001    /*
002     * Copyright (C) 2008 The Guava Authors
003     *
004     * Licensed under the Apache License, Version 2.0 (the "License");
005     * you may not use this file except in compliance with the License.
006     * You may obtain a copy of the License at
007     *
008     * http://www.apache.org/licenses/LICENSE-2.0
009     *
010     * Unless required by applicable law or agreed to in writing, software
011     * distributed under the License is distributed on an "AS IS" BASIS,
012     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013     * See the License for the specific language governing permissions and
014     * limitations under the License.
015     */
016    
017    package com.google.common.primitives;
018    
019    import static com.google.common.base.Preconditions.checkArgument;
020    import static com.google.common.base.Preconditions.checkElementIndex;
021    import static com.google.common.base.Preconditions.checkNotNull;
022    import static com.google.common.base.Preconditions.checkPositionIndexes;
023    
024    import com.google.common.annotations.GwtCompatible;
025    import com.google.common.annotations.GwtIncompatible;
026    
027    import java.io.Serializable;
028    import java.util.AbstractList;
029    import java.util.Arrays;
030    import java.util.Collection;
031    import java.util.Collections;
032    import java.util.Comparator;
033    import java.util.List;
034    import java.util.RandomAccess;
035    
036    /**
037     * Static utility methods pertaining to {@code long} primitives, that are not
038     * already found in either {@link Long} or {@link Arrays}.
039     *
040     * @author Kevin Bourrillion
041     * @since 1.0
042     */
043    @GwtCompatible(emulated = true)
044    public final class Longs {
045      private Longs() {}
046    
047      /**
048       * The number of bytes required to represent a primitive {@code long}
049       * value.
050       */
051      public static final int BYTES = Long.SIZE / Byte.SIZE;
052    
053      /**
054       * The largest power of two that can be represented as a {@code long}.
055       *
056       * @since 10.0
057       */
058      public static final long MAX_POWER_OF_TWO = 1L << (Long.SIZE - 2);
059    
060      /**
061       * Returns a hash code for {@code value}; equal to the result of invoking
062       * {@code ((Long) value).hashCode()}.
063       *
064       * <p>This method always return the value specified by {@link
065       * Long#hashCode()} in java, which might be different from
066       * {@code ((Long) value).hashCode()} in GWT because {@link Long#hashCode()}
067       * in GWT does not obey the JRE contract.
068       *
069       * @param value a primitive {@code long} value
070       * @return a hash code for the value
071       */
072      public static int hashCode(long value) {
073        return (int) (value ^ (value >>> 32));
074      }
075    
076      /**
077       * Compares the two specified {@code long} values. The sign of the value
078       * returned is the same as that of {@code ((Long) a).compareTo(b)}.
079       *
080       * @param a the first {@code long} to compare
081       * @param b the second {@code long} to compare
082       * @return a negative value if {@code a} is less than {@code b}; a positive
083       *     value if {@code a} is greater than {@code b}; or zero if they are equal
084       */
085      public static int compare(long a, long b) {
086        return (a < b) ? -1 : ((a > b) ? 1 : 0);
087      }
088    
089      /**
090       * Returns {@code true} if {@code target} is present as an element anywhere in
091       * {@code array}.
092       *
093       * @param array an array of {@code long} values, possibly empty
094       * @param target a primitive {@code long} value
095       * @return {@code true} if {@code array[i] == target} for some value of {@code
096       *     i}
097       */
098      public static boolean contains(long[] array, long target) {
099        for (long value : array) {
100          if (value == target) {
101            return true;
102          }
103        }
104        return false;
105      }
106    
107      /**
108       * Returns the index of the first appearance of the value {@code target} in
109       * {@code array}.
110       *
111       * @param array an array of {@code long} values, possibly empty
112       * @param target a primitive {@code long} value
113       * @return the least index {@code i} for which {@code array[i] == target}, or
114       *     {@code -1} if no such index exists.
115       */
116      public static int indexOf(long[] array, long target) {
117        return indexOf(array, target, 0, array.length);
118      }
119    
120      // TODO(kevinb): consider making this public
121      private static int indexOf(
122          long[] array, long target, int start, int end) {
123        for (int i = start; i < end; i++) {
124          if (array[i] == target) {
125            return i;
126          }
127        }
128        return -1;
129      }
130    
131      /**
132       * Returns the start position of the first occurrence of the specified {@code
133       * target} within {@code array}, or {@code -1} if there is no such occurrence.
134       *
135       * <p>More formally, returns the lowest index {@code i} such that {@code
136       * java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly
137       * the same elements as {@code target}.
