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      1 /*
      2  * Copyright (C) 2014 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.camera.async;
     18 
     19 import java.util.concurrent.TimeUnit;
     20 import java.util.concurrent.TimeoutException;
     21 
     22 /**
     23  * An input stream of objects which can be closed from either the producer or
     24  * the consumer.
     25  */
     26 public interface BufferQueue<T> extends SafeCloseable {
     27     @Override
     28     public void close();
     29 
     30     /**
     31      * Blocks, returning the next available value.
     32      *
     33      * @return The next available value.
     34      * @throws InterruptedException If interrupted while waiting for the next
     35      *             value.
     36      * @throws com.android.camera.async.BufferQueue.BufferQueueClosedException If the stream is closed and no more values
     37      *             will be available.
     38      */
     39     public T getNext() throws InterruptedException, BufferQueueClosedException;
     40 
     41     /**
     42      * Blocks, returning the next available value.
     43      *
     44      * @param timeout The maximum amount of time to wait.
     45      * @param unit The unit associated with the timeout.
     46      * @return The next available value.
     47      * @throws InterruptedException If interrupted while waiting for the next
     48      *             value.
     49      * @throws com.android.camera.async.BufferQueue.BufferQueueClosedException If the stream is closed and no more values
     50      *             will be available.
     51      * @throws TimeoutException If no new value is made available within the
     52      *             specified time limit.
     53      */
     54     public T getNext(long timeout, TimeUnit unit) throws InterruptedException, TimeoutException,
     55             BufferQueueClosedException;
     56 
     57     /**
     58      * Immediately returns the next available value without removing it from the
     59      * stream.
     60      *
     61      * @return The next available value if one exists, or null if no value
     62      *         exists yet or the stream is closed.
     63      */
     64     public T peekNext();
     65 
     66     /**
     67      * Immediately discards the next available value, if one exists.
     68      */
     69     public void discardNext();
     70 
     71     /**
     72      * @return True if the stream has been closed by either the producer or the
     73      *         consumer.
     74      */
     75     public boolean isClosed();
     76 
     77     /**
     78      * Indicates that the stream is closed and no more results are available.
     79      */
     80     public static class BufferQueueClosedException extends Exception {
     81     }
     82 }
     83