BytesSchemaVersion.java

/**
 * 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 org.apache.pulsar.common.protocol.schema;

import java.io.Serializable;
import java.util.Arrays;
import java.util.Comparator;

/**
 * Bytes schema version
 */
public class BytesSchemaVersion implements SchemaVersion, Comparable<BytesSchemaVersion> {

    private static final char[] HEX_CHARS_UPPER = {
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'
    };

    private final byte[] bytes;
    // cache the hash code for the string, default to 0
    private int hashCode;

    private BytesSchemaVersion(byte[] bytes) {
        this.bytes = bytes;
    }

    @Override
    public byte[] bytes() {
        return bytes;
    }

    public static BytesSchemaVersion of(byte[] bytes) {
        return bytes != null ? new BytesSchemaVersion(bytes) : null;
    }

    /**
     * Get the data from the Bytes.
     * @return The underlying byte array
     */
    public byte[] get() {
        return this.bytes;
    }

    /**
     * The hashcode is cached except for the case where it is computed as 0, in which
     * case we compute the hashcode on every call.
     *
     * @return the hashcode
     */
    @Override
    public int hashCode() {
        if (hashCode == 0) {
            hashCode = Arrays.hashCode(bytes);
        }
        return hashCode;
    }

    @Override
    public boolean equals(Object other) {
        if (this == other) {
            return true;
        }
        if (other == null) {
            return false;
        }

        // we intentionally use the function to compute hashcode here
        if (this.hashCode() != other.hashCode()) {
            return false;
        }

        if (other instanceof BytesSchemaVersion) {
            return Arrays.equals(this.bytes, ((BytesSchemaVersion) other).get());
        }

        return false;
    }

    @Override
    public int compareTo(BytesSchemaVersion that) {
        return BYTES_LEXICO_COMPARATOR.compare(this.bytes, that.bytes);
    }

    @Override
    public String toString() {
        return BytesSchemaVersion.toString(bytes, 0, bytes.length);
    }

    /**
     * Write a printable representation of a byte array. Non-printable
     * characters are hex escaped in the format \\x%02X, eg:
     * \x00 \x05 etc.
     *
     * This function is brought from org.apache.hadoop.hbase.util.Bytes
     *
     * @param b array to write out
     * @param off offset to start at
     * @param len length to write
     * @return string output
     */
    private static String toString(final byte[] b, int off, int len) {
        StringBuilder result = new StringBuilder();

        if (b == null)
            return result.toString();

        // just in case we are passed a 'len' that is > buffer length...
        if (off >= b.length)
            return result.toString();

        if (off + len > b.length)
            len = b.length - off;

        for (int i = off; i < off + len; ++i) {
            int ch = b[i] & 0xFF;
            if (ch >= ' ' && ch <= '~' && ch != '\\') {
                result.append((char) ch);
            } else {
                result.append("\\x");
                result.append(HEX_CHARS_UPPER[ch / 0x10]);
                result.append(HEX_CHARS_UPPER[ch % 0x10]);
            }
        }
        return result.toString();
    }

    /**
     * A byte array comparator based on lexicograpic ordering.
     */
    public final static ByteArrayComparator BYTES_LEXICO_COMPARATOR = new LexicographicByteArrayComparator();

    public interface ByteArrayComparator extends Comparator<byte[]>, Serializable {

        int compare(final byte[] buffer1, int offset1, int length1,
                    final byte[] buffer2, int offset2, int length2);
    }

    private static class LexicographicByteArrayComparator implements ByteArrayComparator {

        private static final long serialVersionUID = -1915703761143534937L;

        @Override
        public int compare(byte[] buffer1, byte[] buffer2) {
            return compare(buffer1, 0, buffer1.length, buffer2, 0, buffer2.length);
        }

        public int compare(final byte[] buffer1, int offset1, int length1,
                           final byte[] buffer2, int offset2, int length2) {

            // short circuit equal case
            if (buffer1 == buffer2 &&
                    offset1 == offset2 &&
                    length1 == length2) {
                return 0;
            }

            // similar to Arrays.compare() but considers offset and length
            int end1 = offset1 + length1;
            int end2 = offset2 + length2;
            for (int i = offset1, j = offset2; i < end1 && j < end2; i++, j++) {
                int a = buffer1[i] & 0xff;
                int b = buffer2[j] & 0xff;
                if (a != b) {
                    return a - b;
                }
            }
            return length1 - length2;
        }
    }
}