b4e785d0f5
The EntityRef trait is used by more than just the EntityMap now, so it should live in its own module. Also move the entity_impl! macro into the new module so it can be used for defining new entity references anywhere.
52 lines
1.7 KiB
Rust
52 lines
1.7 KiB
Rust
//! Densely numbered entity references as mapping keys.
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//!
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//! This module defines an `EntityRef` trait that should be implemented by reference types wrapping
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//! a small integer index.
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/// A type wrapping a small integer index should implement `EntityRef` so it can be used as the key
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/// of an `EntityMap` or `SparseMap`.
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pub trait EntityRef: Copy + Eq {
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/// Create a new entity reference from a small integer.
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/// This should crash if the requested index is not representable.
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fn new(usize) -> Self;
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/// Get the index that was used to create this entity reference.
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fn index(self) -> usize;
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}
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/// Macro which provides the common implementation of a 32-bit entity reference.
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#[macro_export]
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macro_rules! entity_impl {
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// Basic traits.
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($entity:ident) => {
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impl $crate::entity_ref::EntityRef for $entity {
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fn new(index: usize) -> Self {
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assert!(index < (::std::u32::MAX as usize));
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$entity(index as u32)
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}
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fn index(self) -> usize {
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self.0 as usize
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}
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}
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impl $crate::packed_option::ReservedValue for $entity {
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fn reserved_value() -> $entity {
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$entity(::std::u32::MAX)
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}
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}
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};
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// Include basic `Display` impl using the given display prefix.
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// Display an `Ebb` reference as "ebb12".
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($entity:ident, $display_prefix:expr) => {
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entity_impl!($entity);
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impl ::std::fmt::Display for $entity {
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fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
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write!(f, "{}{}", $display_prefix, self.0)
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}
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}
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}
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}
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