Bytes.java

/*
 * Copyright © 2014 Cask Data, 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 co.cask.cdap.api.common;

import java.io.DataOutput;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.nio.ByteBuffer;
import java.nio.charset.Charset;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Iterator;
import java.util.NavigableMap;
import java.util.TreeMap;
import java.util.UUID;
import javax.annotation.Nullable;

/**
 * Utility class that handles byte arrays, conversions to/from other types,
 * comparisons, hash code generation, manufacturing keys for HashMaps or
 * HashSets, etc.
 */
@SuppressWarnings("javadoc")
public class Bytes {

  /**
   * Size of boolean in bytes.
   */
  public static final int SIZEOF_BOOLEAN = Byte.SIZE / Byte.SIZE;

  /**
   * Size of byte in bytes.
   */
  public static final int SIZEOF_BYTE = SIZEOF_BOOLEAN;

  /**
   * Size of char in bytes.
   */
  public static final int SIZEOF_CHAR = Character.SIZE / Byte.SIZE;

  /**
   * Size of double in bytes.
   */
  public static final int SIZEOF_DOUBLE = Double.SIZE / Byte.SIZE;

  /**
   * Size of float in bytes.
   */
  public static final int SIZEOF_FLOAT = Float.SIZE / Byte.SIZE;

  /**
   * Size of int in bytes.
   */
  public static final int SIZEOF_INT = Integer.SIZE / Byte.SIZE;

  /**
   * Size of long in bytes.
   */
  public static final int SIZEOF_LONG = Long.SIZE / Byte.SIZE;

  /**
   * Size of short in bytes.
   */
  public static final int SIZEOF_SHORT = Short.SIZE / Byte.SIZE;

  private static final char[] hexDigits = "0123456789abcdef".toCharArray();
  private static final Charset UTF_8 = Charset.forName("UTF-8");

  /**
   * Byte array comparator class.
   */
  public static class ByteArrayComparator implements Comparator<byte []> {
    /**
     * Constructor.
     */
    public ByteArrayComparator() {
      super();
    }
    @Override
    public int compare(byte [] left, byte [] right) {
      return compareTo(left, right);
    }
  }

  /**
   * Pass this to TreeMaps where byte [] are keys.
   */
  public static final Comparator<byte []> BYTES_COMPARATOR =
      new ByteArrayComparator();

  /**
   * Put bytes at the specified byte array position.
   * @param tgtBytes the byte array
   * @param tgtOffset position in the array
   * @param srcBytes array to write out
   * @param srcOffset source offset
   * @param srcLength source length
   * @return incremented offset
   */
  public static int putBytes(byte[] tgtBytes, int tgtOffset, byte[] srcBytes,
      int srcOffset, int srcLength) {
    System.arraycopy(srcBytes, srcOffset, tgtBytes, tgtOffset, srcLength);
    return tgtOffset + srcLength;
  }

  /**
   * Write a single byte out to the specified byte array position.
   * @param bytes the byte array
   * @param offset position in the array
   * @param b byte to write out
   * @return incremented offset
   */
  public static int putByte(byte[] bytes, int offset, byte b) {
    bytes[offset] = b;
    return offset + 1;
  }

  /**
   * Returns a new byte array, copied from the passed ByteBuffer.
   * @param bb A ByteBuffer
   * @return the byte array
   */
  public static byte[] toBytes(ByteBuffer bb) {
    int length = bb.remaining();
    byte [] result = new byte[length];
    int pos = bb.position();
    bb.get(result);
    bb.position(pos);
    return result;
  }

  /**
   * This method will convert utf8 encoded bytes into a string. If
   * an UnsupportedEncodingException occurs, this method will eat it
   * and return null instead.
   * @param b Presumed UTF-8 encoded byte array.
   * @return String made from <code>b</code>
   */
  public static String toString(final byte [] b) {
    if (b == null) {
      return null;
    }
    return toString(b, 0, b.length);
  }

  /**
   * Joins two byte arrays together using a separator.
   * @param b1 The first byte array.
   * @param sep The separator to use.
   * @param b2 The second byte array.
   */
  public static String toString(final byte [] b1,
      String sep,
      final byte [] b2) {
    return toString(b1, 0, b1.length) + sep + toString(b2, 0, b2.length);
  }

  /**
   * When we encode strings, we always specify UTF8 encoding.
   */
  public static final String UTF8_ENCODING = "UTF-8";

  /**
   * This method will convert utf8 encoded bytes into a string. If
   * an UnsupportedEncodingException occurs, this method will eat it
   * and return null instead.
   *
   * @param b Presumed UTF-8 encoded byte array.
   * @param off offset into array
   * @param len length of utf-8 sequence
   * @return String made from <code>b</code> or null
   */
  public static String toString(final byte [] b, int off, int len) {
    if (b == null) {
      return null;
    }
    if (len == 0) {
      return "";
    }
    try {
      return new String(b, off, len, UTF8_ENCODING);
    } catch (UnsupportedEncodingException e) {
      return null;
    }
  }

  /**
   * This method will convert the remaining bytes of a UTF8
   * encoded byte buffer into a string.
   *
   * @param buf Presumed UTF-8 encoded byte buffer.
   * @return String made from <code>buf</code> or null
   */
  public static String toString(ByteBuffer buf) {
    return toString(buf, UTF_8);
  }

