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1   /**
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *     http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  package org.apache.hadoop.hbase.util;
19  
20  import static com.google.common.base.Preconditions.checkArgument;
21  import static com.google.common.base.Preconditions.checkNotNull;
22  import static com.google.common.base.Preconditions.checkPositionIndex;
23  
24  import java.io.DataInput;
25  import java.io.DataOutput;
26  import java.io.IOException;
27  import java.lang.reflect.Field;
28  import java.math.BigDecimal;
29  import java.math.BigInteger;
30  import java.nio.ByteBuffer;
31  import java.nio.ByteOrder;
32  import java.nio.charset.Charset;
33  import java.security.AccessController;
34  import java.security.PrivilegedAction;
35  import java.security.SecureRandom;
36  import java.util.Arrays;
37  import java.util.Collection;
38  import java.util.Comparator;
39  import java.util.Iterator;
40  import java.util.List;
41  
42  import org.apache.commons.logging.Log;
43  import org.apache.commons.logging.LogFactory;
44  import org.apache.hadoop.hbase.classification.InterfaceAudience;
45  import org.apache.hadoop.hbase.classification.InterfaceStability;
46  import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
47  import org.apache.hadoop.io.RawComparator;
48  import org.apache.hadoop.io.WritableComparator;
49  import org.apache.hadoop.io.WritableUtils;
50  
51  import sun.misc.Unsafe;
52  
53  import com.google.common.annotations.VisibleForTesting;
54  import com.google.common.collect.Lists;
55  import org.apache.hadoop.hbase.util.Bytes.LexicographicalComparerHolder.UnsafeComparer;
56  
57  /**
58   * Utility class that handles byte arrays, conversions to/from other types,
59   * comparisons, hash code generation, manufacturing keys for HashMaps or
60   * HashSets, etc.
61   */
62  @InterfaceAudience.Public
63  @InterfaceStability.Stable
64  public class Bytes {
65    //HConstants.UTF8_ENCODING should be updated if this changed
66    /** When we encode strings, we always specify UTF8 encoding */
67    private static final String UTF8_ENCODING = "UTF-8";
68  
69    //HConstants.UTF8_CHARSET should be updated if this changed
70    /** When we encode strings, we always specify UTF8 encoding */
71    private static final Charset UTF8_CHARSET = Charset.forName(UTF8_ENCODING);
72  
73    //HConstants.EMPTY_BYTE_ARRAY should be updated if this changed
74    private static final byte [] EMPTY_BYTE_ARRAY = new byte [0];
75  
76    private static final Log LOG = LogFactory.getLog(Bytes.class);
77  
78    /**
79     * Size of boolean in bytes
80     */
81    public static final int SIZEOF_BOOLEAN = Byte.SIZE / Byte.SIZE;
82  
83    /**
84     * Size of byte in bytes
85     */
86    public static final int SIZEOF_BYTE = SIZEOF_BOOLEAN;
87  
88    /**
89     * Size of char in bytes
90     */
91    public static final int SIZEOF_CHAR = Character.SIZE / Byte.SIZE;
92  
93    /**
94     * Size of double in bytes
95     */
96    public static final int SIZEOF_DOUBLE = Double.SIZE / Byte.SIZE;
97  
98    /**
99     * Size of float in bytes
100    */
101   public static final int SIZEOF_FLOAT = Float.SIZE / Byte.SIZE;
102 
103   /**
104    * Size of int in bytes
105    */
106   public static final int SIZEOF_INT = Integer.SIZE / Byte.SIZE;
107 
108   /**
109    * Size of long in bytes
110    */
111   public static final int SIZEOF_LONG = Long.SIZE / Byte.SIZE;
112 
113   /**
114    * Size of short in bytes
115    */
116   public static final int SIZEOF_SHORT = Short.SIZE / Byte.SIZE;
117 
118 
119   /**
120    * Estimate of size cost to pay beyond payload in jvm for instance of byte [].
121    * Estimate based on study of jhat and jprofiler numbers.
122    */
123   // JHat says BU is 56 bytes.
124   // SizeOf which uses java.lang.instrument says 24 bytes. (3 longs?)
125   public static final int ESTIMATED_HEAP_TAX = 16;
126 
127   
128   /**
129    * Returns length of the byte array, returning 0 if the array is null.
130    * Useful for calculating sizes.
131    * @param b byte array, which can be null
132    * @return 0 if b is null, otherwise returns length
133    */
134   final public static int len(byte[] b) {
135     return b == null ? 0 : b.length;
136   }
137 
138   /**
139    * Byte array comparator class.
140    */
141   @InterfaceAudience.Public
142   @InterfaceStability.Stable
143   public static class ByteArrayComparator implements RawComparator<byte []> {
144     /**
145      * Constructor
146      */
147     public ByteArrayComparator() {
148       super();
149     }
150     @Override
151     public int compare(byte [] left, byte [] right) {
152       return compareTo(left, right);
153     }
154     @Override
155     public int compare(byte [] b1, int s1, int l1, byte [] b2, int s2, int l2) {
156       return LexicographicalComparerHolder.BEST_COMPARER.
157         compareTo(b1, s1, l1, b2, s2, l2);
158     }
159   }
160 
161   /**
162    * A {@link ByteArrayComparator} that treats the empty array as the largest value.
163    * This is useful for comparing row end keys for regions.
164    */
165   // TODO: unfortunately, HBase uses byte[0] as both start and end keys for region
166   // boundaries. Thus semantically, we should treat empty byte array as the smallest value
167   // while comparing row keys, start keys etc; but as the largest value for comparing
168   // region boundaries for endKeys.
169   @InterfaceAudience.Public
170   @InterfaceStability.Stable
171   public static class RowEndKeyComparator extends ByteArrayComparator {
172     @Override
173     public int compare(byte[] left, byte[] right) {
174       return compare(left, 0, left.length, right, 0, right.length);
175     }
176     @Override
177     public int compare(byte[] b1, int s1, int l1, byte[] b2, int s2, int l2) {
178       if (b1 == b2 && s1 == s2 && l1 == l2) {
179         return 0;
180       }
181       if (l1 == 0) {
182         return l2; //0 or positive
183       }
184       if (l2 == 0) {
185         return -1;
186       }
187       return super.compare(b1, s1, l1, b2, s2, l2);
188     }
189   }
190 
191   /**
192    * Pass this to TreeMaps where byte [] are keys.
193    */
194   public final static Comparator<byte []> BYTES_COMPARATOR = new ByteArrayComparator();
195 
196   /**
197    * Use comparing byte arrays, byte-by-byte
198    */
199   public final static RawComparator<byte []> BYTES_RAWCOMPARATOR = new ByteArrayComparator();
200 
201   /**
202    * Read byte-array written with a WritableableUtils.vint prefix.
203    * @param in Input to read from.
204    * @return byte array read off <code>in</code>
205    * @throws IOException e
206    */
207   public static byte [] readByteArray(final DataInput in)
208   throws IOException {
209     int len = WritableUtils.readVInt(in);
210     if (len < 0) {
211       throw new NegativeArraySizeException(Integer.toString(len));
212     }
213     byte [] result = new byte[len];
214     in.readFully(result, 0, len);
215     return result;
216   }
217 
218   /**
219    * Read byte-array written with a WritableableUtils.vint prefix.
220    * IOException is converted to a RuntimeException.
221    * @param in Input to read from.
222    * @return byte array read off <code>in</code>
223    */
224   public static byte [] readByteArrayThrowsRuntime(final DataInput in) {
225     try {
226       return readByteArray(in);
227     } catch (Exception e) {
228       throw new RuntimeException(e);
229     }
230   }
231 
232   /**
233    * Write byte-array with a WritableableUtils.vint prefix.
234    * @param out output stream to be written to
235    * @param b array to write
236    * @throws IOException e
237    */
238   public static void writeByteArray(final DataOutput out, final byte [] b)
239   throws IOException {
240     if(b == null) {
241       WritableUtils.writeVInt(out, 0);
242     } else {
243       writeByteArray(out, b, 0, b.length);
244     }
245   }
246 
247   /**
248    * Write byte-array to out with a vint length prefix.
249    * @param out output stream
250    * @param b array
251    * @param offset offset into array
252    * @param length length past offset
253    * @throws IOException e
254    */
255   public static void writeByteArray(final DataOutput out, final byte [] b,
256       final int offset, final int length)
257   throws IOException {
258     WritableUtils.writeVInt(out, length);
259     out.write(b, offset, length);
260   }
261 
262   /**
263    * Write byte-array from src to tgt with a vint length prefix.
264    * @param tgt target array
265    * @param tgtOffset offset into target array
266    * @param src source array
267    * @param srcOffset source offset
268    * @param srcLength source length
269    * @return New offset in src array.
270    */
271   public static int writeByteArray(final byte [] tgt, final int tgtOffset,
272       final byte [] src, final int srcOffset, final int srcLength) {
273     byte [] vint = vintToBytes(srcLength);
274     System.arraycopy(vint, 0, tgt, tgtOffset, vint.length);
275     int offset = tgtOffset + vint.length;
276     System.arraycopy(src, srcOffset, tgt, offset, srcLength);
277     return offset + srcLength;
278   }
279 
280   /**
281    * Put bytes at the specified byte array position.
282    * @param tgtBytes the byte array
283    * @param tgtOffset position in the array
284    * @param srcBytes array to write out
285    * @param srcOffset source offset
286    * @param srcLength source length
287    * @return incremented offset
288    */
289   public static int putBytes(byte[] tgtBytes, int tgtOffset, byte[] srcBytes,
290       int srcOffset, int srcLength) {
291     System.arraycopy(srcBytes, srcOffset, tgtBytes, tgtOffset, srcLength);
292     return tgtOffset + srcLength;
293   }
294 
295   /**
296    * Write a single byte out to the specified byte array position.
