net.logstash.logback.util.ReusableByteBuffer Maven / Gradle / Ivy
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/*
* Copyright 2013-2022 the original author or authors.
*
* 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
*
* 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 net.logstash.logback.util;
import java.io.IOException;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Objects;
/**
* A speedy alternative to {@link java.io.ByteArrayOutputStream}.
*
* Unlike {@link java.io.ByteArrayOutputStream}, this implementation is backed by an {@link ArrayList}
* of {@code byte[]} instead of 1 constantly resizing {@code byte[]} array. It does not copy buffers when
* it gets expanded.
*
*
The initial buffer is only created when the stream is first written.
* There is also no copying of the internal buffer if its contents is extracted with the
* {@link #writeTo(OutputStream)} method.
*
*
The {@link #reset()} method clears the content and resets the buffer to its initial state.
* Buffers are disposed except the initial buffer which is reused by subsequent usage.
*
*
This class is *not* thread-safe!
*
*
Note: This class is for internal use only and subject to backward incompatible change
* at any time.
*
* @author brenuart
*/
public class ReusableByteBuffer extends OutputStream {
/**
* The default size of the initial buffer
*/
static final int DEFAULT_INITIAL_CAPACITY = 1024;
/**
* Constant with an empty byte array
*/
private static final byte[] EMPTY_BYTES = new byte[0];
/**
* The buffers used to store the content bytes
*/
private final List buffers = new ArrayList<>();
/**
* The number of bytes already written in previous buffers (other than tail).
*/
private int alreadyBufferedSize = 0;
/**
* The write index in the tail buffer
*/
private int tailWriteIndex = 0;
/**
* Is the stream closed?
*/
private boolean closed = false;
/**
* Create a new {@link ReusableByteBuffer} with the default initial capacity of 1024 bytes.
*/
public ReusableByteBuffer() {
this(DEFAULT_INITIAL_CAPACITY);
}
/**
* Create a new {@link ReusableByteBuffer} with the specified initial capacity.
*
* @param initialCapacity the initial buffer size in bytes
*/
public ReusableByteBuffer(int initialCapacity) {
if (initialCapacity <= 0) {
throw new IllegalArgumentException("initialCapacity must be greater than 0");
}
this.buffers.add(new byte[initialCapacity]);
}
@Override
public void write(int datum) throws IOException {
if (this.closed) {
throw new IOException("Stream closed");
}
growIfNeeded();
getTailBuffer()[this.tailWriteIndex++] = (byte) datum;
}
@Override
public void write(byte[] data, int offset, int length) throws IOException {
Objects.requireNonNull(data, "data must not be null");
if (offset < 0 || offset + length > data.length || length < 0) {
throw new IndexOutOfBoundsException();
}
if (this.closed) {
throw new IOException("Stream closed");
}
while (length > 0) {
byte[] buffer = getTailBuffer();
int freeSpace = buffer.length - this.tailWriteIndex;
if (freeSpace > 0) {
int toCopy = Math.min(freeSpace, length);
System.arraycopy(data, offset, buffer, this.tailWriteIndex, toCopy);
offset += toCopy;
this.tailWriteIndex += toCopy;
length -= toCopy;
}
if (length > 0) {
growIfNeeded();
}
}
}
@Override
public void close() {
this.closed = true;
}
/**
* Return the current size of the buffer.
*
* @return the current size of the buffer.
*/
public int size() {
return this.alreadyBufferedSize + this.tailWriteIndex;
}
/**
* Reset the contents of this {@link ReusableByteBuffer}.
* All currently accumulated output in the output stream is discarded.
* The output stream can be used again.
*/
public void reset() {
// Clear allocated buffers but keep the first one
if (buffers.size() > 1) {
byte[] initialBuffer = this.buffers.get(0);
this.buffers.clear();
this.buffers.add(initialBuffer);
}
this.closed = false;
this.tailWriteIndex = 0;
this.alreadyBufferedSize = 0;
}
/**
* Write the buffers content to the given OutputStream.
*
* @param out the OutputStream to write to
* @throws IOException in case of problems writing into the output stream
*/
public void writeTo(OutputStream out) throws IOException {
Iterator it = this.buffers.iterator();
while (it.hasNext()) {
byte[] buffer = it.next();
if (it.hasNext()) {
out.write(buffer, 0, buffer.length);
} else {
out.write(buffer, 0, this.tailWriteIndex);
}
}
}
/**
* Creates a newly allocated byte array.
*
* Its size is the current size of this output stream and the valid contents
* of the buffer have been copied into it.
*
* @return the current contents of this output stream, as a byte array.
* @see #size()
*/
public byte[] toByteArray() {
int totalSize = size();
if (totalSize == 0) {
return EMPTY_BYTES;
}
byte[] result = new byte[totalSize];
int offset = 0;
Iterator it = this.buffers.iterator();
while (it.hasNext()) {
byte[] buffer = it.next();
if (it.hasNext()) {
System.arraycopy(buffer, 0, result, offset, buffer.length);
offset += buffer.length;
} else {
System.arraycopy(buffer, 0, result, offset, this.tailWriteIndex);
}
}
return result;
}
/**
* Allocate a new chunk if needed
*/
private void growIfNeeded() {
if (getTailBuffer().length == this.tailWriteIndex) {
this.alreadyBufferedSize += this.tailWriteIndex;
this.buffers.add(new byte[this.tailWriteIndex * 2]); // block size doubles each time
this.tailWriteIndex = 0;
}
}
/**
* Convenience method to get the tail buffer (the one to write into)
*
* @return the tail buffer
*/
private byte[] getTailBuffer() {
return this.buffers.get(this.buffers.size() - 1);
}
}