fdo-mirrors/cairo
1
0
Fork 0
mirror of https://gitlab.freedesktop.org/cairo/cairo.git synced 2026-05-08 07:58:02 +02:00
Code Issues Projects Releases Packages Wiki Activity Actions

bo-rectangular: Correctly mergesort a doubly-linked list

Browse source 
Saves having to fixup the pointers afterwards by only having to update
them on the list boundaries during merge.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
This commit is contained in:
Chris Wilson 2011-08-09 17:57:43 +01:00
parent a4e4e2bdd7
commit 17e34b6eab
1 changed files with 13 additions and 12 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

25
src/cairo-bentley-ottmann-rectangular.c
View file

@ -326,16 +326,15 @@ edge_start_or_continue_box (sweep_line_t *sweep_line,
static edge_t *
merge_sorted_edges (edge_t *head_a, edge_t *head_b)
{
edge_t *head, **next;
edge_t *head, **next, *prev;
int32_t x;
if (head_a == NULL)
return head_b;
prev = head_a->prev;
next = &head;
if (head_a->x <= head_b->x) {
head = head_a;
} else {
head_b->prev = prev;
head = head_b;
goto start_with_b;
}
@ -343,10 +342,12 @@ merge_sorted_edges (edge_t *head_a, edge_t *head_b)
do {
x = head_b->x;
while (head_a != NULL && head_a->x <= x) {
prev = head_a;
next = &head_a->next;
head_a = head_a->next;
}
head_b->prev = prev;
*next = head_b;
if (head_a == NULL)
return head;
@ -354,10 +355,12 @@ merge_sorted_edges (edge_t *head_a, edge_t *head_b)
start_with_b:
x = head_a->x;
while (head_b != NULL && head_b->x <= x) {
prev = head_b;
next = &head_b->next;
head_b = head_b->next;
}
head_a->prev = prev;
*next = head_a;
if (head_b == NULL)
return head;
@ -402,19 +405,17 @@ sort_edges (edge_t *list,
head_other->next = NULL;
} else {
*head_out = head_other;
head_other->prev = list->prev;
head_other->next = list;
list->prev = head_other;
list->next = NULL;
}
for (i = 0; i < level && remaining; i++) {
/* Extract a sorted list of the same size as *head_out
* (2^(i+1) elements) from the list of remaining elements. */
remaining = sort_edges (remaining, i, &head_other);
*head_out = merge_sorted_edges (*head_out, head_other);
}
/* *head_out now contains (at most) 2^(level+1) elements. */
return remaining;
}
@ -446,10 +447,6 @@ active_edges_insert (sweep_line_t *sweep)
sweep->cursor = sweep->insert;
sweep->insert = NULL;
sweep->insert_x = INT_MAX;
/* update links within sort? */
for (edge = prev->next; edge; prev = edge, edge = edge->next)
edge->prev = prev;
}
static inline void
@ -587,8 +584,12 @@ sweep_line_delete (sweep_line_t *sweep, rectangle_t *rectangle)
static inline void
sweep_line_insert (sweep_line_t *sweep, rectangle_t *rectangle)
{
if (sweep->insert)
sweep->insert->prev = &rectangle->right;
rectangle->right.next = sweep->insert;
rectangle->right.prev = &rectangle->left;
rectangle->left.next = &rectangle->right;
rectangle->left.prev = NULL;
sweep->insert = &rectangle->left;
if (rectangle->left.x < sweep->insert_x)
sweep->insert_x = rectangle->left.x;