297    * @param bytes the byte array
298    * @param offset position in the array
299    * @param b byte to write out
300    * @return incremented offset
301    */
302   public static int putByte(byte[] bytes, int offset, byte b) {
303     bytes[offset] = b;
304     return offset + 1;
305   }
306 
307   /**
308    * Add the whole content of the ByteBuffer to the bytes arrays. The ByteBuffer is modified.
309    * @param bytes the byte array
310    * @param offset position in the array
311    * @param buf ByteBuffer to write out
312    * @return incremented offset
313    */
314   public static int putByteBuffer(byte[] bytes, int offset, ByteBuffer buf) {
315     int len = buf.remaining();
316     buf.get(bytes, offset, len);
317     return offset + len;
318   }
319 
320   /**
321    * Returns a new byte array, copied from the given {@code buf},
322    * from the index 0 (inclusive) to the limit (exclusive),
323    * regardless of the current position.
324    * The position and the other index parameters are not changed.
325    *
326    * @param buf a byte buffer
327    * @return the byte array
328    * @see #getBytes(ByteBuffer)
329    */
330   public static byte[] toBytes(ByteBuffer buf) {
331     ByteBuffer dup = buf.duplicate();
332     dup.position(0);
333     return readBytes(dup);
334   }
335 
336   private static byte[] readBytes(ByteBuffer buf) {
337     byte [] result = new byte[buf.remaining()];
338     buf.get(result);
339     return result;
340   }
341 
342   /**
343    * @param b Presumed UTF-8 encoded byte array.
344    * @return String made from <code>b</code>
345    */
346   public static String toString(final byte [] b) {
347     if (b == null) {
348       return null;
349     }
350     return toString(b, 0, b.length);
351   }
352 
353   /**
354    * Joins two byte arrays together using a separator.
355    * @param b1 The first byte array.
356    * @param sep The separator to use.
357    * @param b2 The second byte array.
358    */
359   public static String toString(final byte [] b1,
360                                 String sep,
361                                 final byte [] b2) {
362     return toString(b1, 0, b1.length) + sep + toString(b2, 0, b2.length);
363   }
364 
365   /**
366    * This method will convert utf8 encoded bytes into a string. If
367    * the given byte array is null, this method will return null.
368    *
369    * @param b Presumed UTF-8 encoded byte array.
370    * @param off offset into array
371    * @param len length of utf-8 sequence
372    * @return String made from <code>b</code> or null
373    */
374   public static String toString(final byte [] b, int off, int len) {
375     if (b == null) {
376       return null;
377     }
378     if (len == 0) {
379       return "";
380     }
381     return new String(b, off, len, UTF8_CHARSET);
382   }
383 
384   /**
385    * Write a printable representation of a byte array.
386    *
387    * @param b byte array
388    * @return string
389    * @see #toStringBinary(byte[], int, int)
390    */
391   public static String toStringBinary(final byte [] b) {
392     if (b == null)
393       return "null";
394     return toStringBinary(b, 0, b.length);
395   }
396 
397   /**
398    * Converts the given byte buffer to a printable representation,
399    * from the index 0 (inclusive) to the limit (exclusive),
400    * regardless of the current position.
401    * The position and the other index parameters are not changed.
402    *
403    * @param buf a byte buffer
404    * @return a string representation of the buffer's binary contents
405    * @see #toBytes(ByteBuffer)
406    * @see #getBytes(ByteBuffer)
407    */
408   public static String toStringBinary(ByteBuffer buf) {
409     if (buf == null)
410       return "null";
411     if (buf.hasArray()) {
412       return toStringBinary(buf.array(), buf.arrayOffset(), buf.limit());
413     }
414     return toStringBinary(toBytes(buf));
415   }
416 
417   /**
418    * Write a printable representation of a byte array. Non-printable
419    * characters are hex escaped in the format \\x%02X, eg:
420    * \x00 \x05 etc
421    *
422    * @param b array to write out
423    * @param off offset to start at
424    * @param len length to write
425    * @return string output
426    */
427   public static String toStringBinary(final byte [] b, int off, int len) {
428     StringBuilder result = new StringBuilder();
429     // Just in case we are passed a 'len' that is > buffer length...
430     if (off >= b.length) return result.toString();
431     if (off + len > b.length) len = b.length - off;
432     for (int i = off; i < off + len ; ++i ) {
433       int ch = b[i] & 0xFF;
434       if ( (ch >= '0' && ch <= '9')
435           || (ch >= 'A' && ch <= 'Z')
436           || (ch >= 'a' && ch <= 'z')
437           || " `~!@#$%^&*()-_=+[]{}|;:'\",.<>/?".indexOf(ch) >= 0 ) {
438         result.append((char)ch);
439       } else {
440         result.append(String.format("\\x%02X", ch));
441       }
442     }
443     return result.toString();
444   }
445 
446   private static boolean isHexDigit(char c) {
447     return
448         (c >= 'A' && c <= 'F') ||
449         (c >= '0' && c <= '9');
450   }
451 
452   /**
453    * Takes a ASCII digit in the range A-F0-9 and returns
454    * the corresponding integer/ordinal value.
455    * @param ch  The hex digit.
456    * @return The converted hex value as a byte.
457    */
458   public static byte toBinaryFromHex(byte ch) {
459     if ( ch >= 'A' && ch <= 'F' )
460       return (byte) ((byte)10 + (byte) (ch - 'A'));
461     // else
462     return (byte) (ch - '0');
463   }
464 
465   public static byte [] toBytesBinary(String in) {
466     // this may be bigger than we need, but let's be safe.
467     byte [] b = new byte[in.length()];
468     int size = 0;
469     for (int i = 0; i < in.length(); ++i) {
470       char ch = in.charAt(i);
471       if (ch == '\\' && in.length() > i+1 && in.charAt(i+1) == 'x') {
472         // ok, take next 2 hex digits.
473         char hd1 = in.charAt(i+2);
474         char hd2 = in.charAt(i+3);
475 
476         // they need to be A-F0-9:
477         if (!isHexDigit(hd1) ||
478             !isHexDigit(hd2)) {
479           // bogus escape code, ignore:
480           continue;
481         }
482         // turn hex ASCII digit -> number
483         byte d = (byte) ((toBinaryFromHex((byte)hd1) << 4) + toBinaryFromHex((byte)hd2));
484 
485         b[size++] = d;
486         i += 3; // skip 3
487       } else {
488         b[size++] = (byte) ch;
489       }
490     }
491     // resize:
492     byte [] b2 = new byte[size];
493     System.arraycopy(b, 0, b2, 0, size);
494     return b2;
495   }
496 
497   /**
498    * Converts a string to a UTF-8 byte array.
499    * @param s string
500    * @return the byte array
501    */
502   public static byte[] toBytes(String s) {
503     return s.getBytes(UTF8_CHARSET);
504   }
505 
506   /**
507    * Convert a boolean to a byte array. True becomes -1
508    * and false becomes 0.
509    *
510    * @param b value
511    * @return <code>b</code> encoded in a byte array.
512    */
513   public static byte [] toBytes(final boolean b) {
514     return new byte[] { b ? (byte) -1 : (byte) 0 };
515   }
516 
517   /**
518    * Reverses {@link #toBytes(boolean)}
519    * @param b array
520    * @return True or false.
521    */
522   public static boolean toBoolean(final byte [] b) {
523     if (b.length != 1) {
524       throw new IllegalArgumentException("Array has wrong size: " + b.length);
525     }
526     return b[0] != (byte) 0;
527   }
528 
529   /**
530    * Convert a long value to a byte array using big-endian.
531    *
532    * @param val value to convert
533    * @return the byte array
534    */
535   public static byte[] toBytes(long val) {
536     byte [] b = new byte[8];
537     for (int i = 7; i > 0; i--) {
538       b[i] = (byte) val;
539       val >>>= 8;
540     }
541     b[0] = (byte) val;
542     return b;
543   }
544 
545   /**
546    * Converts a byte array to a long value. Reverses
547    * {@link #toBytes(long)}
548    * @param bytes array
549    * @return the long value
550    */
551   public static long toLong(byte[] bytes) {
552     return toLong(bytes, 0, SIZEOF_LONG);
553   }
554 
555   /**
556    * Converts a byte array to a long value. Assumes there will be
557    * {@link #SIZEOF_LONG} bytes available.
558    *
559    * @param bytes bytes
560    * @param offset offset
561    * @return the long value
562    */
563   public static long toLong(byte[] bytes, int offset) {
564     return toLong(bytes, offset, SIZEOF_LONG);
565   }
566 
567   /**
568    * Converts a byte array to a long value.
569    *
570    * @param bytes array of bytes
571    * @param offset offset into array
572    * @param length length of data (must be {@link #SIZEOF_LONG})
573    * @return the long value
574    * @throws IllegalArgumentException if length is not {@link #SIZEOF_LONG} or
575    * if there's not enough room in the array at the offset indicated.
576    */
577   public static long toLong(byte[] bytes, int offset, final int length) {
578     if (length != SIZEOF_LONG || offset + length > bytes.length) {
579       throw explainWrongLengthOrOffset(bytes, offset, length, SIZEOF_LONG);
580     }
581     if (UnsafeComparer.isAvailable()) {
582       return toLongUnsafe(bytes, offset);
583     } else {
584       long l = 0;
585       for(int i = offset; i < offset + length; i++) {
586         l <<= 8;
587         l ^= bytes[i] & 0xFF;
588       }
589       return l;
590     }
591   }
592 
593   private static IllegalArgumentException
594     explainWrongLengthOrOffset(final byte[] bytes,
595                                final int offset,
596                                final int length,
597                                final int expectedLength) {
598     String reason;
599     if (length != expectedLength) {
600       reason = "Wrong length: " + length + ", expected " + expectedLength;
601     } else {
602      reason = "offset (" + offset + ") + length (" + length + ") exceed the"
603         + " capacity of the array: " + bytes.length;
604     }
605     return new IllegalArgumentException(reason);
606   }
607 
608   /**
609    * Put a long value out to the specified byte array position.
