/**
    * 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.hadoop.hbase.util;
  
  import static com.google.common.base.Preconditions.checkArgument;
  import static com.google.common.base.Preconditions.checkNotNull;
  import static com.google.common.base.Preconditions.checkPositionIndex;
  
  import java.io.DataInput;
  import java.io.DataOutput;
  import java.io.IOException;
  import java.math.BigDecimal;
  import java.math.BigInteger;
  import java.nio.ByteBuffer;
  import java.nio.ByteOrder;
  import java.nio.charset.Charset;
  import java.security.SecureRandom;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.Comparator;
  import java.util.Iterator;
  import java.util.List;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.Cell;
  import org.apache.hadoop.hbase.KeyValue;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.classification.InterfaceStability;
  import org.apache.hadoop.hbase.util.Bytes.LexicographicalComparerHolder.UnsafeComparer;
  import org.apache.hadoop.io.RawComparator;
  import org.apache.hadoop.io.WritableComparator;
  import org.apache.hadoop.io.WritableUtils;
  
  import com.google.common.annotations.VisibleForTesting;
  import com.google.common.collect.Lists;
  
  import sun.misc.Unsafe;
  
  /**
   * Utility class that handles byte arrays, conversions to/from other types,
   * comparisons, hash code generation, manufacturing keys for HashMaps or
   * HashSets, etc.
   */
  @SuppressWarnings("restriction")
  @InterfaceAudience.Public
  @InterfaceStability.Stable
  public class Bytes {
    //HConstants.UTF8_ENCODING should be updated if this changed
    /** When we encode strings, we always specify UTF8 encoding */
    private static final String UTF8_ENCODING = "UTF-8";
  
    //HConstants.UTF8_CHARSET should be updated if this changed
    /** When we encode strings, we always specify UTF8 encoding */
    private static final Charset UTF8_CHARSET = Charset.forName(UTF8_ENCODING);
  
    //HConstants.EMPTY_BYTE_ARRAY should be updated if this changed
    private static final byte [] EMPTY_BYTE_ARRAY = new byte [0];
  
    private static final Log LOG = LogFactory.getLog(Bytes.class);
  
    /**
     * 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;
 
   /**
    * Mask to apply to a long to reveal the lower int only. Use like this:
    * int i = (int)(0xFFFFFFFF00000000l ^ some_long_value);
    */
   public static final long MASK_FOR_LOWER_INT_IN_LONG = 0xFFFFFFFF00000000l;
 
   /**
    * Estimate of size cost to pay beyond payload in jvm for instance of byte [].
    * Estimate based on study of jhat and jprofiler numbers.
    */
   // JHat says BU is 56 bytes.
   // SizeOf which uses java.lang.instrument says 24 bytes. (3 longs?)
   public static final int ESTIMATED_HEAP_TAX = 16;
 
   private static final boolean UNSAFE_UNALIGNED = UnsafeAvailChecker.unaligned();
   
   /**
    * Returns length of the byte array, returning 0 if the array is null.
    * Useful for calculating sizes.
    * @param b byte array, which can be null
    * @return 0 if b is null, otherwise returns length
    */
   final public static int len(byte[] b) {
     return b == null ? 0 : b.length;
   }
 
   /**
    * Byte array comparator class.
    */
   @InterfaceAudience.Public
   @InterfaceStability.Stable
   public static class ByteArrayComparator implements RawComparator<byte []> {
     /**
      * Constructor
      */
     public ByteArrayComparator() {
       super();
     }
     @Override
     public int compare(byte [] left, byte [] right) {
       return compareTo(left, right);
     }
     @Override
     public int compare(byte [] b1, int s1, int l1, byte [] b2, int s2, int l2) {
       return LexicographicalComparerHolder.BEST_COMPARER.
         compareTo(b1, s1, l1, b2, s2, l2);
     }
   }
 
   /**
    * A {@link ByteArrayComparator} that treats the empty array as the largest value.
    * This is useful for comparing row end keys for regions.
    */
   // TODO: unfortunately, HBase uses byte[0] as both start and end keys for region
   // boundaries. Thus semantically, we should treat empty byte array as the smallest value
   // while comparing row keys, start keys etc; but as the largest value for comparing
   // region boundaries for endKeys.
   @InterfaceAudience.Public
   @InterfaceStability.Stable
   public static class RowEndKeyComparator extends ByteArrayComparator {
     @Override
     public int compare(byte[] left, byte[] right) {
       return compare(left, 0, left.length, right, 0, right.length);
     }
     @Override
     public int compare(byte[] b1, int s1, int l1, byte[] b2, int s2, int l2) {
       if (b1 == b2 && s1 == s2 && l1 == l2) {
         return 0;
       }
       if (l1 == 0) {
         return l2; //0 or positive
       }
       if (l2 == 0) {
         return -1;
       }
       return super.compare(b1, s1, l1, b2, s2, l2);
     }
   }
 
   /**
    * Pass this to TreeMaps where byte [] are keys.
    */
   public final static Comparator<byte []> BYTES_COMPARATOR = new ByteArrayComparator();
 
   /**
    * Use comparing byte arrays, byte-by-byte
    */
   public final static RawComparator<byte []> BYTES_RAWCOMPARATOR = new ByteArrayComparator();
 
