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//! Allows placing resources (i.e. "global" data) in a dictionary and looking it up by type. The data
//! could be "global" systems, component storages, component factories, etc.
//!
//! This implements a type system for expressing read/write dependencies. Many readers and single
//! writers are allowed, but not both at the same time. This is checked at runtime, not compile time.
//!
//! Lots of inspiration taken from `shred` for how to create a type system
//! to express read/write dependencies
//
// ResourceId
//
use std::any::TypeId;
use std::marker::PhantomData;
use std::prelude::v1::*;
use downcast_rs::Downcast;
use fnv::FnvHashMap as HashMap;
use crate::trust_cell::{Ref, RefMut, TrustCell};
/// Every type can be converted to a `ResourceId`. The ResourceId is used to look up the type's value
/// in the `ResourceMap`
#[derive(Clone, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
pub struct ResourceId {
type_id: TypeId,
}
impl ResourceId {
/// Creates a new resource id from a given type.
#[inline]
pub fn new<T: 'static>() -> Self {
ResourceId {
type_id: std::any::TypeId::of::<T>(),
}
}
}
/// Any data that can be stored in the ResourceMap must implement this trait. There is a blanket
/// implementation provided for all compatible types
pub trait Resource: Downcast + Send + Sync + 'static {}
impl<T> Resource for T where T: Downcast + Send + Sync {}
// Used for downcastic
mod __resource_mopafy_scope {
#![allow(clippy::all)]
use super::Resource;
downcast_rs::impl_downcast!(Resource);
}
/// Builder for creating a ResourceMap
pub struct ResourceMapBuilder {
/// The ResourceMap being built
resource_map: ResourceMap,
}
impl ResourceMapBuilder {
/// Creates an empty builder
pub fn new() -> Self {
ResourceMapBuilder {
resource_map: ResourceMap::new(),
}
}
/// Builder-style API that adds the resource to the map
pub fn with_resource<R>(
mut self,
r: R,
) -> Self
where
R: Resource,
{
self.resource_map.insert(r);
self
}
/// Adds the resource to the map
pub fn insert<R>(
&mut self,
r: R,
) where
R: Resource,
{
self.resource_map.insert(r);
}
/// Consume this builder, returning the resource map
pub fn build(self) -> ResourceMap {
self.resource_map
}
}
/// A key-value structure. The key is a type, and the value is a single object of that type
#[derive(Default)]
pub struct ResourceMap {
resources: HashMap<ResourceId, TrustCell<Box<dyn Resource>>>,
}
impl ResourceMap {
/// Creates an empty resource map
pub fn new() -> Self {
ResourceMap {
resources: HashMap::default(),
}
}
pub fn try_insert_default<R>(&mut self)
where
R: Resource + Default,
{
if !self.has_value::<R>() {
self.insert(R::default());
}
}
/// Add a type/resource instance to the map
pub fn insert<R>(
&mut self,
r: R,
) where
R: Resource,
{
self.insert_by_id(ResourceId::new::<R>(), r);
}
/// Remove a type/resource instance from the map
pub fn remove<R>(&mut self) -> Option<R>
where
R: Resource,
{
self.remove_by_id(ResourceId::new::<R>())
}
fn insert_by_id<R>(
&mut self,
id: ResourceId,
r: R,
) where
R: Resource,
{
//TODO: Do not allow silent overwrite
let _old = self.resources.insert(id, TrustCell::new(Box::new(r)));
//assert!(old.is_none());
}
fn remove_by_id<R>(
&mut self,
id: ResourceId,
) -> Option<R>
where
R: Resource,
{
self.resources
.remove(&id)
.map(TrustCell::into_inner)
.map(|x: Box<dyn Resource>| x.downcast())
.map(|x: Result<Box<R>, _>| x.ok().unwrap())
.map(|x| *x)
}
fn unwrap_resource<R>(resource: Option<R>) -> R {
if resource.is_none() {
let name = core::any::type_name::<R>();
// Tried to fetch or fetch_mut on a resource that is not registered.
panic!("Resource not found: {}", name);
}
resource.unwrap()
}
/// Read-only fetch of a resource. Trying to get a resource that is not in the map is fatal. Use
/// try_fetch if unsure whether the resource exists. Requesting read access to a resource that
/// has any concurrently active writer is fatal.