138       *
139       * @param array the array to search for the sequence {@code target}
140       * @param target the array to search for as a sub-sequence of {@code array}
141       */
142      public static int indexOf(long[] array, long[] target) {
143        checkNotNull(array, "array");
144        checkNotNull(target, "target");
145        if (target.length == 0) {
146          return 0;
147        }
148    
149        outer:
150        for (int i = 0; i < array.length - target.length + 1; i++) {
151          for (int j = 0; j < target.length; j++) {
152            if (array[i + j] != target[j]) {
153              continue outer;
154            }
155          }
156          return i;
157        }
158        return -1;
159      }
160    
161      /**
162       * Returns the index of the last appearance of the value {@code target} in
163       * {@code array}.
164       *
165       * @param array an array of {@code long} values, possibly empty
166       * @param target a primitive {@code long} value
167       * @return the greatest index {@code i} for which {@code array[i] == target},
168       *     or {@code -1} if no such index exists.
169       */
170      public static int lastIndexOf(long[] array, long target) {
171        return lastIndexOf(array, target, 0, array.length);
172      }
173    
174      // TODO(kevinb): consider making this public
175      private static int lastIndexOf(
176          long[] array, long target, int start, int end) {
177        for (int i = end - 1; i >= start; i--) {
178          if (array[i] == target) {
179            return i;
180          }
181        }
182        return -1;
183      }
184    
185      /**
186       * Returns the least value present in {@code array}.
187       *
188       * @param array a <i>nonempty</i> array of {@code long} values
189       * @return the value present in {@code array} that is less than or equal to
190       *     every other value in the array
191       * @throws IllegalArgumentException if {@code array} is empty
192       */
193      public static long min(long... array) {
194        checkArgument(array.length > 0);
195        long min = array[0];
196        for (int i = 1; i < array.length; i++) {
197          if (array[i] < min) {
198            min = array[i];
199          }
200        }
201        return min;
202      }
203    
204      /**
205       * Returns the greatest value present in {@code array}.
206       *
207       * @param array a <i>nonempty</i> array of {@code long} values
208       * @return the value present in {@code array} that is greater than or equal to
209       *     every other value in the array
210       * @throws IllegalArgumentException if {@code array} is empty
211       */
212      public static long max(long... array) {
213        checkArgument(array.length > 0);
214        long max = array[0];
215        for (int i = 1; i < array.length; i++) {
216          if (array[i] > max) {
217            max = array[i];
218          }
219        }
220        return max;
221      }
222    
223      /**
224       * Returns the values from each provided array combined into a single array.
225       * For example, {@code concat(new long[] {a, b}, new long[] {}, new
226       * long[] {c}} returns the array {@code {a, b, c}}.
227       *
228       * @param arrays zero or more {@code long} arrays
229       * @return a single array containing all the values from the source arrays, in
230       *     order
231       */
232      public static long[] concat(long[]... arrays) {
233        int length = 0;
234        for (long[] array : arrays) {
235          length += array.length;
236        }
237        long[] result = new long[length];
238        int pos = 0;
239        for (long[] array : arrays) {
240          System.arraycopy(array, 0, result, pos, array.length);
241          pos += array.length;
242        }
243        return result;
244      }
245    
246      /**
247       * Returns a big-endian representation of {@code value} in an 8-element byte
248       * array; equivalent to {@code ByteBuffer.allocate(8).putLong(value).array()}.
249       * For example, the input value {@code 0x1213141516171819L} would yield the
250       * byte array {@code {0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19}}.
251       *
252       * <p>If you need to convert and concatenate several values (possibly even of
253       * different types), use a shared {@link java.nio.ByteBuffer} instance, or use
254       * {@link com.google.common.io.ByteStreams#newDataOutput()} to get a growable
255       * buffer.
256       */
257      @GwtIncompatible("doesn't work")
258      public static byte[] toByteArray(long value) {
259        return new byte[] {
260            (byte) (value >> 56),
261            (byte) (value >> 48),
262            (byte) (value >> 40),
263            (byte) (value >> 32),
264            (byte) (value >> 24),
265            (byte) (value >> 16),
266            (byte) (value >> 8),
267            (byte) value};
268      }
269    
270      /**
271       * Returns the {@code long} value whose big-endian representation is
272       * stored in the first 8 bytes of {@code bytes}; equivalent to {@code
273       * ByteBuffer.wrap(bytes).getLong()}. For example, the input byte array
274       * {@code {0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19}} would yield the
275       * {@code long} value {@code 0x1213141516171819L}.
276       *
277       * <p>Arguably, it's preferable to use {@link java.nio.ByteBuffer}; that
278       * library exposes much more flexibility at little cost in readability.