   /**
    * Read byte-array written with a WritableableUtils.vint prefix.
    * @param in Input to read from.
    * @return byte array read off <code>in</code>
    * @throws IOException e
    */
   public static byte [] readByteArray(final DataInput in)
   throws IOException {
     int len = WritableUtils.readVInt(in);
     if (len < 0) {
       throw new NegativeArraySizeException(Integer.toString(len));
     }
     byte [] result = new byte[len];
     in.readFully(result, 0, len);
     return result;
   }
 
   /**
    * Read byte-array written with a WritableableUtils.vint prefix.
    * IOException is converted to a RuntimeException.
    * @param in Input to read from.
    * @return byte array read off <code>in</code>
    */
   public static byte [] readByteArrayThrowsRuntime(final DataInput in) {
     try {
       return readByteArray(in);
     } catch (Exception e) {
       throw new RuntimeException(e);
     }
   }
 
   /**
    * Write byte-array with a WritableableUtils.vint prefix.
    * @param out output stream to be written to
    * @param b array to write
    * @throws IOException e
    */
   public static void writeByteArray(final DataOutput out, final byte [] b)
   throws IOException {
     if(b == null) {
       WritableUtils.writeVInt(out, 0);
     } else {
       writeByteArray(out, b, 0, b.length);
     }
   }
 
   /**
    * Write byte-array to out with a vint length prefix.
    * @param out output stream
    * @param b array
    * @param offset offset into array
    * @param length length past offset
    * @throws IOException e
    */
   public static void writeByteArray(final DataOutput out, final byte [] b,
       final int offset, final int length)
   throws IOException {
     WritableUtils.writeVInt(out, length);
     out.write(b, offset, length);
   }
 
   /**
    * Write byte-array from src to tgt with a vint length prefix.
    * @param tgt target array
    * @param tgtOffset offset into target array
    * @param src source array
    * @param srcOffset source offset
    * @param srcLength source length
    * @return New offset in src array.
    */
   public static int writeByteArray(final byte [] tgt, final int tgtOffset,
       final byte [] src, final int srcOffset, final int srcLength) {
     byte [] vint = vintToBytes(srcLength);
     System.arraycopy(vint, 0, tgt, tgtOffset, vint.length);
     int offset = tgtOffset + vint.length;
     System.arraycopy(src, srcOffset, tgt, offset, srcLength);
     return offset + srcLength;
   }
 
   /**
    * 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;
   }
 
   /**
    * Add the whole content of the ByteBuffer to the bytes arrays. The ByteBuffer is modified.
    * @param bytes the byte array
    * @param offset position in the array
    * @param buf ByteBuffer to write out
    * @return incremented offset
    */
   public static int putByteBuffer(byte[] bytes, int offset, ByteBuffer buf) {
     int len = buf.remaining();
     buf.get(bytes, offset, len);
     return offset + len;
   }
 
   /**
    * Returns a new byte array, copied from the given {@code buf},
    * from the index 0 (inclusive) to the limit (exclusive),
    * regardless of the current position.
    * The position and the other index parameters are not changed.
    *
    * @param buf a byte buffer
    * @return the byte array
    * @see #getBytes(ByteBuffer)
    */
   public static byte[] toBytes(ByteBuffer buf) {
     ByteBuffer dup = buf.duplicate();
     dup.position(0);
     return readBytes(dup);
   }
 
   private static byte[] readBytes(ByteBuffer buf) {
     byte [] result = new byte[buf.remaining()];
     buf.get(result);
     return result;
   }
 
   /**
    * @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);
   }
   
   /**
    * This method will convert utf8 encoded bytes into a string. If the given byte array is null,
    * this method will return null.
    * @param b Presumed UTF-8 encoded byte array.
    * @param off offset into array
    * @return String made from <code>b</code> or null
    */
   public static String toString(final byte[] b, int off) {
     if (b == null) {
       return null;
     }
     int len = b.length - off;
     if (len <= 0) {
       return "";
     }
     return new String(b, off, len, UTF8_CHARSET);
   }
 
   /**
    * This method will convert utf8 encoded bytes into a string. If
    * the given byte array is null, this method will return null.
    *
    * @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 "";
     }
     return new String(b, off, len, UTF8_CHARSET);
   }
 
   /**
    * 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);
   }
 
   /**
    * Converts the given byte buffer to a printable representation,
    * from the index 0 (inclusive) to the limit (exclusive),
    * regardless of the current position.
    * The position and the other index parameters are not changed.
    *
    * @param buf a byte buffer
    * @return a string representation of the buffer's binary contents
    * @see #toBytes(ByteBuffer)
    * @see #getBytes(ByteBuffer)
    */
   public static String toStringBinary(ByteBuffer buf) {
     if (buf == null)
       return "null";
     if (buf.hasArray()) {
       return toStringBinary(buf.array(), buf.arrayOffset(), buf.limit());
     }
     return toStringBinary(toBytes(buf));
   }
 
   /**
    * 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();
     // 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 >= '0' && ch <= '9')
           || (ch >= 'A' && ch <= 'Z')
           || (ch >= 'a' && ch <= 'z')
           || " `~!@#$%^&*()-_=+[]{}|;:'\",.<>/?".indexOf(ch) >= 0 ) {
         result.append((char)ch);
       } else {
         result.append(String.format("\\x%02X", ch));
       }
     }
     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 let's 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 == '\\' && in.length() > i+1 && in.charAt(i+1) == 'x') {
         // 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) {
     return s.getBytes(UTF8_CHARSET);
   }
 
