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use std::fmt::{Debug, Display, Formatter};
use std::mem::transmute;
use std::sync::atomic::{AtomicU32, Ordering};
use crate::component::Component;
use crate::util::{gen_mask_64, BitMask, NumberExt};
static NEXT: AtomicU32 = AtomicU32::new(Uid::FIRST_UNIQUE_ID);
static WILDCARD_ID: u32 = 1;
const ID_BITS: BitMask<u64> = BitMask::new(gen_mask_64!(32..=63));
const RELATION_BITS: BitMask<u64> = BitMask::new(gen_mask_64!(6..=31));
const KIND_BITS: BitMask<u64> = BitMask::new(gen_mask_64!(0..=1));
#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq, PartialOrd, Ord)]
#[repr(u8)]
pub enum Kind
{
Pair = 3,
Entity = 2,
Component = 1,
}
/// A unique identifier.
#[derive(Clone, Copy, Hash, PartialEq, Eq, PartialOrd, Ord)]
pub struct Uid
{
inner: u64,
}
impl Uid
{
/// The id part of the first unique `Uid`. The ids `0..Uid::FIRST_UNIQUE_ID` are
/// reserved.
pub const FIRST_UNIQUE_ID: u32 = 5;
/// Returns a new unique entity/component ID.
pub fn new_unique(kind: Kind) -> Self
{
let id = NEXT.fetch_add(1, Ordering::Relaxed);
Self {
inner: ID_BITS.field_prep(u64::from(id)) | KIND_BITS.field_prep(kind as u64),
}
}
#[must_use]
pub fn wildcard() -> Self
{
Self {
inner: ID_BITS.field_prep(u64::from(WILDCARD_ID))
| KIND_BITS.field_prep(Kind::Component as u64),
}
}
#[must_use]
pub fn new_pair(params: PairParams) -> Self
{
assert_ne!(
params.relation.kind(),
Kind::Pair,
"Pair relation cannot be a pair"
);
assert_ne!(
params.target.kind(),
Kind::Pair,
"Pair target cannot be a pair"
);
Self {
inner: ID_BITS.field_prep(u64::from(params.target.id()))
| RELATION_BITS.field_prep(u64::from(params.relation.id()))
| KIND_BITS.field_prep(Kind::Pair as u64),
}
}
#[must_use]
pub fn id(&self) -> u32
{
let Ok(id) = u32::try_from(self.inner.field_get(ID_BITS)) else {
unreachable!("Uid id does not fit in u32");
};
id
}
#[must_use]
pub fn kind(&self) -> Kind
{
let Ok(kind) = u8::try_from(self.inner.field_get(KIND_BITS)) else {
unreachable!("Uid kind does not fit in u8");
};
// SAFETY: The kind bits cannot be invalid since they are set using the Kind enum
// in the new_unique function
unsafe { transmute::<u8, Kind>(kind) }
}
/// If this `Uid` is a pair, returns the relation as a component `Uid`.
///
/// # Panics
/// Will panic if this `Uid` is not a pair.
pub fn relation_component(&self) -> Self
{
assert_eq!(self.kind(), Kind::Pair, "Uid is not a pair");
Self {
inner: ID_BITS.field_prep(u64::from(self.relation()))
| KIND_BITS.field_prep(Kind::Component as u64),
}
}
pub fn has_same_relation_as(&self, other: Self) -> bool
{
self.relation() == other.relation()
}
/// If this `Uid` is a pair, returns the relation as a entity `Uid`.
///
/// # Panics
/// Will panic if this `Uid` is not a pair.
pub fn relation_entity(&self) -> Self
{
assert_eq!(self.kind(), Kind::Pair, "Uid is not a pair");
Self {
inner: ID_BITS.field_prep(u64::from(self.relation()))
| KIND_BITS.field_prep(Kind::Entity as u64),
}
}
/// If this `Uid` is a pair, returns the target as a component `Uid`.
///
/// # Panics
/// Will panic if this `Uid` is not a pair.
pub fn target_component(&self) -> Self
{
assert_eq!(self.kind(), Kind::Pair, "Uid is not a pair");
Self {
inner: ID_BITS.field_prep(u64::from(self.id()))
| KIND_BITS.field_prep(Kind::Component as u64),
}
}
/// If this `Uid` is a pair, returns the target as a entity `Uid`.
///
/// # Panics
/// Will panic if this `Uid` is not a pair.
pub fn target_entity(&self) -> Self
{
assert_eq!(self.kind(), Kind::Pair, "Uid is not a pair");
Self {
inner: ID_BITS.field_prep(u64::from(self.id()))
| KIND_BITS.field_prep(Kind::Entity as u64),
}
}
fn relation(&self) -> u32
{
let Ok(relation) = u32::try_from(self.inner.field_get(RELATION_BITS)) else {
unreachable!("Uid relation does not fit in u32");
};
relation
}
}
impl Debug for Uid
{
fn fmt(&self, formatter: &mut Formatter<'_>) -> std::fmt::Result
{
formatter
.debug_struct("Uid")
.field("id", &self.id())
.field("kind", &self.kind())
.finish_non_exhaustive()
}
}
impl Display for Uid
{
fn fmt(&self, formatter: &mut Formatter<'_>) -> std::fmt::Result
{
if self.kind() == Kind::Pair {
return write!(
formatter,
"({}, {})",
self.relation(),
self.target_component()
);
}
if *self == Uid::wildcard() {
return write!(formatter, "*");
}
write!(formatter, "{}", self.id())
}
}
#[derive(Debug, Clone)]
pub struct PairParams
{
pub relation: Uid,
pub target: Uid,
}
pub trait With: 'static
{
fn uid() -> Uid;
}
impl<ComponentT: Component> With for ComponentT
{
fn uid() -> Uid
{
Self::id()
}
}
#[derive(Debug)]
pub enum Wildcard {}
impl With for Wildcard
{
fn uid() -> Uid
{
Uid::wildcard()
}
}
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