  /**
   * This method will convert the remaining bytes of an
   * encoded byte buffer into a string of the given charset.
   *
   * @param buf Encoded byte buffer.
   * @param charset Charset of the string encoded in the byte buffer.
   * @return String made from <code>buf</code> or null
   */
  public static String toString(ByteBuffer buf, Charset charset) {
    if (buf == null) {
      return null;
    }
    buf.mark();
    String s = charset.decode(buf).toString();
    buf.reset();
    return s;
  }

  /**
   * Write a printable representation of a byte array.
   *
   * @param b byte array
   * @return string
   * @see #toStringBinary(byte[], int, int)
   */
  public static String toStringBinary(final byte [] b) {
    if (b == null) {
      return "null";
    }
    return toStringBinary(b, 0, b.length);
  }

  /**
   * Returns a string containing each byte, in order, as a two-digit unsigned
   * hexadecimal number in lower case.
   */
  public static String toHexString(byte [] bytes) {
    StringBuilder sb = new StringBuilder(2 * bytes.length);
    for (byte b : bytes) {
      sb.append(hexDigits[(b >> 4) & 0xf]).append(hexDigits[b & 0xf]);
    }
    return sb.toString();
  }

  /**
   * Converts the given byte buffer, from its array offset to its limit, to
   * a string. The position and the mark are ignored.
   *
   * @param buf a byte buffer
   * @return a string representation of the buffer's binary contents
   */
  public static String toStringBinary(ByteBuffer buf) {
    if (buf == null) {
      return "null";
    }
    return toStringBinary(buf.array(), buf.arrayOffset(), buf.limit());
  }

  /**
   * Write a printable representation of a byte array. Non-printable
   * characters are hex escaped in the format \\x%02X, eg:
   * \x00 \x05 etc
   *
   * @param b array to write out
   * @param off offset to start at
   * @param len length to write
   * @return string output
   */
  public static String toStringBinary(final byte [] b, int off, int len) {
    StringBuilder result = new StringBuilder();
    try {
      String first = new String(b, off, len, "ISO-8859-1");
      for (int i = 0; i < first.length(); ++i) {
        int ch = first.charAt(i) & 0xFF;
        if ((ch >= '0' && ch <= '9')
            || (ch >= 'A' && ch <= 'Z')
            || (ch >= 'a' && ch <= 'z')
            || " `~!@#$%^&*()-_=+[]{}\\|;:'\",.<>/?".indexOf(ch) >= 0) {
          result.append(first.charAt(i));
        } else {
          result.append(String.format("\\x%02X", ch));
        }
      }
    } catch (UnsupportedEncodingException e) {
    }
    return result.toString();
  }

  private static boolean isHexDigit(char c) {
    return
        (c >= 'A' && c <= 'F') ||
        (c >= '0' && c <= '9');
  }

  /**
   * Takes a ASCII digit in the range A-F0-9 and returns
   * the corresponding integer/ordinal value.
   * @param ch  The hex digit.
   * @return The converted hex value as a byte.
   */
  public static byte toBinaryFromHex(byte ch) {
    if (ch >= 'A' && ch <= 'F') {
      return (byte) ((byte) 10 + (byte) (ch - 'A'));
    }
    // else
    return (byte) (ch - '0');
  }

  public static byte [] toBytesBinary(String in) {
    // this may be bigger than we need, but lets be safe.
    byte [] b = new byte[in.length()];
    int size = 0;
    for (int i = 0; i < in.length(); ++i) {
      char ch = in.charAt(i);
      if (ch == '\\') {
        // begin hex escape:
        char next = in.charAt(i + 1);
        if (next != 'x') {
          // invalid escape sequence, ignore this one.
          b[size++] = (byte) ch;
          continue;
        }
        // ok, take next 2 hex digits.
        char hd1 = in.charAt(i + 2);
        char hd2 = in.charAt(i + 3);

        // they need to be A-F0-9:
        if (!isHexDigit(hd1) ||
            !isHexDigit(hd2)) {
          // bogus escape code, ignore:
          continue;
        }
        // turn hex ASCII digit -> number
        byte d = (byte) ((toBinaryFromHex((byte) hd1) << 4) + toBinaryFromHex((byte) hd2));

        b[size++] = d;
        i += 3; // skip 3
      } else {
        b[size++] = (byte) ch;
      }
    }
    // resize:
    byte [] b2 = new byte[size];
    System.arraycopy(b, 0, b2, 0, size);
    return b2;
  }

  /**
   * Converts a string to a UTF-8 byte array.
   * @param s string
   * @return the byte array
   */
  public static byte[] toBytes(String s) {
    try {
      return s.getBytes(UTF8_ENCODING);
    } catch (UnsupportedEncodingException e) {
      return null;
    }
  }

  /**
   * Convert a boolean to a byte array. True becomes -1
   * and false becomes 0.
   *
   * @param b value
   * @return <code>b</code> encoded in a byte array.
   */
  public static byte [] toBytes(final boolean b) {
    return new byte[] { b ? (byte) -1 : (byte) 0 };
  }

  /**
   * Reverses {@link #toBytes(boolean)}.
   * @param b array
   * @return True or false.
   */
  public static boolean toBoolean(final byte [] b) {
    if (b.length != 1) {
      throw new IllegalArgumentException("Array has wrong size: " + b.length);
    }
    return b[0] != (byte) 0;
  }

  /**
   * Convert a long value to a byte array using big-endian.
   *
   * @param val value to convert
   * @return the byte array
   */
  public static byte[] toBytes(long val) {
    byte [] b = new byte[8];
    for (int i = 7; i > 0; i--) {
      b[i] = (byte) val;
      val >>>= 8;
    }
    b[0] = (byte) val;
    return b;
  }