pub fn fetch<R: Resource>(&self) -> ReadBorrow<R> {
let result = self.try_fetch();
Self::unwrap_resource(result)
}
/// Read-only fetch of a resource. Requesting read access to a resource that has a concurrently
/// active writer is fatal. Returns None if the type is not registered.
pub fn try_fetch<R: Resource>(&self) -> Option<ReadBorrow<R>> {
let res_id = ResourceId::new::<R>();
self.resources.get(&res_id).map(|r| ReadBorrow {
inner: Ref::map(r.borrow(), Box::as_ref),
phantom: PhantomData,
})
}
/// Read/Write fetch of a resource. Trying to get a resource that is not in the map is fatal. Use
/// try_fetch if unsure whether the resource exists. Requesting write access to a resource with
/// any concurrently active read/write is fatal
pub fn fetch_mut<R: Resource>(&self) -> WriteBorrow<R> {
let result = self.try_fetch_mut();
Self::unwrap_resource(result)
}
/// Read/Write fetch of a resource. Requesting write access to a resource with
/// any concurrently active read/write is fatal. Returns None if the type is not registered.
pub fn try_fetch_mut<R: Resource>(&self) -> Option<WriteBorrow<R>> {
let res_id = ResourceId::new::<R>();
self.resources.get(&res_id).map(|r| WriteBorrow::<R> {
inner: RefMut::map(r.borrow_mut(), Box::as_mut),
phantom: PhantomData,
})
}
/// Returns true if the resource is registered.
pub fn has_value<R>(&self) -> bool
where
R: Resource,
{
self.has_value_raw(ResourceId::new::<R>())
}
fn has_value_raw(
&self,
id: ResourceId,
) -> bool {
self.resources.contains_key(&id)
}
/// Iterate all ResourceIds within the dictionary
pub fn keys(&self) -> impl Iterator<Item = &ResourceId> {
self.resources.iter().map(|x| x.0)
}
}
/// DataRequirement base trait, which underlies Read<T> and Write<T> requests
pub trait DataRequirement<'a> {
type Borrow: DataBorrow;
fn fetch(resource_map: &'a ResourceMap) -> Self::Borrow;
}
// Implementation for () required because we build support for (), (A), (A, B), (A, B, ...) inductively
impl<'a> DataRequirement<'a> for () {
type Borrow = ();
fn fetch(_: &'a ResourceMap) -> Self::Borrow {}
}
/// This type represents requesting read access to T. If T is not registered, trying to fill this
/// request will be fatal
pub struct Read<T: Resource> {
phantom_data: PhantomData<T>,
}
/// Same as `Read`, but will return None rather than being fatal
pub type ReadOption<T> = Option<Read<T>>;
impl<'a, T: Resource> DataRequirement<'a> for Read<T> {
type Borrow = ReadBorrow<'a, T>;
fn fetch(resource_map: &'a ResourceMap) -> Self::Borrow {
resource_map.fetch::<T>()
}
}
impl<'a, T: Resource> DataRequirement<'a> for Option<Read<T>> {
type Borrow = Option<ReadBorrow<'a, T>>;
fn fetch(resource_map: &'a ResourceMap) -> Self::Borrow {
resource_map.try_fetch::<T>()
}
}
/// This type represents requesting write access to T. If T is not registered, trying to fill this
/// request will be fatal
pub struct Write<T: Resource> {
phantom_data: PhantomData<T>,
}
/// Same as `Write`, but will return None rather than being fatal
pub type WriteOption<T> = Option<Write<T>>;
impl<'a, T: Resource> DataRequirement<'a> for Write<T> {
type Borrow = WriteBorrow<'a, T>;
fn fetch(resource_map: &'a ResourceMap) -> Self::Borrow {
resource_map.fetch_mut::<T>()
}
}
impl<'a, T: Resource> DataRequirement<'a> for Option<Write<T>> {
type Borrow = Option<WriteBorrow<'a, T>>;
fn fetch(resource_map: &'a ResourceMap) -> Self::Borrow {
resource_map.try_fetch_mut::<T>()
}
}
/// Borrow base trait. This base trait is required to allow inductively composing tuples of ReadBorrow/WriteBorrow
