001// Copyright 2011-2013 The Apache Software Foundation
002//
003// Licensed under the Apache License, Version 2.0 (the "License");
004// you may not use this file except in compliance with the License.
005// You may obtain a copy of the License at
006//
007// http://www.apache.org/licenses/LICENSE-2.0
008//
009// Unless required by applicable law or agreed to in writing, software
010// distributed under the License is distributed on an "AS IS" BASIS,
011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012// See the License for the specific language governing permissions and
013// limitations under the License.
014
015package org.apache.tapestry5.internal.services.assets;
016
017import org.apache.tapestry5.commons.Resource;
018import org.apache.tapestry5.services.assets.*;
019
020import java.io.IOException;
021
022public class SRSCompressingInterceptor extends DelegatingSRS
023{
024    private final int compressionCutoff;
025
026    private final AssetChecksumGenerator checksumGenerator;
027
028    public SRSCompressingInterceptor(StreamableResourceSource delegate, int compressionCutoff, AssetChecksumGenerator checksumGenerator)
029    {
030        super(delegate);
031        this.compressionCutoff = compressionCutoff;
032        this.checksumGenerator = checksumGenerator;
033    }
034
035    public StreamableResource getStreamableResource(Resource baseResource, StreamableResourceProcessing processing, ResourceDependencies dependencies)
036            throws IOException
037    {
038        StreamableResource streamable = delegate.getStreamableResource(baseResource, processing, dependencies);
039
040        return processing == StreamableResourceProcessing.COMPRESSION_ENABLED ? compress(streamable) : streamable;
041    }
042
043    private StreamableResource compress(StreamableResource uncompressed) throws IOException
044    {
045        if (uncompressed.getCompression() != CompressionStatus.COMPRESSABLE)
046        {
047            return uncompressed;
048        }
049
050        int size = uncompressed.getSize();
051
052        // Because of GZIP overhead, streams below a certain point actually get larger when compressed so
053        // we don't even try.
054
055        if (size < compressionCutoff)
056        {
057            return uncompressed;
058        }
059
060        return new CompressedStreamableResource(uncompressed, checksumGenerator);
061    }
062}