610    * @param bytes the byte array
611    * @param offset position in the array
612    * @param val long to write out
613    * @return incremented offset
614    * @throws IllegalArgumentException if the byte array given doesn't have
615    * enough room at the offset specified.
616    */
617   public static int putLong(byte[] bytes, int offset, long val) {
618     if (bytes.length - offset < SIZEOF_LONG) {
619       throw new IllegalArgumentException("Not enough room to put a long at"
620           + " offset " + offset + " in a " + bytes.length + " byte array");
621     }
622     if (UnsafeComparer.isAvailable()) {
623       return putLongUnsafe(bytes, offset, val);
624     } else {
625       for(int i = offset + 7; i > offset; i--) {
626         bytes[i] = (byte) val;
627         val >>>= 8;
628       }
629       bytes[offset] = (byte) val;
630       return offset + SIZEOF_LONG;
631     }
632   }
633 
634   /**
635    * Put a long value out to the specified byte array position (Unsafe).
636    * @param bytes the byte array
637    * @param offset position in the array
638    * @param val long to write out
639    * @return incremented offset
640    */
641   public static int putLongUnsafe(byte[] bytes, int offset, long val)
642   {
643     if (UnsafeComparer.littleEndian) {
644       val = Long.reverseBytes(val);
645     }
646     UnsafeComparer.theUnsafe.putLong(bytes, (long) offset +
647       UnsafeComparer.BYTE_ARRAY_BASE_OFFSET , val);
648     return offset + SIZEOF_LONG;
649   }
650 
651   /**
652    * Presumes float encoded as IEEE 754 floating-point "single format"
653    * @param bytes byte array
654    * @return Float made from passed byte array.
655    */
656   public static float toFloat(byte [] bytes) {
657     return toFloat(bytes, 0);
658   }
659 
660   /**
661    * Presumes float encoded as IEEE 754 floating-point "single format"
662    * @param bytes array to convert
663    * @param offset offset into array
664    * @return Float made from passed byte array.
665    */
666   public static float toFloat(byte [] bytes, int offset) {
667     return Float.intBitsToFloat(toInt(bytes, offset, SIZEOF_INT));
668   }
669 
670   /**
671    * @param bytes byte array
672    * @param offset offset to write to
673    * @param f float value
674    * @return New offset in <code>bytes</code>
675    */
676   public static int putFloat(byte [] bytes, int offset, float f) {
677     return putInt(bytes, offset, Float.floatToRawIntBits(f));
678   }
679 
680   /**
681    * @param f float value
682    * @return the float represented as byte []
683    */
684   public static byte [] toBytes(final float f) {
685     // Encode it as int
686     return Bytes.toBytes(Float.floatToRawIntBits(f));
687   }
688 
689   /**
690    * @param bytes byte array
691    * @return Return double made from passed bytes.
692    */
693   public static double toDouble(final byte [] bytes) {
694     return toDouble(bytes, 0);
695   }
696 
697   /**
698    * @param bytes byte array
699    * @param offset offset where double is
700    * @return Return double made from passed bytes.
701    */
702   public static double toDouble(final byte [] bytes, final int offset) {
703     return Double.longBitsToDouble(toLong(bytes, offset, SIZEOF_LONG));
704   }
705 
706   /**
707    * @param bytes byte array
708    * @param offset offset to write to
709    * @param d value
710    * @return New offset into array <code>bytes</code>
711    */
712   public static int putDouble(byte [] bytes, int offset, double d) {
713     return putLong(bytes, offset, Double.doubleToLongBits(d));
714   }
715 
716   /**
717    * Serialize a double as the IEEE 754 double format output. The resultant
718    * array will be 8 bytes long.
719    *
720    * @param d value
721    * @return the double represented as byte []
722    */
723   public static byte [] toBytes(final double d) {
724     // Encode it as a long
725     return Bytes.toBytes(Double.doubleToRawLongBits(d));
726   }
727 
728   /**
729    * Convert an int value to a byte array.  Big-endian.  Same as what DataOutputStream.writeInt
730    * does.
731    *
732    * @param val value
733    * @return the byte array
734    */
735   public static byte[] toBytes(int val) {
736     byte [] b = new byte[4];
737     for(int i = 3; i > 0; i--) {
738       b[i] = (byte) val;
739       val >>>= 8;
740     }
741     b[0] = (byte) val;
742     return b;
743   }
744 
745   /**
746    * Converts a byte array to an int value
747    * @param bytes byte array
748    * @return the int value
749    */
750   public static int toInt(byte[] bytes) {
751     return toInt(bytes, 0, SIZEOF_INT);
752   }
753 
754   /**
755    * Converts a byte array to an int value
756    * @param bytes byte array
757    * @param offset offset into array
758    * @return the int value
759    */
760   public static int toInt(byte[] bytes, int offset) {
761     return toInt(bytes, offset, SIZEOF_INT);
762   }
763 
764   /**
765    * Converts a byte array to an int value
766    * @param bytes byte array
767    * @param offset offset into array
768    * @param length length of int (has to be {@link #SIZEOF_INT})
769    * @return the int value
770    * @throws IllegalArgumentException if length is not {@link #SIZEOF_INT} or
771    * if there's not enough room in the array at the offset indicated.
772    */
773   public static int toInt(byte[] bytes, int offset, final int length) {
774     if (length != SIZEOF_INT || offset + length > bytes.length) {
775       throw explainWrongLengthOrOffset(bytes, offset, length, SIZEOF_INT);
776     }
777     if (UnsafeComparer.isAvailable()) {
778       return toIntUnsafe(bytes, offset);
779     } else {
780       int n = 0;
781       for(int i = offset; i < (offset + length); i++) {
782         n <<= 8;
783         n ^= bytes[i] & 0xFF;
784       }
785       return n;
786     }
787   }
788 
789   /**
790    * Converts a byte array to an int value (Unsafe version)
791    * @param bytes byte array
792    * @param offset offset into array
793    * @return the int value
794    */
795   public static int toIntUnsafe(byte[] bytes, int offset) {
796     if (UnsafeComparer.littleEndian) {
797       return Integer.reverseBytes(UnsafeComparer.theUnsafe.getInt(bytes,
798         (long) offset + UnsafeComparer.BYTE_ARRAY_BASE_OFFSET));
799     } else {
800       return UnsafeComparer.theUnsafe.getInt(bytes,
801         (long) offset + UnsafeComparer.BYTE_ARRAY_BASE_OFFSET);
802     }
803   }
804 
805   /**
806    * Converts a byte array to an short value (Unsafe version)
807    * @param bytes byte array
808    * @param offset offset into array
809    * @return the short value
810    */
811   public static short toShortUnsafe(byte[] bytes, int offset) {
812     if (UnsafeComparer.littleEndian) {
813       return Short.reverseBytes(UnsafeComparer.theUnsafe.getShort(bytes,
814         (long) offset + UnsafeComparer.BYTE_ARRAY_BASE_OFFSET));
815     } else {
816       return UnsafeComparer.theUnsafe.getShort(bytes,
817         (long) offset + UnsafeComparer.BYTE_ARRAY_BASE_OFFSET);
818     }
819   }
820 
821   /**
822    * Converts a byte array to an long value (Unsafe version)
823    * @param bytes byte array
824    * @param offset offset into array
825    * @return the long value
826    */
827   public static long toLongUnsafe(byte[] bytes, int offset) {
828     if (UnsafeComparer.littleEndian) {
829       return Long.reverseBytes(UnsafeComparer.theUnsafe.getLong(bytes,
830         (long) offset + UnsafeComparer.BYTE_ARRAY_BASE_OFFSET));
831     } else {
832       return UnsafeComparer.theUnsafe.getLong(bytes,
833         (long) offset + UnsafeComparer.BYTE_ARRAY_BASE_OFFSET);
834     }
835   }
836 
837   /**
838    * Converts a byte array to an int value
839    * @param bytes byte array
840    * @param offset offset into array
841    * @param length how many bytes should be considered for creating int
842    * @return the int value
843    * @throws IllegalArgumentException if there's not enough room in the array at the offset
844    * indicated.
845    */
846   public static int readAsInt(byte[] bytes, int offset, final int length) {
847     if (offset + length > bytes.length) {
848       throw new IllegalArgumentException("offset (" + offset + ") + length (" + length
849           + ") exceed the" + " capacity of the array: " + bytes.length);
850     }
851     int n = 0;
852     for(int i = offset; i < (offset + length); i++) {
853       n <<= 8;
854       n ^= bytes[i] & 0xFF;
855     }
856     return n;
857   }
858 
859   /**
860    * Put an int value out to the specified byte array position.
861    * @param bytes the byte array
862    * @param offset position in the array
863    * @param val int to write out
864    * @return incremented offset
865    * @throws IllegalArgumentException if the byte array given doesn't have
866    * enough room at the offset specified.
867    */
868   public static int putInt(byte[] bytes, int offset, int val) {
869     if (bytes.length - offset < SIZEOF_INT) {
870       throw new IllegalArgumentException("Not enough room to put an int at"
871           + " offset " + offset + " in a " + bytes.length + " byte array");
872     }
873     if (UnsafeComparer.isAvailable()) {
874       return putIntUnsafe(bytes, offset, val);
875     } else {
876       for(int i= offset + 3; i > offset; i--) {
877         bytes[i] = (byte) val;
878         val >>>= 8;
879       }
880       bytes[offset] = (byte) val;
881       return offset + SIZEOF_INT;
882     }
883   }
884 
885   /**
886    * Put an int value out to the specified byte array position (Unsafe).
