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java/org/apache/tomcat/util/net/WriteBuffer.java

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+/*
+ *  Licensed to the Apache Software Foundation (ASF) under one or more
+ *  contributor license agreements.  See the NOTICE file distributed with
+ *  this work for additional information regarding copyright ownership.
+ *  The ASF licenses this file to You 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 org.apache.tomcat.util.net;
+
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+import java.util.concurrent.LinkedBlockingDeque;
+
+import org.apache.tomcat.util.buf.ByteBufferHolder;
+
+/**
+ * Provides an expandable set of buffers for writes. Non-blocking writes can be
+ * of any size and may not be able to be written immediately or wholly contained
+ * in the buffer used to perform the writes to the next layer. This class
+ * provides a buffering capability to allow such writes to return immediately
+ * and also allows for the user provided buffers to be re-used / recycled as
+ * required.
+ */
+public class WriteBuffer {
+
+    private final int bufferSize;
+
+    private final LinkedBlockingDeque<ByteBufferHolder> buffers = new LinkedBlockingDeque<>();
+
+    public WriteBuffer(int bufferSize) {
+        this.bufferSize = bufferSize;
+    }
+
+
+    void add(byte[] buf, int offset, int length) {
+        ByteBufferHolder holder = getByteBufferHolder(length);
+        holder.getBuf().put(buf, offset, length);
+    }
+
+
+    public void add(ByteBuffer from) {
+        ByteBufferHolder holder = getByteBufferHolder(from.remaining());
+        holder.getBuf().put(from);
+    }
+
+
+    private ByteBufferHolder getByteBufferHolder(int capacity) {
+        ByteBufferHolder holder = buffers.peekLast();
+        if (holder == null || holder.isFlipped() || holder.getBuf().remaining() < capacity) {
+            ByteBuffer buffer = ByteBuffer.allocate(Math.max(bufferSize, capacity));
+            holder = new ByteBufferHolder(buffer, false);
+            buffers.add(holder);
+        }
+        return holder;
+    }
+
+
+    public boolean isEmpty() {
+        return buffers.isEmpty();
+    }
+
+
+    /**
+     * Create an array of ByteBuffers from the current WriteBuffer, prefixing
+     * that array with the provided ByteBuffers.
+     *
+     * @param prefixes The additional ByteBuffers to add to the start of the
+     *                 array
+     *
+     * @return an array of ByteBuffers from the current WriteBuffer prefixed by
+     *         the provided ByteBuffers
+     */
+    ByteBuffer[] toArray(ByteBuffer... prefixes) {
+        List<ByteBuffer> result = new ArrayList<>();
+        for (ByteBuffer prefix : prefixes) {
+            if (prefix.hasRemaining()) {
+                result.add(prefix);
+            }
+        }
+        for (ByteBufferHolder buffer : buffers) {
+            buffer.flip();
+            result.add(buffer.getBuf());
+        }
+        buffers.clear();
+        return result.toArray(new ByteBuffer[result.size()]);
+    }
+
+
+    boolean write(SocketWrapperBase<?> socketWrapper, boolean blocking) throws IOException {
+        Iterator<ByteBufferHolder> bufIter = buffers.iterator();
+        boolean dataLeft = false;
+        while (!dataLeft && bufIter.hasNext()) {
+            ByteBufferHolder buffer = bufIter.next();
+            buffer.flip();
+            if (blocking) {
+                socketWrapper.writeBlocking(buffer.getBuf());
+            } else {
+                socketWrapper.writeNonBlockingInternal(buffer.getBuf());
+            }
+            if (buffer.getBuf().remaining() == 0) {
+                bufIter.remove();
+            } else {
+                dataLeft = true;
+            }
+        }
+        return dataLeft;
+    }
+
+
+    public boolean write(Sink sink, boolean blocking) throws IOException {
+        Iterator<ByteBufferHolder> bufIter = buffers.iterator();
+        boolean dataLeft = false;
+        while (!dataLeft && bufIter.hasNext()) {
+            ByteBufferHolder buffer = bufIter.next();
+            buffer.flip();
+            dataLeft = sink.writeFromBuffer(buffer.getBuf(), blocking);
+            if (!dataLeft) {
+                bufIter.remove();
+            }
+        }
+        return dataLeft;
+    }
+
+
+    /**
+     * Interface implemented by clients of the WriteBuffer to enable data to be
+     * written back out from the buffer.
+     */
+    public interface Sink {
+        boolean writeFromBuffer(ByteBuffer buffer, boolean block) throws IOException;
+    }
+}