AR-383: Optimized overwrite behaviour for ContentWriter. Content will only be duplicated for the writes if explicitly requesting a random-access file without the truncate option

git-svn-id: https://svn.alfresco.com/repos/alfresco-enterprise/alfresco/HEAD/root@2254 c4b6b30b-aa2e-2d43-bbcb-ca4b014f7261

source/java/org/alfresco/service/cmr/repository/ContentAccessor.java

@@ -45,6 +45,10 @@ public interface ContentAccessor
     
     /**
      * Set the transaction provider that will be used when stream listeners are called.
+     * No transactions are started unless there are listeners present to be executed.
+     * For consistency, the execution of listeners <b>will not</b> be allowed to proceed
+     * unless this property has been set OR the channel close operations are executed
+     * within the context of a live transaction.
      * 
      * @param transactionService a transaction provider
      */

source/java/org/alfresco/service/cmr/repository/ContentReader.java

@@ -19,6 +19,7 @@ package org.alfresco.service.cmr.repository;
 import java.io.File;
 import java.io.InputStream;
 import java.io.OutputStream;
+import java.nio.channels.FileChannel;
 import java.nio.channels.ReadableByteChannel;
 
 /**
@@ -86,6 +87,19 @@ public interface ContentReader extends ContentAccessor
      */
     public ReadableByteChannel getReadableChannel() throws ContentIOException;
     
+    /**
+     * Provides read-only, random-access to the underlying content.  In general, this method
+     * should be considered more expensive than the sequential-access method,
+     * {@link #getReadableChannel()}.
+     * 
+     * @return Returns a random-access channel onto the content
+     * @throws ContentIOException
+     *
+     * @see #getReadableChannel()
+     * @see java.io.RandomAccessFile#getChannel()
+     */
+    public FileChannel getFileChannel() throws ContentIOException;
+
     /**
      * Get a stream to read from the underlying channel
      * 

source/java/org/alfresco/service/cmr/repository/ContentWriter.java

@@ -19,6 +19,7 @@ package org.alfresco.service.cmr.repository;
 import java.io.File;
 import java.io.InputStream;
 import java.io.OutputStream;
+import java.nio.channels.FileChannel;
 import java.nio.channels.WritableByteChannel;
 
 
@@ -77,6 +78,23 @@ public interface ContentWriter extends ContentAccessor
      */
     public WritableByteChannel getWritableChannel() throws ContentIOException;
 
+    /**
+     * Provides read-write, random-access to the underlying content.  In general, this method
+     * should be considered more expensive than the sequential-access method,
+     * {@link #getWritableChannel()}.
+     * <p>
+     * Underlying implementations use the <code>truncate</code> parameter to determine the
+     * most effective means of providing access to the content.
+     * 
+     * @param truncate true to start with zero length content
+     * @return Returns a random-access channel onto the content
+     * @throws ContentIOException
+     *
+     * @see #getWritableChannel()
+     * @see java.io.RandomAccessFile#getChannel()
+     */
+    public FileChannel getFileChannel(boolean truncate) throws ContentIOException;
+
     /**
      * Get a stream to write to the underlying channel.
      *