src/glu/sgi/libtess/priorityq-heap.c

   1 /*
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   3  * Copyright (C) 1991-2000 Silicon Graphics, Inc. All Rights Reserved.
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   5  * Permission is hereby granted, free of charge, to any person obtaining a
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  10  * Software is furnished to do so, subject to the following conditions:
  11  *
  12  * The above copyright notice including the dates of first publication and
  13  * either this permission notice or a reference to
  14  * http://oss.sgi.com/projects/FreeB/
  15  * shall be included in all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  18  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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  26  * shall not be used in advertising or otherwise to promote the sale, use or
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  29  */
  30 /*
  31 ** Author: Eric Veach, July 1994.
  32 **
  33 */
  34
  35 #include <stddef.h>
  36 #include <assert.h>
  37 #include "priorityq-heap.h"
  38 #include "memalloc.h"
  39
  40 #define INIT_SIZE       32
  41
  42 #define TRUE 1
  43 #define FALSE 0
  44
  45 #ifdef FOR_TRITE_TEST_PROGRAM
  46 #define LEQ(x,y)        (*pq->leq)(x,y)
  47 #else
  48 /* Violates modularity, but a little faster */
  49 #include "geom.h"
  50 #define LEQ(x,y)        VertLeq((GLUvertex *)x, (GLUvertex *)y)
  51 #endif
  52
  53 /* really __gl_pqHeapNewPriorityQ */
  54 PriorityQ *pqNewPriorityQ( int (*leq)(PQkey key1, PQkey key2) )
  55 {
  56   PriorityQ *pq = (PriorityQ *)memAlloc( sizeof( PriorityQ ));
  57   if (pq == NULL) return NULL;
  58
  59   pq->size = 0;
  60   pq->max = INIT_SIZE;
  61   pq->nodes = (PQnode *)memAlloc( (INIT_SIZE + 1) * sizeof(pq->nodes[0]) );
  62   if (pq->nodes == NULL) {
  63      memFree(pq);
  64      return NULL;
  65   }
  66
  67   pq->handles = (PQhandleElem *)memAlloc( (INIT_SIZE + 1) * sizeof(pq->handles[0]) );
  68   if (pq->handles == NULL) {
  69      memFree(pq->nodes);
  70      memFree(pq);
  71      return NULL;
  72   }
  73
  74   pq->initialized = FALSE;
  75   pq->freeList = 0;
  76   pq->leq = leq;
  77
  78   pq->nodes[1].handle = 1;      /* so that Minimum() returns NULL */
  79   pq->handles[1].key = NULL;
  80   return pq;
  81 }
  82
  83 /* really __gl_pqHeapDeletePriorityQ */
  84 void pqDeletePriorityQ( PriorityQ *pq )
  85 {
  86   memFree( pq->handles );
  87   memFree( pq->nodes );
  88   memFree( pq );
  89 }
  90
  91
  92 static void FloatDown( PriorityQ *pq, long curr )
  93 {
  94   PQnode *n = pq->nodes;
  95   PQhandleElem *h = pq->handles;
  96   PQhandle hCurr, hChild;
  97   long child;
  98
  99   hCurr = n[curr].handle;
 100   for( ;; ) {
 101     child = curr << 1;
 102     if( child < pq->size && LEQ( h[n[child+1].handle].key,
 103                                  h[n[child].handle].key )) {
 104       ++child;
 105     }
 106
 107     assert(child <= pq->max);
 108
 109     hChild = n[child].handle;
 110     if( child > pq->size || LEQ( h[hCurr].key, h[hChild].key )) {
 111       n[curr].handle = hCurr;
 112       h[hCurr].node = curr;
 113       break;
 114     }
 115     n[curr].handle = hChild;
 116     h[hChild].node = curr;
 117     curr = child;
 118   }
 119 }
 120
 121
 122 static void FloatUp( PriorityQ *pq, long curr )
 123 {
 124   PQnode *n = pq->nodes;
 125   PQhandleElem *h = pq->handles;
 126   PQhandle hCurr, hParent;
 127   long parent;
 128
