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app/src/main/java/com/android/volley/toolbox/PoolingByteArrayOutputStream.java

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+/*
+ * Copyright (C) 2012 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 com.android.volley.toolbox;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+
+/**
+ * A variation of {@link ByteArrayOutputStream} that uses a pool of byte[] buffers instead
+ * of always allocating them fresh, saving on heap churn.
+ */
+public class PoolingByteArrayOutputStream extends ByteArrayOutputStream {
+    /**
+     * If the {@link #PoolingByteArrayOutputStream(ByteArrayPool)} constructor is called, this is
+     * the default size to which the underlying byte array is initialized.
+     */
+    private static final int DEFAULT_SIZE = 256;
+
+    private final ByteArrayPool mPool;
+
+    /**
+     * Constructs a new PoolingByteArrayOutputStream with a default size. If more bytes are written
+     * to this instance, the underlying byte array will expand.
+     */
+    public PoolingByteArrayOutputStream(ByteArrayPool pool) {
+        this(pool, DEFAULT_SIZE);
+    }
+
+    /**
+     * Constructs a new {@code ByteArrayOutputStream} with a default size of {@code size} bytes. If
+     * more than {@code size} bytes are written to this instance, the underlying byte array will
+     * expand.
+     *
+     * @param size initial size for the underlying byte array. The value will be pinned to a default
+     *        minimum size.
+     */
+    public PoolingByteArrayOutputStream(ByteArrayPool pool, int size) {
+        mPool = pool;
+        buf = mPool.getBuf(Math.max(size, DEFAULT_SIZE));
+    }
+
+    @Override
+    public void close() throws IOException {
+        mPool.returnBuf(buf);
+        buf = null;
+        super.close();
+    }
+
+    @Override
+    public void finalize() {
+        mPool.returnBuf(buf);
+    }
+
+    /**
+     * Ensures there is enough space in the buffer for the given number of additional bytes.
+     */
+    private void expand(int i) {
+        /* Can the buffer handle @i more bytes, if not expand it */
+        if (count + i <= buf.length) {
+            return;
+        }
+        byte[] newbuf = mPool.getBuf((count + i) * 2);
+        System.arraycopy(buf, 0, newbuf, 0, count);
+        mPool.returnBuf(buf);
+        buf = newbuf;
+    }
+
+    @Override
+    public synchronized void write(byte[] buffer, int offset, int len) {
+        expand(len);
+        super.write(buffer, offset, len);
+    }
+
+    @Override
+    public synchronized void write(int oneByte) {
+        expand(1);
+        super.write(oneByte);
+    }
+}