src/glu/sgi/libnurbs/nurbtess/quicksort.cc

   1 /*
   2 ** License Applicability. Except to the extent portions of this file are
   3 ** made subject to an alternative license as permitted in the SGI Free
   4 ** Software License B, Version 1.1 (the "License"), the contents of this
   5 ** file are subject only to the provisions of the License. You may not use
   6 ** this file except in compliance with the License. You may obtain a copy
   7 ** of the License at Silicon Graphics, Inc., attn: Legal Services, 1600
   8 ** Amphitheatre Parkway, Mountain View, CA 94043-1351, or at:
   9 **
  10 ** http://oss.sgi.com/projects/FreeB
  11 **
  12 ** Note that, as provided in the License, the Software is distributed on an
  13 ** "AS IS" basis, with ALL EXPRESS AND IMPLIED WARRANTIES AND CONDITIONS
  14 ** DISCLAIMED, INCLUDING, WITHOUT LIMITATION, ANY IMPLIED WARRANTIES AND
  15 ** CONDITIONS OF MERCHANTABILITY, SATISFACTORY QUALITY, FITNESS FOR A
  16 ** PARTICULAR PURPOSE, AND NON-INFRINGEMENT.
  17 **
  18 ** Original Code. The Original Code is: OpenGL Sample Implementation,
  19 ** Version 1.2.1, released January 26, 2000, developed by Silicon Graphics,
  20 ** Inc. The Original Code is Copyright (c) 1991-2000 Silicon Graphics, Inc.
  21 ** Copyright in any portions created by third parties is as indicated
  22 ** elsewhere herein. All Rights Reserved.
  23 **
  24 ** Additional Notice Provisions: The application programming interfaces
  25 ** established by SGI in conjunction with the Original Code are The
  26 ** OpenGL(R) Graphics System: A Specification (Version 1.2.1), released
  27 ** April 1, 1999; The OpenGL(R) Graphics System Utility Library (Version
  28 ** 1.3), released November 4, 1998; and OpenGL(R) Graphics with the X
  29 ** Window System(R) (Version 1.3), released October 19, 1998. This software
  30 ** was created using the OpenGL(R) version 1.2.1 Sample Implementation
  31 ** published by SGI, but has not been independently verified as being
  32 ** compliant with the OpenGL(R) version 1.2.1 Specification.
  33 **
  34 */
  35 /*
  36 */
  37
  38 #include <stdlib.h>
  39 #include <stdio.h>
  40
  41
  42 static void swap(void *v[], int i, int j)
  43 {
  44   void *temp;
  45   temp = v[i];
  46   v[i] = v[j];
  47   v[j] = temp;
  48 }
  49
  50 /*as an example to use this function to
  51  *sort integers, you need to supply the function
  52  *int comp(int *i1, int *i2)
  53  *{
  54  *  if( *i1 < * i2) return -1;
  55  *  else return 1;
  56  *}
  57  *and an array of pointers to integers:
  58  * int *v[100] (allocate space for where  each v[i] points to).
  59  *then you can call:
  60  * quicksort( (void**)v, left, right, (int (*)(void *, void *))comp)
  61  */
  62 void quicksort(void *v[], int left, int right,
  63                int (*comp) (void *, void *))
  64 {
  65   int i, last;
  66   if(left >= right) /*do nothing if array contains */
  67     return;         /*fewer than two elements*/
  68
  69   swap(v, left, (left+right)/2);
  70   last = left;
  71   for(i=left+1; i<=right; i++)
  72     if((*comp)(v[i], v[left])<0)
  73       swap(v, ++last, i);
  74   swap(v, left, last);
  75   quicksort(v, left, last-1, comp);
  76   quicksort(v, last+1, right, comp);
  77 }