001// Copyright 2011 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.ioc.Resource;
018import org.apache.tapestry5.services.assets.*;
019
020import java.io.BufferedOutputStream;
021import java.io.ByteArrayOutputStream;
022import java.io.IOException;
023import java.util.zip.GZIPOutputStream;
024
025public class SRSCompressingInterceptor implements StreamableResourceSource
026{
027    private final int compressionCutoff;
028
029    private final StreamableResourceSource delegate;
030
031    public SRSCompressingInterceptor(int compressionCutoff, StreamableResourceSource delegate)
032    {
033        this.compressionCutoff = compressionCutoff;
034        this.delegate = delegate;
035    }
036
037    public StreamableResource getStreamableResource(Resource baseResource, StreamableResourceProcessing processing, ResourceDependencies dependencies)
038            throws IOException
039    {
040        StreamableResource streamable = delegate.getStreamableResource(baseResource, processing, dependencies);
041
042        return processing == StreamableResourceProcessing.COMPRESSION_ENABLED ? compress(streamable) : streamable;
043    }
044
045    private StreamableResource compress(StreamableResource uncompressed) throws IOException
046    {
047        if (uncompressed.getCompression() != CompressionStatus.COMPRESSABLE)
048        {
049            return uncompressed;
050        }
051
052        int size = uncompressed.getSize();
053
054        // Because of GZIP overhead, streams below a certain point actually get larger when compressed so
055        // we don't even try.
056
057        if (size < compressionCutoff)
058        {
059            return uncompressed;
060        }
061
062        ByteArrayOutputStream bos = new ByteArrayOutputStream(size);
063
064        GZIPOutputStream gos = new GZIPOutputStream(bos);
065        BufferedOutputStream buffered = new BufferedOutputStream(gos);
066
067        uncompressed.streamTo(buffered);
068
069        buffered.close();
070
071        BytestreamCache cache = new BytestreamCache(bos);
072
073        return new StreamableResourceImpl(uncompressed.getDescription(),
074                uncompressed.getContentType(), CompressionStatus.COMPRESSED,
075                uncompressed.getLastModified(), cache);
076    }
077}