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
017package com.google.common.primitives;
018
019import static com.google.common.base.Preconditions.checkArgument;
020import static com.google.common.base.Preconditions.checkElementIndex;
021import static com.google.common.base.Preconditions.checkNotNull;
022import static com.google.common.base.Preconditions.checkPositionIndexes;
023import static java.lang.Float.NEGATIVE_INFINITY;
024import static java.lang.Float.POSITIVE_INFINITY;
025
026import com.google.common.annotations.GwtCompatible;
027
028import java.io.Serializable;
029import java.util.AbstractList;
030import java.util.Arrays;
031import java.util.Collection;
032import java.util.Collections;
033import java.util.Comparator;
034import java.util.List;
035import java.util.RandomAccess;
036
037/**
038 * Static utility methods pertaining to {@code float} primitives, that are not
039 * already found in either {@link Float} or {@link Arrays}.
040 *
041 * <p>See the Guava User Guide article on <a href=
042 * "http://code.google.com/p/guava-libraries/wiki/PrimitivesExplained">
043 * primitive utilities</a>.
044 *
045 * @author Kevin Bourrillion
046 * @since 1.0
047 */
048@GwtCompatible
049public final class Floats {
050  private Floats() {}
051
052  /**
053   * The number of bytes required to represent a primitive {@code float}
054   * value.
055   *
056   * @since 10.0
057   */
058  public static final int BYTES = Float.SIZE / Byte.SIZE;
059
060  /**
061   * Returns a hash code for {@code value}; equal to the result of invoking
062   * {@code ((Float) value).hashCode()}.
063   *
064   * @param value a primitive {@code float} value
065   * @return a hash code for the value
066   */
067  public static int hashCode(float value) {
068    // TODO(kevinb): is there a better way, that's still gwt-safe?
069    return ((Float) value).hashCode();
070  }
071
072  /**
073   * Compares the two specified {@code float} values using {@link
074   * Float#compare(float, float)}. You may prefer to invoke that method
075   * directly; this method exists only for consistency with the other utilities
076   * in this package.
077   *
078   * @param a the first {@code float} to compare
079   * @param b the second {@code float} to compare
080   * @return the result of invoking {@link Float#compare(float, float)}
081   */
082  public static int compare(float a, float b) {
083    return Float.compare(a, b);
084  }
085
086  /**
087   * Returns {@code true} if {@code value} represents a real number. This is
088   * equivalent to, but not necessarily implemented as,
089   * {@code !(Float.isInfinite(value) || Float.isNaN(value))}.
090   *
091   * @since 10.0
092   */
093  public static boolean isFinite(float value) {
094    return NEGATIVE_INFINITY < value & value < POSITIVE_INFINITY;
095  }
096
097  /**
098   * Returns {@code true} if {@code target} is present as an element anywhere in
099   * {@code array}. Note that this always returns {@code false} when {@code
100   * target} is {@code NaN}.
101   *
102   * @param array an array of {@code float} values, possibly empty
103   * @param target a primitive {@code float} value
104   * @return {@code true} if {@code array[i] == target} for some value of {@code
105   *     i}
106   */
107  public static boolean contains(float[] array, float target) {
108    for (float value : array) {
109      if (value == target) {
110        return true;
111      }
112    }
113    return false;
114  }
115
116  /**
117   * Returns the index of the first appearance of the value {@code target} in
118   * {@code array}. Note that this always returns {@code -1} when {@code target}
119   * is {@code NaN}.
120   *
121   * @param array an array of {@code float} values, possibly empty
122   * @param target a primitive {@code float} value
123   * @return the least index {@code i} for which {@code array[i] == target}, or
124   *     {@code -1} if no such index exists.
125   */
126  public static int indexOf(float[] array, float target) {
127    return indexOf(array, target, 0, array.length);
128  }
129
130  // TODO(kevinb): consider making this public
131  private static int indexOf(
132      float[] array, float target, int start, int end) {
133    for (int i = start; i < end; i++) {
134      if (array[i] == target) {
135        return i;
136      }
137    }
138    return -1;
139  }
140
141  /**
142   * Returns the start position of the first occurrence of the specified {@code
143   * target} within {@code array}, or {@code -1} if there is no such occurrence.