   /**
    * 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);
     }
     if (UNSAFE_UNALIGNED) {
       return toLongUnsafe(bytes, offset);
     } else {
       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");
     }
     if (UNSAFE_UNALIGNED) {
       return putLongUnsafe(bytes, offset, val);
     } else {
       for(int i = offset + 7; i > offset; i--) {
         bytes[i] = (byte) val;
         val >>>= 8;
       }
       bytes[offset] = (byte) val;
       return offset + SIZEOF_LONG;
     }
   }
 
   /**
    * Put a long value out to the specified byte array position (Unsafe).
    * @param bytes the byte array
    * @param offset position in the array
    * @param val long to write out
    * @return incremented offset
    */
   public static int putLongUnsafe(byte[] bytes, int offset, long val)
   {
     if (UnsafeComparer.littleEndian) {
       val = Long.reverseBytes(val);
     }
     UnsafeComparer.theUnsafe.putLong(bytes, (long) offset +
       UnsafeComparer.BYTE_ARRAY_BASE_OFFSET , 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));
   }
 
   /**
    * @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));
   }
 
   /**
    * @param bytes byte array
    * @return Return double made from passed bytes.
    */
   public static double toDouble(final byte [] bytes) {
     return toDouble(bytes, 0);
   }
 
   /**
    * @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));
   }
 
   /**
    * @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.  Big-endian.  Same as what DataOutputStream.writeInt
    * does.
    *
    * @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);
     }
     if (UNSAFE_UNALIGNED) {
       return toIntUnsafe(bytes, offset);
     } else {
       int n = 0;
       for(int i = offset; i < (offset + length); i++) {
         n <<= 8;
         n ^= bytes[i] & 0xFF;
       }
       return n;
     }
   }
 
   /**
    * Converts a byte array to an int value (Unsafe version)
    * @param bytes byte array
    * @param offset offset into array
    * @return the int value
    */
   public static int toIntUnsafe(byte[] bytes, int offset) {
     if (UnsafeComparer.littleEndian) {
       return Integer.reverseBytes(UnsafeComparer.theUnsafe.getInt(bytes,
         (long) offset + UnsafeComparer.BYTE_ARRAY_BASE_OFFSET));
     } else {
       return UnsafeComparer.theUnsafe.getInt(bytes,
         (long) offset + UnsafeComparer.BYTE_ARRAY_BASE_OFFSET);
     }
   }
 
   /**
    * Converts a byte array to an short value (Unsafe version)
    * @param bytes byte array
    * @param offset offset into array
    * @return the short value
    */
   public static short toShortUnsafe(byte[] bytes, int offset) {
     if (UnsafeComparer.littleEndian) {
       return Short.reverseBytes(UnsafeComparer.theUnsafe.getShort(bytes,
         (long) offset + UnsafeComparer.BYTE_ARRAY_BASE_OFFSET));
     } else {
       return UnsafeComparer.theUnsafe.getShort(bytes,
         (long) offset + UnsafeComparer.BYTE_ARRAY_BASE_OFFSET);
     }
   }
 
   /**
    * Converts a byte array to an long value (Unsafe version)
    * @param bytes byte array
    * @param offset offset into array
    * @return the long value
    */
   public static long toLongUnsafe(byte[] bytes, int offset) {
     if (UnsafeComparer.littleEndian) {
       return Long.reverseBytes(UnsafeComparer.theUnsafe.getLong(bytes,
         (long) offset + UnsafeComparer.BYTE_ARRAY_BASE_OFFSET));
     } else {
       return UnsafeComparer.theUnsafe.getLong(bytes,
         (long) offset + UnsafeComparer.BYTE_ARRAY_BASE_OFFSET);
     }
   }
 
   /**
    * Converts a byte array to an int value
    * @param bytes byte array
    * @param offset offset into array
    * @param length how many bytes should be considered for creating int
    * @return the int value
    * @throws IllegalArgumentException if there's not enough room in the array at the offset
    * indicated.
    */
   public static int readAsInt(byte[] bytes, int offset, final int length) {
     if (offset + length > bytes.length) {
       throw new IllegalArgumentException("offset (" + offset + ") + length (" + length
           + ") exceed the" + " capacity of the array: " + bytes.length);
     }
     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");
     }
     if (UNSAFE_UNALIGNED) {
       return putIntUnsafe(bytes, offset, val);
     } else {
       for(int i= offset + 3; i > offset; i--) {
         bytes[i] = (byte) val;
         val >>>= 8;
       }
       bytes[offset] = (byte) val;
       return offset + SIZEOF_INT;
     }
   }
 
   /**
    * Put an int value out to the specified byte array position (Unsafe).
    * @param bytes the byte array
    * @param offset position in the array
    * @param val int to write out
    * @return incremented offset
    */
   public static int putIntUnsafe(byte[] bytes, int offset, int val)
   {
     if (UnsafeComparer.littleEndian) {
       val = Integer.reverseBytes(val);
     }
     UnsafeComparer.theUnsafe.putInt(bytes, (long) offset +
       UnsafeComparer.BYTE_ARRAY_BASE_OFFSET , 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);
     }
     if (UNSAFE_UNALIGNED) {
       return toShortUnsafe(bytes, offset);
     } else {
       short n = 0;
       n ^= bytes[offset] & 0xFF;
       n <<= 8;
       n ^= bytes[offset+1] & 0xFF;
       return n;
    }
   }
 
