com.metamx.common.io.smoosh.SmooshedFileMapper.java Source code

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Here is the source code for com.metamx.common.io.smoosh.SmooshedFileMapper.java

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/*
 * Copyright 2011,2012 Metamarkets Group Inc.
 *
 * Licensed 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 com.metamx.common.io.smoosh;

import com.google.common.base.Charsets;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.io.Closeables;
import com.google.common.io.Files;
import com.metamx.common.ByteBufferUtils;
import com.metamx.common.ISE;

import java.io.BufferedReader;
import java.io.Closeable;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;
import java.util.List;
import java.util.Map;
import java.util.Set;

/**
 * Class that works in conjunction with FileSmoosher.  This class knows how to map in a set of files smooshed
 * by the FileSmoosher.
 */
public class SmooshedFileMapper implements Closeable {
    public static SmooshedFileMapper load(File baseDir) throws IOException {
        File metaFile = FileSmoosher.metaFile(baseDir);

        BufferedReader in = null;
        try {
            in = new BufferedReader(new InputStreamReader(new FileInputStream(metaFile), Charsets.UTF_8));

            String line = in.readLine();
            if (line == null) {
                throw new ISE("First line should be version,maxChunkSize,numChunks, got null.");
            }

            String[] splits = line.split(",");
            if (!"v1".equals(splits[0])) {
                throw new ISE("Unknown version[%s], v1 is all I know.", splits[0]);
            }
            if (splits.length != 3) {
                throw new ISE("Wrong number of splits[%d] in line[%s]", splits.length, line);
            }
            final Integer numFiles = Integer.valueOf(splits[2]);
            List<File> outFiles = Lists.newArrayListWithExpectedSize(numFiles);

            for (int i = 0; i < numFiles; ++i) {
                outFiles.add(FileSmoosher.makeChunkFile(baseDir, i));
            }

            Map<String, Metadata> internalFiles = Maps.newTreeMap();
            while ((line = in.readLine()) != null) {
                splits = line.split(",");

                if (splits.length != 4) {
                    throw new ISE("Wrong number of splits[%d] in line[%s]", splits.length, line);
                }
                internalFiles.put(splits[0], new Metadata(Integer.parseInt(splits[1]), Integer.parseInt(splits[2]),
                        Integer.parseInt(splits[3])));
            }

            return new SmooshedFileMapper(outFiles, internalFiles);
        } finally {
            Closeables.close(in, false);
        }
    }

    private final List<File> outFiles;
    private final Map<String, Metadata> internalFiles;
    private final List<MappedByteBuffer> buffersList = Lists.newArrayList();

    private SmooshedFileMapper(List<File> outFiles, Map<String, Metadata> internalFiles) {
        this.outFiles = outFiles;
        this.internalFiles = internalFiles;
    }

    public Set<String> getInternalFilenames() {
        return internalFiles.keySet();
    }

    public ByteBuffer mapFile(String name) throws IOException {
        final Metadata metadata = internalFiles.get(name);
        if (metadata == null) {
            return null;
        }

        final int fileNum = metadata.getFileNum();
        while (buffersList.size() <= fileNum) {
            buffersList.add(null);
        }

        MappedByteBuffer mappedBuffer = buffersList.get(fileNum);
        if (mappedBuffer == null) {
            mappedBuffer = Files.map(outFiles.get(fileNum));
            buffersList.set(fileNum, mappedBuffer);
        }

        ByteBuffer retVal = mappedBuffer.duplicate();
        retVal.position(metadata.getStartOffset()).limit(metadata.getEndOffset());
        return retVal.slice();
    }

    @Override
    public void close() throws IOException {
        for (MappedByteBuffer mappedByteBuffer : buffersList) {
            ByteBufferUtils.unmap(mappedByteBuffer);
        }
    }
}