144   *
145   * <p>More formally, returns the lowest index {@code i} such that {@code
146   * java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly
147   * the same elements as {@code target}.
148   *
149   * <p>Note that this always returns {@code -1} when {@code target} contains
150   * {@code NaN}.
151   *
152   * @param array the array to search for the sequence {@code target}
153   * @param target the array to search for as a sub-sequence of {@code array}
154   */
155  public static int indexOf(float[] array, float[] target) {
156    checkNotNull(array, "array");
157    checkNotNull(target, "target");
158    if (target.length == 0) {
159      return 0;
160    }
161
162    outer:
163    for (int i = 0; i < array.length - target.length + 1; i++) {
164      for (int j = 0; j < target.length; j++) {
165        if (array[i + j] != target[j]) {
166          continue outer;
167        }
168      }
169      return i;
170    }
171    return -1;
172  }
173
174  /**
175   * Returns the index of the last appearance of the value {@code target} in
176   * {@code array}. Note that this always returns {@code -1} when {@code target}
177   * is {@code NaN}.
178   *
179   * @param array an array of {@code float} values, possibly empty
180   * @param target a primitive {@code float} value
181   * @return the greatest index {@code i} for which {@code array[i] == target},
182   *     or {@code -1} if no such index exists.
183   */
184  public static int lastIndexOf(float[] array, float target) {
185    return lastIndexOf(array, target, 0, array.length);
186  }
187
188  // TODO(kevinb): consider making this public
189  private static int lastIndexOf(
190      float[] array, float target, int start, int end) {
191    for (int i = end - 1; i >= start; i--) {
192      if (array[i] == target) {
193        return i;
194      }
195    }
196    return -1;
197  }
198
199  /**
200   * Returns the least value present in {@code array}, using the same rules of
201   * comparison as {@link Math#min(float, float)}.
202   *
203   * @param array a <i>nonempty</i> array of {@code float} values
204   * @return the value present in {@code array} that is less than or equal to
205   *     every other value in the array
206   * @throws IllegalArgumentException if {@code array} is empty
207   */
208  public static float min(float... array) {
209    checkArgument(array.length > 0);
210    float min = array[0];
211    for (int i = 1; i < array.length; i++) {
212      min = Math.min(min, array[i]);
213    }
214    return min;
215  }
216
217  /**
218   * Returns the greatest value present in {@code array}, using the same rules
219   * of comparison as {@link Math#min(float, float)}.
220   *
221   * @param array a <i>nonempty</i> array of {@code float} values
222   * @return the value present in {@code array} that is greater than or equal to
223   *     every other value in the array
224   * @throws IllegalArgumentException if {@code array} is empty
225   */
226  public static float max(float... array) {
227    checkArgument(array.length > 0);
228    float max = array[0];
229    for (int i = 1; i < array.length; i++) {
230      max = Math.max(max, array[i]);
231    }
232    return max;
233  }
234
235  /**
236   * Returns the values from each provided array combined into a single array.
237   * For example, {@code concat(new float[] {a, b}, new float[] {}, new
238   * float[] {c}} returns the array {@code {a, b, c}}.
239   *
240   * @param arrays zero or more {@code float} arrays
241   * @return a single array containing all the values from the source arrays, in
242   *     order
243   */
244  public static float[] concat(float[]... arrays) {
245    int length = 0;
246    for (float[] array : arrays) {
247      length += array.length;
248    }
249    float[] result = new float[length];
250    int pos = 0;
251    for (float[] array : arrays) {
252      System.arraycopy(array, 0, result, pos, array.length);
253      pos += array.length;
254    }
255    return result;
256  }
257
258  /**
259   * Returns an array containing the same values as {@code array}, but
260   * guaranteed to be of a specified minimum length. If {@code array} already
261   * has a length of at least {@code minLength}, it is returned directly.
262   * Otherwise, a new array of size {@code minLength + padding} is returned,
263   * containing the values of {@code array}, and zeroes in the remaining places.