  /**
   * Converts a byte array to a long value. Reverses
   * {@link #toBytes(long)}
   * @param bytes array
   * @return the long value
   */
  public static long toLong(byte[] bytes) {
    return toLong(bytes, 0, SIZEOF_LONG);
  }

  /**
   * Converts a byte array to a long value. Assumes there will be
   * {@link #SIZEOF_LONG} bytes available.
   *
   * @param bytes bytes
   * @param offset offset
   * @return the long value
   */
  public static long toLong(byte[] bytes, int offset) {
    return toLong(bytes, offset, SIZEOF_LONG);
  }

  /**
   * Converts a byte array to a long value.
   *
   * @param bytes array of bytes
   * @param offset offset into array
   * @param length length of data (must be {@link #SIZEOF_LONG})
   * @return the long value
   * @throws IllegalArgumentException if length is not {@link #SIZEOF_LONG} or
   * if there's not enough room in the array at the offset indicated.
   */
  public static long toLong(byte[] bytes, int offset, final int length) {
    if (length != SIZEOF_LONG || offset + length > bytes.length) {
      throw explainWrongLengthOrOffset(bytes, offset, length, SIZEOF_LONG);
    }
    long l = 0;
    for (int i = offset; i < offset + length; i++) {
      l <<= 8;
      l ^= bytes[i] & 0xFF;
    }
    return l;
  }

  private static IllegalArgumentException
  explainWrongLengthOrOffset(final byte[] bytes,
      final int offset,
      final int length,
      final int expectedLength) {
    String reason;
    if (length != expectedLength) {
      reason = "Wrong length: " + length + ", expected " + expectedLength;
    } else {
      reason = "offset (" + offset + ") + length (" + length + ") exceed the"
          + " capacity of the array: " + bytes.length;
    }
    return new IllegalArgumentException(reason);
  }

  /**
   * Put a long value out to the specified byte array position.
   * @param bytes the byte array
   * @param offset position in the array
   * @param val long to write out
   * @return incremented offset
   * @throws IllegalArgumentException if the byte array given doesn't have
   * enough room at the offset specified.
   */
  public static int putLong(byte[] bytes, int offset, long val) {
    if (bytes.length - offset < SIZEOF_LONG) {
      throw new IllegalArgumentException("Not enough room to put a long at"
          + " offset " + offset + " in a " + bytes.length + " byte array");
    }
    for (int i = offset + 7; i > offset; i--) {
      bytes[i] = (byte) val;
      val >>>= 8;
    }
    bytes[offset] = (byte) val;
    return offset + SIZEOF_LONG;
  }

  /**
   * Presumes float encoded as IEEE 754 floating-point "single format".
   * @param bytes byte array
   * @return Float made from passed byte array.
   */
  public static float toFloat(byte [] bytes) {
    return toFloat(bytes, 0);
  }

  /**
   * Presumes float encoded as IEEE 754 floating-point "single format".
   * @param bytes array to convert
   * @param offset offset into array
   * @return Float made from passed byte array.
   */
  public static float toFloat(byte [] bytes, int offset) {
    return Float.intBitsToFloat(toInt(bytes, offset, SIZEOF_INT));
  }

  /**
   * Put a float value out to the specified byte array position.
   * @param bytes byte array
   * @param offset offset to write to
   * @param f float value
   * @return New offset in <code>bytes</code>
   */
  public static int putFloat(byte [] bytes, int offset, float f) {
    return putInt(bytes, offset, Float.floatToRawIntBits(f));
  }

  /**
   * @param f float value
   * @return the float represented as byte []
   */
  public static byte [] toBytes(final float f) {
    // Encode it as int
    return Bytes.toBytes(Float.floatToRawIntBits(f));
  }

  /**
   * Return double made from passed bytes.
   * @param bytes byte array
   * @return Return double made from passed bytes.
   */
  public static double toDouble(final byte [] bytes) {
    return toDouble(bytes, 0);
  }

  /**
   * Return double made from passed bytes.
   * @param bytes byte array
   * @param offset offset where double is
   * @return Return double made from passed bytes.
   */
  public static double toDouble(final byte [] bytes, final int offset) {
    return Double.longBitsToDouble(toLong(bytes, offset, SIZEOF_LONG));
  }

  /**
   * Put a double value out to the specified byte array position.
   * @param bytes byte array
   * @param offset offset to write to
   * @param d value
   * @return New offset into array <code>bytes</code>
   */
  public static int putDouble(byte [] bytes, int offset, double d) {
    return putLong(bytes, offset, Double.doubleToLongBits(d));
  }

  /**
   * Serialize a double as the IEEE 754 double format output. The resultant
   * array will be 8 bytes long.
   *
   * @param d value
   * @return the double represented as byte []
   */
  public static byte [] toBytes(final double d) {
    // Encode it as a long
    return Bytes.toBytes(Double.doubleToRawLongBits(d));
  }

  /**
   * Convert an int value to a byte array.
   * @param val value
   * @return the byte array
   */
  public static byte[] toBytes(int val) {
    byte [] b = new byte[4];
    for (int i = 3; i > 0; i--) {
      b[i] = (byte) val;
      val >>>= 8;
    }
    b[0] = (byte) val;
    return b;
  }

  /**
   * Converts a byte array to an int value.
   * @param bytes byte array
   * @return the int value
   */
  public static int toInt(byte[] bytes) {
    return toInt(bytes, 0, SIZEOF_INT);
  }

