broker-plugins/amqp-1-0-protocol/src/main/java/org/apache/qpid/server/protocol/v1_0/codec/StringTypeConstructor.java

/*
 *
 * 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.qpid.server.protocol.v1_0.codec;

import static java.nio.charset.StandardCharsets.UTF_8;

import java.nio.ByteBuffer;

import com.google.common.cache.Cache;

import org.apache.qpid.server.bytebuffer.QpidByteBuffer;
import org.apache.qpid.server.protocol.v1_0.type.AmqpErrorException;
import org.apache.qpid.server.protocol.v1_0.type.transport.AmqpError;
import org.apache.qpid.server.virtualhost.CacheFactory;
import org.apache.qpid.server.virtualhost.NullCache;

public class StringTypeConstructor extends VariableWidthTypeConstructor<String>
{
    private static final NullCache<ByteBuffer, String> NULL_CACHE = new NullCache<>();

    private static final ThreadLocal<Cache<ByteBuffer, String>> CACHE =
            ThreadLocal.withInitial(() -> CacheFactory.getCache("stringCache", NULL_CACHE));

    public static StringTypeConstructor getInstance(int i)
    {
        return new StringTypeConstructor(i);
    }


    private StringTypeConstructor(int size)
    {
        super(size);
    }

    @Override
    public String construct(final QpidByteBuffer in, final ValueHandler handler) throws AmqpErrorException
    {
        int size;

        if (!in.hasRemaining(getSize()))
        {
            throw new AmqpErrorException(AmqpError.DECODE_ERROR, "Cannot construct string: insufficient input data");
        }

        if (getSize() == 1)
        {
            size = in.getUnsignedByte();
        }
        else
        {
            size = in.getInt();
        }

        if (!in.hasRemaining(size))
        {
            throw new AmqpErrorException(AmqpError.DECODE_ERROR, "Cannot construct string: insufficient input data");
        }

        byte[] data = new byte[size];
        in.get(data);

        ByteBuffer buffer = ByteBuffer.wrap(data);
        String cached = getCache().getIfPresent(buffer);
        if (cached == null)
        {
            cached = new String(data, UTF_8);
            getCache().put(buffer, cached);
        }
        return cached;
    }

    static Cache<ByteBuffer, String> getCache()
    {
        return CACHE.get();
    }

    static void setCache(final Cache<ByteBuffer, String> cache)
    {
        CACHE.set(cache);
    }
}