/*BEGIN_COPYRIGHT_BLOCK*

PLT Utilities BSD License

Copyright (c) 2007-2015 JavaPLT group at Rice University

All rights reserved.

Developed by: Java Programming Languages Team

Rice University

http://www.cs.rice.edu/~javaplt/

Redistribution and use in source and binary forms, with or without modification, are permitted

provided that the following conditions are met:

- Redistributions of source code must retain the above copyright notice, this list of conditions

and the following disclaimer.

- Redistributions in binary form must reproduce the above copyright notice, this list of

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with the distribution.

- Neither the name of the JavaPLT group, Rice University, nor the names of the library's

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package edu.rice.cs.plt.object;

import java.util.Comparator;

import edu.rice.cs.plt.iter.IterUtil;

/** Utility methods that may be useful in implementing an object of any type. */

public final class ObjectUtil {

private ObjectUtil() {}

public static boolean equal(Object o1, Object o2) {

return (o1 == null) ? (o2 == null) : o1.equals(o2);

}

/** Prime number used for hashing (approximately 2^32 divided by the golden ratio). */

private static final int KNUTH_CONST = -1640531535; // 2654435761 (unsigned)

/** Optimized implementation of {@link #hash(int[])} with 0 args. */

public static int hash() { return 1; }

/** Optimized implementation of {@link #hash(int[])} with 1 arg. */

public static int hash(int a) { return KNUTH_CONST ^ a; }

/** Optimized implementation of {@link #hash(int[])}) with 2 args. */

public static int hash(int a, int b) { return ((KNUTH_CONST ^ a) * KNUTH_CONST) ^ b; }

/** Optimized implementation of {@link #hash(int[])} with 3 args. */

public static int hash(int a, int b, int c) {

return ((((KNUTH_CONST ^ a) * KNUTH_CONST) ^ b) * KNUTH_CONST) ^ c;

}

/** Optimized implementation of {@link #hash(int[])} with 4 args. */

public static int hash(int a, int b, int c, int d) {

return ((((((KNUTH_CONST ^ a) * KNUTH_CONST) ^ b) * KNUTH_CONST) ^ c) * KNUTH_CONST) ^ d;

}

/**

* Produce a hash value based on the given keys according to an algorithm attributed to

* Knuth (The Art of Programming, Vol. 3, Sorting and Searching) (TODO: verify this source).

* The key idea is to combine 32-bit hash keys (where a typical class has multiple hash keys)

* using exclusive OR after multiplying the existing accumulated result by a large prime number.

*/

public static int hash(int... keys) {

int len = keys.length;

int result = 1;

for (int i = 0; i < len; i++) { result = (result * KNUTH_CONST) ^ keys[i]; }

return result;

}

/** Optimized implementation of {@link #hash(Object[])} with 1 arg. */

public static int hash(Object a) { return hash((a == null) ? 0 : a.hashCode()); }

/** Optimized implementation of {@link #hash(Object[])}) with 2 args. */

public static int hash(Object a, Object b) {

return hash((a == null) ? 0 : a.hashCode(), (b == null) ? 0 : b.hashCode());

}

/** Optimized implementation of {@link #hash(Object[])} with 3 args. */

public static int hash(Object a, Object b, Object c) {

return hash((a == null) ? 0 : a.hashCode(), (b == null) ? 0 : b.hashCode(),

(c == null) ? 0 : c.hashCode());

}

/** Optimized implementation of {@link #hash(Object[])} with 4 args. */

public static int hash(Object a, Object b, Object c, Object d) {

return hash((a == null) ? 0 : a.hashCode(), (b == null) ? 0 : b.hashCode(),

(c == null) ? 0 : c.hashCode(), (d == null) ? 0 : d.hashCode());

}

/** Produce a hash code for an object in which {@code #equals()} depends on the given values. */

public static int hash(Object... objs) {

int len = objs.length;

int[] keys = new int[len];

for (int i = 0; i < len; i++) {

Object obj = objs[i];

keys[i] = (obj == null) ? 0 : obj.hashCode();

}

return hash(keys);