  /**
   * Converts a byte array to an int value.
   * @param bytes byte array
   * @param offset offset into array
   * @return the int value
   */
  public static int toInt(byte[] bytes, int offset) {
    return toInt(bytes, offset, SIZEOF_INT);
  }

  /**
   * Converts a byte array to an int value.
   * @param bytes byte array
   * @param offset offset into array
   * @param length length of int (has to be {@link #SIZEOF_INT})
   * @return the int value
   * @throws IllegalArgumentException if length is not {@link #SIZEOF_INT} or
   * if there's not enough room in the array at the offset indicated.
   */
  public static int toInt(byte[] bytes, int offset, final int length) {
    if (length != SIZEOF_INT || offset + length > bytes.length) {
      throw explainWrongLengthOrOffset(bytes, offset, length, SIZEOF_INT);
    }
    int n = 0;
    for (int i = offset; i < (offset + length); i++) {
      n <<= 8;
      n ^= bytes[i] & 0xFF;
    }
    return n;
  }

  /**
   * Put an int value out to the specified byte array position.
   * @param bytes the byte array
   * @param offset position in the array
   * @param val int to write out
   * @return incremented offset
   * @throws IllegalArgumentException if the byte array given doesn't have
   * enough room at the offset specified.
   */
  public static int putInt(byte[] bytes, int offset, int val) {
    if (bytes.length - offset < SIZEOF_INT) {
      throw new IllegalArgumentException("Not enough room to put an int at"
          + " offset " + offset + " in a " + bytes.length + " byte array");
    }
    for (int i = offset + 3; i > offset; i--) {
      bytes[i] = (byte) val;
      val >>>= 8;
    }
    bytes[offset] = (byte) val;
    return offset + SIZEOF_INT;
  }

  /**
   * Convert a short value to a byte array of {@link #SIZEOF_SHORT} bytes long.
   * @param val value
   * @return the byte array
   */
  public static byte[] toBytes(short val) {
    byte[] b = new byte[SIZEOF_SHORT];
    b[1] = (byte) val;
    val >>= 8;
    b[0] = (byte) val;
    return b;
  }

  /**
   * Converts a byte array to a short value.
   * @param bytes byte array
   * @return the short value
   */
  public static short toShort(byte[] bytes) {
    return toShort(bytes, 0, SIZEOF_SHORT);
  }

  /**
   * Converts a byte array to a short value.
   * @param bytes byte array
   * @param offset offset into array
   * @return the short value
   */
  public static short toShort(byte[] bytes, int offset) {
    return toShort(bytes, offset, SIZEOF_SHORT);
  }

  /**
   * Converts a byte array to a short value.
   * @param bytes byte array
   * @param offset offset into array
   * @param length length, has to be {@link #SIZEOF_SHORT}
   * @return the short value
   * @throws IllegalArgumentException if length is not {@link #SIZEOF_SHORT}
   * or if there's not enough room in the array at the offset indicated.
   */
  public static short toShort(byte[] bytes, int offset, final int length) {
    if (length != SIZEOF_SHORT || offset + length > bytes.length) {
      throw explainWrongLengthOrOffset(bytes, offset, length, SIZEOF_SHORT);
    }
    short n = 0;
    n ^= bytes[offset] & 0xFF;
    n <<= 8;
    n ^= bytes[offset + 1] & 0xFF;
    return n;
  }

  /**
   * This method will get a sequence of bytes from pos -> limit,
   * but will restore pos after.
   * @param buf
   * @return byte array
   */
  public static byte[] getBytes(ByteBuffer buf) {
    int savedPos = buf.position();
    byte [] newBytes = new byte[buf.remaining()];
    buf.get(newBytes);
    buf.position(savedPos);
    return newBytes;
  }

  /**
   * Put a short value out to the specified byte array position.
   * @param bytes the byte array
   * @param offset position in the array
   * @param val short to write out
   * @return incremented offset
   * @throws IllegalArgumentException if the byte array given doesn't have
   * enough room at the offset specified.
   */
  public static int putShort(byte[] bytes, int offset, short val) {
    if (bytes.length - offset < SIZEOF_SHORT) {
      throw new IllegalArgumentException("Not enough room to put a short at"
          + " offset " + offset + " in a " + bytes.length + " byte array");
    }
    bytes[offset + 1] = (byte) val;
    val >>= 8;
    bytes[offset] = (byte) val;
    return offset + SIZEOF_SHORT;
  }

  /**
   * Convert a BigDecimal value to a byte array.
   *
   * @param val
   * @return the byte array
   */
  public static byte[] toBytes(BigDecimal val) {
    byte[] valueBytes = val.unscaledValue().toByteArray();
    byte[] result = new byte[valueBytes.length + SIZEOF_INT];
    int offset = putInt(result, 0, val.scale());
    putBytes(result, offset, valueBytes, 0, valueBytes.length);
    return result;
  }

  /**
   * Returns a copy of the byte representation of the given UUID.
   * @param uuid UUID to get the byte representation of
   * @return byte representation of the given UUID
   */
  public static byte[] toBytes(UUID uuid) {
    ByteBuffer bb = ByteBuffer.wrap(new byte[16]);
    bb.putLong(uuid.getMostSignificantBits());
    bb.putLong(uuid.getLeastSignificantBits());
    return bb.array();
  }

  /**
   * Convert the given byte representation of a UUID into a UUID.
   * @param bytes byte representation of a UUID
   * @return UUID
   */
  public static UUID toUUID(byte [] bytes) {
    ByteBuffer bb = ByteBuffer.wrap(bytes);
    return new UUID(bb.getLong(), bb.getLong());
  }