887    * @param bytes the byte array
888    * @param offset position in the array
889    * @param val int to write out
890    * @return incremented offset
891    */
892   public static int putIntUnsafe(byte[] bytes, int offset, int val)
893   {
894     if (UnsafeComparer.littleEndian) {
895       val = Integer.reverseBytes(val);
896     }
897     UnsafeComparer.theUnsafe.putInt(bytes, (long) offset +
898       UnsafeComparer.BYTE_ARRAY_BASE_OFFSET , val);
899     return offset + SIZEOF_INT;
900   }
901 
902   /**
903    * Convert a short value to a byte array of {@link #SIZEOF_SHORT} bytes long.
904    * @param val value
905    * @return the byte array
906    */
907   public static byte[] toBytes(short val) {
908     byte[] b = new byte[SIZEOF_SHORT];
909     b[1] = (byte) val;
910     val >>= 8;
911     b[0] = (byte) val;
912     return b;
913   }
914 
915   /**
916    * Converts a byte array to a short value
917    * @param bytes byte array
918    * @return the short value
919    */
920   public static short toShort(byte[] bytes) {
921     return toShort(bytes, 0, SIZEOF_SHORT);
922   }
923 
924   /**
925    * Converts a byte array to a short value
926    * @param bytes byte array
927    * @param offset offset into array
928    * @return the short value
929    */
930   public static short toShort(byte[] bytes, int offset) {
931     return toShort(bytes, offset, SIZEOF_SHORT);
932   }
933 
934   /**
935    * Converts a byte array to a short value
936    * @param bytes byte array
937    * @param offset offset into array
938    * @param length length, has to be {@link #SIZEOF_SHORT}
939    * @return the short value
940    * @throws IllegalArgumentException if length is not {@link #SIZEOF_SHORT}
941    * or if there's not enough room in the array at the offset indicated.
942    */
943   public static short toShort(byte[] bytes, int offset, final int length) {
944     if (length != SIZEOF_SHORT || offset + length > bytes.length) {
945       throw explainWrongLengthOrOffset(bytes, offset, length, SIZEOF_SHORT);
946     }
947     if (UnsafeComparer.isAvailable()) {
948       return toShortUnsafe(bytes, offset);
949     } else {
950       short n = 0;
951       n ^= bytes[offset] & 0xFF;
952       n <<= 8;
953       n ^= bytes[offset+1] & 0xFF;
954       return n;
955    }
956   }
957 
958   /**
959    * Returns a new byte array, copied from the given {@code buf},
960    * from the position (inclusive) to the limit (exclusive).
961    * The position and the other index parameters are not changed.
962    *
963    * @param buf a byte buffer
964    * @return the byte array
965    * @see #toBytes(ByteBuffer)
966    */
967   public static byte[] getBytes(ByteBuffer buf) {
968     return readBytes(buf.duplicate());
969   }
970 
971   /**
972    * Put a short value out to the specified byte array position.
973    * @param bytes the byte array
974    * @param offset position in the array
975    * @param val short to write out
976    * @return incremented offset
977    * @throws IllegalArgumentException if the byte array given doesn't have
978    * enough room at the offset specified.
979    */
980   public static int putShort(byte[] bytes, int offset, short val) {
981     if (bytes.length - offset < SIZEOF_SHORT) {
982       throw new IllegalArgumentException("Not enough room to put a short at"
983           + " offset " + offset + " in a " + bytes.length + " byte array");
984     }
985     if (UnsafeComparer.isAvailable()) {
986       return putShortUnsafe(bytes, offset, val);
987     } else {
988       bytes[offset+1] = (byte) val;
989       val >>= 8;
990       bytes[offset] = (byte) val;
991       return offset + SIZEOF_SHORT;
992     }
993   }
994 
995   /**
996    * Put a short value out to the specified byte array position (Unsafe).
997    * @param bytes the byte array
998    * @param offset position in the array
999    * @param val short to write out
1000    * @return incremented offset
1001    */
1002   public static int putShortUnsafe(byte[] bytes, int offset, short val)
1003   {
1004     if (UnsafeComparer.littleEndian) {
1005       val = Short.reverseBytes(val);
1006     }
1007     UnsafeComparer.theUnsafe.putShort(bytes, (long) offset +
1008       UnsafeComparer.BYTE_ARRAY_BASE_OFFSET , val);
1009     return offset + SIZEOF_SHORT;
1010   }
1011 
1012   /**
1013    * Put an int value as short out to the specified byte array position. Only the lower 2 bytes of
1014    * the short will be put into the array. The caller of the API need to make sure they will not
1015    * loose the value by doing so. This is useful to store an unsigned short which is represented as
1016    * int in other parts.
1017    * @param bytes the byte array
1018    * @param offset position in the array
1019    * @param val value to write out
1020    * @return incremented offset
1021    * @throws IllegalArgumentException if the byte array given doesn't have
1022    * enough room at the offset specified.
1023    */
1024   public static int putAsShort(byte[] bytes, int offset, int val) {
1025     if (bytes.length - offset < SIZEOF_SHORT) {
1026       throw new IllegalArgumentException("Not enough room to put a short at"
1027           + " offset " + offset + " in a " + bytes.length + " byte array");
1028     }
1029     bytes[offset+1] = (byte) val;
1030     val >>= 8;
1031     bytes[offset] = (byte) val;
1032     return offset + SIZEOF_SHORT;
1033   }
1034 
1035   /**
1036    * Convert a BigDecimal value to a byte array
1037    *
1038    * @param val
1039    * @return the byte array
1040    */
1041   public static byte[] toBytes(BigDecimal val) {
1042     byte[] valueBytes = val.unscaledValue().toByteArray();
1043     byte[] result = new byte[valueBytes.length + SIZEOF_INT];
1044     int offset = putInt(result, 0, val.scale());
1045     putBytes(result, offset, valueBytes, 0, valueBytes.length);
1046     return result;
1047   }
1048 
1049 
1050   /**
1051    * Converts a byte array to a BigDecimal
1052    *
1053    * @param bytes
1054    * @return the char value
1055    */
1056   public static BigDecimal toBigDecimal(byte[] bytes) {
1057     return toBigDecimal(bytes, 0, bytes.length);
1058   }
1059 
1060   /**
1061    * Converts a byte array to a BigDecimal value
1062    *
1063    * @param bytes
1064    * @param offset
1065    * @param length
1066    * @return the char value
1067    */
1068   public static BigDecimal toBigDecimal(byte[] bytes, int offset, final int length) {
1069     if (bytes == null || length < SIZEOF_INT + 1 ||
1070       (offset + length > bytes.length)) {
1071       return null;
1072     }
1073 
1074     int scale = toInt(bytes, offset);
1075     byte[] tcBytes = new byte[length - SIZEOF_INT];
1076     System.arraycopy(bytes, offset + SIZEOF_INT, tcBytes, 0, length - SIZEOF_INT);
1077     return new BigDecimal(new BigInteger(tcBytes), scale);
1078   }
1079 
1080   /**
1081    * Put a BigDecimal value out to the specified byte array position.
1082    *
1083    * @param bytes  the byte array
1084    * @param offset position in the array
1085    * @param val    BigDecimal to write out
1086    * @return incremented offset
1087    */
1088   public static int putBigDecimal(byte[] bytes, int offset, BigDecimal val) {
1089     if (bytes == null) {
1090       return offset;
1091     }
1092 
1093     byte[] valueBytes = val.unscaledValue().toByteArray();
1094     byte[] result = new byte[valueBytes.length + SIZEOF_INT];
1095     offset = putInt(result, offset, val.scale());
1096     return putBytes(result, offset, valueBytes, 0, valueBytes.length);
1097   }
1098 
1099   /**
1100    * @param vint Integer to make a vint of.
1101    * @return Vint as bytes array.
1102    */
1103   public static byte [] vintToBytes(final long vint) {
1104     long i = vint;
1105     int size = WritableUtils.getVIntSize(i);
1106     byte [] result = new byte[size];
1107     int offset = 0;
1108     if (i >= -112 && i <= 127) {
1109       result[offset] = (byte) i;
1110       return result;
1111     }
1112 
1113     int len = -112;
1114     if (i < 0) {
1115       i ^= -1L; // take one's complement'
1116       len = -120;
1117     }
1118 
1119     long tmp = i;
1120     while (tmp != 0) {
1121       tmp = tmp >> 8;
1122       len--;
1123     }
1124 
1125     result[offset++] = (byte) len;
1126 
1127     len = (len < -120) ? -(len + 120) : -(len + 112);
1128 
1129     for (int idx = len; idx != 0; idx--) {
1130       int shiftbits = (idx - 1) * 8;
1131       long mask = 0xFFL << shiftbits;
1132       result[offset++] = (byte)((i & mask) >> shiftbits);
1133     }
1134     return result;
1135   }
1136 
1137   /**
1138    * @param buffer buffer to convert
1139    * @return vint bytes as an integer.
1140    */
1141   public static long bytesToVint(final byte [] buffer) {
1142     int offset = 0;
1143     byte firstByte = buffer[offset++];
1144     int len = WritableUtils.decodeVIntSize(firstByte);
1145     if (len == 1) {
1146       return firstByte;
1147     }
1148     long i = 0;
1149     for (int idx = 0; idx < len-1; idx++) {
1150       byte b = buffer[offset++];
1151       i = i << 8;
1152       i = i | (b & 0xFF);
1153     }
1154     return (WritableUtils.isNegativeVInt(firstByte) ? ~i : i);
1155   }
1156 
1157   /**
1158    * Reads a zero-compressed encoded long from input stream and returns it.
1159    * @param buffer Binary array
1160    * @param offset Offset into array at which vint begins.
