Utils.java

package org.apache.jdbm;

import javax.crypto.Cipher;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOError;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.Comparator;

/**
 * Various utilities used in JDBM
 */
class Utils {

    /**
     * empty string is used as dummy value to represent null values in HashSet and TreeSet
     */
    static final String EMPTY_STRING = "";



    public static byte[] encrypt(Cipher cipherIn, ByteBuffer b) {
        if(cipherIn==null && b.hasArray())
            return b.array();
        byte[] bb = new byte[Storage.PAGE_SIZE];
        b.rewind();
        b.get(bb,0,Storage.PAGE_SIZE);
        return encrypt(cipherIn,bb);
    }
    
    public static byte[] encrypt(Cipher cipherIn, byte[] b) {
        if (cipherIn == null)
            return b;

        try {
            return cipherIn.doFinal(b);
        } catch (Exception e) {
            throw new IOError(e);
        }

    }


    /**
     * Compares comparables. Default comparator for most of java types
     */
    static final Comparator COMPARABLE_COMPARATOR = new Comparator<Comparable>() {
        public int compare(Comparable o1, Comparable o2) {
            return o1 == null && o2 != null ? -1 : (o1 != null && o2 == null ? 1 : o1.compareTo(o2));
        }
    };


    static String formatSpaceUsage(long size) {
        if (size < 1e4)
            return size + "B";
        else if (size < 1e7)
            return "" + Math.round(1D * size / 1024D) + "KB";
        else if (size < 1e10)
            return "" + Math.round(1D * size / 1e6) + "MB";
        else
            return "" + Math.round(1D * size / 1e9) + "GB";
    }


    static boolean allZeros(byte[] b) {
        for (int i = 0; i < b.length; i++) {
            if (b[i] != 0) return false;
        }
        return true;
    }

    
    static <E> E max(E e1, E e2, Comparator comp){
        if(e1 == null) return e2;
        if(e2 == null) return e1;

        if(comp == null)
            comp = COMPARABLE_COMPARATOR;
        return comp.compare(e1,e2)<0 ? e2:e1;
    }

    static <E> E min(E e1, E e2, Comparator comp){
        if(e1 == null) return e2;
        if(e2 == null) return e1;

        if(comp == null)
            comp = COMPARABLE_COMPARATOR;

        return comp.compare(e1,e2)>0 ? e2:e1;
    }
    
    
    static final Serializer<Object> NULL_SERIALIZER = new Serializer<Object>() {
        public void serialize(DataOutput out, Object obj) throws IOException {
            out.writeByte(11);
        }

        public Object deserialize(DataInput in) throws IOException, ClassNotFoundException {
            in.readByte();
            return null;
        }
    };

}