264   *
265   * @param array the source array
266   * @param minLength the minimum length the returned array must guarantee
267   * @param padding an extra amount to "grow" the array by if growth is
268   *     necessary
269   * @throws IllegalArgumentException if {@code minLength} or {@code padding} is
270   *     negative
271   * @return an array containing the values of {@code array}, with guaranteed
272   *     minimum length {@code minLength}
273   */
274  public static float[] ensureCapacity(
275      float[] array, int minLength, int padding) {
276    checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
277    checkArgument(padding >= 0, "Invalid padding: %s", padding);
278    return (array.length < minLength)
279        ? copyOf(array, minLength + padding)
280        : array;
281  }
282
283  // Arrays.copyOf() requires Java 6
284  private static float[] copyOf(float[] original, int length) {
285    float[] copy = new float[length];
286    System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
287    return copy;
288  }
289
290  /**
291   * Returns a string containing the supplied {@code float} values, converted
292   * to strings as specified by {@link Float#toString(float)}, and separated by
293   * {@code separator}. For example, {@code join("-", 1.0f, 2.0f, 3.0f)}
294   * returns the string {@code "1.0-2.0-3.0"}.
295   *
296   * <p>Note that {@link Float#toString(float)} formats {@code float}
297   * differently in GWT.  In the previous example, it returns the string {@code
298   * "1-2-3"}.
299   *
300   * @param separator the text that should appear between consecutive values in
301   *     the resulting string (but not at the start or end)
302   * @param array an array of {@code float} values, possibly empty
303   */
304  public static String join(String separator, float... array) {
305    checkNotNull(separator);
306    if (array.length == 0) {
307      return "";
308    }
309
310    // For pre-sizing a builder, just get the right order of magnitude
311    StringBuilder builder = new StringBuilder(array.length * 12);
312    builder.append(array[0]);
313    for (int i = 1; i < array.length; i++) {
314      builder.append(separator).append(array[i]);
315    }
316    return builder.toString();
317  }
318
319  /**
320   * Returns a comparator that compares two {@code float} arrays
321   * lexicographically. That is, it compares, using {@link
322   * #compare(float, float)}), the first pair of values that follow any
323   * common prefix, or when one array is a prefix of the other, treats the
324   * shorter array as the lesser. For example, {@code [] < [1.0f] < [1.0f, 2.0f]
325   * < [2.0f]}.
326   *
327   * <p>The returned comparator is inconsistent with {@link
328   * Object#equals(Object)} (since arrays support only identity equality), but
329   * it is consistent with {@link Arrays#equals(float[], float[])}.
330   *
331   * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
332   *     Lexicographical order article at Wikipedia</a>
333   * @since 2.0
334   */
335  public static Comparator<float[]> lexicographicalComparator() {
336    return LexicographicalComparator.INSTANCE;
337  }
338
339  private enum LexicographicalComparator implements Comparator<float[]> {
340    INSTANCE;
341
342    @Override
343    public int compare(float[] left, float[] right) {
344      int minLength = Math.min(left.length, right.length);
345      for (int i = 0; i < minLength; i++) {
346        int result = Floats.compare(left[i], right[i]);
347        if (result != 0) {
348          return result;
349        }
350      }
351      return left.length - right.length;
352    }
353  }
354
355  /**
356   * Returns an array containing each value of {@code collection}, converted to
357   * a {@code float} value in the manner of {@link Number#floatValue}.
358   *
359   * <p>Elements are copied from the argument collection as if by {@code
360   * collection.toArray()}.  Calling this method is as thread-safe as calling
361   * that method.
362   *
363   * @param collection a collection of {@code Number} instances
364   * @return an array containing the same values as {@code collection}, in the
365   *     same order, converted to primitives
366   * @throws NullPointerException if {@code collection} or any of its elements
367   *     is null
368   * @since 1.0 (parameter was {@code Collection<Float>} before 12.0)
369   */
370  public static float[] toArray(Collection<? extends Number> collection) {
371    if (collection instanceof FloatArrayAsList) {
372      return ((FloatArrayAsList) collection).toFloatArray();
373    }
374
375    Object[] boxedArray = collection.toArray();
376    int len = boxedArray.length;
377    float[] array = new float[len];
378    for (int i = 0; i < len; i++) {
379      // checkNotNull for GWT (do not optimize)
380      array[i] = ((Number) checkNotNull(boxedArray[i])).floatValue();
381    }
382    return array;
383  }
384
385  /**
386   * Returns a fixed-size list backed by the specified array, similar to {@link
387   * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)},
388   * but any attempt to set a value to {@code null} will result in a {@link
389   * NullPointerException}.
