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81 lines
2.5 KiB
Rust
81 lines
2.5 KiB
Rust
// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
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// Think of Resources as File Descriptors. They are integers that are allocated by
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// the privileged side of Deno to refer to various rust objects that need to be
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// referenced between multiple ops. For example, network sockets are resources.
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// Resources may or may not correspond to a real operating system file
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// descriptor (hence the different name).
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use downcast_rs::Downcast;
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use std;
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use std::any::Any;
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use std::collections::HashMap;
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/// ResourceId is Deno's version of a file descriptor. ResourceId is also referred
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/// to as rid in the code base.
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pub type ResourceId = u32;
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/// These store Deno's file descriptors. These are not necessarily the operating
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/// system ones.
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type ResourceMap = HashMap<ResourceId, (String, Box<dyn Resource>)>;
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#[derive(Default)]
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pub struct ResourceTable {
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map: ResourceMap,
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next_id: u32,
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}
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impl ResourceTable {
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pub fn get<T: Resource>(&self, rid: ResourceId) -> Option<&T> {
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if let Some((_name, resource)) = self.map.get(&rid) {
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return resource.downcast_ref::<T>();
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}
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None
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}
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pub fn get_mut<T: Resource>(&mut self, rid: ResourceId) -> Option<&mut T> {
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if let Some((_name, resource)) = self.map.get_mut(&rid) {
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return resource.downcast_mut::<T>();
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}
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None
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}
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// TODO: resource id allocation should probably be randomized for security.
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fn next_rid(&mut self) -> ResourceId {
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let next_rid = self.next_id;
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self.next_id += 1;
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next_rid as ResourceId
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}
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pub fn add(&mut self, name: &str, resource: Box<dyn Resource>) -> ResourceId {
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let rid = self.next_rid();
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let r = self.map.insert(rid, (name.to_string(), resource));
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assert!(r.is_none());
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rid
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}
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pub fn entries(&self) -> Vec<(ResourceId, String)> {
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self
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.map
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.iter()
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.map(|(key, (name, _resource))| (*key, name.clone()))
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.collect()
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}
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// close(2) is done by dropping the value. Therefore we just need to remove
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// the resource from the resource table.
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pub fn close(&mut self, rid: ResourceId) -> Option<()> {
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self.map.remove(&rid).map(|(_name, _resource)| ())
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}
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}
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/// Abstract type representing resource in Deno.
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///
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/// The only thing it does is implementing `Downcast` trait
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/// that allows to cast resource to concrete type in `TableResource::get`
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/// and `TableResource::get_mut` methods.
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pub trait Resource: Downcast + Any + Send {}
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impl<T> Resource for T where T: Downcast + Any + Send {}
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impl_downcast!(Resource);
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