1161    * @throws java.io.IOException e
1162    * @return deserialized long from stream.
1163    */
1164   public static long readVLong(final byte [] buffer, final int offset)
1165   throws IOException {
1166     byte firstByte = buffer[offset];
1167     int len = WritableUtils.decodeVIntSize(firstByte);
1168     if (len == 1) {
1169       return firstByte;
1170     }
1171     long i = 0;
1172     for (int idx = 0; idx < len-1; idx++) {
1173       byte b = buffer[offset + 1 + idx];
1174       i = i << 8;
1175       i = i | (b & 0xFF);
1176     }
1177     return (WritableUtils.isNegativeVInt(firstByte) ? ~i : i);
1178   }
1179 
1180   /**
1181    * @param left left operand
1182    * @param right right operand
1183    * @return 0 if equal, < 0 if left is less than right, etc.
1184    */
1185   public static int compareTo(final byte [] left, final byte [] right) {
1186     return LexicographicalComparerHolder.BEST_COMPARER.
1187       compareTo(left, 0, left.length, right, 0, right.length);
1188   }
1189 
1190   /**
1191    * Lexicographically compare two arrays.
1192    *
1193    * @param buffer1 left operand
1194    * @param buffer2 right operand
1195    * @param offset1 Where to start comparing in the left buffer
1196    * @param offset2 Where to start comparing in the right buffer
1197    * @param length1 How much to compare from the left buffer
1198    * @param length2 How much to compare from the right buffer
1199    * @return 0 if equal, < 0 if left is less than right, etc.
1200    */
1201   public static int compareTo(byte[] buffer1, int offset1, int length1,
1202       byte[] buffer2, int offset2, int length2) {
1203     return LexicographicalComparerHolder.BEST_COMPARER.
1204       compareTo(buffer1, offset1, length1, buffer2, offset2, length2);
1205   }
1206 
1207   interface Comparer<T> {
1208     int compareTo(
1209       T buffer1, int offset1, int length1, T buffer2, int offset2, int length2
1210     );
1211   }
1212 
1213   @VisibleForTesting
1214   static Comparer<byte[]> lexicographicalComparerJavaImpl() {
1215     return LexicographicalComparerHolder.PureJavaComparer.INSTANCE;
1216   }
1217 
1218   /**
1219    * Provides a lexicographical comparer implementation; either a Java
1220    * implementation or a faster implementation based on {@link Unsafe}.
1221    *
1222    * <p>Uses reflection to gracefully fall back to the Java implementation if
1223    * {@code Unsafe} isn't available.
1224    */
1225   @VisibleForTesting
1226   static class LexicographicalComparerHolder {
1227     static final String UNSAFE_COMPARER_NAME =
1228         LexicographicalComparerHolder.class.getName() + "$UnsafeComparer";
1229 
1230     static final Comparer<byte[]> BEST_COMPARER = getBestComparer();
1231     /**
1232      * Returns the Unsafe-using Comparer, or falls back to the pure-Java
1233      * implementation if unable to do so.
1234      */
1235     static Comparer<byte[]> getBestComparer() {
1236       try {
1237         Class<?> theClass = Class.forName(UNSAFE_COMPARER_NAME);
1238 
1239         // yes, UnsafeComparer does implement Comparer<byte[]>
1240         @SuppressWarnings("unchecked")
1241         Comparer<byte[]> comparer =
1242           (Comparer<byte[]>) theClass.getEnumConstants()[0];
1243         return comparer;
1244       } catch (Throwable t) { // ensure we really catch *everything*
1245         return lexicographicalComparerJavaImpl();
1246       }
1247     }
1248 
1249     enum PureJavaComparer implements Comparer<byte[]> {
1250       INSTANCE;
1251 
1252       @Override
1253       public int compareTo(byte[] buffer1, int offset1, int length1,
1254           byte[] buffer2, int offset2, int length2) {
1255         // Short circuit equal case
1256         if (buffer1 == buffer2 &&
1257             offset1 == offset2 &&
1258             length1 == length2) {
1259           return 0;
1260         }
1261         // Bring WritableComparator code local
1262         int end1 = offset1 + length1;
1263         int end2 = offset2 + length2;
1264         for (int i = offset1, j = offset2; i < end1 && j < end2; i++, j++) {
1265           int a = (buffer1[i] & 0xff);
1266           int b = (buffer2[j] & 0xff);
1267           if (a != b) {
1268             return a - b;
1269           }
1270         }
1271         return length1 - length2;
1272       }
1273     }
1274 
1275     @VisibleForTesting
1276     enum UnsafeComparer implements Comparer<byte[]> {
1277       INSTANCE;
1278 
1279       static final Unsafe theUnsafe;
1280 
1281       /** The offset to the first element in a byte array. */
1282       static final int BYTE_ARRAY_BASE_OFFSET;
1283 
1284       static {
1285         theUnsafe = (Unsafe) AccessController.doPrivileged(
1286             new PrivilegedAction<Object>() {
1287               @Override
1288               public Object run() {
1289                 try {
1290                   Field f = Unsafe.class.getDeclaredField("theUnsafe");
1291                   f.setAccessible(true);
1292                   return f.get(null);
1293                 } catch (NoSuchFieldException e) {
1294                   // It doesn't matter what we throw;
1295                   // it's swallowed in getBestComparer().
1296                   throw new Error();
1297                 } catch (IllegalAccessException e) {
1298                   throw new Error();
1299                 }
1300               }
1301             });
1302 
1303         BYTE_ARRAY_BASE_OFFSET = theUnsafe.arrayBaseOffset(byte[].class);
1304 
1305         // sanity check - this should never fail
1306         if (theUnsafe.arrayIndexScale(byte[].class) != 1) {
1307           throw new AssertionError();
1308         }
1309       }
1310 
1311       static final boolean littleEndian =
1312         ByteOrder.nativeOrder().equals(ByteOrder.LITTLE_ENDIAN);
1313 
1314       /**
1315        * Returns true if x1 is less than x2, when both values are treated as
1316        * unsigned long.
1317        */
1318       static boolean lessThanUnsignedLong(long x1, long x2) {
1319         return (x1 + Long.MIN_VALUE) < (x2 + Long.MIN_VALUE);
1320       }
1321 
1322       /**
1323        * Returns true if x1 is less than x2, when both values are treated as
1324        * unsigned int.
1325        */
1326       static boolean lessThanUnsignedInt(int x1, int x2) {
1327         return (x1 & 0xffffffffL) < (x2 & 0xffffffffL);
1328       }
1329 
1330       /**
1331        * Returns true if x1 is less than x2, when both values are treated as
1332        * unsigned short.
1333        */
1334       static boolean lessThanUnsignedShort(short x1, short x2) {
1335         return (x1 & 0xffff) < (x2 & 0xffff);
1336       }
1337 
1338       /**
1339        * Checks if Unsafe is available
1340        * @return true, if available, false - otherwise
1341        */
1342       public static boolean isAvailable()
1343       {
1344         return theUnsafe != null;
1345       }
1346 
1347       /**
1348        * Lexicographically compare two arrays.
1349        *
1350        * @param buffer1 left operand
1351        * @param buffer2 right operand
1352        * @param offset1 Where to start comparing in the left buffer
1353        * @param offset2 Where to start comparing in the right buffer
1354        * @param length1 How much to compare from the left buffer
1355        * @param length2 How much to compare from the right buffer
1356        * @return 0 if equal, < 0 if left is less than right, etc.
1357        */
1358       @Override
1359       public int compareTo(byte[] buffer1, int offset1, int length1,
1360           byte[] buffer2, int offset2, int length2) {
1361 
1362         // Short circuit equal case
1363         if (buffer1 == buffer2 &&
1364             offset1 == offset2 &&
1365             length1 == length2) {
1366           return 0;
1367         }
1368         final int minLength = Math.min(length1, length2);
1369         final int minWords = minLength / SIZEOF_LONG;
1370         final long offset1Adj = offset1 + BYTE_ARRAY_BASE_OFFSET;
1371         final long offset2Adj = offset2 + BYTE_ARRAY_BASE_OFFSET;
1372 
1373         /*
1374          * Compare 8 bytes at a time. Benchmarking shows comparing 8 bytes at a
1375          * time is no slower than comparing 4 bytes at a time even on 32-bit.
1376          * On the other hand, it is substantially faster on 64-bit.
1377          */
1378         for (int i = 0; i < minWords * SIZEOF_LONG; i += SIZEOF_LONG) {
1379           long lw = theUnsafe.getLong(buffer1, offset1Adj + (long) i);
1380           long rw = theUnsafe.getLong(buffer2, offset2Adj + (long) i);
1381           long diff = lw ^ rw;
1382           if(littleEndian){
1383             lw = Long.reverseBytes(lw);
1384             rw = Long.reverseBytes(rw);
1385           }
1386           if (diff != 0) {
1387               return lessThanUnsignedLong(lw, rw) ? -1 : 1;
1388           }
1389         }
1390         int offset = minWords * SIZEOF_LONG;
1391 
1392         if (minLength - offset >= SIZEOF_INT) {
1393           int il = theUnsafe.getInt(buffer1, offset1Adj + offset);
1394           int ir = theUnsafe.getInt(buffer2, offset2Adj + offset);
1395           if(littleEndian){
1396             il = Integer.reverseBytes(il);
1397             ir = Integer.reverseBytes(ir);
1398           }
1399           if(il != ir){
1400             return lessThanUnsignedInt(il, ir) ? -1: 1;
1401           }
1402            offset += SIZEOF_INT;
1403         }
1404         if (minLength - offset >= SIZEOF_SHORT) {
1405           short sl = theUnsafe.getShort(buffer1, offset1Adj + offset);
1406           short sr = theUnsafe.getShort(buffer2, offset2Adj + offset);
1407           if(littleEndian){
1408             sl = Short.reverseBytes(sl);
1409             sr = Short.reverseBytes(sr);
1410           }
1411           if(sl != sr){
1412             return lessThanUnsignedShort(sl, sr) ? -1: 1;
1413           }
1414           offset += SIZEOF_SHORT;
1415         }
1416         if (minLength - offset == 1) {
1417           int a = (buffer1[(int)(offset1 + offset)] & 0xff);
1418           int b = (buffer2[(int)(offset2 + offset)] & 0xff);
1419           if (a != b) {
1420             return a - b;
1421           }
1422         }
1423         return length1 - length2;
1424       }
1425     }
1426   }
1427 
1428   /**
1429    * @param left left operand
1430    * @param right right operand
1431    * @return True if equal
1432    */
1433   public static boolean equals(final byte [] left, final byte [] right) {
1434     // Could use Arrays.equals?