 129   hCurr = n[curr].handle;
 130   for( ;; ) {
 131     parent = curr >> 1;
 132     hParent = n[parent].handle;
 133     if( parent == 0 || LEQ( h[hParent].key, h[hCurr].key )) {
 134       n[curr].handle = hCurr;
 135       h[hCurr].node = curr;
 136       break;
 137     }
 138     n[curr].handle = hParent;
 139     h[hParent].node = curr;
 140     curr = parent;
 141   }
 142 }
 143
 144 /* really __gl_pqHeapInit */
 145 void pqInit( PriorityQ *pq )
 146 {
 147   long i;
 148
 149   /* This method of building a heap is O(n), rather than O(n lg n). */
 150
 151   for( i = pq->size; i >= 1; --i ) {
 152     FloatDown( pq, i );
 153   }
 154   pq->initialized = TRUE;
 155 }
 156
 157 /* really __gl_pqHeapInsert */
 158 /* returns LONG_MAX iff out of memory */
 159 PQhandle pqInsert( PriorityQ *pq, PQkey keyNew )
 160 {
 161   long curr;
 162   PQhandle free;
 163
 164   curr = ++ pq->size;
 165   if( (curr*2) > pq->max ) {
 166     PQnode *saveNodes= pq->nodes;
 167     PQhandleElem *saveHandles= pq->handles;
 168
 169     /* If the heap overflows, double its size. */
 170     pq->max <<= 1;
 171     pq->nodes = (PQnode *)memRealloc( pq->nodes,
 172                                      (size_t)
 173                                      ((pq->max + 1) * sizeof( pq->nodes[0] )));
 174     if (pq->nodes == NULL) {
 175        pq->nodes = saveNodes;   /* restore ptr to free upon return */
 176        return LONG_MAX;
 177     }
 178     pq->handles = (PQhandleElem *)memRealloc( pq->handles,
 179                                              (size_t)
 180                                               ((pq->max + 1) *
 181                                                sizeof( pq->handles[0] )));
 182     if (pq->handles == NULL) {
 183        pq->handles = saveHandles; /* restore ptr to free upon return */
 184        return LONG_MAX;
 185     }
 186   }
 187
 188   if( pq->freeList == 0 ) {
 189     free = curr;
 190   } else {
 191     free = pq->freeList;
 192     pq->freeList = pq->handles[free].node;
 193   }
 194
 195   pq->nodes[curr].handle = free;
 196   pq->handles[free].node = curr;
 197   pq->handles[free].key = keyNew;
 198
 199   if( pq->initialized ) {
 200     FloatUp( pq, curr );
 201   }
 202   assert(free != LONG_MAX);
 203   return free;
 204 }
 205
 206 /* really __gl_pqHeapExtractMin */
 207 PQkey pqExtractMin( PriorityQ *pq )
 208 {
 209   PQnode *n = pq->nodes;
 210   PQhandleElem *h = pq->handles;
 211   PQhandle hMin = n[1].handle;
 212   PQkey min = h[hMin].key;
 213
 214   if( pq->size > 0 ) {
 215     n[1].handle = n[pq->size].handle;
 216     h[n[1].handle].node = 1;
 217
 218     h[hMin].key = NULL;
 219     h[hMin].node = pq->freeList;
 220     pq->freeList = hMin;
 221
 222     if( -- pq->size > 0 ) {
 223       FloatDown( pq, 1 );
 224     }
 225   }
 226   return min;
 227 }
 228
 229 /* really __gl_pqHeapDelete */
 230 void pqDelete( PriorityQ *pq, PQhandle hCurr )
 231 {
 232   PQnode *n = pq->nodes;
 233   PQhandleElem *h = pq->handles;
 234   long curr;
 235
 236   assert( hCurr >= 1 && hCurr <= pq->max && h[hCurr].key != NULL );
 237
 238   curr = h[hCurr].node;
 239   n[curr].handle = n[pq->size].handle;
 240   h[n[curr].handle].node = curr;
 241
 242   if( curr <= -- pq->size ) {
 243     if( curr <= 1 || LEQ( h[n[curr>>1].handle].key, h[n[curr].handle].key )) {
 244       FloatDown( pq, curr );
 245     } else {
 246       FloatUp( pq, curr );
 247     }
 248   }
 249   h[hCurr].key = NULL;
 250   h[hCurr].node = pq->freeList;
 251   pq->freeList = hCurr;
 252 }