tikhomirov@307: /*
tikhomirov@307:  * Copyright (c) 2011 TMate Software Ltd
tikhomirov@307:  *  
tikhomirov@307:  * This program is free software; you can redistribute it and/or modify
tikhomirov@307:  * it under the terms of the GNU General Public License as published by
tikhomirov@307:  * the Free Software Foundation; version 2 of the License.
tikhomirov@307:  *
tikhomirov@307:  * This program is distributed in the hope that it will be useful,
tikhomirov@307:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
tikhomirov@307:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
tikhomirov@307:  * GNU General Public License for more details.
tikhomirov@307:  *
tikhomirov@307:  * For information on how to redistribute this software under
tikhomirov@307:  * the terms of a license other than GNU General Public License
tikhomirov@307:  * contact TMate Software at support@hg4j.com
tikhomirov@307:  */
tikhomirov@307: package org.tmatesoft.hg.internal;
tikhomirov@307: 
tikhomirov@307: /**
tikhomirov@311:  * Internal alternative to Arrays.sort to build reversed index along with sorting
tikhomirov@307:  * 
tikhomirov@307:  * @author Artem Tikhomirov
tikhomirov@307:  * @author TMate Software Ltd.
tikhomirov@307:  */
tikhomirov@307: public class ArrayHelper {
tikhomirov@307: 	private int[] reverse;
tikhomirov@307: 
tikhomirov@307: 	@SuppressWarnings("unchecked")
tikhomirov@307: 	public void sort(Comparable<?>[] a) {
tikhomirov@307: //		Object[] aux = (Object[]) a.clone();
tikhomirov@307: 		reverse = new int[a.length];
tikhomirov@307: 		sort1((Comparable<Object>[])a, 0, a.length);
tikhomirov@310: 		for (int i = 0; i < reverse.length; i++) {
tikhomirov@310: 			// element that was not moved don't have an index in reverse.
tikhomirov@310: 			// perhaps, can do it inside sort alg?
tikhomirov@311: 			// Alternatively, may start with filling reverse[] array with initial indexes and
tikhomirov@311: 			// avoid != 0 comparisons in #swap altogether?
tikhomirov@310: 			if (reverse[i] == 0) {
tikhomirov@310: 				reverse[i] = i+1;
tikhomirov@310: 			}
tikhomirov@310: 		}
tikhomirov@307: 	}
tikhomirov@311: 
tikhomirov@311: 	/**
tikhomirov@311: 	 * Slightly modified version of Arrays.sort1(int[], int, int) quicksort alg (just to deal with Object[])
tikhomirov@311: 	 */
tikhomirov@307:     private void sort1(Comparable<Object> x[], int off, int len) {
tikhomirov@307:     	// Insertion sort on smallest arrays
tikhomirov@307:     	if (len < 7) {
tikhomirov@307:     	    for (int i=off; i<len+off; i++)
tikhomirov@307:     			for (int j=i; j>off && x[j-1].compareTo(x[j]) > 0; j--)
tikhomirov@307:     			    swap(x, j, j-1);
tikhomirov@307:     	    return;
tikhomirov@307:     	}
tikhomirov@307: 
tikhomirov@307:     	// Choose a partition element, v
tikhomirov@307:     	int m = off + (len >> 1);       // Small arrays, middle element
tikhomirov@307:     	if (len > 7) {
tikhomirov@307:     	    int l = off;
tikhomirov@307:     	    int n = off + len - 1;
tikhomirov@307:     	    if (len > 40) {        // Big arrays, pseudomedian of 9
tikhomirov@307:     			int s = len/8;
