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Add ts_tree_cursor_goto_first_child_for_point function

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This function (and the similar `ts_tree_cursor_goto_first_child_for_byte`)
allows you to efficiently seek the tree cursor to a given position,
exploiting the tree's internal balancing, without having to visit
all of the preceding siblings of each node.
This commit is contained in:
Max Brunsfeld 2021-05-27 12:30:17 -07:00
parent 036aceed57
commit 919e9745a6
5 changed files with 166 additions and 6 deletions
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41
lib/src/tree_cursor.c
View file

@ -159,10 +159,43 @@ int64_t ts_tree_cursor_goto_first_child_for_byte(TSTreeCursor *_self, uint32_t g
}
} while (did_descend);
if (self->stack.size > initial_size &&
ts_tree_cursor_goto_next_sibling((TSTreeCursor *)self)) {
return visible_child_index;
}
self->stack.size = initial_size;
return -1;
}
int64_t ts_tree_cursor_goto_first_child_for_point(TSTreeCursor *_self, TSPoint goal_point) {
TreeCursor *self = (TreeCursor *)_self;
uint32_t initial_size = self->stack.size;
uint32_t visible_child_index = 0;
bool did_descend;
do {
did_descend = false;
bool visible;
TreeCursorEntry entry;
CursorChildIterator iterator = ts_tree_cursor_iterate_children(self);
while (ts_tree_cursor_child_iterator_next(&iterator, &entry, &visible)) {
TSPoint end_point = point_add(entry.position.extent, ts_subtree_size(*entry.subtree).extent);
bool at_goal = point_gt(end_point, goal_point);
uint32_t visible_child_count = ts_subtree_visible_child_count(*entry.subtree);
if (at_goal) {
if (visible) {
array_push(&self->stack, entry);
return visible_child_index;
}
if (visible_child_count > 0) {
array_push(&self->stack, entry);
did_descend = true;
break;
}
} else if (visible) {
visible_child_index++;
} else {
visible_child_index += visible_child_count;
}
}
} while (did_descend);
self->stack.size = initial_size;
return -1;