   /**
    * Returns a new byte array, copied from the given {@code buf},
    * from the position (inclusive) to the limit (exclusive).
    * The position and the other index parameters are not changed.
    *
    * @param buf a byte buffer
    * @return the byte array
    * @see #toBytes(ByteBuffer)
    */
   public static byte[] getBytes(ByteBuffer buf) {
     return readBytes(buf.duplicate());
   }
 
   /**
    * 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");
     }
     if (UNSAFE_UNALIGNED) {
       return putShortUnsafe(bytes, offset, val);
     } else {
       bytes[offset+1] = (byte) val;
       val >>= 8;
       bytes[offset] = (byte) val;
       return offset + SIZEOF_SHORT;
     }
   }
 
   /**
    * Put a short value out to the specified byte array position (Unsafe).
    * @param bytes the byte array
    * @param offset position in the array
    * @param val short to write out
    * @return incremented offset
    */
   public static int putShortUnsafe(byte[] bytes, int offset, short val)
   {
     if (UnsafeComparer.littleEndian) {
       val = Short.reverseBytes(val);
     }
     UnsafeComparer.theUnsafe.putShort(bytes, (long) offset +
       UnsafeComparer.BYTE_ARRAY_BASE_OFFSET , val);
     return offset + SIZEOF_SHORT;
   }
 
   /**
    * Put an int value as short out to the specified byte array position. Only the lower 2 bytes of
    * the short will be put into the array. The caller of the API need to make sure they will not
    * loose the value by doing so. This is useful to store an unsigned short which is represented as
    * int in other parts.
    * @param bytes the byte array
    * @param offset position in the array
    * @param val value 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 putAsShort(byte[] bytes, int offset, int 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;
   }
 
 
   /**
    * 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);
   }
 
   /**
    * @param vint Integer to make a vint of.
    * @return Vint as bytes array.
    */
   public static byte [] vintToBytes(final long vint) {
     long i = vint;
     int size = WritableUtils.getVIntSize(i);
     byte [] result = new byte[size];
     int offset = 0;
     if (i >= -112 && i <= 127) {
       result[offset] = (byte) i;
       return result;
     }
 
     int len = -112;
     if (i < 0) {
       i ^= -1L; // take one's complement'
       len = -120;
     }
 
     long tmp = i;
     while (tmp != 0) {
       tmp = tmp >> 8;
       len--;
     }
 
     result[offset++] = (byte) len;
 
     len = (len < -120) ? -(len + 120) : -(len + 112);
 
     for (int idx = len; idx != 0; idx--) {
       int shiftbits = (idx - 1) * 8;
       long mask = 0xFFL << shiftbits;
       result[offset++] = (byte)((i & mask) >> shiftbits);
     }
     return result;
   }
 
   /**
    * @param buffer buffer to convert
    * @return vint bytes as an integer.
    */
   public static long bytesToVint(final byte [] buffer) {
     int offset = 0;
     byte firstByte = buffer[offset++];
     int len = WritableUtils.decodeVIntSize(firstByte);
     if (len == 1) {
       return firstByte;
     }
     long i = 0;
     for (int idx = 0; idx < len-1; idx++) {
       byte b = buffer[offset++];
       i = i << 8;
       i = i | (b & 0xFF);
     }
     return (WritableUtils.isNegativeVInt(firstByte) ? ~i : i);
   }
 
   /**
    * Reads a zero-compressed encoded long from input buffer and returns it.
    * @param buffer Binary array
    * @param offset Offset into array at which vint begins.
    * @throws java.io.IOException e
    * @return deserialized long from buffer.
    * @deprecated Use {@link #readAsVLong()} instead.
    */
   @Deprecated
   public static long readVLong(final byte [] buffer, final int offset)
   throws IOException {
     return readAsVLong(buffer, offset);
   }
 
   /**
    * Reads a zero-compressed encoded long from input buffer and returns it.
    * @param buffer Binary array
    * @param offset Offset into array at which vint begins.
    * @return deserialized long from buffer.
    */
   public static long readAsVLong(final byte [] buffer, final int offset) {
     byte firstByte = buffer[offset];
     int len = WritableUtils.decodeVIntSize(firstByte);
     if (len == 1) {
       return firstByte;
     }
     long i = 0;
     for (int idx = 0; idx < len-1; idx++) {
       byte b = buffer[offset + 1 + idx];
       i = i << 8;
       i = i | (b & 0xFF);
     }
     return (WritableUtils.isNegativeVInt(firstByte) ? ~i : i);
   }
 
   /**
    * @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
     );
   }
 
   @VisibleForTesting
   static Comparer<byte[]> lexicographicalComparerJavaImpl() {
     return LexicographicalComparerHolder.PureJavaComparer.INSTANCE;
   }
 
   /**
    * Provides a lexicographical comparer implementation; either a Java
    * implementation or a faster implementation based on {@link Unsafe}.
    *
    * <p>Uses reflection to gracefully fall back to the Java implementation if
    * {@code Unsafe} isn't available.
    */
   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;
       }
     }
 
     @VisibleForTesting
     enum UnsafeComparer implements Comparer<byte[]> {
       INSTANCE;
 
       static final Unsafe theUnsafe;
 
