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https://github.com/denoland/deno.git
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201 lines
6.9 KiB
Rust
201 lines
6.9 KiB
Rust
// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
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// Think of Resources as File Descriptors. They are integers that are allocated
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// by the privileged side of Deno which refer to various rust objects that need
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// to be persisted between various ops. For example, network sockets are
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// resources. Resources may or may not correspond to a real operating system
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// file descriptor (hence the different name).
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use crate::error::bad_resource_id;
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use crate::error::not_supported;
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use crate::ZeroCopyBuf;
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use anyhow::Error;
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use futures::Future;
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use std::any::type_name;
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use std::any::Any;
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use std::any::TypeId;
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use std::borrow::Cow;
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use std::collections::BTreeMap;
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use std::iter::Iterator;
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use std::pin::Pin;
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use std::rc::Rc;
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/// Returned by resource read/write/shutdown methods
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pub type AsyncResult<T> = Pin<Box<dyn Future<Output = Result<T, Error>>>>;
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/// All objects that can be store in the resource table should implement the
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/// `Resource` trait.
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/// TODO(@AaronO): investigate avoiding alloc on read/write/shutdown
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pub trait Resource: Any + 'static {
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/// Returns a string representation of the resource which is made available
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/// to JavaScript code through `op_resources`. The default implementation
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/// returns the Rust type name, but specific resource types may override this
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/// trait method.
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fn name(&self) -> Cow<str> {
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type_name::<Self>().into()
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}
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/// Resources may implement `read()` to be a readable stream
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fn read(self: Rc<Self>, _buf: ZeroCopyBuf) -> AsyncResult<usize> {
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Box::pin(futures::future::err(not_supported()))
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}
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/// Resources may implement `write()` to be a writable stream
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fn write(self: Rc<Self>, _buf: ZeroCopyBuf) -> AsyncResult<usize> {
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Box::pin(futures::future::err(not_supported()))
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}
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/// Resources may implement `shutdown()` for graceful async shutdowns
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fn shutdown(self: Rc<Self>) -> AsyncResult<()> {
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Box::pin(futures::future::err(not_supported()))
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}
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/// Resources may implement the `close()` trait method if they need to do
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/// resource specific clean-ups, such as cancelling pending futures, after a
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/// resource has been removed from the resource table.
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fn close(self: Rc<Self>) {}
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}
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impl dyn Resource {
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#[inline(always)]
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fn is<T: Resource>(&self) -> bool {
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self.type_id() == TypeId::of::<T>()
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}
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#[inline(always)]
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#[allow(clippy::needless_lifetimes)]
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pub fn downcast_rc<'a, T: Resource>(self: &'a Rc<Self>) -> Option<&'a Rc<T>> {
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if self.is::<T>() {
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let ptr = self as *const Rc<_> as *const Rc<T>;
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Some(unsafe { &*ptr })
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} else {
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None
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}
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}
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}
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/// A `ResourceId` is an integer value referencing a resource. It could be
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/// considered to be the Deno equivalent of a `file descriptor` in POSIX like
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/// operating systems. Elsewhere in the code base it is commonly abbreviated
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/// to `rid`.
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// TODO: use `u64` instead?
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pub type ResourceId = u32;
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/// Map-like data structure storing Deno's resources (equivalent to file
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/// descriptors).
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///
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/// Provides basic methods for element access. A resource can be of any type.
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/// Different types of resources can be stored in the same map, and provided
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/// with a name for description.
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///
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/// Each resource is identified through a _resource ID (rid)_, which acts as
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/// the key in the map.
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#[derive(Default)]
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pub struct ResourceTable {
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index: BTreeMap<ResourceId, Rc<dyn Resource>>,
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next_rid: ResourceId,
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}
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impl ResourceTable {
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/// Inserts resource into the resource table, which takes ownership of it.
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///
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/// The resource type is erased at runtime and must be statically known
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/// when retrieving it through `get()`.
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///
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/// Returns a unique resource ID, which acts as a key for this resource.
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pub fn add<T: Resource>(&mut self, resource: T) -> ResourceId {
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self.add_rc(Rc::new(resource))
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}
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/// Inserts a `Rc`-wrapped resource into the resource table.
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///
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/// The resource type is erased at runtime and must be statically known
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/// when retrieving it through `get()`.
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///
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/// Returns a unique resource ID, which acts as a key for this resource.
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pub fn add_rc<T: Resource>(&mut self, resource: Rc<T>) -> ResourceId {
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let resource = resource as Rc<dyn Resource>;
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let rid = self.next_rid;
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let removed_resource = self.index.insert(rid, resource);
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assert!(removed_resource.is_none());
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self.next_rid += 1;
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rid
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}
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/// Returns true if any resource with the given `rid` exists.
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pub fn has(&self, rid: ResourceId) -> bool {
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self.index.contains_key(&rid)
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}
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/// Returns a reference counted pointer to the resource of type `T` with the
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/// given `rid`. If `rid` is not present or has a type different than `T`,
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/// this function returns `None`.
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pub fn get<T: Resource>(&self, rid: ResourceId) -> Result<Rc<T>, Error> {
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self
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.index
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.get(&rid)
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.and_then(|rc| rc.downcast_rc::<T>())
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.map(Clone::clone)
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.ok_or_else(bad_resource_id)
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}
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pub fn get_any(&self, rid: ResourceId) -> Result<Rc<dyn Resource>, Error> {
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self
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.index
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.get(&rid)
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.map(Clone::clone)
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.ok_or_else(bad_resource_id)
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}
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/// Removes a resource of type `T` from the resource table and returns it.
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/// If a resource with the given `rid` exists but its type does not match `T`,
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/// it is not removed from the resource table. Note that the resource's
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/// `close()` method is *not* called.
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pub fn take<T: Resource>(&mut self, rid: ResourceId) -> Result<Rc<T>, Error> {
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let resource = self.get::<T>(rid)?;
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self.index.remove(&rid);
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Ok(resource)
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}
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/// Removes a resource from the resource table and returns it. Note that the
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/// resource's `close()` method is *not* called.
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pub fn take_any(
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&mut self,
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rid: ResourceId,
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) -> Result<Rc<dyn Resource>, Error> {
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self.index.remove(&rid).ok_or_else(bad_resource_id)
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}
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/// Removes the resource with the given `rid` from the resource table. If the
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/// only reference to this resource existed in the resource table, this will
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/// cause the resource to be dropped. However, since resources are reference
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/// counted, therefore pending ops are not automatically cancelled. A resource
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/// may implement the `close()` method to perform clean-ups such as canceling
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/// ops.
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pub fn close(&mut self, rid: ResourceId) -> Result<(), Error> {
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self
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.index
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.remove(&rid)
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.ok_or_else(bad_resource_id)
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.map(|resource| resource.close())
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}
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/// Returns an iterator that yields a `(id, name)` pair for every resource
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/// that's currently in the resource table. This can be used for debugging
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/// purposes or to implement the `op_resources` op. Note that the order in
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/// which items appear is not specified.
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///
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/// # Example
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///
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/// ```
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/// # use deno_core::ResourceTable;
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/// # let resource_table = ResourceTable::default();
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/// let resource_names = resource_table.names().collect::<Vec<_>>();
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/// ```
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pub fn names(&self) -> impl Iterator<Item = (ResourceId, Cow<str>)> {
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self
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.index
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.iter()
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.map(|(&id, resource)| (id, resource.name()))
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}
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}
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