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      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 ** Author: Eric Veach, July 1994.
     37 **
     38 ** $Date$ $Revision$
     39 ** $Header: //depot/main/gfx/lib/glu/libtess/priorityq-heap.c#5 $
     40 */
     41 
     42 #include <stddef.h>
     43 #include <assert.h>
     44 #include <limits.h>
     45 #include "priorityq-heap.h"
     46 #include "memalloc.h"
     47 
     48 #define INIT_SIZE	32
     49 
     50 #define TRUE 1
     51 #define FALSE 0
     52 
     53 #ifdef FOR_TRITE_TEST_PROGRAM
     54 #define LEQ(x,y)	(*pq->leq)(x,y)
     55 #else
     56 /* Violates modularity, but a little faster */
     57 #include "geom.h"
     58 #define LEQ(x,y)	VertLeq((GLUvertex *)x, (GLUvertex *)y)
     59 #endif
     60 
     61 /* really __gl_pqHeapNewPriorityQ */
     62 PriorityQ *pqNewPriorityQ( int (*leq)(PQkey key1, PQkey key2) )
     63 {
     64   PriorityQ *pq = (PriorityQ *)memAlloc( sizeof( PriorityQ ));
     65   if (pq == NULL) return NULL;
     66 
     67   pq->size = 0;
     68   pq->max = INIT_SIZE;
     69   pq->nodes = (PQnode *)memAlloc( (INIT_SIZE + 1) * sizeof(pq->nodes[0]) );
     70   if (pq->nodes == NULL) {
     71      memFree(pq);
     72      return NULL;
     73   }
     74 
     75   pq->handles = (PQhandleElem *)memAlloc( (INIT_SIZE + 1) * sizeof(pq->handles[0]) );
     76   if (pq->handles == NULL) {
     77      memFree(pq->nodes);
     78      memFree(pq);
     79      return NULL;
     80   }
     81 
     82   pq->initialized = FALSE;
     83   pq->freeList = 0;
     84   pq->leq = leq;
     85 
     86   pq->nodes[1].handle = 1;	/* so that Minimum() returns NULL */
     87   pq->handles[1].key = NULL;
     88   return pq;
     89 }
     90 
     91 /* really __gl_pqHeapDeletePriorityQ */
     92 void pqDeletePriorityQ( PriorityQ *pq )
     93 {
     94   memFree( pq->handles );
     95   memFree( pq->nodes );
     96   memFree( pq );
     97 }
     98 
     99 
    100 static void FloatDown( PriorityQ *pq, long curr )
    101 {
    102   PQnode *n = pq->nodes;
    103   PQhandleElem *h = pq->handles;
    104   PQhandle hCurr, hChild;
    105   long child;
    106 
    107   hCurr = n[curr].handle;
    108   for( ;; ) {
    109     child = curr << 1;
    110     if( child < pq->size && LEQ( h[n[child+1].handle].key,
    111 				 h[n[child].handle].key )) {
    112       ++child;
    113     }
    114 
    115     assert(child <= pq->max);
    116 
    117     hChild = n[child].handle;
    118     if( child > pq->size || LEQ( h[hCurr].key, h[hChild].key )) {
    119       n[curr].handle = hCurr;
    120       h[hCurr].node = curr;
    121       break;
    122     }
    123     n[curr].handle = hChild;
    124     h[hChild].node = curr;
    125     curr = child;
    126   }
    127 }
    128 
    129 
    130 static void FloatUp( PriorityQ *pq, long curr )
    131 {
    132   PQnode *n = pq->nodes;
    133   PQhandleElem *h = pq->handles;
    134   PQhandle hCurr, hParent;
    135   long parent;
    136 
    137   hCurr = n[curr].handle;
    138   for( ;; ) {
    139     parent = curr >> 1;
    140     hParent = n[parent].handle;
    141     if( parent == 0 || LEQ( h[hParent].key, h[hCurr].key )) {
    142       n[curr].handle = hCurr;
    143       h[hCurr].node = curr;
    144       break;
    145     }
    146     n[curr].handle = hParent;
    147     h[hParent].node = curr;
