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/*
* Copyright (C) 2006 The Android Open Source Project
*
* 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 android.webkit;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.SoftReference;
import java.util.LinkedList;
import java.util.ListIterator;
/** Utility class optimized for accumulating bytes, and then spitting
them back out. It does not optimize for returning the result in a
single array, though this is supported in the API. It is fastest
if the retrieval can be done via iterating through chunks.
*/
class ByteArrayBuilder {
private static final int DEFAULT_CAPACITY = 8192;
// Global pool of chunks to be used by other ByteArrayBuilders.
private static final LinkedList<SoftReference<Chunk>> sPool =
new LinkedList<SoftReference<Chunk>>();
// Reference queue for processing gc'd entries.
private static final ReferenceQueue<Chunk> sQueue =
new ReferenceQueue<Chunk>();
private LinkedList<Chunk> mChunks;
public ByteArrayBuilder() {
mChunks = new LinkedList<Chunk>();
}
public synchronized void append(byte[] array, int offset, int length) {
while (length > 0) {
Chunk c = null;
if (mChunks.isEmpty()) {
c = obtainChunk(length);
mChunks.addLast(c);
} else {
c = mChunks.getLast();
if (c.mLength == c.mArray.length) {
c = obtainChunk(length);
mChunks.addLast(c);
}
}
int amount = Math.min(length, c.mArray.length - c.mLength);
System.arraycopy(array, offset, c.mArray, c.mLength, amount);
c.mLength += amount;
length -= amount;
offset += amount;
}
}
/**
* The fastest way to retrieve the data is to iterate through the
* chunks. This returns the first chunk. Note: this pulls the
* chunk out of the queue. The caller must call Chunk.release() to
* dispose of it.
*/
public synchronized Chunk getFirstChunk() {
if (mChunks.isEmpty()) return null;
return mChunks.removeFirst();
}
public synchronized boolean isEmpty() {
return mChunks.isEmpty();
}
public synchronized int getByteSize() {
int total = 0;
ListIterator<Chunk> it = mChunks.listIterator(0);
while (it.hasNext()) {
Chunk c = it.next();
total += c.mLength;
}
return total;
}
public synchronized void clear() {
Chunk c = getFirstChunk();
while (c != null) {
c.release();
c = getFirstChunk();
}
}
// Must be called with lock held on sPool.
private void processPoolLocked() {
while (true) {
SoftReference<Chunk> entry = (SoftReference<Chunk>) sQueue.poll();
if (entry == null) {
break;
}
sPool.remove(entry);
}
}
private Chunk obtainChunk(int length) {
// Correct a small length.
if (length < DEFAULT_CAPACITY) {
length = DEFAULT_CAPACITY;
}
synchronized (sPool) {
// Process any queued references and remove them from the pool.
processPoolLocked();
if (!sPool.isEmpty()) {
Chunk c = sPool.removeFirst().get();
// The first item may have been queued after processPoolLocked
// so check for null.
if (c != null) {
return c;
}
}
return new Chunk(length);
}
}
public static class Chunk {
public byte[] mArray;
public int mLength;
public Chunk(int length) {
mArray = new byte[length];
mLength = 0;
}
/**
* Release the chunk and make it available for reuse.
*/
public void release() {
mLength = 0;
synchronized (sPool) {
// Add the chunk back to the pool as a SoftReference so it can
// be gc'd if needed.
sPool.offer(new SoftReference<Chunk>(this, sQueue));
sPool.notifyAll();
}
}
}
}
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