufferSizeExceeded) throws IOException {
if (output == null) {
if (thresholdBufferSizeExceeded) {
writtenBytes = -1;
}
output = createOutputStream(thresholdBufferSizeExceeded);
}
output.write(buffer.toByteArray());
buffer = null;
}
/**
* Returns the custom implementation of the {@link OutputStream}. This will only be called when the specified
* threshold buffer size is exceeded, or when {@link #close()} is called.
* @param thresholdBufferSizeExceeded Whether the threshold buffer size has exceeded.
* @return The custom implementation of the {@link OutputStream}.
* @throws IOException When an I/O error occurs.
*/
protected OutputStream createOutputStream(boolean thresholdBufferSizeExceeded) throws IOException {
throw new UnsupportedOperationException(
"You need to either override this method, or use the 2-arg constructor taking OutputStream instead.");
}
/**
* Returns the amount of so far written bytes in the threshold buffer. This will be 0 when the threshold buffer is
* empty and this will be -1 when the threshold has exceeded.
* @return The amount of so far written bytes in the threshold buffer.
*/
protected int getWrittenBytes() {
return writtenBytes;
}
@Override
public void reset() {
if (isResettable()) {
buffer = new ByteArrayOutputStream(thresholdBufferSize);
writtenBytes = 0;
}
}
@Override
public void flush() throws IOException {
checkClosed();
if (!isResettable()) {
output.flush();
}
}
@Override
public void close() throws IOException {
if (closed) {
return;
}
if (isResettable()) {
flushBuffer(false);
}
output.close();
closed = true;
}
@Override
public boolean isResettable() {
return buffer != null;
}
/**
* Check if the current stream is closed and if so, then throw IO exception.
* @throws IOException When the current stream is closed.
*/
private void checkClosed() throws IOException {
if (closed) {
throw new IOException(ERROR_CLOSED);
}
}
}