1435     //noinspection SimplifiableConditionalExpression
1436     if (left == right) return true;
1437     if (left == null || right == null) return false;
1438     if (left.length != right.length) return false;
1439     if (left.length == 0) return true;
1440 
1441     // Since we're often comparing adjacent sorted data,
1442     // it's usual to have equal arrays except for the very last byte
1443     // so check that first
1444     if (left[left.length - 1] != right[right.length - 1]) return false;
1445 
1446     return compareTo(left, right) == 0;
1447   }
1448 
1449   public static boolean equals(final byte[] left, int leftOffset, int leftLen,
1450                                final byte[] right, int rightOffset, int rightLen) {
1451     // short circuit case
1452     if (left == right &&
1453         leftOffset == rightOffset &&
1454         leftLen == rightLen) {
1455       return true;
1456     }
1457     // different lengths fast check
1458     if (leftLen != rightLen) {
1459       return false;
1460     }
1461     if (leftLen == 0) {
1462       return true;
1463     }
1464 
1465     // Since we're often comparing adjacent sorted data,
1466     // it's usual to have equal arrays except for the very last byte
1467     // so check that first
1468     if (left[leftOffset + leftLen - 1] != right[rightOffset + rightLen - 1]) return false;
1469 
1470     return LexicographicalComparerHolder.BEST_COMPARER.
1471       compareTo(left, leftOffset, leftLen, right, rightOffset, rightLen) == 0;
1472   }
1473 
1474 
1475   /**
1476    * @param a left operand
1477    * @param buf right operand
1478    * @return True if equal
1479    */
1480   public static boolean equals(byte[] a, ByteBuffer buf) {
1481     if (a == null) return buf == null;
1482     if (buf == null) return false;
1483     if (a.length != buf.remaining()) return false;
1484 
1485     // Thou shalt not modify the original byte buffer in what should be read only operations.
1486     ByteBuffer b = buf.duplicate();
1487     for (byte anA : a) {
1488       if (anA != b.get()) {
1489         return false;
1490       }
1491     }
1492     return true;
1493   }
1494 
1495 
1496   /**
1497    * Return true if the byte array on the right is a prefix of the byte
1498    * array on the left.
1499    */
1500   public static boolean startsWith(byte[] bytes, byte[] prefix) {
1501     return bytes != null && prefix != null &&
1502       bytes.length >= prefix.length &&
1503       LexicographicalComparerHolder.BEST_COMPARER.
1504         compareTo(bytes, 0, prefix.length, prefix, 0, prefix.length) == 0;
1505   }
1506 
1507   /**
1508    * @param b bytes to hash
1509    * @return Runs {@link WritableComparator#hashBytes(byte[], int)} on the
1510    * passed in array.  This method is what {@link org.apache.hadoop.io.Text} and
1511    * {@link ImmutableBytesWritable} use calculating hash code.
1512    */
1513   public static int hashCode(final byte [] b) {
1514     return hashCode(b, b.length);
1515   }
1516 
1517   /**
1518    * @param b value
1519    * @param length length of the value
1520    * @return Runs {@link WritableComparator#hashBytes(byte[], int)} on the
1521    * passed in array.  This method is what {@link org.apache.hadoop.io.Text} and
1522    * {@link ImmutableBytesWritable} use calculating hash code.
1523    */
1524   public static int hashCode(final byte [] b, final int length) {
1525     return WritableComparator.hashBytes(b, length);
1526   }
1527 
1528   /**
1529    * @param b bytes to hash
1530    * @return A hash of <code>b</code> as an Integer that can be used as key in
1531    * Maps.
1532    */
1533   public static Integer mapKey(final byte [] b) {
1534     return hashCode(b);
1535   }
1536 
1537   /**
1538    * @param b bytes to hash
1539    * @param length length to hash
1540    * @return A hash of <code>b</code> as an Integer that can be used as key in
1541    * Maps.
1542    */
1543   public static Integer mapKey(final byte [] b, final int length) {
1544     return hashCode(b, length);
1545   }
1546 
1547   /**
1548    * @param a lower half
1549    * @param b upper half
1550    * @return New array that has a in lower half and b in upper half.
1551    */
1552   public static byte [] add(final byte [] a, final byte [] b) {
1553     return add(a, b, EMPTY_BYTE_ARRAY);
1554   }
1555 
1556   /**
1557    * @param a first third
1558    * @param b second third
1559    * @param c third third
1560    * @return New array made from a, b and c
1561    */
1562   public static byte [] add(final byte [] a, final byte [] b, final byte [] c) {
1563     byte [] result = new byte[a.length + b.length + c.length];
1564     System.arraycopy(a, 0, result, 0, a.length);
1565     System.arraycopy(b, 0, result, a.length, b.length);
1566     System.arraycopy(c, 0, result, a.length + b.length, c.length);
1567     return result;
1568   }
1569 
1570   /**
1571    * @param a array
1572    * @param length amount of bytes to grab
1573    * @return First <code>length</code> bytes from <code>a</code>
1574    */
1575   public static byte [] head(final byte [] a, final int length) {
1576     if (a.length < length) {
1577       return null;
1578     }
1579     byte [] result = new byte[length];
1580     System.arraycopy(a, 0, result, 0, length);
1581     return result;
1582   }
1583 
1584   /**
1585    * @param a array
1586    * @param length amount of bytes to snarf
1587    * @return Last <code>length</code> bytes from <code>a</code>
1588    */
1589   public static byte [] tail(final byte [] a, final int length) {
1590     if (a.length < length) {
1591       return null;
1592     }
1593     byte [] result = new byte[length];
1594     System.arraycopy(a, a.length - length, result, 0, length);
1595     return result;
1596   }
1597 
1598   /**
1599    * @param a array
1600    * @param length new array size
1601    * @return Value in <code>a</code> plus <code>length</code> prepended 0 bytes
1602    */
1603   public static byte [] padHead(final byte [] a, final int length) {
1604     byte [] padding = new byte[length];
1605     for (int i = 0; i < length; i++) {
1606       padding[i] = 0;
1607     }
1608     return add(padding,a);
1609   }
1610 
1611   /**
1612    * @param a array
1613    * @param length new array size
1614    * @return Value in <code>a</code> plus <code>length</code> appended 0 bytes
1615    */
1616   public static byte [] padTail(final byte [] a, final int length) {
1617     byte [] padding = new byte[length];
1618     for (int i = 0; i < length; i++) {
1619       padding[i] = 0;
1620     }
1621     return add(a,padding);
1622   }
1623 
1624   /**
1625    * Split passed range.  Expensive operation relatively.  Uses BigInteger math.
1626    * Useful splitting ranges for MapReduce jobs.
1627    * @param a Beginning of range
1628    * @param b End of range
1629    * @param num Number of times to split range.  Pass 1 if you want to split
1630    * the range in two; i.e. one split.
1631    * @return Array of dividing values
1632    */
1633   public static byte [][] split(final byte [] a, final byte [] b, final int num) {
1634     return split(a, b, false, num);
1635   }
1636 
1637   /**
1638    * Split passed range.  Expensive operation relatively.  Uses BigInteger math.
1639    * Useful splitting ranges for MapReduce jobs.
1640    * @param a Beginning of range
1641    * @param b End of range
1642    * @param inclusive Whether the end of range is prefix-inclusive or is
1643    * considered an exclusive boundary.  Automatic splits are generally exclusive
1644    * and manual splits with an explicit range utilize an inclusive end of range.
1645    * @param num Number of times to split range.  Pass 1 if you want to split
1646    * the range in two; i.e. one split.
1647    * @return Array of dividing values
1648    */
1649   public static byte[][] split(final byte[] a, final byte[] b,
1650       boolean inclusive, final int num) {
1651     byte[][] ret = new byte[num + 2][];
1652     int i = 0;
1653     Iterable<byte[]> iter = iterateOnSplits(a, b, inclusive, num);
1654     if (iter == null)
1655       return null;
1656     for (byte[] elem : iter) {
1657       ret[i++] = elem;
1658     }
1659     return ret;
1660   }
1661 
1662   /**
1663    * Iterate over keys within the passed range, splitting at an [a,b) boundary.
1664    */
1665   public static Iterable<byte[]> iterateOnSplits(final byte[] a,
1666       final byte[] b, final int num)
1667   {
1668     return iterateOnSplits(a, b, false, num);
1669   }
1670 
1671   /**
1672    * Iterate over keys within the passed range.