       /** The offset to the first element in a byte array. */
       static final int BYTE_ARRAY_BASE_OFFSET;
 
       static {
         if (UNSAFE_UNALIGNED) {
           theUnsafe = UnsafeAccess.theUnsafe;
         } else {
           // It doesn't matter what we throw;
           // it's swallowed in getBestComparer().
           throw new Error();
         }
 
         BYTE_ARRAY_BASE_OFFSET = theUnsafe.arrayBaseOffset(byte[].class);
 
         // sanity check - this should never fail
         if (theUnsafe.arrayIndexScale(byte[].class) != 1) {
           throw new AssertionError();
         }
       }
 
       static final boolean littleEndian =
         ByteOrder.nativeOrder().equals(ByteOrder.LITTLE_ENDIAN);
 
       /**
        * Returns true if x1 is less than x2, when both values are treated as
        * unsigned long.
        * Both values are passed as is read by Unsafe. When platform is Little Endian, have to
        * convert to corresponding Big Endian value and then do compare. We do all writes in
        * Big Endian format.
        */
       static boolean lessThanUnsignedLong(long x1, long x2) {
         if (littleEndian) {
           x1 = Long.reverseBytes(x1);
           x2 = Long.reverseBytes(x2);
         }
         return (x1 + Long.MIN_VALUE) < (x2 + Long.MIN_VALUE);
       }
 
       /**
        * Returns true if x1 is less than x2, when both values are treated as
        * unsigned int.
        * Both values are passed as is read by Unsafe. When platform is Little Endian, have to
        * convert to corresponding Big Endian value and then do compare. We do all writes in
        * Big Endian format.
        */
       static boolean lessThanUnsignedInt(int x1, int x2) {
         if (littleEndian) {
           x1 = Integer.reverseBytes(x1);
           x2 = Integer.reverseBytes(x2);
         }
         return (x1 & 0xffffffffL) < (x2 & 0xffffffffL);
       }
 
       /**
        * Returns true if x1 is less than x2, when both values are treated as
        * unsigned short.
        * Both values are passed as is read by Unsafe. When platform is Little Endian, have to
        * convert to corresponding Big Endian value and then do compare. We do all writes in
        * Big Endian format.
        */
       static boolean lessThanUnsignedShort(short x1, short x2) {
         if (littleEndian) {
           x1 = Short.reverseBytes(x1);
           x2 = Short.reverseBytes(x2);
         }
         return (x1 & 0xffff) < (x2 & 0xffff);
       }
 
       /**
        * 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.
        */
       @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;
         }
         final int minLength = Math.min(length1, length2);
         final int minWords = minLength / SIZEOF_LONG;
         final long offset1Adj = offset1 + BYTE_ARRAY_BASE_OFFSET;
         final long offset2Adj = offset2 + BYTE_ARRAY_BASE_OFFSET;
 
         /*
          * Compare 8 bytes at a time. Benchmarking shows comparing 8 bytes at a
          * time is no slower than comparing 4 bytes at a time even on 32-bit.
          * On the other hand, it is substantially faster on 64-bit.
          */
         // This is the end offset of long parts.
         int j = minWords << 3; // Same as minWords * SIZEOF_LONG
         for (int i = 0; i < j; i += SIZEOF_LONG) {
           long lw = theUnsafe.getLong(buffer1, offset1Adj + (long) i);
           long rw = theUnsafe.getLong(buffer2, offset2Adj + (long) i);
           long diff = lw ^ rw;
           if (diff != 0) {
               return lessThanUnsignedLong(lw, rw) ? -1 : 1;
           }
         }
         int offset = j;
 
         if (minLength - offset >= SIZEOF_INT) {
           int il = theUnsafe.getInt(buffer1, offset1Adj + offset);
           int ir = theUnsafe.getInt(buffer2, offset2Adj + offset);
           if (il != ir) {
             return lessThanUnsignedInt(il, ir) ? -1: 1;
           }
           offset += SIZEOF_INT;
         }
         if (minLength - offset >= SIZEOF_SHORT) {
           short sl = theUnsafe.getShort(buffer1, offset1Adj + offset);
           short sr = theUnsafe.getShort(buffer2, offset2Adj + offset);
           if (sl != sr) {
             return lessThanUnsignedShort(sl, sr) ? -1: 1;
           }
           offset += SIZEOF_SHORT;
         }
         if (minLength - offset == 1) {
           int a = (buffer1[(int)(offset1 + offset)] & 0xff);
           int b = (buffer2[(int)(offset2 + offset)] & 0xff);
           if (a != b) {
             return a - b;
           }
         }
         return length1 - length2;
       }
     }
   }
 
   /**
    * @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;
   }
 
   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;
   }
 
 
   /**
    * @param a left operand
    * @param buf right operand
    * @return True if equal
    */
   public static boolean equals(byte[] a, ByteBuffer buf) {
     if (a == null) return buf == null;
     if (buf == null) return false;
     if (a.length != buf.remaining()) return false;
 
     // Thou shalt not modify the original byte buffer in what should be read only operations.
     ByteBuffer b = buf.duplicate();
     for (byte anA : a) {
       if (anA != b.get()) {
         return false;
       }
     }
     return true;
   }
 