    148     curr = parent;
    149   }
    150 }
    151 
    152 /* really __gl_pqHeapInit */
    153 void pqInit( PriorityQ *pq )
    154 {
    155   long i;
    156 
    157   /* This method of building a heap is O(n), rather than O(n lg n). */
    158 
    159   for( i = pq->size; i >= 1; --i ) {
    160     FloatDown( pq, i );
    161   }
    162   pq->initialized = TRUE;
    163 }
    164 
    165 /* really __gl_pqHeapInsert */
    166 /* returns LONG_MAX iff out of memory */
    167 PQhandle pqInsert( PriorityQ *pq, PQkey keyNew )
    168 {
    169   long curr;
    170   PQhandle free;
    171 
    172   curr = ++ pq->size;
    173   if( (curr*2) > pq->max ) {
    174     PQnode *saveNodes= pq->nodes;
    175     PQhandleElem *saveHandles= pq->handles;
    176 
    177     /* If the heap overflows, double its size. */
    178     pq->max <<= 1;
    179     pq->nodes = (PQnode *)memRealloc( pq->nodes,
    180 				     (size_t)
    181 				     ((pq->max + 1) * sizeof( pq->nodes[0] )));
    182     if (pq->nodes == NULL) {
    183        pq->nodes = saveNodes;	/* restore ptr to free upon return */
    184        return LONG_MAX;
    185     }
    186     pq->handles = (PQhandleElem *)memRealloc( pq->handles,
    187 			                     (size_t)
    188 			                      ((pq->max + 1) *
    189 					       sizeof( pq->handles[0] )));
    190     if (pq->handles == NULL) {
    191        pq->handles = saveHandles; /* restore ptr to free upon return */
    192        return LONG_MAX;
    193     }
    194   }
    195 
    196   if( pq->freeList == 0 ) {
    197     free = curr;
    198   } else {
    199     free = pq->freeList;
    200     pq->freeList = pq->handles[free].node;
    201   }
    202 
    203   pq->nodes[curr].handle = free;
    204   pq->handles[free].node = curr;
    205   pq->handles[free].key = keyNew;
    206 
    207   if( pq->initialized ) {
    208     FloatUp( pq, curr );
    209   }
    210   assert(free != LONG_MAX);
    211   return free;
    212 }
    213 
    214 /* really __gl_pqHeapExtractMin */
    215 PQkey pqExtractMin( PriorityQ *pq )
    216 {
    217   PQnode *n = pq->nodes;
    218   PQhandleElem *h = pq->handles;
    219   PQhandle hMin = n[1].handle;
    220   PQkey min = h[hMin].key;
    221 
    222   if( pq->size > 0 ) {
    223     n[1].handle = n[pq->size].handle;
    224     h[n[1].handle].node = 1;
    225 
    226     h[hMin].key = NULL;
    227     h[hMin].node = pq->freeList;
    228     pq->freeList = hMin;
    229 
    230     if( -- pq->size > 0 ) {
    231       FloatDown( pq, 1 );
    232     }
    233   }
    234   return min;
    235 }
    236 
    237 /* really __gl_pqHeapDelete */
    238 void pqDelete( PriorityQ *pq, PQhandle hCurr )
    239 {
    240   PQnode *n = pq->nodes;
    241   PQhandleElem *h = pq->handles;
    242   long curr;
    243 
    244   assert( hCurr >= 1 && hCurr <= pq->max && h[hCurr].key != NULL );
    245 
    246   curr = h[hCurr].node;
    247   n[curr].handle = n[pq->size].handle;
    248   h[n[curr].handle].node = curr;
    249 
    250   if( curr <= -- pq->size ) {
    251     if( curr <= 1 || LEQ( h[n[curr>>1].handle].key, h[n[curr].handle].key )) {
    252       FloatDown( pq, curr );
    253     } else {
    254       FloatUp( pq, curr );
    255     }
    256   }
    257   h[hCurr].key = NULL;
    258   h[hCurr].node = pq->freeList;
    259   pq->freeList = hCurr;
    260 }
    261