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// Copyright 2018-2019 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 to refer to various rust objects that need to be
// referenced between multiple 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 downcast_rs::Downcast;
use std;
use std::any::Any;
use std::collections::HashMap;
use std::io::Error;
use std::io::ErrorKind;
/// ResourceId is Deno's version of a file descriptor. ResourceId is also referred
/// to as rid in the code base.
pub type ResourceId = u32;
/// These store Deno's file descriptors. These are not necessarily the operating
/// system ones.
type ResourceMap = HashMap<ResourceId, Box<dyn Resource>>;
#[derive(Default)]
pub struct ResourceTable {
map: ResourceMap,
next_id: u32,
}
impl ResourceTable {
pub fn get<T: Resource>(&self, rid: ResourceId) -> Result<&T, Error> {
let resource = self.map.get(&rid).ok_or_else(bad_resource)?;
let resource = &resource.downcast_ref::<T>().ok_or_else(bad_resource)?;
Ok(resource)
}
pub fn get_mut<T: Resource>(
&mut self,
rid: ResourceId,
) -> Result<&mut T, Error> {
let resource = self.map.get_mut(&rid).ok_or_else(bad_resource)?;
let resource = resource.downcast_mut::<T>().ok_or_else(bad_resource)?;
Ok(resource)
}
// TODO: resource id allocation should probably be randomized for security.
fn next_rid(&mut self) -> ResourceId {
let next_rid = self.next_id;
self.next_id += 1;
next_rid as ResourceId
}
pub fn add(&mut self, resource: Box<dyn Resource>) -> ResourceId {
let rid = self.next_rid();
let r = self.map.insert(rid, resource);
assert!(r.is_none());
rid
}
// close(2) is done by dropping the value. Therefore we just need to remove
// the resource from the RESOURCE_TABLE.
pub fn close(&mut self, rid: ResourceId) -> Result<(), Error> {
let repr = self.map.remove(&rid).ok_or_else(bad_resource)?;
// Give resource a chance to cleanup (notify tasks, etc.)
repr.close();
Ok(())
}
}
/// Abstract type representing resource in Deno.
pub trait Resource: Downcast + Any + Send {
/// Method that allows to cleanup resource.
fn close(&self) {}
fn inspect_repr(&self) -> &str {
unimplemented!();
}
}
impl_downcast!(Resource);
// TODO: probably bad error kind
pub fn bad_resource() -> Error {
Error::new(ErrorKind::NotFound, "bad resource id")
}
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