mirror of
https://github.com/italicsjenga/agb.git
synced 2024-12-24 00:31:34 +11:00
Use MaybeUninit to reduce memory usage by half
This commit is contained in:
Gwilym Kuiper
parent
cd9798d01f
commit
ee983ef7ec
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@ -1,7 +1,9 @@
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use alloc::vec::Vec;
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use core::{
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hash::{BuildHasher, BuildHasherDefault, Hash, Hasher},
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iter, mem,
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iter,
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mem::{self, MaybeUninit},
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ptr,
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};
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use rustc_hash::FxHasher;
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@ -10,27 +12,118 @@ type HashType = u32;
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struct Node<K, V> {
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hash: HashType,
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// distance_to_initial_bucket = -1 => key and value are uninit.
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// distance_to_initial_bucket >= 0 => key and value are init
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distance_to_initial_bucket: i32,
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key: K,
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value: V,
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key: MaybeUninit<K>,
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value: MaybeUninit<V>,
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}
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impl<K, V> Node<K, V> {
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fn with_new_key_value(self, new_key: K, new_value: V) -> (Self, V) {
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fn with_new_key_value(self, new_key: K, new_value: V) -> (Self, Option<V>) {
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(
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Self {
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hash: self.hash,
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distance_to_initial_bucket: self.distance_to_initial_bucket,
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key: new_key,
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value: new_value,
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key: MaybeUninit::new(new_key),
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value: MaybeUninit::new(new_value),
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},
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self.value,
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self.get_owned_value(),
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)
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}
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fn new() -> Self {
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Self {
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hash: 0,
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distance_to_initial_bucket: -1,
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key: MaybeUninit::uninit(),
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value: MaybeUninit::uninit(),
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}
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}
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fn new_with(key: K, value: V, hash: HashType) -> Self {
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Self {
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hash,
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distance_to_initial_bucket: 0,
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key: MaybeUninit::new(key),
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value: MaybeUninit::new(value),
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}
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}
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fn get_value_ref(&self) -> Option<&V> {
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if self.has_value() {
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Some(unsafe { self.value.assume_init_ref() })
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} else {
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None
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}
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}
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fn get_value_mut(&mut self) -> Option<&mut V> {
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if self.has_value() {
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Some(unsafe { self.value.assume_init_mut() })
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} else {
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None
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}
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}
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fn get_owned_value(mut self) -> Option<V> {
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if self.has_value() {
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let value = mem::replace(&mut self.value, MaybeUninit::uninit());
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self.distance_to_initial_bucket = -1;
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Some(unsafe { value.assume_init() })
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} else {
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None
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}
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}
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fn key_ref(&self) -> Option<&K> {
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if self.distance_to_initial_bucket >= 0 {
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Some(unsafe { self.key.assume_init_ref() })
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} else {
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None
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}
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}
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fn has_value(&self) -> bool {
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self.distance_to_initial_bucket >= 0
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}
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fn take(&mut self) -> Self {
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mem::take(self)
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}
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fn take_key_value(&mut self) -> Option<(K, V, HashType)> {
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if self.has_value() {
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let key = mem::replace(&mut self.key, MaybeUninit::uninit());
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let value = mem::replace(&mut self.value, MaybeUninit::uninit());
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self.distance_to_initial_bucket = -1;
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Some(unsafe { (key.assume_init(), value.assume_init(), self.hash) })
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} else {
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None
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}
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}
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}
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impl<K, V> Drop for Node<K, V> {
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fn drop(&mut self) {
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if self.distance_to_initial_bucket >= 0 {
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unsafe { ptr::drop_in_place(self.key.as_mut_ptr()) };
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unsafe { ptr::drop_in_place(self.value.as_mut_ptr()) };
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}
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}
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}
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impl<K, V> Default for Node<K, V> {
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fn default() -> Self {
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Self::new()
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}
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}
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struct NodeStorage<K, V> {
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nodes: Vec<Option<Node<K, V>>>,
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nodes: Vec<Node<K, V>>,
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max_distance_to_initial_bucket: i32,
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number_of_items: usize,
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@ -41,7 +134,7 @@ impl<K, V> NodeStorage<K, V> {
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assert!(capacity.is_power_of_two(), "Capacity must be a power of 2");
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Self {
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nodes: iter::repeat_with(|| None).take(capacity).collect(),
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nodes: iter::repeat_with(Default::default).take(capacity).collect(),
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max_distance_to_initial_bucket: 0,
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number_of_items: 0,
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}
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@ -63,26 +156,21 @@ impl<K, V> NodeStorage<K, V> {
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self.len()
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);
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let mut new_node = Node {
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hash,
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distance_to_initial_bucket: 0,
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key,
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value,
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};
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let mut new_node = Node::new_with(key, value, hash);
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loop {
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let location = fast_mod(
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self.capacity(),
