com.bigdata.dastor.dht.CollatingOrderPreservingPartitioner.java Source code

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Here is the source code for com.bigdata.dastor.dht.CollatingOrderPreservingPartitioner.java

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/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.bigdata.dastor.dht;

import java.math.BigInteger;
import java.text.Collator;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Locale;
import java.util.Random;

import org.apache.commons.lang.ArrayUtils;

import com.bigdata.dastor.db.DecoratedKey;
import com.bigdata.dastor.utils.FBUtilities;
import com.bigdata.dastor.utils.Pair;

public class CollatingOrderPreservingPartitioner implements IPartitioner<BytesToken> {
    static final Collator collator = Collator.getInstance(new Locale("en", "US"));

    public static final BytesToken MINIMUM = new BytesToken(ArrayUtils.EMPTY_BYTE_ARRAY);

    public static final BigInteger BYTE_MASK = new BigInteger("255");

    public DecoratedKey<BytesToken> decorateKey(String key) {
        return new DecoratedKey<BytesToken>(getToken(key), key);
    }

    public DecoratedKey<BytesToken> convertFromDiskFormat(String key) {
        return new DecoratedKey<BytesToken>(getToken(key), key);
    }

    public String convertToDiskFormat(DecoratedKey<BytesToken> key) {
        return key.key;
    }

    public BytesToken midpoint(BytesToken ltoken, BytesToken rtoken) {
        int sigbytes = Math.max(ltoken.token.length, rtoken.token.length);
        BigInteger left = bigForBytes(ltoken.token, sigbytes);
        BigInteger right = bigForBytes(rtoken.token, sigbytes);

        Pair<BigInteger, Boolean> midpair = FBUtilities.midpoint(left, right, 8 * sigbytes);
        return new BytesToken(bytesForBig(midpair.left, sigbytes, midpair.right));
    }

    /**
     * Convert a byte array containing the most significant of 'sigbytes' bytes
     * representing a big-endian magnitude into a BigInteger.
     */
    private BigInteger bigForBytes(byte[] bytes, int sigbytes) {
        if (bytes.length != sigbytes) {
            // append zeros
            bytes = Arrays.copyOf(bytes, sigbytes);
        }
        return new BigInteger(1, bytes);
    }

    /**
     * Convert a (positive) BigInteger into a byte array representing its magnitude.
     * If remainder is true, an additional byte with the high order bit enabled
     * will be added to the end of the array
     */
    private byte[] bytesForBig(BigInteger big, int sigbytes, boolean remainder) {
        byte[] bytes = new byte[sigbytes + (remainder ? 1 : 0)];
        if (remainder) {
            // remaining bit is the most significant in the last byte
            bytes[sigbytes] |= 0x80;
        }
        // bitmask for a single byte
        for (int i = 0; i < sigbytes; i++) {
            int maskpos = 8 * (sigbytes - (i + 1));
            // apply bitmask and get byte value
            bytes[i] = (byte) (big.and(BYTE_MASK.shiftLeft(maskpos)).shiftRight(maskpos).intValue() & 0xFF);
        }
        return bytes;
    }

    public BytesToken getMinimumToken() {
        return MINIMUM;
    }

    public BytesToken getRandomToken() {
        Random r = new Random();
        byte[] buffer = new byte[16];
        r.nextBytes(buffer);
        return new BytesToken(buffer);
    }

    private final Token.TokenFactory<byte[]> tokenFactory = new Token.TokenFactory<byte[]>() {
        public byte[] toByteArray(Token<byte[]> bytesToken) {
            return bytesToken.token;
        }

        public Token<byte[]> fromByteArray(byte[] bytes) {
            return new BytesToken(bytes);
        }

        public String toString(Token<byte[]> bytesToken) {
            return FBUtilities.bytesToHex(bytesToken.token);
        }

        public Token<byte[]> fromString(String string) {
            return new BytesToken(FBUtilities.hexToBytes(string));
        }
    };

    public Token.TokenFactory<byte[]> getTokenFactory() {
        return tokenFactory;
    }

    public boolean preservesOrder() {
        return true;
    }

    public BytesToken getToken(String key) {
        if (key.isEmpty())
            return MINIMUM;
        return new BytesToken(collator.getCollationKey(key).toByteArray());
    }
}