2020-07-10 08:37:06 +00:00
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// modified by Bevy contributors
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2020-07-10 04:18:35 +00:00
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use core::fmt;
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use hashbrown::HashMap;
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#[cfg(feature = "std")]
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use std::error::Error;
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/// Lightweight unique ID of an entity
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///
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/// Obtained from `World::spawn`. Can be stored to refer to an entity in the future.
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#[derive(Debug, Clone, Copy, Hash, Eq, Ord, PartialEq, PartialOrd)]
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pub struct Entity(u32);
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impl Entity {
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#[allow(missing_docs)]
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pub fn new() -> Self {
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Self(rand::random::<u32>())
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}
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#[allow(missing_docs)]
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#[inline]
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pub fn with_id(id: u32) -> Self {
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Self(id)
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}
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/// Extract a transiently unique identifier
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///
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/// No two simultaneously-live entities share the same ID, but dead entities' IDs may collide
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/// with both live and dead entities. Useful for compactly representing entities within a
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/// specific snapshot of the world, such as when serializing.
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#[inline]
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pub fn id(self) -> u32 {
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self.0
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}
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}
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#[derive(Default)]
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pub(crate) struct Entities {
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pub entity_locations: HashMap<Entity, Location>,
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pub current: u32,
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}
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impl Entities {
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/// Destroy an entity, allowing it to be reused
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///
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/// Must not be called on reserved entities prior to `flush`.
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pub fn free(&mut self, entity: Entity) -> Result<Location, NoSuchEntity> {
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if let Some(location) = self.entity_locations.remove(&entity) {
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Ok(location)
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} else {
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Err(NoSuchEntity)
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}
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}
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/// Ensure `n` at least allocations can succeed without reallocating
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pub fn reserve(&mut self, additional: u32) {
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self.entity_locations.reserve(additional as usize)
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}
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pub fn contains(&self, entity: Entity) -> bool {
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self.entity_locations.contains_key(&entity)
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}
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pub fn clear(&mut self) {
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self.entity_locations.clear();
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}
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/// Access the location storage of an entity
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pub fn get_mut(&mut self, entity: Entity) -> Result<&mut Location, NoSuchEntity> {
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2020-07-10 08:37:06 +00:00
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self.entity_locations
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.get_mut(&entity)
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.ok_or_else(|| NoSuchEntity)
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2020-07-10 04:18:35 +00:00
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}
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/// Access the location storage of an entity
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pub fn insert(&mut self, entity: Entity, location: Location) {
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self.entity_locations.insert(entity, location);
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}
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pub fn get(&self, entity: Entity) -> Result<Location, NoSuchEntity> {
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2020-07-10 08:37:06 +00:00
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self.entity_locations
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.get(&entity)
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.cloned()
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.ok_or_else(|| NoSuchEntity)
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2020-07-10 04:18:35 +00:00
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}
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}
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#[derive(Copy, Clone)]
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#[allow(missing_docs)]
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pub struct Location {
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pub archetype: u32,
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pub index: u32,
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}
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/// Error indicating that no entity with a particular ID exists
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#[derive(Debug, Clone, Eq, PartialEq)]
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pub struct NoSuchEntity;
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impl fmt::Display for NoSuchEntity {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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f.pad("no such entity")
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}
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}
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#[cfg(feature = "std")]
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impl Error for NoSuchEntity {}
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