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   /*
    * Copyright 2018 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.handler.ssl;
  
  import io.netty.buffer.ByteBufAllocator;
  
  import javax.net.ssl.X509KeyManager;
  import java.util.Iterator;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  
  /**
   * {@link OpenSslKeyMaterialProvider} that will cache the {@link OpenSslKeyMaterial} to reduce the overhead
   * of parsing the chain and the key for generation of the material.
   */
  final class OpenSslCachingKeyMaterialProvider extends OpenSslKeyMaterialProvider {
  
      private final int maxCachedEntries;
      private volatile boolean full;
      private final ConcurrentMap<String, OpenSslKeyMaterial> cache = new ConcurrentHashMap<String, OpenSslKeyMaterial>();
  
      OpenSslCachingKeyMaterialProvider(X509KeyManager keyManager, String password, int maxCachedEntries) {
          super(keyManager, password);
          this.maxCachedEntries = maxCachedEntries;
      }
  
      @Override
      OpenSslKeyMaterial chooseKeyMaterial(ByteBufAllocator allocator, String alias) throws Exception {
          OpenSslKeyMaterial material = cache.get(alias);
          if (material == null) {
              material = super.chooseKeyMaterial(allocator, alias);
              if (material == null) {
                  // No keymaterial should be used.
                  return null;
              }
  
              if (full) {
                  return material;
              }
              if (cache.size() > maxCachedEntries) {
                  full = true;
                  // Do not cache...
                  return material;
              }
              OpenSslKeyMaterial old = cache.putIfAbsent(alias, material);
              if (old != null) {
                  material.release();
                  material = old;
              }
          }
          // We need to call retain() as we want to always have at least a refCnt() of 1 before destroy() was called.
          return material.retain();
      }
  
      @Override
      void destroy() {
          // Remove and release all entries.
          do  {
              Iterator<OpenSslKeyMaterial> iterator = cache.values().iterator();
              while (iterator.hasNext()) {
                  iterator.next().release();
                  iterator.remove();
              }
          } while (!cache.isEmpty());
      }
  }