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   /*
    * Copyright 2015 The Netty Project
    *
    * The Netty Project 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:
    *
    *   https://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 io.netty.example.http2.tiles;
  
  import static io.netty.buffer.Unpooled.unreleasableBuffer;
  import static io.netty.example.http2.Http2ExampleUtil.toByteBuf;
  import io.netty.buffer.ByteBuf;
  
  import java.io.IOException;
  import java.util.HashMap;
  import java.util.Map;
  
  /**
   * Caches the images to avoid reading them every time from the disk.
   */
  public final class ImageCache {
  
      public static ImageCache INSTANCE = new ImageCache();
  
      private final Map<String, ByteBuf> imageBank = new HashMap<String, ByteBuf>(200);
  
      private ImageCache() {
          init();
      }
  
      public static String name(int x, int y) {
          return "tile-" + y + "-" + x + ".jpeg";
      }
  
      public ByteBuf image(int x, int y) {
          return imageBank.get(name(x, y));
      }
  
      private void init() {
          for (int y = 0; y < 10; y++) {
              for (int x = 0; x < 20; x++) {
                  try {
                      String name = name(x, y);
                      ByteBuf fileBytes = unreleasableBuffer(toByteBuf(getClass()
                              .getResourceAsStream(name)).asReadOnly());
                      imageBank.put(name, fileBytes);
                  } catch (IOException e) {
                      e.printStackTrace();
                  }
              }
          }
      }
  }