java/src/main/com/google/appengine/api/files/FileReadChannelImpl.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 FileReadChannel}.
  11  *
  12  */
  13 @Deprecated
  14 class FileReadChannelImpl implements FileReadChannel {
  15
  16   private FileServiceImpl fileService;
  17   private AppEngineFile file;
  18   private long position;
  19   private boolean isOpen;
  20   private boolean reachedEOF;
  21   private final Object lock = new Object();
  22
  23   FileReadChannelImpl(AppEngineFile f, FileServiceImpl fs) {
  24     this.file = f;
  25     this.fileService = fs;
  26     isOpen = true;
  27     reachedEOF = false;
  28     if (null == file) {
  29       throw new NullPointerException("file is null");
  30     }
  31     if (null == fs) {
  32       throw new NullPointerException("fs is null");
  33     }
  34     if (!f.isReadable()) {
  35       throw new IllegalArgumentException("file is not readable");
  36     }
  37   }
  38
  39   private void checkOpen() throws ClosedChannelException {
  40     synchronized (lock) {
  41       if (!isOpen) {
  42         throw new ClosedChannelException();
  43       }
  44     }
  45   }
  46
  47   /**
  48    * {@inheritDoc}
  49    * @throws ClosedChannelException
  50    */
  51   @Override
  52   public long position() throws ClosedChannelException {
  53     synchronized (lock) {
  54       checkOpen();
  55       return position;
  56     }
  57   }
  58
  59   /**
  60    * {@inheritDoc}
  61    */
  62   @Override
  63   public FileReadChannel position(long newPosition) throws IOException {
  64     if (newPosition < 0) {
  65       throw new IllegalArgumentException("newPosition may not be negative");
  66     }
  67     synchronized (lock) {
  68       checkOpen();
  69       position = newPosition;
  70       reachedEOF = false;
  71       return this;
  72     }
  73   }
  74
  75   /**
  76    * {@inheritDoc}
  77    */
  78   @Override
  79   public int read(ByteBuffer dst) throws IOException {
  80     synchronized (lock) {
  81       if (reachedEOF) {
  82         return -1;
  83       }
  84       int numBytesRead = fileService.read(file, dst, position);
  85       if (numBytesRead >= 0) {
  86         position += numBytesRead;
  87       } else {
  88         reachedEOF = true;
  89       }
  90       return numBytesRead;
  91     }
  92   }
  93
  94   /**
  95    * {@inheritDoc}
  96    */
  97   @Override
  98   public boolean isOpen() {
  99     synchronized (lock) {
 100       return isOpen;
 101     }
 102   }
 103
 104   /**
 105    * {@inheritDoc}
 106    */
 107   @Override
 108   public void close() throws IOException {
 109     synchronized (lock) {
 110       if (!isOpen) {
 111         return;
 112       }
 113       fileService.close(file, false);
 114       isOpen = false;
 115     }
 116   }
 117
 118   @Override
 119   public String toString() {
 120     return "FileReadChannel [file=" + file + ", position=" + position + ", isOpen=" + isOpen
 121         + ", reachedEOF=" + reachedEOF + "]";
 122   }
 123 }