| /* |
| * 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.drill.common; |
| |
| /** |
| * A class similar to Pointer<>, but with features unique to holding |
| * AutoCloseable pointers. The AutoCloseablePointer<> must be closed |
| * when it will no longer be used. |
| * |
| * <p>If you're familiar with C++/Boost's shared_ptr<>, you might recognize |
| * some of the features here.</p> |
| * |
| * @param <T> type of the pointer |
| */ |
| public final class AutoCloseablePointer<T extends AutoCloseable> implements AutoCloseable { |
| private T pointer; |
| |
| /** |
| * Constructor for a null-valued pointer. |
| */ |
| public AutoCloseablePointer() { |
| pointer = null; |
| } |
| |
| /** |
| * Constructor for a pointer value. |
| * |
| * @param pointer the initial pointer value |
| */ |
| public AutoCloseablePointer(final T pointer) { |
| this.pointer = pointer; |
| } |
| |
| @Override |
| public void close() throws Exception { |
| assign(null); |
| } |
| |
| /** |
| * Get the raw pointer out for use. |
| * |
| * @return the raw pointer |
| */ |
| public T get() { |
| return pointer; |
| } |
| |
| /** |
| * The caller adopts the pointer; the holder is set to |
| * null, and will no longer be responsible for close()ing this pointer. |
| * |
| * @return the pointer being adopted; may be null |
| */ |
| public T adopt() { |
| final T p = pointer; |
| pointer = null; |
| return p; |
| } |
| |
| /** |
| * Assign a new pointer to this holder. Any currently held pointer |
| * will first be closed. If closing the currently held pointer throws |
| * an exception, the new pointer is still assigned, and the holder must still |
| * be closed to close that. |
| * |
| * <p>This makes it convenient to assign a new pointer without having to check |
| * for a previous value and worry about cleaning it up; this does all that.</p> |
| * |
| * @param newP the new pointer to hold |
| * @throws Exception any exception thrown by closing the currently held |
| * pointer |
| */ |
| public void assign(final T newP) throws Exception { |
| try { |
| if (pointer != null) { |
| pointer.close(); |
| } |
| } finally { |
| pointer = newP; |
| } |
| } |
| |
| /** |
| * Like {@link #assign(AutoCloseable)}, except that any exception thrown |
| * by closing the previously held pointer is wrapped with (an unchecked) |
| * {@link RuntimeException}. |
| * |
| * @param newP the new pointer to hold |
| */ |
| public void assignNoChecked(final T newP) { |
| try { |
| assign(newP); |
| } catch(final Exception e) { |
| throw new RuntimeException(e); |
| } |
| } |
| } |