  /**
   * Converts a byte array to a BigDecimal.
   *
   * @param bytes
   * @return the char value
   */
  public static BigDecimal toBigDecimal(byte[] bytes) {
    return toBigDecimal(bytes, 0, bytes.length);
  }

  /**
   * Converts a byte array to a BigDecimal value.
   *
   * @param bytes
   * @param offset
   * @param length
   * @return the char value
   */
  public static BigDecimal toBigDecimal(byte[] bytes, int offset, final int length) {
    if (bytes == null || length < SIZEOF_INT + 1 ||
        (offset + length > bytes.length)) {
      return null;
    }

    int scale = toInt(bytes, offset);
    byte[] tcBytes = new byte[length - SIZEOF_INT];
    System.arraycopy(bytes, offset + SIZEOF_INT, tcBytes, 0, length - SIZEOF_INT);
    return new BigDecimal(new BigInteger(tcBytes), scale);
  }

  /**
   * Put a BigDecimal value out to the specified byte array position.
   *
   * @param bytes  the byte array
   * @param offset position in the array
   * @param val    BigDecimal to write out
   * @return incremented offset
   */
  public static int putBigDecimal(byte[] bytes, int offset, BigDecimal val) {
    if (bytes == null) {
      return offset;
    }

    byte[] valueBytes = val.unscaledValue().toByteArray();
    byte[] result = new byte[valueBytes.length + SIZEOF_INT];
    offset = putInt(result, offset, val.scale());
    return putBytes(result, offset, valueBytes, 0, valueBytes.length);
  }


  /**
   * Lexicographically compare two arrays.
   * @param left left operand
   * @param right right operand
   * @return 0 if equal, < 0 if left is less than right, etc.
   */
  public static int compareTo(final byte [] left, final byte [] right) {
    return LexicographicalComparerHolder.BEST_COMPARER.
        compareTo(left, 0, left.length, right, 0, right.length);
  }

  /**
   * Lexicographically compare two arrays.
   *
   * @param buffer1 left operand
   * @param buffer2 right operand
   * @param offset1 Where to start comparing in the left buffer
   * @param offset2 Where to start comparing in the right buffer
   * @param length1 How much to compare from the left buffer
   * @param length2 How much to compare from the right buffer
   * @return 0 if equal, < 0 if left is less than right, etc.
   */
  public static int compareTo(byte[] buffer1, int offset1, int length1,
      byte[] buffer2, int offset2, int length2) {
    return LexicographicalComparerHolder.BEST_COMPARER.
        compareTo(buffer1, offset1, length1, buffer2, offset2, length2);
  }

  interface Comparer<T> {
    int compareTo(T buffer1, int offset1, int length1,
        T buffer2, int offset2, int length2);
  }

  static Comparer<byte[]> lexicographicalComparerJavaImpl() {
    return LexicographicalComparerHolder.PureJavaComparer.INSTANCE;
  }
  static class LexicographicalComparerHolder {
    static final String UNSAFE_COMPARER_NAME =
        LexicographicalComparerHolder.class.getName() + "$UnsafeComparer";

    static final Comparer<byte[]> BEST_COMPARER = getBestComparer();
    /**
     * Returns the Unsafe-using Comparer, or falls back to the pure-Java
     * implementation if unable to do so.
     */
    static Comparer<byte[]> getBestComparer() {
      try {
        Class<?> theClass = Class.forName(UNSAFE_COMPARER_NAME);

        // yes, UnsafeComparer does implement Comparer<byte[]>
        @SuppressWarnings("unchecked")
        Comparer<byte[]> comparer =
        (Comparer<byte[]>) theClass.getEnumConstants()[0];
        return comparer;
      } catch (Throwable t) { // ensure we really catch *everything*
        return lexicographicalComparerJavaImpl();
      }
    }

    enum PureJavaComparer implements Comparer<byte[]> {
      INSTANCE;

      @Override
      public int compareTo(byte[] buffer1, int offset1, int length1,
          byte[] buffer2, int offset2, int length2) {
        // Short circuit equal case
        if (buffer1 == buffer2 &&
            offset1 == offset2 &&
            length1 == length2) {
          return 0;
        }
        // Bring WritableComparator code local
        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;
      }
    }
  }

  /**
   * Checks two byte arrays for equality.
   * @param left left operand
   * @param right right operand
   * @return True if equal
   */
  public static boolean equals(final byte [] left, final byte [] right) {
    // Could use Arrays.equals?
    //noinspection SimplifiableConditionalExpression
    if (left == right) {
      return true;
    }
    if (left == null || right == null) {
      return false;
    }
    if (left.length != right.length) {
      return false;
    }
    if (left.length == 0) {
      return true;
    }

    // Since we're often comparing adjacent sorted data,
    // it's usual to have equal arrays except for the very last byte
    // so check that first
    if (left[left.length - 1] != right[right.length - 1]) {
      return false;
    }

    return compareTo(left, right) == 0;
  }

  /**
   * Checks segments of two byte arrays for equality.
   * @param left left operand
   * @param leftOffset offset from which to start comparison
   * @param leftLen length of left segment
   * @param right right operand
   * @param rightOffset offset from which to start comparison
   * @param rightLen length of right segment
   * @return True if two segments are equal
   */
  public static boolean equals(final byte[] left, int leftOffset, int leftLen,
      final byte[] right, int rightOffset, int rightLen) {
    // short circuit case
    if (left == right &&
        leftOffset == rightOffset &&
        leftLen == rightLen) {
      return true;
    }
    // different lengths fast check
    if (leftLen != rightLen) {
      return false;
    }
    if (leftLen == 0) {
      return true;
    }