 
   /**
    * 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;
   }
 
   /**
    * @param b bytes to hash
    * @return Runs {@link WritableComparator#hashBytes(byte[], int)} on the
    * passed in array.  This method is what {@link org.apache.hadoop.io.Text} and
    * {@link org.apache.hadoop.hbase.io.ImmutableBytesWritable} use calculating hash code.
    */
   public static int hashCode(final byte [] b) {
     return hashCode(b, b.length);
   }
 
   /**
    * @param b value
    * @param length length of the value
    * @return Runs {@link WritableComparator#hashBytes(byte[], int)} on the
    * passed in array.  This method is what {@link org.apache.hadoop.io.Text} and
    * {@link org.apache.hadoop.hbase.io.ImmutableBytesWritable} use calculating hash code.
    */
   public static int hashCode(final byte [] b, final int length) {
     return WritableComparator.hashBytes(b, length);
   }
 
   /**
    * @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);
   }
 
   /**
    * @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);
   }
 
   /**
    * @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);
   }
 
   /**
    * @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;
   }
 
   /**
    * @param arrays all the arrays to concatenate together.
    * @return New array made from the concatenation of the given arrays.
    */
   public static byte [] add(final byte [][] arrays) {
     int length = 0;
     for (int i = 0; i < arrays.length; i++) {
       length += arrays[i].length;
     }
     byte [] result = new byte[length];
     int index = 0;
     for (int i = 0; i < arrays.length; i++) {
       System.arraycopy(arrays[i], 0, result, index, arrays[i].length);
       index += arrays[i].length;
     }
     return result;
   }
 
   /**
    * @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;
   }
 
   /**
    * @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;
   }
 
   /**
    * @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);
   }
 
   /**
    * @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);
     //when diffBI < splitBI, use an additional byte to increase diffBI
     if(diffBI.compareTo(splitsBI) < 0) {
       byte[] aPaddedAdditional = new byte[aPadded.length+1];
       byte[] bPaddedAdditional = new byte[bPadded.length+1];
       for (int i = 0; i < aPadded.length; i++){
         aPaddedAdditional[i] = aPadded[i];
       }
       for (int j = 0; j < bPadded.length; j++){
         bPaddedAdditional[j] = bPadded[j];
       }
       aPaddedAdditional[aPadded.length] = 0;
       bPaddedAdditional[bPadded.length] = 0;
       return iterateOnSplits(aPaddedAdditional, bPaddedAdditional, inclusive,  num);
     }
     final BigInteger intervalBI;
     try {
       intervalBI = diffBI.divide(splitsBI);
     } catch(Exception e) {
       LOG.error("Exception caught during division", e);
       return null;
     }
 
     final Iterator<byte[]> iterator = new Iterator<byte[]>() {
       private int i = -1;
 
       @Override
       public boolean hasNext() {
         return i < num+1;
       }
 
       @Override
       public byte[] next() {
         i++;
         if (i == 0) return a;
         if (i == num + 1) return b;
 
         BigInteger curBI = startBI.add(intervalBI.multiply(BigInteger.valueOf(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) + (int) bytes[i];
     return hash;
   }
 
   /**
    * @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;
   }
 
   /**
    * @param t operands
    * @return Array of binary byte arrays made from passed array of binary strings
    */
   public static byte[][] toBinaryByteArrays(final String[] t) {
     byte[][] result = new byte[t.length][];
     for (int i = 0; i < t.length; i++) {
       result[i] = Bytes.toBytesBinary(t[i]);
     }
     return result;
   }
 
   /**
    * @param column operand
    * @return A byte array of a byte array where first and only entry is
    * <code>column</code>
    */
   public static byte [][] toByteArrays(final String column) {
     return toByteArrays(toBytes(column));
   }
 
   /**
    * @param column operand
    * @return A byte array of a byte array 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;
   }
 
   /**
    * Binary search for keys in indexes.
    *
    * @param arr array of byte arrays to search for
    * @param key the key you want to find
    * @param offset the offset in the key you want to find
    * @param length the length of the key
    * @param comparator a comparator to compare.
    * @return zero-based index of the key, if the key is present in the array.
    *         Otherwise, a value -(i + 1) such that the key is between arr[i -
    *         1] and arr[i] non-inclusively, where i is in [0, i], if we define
    *         arr[-1] = -Inf and arr[N] = Inf for an N-element array. The above
    *         means that this function can return 2N + 1 different values
    *         ranging from -(N + 1) to N - 1.
    */
   public static int binarySearch(byte [][]arr, byte []key, int offset,
       int length, RawComparator<?> comparator) {
     int low = 0;
     int high = arr.length - 1;
 
     while (low <= high) {
       int mid = (low+high) >>> 1;
       // we have to compare in this order, because the comparator order
       // has special logic when the 'left side' is a special key.
       int cmp = comparator.compare(key, offset, length,
           arr[mid], 0, arr[mid].length);
       // key lives above the midpoint
       if (cmp > 0)
         low = mid + 1;
       // key lives below the midpoint
       else if (cmp < 0)
         high = mid - 1;
       // BAM. how often does this really happen?
       else
         return mid;
     }
     return - (low+1);
   }
 
