State machine

2 files changed, 93 insertions, 72 deletions

diff --git a/demo.c b/demo.c
index d3de027..66e3e8d 100644
--- a/demo.c
+++ b/demo.c
@@ -6,6 +6,7 @@
 #include "region-iter.c"
 
 static const pixman_rectangle32_t rects[] = {
+#if 0
     { 0, 50, 200, 100 },
     { 250, 0, 200, 100 },
     { 500, 0, 50, 350 },
@@ -20,6 +21,7 @@ static const pixman_rectangle32_t rects[] = {
     { 450, 350, 50, 50 },
     { 50, 450, 400, 50 },
     { 25, 135, 600, 25 }
+#endif
 };
 
 static corner_t *
diff --git a/region-iter.c b/region-iter.c
index 0d8d1ff..8efb395 100644
--- a/region-iter.c
+++ b/region-iter.c
@@ -11,21 +11,37 @@
 #define FALSE 0
 #endif
 
-static const pixman_box32_t sentinel =
-{
-    INT_MAX, INT_MAX, INT_MAX, INT_MAX
-};
-
 typedef struct region_iter_t region_iter_t;
 typedef struct row_t row_t;
 
+typedef enum
+{
+    FIRST,
+    MIDDLE,
+    FINAL,
+    DONE
+} state_t;
+
 struct region_iter_t
 {
-    int				y;
-    const pixman_box32_t *	first;
-    const pixman_box32_t *	last;
-    unsigned int		first_row : 1;
-    unsigned int		final_row : 1;
+    state_t			state;
+
+    union
+    {
+	struct
+	{
+	    pixman_region32_t *	region;
+	} first;
+	struct
+	{
+	    pixman_box32_t *	first;
+	    pixman_box32_t *	last;
+	} middle;
+	struct
+	{
+	    int			y1;
+	} final;
+    } u;
 };
 
 struct row_t
@@ -37,6 +53,7 @@ struct row_t
 };
 
 /* region_data manipulation */
+
 static size_t
 next_power (size_t n)
 {
@@ -77,86 +94,88 @@ region_data_append (pixman_region32_data_t *data, int n, pixman_box32_t *boxes)
 static void
 region_iter_init (region_iter_t *iter, pixman_region32_t *region)
 {
-    iter->y = INT_MIN;
-    iter->first_row = TRUE;
-    iter->final_row = FALSE;
-
-    if (!region->data)
-    {
-	iter->first = &(region->extents);
-	iter->last = &(region->extents) + 1;
-    }
-    else if (region->data->numRects == 0)
-    {
-	iter->first = &sentinel;
-	iter->last = &sentinel + 1;
-    }
-    else
-    {
-	iter->first = (pixman_box32_t *)(region->data + 1);
-	iter->last = iter->first + region->data->numRects;
-    }
+    iter->state = FIRST;
+    iter->u.first.region = region;
 }
 
 static pixman_bool_t
 region_iter_get_row (region_iter_t *iter, row_t *row)
 {
-    if (!iter->first)
-    {
-	return FALSE;
-    }
-    else if (iter->final_row)
-    {
-	row->first = NULL;
-	row->last = NULL;
-	row->y1 = iter->y;
-	row->y2 = INT_MAX;
-
-	iter->final_row = FALSE;
-	iter->first = NULL;
-
-	return TRUE;
-    }
-    else if (iter->first_row || iter->y < iter->first->y1)
+    pixman_box32_t *first;
+    pixman_box32_t *last;
+    pixman_box32_t *box;
+    
+    switch (iter->state)
     {
+    case FIRST:
+	row->y1 = INT_MIN;
 	row->first = NULL;
 	row->last = NULL;
-	row->y1 = iter->y;
-	row->y2 = iter->first->y1;
-
-	iter->y = iter->first->y1;
-	iter->first_row = FALSE;
-
-	return TRUE;
-    }
-    else
-    {
-	const pixman_box32_t *box;
-
-	for (box = iter->first; box != iter->last; box++)
+	
+	if (!iter->u.first.region->data)
+	{
+	    iter->state = MIDDLE;
+	    first = &(iter->u.first.region->extents);
+	    last = &(iter->u.first.region->extents) + 1;
+	}
+	else if (iter->u.first.region->data->numRects == 0)
+	{
+	    row->y2 = INT_MAX;
+	    iter->state = DONE;
+	}
+	else
 	{
-	    if (box->y1 != iter->y)
+	    iter->state = MIDDLE;
+	    first = (pixman_box32_t *)(iter->u.first.region->data + 1);
+	    last = first + iter->u.first.region->data->numRects;
+	}
+	
+	if (iter->state == MIDDLE)
+	{
+	    row->y2 = first->y1;
+	    iter->u.middle.first = first;
+	    iter->u.middle.last = last;
+	}
+	break;
+	
+    case MIDDLE:
+	assert (iter->u.middle.last - iter->u.middle.first > 0);
+	
+	for (box = iter->u.middle.first; box != iter->u.middle.last; ++box)
+	{
+	    if (box->y1 != iter->u.middle.first->y1)
 		break;
 	}
-
-	row->first = iter->first;
+	
+	row->y1 = iter->u.middle.first->y1;
+	row->y2 = iter->u.middle.first->y2;
+	row->first = iter->u.middle.first;
 	row->last = box;
-	row->y1 = iter->y;
-	row->y2 = iter->first->y2;
-
-	iter->y = iter->first->y2;
-
-	if (box == iter->last)
+	
+	if (box != iter->u.middle.last)
 	{
-	    iter->final_row = TRUE;
+	    iter->u.middle.first = box;
 	}
 	else
 	{
-	    iter->first = box;
+	    iter->state = FINAL;
+	    iter->u.final.y1 = row->y2;
 	}
-
-	return TRUE;
+	break;
+	
+    case FINAL:
+	row->first = NULL;
+	row->last = NULL;
+	row->y1 = iter->u.final.y1;
+	row->y2 = INT_MAX;
+	iter->state = DONE;
+	break;
+	
+    case DONE:
+	return FALSE;
     }
+
+    return TRUE;
 }
 
 /* Overlapped iter */