}

/** Produce a hash code for an object in which {@code equals()} depends on the given values. */

public static int hash(Iterable<?> iter) {

int result = 1;

for (Object obj : iter) {

int key = (obj == null) ? 0 : obj.hashCode();

result = (result * KNUTH_CONST) ^ key;

}

return result;

}

public static <T1 extends Comparable<? super T1>, T2 extends Comparable<? super T2>>

int compare(T1 x1, T1 y1, T2 x2, T2 y2) {

int result = x1.compareTo(y1);

if (result == 0) { result = x2.compareTo(y2); }

return result;

}

public static <T1, T2> int compare(Comparator<? super T1> comp1, T1 x1, T1 y1,

Comparator<? super T2> comp2, T2 x2, T2 y2) {

int result = comp1.compare(x1, y1);

if (result == 0) { result = comp2.compare(x2, y2); }

return result;

}

public static <T1 extends Comparable<? super T1>, T2 extends Comparable<? super T2>,

T3 extends Comparable<? super T3>>

int compare(T1 x1, T1 y1, T2 x2, T2 y2, T3 x3, T3 y3) {

int result = x1.compareTo(y1);

if (result == 0) { result = x2.compareTo(y2); }

if (result == 0) { result = x3.compareTo(y3); }

return result;

}

public static <T1, T2, T3> int compare(Comparator<? super T1> comp1, T1 x1, T1 y1,

Comparator<? super T2> comp2, T2 x2, T2 y2,

Comparator<? super T3> comp3, T3 x3, T3 y3) {

int result = comp1.compare(x1, y1);

if (result == 0) { result = comp2.compare(x2, y2); }

if (result == 0) { result = comp3.compare(x3, y3); }

return result;

}

public static <T1 extends Comparable<? super T1>, T2 extends Comparable<? super T2>,

T3 extends Comparable<? super T3>, T4 extends Comparable<? super T4>>

int compare(T1 x1, T1 y1, T2 x2, T2 y2, T3 x3, T3 y3, T4 x4, T4 y4) {

int result = x1.compareTo(y1);

if (result == 0) { result = x2.compareTo(y2); }

if (result == 0) { result = x3.compareTo(y3); }

if (result == 0) { result = x4.compareTo(y4); }

return result;

}

public static <T1, T2, T3, T4> int compare(Comparator<? super T1> comp1, T1 x1, T1 y1,

Comparator<? super T2> comp2, T2 x2, T2 y2,

Comparator<? super T3> comp3, T3 x3, T3 y3,

Comparator<? super T4> comp4, T4 x4, T4 y4) {

int result = comp1.compare(x1, y1);

if (result == 0) { result = comp2.compare(x2, y2); }

if (result == 0) { result = comp3.compare(x3, y3); }

if (result == 0) { result = comp4.compare(x4, y4); }

return result;

}

/**

* Get the height of the object when treated as a composite. If {@code obj} implements

* {@code Composite}, invokes {@link Composite#compositeHeight}; otherwise, returns {@code 0}.

*/

public static int compositeHeight(Object obj) {

if (obj instanceof Composite) { return ((Composite) obj).compositeHeight(); }

else { return 0; }

}

/** Get the maximum composite height of a set of objects. */

public static int compositeHeight(Object... objs) { return compositeHeight(IterUtil.asIterable(objs)); }

/** Get the maximum composite height of a set of objects. */

public static int compositeHeight(Iterable<?> objs) {

int result = 0;

for (Object obj : objs) {

int height = compositeHeight(obj);

if (result < height) { result = height; }

}

return result;

}

/**

* Get the composite size of the object. If {@code obj} implements {@code Composite},

* invokes {@link Composite#compositeSize}; otherwise, returns {@code 1}.

*/

public static int compositeSize(Object obj) {

if (obj instanceof Composite) { return ((Composite) obj).compositeSize(); }

else { return 1; }

}

/** Get the total composite size of a set of objects. */

public static int compositeSize(Object... objs) { return compositeSize(IterUtil.asIterable(objs)); }

/** Get the total composite size of a set of objects. */

public static int compositeSize(Iterable<?> objs) {

int result = 0;

for (Object obj : objs) { result += compositeSize(obj); }

return result;

}

}