   /**
    * Binary search for keys in indexes.
    *
    * @param arr array of byte arrays to search for
    * @param key the key you want to find
    * @param comparator a comparator to compare.
    * @return zero-based index of the key, if the key is present in the array.
    *         Otherwise, a value -(i + 1) such that the key is between arr[i -
    *         1] and arr[i] non-inclusively, where i is in [0, i], if we define
    *         arr[-1] = -Inf and arr[N] = Inf for an N-element array. The above
    *         means that this function can return 2N + 1 different values
    *         ranging from -(N + 1) to N - 1.
    * @return the index of the block
    */
   public static int binarySearch(byte[][] arr, Cell key, RawComparator<Cell> comparator) {
     int low = 0;
     int high = arr.length - 1;
     KeyValue.KeyOnlyKeyValue r = new KeyValue.KeyOnlyKeyValue();
     while (low <= high) {
       int mid = (low+high) >>> 1;
       // we have to compare in this order, because the comparator order
       // has special logic when the 'left side' is a special key.
       r.setKey(arr[mid], 0, arr[mid].length);
       int cmp = comparator.compare(key, r);
       // key lives above the midpoint
       if (cmp > 0)
         low = mid + 1;
       // key lives below the midpoint
       else if (cmp < 0)
         high = mid - 1;
       // BAM. how often does this really happen?
       else
         return mid;
     }
     return - (low+1);
   }
 
   /**
    * 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);
   }
 
   /**
    * Reads a fixed-size field and interprets it as a string padded with zeros.
    */
   public static String readStringFixedSize(final DataInput in, int size)
       throws IOException {
     byte[] b = new byte[size];
     in.readFully(b);
     int n = b.length;
     while (n > 0 && b[n - 1] == 0)
       --n;
 
     return toString(b, 0, n);
   }
 
   /**
    * Copy the byte array given in parameter and return an instance
    * of a new byte array with the same length and the same content.
    * @param bytes the byte array to duplicate
    * @return a copy of the given byte array
    */
   public static byte [] copy(byte [] bytes) {
     if (bytes == null) return null;
     byte [] result = new byte[bytes.length];
     System.arraycopy(bytes, 0, result, 0, bytes.length);
     return result;
   }
 
   /**
    * Copy the byte array given in parameter and return an instance
    * of a new byte array with the same length and the same content.
    * @param bytes the byte array to copy from
    * @return a copy of the given designated byte array
    * @param offset
    * @param length
    */
   public static byte [] copy(byte [] bytes, final int offset, final int length) {
     if (bytes == null) return null;
     byte [] result = new byte[length];
     System.arraycopy(bytes, offset, result, 0, length);
     return result;
   }
 
   /**
    * Search sorted array "a" for byte "key". I can't remember if I wrote this or copied it from
    * somewhere. (mcorgan)
    * @param a Array to search. Entries must be sorted and unique.
    * @param fromIndex First index inclusive of "a" to include in the search.
    * @param toIndex Last index exclusive of "a" to include in the search.
    * @param key The byte to search for.
    * @return The index of key if found. If not found, return -(index + 1), where negative indicates
    *         "not found" and the "index + 1" handles the "-0" case.
    */
   public static int unsignedBinarySearch(byte[] a, int fromIndex, int toIndex, byte key) {
     int unsignedKey = key & 0xff;
     int low = fromIndex;
     int high = toIndex - 1;
 
     while (low <= high) {
       int mid = (low + high) >>> 1;
       int midVal = a[mid] & 0xff;
 
       if (midVal < unsignedKey) {
         low = mid + 1;
       } else if (midVal > unsignedKey) {
         high = mid - 1;
       } else {
         return mid; // key found
       }
     }
     return -(low + 1); // key not found.
   }
 
   /**
    * Treat the byte[] as an unsigned series of bytes, most significant bits first.  Start by adding
    * 1 to the rightmost bit/byte and carry over all overflows to the more significant bits/bytes.
    *
    * @param input The byte[] to increment.
    * @return The incremented copy of "in".  May be same length or 1 byte longer.
    */
   public static byte[] unsignedCopyAndIncrement(final byte[] input) {
     byte[] copy = copy(input);
     if (copy == null) {
       throw new IllegalArgumentException("cannot increment null array");
     }
     for (int i = copy.length - 1; i >= 0; --i) {
       if (copy[i] == -1) {// -1 is all 1-bits, which is the unsigned maximum
         copy[i] = 0;
       } else {
         ++copy[i];
         return copy;
       }
     }
     // we maxed out the array
     byte[] out = new byte[copy.length + 1];
     out[0] = 1;
     System.arraycopy(copy, 0, out, 1, copy.length);
     return out;
   }
 
   public static boolean equals(List<byte[]> a, List<byte[]> b) {
     if (a == null) {
       if (b == null) {
         return true;
       }
       return false;
     }
     if (b == null) {
       return false;
     }
     if (a.size() != b.size()) {
       return false;
     }
     for (int i = 0; i < a.size(); ++i) {
       if (!Bytes.equals(a.get(i), b.get(i))) {
         return false;
       }
     }
     return true;
   }
 
   public static boolean isSorted(Collection<byte[]> arrays) {
     byte[] previous = new byte[0];
     for (byte[] array : IterableUtils.nullSafe(arrays)) {
       if (Bytes.compareTo(previous, array) > 0) {
         return false;
       }
       previous = array;
     }
     return true;
   }
 
   public static List<byte[]> getUtf8ByteArrays(List<String> strings) {
     List<byte[]> byteArrays = Lists.newArrayListWithCapacity(CollectionUtils.nullSafeSize(strings));
     for (String s : IterableUtils.nullSafe(strings)) {
       byteArrays.add(Bytes.toBytes(s));
     }
     return byteArrays;
   }
 