279       *
280       * @throws IllegalArgumentException if {@code bytes} has fewer than 8
281       *     elements
282       */
283      @GwtIncompatible("doesn't work")
284      public static long fromByteArray(byte[] bytes) {
285        checkArgument(bytes.length >= BYTES,
286            "array too small: %s < %s", bytes.length, BYTES);
287        return fromBytes(bytes[0], bytes[1], bytes[2], bytes[3],
288            bytes[4], bytes[5], bytes[6], bytes[7]) ;
289      }
290    
291      /**
292       * Returns the {@code long} value whose byte representation is the given 8
293       * bytes, in big-endian order; equivalent to {@code Longs.fromByteArray(new
294       * byte[] {b1, b2, b3, b4, b5, b6, b7, b8})}.
295       *
296       * @since 7.0
297       */
298      @GwtIncompatible("doesn't work")
299      public static long fromBytes(byte b1, byte b2, byte b3, byte b4,
300          byte b5, byte b6, byte b7, byte b8) {
301        return (b1 & 0xFFL) << 56
302            | (b2 & 0xFFL) << 48
303            | (b3 & 0xFFL) << 40
304            | (b4 & 0xFFL) << 32
305            | (b5 & 0xFFL) << 24
306            | (b6 & 0xFFL) << 16
307            | (b7 & 0xFFL) << 8
308            | (b8 & 0xFFL);
309      }
310    
311      /**
312       * Returns an array containing the same values as {@code array}, but
313       * guaranteed to be of a specified minimum length. If {@code array} already
314       * has a length of at least {@code minLength}, it is returned directly.
315       * Otherwise, a new array of size {@code minLength + padding} is returned,
316       * containing the values of {@code array}, and zeroes in the remaining places.
317       *
318       * @param array the source array
319       * @param minLength the minimum length the returned array must guarantee
320       * @param padding an extra amount to "grow" the array by if growth is
321       *     necessary
322       * @throws IllegalArgumentException if {@code minLength} or {@code padding} is
323       *     negative
324       * @return an array containing the values of {@code array}, with guaranteed
325       *     minimum length {@code minLength}
326       */
327      public static long[] ensureCapacity(
328          long[] array, int minLength, int padding) {
329        checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
330        checkArgument(padding >= 0, "Invalid padding: %s", padding);
331        return (array.length < minLength)
332            ? copyOf(array, minLength + padding)
333            : array;
334      }
335    
336      // Arrays.copyOf() requires Java 6
337      private static long[] copyOf(long[] original, int length) {
338        long[] copy = new long[length];
339        System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
340        return copy;
341      }
342    
343      /**
344       * Returns a string containing the supplied {@code long} values separated
345       * by {@code separator}. For example, {@code join("-", 1L, 2L, 3L)} returns
346       * the string {@code "1-2-3"}.
347       *
348       * @param separator the text that should appear between consecutive values in
349       *     the resulting string (but not at the start or end)
350       * @param array an array of {@code long} values, possibly empty
351       */
352      public static String join(String separator, long... array) {
353        checkNotNull(separator);
354        if (array.length == 0) {
355          return "";
356        }
357    
358        // For pre-sizing a builder, just get the right order of magnitude
359        StringBuilder builder = new StringBuilder(array.length * 10);
360        builder.append(array[0]);
361        for (int i = 1; i < array.length; i++) {
362          builder.append(separator).append(array[i]);
363        }
364        return builder.toString();
365      }
366    
367      /**
368       * Returns a comparator that compares two {@code long} arrays
369       * lexicographically. That is, it compares, using {@link
370       * #compare(long, long)}), the first pair of values that follow any
371       * common prefix, or when one array is a prefix of the other, treats the
372       * shorter array as the lesser. For example,
373       * {@code [] < [1L] < [1L, 2L] < [2L]}.
374       *
375       * <p>The returned comparator is inconsistent with {@link
376       * Object#equals(Object)} (since arrays support only identity equality), but
377       * it is consistent with {@link Arrays#equals(long[], long[])}.
378       *
379       * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
380       *     Lexicographical order article at Wikipedia</a>
381       * @since 2.0
382       */
383      public static Comparator<long[]> lexicographicalComparator() {
384        return LexicographicalComparator.INSTANCE;
385      }
386    
387      private enum LexicographicalComparator implements Comparator<long[]> {
388        INSTANCE;
389    
390        @Override
391        public int compare(long[] left, long[] right) {
392          int minLength = Math.min(left.length, right.length);
393          for (int i = 0; i < minLength; i++) {
394            int result = Longs.compare(left[i], right[i]);
395            if (result != 0) {
396              return result;
397            }
398          }
399          return left.length - right.length;
400        }
401      }
402    
403      /**
404       * Copies a collection of {@code Long} instances into a new array of
405       * primitive {@code long} values.
406       *
407       * <p>Elements are copied from the argument collection as if by {@code
408       * collection.toArray()}.  Calling this method is as thread-safe as calling
409       * that method.