1673    */
1674   public static Iterable<byte[]> iterateOnSplits(
1675       final byte[] a, final byte[]b, boolean inclusive, final int num)
1676   {
1677     byte [] aPadded;
1678     byte [] bPadded;
1679     if (a.length < b.length) {
1680       aPadded = padTail(a, b.length - a.length);
1681       bPadded = b;
1682     } else if (b.length < a.length) {
1683       aPadded = a;
1684       bPadded = padTail(b, a.length - b.length);
1685     } else {
1686       aPadded = a;
1687       bPadded = b;
1688     }
1689     if (compareTo(aPadded,bPadded) >= 0) {
1690       throw new IllegalArgumentException("b <= a");
1691     }
1692     if (num <= 0) {
1693       throw new IllegalArgumentException("num cannot be <= 0");
1694     }
1695     byte [] prependHeader = {1, 0};
1696     final BigInteger startBI = new BigInteger(add(prependHeader, aPadded));
1697     final BigInteger stopBI = new BigInteger(add(prependHeader, bPadded));
1698     BigInteger diffBI = stopBI.subtract(startBI);
1699     if (inclusive) {
1700       diffBI = diffBI.add(BigInteger.ONE);
1701     }
1702     final BigInteger splitsBI = BigInteger.valueOf(num + 1);
1703     if(diffBI.compareTo(splitsBI) < 0) {
1704       return null;
1705     }
1706     final BigInteger intervalBI;
1707     try {
1708       intervalBI = diffBI.divide(splitsBI);
1709     } catch(Exception e) {
1710       LOG.error("Exception caught during division", e);
1711       return null;
1712     }
1713 
1714     final Iterator<byte[]> iterator = new Iterator<byte[]>() {
1715       private int i = -1;
1716 
1717       @Override
1718       public boolean hasNext() {
1719         return i < num+1;
1720       }
1721 
1722       @Override
1723       public byte[] next() {
1724         i++;
1725         if (i == 0) return a;
1726         if (i == num + 1) return b;
1727 
1728         BigInteger curBI = startBI.add(intervalBI.multiply(BigInteger.valueOf(i)));
1729         byte [] padded = curBI.toByteArray();
1730         if (padded[1] == 0)
1731           padded = tail(padded, padded.length - 2);
1732         else
1733           padded = tail(padded, padded.length - 1);
1734         return padded;
1735       }
1736 
1737       @Override
1738       public void remove() {
1739         throw new UnsupportedOperationException();
1740       }
1741 
1742     };
1743 
1744     return new Iterable<byte[]>() {
1745       @Override
1746       public Iterator<byte[]> iterator() {
1747         return iterator;
1748       }
1749     };
1750   }
1751 
1752   /**
1753    * @param bytes array to hash
1754    * @param offset offset to start from
1755    * @param length length to hash
1756    * */
1757   public static int hashCode(byte[] bytes, int offset, int length) {
1758     int hash = 1;
1759     for (int i = offset; i < offset + length; i++)
1760       hash = (31 * hash) + (int) bytes[i];
1761     return hash;
1762   }
1763 
1764   /**
1765    * @param t operands
1766    * @return Array of byte arrays made from passed array of Text
1767    */
1768   public static byte [][] toByteArrays(final String [] t) {
1769     byte [][] result = new byte[t.length][];
1770     for (int i = 0; i < t.length; i++) {
1771       result[i] = Bytes.toBytes(t[i]);
1772     }
1773     return result;
1774   }
1775 
1776   /**
1777    * @param column operand
1778    * @return A byte array of a byte array where first and only entry is
1779    * <code>column</code>
1780    */
1781   public static byte [][] toByteArrays(final String column) {
1782     return toByteArrays(toBytes(column));
1783   }
1784 
1785   /**
1786    * @param column operand
1787    * @return A byte array of a byte array where first and only entry is
1788    * <code>column</code>
1789    */
1790   public static byte [][] toByteArrays(final byte [] column) {
1791     byte [][] result = new byte[1][];
1792     result[0] = column;
1793     return result;
1794   }
1795 
1796   /**
1797    * Binary search for keys in indexes.
1798    *
1799    * @param arr array of byte arrays to search for
1800    * @param key the key you want to find
1801    * @param offset the offset in the key you want to find
1802    * @param length the length of the key
1803    * @param comparator a comparator to compare.
1804    * @return zero-based index of the key, if the key is present in the array.
1805    *         Otherwise, a value -(i + 1) such that the key is between arr[i -
1806    *         1] and arr[i] non-inclusively, where i is in [0, i], if we define
1807    *         arr[-1] = -Inf and arr[N] = Inf for an N-element array. The above
1808    *         means that this function can return 2N + 1 different values
1809    *         ranging from -(N + 1) to N - 1.
1810    */
1811   public static int binarySearch(byte [][]arr, byte []key, int offset,
1812       int length, RawComparator<?> comparator) {
1813     int low = 0;
1814     int high = arr.length - 1;
1815 
1816     while (low <= high) {
1817       int mid = (low+high) >>> 1;
1818       // we have to compare in this order, because the comparator order
1819       // has special logic when the 'left side' is a special key.
1820       int cmp = comparator.compare(key, offset, length,
1821           arr[mid], 0, arr[mid].length);
1822       // key lives above the midpoint
1823       if (cmp > 0)
1824         low = mid + 1;
1825       // key lives below the midpoint
1826       else if (cmp < 0)
1827         high = mid - 1;
1828       // BAM. how often does this really happen?
1829       else
1830         return mid;
1831     }
1832     return - (low+1);
1833   }
1834 
1835   /**
1836    * Bytewise binary increment/deincrement of long contained in byte array
1837    * on given amount.
1838    *
1839    * @param value - array of bytes containing long (length <= SIZEOF_LONG)
1840    * @param amount value will be incremented on (deincremented if negative)
1841    * @return array of bytes containing incremented long (length == SIZEOF_LONG)
1842    */
1843   public static byte [] incrementBytes(byte[] value, long amount)
1844   {
1845     byte[] val = value;
1846     if (val.length < SIZEOF_LONG) {
1847       // Hopefully this doesn't happen too often.
1848       byte [] newvalue;
1849       if (val[0] < 0) {
1850         newvalue = new byte[]{-1, -1, -1, -1, -1, -1, -1, -1};
1851       } else {
1852         newvalue = new byte[SIZEOF_LONG];
1853       }
1854       System.arraycopy(val, 0, newvalue, newvalue.length - val.length,
1855         val.length);
1856       val = newvalue;
1857     } else if (val.length > SIZEOF_LONG) {
1858       throw new IllegalArgumentException("Increment Bytes - value too big: " +
1859         val.length);
1860     }
1861     if(amount == 0) return val;
1862     if(val[0] < 0){
1863       return binaryIncrementNeg(val, amount);
1864     }
1865     return binaryIncrementPos(val, amount);
1866   }
1867 
1868   /* increment/deincrement for positive value */
1869   private static byte [] binaryIncrementPos(byte [] value, long amount) {
1870     long amo = amount;
1871     int sign = 1;
1872     if (amount < 0) {
1873       amo = -amount;
1874       sign = -1;
1875     }
1876     for(int i=0;i<value.length;i++) {
1877       int cur = ((int)amo % 256) * sign;
1878       amo = (amo >> 8);
1879       int val = value[value.length-i-1] & 0x0ff;
1880       int total = val + cur;
1881       if(total > 255) {
1882         amo += sign;
1883         total %= 256;
1884       } else if (total < 0) {
1885         amo -= sign;
1886       }
1887       value[value.length-i-1] = (byte)total;
1888       if (amo == 0) return value;
1889     }
1890     return value;
1891   }
1892 
1893   /* increment/deincrement for negative value */
1894   private static byte [] binaryIncrementNeg(byte [] value, long amount) {
1895     long amo = amount;
1896     int sign = 1;
1897     if (amount < 0) {
1898       amo = -amount;
1899       sign = -1;
1900     }
1901     for(int i=0;i<value.length;i++) {
1902       int cur = ((int)amo % 256) * sign;
1903       amo = (amo >> 8);
1904       int val = ((~value[value.length-i-1]) & 0x0ff) + 1;
1905       int total = cur - val;
1906       if(total >= 0) {
1907         amo += sign;
1908       } else if (total < -256) {
1909         amo -= sign;
1910         total %= 256;
1911       }
1912       value[value.length-i-1] = (byte)total;
1913       if (amo == 0) return value;
1914     }
1915     return value;
1916   }
1917 
1918   /**
1919    * Writes a string as a fixed-size field, padded with zeros.
1920    */
1921   public static void writeStringFixedSize(final DataOutput out, String s,
1922       int size) throws IOException {
1923     byte[] b = toBytes(s);
1924     if (b.length > size) {
1925       throw new IOException("Trying to write " + b.length + " bytes (" +
1926           toStringBinary(b) + ") into a field of length " + size);
1927     }
1928 
1929     out.writeBytes(s);
1930     for (int i = 0; i < size - s.length(); ++i)
1931       out.writeByte(0);
1932   }
1933 
1934   /**
1935    * Reads a fixed-size field and interprets it as a string padded with zeros.
1936    */
1937   public static String readStringFixedSize(final DataInput in, int size)
1938       throws IOException {
1939     byte[] b = new byte[size];
1940     in.readFully(b);
1941     int n = b.length;
1942     while (n > 0 && b[n - 1] == 0)
1943       --n;
1944 
1945     return toString(b, 0, n);
1946   }
1947 
1948   /**
1949    * Copy the byte array given in parameter and return an instance
1950    * of a new byte array with the same length and the same content.
1951    * @param bytes the byte array to duplicate
1952    * @return a copy of the given byte array
1953    */
1954   public static byte [] copy(byte [] bytes) {
1955     if (bytes == null) return null;
1956     byte [] result = new byte[bytes.length];
1957     System.arraycopy(bytes, 0, result, 0, bytes.length);
1958     return result;
1959   }
1960 
1961   /**
1962    * Copy the byte array given in parameter and return an instance
1963    * of a new byte array with the same length and the same content.
