struct VoronoiDiagramGenerator::Halfedge * VoronoiDiagramGenerator::ELleftbnd(struct Point *p)
{
int i, bucket;
struct Halfedge *he;
/* Use hash table to get close to desired halfedge */
bucket = (int)((p->x - xmin)/deltax * ELhashsize); //use the hash function to find the place in the hash map that this HalfEdge should be
if(bucket<0) bucket =0; //make sure that the bucket position in within the range of the hash array
if(bucket>=ELhashsize) bucket = ELhashsize - 1;
he = ELgethash(bucket);
if(he == (struct Halfedge *) NULL) //if the HE isn't found, search backwards and forwards in the hash map for the first non-null entry
{
for(i=1; 1 ; i += 1)
{
if ((he=ELgethash(bucket-i)) != (struct Halfedge *) NULL)
break;
if ((he=ELgethash(bucket+i)) != (struct Halfedge *) NULL)
break;
};
totalsearch += i;
};
ntry += 1;
/* Now search linear list of halfedges for the correct one */
if (he==ELleftend || (he != ELrightend && right_of(he,p)))
{
do
{
he = he -> ELright;
} while (he!=ELrightend && right_of(he,p)); //keep going right on the list until either the end is reached, or you find the 1st edge which the point
he = he -> ELleft; //isn't to the right of
}
else //if the point is to the left of the HalfEdge, then search left for the HE just to the left of the point
do
{
he = he -> ELleft;
} while (he!=ELleftend && !right_of(he,p));
/* Update hash table and reference counts */
if(bucket > 0 && bucket <ELhashsize-1)
{
if(ELhash[bucket] != (struct Halfedge *) NULL)
{
ELhash[bucket] -> ELrefcnt -= 1;
}
ELhash[bucket] = he;
ELhash[bucket] -> ELrefcnt += 1;
};
return (he);
}
void cover_column(toroid_header_t* c)
{
assert (finalized_m);
right_of(c)->left_m = left_of(c);
left_of(c)->right_m = right_of(c);
for (toroid_node_t* i(down_of(c)); i != c; i = down_of(i))
{
for (toroid_node_t* j(right_of(i)); j != i; j = right_of(j))
{
down_of(j)->up_m = up_of(j);
up_of(j)->down_m = down_of(j);
--(column_of(j)->size_m);
}
}
}
void uncover_column(toroid_header_t* c)
{
assert (finalized_m);
for (toroid_node_t* i(up_of(c)); i != c; i = up_of(i))
{
for (toroid_node_t* j(left_of(i)); j != i; j = left_of(j))
{
++(column_of(j)->size_m);
down_of(j)->up_m = j;
up_of(j)->down_m = j;
}
}
right_of(c)->left_m = c;
left_of(c)->right_m = c;
}
static int cptclip_z_id(cpt_t* cpt,
double zleft,
double zright,
bool (*left_of)(double,double),
bool (*right_of)(double,double))
{
cpt_seg_t* seg;
/*
pop segments from the left until one of them
intersects the requested interval
*/
while ((seg = cpt_pop(cpt)) != NULL)
{
if (right_of(seg->rsmp.val,zleft))
break;
cpt_seg_destroy(seg);
}
if (seg)
{
/*
if this segment is not completely inside the
requested interval then clip it to the interval
*/
if (left_of(seg->lsmp.val,zleft))
{
fill_t fill;
double z =
(zleft - seg->lsmp.val)/
(seg->rsmp.val - seg->lsmp.val);
if (fill_interpolate(z,
seg->lsmp.fill,
seg->rsmp.fill,
cpt->model,
&fill) != 0)
{
btrace("fill interpolation failed");
return 1;
}
seg->lsmp.fill = fill;
seg->lsmp.val = zleft;
}
/*
push the (possibly modified) segment back to
where it came
*/
cpt_prepend(seg,cpt);
}
/* likewise on the right */
while ((seg = cpt_shift(cpt)) != NULL)
{
if (left_of(seg->lsmp.val,zright))
break;
cpt_seg_destroy(seg);
}
if (seg)
{
if (right_of(seg->rsmp.val,zright))
{
fill_t fill;
double z =
(zright - seg->lsmp.val)/
(seg->rsmp.val - seg->lsmp.val);
if (fill_interpolate(z,
seg->lsmp.fill,
seg->rsmp.fill,
cpt->model,
&fill) != 0)
{
btrace("fill interpolation failed");
return 1;
}
seg->rsmp.fill = fill;
seg->rsmp.val = zright;
}
cpt_append(seg,cpt);
}
return 0;
}
