java/src/main/com/google/appengine/api/files/FileWriteChannelImpl.java

   1 // Copyright 2011 Google Inc. All Rights Reserved.
   2
   3 package com.google.appengine.api.files;
   4
   5 import java.io.IOException;
   6 import java.nio.ByteBuffer;
   7 import java.nio.channels.ClosedChannelException;
   8
   9 /**
  10  * An implementation of {@code FileWriteChannel}.
  11  *
  12  */
  13 class FileWriteChannelImpl implements FileWriteChannel {
  14
  15   private FileServiceImpl fileService;
  16   private AppEngineFile file;
  17   private boolean lockHeld;
  18   private boolean isOpen;
  19   private final Object lock = new Object();
  20
  21   FileWriteChannelImpl(AppEngineFile f, boolean lock, FileServiceImpl fs) {
  22     this.file = f;
  23     this.lockHeld = lock;
  24     this.fileService = fs;
  25     isOpen = true;
  26     if (null == file) {
  27       throw new NullPointerException("file is null");
  28     }
  29     if (!f.isWritable()) {
  30       throw new IllegalArgumentException("file is not writable");
  31     }
  32   }
  33
  34   private void checkOpen() throws ClosedChannelException {
  35     if (!isOpen) {
  36       throw new ClosedChannelException();
  37     }
  38   }
  39
  40   /**
  41    * {@inheritDoc}
  42    */
  43   @Override
  44   public int write(ByteBuffer src) throws IOException {
  45     synchronized (lock) {
  46       return write(src, null);
  47     }
  48   }
  49
  50   /**
  51    * {@inheritDoc}
  52    */
  53   @Override
  54   public int write(ByteBuffer buffer, String sequenceKey) throws IOException {
  55     synchronized (lock) {
  56       checkOpen();
  57       return fileService.append(file, buffer, sequenceKey);
  58     }
  59   }
  60
  61   /**
  62    * {@inheritDoc}
  63    */
  64   @Override
  65   public boolean isOpen() {
  66     synchronized (lock) {
  67       return isOpen;
  68     }
  69   }
  70
  71   /**
  72    * {@inheritDoc}
  73    */
  74   @Override
  75   public void close() throws IOException {
  76     synchronized (lock) {
  77       if (!isOpen) {
  78         return;
  79       }
  80       fileService.close(file, false);
  81       isOpen = false;
  82     }
  83   }
  84
  85   /**
  86    * {@inheritDoc}
  87    */
  88   @Override
  89   public void closeFinally() throws IllegalStateException, IOException {
  90     synchronized (lock) {
  91       if (!lockHeld) {
  92         throw new IllegalStateException(
  93             "The lock for this file is not held by the current request");
  94       }
  95       if (isOpen) {
  96         fileService.close(file, true);
  97       } else {
  98         try {
  99           fileService.openForAppend(file, true);
 100           fileService.close(file, true);
 101         } catch (FinalizationException e) {
 102         }
 103       }
 104       isOpen = false;
 105     }
 106   }
 107
 108 }