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new_node.hash + new_node.distance_to_initial_bucket as HashType,
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);
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let current_node = self.nodes[location].as_mut();
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let current_node = &mut self.nodes[location];
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if let Some(current_node) = current_node {
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if current_node.has_value() {
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if current_node.distance_to_initial_bucket <= new_node.distance_to_initial_bucket {
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mem::swap(&mut new_node, current_node);
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}
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} else {
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self.nodes[location] = Some(new_node);
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self.nodes[location] = new_node;
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break;
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}
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@ -97,34 +185,23 @@ impl<K, V> NodeStorage<K, V> {
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fn remove_from_location(&mut self, location: usize) -> V {
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let mut current_location = location;
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self.number_of_items -= 1;
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let result = loop {
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loop {
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let next_location = fast_mod(self.capacity(), (current_location + 1) as HashType);
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// if the next node is empty, or the next location has 0 distance to initial bucket then
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// we can clear the current node
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if self.nodes[next_location].is_none()
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|| self.nodes[next_location]
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.as_ref()
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.unwrap()
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.distance_to_initial_bucket
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== 0
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if !self.nodes[next_location].has_value()
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|| self.nodes[next_location].distance_to_initial_bucket == 0
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{
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break self.nodes[current_location].take().unwrap();
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return self.nodes[current_location].take_key_value().unwrap().1;
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}
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if self.nodes[next_location].is_none() {}
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self.nodes.swap(current_location, next_location);
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self.nodes[current_location]
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.as_mut()
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.unwrap()
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.distance_to_initial_bucket -= 1;
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self.nodes[current_location].distance_to_initial_bucket -= 1;
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current_location = next_location;
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};
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self.number_of_items -= 1;
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result.value
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}
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}
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fn get_location(&self, key: &K, hash: HashType) -> Option<usize>
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@ -138,8 +215,8 @@ impl<K, V> NodeStorage<K, V> {
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);
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let node = &self.nodes[location];
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if let Some(node) = node {
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if &node.key == key {
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if let Some(node_key_ref) = node.key_ref() {
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if node_key_ref == key {
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return Some(location);
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}
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} else {
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@ -188,8 +265,10 @@ impl<K, V> HashMap<K, V> {
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let mut new_node_storage = NodeStorage::with_size(new_size);
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for node in self.nodes.nodes.drain(..).flatten() {
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new_node_storage.insert_new(node.key, node.value, node.hash);
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for mut node in self.nodes.nodes.drain(..) {
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if let Some((key, value, hash)) = node.take_key_value() {
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new_node_storage.insert_new(key, value, hash);
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}
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}
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self.nodes = new_node_storage;
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@ -215,11 +294,11 @@ where
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let hash = self.hash(&key);
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if let Some(location) = self.nodes.get_location(&key, hash) {
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let old_node = self.nodes.nodes[location].take().unwrap();
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let old_node = self.nodes.nodes[location].take();
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let (new_node, old_value) = old_node.with_new_key_value(key, value);
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self.nodes.nodes[location] = Some(new_node);
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self.nodes.nodes[location] = new_node;
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return Some(old_value);
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return old_value;
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}
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if self.nodes.capacity() * 85 / 100 <= self.len() {
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@ -235,14 +314,15 @@ where
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self.nodes
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.get_location(key, hash)
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.map(|location| &self.nodes.nodes[location].as_ref().unwrap().value)
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.map(|location| self.nodes.nodes[location].get_value_ref())
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.flatten()
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}
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pub fn get_mut(&mut self, key: &K) -> Option<&mut V> {
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let hash = self.hash(key);
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if let Some(location) = self.nodes.get_location(key, hash) {
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Some(&mut self.nodes.nodes[location].as_mut().unwrap().value)
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self.nodes.nodes[location].get_value_mut()
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} else {
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None
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}
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@ -282,12 +362,12 @@ impl<'a, K, V> Iterator for Iter<'a, K, V> {
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return None;
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}
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if let Some(node) = &self.map.nodes.nodes[self.at] {
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self.at += 1;
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return Some((&node.key, &node.value));
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}
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let node = &self.map.nodes.nodes[self.at];
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self.at += 1;
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if node.has_value() {
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return Some((node.key_ref().unwrap(), node.get_value_ref().unwrap()));
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}
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}
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}
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}
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@ -341,7 +421,7 @@ where
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{
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match self {
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Entry::Occupied(e) => {
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f(&mut e.entry.value);
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f(e.entry.get_value_mut().unwrap());
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Entry::Occupied(e)
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}
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Entry::Vacant(e) => Entry::Vacant(e),
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@ -359,7 +439,7 @@ where
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if let Some(location) = location {
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Entry::Occupied(OccupiedEntry {
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entry: self.nodes.nodes[location].as_mut().unwrap(),
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entry: &mut self.nodes.nodes[location],
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})
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} else {
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Entry::Vacant(VacantEntry { key, map: self })
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