tikhomirov@307: 	    		l = med3(x, l,     l+s, l+2*s);
tikhomirov@307: 	    		m = med3(x, m-s,   m,   m+s);
tikhomirov@307: 	    		n = med3(x, n-2*s, n-s, n);
tikhomirov@307:     	    }
tikhomirov@307:     	    m = med3(x, l, m, n); // Mid-size, med of 3
tikhomirov@307:     	}
tikhomirov@307:     	Comparable<Object> v = x[m];
tikhomirov@307: 
tikhomirov@307:     	// Establish Invariant: v* (<v)* (>v)* v*
tikhomirov@307:     	int a = off, b = a, c = off + len - 1, d = c;
tikhomirov@307:     	while(true) {
tikhomirov@307:     	    while (b <= c && x[b].compareTo(v) <= 0) {
tikhomirov@307:     			if (x[b] == v)
tikhomirov@307:     			    swap(x, a++, b);
tikhomirov@307:     			b++;
tikhomirov@307:     	    }
tikhomirov@307:     	    while (c >= b && x[c].compareTo(v) >= 0) {
tikhomirov@307:     			if (x[c] == v)
tikhomirov@307:     			    swap(x, c, d--);
tikhomirov@307:     			c--;
tikhomirov@307:     	    }
tikhomirov@307:     	    if (b > c)
tikhomirov@307:     			break;
tikhomirov@307:     	    swap(x, b++, c--);
tikhomirov@307:     	}
tikhomirov@307: 
tikhomirov@307:     	// Swap partition elements back to middle
tikhomirov@307:     	int s, n = off + len;
tikhomirov@307:     	s = Math.min(a-off, b-a  );  vecswap(x, off, b-s, s);
tikhomirov@307:     	s = Math.min(d-c,   n-d-1);  vecswap(x, b,   n-s, s);
tikhomirov@307: 
tikhomirov@307:     	// Recursively sort non-partition-elements
tikhomirov@307:     	if ((s = b-a) > 1)
tikhomirov@307:     	    sort1(x, off, s);
tikhomirov@307:     	if ((s = d-c) > 1)
tikhomirov@307:     	    sort1(x, n-s, s);
tikhomirov@307:     }
tikhomirov@307: 
tikhomirov@307:     /**
tikhomirov@307:      * Swaps x[a .. (a+n-1)] with x[b .. (b+n-1)].
tikhomirov@307:      */
tikhomirov@307:     private void vecswap(Object[] x, int a, int b, int n) {
tikhomirov@307: 		for (int i=0; i<n; i++, a++, b++) {
tikhomirov@307: 		    swap(x, a, b);
tikhomirov@307: 		}
tikhomirov@307:     }
tikhomirov@307: 
tikhomirov@307:     /**
tikhomirov@307:      * Returns the index of the median of the three indexed integers.
tikhomirov@307:      */
tikhomirov@307:     private static int med3(Comparable<Object>[] x, int a, int b, int c) {
tikhomirov@307: 	return (x[a].compareTo(x[b]) < 0 ?
tikhomirov@307: 		(x[b].compareTo(x[c]) < 0 ? b : x[a].compareTo(x[c]) < 0 ? c : a) :
tikhomirov@307: 		(x[b].compareTo(x[c]) > 0 ? b : x[a].compareTo(x[c]) > 0 ? c : a));
tikhomirov@307:     }
tikhomirov@307: 
tikhomirov@307: 
tikhomirov@307: 	/**
tikhomirov@307: 	 * @return the reverse
tikhomirov@307: 	 */
tikhomirov@307: 	public int[] getReverse() {
tikhomirov@307: 		return reverse;
tikhomirov@307: 	}
tikhomirov@307: 
tikhomirov@307: 	/**
tikhomirov@307: 	 * Swaps x[a] with x[b].
tikhomirov@307: 	 */
tikhomirov@307: 	private void swap(Object[] x, int a, int b) {
tikhomirov@307: 		Object t = x[a];
tikhomirov@307: 		x[a] = x[b];
tikhomirov@307: 		x[b] = t;
tikhomirov@307: 		int z1 = reverse[a] != 0 ? reverse[a] : a+1;
tikhomirov@307: 		int z2 = reverse[b] != 0 ? reverse[b] : b+1;
tikhomirov@307: 		reverse[b] = z1;
tikhomirov@307: 		reverse[a] = z2;
tikhomirov@307: 	}
tikhomirov@307: }