Merge pull request #415 from Massive-Dynamics/fix-414

Adds a method to get the buffer for a specific index in CompositeByteBuf

buffer/src/main/java/io/netty/buffer/CompositeByteBuf.java

@@ -575,6 +575,34 @@ public class CompositeByteBuf extends AbstractByteBuf {
         dst.writerIndex(dst.capacity());
     }
 
+    /**
+     * Returns the {@link ByteBuf} portion of this {@link CompositeByteBuf} that
+     * contains the specified {@code index}. This is an expert method!
+     *
+     * <p>
+     * Please note that since a {@link CompositeByteBuf} is made up of
+     * multiple {@link ByteBuf}s, this does <em>not</em> return the full buffer.
+     * Instead, it only returns a portion of the composite buffer where the
+     * index is located
+     * </p>
+     *
+     * @param index The {@code index} to search for and include in the returned {@link ByteBuf}
+     * @return The {@link ByteBuf} that contains the specified {@code index}
+     * @throws IndexOutOfBoundsException when the specified {@code index} is
+     * less than zero, or larger than {@code capacity()}
+     */
+    public ByteBuf getBufferFor(int index) throws IndexOutOfBoundsException {
+        if (index < 0 || index >= capacity()) {
+            throw new IndexOutOfBoundsException("Invalid index: " + index
+                    + " - Bytes needed: " + index + ", maximum is "
+                    + capacity());
+        }
+
+        //Return the component byte buffer
+        return components[componentId(index)];
+
+    }
+
     @Override
     public ByteBuf slice(int index, int length) {
         if (index == 0) {

buffer/src/test/java/io/netty/buffer/AbstractCompositeChannelBufferTest.java

@@ -16,6 +16,7 @@
 package io.netty.buffer;
 
 import static io.netty.buffer.Unpooled.*;
+import java.io.IOException;
 import static org.junit.Assert.*;
 
 import java.nio.ByteBuffer;
@@ -89,6 +90,29 @@ public abstract class AbstractCompositeChannelBufferTest extends
     protected boolean discardReadBytesDoesNotMoveWritableBytes() {
         return false;
     }
+    
+    /**
+     * Tests the "getBufferFor" method
+     */
+    @Test
+    public void testGetBufferFor() throws IOException {
+        CompositeByteBuf buf = (CompositeByteBuf) Unpooled.wrappedBuffer(new byte[] { 1, 2, 3, 4, 5 }, new byte[] {4, 5, 6, 7, 8, 9, 26});
+    
+        //Ensure that a random place will be fine
+        assertEquals(buf.getBufferFor(2).capacity(), 5);
+        
+        //Loop through each byte
+        
+        byte index = 0;
+        
+        while (index < buf.capacity()) {
+            ByteBuf _buf = buf.getBufferFor(index++);
+            assertNotNull(_buf);
+            assertTrue(_buf.capacity() > 0);
+            assertNotNull(_buf.getByte(0));
+            assertNotNull(_buf.getByte(_buf.readableBytes() - 1));
+        }
+    }
 
     @Test
     public void testDiscardReadBytes3() {