   /**
    * Returns the index of the first appearance of the value {@code target} in
    * {@code array}.
    *
    * @param array an array of {@code byte} values, possibly empty
    * @param target a primitive {@code byte} value
    * @return the least index {@code i} for which {@code array[i] == target}, or
    *     {@code -1} if no such index exists.
    */
   public static int indexOf(byte[] array, byte target) {
     for (int i = 0; i < array.length; i++) {
       if (array[i] == target) {
         return i;
       }
     }
     return -1;
   }
 
   /**
    * Returns the start position of the first occurrence of the specified {@code
    * target} within {@code array}, or {@code -1} if there is no such occurrence.
    *
    * <p>More formally, returns the lowest index {@code i} such that {@code
    * java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly
    * the same elements as {@code target}.
    *
    * @param array the array to search for the sequence {@code target}
    * @param target the array to search for as a sub-sequence of {@code array}
    */
   public static int indexOf(byte[] array, byte[] target) {
     checkNotNull(array, "array");
     checkNotNull(target, "target");
     if (target.length == 0) {
       return 0;
     }
 
     outer:
     for (int i = 0; i < array.length - target.length + 1; i++) {
       for (int j = 0; j < target.length; j++) {
         if (array[i + j] != target[j]) {
           continue outer;
         }
       }
       return i;
     }
     return -1;
   }
 
   /**
    * @param array an array of {@code byte} values, possibly empty
    * @param target a primitive {@code byte} value
    * @return {@code true} if {@code target} is present as an element anywhere in {@code array}.
    */
   public static boolean contains(byte[] array, byte target) {
     return indexOf(array, target) > -1;
   }
 
   /**
    * @param array an array of {@code byte} values, possibly empty
    * @param target an array of {@code byte}
    * @return {@code true} if {@code target} is present anywhere in {@code array}
    */
   public static boolean contains(byte[] array, byte[] target) {
     return indexOf(array, target) > -1;
   }
 
   /**
    * Fill given array with zeros.
    * @param b array which needs to be filled with zeros
    */
   public static void zero(byte[] b) {
     zero(b, 0, b.length);
   }
 
   /**
    * Fill given array with zeros at the specified position.
    * @param b
    * @param offset
    * @param length
    */
   public static void zero(byte[] b, int offset, int length) {
     checkPositionIndex(offset, b.length, "offset");
     checkArgument(length > 0, "length must be greater than 0");
     checkPositionIndex(offset + length, b.length, "offset + length");
     Arrays.fill(b, offset, offset + length, (byte) 0);
   }
 
   private static final SecureRandom RNG = new SecureRandom();
 
   /**
    * Fill given array with random bytes.
    * @param b array which needs to be filled with random bytes
    */
   public static void random(byte[] b) {
     RNG.nextBytes(b);
   }
 
   /**
    * Fill given array with random bytes at the specified position.
    * @param b
    * @param offset
    * @param length
    */
   public static void random(byte[] b, int offset, int length) {
     checkPositionIndex(offset, b.length, "offset");
     checkArgument(length > 0, "length must be greater than 0");
     checkPositionIndex(offset + length, b.length, "offset + length");
     byte[] buf = new byte[length];
     RNG.nextBytes(buf);
     System.arraycopy(buf, 0, b, offset, length);
   }
 
   /**
    * Create a max byte array with the specified max byte count
    * @param maxByteCount the length of returned byte array
    * @return the created max byte array
    */
   public static byte[] createMaxByteArray(int maxByteCount) {
     byte[] maxByteArray = new byte[maxByteCount];
     for (int i = 0; i < maxByteArray.length; i++) {
       maxByteArray[i] = (byte) 0xff;
     }
     return maxByteArray;
   }
 
   /**
    * Create a byte array which is multiple given bytes
    * @param srcBytes
    * @param multiNum
    * @return byte array
    */
   public static byte[] multiple(byte[] srcBytes, int multiNum) {
     if (multiNum <= 0) {
       return new byte[0];
     }
     byte[] result = new byte[srcBytes.length * multiNum];
     for (int i = 0; i < multiNum; i++) {
       System.arraycopy(srcBytes, 0, result, i * srcBytes.length,
         srcBytes.length);
     }
     return result;
   }
   
   /**
    * Convert a byte array into a hex string
    * @param b
    */
   public static String toHex(byte[] b) {
     checkArgument(b.length > 0, "length must be greater than 0");
     return String.format("%x", new BigInteger(1, b));
   }
 
   /**
    * Create a byte array from a string of hash digits. The length of the
    * string must be a multiple of 2
    * @param hex
    */
   public static byte[] fromHex(String hex) {
     checkArgument(hex.length() > 0, "length must be greater than 0");
     checkArgument(hex.length() % 2 == 0, "length must be a multiple of 2");
     // Make sure letters are upper case
     hex = hex.toUpperCase();
     byte[] b = new byte[hex.length() / 2];
     for (int i = 0; i < b.length; i++) {
       b[i] = (byte)((toBinaryFromHex((byte)hex.charAt(2 * i)) << 4) +
         toBinaryFromHex((byte)hex.charAt((2 * i + 1))));
     }
     return b;
   }
 
 }