CompressedIO.java

package edu.cmu.graphchi.io;

/**
 * Copyright [2012] [Aapo Kyrola, Guy Blelloch, Carlos Guestrin / Carnegie Mellon University]
 *
 * 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.
 */


import java.io.*;
import java.util.zip.*;

/**
 * Zlib-compressed I/O utilities.
 * @author akyrola
 */
public class CompressedIO {

    static boolean COMPRESSION_ENABLED = true;

    public static void readCompressed(File f, byte[] buf, int nbytes) throws FileNotFoundException, IOException {
        if (COMPRESSION_ENABLED) {
            BufferedInputStream bis = new BufferedInputStream(new FileInputStream(f));
            InflaterInputStream iis = new InflaterInputStream(bis);
            int read = 0;
            while (read < nbytes) {
                read += iis.read(buf, read, nbytes - read);
            }
            iis.close(); bis.close();
        } else {
            FileInputStream in = new FileInputStream(f);
            int read = 0;
            while (read < nbytes) {
                read += in.read(buf, read, buf.length - read);
            }
            in.close();
        }
    }

    public static void writeCompressed(File f, byte[] data, int nbytes) throws FileNotFoundException, IOException {
        if (COMPRESSION_ENABLED) {
            BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(f));
            DeflaterOutputStream dos = new DeflaterOutputStream(bos);
            dos.write(data, 0, nbytes);
            dos.close(); bos.close();
        } else {
            BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(f));
            bos.write(data, 0, nbytes);
            bos.close();
        }
    }

    /* Note: I realize this is not a good way to manage compression level (should not be part of the utility class). FIXME */
    public static void disableCompression() {
        COMPRESSION_ENABLED = false;
    }

    public static boolean isCompressionEnabled() {
        return COMPRESSION_ENABLED;
    }

    static {
        if ("0".equals(System.getProperty("graphchi.compression"))) {
            disableCompression();
        }
    }
}