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Apache Geode provides a database-like consistency model, reliable transaction processing and a shared-nothing architecture to maintain very low latency performance with high concurrency processing

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more contributor license
 * agreements. See the NOTICE file distributed with this work for additional information regarding
 * copyright ownership. The ASF 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
 *
 * http://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 org.apache.geode.internal.memcached.commands;

import java.nio.ByteBuffer;

import org.apache.geode.cache.Cache;
import org.apache.geode.cache.Region;
import org.apache.geode.internal.memcached.Reply;
import org.apache.geode.internal.memcached.RequestReader;
import org.apache.geode.internal.memcached.ResponseStatus;
import org.apache.geode.internal.memcached.ValueWrapper;

/**
 * general format of the command is:

 * 
 * <command name> <key> <flags> <exptime> <bytes> [noreply]\r\n
 * 

 * 
 * "replace" means "store this data, but only if the server *does* already hold data for this key".
 * 
 */
public class ReplaceCommand extends StorageCommand {

  @Override
  public ByteBuffer processStorageCommand(String key, byte[] value, int flags, Cache cache) {
    Region r = getMemcachedRegion(cache);
    Object oldVal = r.replace(key, ValueWrapper.getWrappedValue(value, flags));
    String reply = null;
    if (oldVal == null) {
      reply = Reply.NOT_STORED.toString();
    } else {
      reply = Reply.STORED.toString();
    }
    return asciiCharset.encode(reply);
  }

  @Override
  public ByteBuffer processBinaryStorageCommand(Object key, byte[] value, long cas, int flags,
      Cache cache, RequestReader request) {
    ByteBuffer response = request.getResponse();
    Region r = getMemcachedRegion(cache);
    ValueWrapper val = ValueWrapper.getWrappedValue(value, flags);
    boolean success = false;

    try {
      if (cas != 0L) {
        ValueWrapper expected = ValueWrapper.getDummyValue(cas);
        success = r.replace(key, expected, val);
      } else {
        success = r.replace(key, val) != null;
      }
    } catch (Exception e) {
      return handleBinaryException(key, request, response, "replace", e);
    }

    if (getLogger().fineEnabled()) {
      getLogger().fine("replace:key:" + key + " cas:" + cas + " success:" + success);
    }

    // set status
    if (success) {
      if (isQuiet()) {
        return null;
      }
      response.putShort(POSITION_RESPONSE_STATUS, ResponseStatus.NO_ERROR.asShort());
      response.putLong(POSITION_CAS, val.getVersion());
    } else {
      if (cas != 0L) {
        response.putShort(POSITION_RESPONSE_STATUS, ResponseStatus.KEY_EXISTS.asShort());
      } else {
        response.putShort(POSITION_RESPONSE_STATUS, ResponseStatus.KEY_NOT_FOUND.asShort());
      }
      // set CAS
      // response.putLong(POSITION_CAS, val.getVersion());
    }
    return response;
  }

  /**
   * Overridden by Q command
   */
  protected boolean isQuiet() {
    return false;
  }
}