    // Since we're often comparing adjacent sorted data,
    // it's usual to have equal arrays except for the very last byte
    // so check that first
    if (left[leftOffset + leftLen - 1] != right[rightOffset + rightLen - 1]) {
      return false;
    }

    return LexicographicalComparerHolder.BEST_COMPARER.
        compareTo(left, leftOffset, leftLen, right, rightOffset, rightLen) == 0;
  }


  /**
   * Return true if the byte array on the right is a prefix of the byte
   * array on the left.
   */
  public static boolean startsWith(byte[] bytes, byte[] prefix) {
    return bytes != null && prefix != null &&
        bytes.length >= prefix.length &&
        LexicographicalComparerHolder.BEST_COMPARER.
        compareTo(bytes, 0, prefix.length, prefix, 0, prefix.length) == 0;
  }

  /**
   * Compute hash for binary data.
   * @param b bytes to hash
   * @return Runs {@link #hashBytes(byte[], int)} on the
   * passed in array.
   */
  public static int hashCode(final byte [] b) {
    return hashCode(b, b.length);
  }

  /**
   * Compute hash for binary data.
   * @param b value
   * @param length length of the value
   * @return Runs {@link #hashBytes(byte[], int)} on the
   * passed in array.
   */
  public static int hashCode(final byte [] b, final int length) {
    return hashBytes(b, length);
  }

  /** Compute hash for binary data. */
  public static int hashBytes(byte[] bytes, int offset, int length) {
    int hash = 1;
    for (int i = offset; i < offset + length; i++) {
      hash = (31 * hash) + bytes[i];
    }
    return hash;
  }

  /** Compute hash for binary data. */
  public static int hashBytes(byte[] bytes, int length) {
    return hashBytes(bytes, 0, length);
  }

  /**
   * Returns a hash of a byte array as an Integer that can be used as key in Maps.
   * @param b bytes to hash
   * @return A hash of <code>b</code> as an Integer that can be used as key in
   * Maps.
   */
  public static Integer mapKey(final byte [] b) {
    return hashCode(b);
  }

  /**
   * Returns a hash of a byte array segment as an Integer that can be used as key in Maps.
   * @param b bytes to hash
   * @param length length to hash
   * @return A hash of <code>b</code> as an Integer that can be used as key in
   * Maps.
   */
  public static Integer mapKey(final byte [] b, final int length) {
    return hashCode(b, length);
  }

  /**
   *  Byte array of size zero.
   */
  public static final byte [] EMPTY_BYTE_ARRAY = new byte [0];

  /**
   * Concatenate two byte arrays.
   * @param a lower half
   * @param b upper half
   * @return New array that has a in lower half and b in upper half.
   */
  public static byte [] add(final byte [] a, final byte [] b) {
    return add(a, b, EMPTY_BYTE_ARRAY);
  }

  /**
   * Concatenate three byte arrays.
   * @param a first third
   * @param b second third
   * @param c third third
   * @return New array made from a, b and c
   */
  public static byte [] add(final byte [] a, final byte [] b, final byte [] c) {
    byte [] result = new byte[a.length + b.length + c.length];
    System.arraycopy(a, 0, result, 0, a.length);
    System.arraycopy(b, 0, result, a.length, b.length);
    System.arraycopy(c, 0, result, a.length + b.length, c.length);
    return result;
  }

  /**
   * Returns the values from each provided array combined into a single array.
   * For example, {@code concat(new byte[] {a, b}, new byte[] {}, new
   * byte[] {c}} returns the array {@code {a, b, c}}. This method is copied from google guava library.
   *
   * @param arrays zero or more {@code byte} arrays
   * @return a single array containing all the values from the source arrays, in
   *         order
   */
  public static byte[] concat(byte[]... arrays) {
    int length = 0;
    for (byte[] array : arrays) {
      length += array.length;
    }
    byte[] result = new byte[length];
    int pos = 0;
    for (byte[] array : arrays) {
      System.arraycopy(array, 0, result, pos, array.length);
      pos += array.length;
    }
    return result;
  }

  /**
   * Returns first <code>length</code> bytes from byte array.
   * @param a array
   * @param length amount of bytes to grab
   * @return First <code>length</code> bytes from <code>a</code>
   */
  public static byte [] head(final byte [] a, final int length) {
    if (a.length < length) {
      return null;
    }
    byte [] result = new byte[length];
    System.arraycopy(a, 0, result, 0, length);
    return result;
  }

  /**
   * Returns last <code>length</code> bytes from byte array.
   * @param a array
   * @param length amount of bytes to snarf
   * @return Last <code>length</code> bytes from <code>a</code>
   */
  public static byte [] tail(final byte [] a, final int length) {
    if (a.length < length) {
      return null;
    }
    byte [] result = new byte[length];
    System.arraycopy(a, a.length - length, result, 0, length);
    return result;
  }

  /**
   * Return a byte array with value in <code>a</code> plus <code>length</code> prepended 0 bytes.
   * @param a array
   * @param length new array size
   * @return Value in <code>a</code> plus <code>length</code> prepended 0 bytes
   */
  public static byte [] padHead(final byte [] a, final int length) {
    byte [] padding = new byte[length];
    for (int i = 0; i < length; i++) {
      padding[i] = 0;
    }
    return add(padding, a);
  }