410       *
411       * @param collection a collection of {@code Long} objects
412       * @return an array containing the same values as {@code collection}, in the
413       *     same order, converted to primitives
414       * @throws NullPointerException if {@code collection} or any of its elements
415       *     is null
416       */
417      public static long[] toArray(Collection<Long> collection) {
418        if (collection instanceof LongArrayAsList) {
419          return ((LongArrayAsList) collection).toLongArray();
420        }
421    
422        Object[] boxedArray = collection.toArray();
423        int len = boxedArray.length;
424        long[] array = new long[len];
425        for (int i = 0; i < len; i++) {
426          // checkNotNull for GWT (do not optimize)
427          array[i] = (Long) checkNotNull(boxedArray[i]);
428        }
429        return array;
430      }
431    
432      /**
433       * Returns a fixed-size list backed by the specified array, similar to {@link
434       * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)},
435       * but any attempt to set a value to {@code null} will result in a {@link
436       * NullPointerException}.
437       *
438       * <p>The returned list maintains the values, but not the identities, of
439       * {@code Long} objects written to or read from it.  For example, whether
440       * {@code list.get(0) == list.get(0)} is true for the returned list is
441       * unspecified.
442       *
443       * @param backingArray the array to back the list
444       * @return a list view of the array
445       */
446      public static List<Long> asList(long... backingArray) {
447        if (backingArray.length == 0) {
448          return Collections.emptyList();
449        }
450        return new LongArrayAsList(backingArray);
451      }
452    
453      @GwtCompatible
454      private static class LongArrayAsList extends AbstractList<Long>
455          implements RandomAccess, Serializable {
456        final long[] array;
457        final int start;
458        final int end;
459    
460        LongArrayAsList(long[] array) {
461          this(array, 0, array.length);
462        }
463    
464        LongArrayAsList(long[] array, int start, int end) {
465          this.array = array;
466          this.start = start;
467          this.end = end;
468        }
469    
470        @Override public int size() {
471          return end - start;
472        }
473    
474        @Override public boolean isEmpty() {
475          return false;
476        }
477    
478        @Override public Long get(int index) {
479          checkElementIndex(index, size());
480          return array[start + index];
481        }
482    
483        @Override public boolean contains(Object target) {
484          // Overridden to prevent a ton of boxing
485          return (target instanceof Long)
486              && Longs.indexOf(array, (Long) target, start, end) != -1;
487        }
488    
489        @Override public int indexOf(Object target) {
490          // Overridden to prevent a ton of boxing
491          if (target instanceof Long) {
492            int i = Longs.indexOf(array, (Long) target, start, end);
493            if (i >= 0) {
494              return i - start;
495            }
496          }
497          return -1;
498        }
499    
500        @Override public int lastIndexOf(Object target) {
501          // Overridden to prevent a ton of boxing
502          if (target instanceof Long) {
503            int i = Longs.lastIndexOf(array, (Long) target, start, end);
504            if (i >= 0) {
505              return i - start;
506            }
507          }
508          return -1;
509        }
510    
511        @Override public Long set(int index, Long element) {
512          checkElementIndex(index, size());
513          long oldValue = array[start + index];
514          array[start + index] = checkNotNull(element);  // checkNotNull for GWT (do not optimize)
515          return oldValue;
516        }
517    
518        @Override public List<Long> subList(int fromIndex, int toIndex) {
519          int size = size();
520          checkPositionIndexes(fromIndex, toIndex, size);
521          if (fromIndex == toIndex) {
522            return Collections.emptyList();
523          }
524          return new LongArrayAsList(array, start + fromIndex, start + toIndex);
525        }
526    
527        @Override public boolean equals(Object object) {
528          if (object == this) {
529            return true;
530          }
531          if (object instanceof LongArrayAsList) {
532            LongArrayAsList that = (LongArrayAsList) object;
533            int size = size();
534            if (that.size() != size) {
535              return false;
536            }
537            for (int i = 0; i < size; i++) {
538              if (array[start + i] != that.array[that.start + i]) {
539                return false;
540              }
541            }
542            return true;
543          }
544          return super.equals(object);
545        }
546    
547        @Override public int hashCode() {
548          int result = 1;
549          for (int i = start; i < end; i++) {
550            result = 31 * result + Longs.hashCode(array[i]);
551          }
552          return result;
553        }
554    
555        @Override public String toString() {
556          StringBuilder builder = new StringBuilder(size() * 10);
557          builder.append('[').append(array[start]);
558          for (int i = start + 1; i < end; i++) {
559            builder.append(", ").append(array[i]);
560          }
561          return builder.append(']').toString();
562        }
563    
564        long[] toLongArray() {
565          // Arrays.copyOfRange() requires Java 6
566          int size = size();
567          long[] result = new long[size];
568          System.arraycopy(array, start, result, 0, size);
569          return result;
570        }
571    
572        private static final long serialVersionUID = 0;
573      }
574    }