Fixes xerial#88 by introducing thread-safe BufferAllocator

Author: xerial

project/build.properties

@@ -1,2 +1,2 @@
-sbt.version=0.13.5
+sbt.version=0.13.6
 

src/main/java/org/xerial/snappy/BufferRecycler.java

@@ -24,6 +24,10 @@
 //--------------------------------------
 package org.xerial.snappy;
 
+import org.xerial.snappy.buffer.BufferAllocatorFactory;
+import org.xerial.snappy.buffer.BufferAllocator;
+import org.xerial.snappy.buffer.CachedBufferAllocator;
+
 import java.io.IOException;
 import java.io.OutputStream;
 
@@ -56,9 +60,11 @@ public class SnappyOutputStream extends OutputStream {
     static final int DEFAULT_BLOCK_SIZE = 32 * 1024; // Use 32kb for the default block size
 
     protected final OutputStream out;
-
-    private final BufferRecycler recycler;
     private final int blockSize;
+
+    private final BufferAllocator inputBufferAllocator;
+    private final BufferAllocator outputBufferAllocator;
+
     protected final byte[] inputBuffer;
     protected final byte[] outputBuffer;
     private int inputCursor = 0;
@@ -74,14 +80,25 @@ public SnappyOutputStream(OutputStream out) {
      * @throws IOException
      */
     public SnappyOutputStream(OutputStream out, int blockSize) {
+        this(out, blockSize, CachedBufferAllocator.factory);
+    }
+
+    public SnappyOutputStream(OutputStream out, int blockSize, BufferAllocatorFactory bufferAllocatorFactory) {
         this.out = out;
-        this.recycler = BufferRecycler.instance();
         this.blockSize = Math.max(MIN_BLOCK_SIZE, blockSize);
-        inputBuffer = recycler.allocInputBuffer(this.blockSize);
-        outputBuffer = recycler.allocOutputBuffer(SnappyCodec.HEADER_SIZE + 4 + Snappy.maxCompressedLength(this.blockSize));
+        int inputSize = blockSize;
+        int outputSize = SnappyCodec.HEADER_SIZE + 4 + Snappy.maxCompressedLength(blockSize);
+
+        this.inputBufferAllocator = bufferAllocatorFactory.getBufferAllocator(inputSize);
+        this.outputBufferAllocator = bufferAllocatorFactory.getBufferAllocator(outputSize);
+
+        inputBuffer = inputBufferAllocator.allocate(inputSize);
+        outputBuffer = inputBufferAllocator.allocate(outputSize);
+
         outputCursor = SnappyCodec.currentHeader.writeHeader(outputBuffer, 0);
     }
 
+
     /* (non-Javadoc)
      * @see java.io.OutputStream#write(byte[], int, int)
      */
@@ -265,9 +282,9 @@ public void flush() throws IOException {
 
     static void writeInt(byte[] dst, int offset, int v) {
         dst[offset] = (byte) ((v >> 24) & 0xFF);
-        dst[offset+1] = (byte) ((v >> 16) & 0xFF);
-        dst[offset+2] = (byte) ((v >> 8) & 0xFF);
-        dst[offset+3] = (byte) ((v >> 0) & 0xFF);
+        dst[offset + 1] = (byte) ((v >> 16) & 0xFF);
+        dst[offset + 2] = (byte) ((v >> 8) & 0xFF);
+        dst[offset + 3] = (byte) ((v >> 0) & 0xFF);
     }
 
     static int readInt(byte[] buffer, int pos) {
@@ -312,10 +329,9 @@ public void close() throws IOException {
         try {
             flush();
             out.close();
-        }
-        finally {
-            recycler.releaseInputBuffer(inputBuffer);
-            recycler.releaseOutputBuffer(outputBuffer);
+        } finally {
+            inputBufferAllocator.release(inputBuffer);
+            outputBufferAllocator.release(outputBuffer);
         }
     }
 

src/main/java/org/xerial/snappy/SnappyOutputStream.java

@@ -0,0 +1,11 @@
+package org.xerial.snappy.buffer;
+
+/**
+ * BufferAllocator interface. The implementation of this interface must be thread-safe
+ */
+public interface BufferAllocator {
+
+    public byte[] allocate(int size);
+    public void release(byte[] buffer);
+
+}

src/main/java/org/xerial/snappy/buffer/BufferAllocator.java

@@ -0,0 +1,10 @@
+package org.xerial.snappy.buffer;
+
+/**
+ *
+ */
+public interface BufferAllocatorFactory {
+
+    BufferAllocator getBufferAllocator(int minSize);
+}
+

src/main/java/org/xerial/snappy/buffer/BufferAllocatorFactory.java

@@ -0,0 +1,55 @@
+package org.xerial.snappy.buffer;
+
+import java.lang.ref.SoftReference;
+import java.util.*;
+
+/**
+ * Cached buffer
+ */
+public class CachedBufferAllocator implements BufferAllocator {
+
+    public static BufferAllocatorFactory factory = new BufferAllocatorFactory() {
+        @Override
+        public BufferAllocator getBufferAllocator(int bufferSize) {
+            return CachedBufferAllocator.getAllocator(bufferSize);
+        }
+    };
+
+    /**
+     * Use SoftReference so that having this queueTable does not prevent the GC of CachedBufferAllocator instances
+     */
+    public static Map<Integer, SoftReference<CachedBufferAllocator>> queueTable = new HashMap<Integer, SoftReference<CachedBufferAllocator>>();
+
+    private final int bufferSize;
+    private final Deque<byte[]> bufferQueue;
+
+    public CachedBufferAllocator(int bufferSize) {
+        this.bufferSize = bufferSize;
+        this.bufferQueue = new ArrayDeque<byte[]>();
+    }
+
+    public static synchronized CachedBufferAllocator getAllocator(int bufferSize) {
+        if(!queueTable.containsKey(bufferSize)) {
+            queueTable.put(bufferSize, new SoftReference<CachedBufferAllocator>(new CachedBufferAllocator(bufferSize)));
+        }
+        return queueTable.get(bufferSize).get();
+    }
+
+    @Override
+    public byte[] allocate(int size) {
+        synchronized(this) {
+            if(bufferQueue.isEmpty()) {
+                return new byte[size];
+            }
+            else {
+                return bufferQueue.pollFirst();
+            }
+        }
+    }
+    @Override
+    public void release(byte[] buffer) {
+        synchronized(this) {
+            bufferQueue.addLast(buffer);
+        }
+    }
+}

src/main/java/org/xerial/snappy/buffer/CachedBufferAllocator.java

@@ -0,0 +1,26 @@
+package org.xerial.snappy.buffer;
+
+/**
+ * Simple buffer allocator, which does not reuse the allocated buffer
+ */
+public class DefaultBufferAllocator implements BufferAllocator {
+
+    public static BufferAllocatorFactory factory = new BufferAllocatorFactory() {
+        public BufferAllocator singleton = new DefaultBufferAllocator();
+        @Override
+        public BufferAllocator getBufferAllocator(int bufferSize) {
+            return singleton;
+        }
+    };
+
+    @Override
+    public byte[] allocate(int size) {
+        return new byte[size];
+    }
+
+    @Override
+    public void release(byte[] buffer) {
+        // do nothing
+    }
+
+}

src/main/java/org/xerial/snappy/buffer/DefaultBufferAllocator.java

@@ -1 +1 @@
-version in ThisBuild := "1.1.1.3"
+version in ThisBuild := "1.1.1.4-SNAPSHOT"