  /**
   * Return a byte array with value in <code>a</code> plus <code>length</code> appended 0 bytes.
   * @param a array
   * @param length new array size
   * @return Value in <code>a</code> plus <code>length</code> appended 0 bytes
   */
  public static byte [] padTail(final byte [] a, final int length) {
    byte [] padding = new byte[length];
    for (int i = 0; i < length; i++) {
      padding[i] = 0;
    }
    return add(a, padding);
  }

  /**
   * Split passed range.  Expensive operation relatively.  Uses BigInteger math.
   * Useful splitting ranges for MapReduce jobs.
   * @param a Beginning of range
   * @param b End of range
   * @param num Number of times to split range.  Pass 1 if you want to split
   * the range in two; i.e. one split.
   * @return Array of dividing values
   */
  public static byte [][] split(final byte [] a, final byte [] b, final int num) {
    return split(a, b, false, num);
  }

  /**
   * Split passed range.  Expensive operation relatively.  Uses BigInteger math.
   * Useful splitting ranges for MapReduce jobs.
   * @param a Beginning of range
   * @param b End of range
   * @param inclusive Whether the end of range is prefix-inclusive or is
   * considered an exclusive boundary.  Automatic splits are generally exclusive
   * and manual splits with an explicit range utilize an inclusive end of range.
   * @param num Number of times to split range.  Pass 1 if you want to split
   * the range in two; i.e. one split.
   * @return Array of dividing values
   */
  public static byte[][] split(final byte[] a, final byte[] b,
      boolean inclusive, final int num) {
    byte[][] ret = new byte[num + 2][];
    int i = 0;
    Iterable<byte[]> iter = iterateOnSplits(a, b, inclusive, num);
    if (iter == null) {
      return null;
    }
    for (byte[] elem : iter) {
      ret[i++] = elem;
    }
    return ret;
  }

  /**
   * Iterate over keys within the passed range, splitting at an [a,b) boundary.
   */
  public static Iterable<byte[]> iterateOnSplits(final byte[] a, final byte[] b, final int num) {
    return iterateOnSplits(a, b, false, num);
  }

  /**
   * Iterate over keys within the passed range.
   */
  public static Iterable<byte[]> iterateOnSplits(final byte[] a, final byte[]b, boolean inclusive, final int num) {
    byte [] aPadded;
    byte [] bPadded;
    if (a.length < b.length) {
      aPadded = padTail(a, b.length - a.length);
      bPadded = b;
    } else if (b.length < a.length) {
      aPadded = a;
      bPadded = padTail(b, a.length - b.length);
    } else {
      aPadded = a;
      bPadded = b;
    }
    if (compareTo(aPadded, bPadded) >= 0) {
      throw new IllegalArgumentException("b <= a");
    }
    if (num <= 0) {
      throw new IllegalArgumentException("num cannot be < 0");
    }
    byte [] prependHeader = {1, 0};
    final BigInteger startBI = new BigInteger(add(prependHeader, aPadded));
    final BigInteger stopBI = new BigInteger(add(prependHeader, bPadded));
    BigInteger diffBI = stopBI.subtract(startBI);
    if (inclusive) {
      diffBI = diffBI.add(BigInteger.ONE);
    }
    final BigInteger splitsBI = BigInteger.valueOf(num + 1);
    if (diffBI.compareTo(splitsBI) < 0) {
      return null;
    }
    final BigInteger intervalBI;
    try {
      intervalBI = diffBI.divide(splitsBI);
    } catch (Exception e) {
      return null;
    }

    final Iterator<byte[]> iterator = new Iterator<byte[]>() {
      private int i = -1;

      @Override
      public boolean hasNext() {
        return this.i < num + 1;
      }

      @Override
      public byte[] next() {
        this.i++;
        if (this.i == 0) {
          return a;
        }
        if (this.i == num + 1) {
          return b;
        }

        BigInteger curBI = startBI.add(intervalBI.multiply(BigInteger.valueOf(this.i)));
        byte [] padded = curBI.toByteArray();
        if (padded[1] == 0) {
          padded = tail(padded, padded.length - 2);
        } else {
          padded = tail(padded, padded.length - 1);
        }
        return padded;
      }

      @Override
      public void remove() {
        throw new UnsupportedOperationException();
      }

    };

    return new Iterable<byte[]>() {
      @Override
      public Iterator<byte[]> iterator() {
        return iterator;
      }
    };
      }

  /**
   * @param bytes array to hash
   * @param offset offset to start from
   * @param length length to hash
   * */
  public static int hashCode(byte[] bytes, int offset, int length) {
    int hash = 1;
    for (int i = offset; i < offset + length; i++) {
      hash = (31 * hash) + bytes[i];
    }
    return hash;
  }

  /**
   * Returns an array of byte arrays made from passed array of Text.
   * @param t operands
   * @return Array of byte arrays made from passed array of Text
   */
  public static byte [][] toByteArrays(final String [] t) {
    byte [][] result = new byte[t.length][];
    for (int i = 0; i < t.length; i++) {
      result[i] = Bytes.toBytes(t[i]);
    }
    return result;
  }

  /**
   * Returns an array of byte arrays where first and only entry is.
   * <code>column</code>
   * @param column operand
   * @return An array of byte arrays where first and only entry is
   * <code>column</code>
   */
  public static byte [][] toByteArrays(final String column) {
    return toByteArrays(toBytes(column));
  }