1964    * @param bytes the byte array to copy from
1965    * @return a copy of the given designated byte array
1966    * @param offset
1967    * @param length
1968    */
1969   public static byte [] copy(byte [] bytes, final int offset, final int length) {
1970     if (bytes == null) return null;
1971     byte [] result = new byte[length];
1972     System.arraycopy(bytes, offset, result, 0, length);
1973     return result;
1974   }
1975 
1976   /**
1977    * Search sorted array "a" for byte "key". I can't remember if I wrote this or copied it from
1978    * somewhere. (mcorgan)
1979    * @param a Array to search. Entries must be sorted and unique.
1980    * @param fromIndex First index inclusive of "a" to include in the search.
1981    * @param toIndex Last index exclusive of "a" to include in the search.
1982    * @param key The byte to search for.
1983    * @return The index of key if found. If not found, return -(index + 1), where negative indicates
1984    *         "not found" and the "index + 1" handles the "-0" case.
1985    */
1986   public static int unsignedBinarySearch(byte[] a, int fromIndex, int toIndex, byte key) {
1987     int unsignedKey = key & 0xff;
1988     int low = fromIndex;
1989     int high = toIndex - 1;
1990 
1991     while (low <= high) {
1992       int mid = (low + high) >>> 1;
1993       int midVal = a[mid] & 0xff;
1994 
1995       if (midVal < unsignedKey) {
1996         low = mid + 1;
1997       } else if (midVal > unsignedKey) {
1998         high = mid - 1;
1999       } else {
2000         return mid; // key found
2001       }
2002     }
2003     return -(low + 1); // key not found.
2004   }
2005 
2006   /**
2007    * Treat the byte[] as an unsigned series of bytes, most significant bits first.  Start by adding
2008    * 1 to the rightmost bit/byte and carry over all overflows to the more significant bits/bytes.
2009    *
2010    * @param input The byte[] to increment.
2011    * @return The incremented copy of "in".  May be same length or 1 byte longer.
2012    */
2013   public static byte[] unsignedCopyAndIncrement(final byte[] input) {
2014     byte[] copy = copy(input);
2015     if (copy == null) {
2016       throw new IllegalArgumentException("cannot increment null array");
2017     }
2018     for (int i = copy.length - 1; i >= 0; --i) {
2019       if (copy[i] == -1) {// -1 is all 1-bits, which is the unsigned maximum
2020         copy[i] = 0;
2021       } else {
2022         ++copy[i];
2023         return copy;
2024       }
2025     }
2026     // we maxed out the array
2027     byte[] out = new byte[copy.length + 1];
2028     out[0] = 1;
2029     System.arraycopy(copy, 0, out, 1, copy.length);
2030     return out;
2031   }
2032 
2033   public static boolean equals(List<byte[]> a, List<byte[]> b) {
2034     if (a == null) {
2035       if (b == null) {
2036         return true;
2037       }
2038       return false;
2039     }
2040     if (b == null) {
2041       return false;
2042     }
2043     if (a.size() != b.size()) {
2044       return false;
2045     }
2046     for (int i = 0; i < a.size(); ++i) {
2047       if (!Bytes.equals(a.get(i), b.get(i))) {
2048         return false;
2049       }
2050     }
2051     return true;
2052   }
2053 
2054   public static boolean isSorted(Collection<byte[]> arrays) {
2055     byte[] previous = new byte[0];
2056     for (byte[] array : IterableUtils.nullSafe(arrays)) {
2057       if (Bytes.compareTo(previous, array) > 0) {
2058         return false;
2059       }
2060       previous = array;
2061     }
2062     return true;
2063   }
2064 
2065   public static List<byte[]> getUtf8ByteArrays(List<String> strings) {
2066     List<byte[]> byteArrays = Lists.newArrayListWithCapacity(CollectionUtils.nullSafeSize(strings));
2067     for (String s : IterableUtils.nullSafe(strings)) {
2068       byteArrays.add(Bytes.toBytes(s));
2069     }
2070     return byteArrays;
2071   }
2072 
2073   /**
2074    * Returns the index of the first appearance of the value {@code target} in
2075    * {@code array}.
2076    *
2077    * @param array an array of {@code byte} values, possibly empty
2078    * @param target a primitive {@code byte} value
2079    * @return the least index {@code i} for which {@code array[i] == target}, or
2080    *     {@code -1} if no such index exists.
2081    */
2082   public static int indexOf(byte[] array, byte target) {
2083     for (int i = 0; i < array.length; i++) {
2084       if (array[i] == target) {
2085         return i;
2086       }
2087     }
2088     return -1;
2089   }
2090 
2091   /**
2092    * Returns the start position of the first occurrence of the specified {@code
2093    * target} within {@code array}, or {@code -1} if there is no such occurrence.
2094    *
2095    * <p>More formally, returns the lowest index {@code i} such that {@code
2096    * java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly
2097    * the same elements as {@code target}.
2098    *
2099    * @param array the array to search for the sequence {@code target}
2100    * @param target the array to search for as a sub-sequence of {@code array}
2101    */
2102   public static int indexOf(byte[] array, byte[] target) {
2103     checkNotNull(array, "array");
2104     checkNotNull(target, "target");
2105     if (target.length == 0) {
2106       return 0;
2107     }
2108 
2109     outer:
2110     for (int i = 0; i < array.length - target.length + 1; i++) {
2111       for (int j = 0; j < target.length; j++) {
2112         if (array[i + j] != target[j]) {
2113           continue outer;
2114         }
2115       }
2116       return i;
2117     }
2118     return -1;
2119   }
2120 
2121   /**
2122    * @param array an array of {@code byte} values, possibly empty
2123    * @param target a primitive {@code byte} value
2124    * @return {@code true} if {@code target} is present as an element anywhere in {@code array}.
2125    */
2126   public static boolean contains(byte[] array, byte target) {
2127     return indexOf(array, target) > -1;
2128   }
2129 
2130   /**
2131    * @param array an array of {@code byte} values, possibly empty
2132    * @param target an array of {@code byte}
2133    * @return {@code true} if {@code target} is present anywhere in {@code array}
2134    */
2135   public static boolean contains(byte[] array, byte[] target) {
2136     return indexOf(array, target) > -1;
2137   }
2138 
2139   /**
2140    * Fill given array with zeros.
2141    * @param b array which needs to be filled with zeros
2142    */
2143   public static void zero(byte[] b) {
2144     zero(b, 0, b.length);
2145   }
2146 
2147   /**
2148    * Fill given array with zeros at the specified position.
2149    * @param b
2150    * @param offset
2151    * @param length
2152    */
2153   public static void zero(byte[] b, int offset, int length) {
2154     checkPositionIndex(offset, b.length, "offset");
2155     checkArgument(length > 0, "length must be greater than 0");
2156     checkPositionIndex(offset + length, b.length, "offset + length");
2157     Arrays.fill(b, offset, offset + length, (byte) 0);
2158   }
2159 
2160   private static final SecureRandom RNG = new SecureRandom();
2161 
2162   /**
2163    * Fill given array with random bytes.
2164    * @param b array which needs to be filled with random bytes
2165    */
2166   public static void random(byte[] b) {
2167     RNG.nextBytes(b);
2168   }
2169 
2170   /**
2171    * Fill given array with random bytes at the specified position.
2172    * @param b
2173    * @param offset
2174    * @param length
2175    */
2176   public static void random(byte[] b, int offset, int length) {
2177     checkPositionIndex(offset, b.length, "offset");
2178     checkArgument(length > 0, "length must be greater than 0");
2179     checkPositionIndex(offset + length, b.length, "offset + length");
2180     byte[] buf = new byte[length];
2181     RNG.nextBytes(buf);
2182     System.arraycopy(buf, 0, b, offset, length);
2183   }
2184 
2185   /**
2186    * Create a max byte array with the specified max byte count
2187    * @param maxByteCount the length of returned byte array
2188    * @return the created max byte array
2189    */
2190   public static byte[] createMaxByteArray(int maxByteCount) {
2191     byte[] maxByteArray = new byte[maxByteCount];
2192     for (int i = 0; i < maxByteArray.length; i++) {
2193       maxByteArray[i] = (byte) 0xff;
2194     }
2195     return maxByteArray;
2196   }
2197 
2198   /**
2199    * Create a byte array which is multiple given bytes
2200    * @param srcBytes
2201    * @param multiNum
2202    * @return byte array
2203    */
2204   public static byte[] multiple(byte[] srcBytes, int multiNum) {
2205     if (multiNum <= 0) {
2206       return new byte[0];
2207     }
2208     byte[] result = new byte[srcBytes.length * multiNum];
2209     for (int i = 0; i < multiNum; i++) {
2210       System.arraycopy(srcBytes, 0, result, i * srcBytes.length,
2211         srcBytes.length);
2212     }
2213     return result;
2214   }
2215   
2216   /**
2217    * Convert a byte array into a hex string
2218    * @param b
2219    */
2220   public static String toHex(byte[] b) {
2221     checkArgument(b.length > 0, "length must be greater than 0");
2222     return String.format("%x", new BigInteger(1, b));
2223   }
2224 
2225   /**
2226    * Create a byte array from a string of hash digits. The length of the
2227    * string must be a multiple of 2
2228    * @param hex
2229    */
2230   public static byte[] fromHex(String hex) {
2231     checkArgument(hex.length() > 0, "length must be greater than 0");
2232     checkArgument(hex.length() % 2 == 0, "length must be a multiple of 2");
2233     // Make sure letters are upper case
2234     hex = hex.toUpperCase();
2235     byte[] b = new byte[hex.length() / 2];
2236     for (int i = 0; i < b.length; i++) {
2237       b[i] = (byte)((toBinaryFromHex((byte)hex.charAt(2 * i)) << 4) +
2238         toBinaryFromHex((byte)hex.charAt((2 * i + 1))));
2239     }
2240     return b;
2241   }
2242 
2243 }