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denoland-deno/core/resources.rs
Bartek Iwańczuk 6984b63f2f
refactor: rewrite ops to use ResourceTable2 (#8512)
This commit migrates all ops to use new resource table
and "AsyncRefCell".

Old implementation of resource table was completely 
removed and all code referencing it was updated to use
new system.
2020-12-16 17:14:12 +01:00

164 lines
5.8 KiB
Rust

// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
// Think of Resources as File Descriptors. They are integers that are allocated
// by the privileged side of Deno which refer to various rust objects that need
// to be persisted between various ops. For example, network sockets are
// resources. Resources may or may not correspond to a real operating system
// file descriptor (hence the different name).
use std::any::type_name;
use std::any::Any;
use std::any::TypeId;
use std::borrow::Cow;
use std::collections::HashMap;
use std::iter::Iterator;
use std::rc::Rc;
/// All objects that can be store in the resource table should implement the
/// `Resource` trait.
pub trait Resource: Any + 'static {
/// Returns a string representation of the resource which is made available
/// to JavaScript code through `op_resources`. The default implementation
/// returns the Rust type name, but specific resource types may override this
/// trait method.
fn name(&self) -> Cow<str> {
type_name::<Self>().into()
}
/// Resources may implement the `close()` trait method if they need to do
/// resource specific clean-ups, such as cancelling pending futures, after a
/// resource has been removed from the resource table.
fn close(self: Rc<Self>) {}
}
impl dyn Resource {
#[inline(always)]
fn is<T: Resource>(&self) -> bool {
self.type_id() == TypeId::of::<T>()
}
#[inline(always)]
#[allow(clippy::needless_lifetimes)]
pub fn downcast_rc<'a, T: Resource>(self: &'a Rc<Self>) -> Option<&'a Rc<T>> {
if self.is::<T>() {
let ptr = self as *const Rc<_> as *const Rc<T>;
Some(unsafe { &*ptr })
} else {
None
}
}
}
/// A `ResourceId` is an integer value referencing a resource. It could be
/// considered to be the Deno equivalent of a `file descriptor` in POSIX like
/// operating systems. Elsewhere in the code base it is commonly abbreviated
/// to `rid`.
// TODO: use `u64` instead?
pub type ResourceId = u32;
/// Map-like data structure storing Deno's resources (equivalent to file
/// descriptors).
///
/// Provides basic methods for element access. A resource can be of any type.
/// Different types of resources can be stored in the same map, and provided
/// with a name for description.
///
/// Each resource is identified through a _resource ID (rid)_, which acts as
/// the key in the map.
#[derive(Default)]
pub struct ResourceTable {
index: HashMap<ResourceId, Rc<dyn Resource>>,
next_rid: ResourceId,
}
impl ResourceTable {
/// Inserts resource into the resource table, which takes ownership of it.
///
/// The resource type is erased at runtime and must be statically known
/// when retrieving it through `get()`.
///
/// Returns a unique resource ID, which acts as a key for this resource.
pub fn add<T: Resource>(&mut self, resource: T) -> ResourceId {
self.add_rc(Rc::new(resource))
}
/// Inserts a `Rc`-wrapped resource into the resource table.
///
/// The resource type is erased at runtime and must be statically known
/// when retrieving it through `get()`.
///
/// Returns a unique resource ID, which acts as a key for this resource.
pub fn add_rc<T: Resource>(&mut self, resource: Rc<T>) -> ResourceId {
let resource = resource as Rc<dyn Resource>;
let rid = self.next_rid;
let removed_resource = self.index.insert(rid, resource);
assert!(removed_resource.is_none());
self.next_rid += 1;
rid
}
/// Returns true if any resource with the given `rid` exists.
pub fn has(&self, rid: ResourceId) -> bool {
self.index.contains_key(&rid)
}
/// Returns a reference counted pointer to the resource of type `T` with the
/// given `rid`. If `rid` is not present or has a type different than `T`,
/// this function returns `None`.
pub fn get<T: Resource>(&self, rid: ResourceId) -> Option<Rc<T>> {
self
.index
.get(&rid)
.and_then(|rc| rc.downcast_rc::<T>())
.map(Clone::clone)
}
pub fn get_any(&self, rid: ResourceId) -> Option<Rc<dyn Resource>> {
self.index.get(&rid).map(Clone::clone)
}
/// Removes a resource of type `T` from the resource table and returns it.
/// If a resource with the given `rid` exists but its type does not match `T`,
/// it is not removed from the resource table. Note that the resource's
/// `close()` method is *not* called.
pub fn take<T: Resource>(&mut self, rid: ResourceId) -> Option<Rc<T>> {
let resource = self.get::<T>(rid)?;
self.index.remove(&rid);
Some(resource)
}
/// Removes a resource from the resource table and returns it. Note that the
/// resource's `close()` method is *not* called.
pub fn take_any(&mut self, rid: ResourceId) -> Option<Rc<dyn Resource>> {
self.index.remove(&rid)
}
/// Removes the resource with the given `rid` from the resource table. If the
/// only reference to this resource existed in the resource table, this will
/// cause the resource to be dropped. However, since resources are reference
/// counted, therefore pending ops are not automatically cancelled. A resource
/// may implement the `close()` method to perform clean-ups such as canceling
/// ops.
pub fn close(&mut self, rid: ResourceId) -> Option<()> {
self.index.remove(&rid).map(|resource| resource.close())
}
/// Returns an iterator that yields a `(id, name)` pair for every resource
/// that's currently in the resource table. This can be used for debugging
/// purposes or to implement the `op_resources` op. Note that the order in
/// which items appear is not specified.
///
/// # Example
///
/// ```
/// # use deno_core::ResourceTable;
/// # let resource_table = ResourceTable::default();
/// let resource_names = resource_table.names().collect::<Vec<_>>();
/// ```
pub fn names(&self) -> impl Iterator<Item = (ResourceId, Cow<str>)> {
self
.index
.iter()
.map(|(&id, resource)| (id, resource.name()))
}
}