  /**
   * Returns an array of byte arrays  where first and only entry is.
   * <code>column</code>
   * @param column operand
   * @return An array of byte arrays  where first and only entry is
   * <code>column</code>
   */
  public static byte [][] toByteArrays(final byte [] column) {
    byte [][] result = new byte[1][];
    result[0] = column;
    return result;
  }

  /**
   * Bytewise binary increment/deincrement of long contained in byte array
   * on given amount.
   *
   * @param value - array of bytes containing long (length <= SIZEOF_LONG)
   * @param amount value will be incremented on (deincremented if negative)
   * @return array of bytes containing incremented long (length == SIZEOF_LONG)
   */
  public static byte [] incrementBytes(byte[] value, long amount) {
    byte[] val = value;
    if (val.length < SIZEOF_LONG) {
      // Hopefully this doesn't happen too often.
      byte [] newvalue;
      if (val[0] < 0) {
        newvalue = new byte[]{-1, -1, -1, -1, -1, -1, -1, -1};
      } else {
        newvalue = new byte[SIZEOF_LONG];
      }
      System.arraycopy(val, 0, newvalue, newvalue.length - val.length,
          val.length);
      val = newvalue;
    } else if (val.length > SIZEOF_LONG) {
      throw new IllegalArgumentException("Increment Bytes - value too big: " +
          val.length);
    }
    if (amount == 0) {
      return val;
    }
    if (val[0] < 0) {
      return binaryIncrementNeg(val, amount);
    }
    return binaryIncrementPos(val, amount);
  }

  /* increment/deincrement for positive value */
  private static byte [] binaryIncrementPos(byte [] value, long amount) {
    long amo = amount;
    int sign = 1;
    if (amount < 0) {
      amo = -amount;
      sign = -1;
    }
    for (int i = 0; i < value.length; i++) {
      int cur = ((int) amo % 256) * sign;
      amo = (amo >> 8);
      int val = value[value.length - i - 1] & 0x0ff;
      int total = val + cur;
      if (total > 255) {
        amo += sign;
        total %= 256;
      } else if (total < 0) {
        amo -= sign;
      }
      value[value.length - i - 1] = (byte) total;
      if (amo == 0) {
        return value;
      }
    }
    return value;
  }

  /* increment/deincrement for negative value */
  private static byte [] binaryIncrementNeg(byte [] value, long amount) {
    long amo = amount;
    int sign = 1;
    if (amount < 0) {
      amo = -amount;
      sign = -1;
    }
    for (int i = 0; i < value.length; i++) {
      int cur = ((int) amo % 256) * sign;
      amo = (amo >> 8);
      int val = ((~value[value.length - i - 1]) & 0x0ff) + 1;
      int total = cur - val;
      if (total >= 0) {
        amo += sign;
      } else if (total < -256) {
        amo -= sign;
        total %= 256;
      }
      value[value.length - i - 1] = (byte) total;
      if (amo == 0) {
        return value;
      }
    }
    return value;
  }

  /**
   * Writes a string as a fixed-size field, padded with zeros.
   */
  public static void writeStringFixedSize(final DataOutput out, String s,
      int size) throws IOException {
    byte[] b = toBytes(s);
    if (b.length > size) {
      throw new IOException("Trying to write " + b.length + " bytes (" +
          toStringBinary(b) + ") into a field of length " + size);
    }

    out.writeBytes(s);
    for (int i = 0; i < size - s.length(); ++i) {
      out.writeByte(0);
    }
  }

  /**
   * Returns the given prefix, incremented by one, in the form that will be suitable for prefix matching.
   * @param prefix the prefix to increment for the stop key
   * @return the stop key to use (may be null if the prefix cannot be incremented)
   */
  // NOTE: null means "read to the end"
  @Nullable
  public static byte[] stopKeyForPrefix(byte[] prefix) {
    for (int i = prefix.length - 1; i >= 0; i--) {
      int unsigned = prefix[i] & 0xff;
      if (unsigned < 0xff) {
        byte[] stopKey = Arrays.copyOf(prefix, i + 1);
        stopKey[stopKey.length - 1]++;
        return stopKey;
      }
    }

    // i.e. "read to the end"
    return null;
  }

  /**
   * Creates immutable sorted map with one entry with given key and value.
   * @param key key of the entry
   * @param value value of the entry
   * @return instance of {@link NavigableMap}
   *
   * @deprecated This method will be removed in future release
   */
  @Deprecated
  public static <T> NavigableMap<byte[], T> immutableSortedMapOf(byte[] key, T value) {
    // Not really immutable. However, for the sake of removing
    // guava usage and given this API is deprecated, it should be fine.
    TreeMap<byte[], T> result = new TreeMap<byte[], T>(BYTES_COMPARATOR);
    result.put(key, value);
    return result;
  }

  /**
   * Creates immutable sorted map with two entries with given keys and values.
   * @param key1 key of the first entry
   * @param value1 value of the first entry
   * @param key2 key of the second entry
   * @param value2 value of the second entry
   * @return instance of {@link NavigableMap}
   *
   * @deprecated This method will be removed in future release
   */
  @Deprecated
  public static <T> NavigableMap<byte[], T> immutableSortedMapOf(byte[] key1, T value1,
                                                                  byte[] key2, T value2) {
    // Not really immutable. However, for the sake of removing
    // guava usage and given this API is deprecated, it should be fine.
    TreeMap<byte[], T> result = new TreeMap<byte[], T>(BYTES_COMPARATOR);
    result.put(key1, value1);
    result.put(key2, value2);
    return result;
  }
}