390   *
391   * <p>The returned list maintains the values, but not the identities, of
392   * {@code Float} objects written to or read from it.  For example, whether
393   * {@code list.get(0) == list.get(0)} is true for the returned list is
394   * unspecified.
395   *
396   * <p>The returned list may have unexpected behavior if it contains {@code
397   * NaN}, or if {@code NaN} is used as a parameter to any of its methods.
398   *
399   * @param backingArray the array to back the list
400   * @return a list view of the array
401   */
402  public static List<Float> asList(float... backingArray) {
403    if (backingArray.length == 0) {
404      return Collections.emptyList();
405    }
406    return new FloatArrayAsList(backingArray);
407  }
408
409  @GwtCompatible
410  private static class FloatArrayAsList extends AbstractList<Float>
411      implements RandomAccess, Serializable {
412    final float[] array;
413    final int start;
414    final int end;
415
416    FloatArrayAsList(float[] array) {
417      this(array, 0, array.length);
418    }
419
420    FloatArrayAsList(float[] array, int start, int end) {
421      this.array = array;
422      this.start = start;
423      this.end = end;
424    }
425
426    @Override public int size() {
427      return end - start;
428    }
429
430    @Override public boolean isEmpty() {
431      return false;
432    }
433
434    @Override public Float get(int index) {
435      checkElementIndex(index, size());
436      return array[start + index];
437    }
438
439    @Override public boolean contains(Object target) {
440      // Overridden to prevent a ton of boxing
441      return (target instanceof Float)
442          && Floats.indexOf(array, (Float) target, start, end) != -1;
443    }
444
445    @Override public int indexOf(Object target) {
446      // Overridden to prevent a ton of boxing
447      if (target instanceof Float) {
448        int i = Floats.indexOf(array, (Float) target, start, end);
449        if (i >= 0) {
450          return i - start;
451        }
452      }
453      return -1;
454    }
455
456    @Override public int lastIndexOf(Object target) {
457      // Overridden to prevent a ton of boxing
458      if (target instanceof Float) {
459        int i = Floats.lastIndexOf(array, (Float) target, start, end);
460        if (i >= 0) {
461          return i - start;
462        }
463      }
464      return -1;
465    }
466
467    @Override public Float set(int index, Float element) {
468      checkElementIndex(index, size());
469      float oldValue = array[start + index];
470      // checkNotNull for GWT (do not optimize)
471      array[start + index] = checkNotNull(element);
472      return oldValue;
473    }
474
475    @Override public List<Float> subList(int fromIndex, int toIndex) {
476      int size = size();
477      checkPositionIndexes(fromIndex, toIndex, size);
478      if (fromIndex == toIndex) {
479        return Collections.emptyList();
480      }
481      return new FloatArrayAsList(array, start + fromIndex, start + toIndex);
482    }
483
484    @Override public boolean equals(Object object) {
485      if (object == this) {
486        return true;
487      }
488      if (object instanceof FloatArrayAsList) {
489        FloatArrayAsList that = (FloatArrayAsList) object;
490        int size = size();
491        if (that.size() != size) {
492          return false;
493        }
494        for (int i = 0; i < size; i++) {
495          if (array[start + i] != that.array[that.start + i]) {
496            return false;
497          }
498        }
499        return true;
500      }
501      return super.equals(object);
502    }
503
504    @Override public int hashCode() {
505      int result = 1;
506      for (int i = start; i < end; i++) {
507        result = 31 * result + Floats.hashCode(array[i]);
508      }
509      return result;
510    }
511
512    @Override public String toString() {
513      StringBuilder builder = new StringBuilder(size() * 12);
514      builder.append('[').append(array[start]);
515      for (int i = start + 1; i < end; i++) {
516        builder.append(", ").append(array[i]);
517      }
518      return builder.append(']').toString();
519    }
520
521    float[] toFloatArray() {
522      // Arrays.copyOfRange() is not available under GWT
523      int size = size();
524      float[] result = new float[size];
525      System.arraycopy(array, start, result, 0, size);
526      return result;
527    }
528
529    private static final long serialVersionUID = 0;
530  }
531}