priority_queue: replace copies with moves
This commit is contained in:
parent
6c433f22a1
commit
b3463ea657
|
@ -1,12 +1,18 @@
|
|||
|
||||
/// A priority queue implemented with a binary heap
|
||||
use core::cmp::Ord;
|
||||
use ptr::addr_of;
|
||||
|
||||
pub struct PriorityQueue <T: Copy Ord>{
|
||||
#[abi = "rust-intrinsic"]
|
||||
extern "C" mod rusti {
|
||||
fn move_val_init<T>(dst: &mut T, -src: T);
|
||||
}
|
||||
|
||||
pub struct PriorityQueue <T: Ord>{
|
||||
priv data: ~[T],
|
||||
}
|
||||
|
||||
impl <T: Copy Ord> PriorityQueue<T> {
|
||||
impl <T: Ord> PriorityQueue<T> {
|
||||
/// Returns the greatest item in the queue - fails if empty
|
||||
pure fn top(&self) -> &self/T { &self.data[0] }
|
||||
|
||||
|
@ -97,26 +103,33 @@ impl <T: Copy Ord> PriorityQueue<T> {
|
|||
q
|
||||
}
|
||||
|
||||
priv fn siftup(&mut self, start: uint, pos: uint) {
|
||||
// The implementations of siftup and siftdown use unsafe blocks in order to
|
||||
// move an element out of the vector (leaving behind a junk element), shift
|
||||
// along the others and move it back into the vector over the junk element.
|
||||
// This reduces the constant factor compared to using swaps, which involves
|
||||
// twice as many moves.
|
||||
|
||||
priv fn siftup(&mut self, start: uint, pos: uint) unsafe {
|
||||
let mut pos = pos;
|
||||
let new = self.data[pos];
|
||||
let new = move *addr_of(&self.data[pos]);
|
||||
|
||||
while pos > start {
|
||||
let parent = (pos - 1) >> 1;
|
||||
if new > self.data[parent] {
|
||||
self.data[pos] = self.data[parent];
|
||||
rusti::move_val_init(&mut self.data[pos],
|
||||
move *addr_of(&self.data[parent]));
|
||||
pos = parent;
|
||||
loop
|
||||
}
|
||||
break
|
||||
}
|
||||
self.data[pos] = new;
|
||||
rusti::move_val_init(&mut self.data[pos], move new);
|
||||
}
|
||||
|
||||
priv fn siftdown_range(&mut self, pos: uint, end: uint) {
|
||||
priv fn siftdown_range(&mut self, pos: uint, end: uint) unsafe {
|
||||
let mut pos = pos;
|
||||
let start = pos;
|
||||
let new = self.data[pos];
|
||||
let new = move *addr_of(&self.data[pos]);
|
||||
|
||||
let mut child = 2 * pos + 1;
|
||||
while child < end {
|
||||
|
@ -124,11 +137,12 @@ impl <T: Copy Ord> PriorityQueue<T> {
|
|||
if right < end && !(self.data[child] > self.data[right]) {
|
||||
child = right;
|
||||
}
|
||||
self.data[pos] = self.data[child];
|
||||
rusti::move_val_init(&mut self.data[pos],
|
||||
move *addr_of(&self.data[child]));
|
||||
pos = child;
|
||||
child = 2 * pos + 1;
|
||||
}
|
||||
self.data[pos] = new;
|
||||
rusti::move_val_init(&mut self.data[pos], move new);
|
||||
self.siftup(start, pos);
|
||||
}
|
||||
|
||||
|
|
Loading…
Reference in New Issue