/// i.e. (), (A), (A, B), (A, B, ...) inductively
pub trait DataBorrow {}
// Implementation for () required because we build support for (), (A), (A, B), (A, B, ...) inductively
impl DataBorrow for () {}
/// Represents a filled read-only request for T
pub struct ReadBorrow<'a, T> {
inner: Ref<'a, dyn Resource>,
phantom: PhantomData<&'a T>,
}
impl<'a, T> DataBorrow for ReadBorrow<'a, T> {}
impl<'a, T> DataBorrow for Option<ReadBorrow<'a, T>> {}
impl<'a, T> std::ops::Deref for ReadBorrow<'a, T>
where
T: Resource,
{
type Target = T;
fn deref(&self) -> &T {
self.inner.downcast_ref().unwrap()
}
}
impl<'a, T> Clone for ReadBorrow<'a, T> {
fn clone(&self) -> Self {
ReadBorrow {
inner: self.inner.clone(),
phantom: PhantomData,
}
}
}
/// Represents a filled read/write request for T
pub struct WriteBorrow<'a, T> {
inner: RefMut<'a, dyn Resource>,
phantom: PhantomData<&'a mut T>,
}
impl<'a, T> DataBorrow for WriteBorrow<'a, T> {}
impl<'a, T> DataBorrow for Option<WriteBorrow<'a, T>> {}
impl<'a, T> std::ops::Deref for WriteBorrow<'a, T>
where
T: Resource,
{
type Target = T;
fn deref(&self) -> &T {
self.inner.downcast_ref().unwrap()
}
}
impl<'a, T> std::ops::DerefMut for WriteBorrow<'a, T>
where
T: Resource,
{
fn deref_mut(&mut self) -> &mut T {
self.inner.downcast_mut().unwrap()
}
}
// This macro is used to inductively build tuples i.e. (), (A), (A, B), (A, B, ...) inductively
macro_rules! impl_data {
( $($ty:ident),* ) => {
//
// Make tuples containing DataBorrow types implement DataBorrow
//
impl<$($ty),*> DataBorrow for ( $( $ty , )* )
where $( $ty : DataBorrow ),*
{
}
//
// Make tuples containing DataRequirement types implement DataBorrow. Additionally implement
// fetch
//
impl<'a, $($ty),*> DataRequirement<'a> for ( $( $ty , )* )
where $( $ty : DataRequirement<'a> ),*
{
type Borrow = ( $( <$ty as DataRequirement<'a>>::Borrow, )* );
fn fetch(resource_map: &'a ResourceMap) -> Self::Borrow {
#![allow(unused_variables)]
( $( <$ty as DataRequirement<'a>>::fetch(resource_map), )* )
}
}
};
}
mod impl_data {
#![cfg_attr(rustfmt, rustfmt_skip)]
use super::*;
// Build tuples for DataBorrow/DataRequirement i.e. (), (A), (A, B), (A, B, ...) inductively
impl_data!(A);
impl_data!(A, B);
impl_data!(A, B, C);
impl_data!(A, B, C, D);
impl_data!(A, B, C, D, E);
impl_data!(A, B, C, D, E, F);
impl_data!(A, B, C, D, E, F, G);
impl_data!(A, B, C, D, E, F, G, H);
impl_data!(A, B, C, D, E, F, G, H, I);
impl_data!(A, B, C, D, E, F, G, H, I, J);
// May be extended as needed, but this seems like enough
// impl_data!(A, B, C, D, E, F, G, H, I, J, K);
// impl_data!(A, B, C, D, E, F, G, H, I, J, K, L);
// impl_data!(A, B, C, D, E, F, G, H, I, J, K, L, M);
// impl_data!(A, B, C, D, E, F, G, H, I, J, K, L, M, N);
// impl_data!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O);
// impl_data!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P);
// impl_data!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q);
// impl_data!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R);
// impl_data!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S);
// impl_data!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T);
// impl_data!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U);
// impl_data!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V);
// impl_data!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W);
// impl_data!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X);
// impl_data!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y);
// impl_data!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z);
}