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Improved algorithm of Rope::append()

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It doesn't use an intermediate conversion to a string anymore, and should
execute in O(log N) as long as the right-hand rope is equal length or
smaller than the left.

It may also be O(log N) for the left-hand rope being smaller, but that
depends on whether the rebalance code executes in O(log N) time when
the left and right hand side are individually balanced.  I haven't
analysed it yet, so dunno.
This commit is contained in:
Nathan Vegdahl 2015-02-17 23:10:38 -08:00
parent d26c95ab1d
commit 535f219c41
1 changed files with 11 additions and 5 deletions
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16
src/buffer/rope.rs
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@ -200,11 +200,17 @@ impl Rope {
/// Appends another rope to the end of this one, consuming the other rope.
pub fn append(&mut self, rope: Rope) {
// TODO: make more efficient. Converting to a string and then
// inserting is pretty slow...
let s = rope.to_string();
let gc = self.grapheme_count();
self.insert_text_at_grapheme_index(s.as_slice(), gc);
if self.tree_height <= rope.tree_height || self.is_leaf() {
let mut temp_rope = Box::new(Rope::new());
mem::swap(self, &mut (*temp_rope));
self.data = RopeData::Branch(temp_rope, Box::new(rope));
}
else if let RopeData::Branch(_, ref mut right) = self.data {
right.append(rope);
}
self.update_stats();
self.rebalance();
}
/// Makes a copy of the rope as a string