1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
// Copyright 2018-2022 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 crate::error::bad_resource_id;
use crate::error::not_supported;
use crate::io::BufMutView;
use crate::io::BufView;
use crate::io::WriteOutcome;
use anyhow::Error;
use futures::Future;
use std::any::type_name;
use std::any::Any;
use std::any::TypeId;
use std::borrow::Cow;
use std::collections::BTreeMap;
use std::iter::Iterator;
use std::pin::Pin;
use std::rc::Rc;

/// Returned by resource read/write/shutdown methods
pub type AsyncResult<T> = Pin<Box<dyn Future<Output = Result<T, Error>>>>;

/// Resources are Rust objects that are attached to a [deno_core::JsRuntime].
/// They are identified in JS by a numeric ID (the resource ID, or rid).
/// Resources can be created in ops. Resources can also be retrieved in ops by
/// their rid. Resources are not thread-safe - they can only be accessed from
/// the thread that the JsRuntime lives on.
///
/// Resources are reference counted in Rust. This means that they can be
/// cloned and passed around. When the last reference is dropped, the resource
/// is automatically closed. As long as the resource exists in the resource
/// table, the reference count is at least 1.
///
/// ### Readable
///
/// Readable resources are resources that can have data read from. Examples of
/// this are files, sockets, or HTTP streams.
///
/// Readables can be read from from either JS or Rust. In JS one can use
/// `Deno.core.read()` to read from a single chunk of data from a readable. In
/// Rust one can directly call `read()` or `read_byob()`. The Rust side code is
/// used to implement ops like `op_slice`.
///
/// A distinction can be made between readables that produce chunks of data
/// themselves (they allocate the chunks), and readables that fill up
/// bring-your-own-buffers (BYOBs). The former is often the case for framed
/// protocols like HTTP, while the latter is often the case for kernel backed
/// resources like files and sockets.
///
/// All readables must implement `read()`. If resources can support an optimized
/// path for BYOBs, they should also implement `read_byob()`. For kernel backed
/// resources it often makes sense to implement `read_byob()` first, and then
/// implement `read()` as an operation that allocates a new chunk with
/// `len == limit`, then calls `read_byob()`, and then returns a chunk sliced to
/// the number of bytes read. Kernel backed resources can use the
/// [deno_core::impl_readable_byob] macro to implement optimized `read_byob()`
/// and `read()` implementations from a single `Self::read()` method.
///
/// ### Writable
///
/// Writable resources are resources that can have data written to. Examples of
/// this are files, sockets, or HTTP streams.
///
/// Writables can be written to from either JS or Rust. In JS one can use
/// `Deno.core.write()` to write to a single chunk of data to a writable. In
/// Rust one can directly call `write()`. The latter is used to implement ops
/// like `op_slice`.
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()
  }

  /// Read a single chunk of data from the resource. This operation returns a
  /// `BufView` that represents the data that was read. If a zero length buffer
  /// is returned, it indicates that the resource has reached EOF.
  ///
  /// If this method is not implemented, the default implementation will error
  /// with a "not supported" error.
  ///
  /// If a readable can provide an optimized path for BYOBs, it should also
  /// implement `read_byob()`.
  fn read(self: Rc<Self>, limit: usize) -> AsyncResult<BufView> {
    _ = limit;
    Box::pin(futures::future::err(not_supported()))
  }

  /// Read a single chunk of data from the resource into the provided `BufMutView`.
  ///
  /// This operation returns the number of bytes read. If zero bytes are read,
  /// it indicates that the resource has reached EOF.
  ///
  /// If this method is not implemented explicitly, the default implementation
  /// will call `read()` and then copy the data into the provided buffer. For
  /// readable resources that can provide an optimized path for BYOBs, it is
  /// strongly recommended to override this method.
  fn read_byob(
    self: Rc<Self>,
    mut buf: BufMutView,
  ) -> AsyncResult<(usize, BufMutView)> {
    Box::pin(async move {
      let read = self.read(buf.len()).await?;
      let nread = read.len();
      buf[..nread].copy_from_slice(&read);
      Ok((nread, buf))
    })
  }

  /// Write a single chunk of data to the resource. The operation may not be
  /// able to write the entire chunk, in which case it should return the number
  /// of bytes written. Additionally it should return the `BufView` that was
  /// passed in.
  ///
  /// If this method is not implemented, the default implementation will error
  /// with a "not supported" error.
  fn write(self: Rc<Self>, buf: BufView) -> AsyncResult<WriteOutcome> {
    _ = buf;
    Box::pin(futures::future::err(not_supported()))
  }

  /// Write an entire chunk of data to the resource. Unlike `write()`, this will
  /// ensure the entire chunk is written. If the operation is not able to write
  /// the entire chunk, an error is to be returned.
  ///
  /// By default this method will call `write()` repeatedly until the entire
  /// chunk is written. Resources that can write the entire chunk in a single
  /// operation using an optimized path should override this method.
  fn write_all(self: Rc<Self>, view: BufView) -> AsyncResult<()> {
    Box::pin(async move {
      let mut view = view;
      let this = self;
      while !view.is_empty() {
        let resp = this.clone().write(view).await?;
        match resp {
          WriteOutcome::Partial {
            nwritten,
            view: new_view,
          } => {
            view = new_view;
            view.advance_cursor(nwritten);
          }
          WriteOutcome::Full { .. } => break,
        }
      }
      Ok(())
    })
  }

  /// The shutdown method can be used to asynchronously close the resource. It
  /// is not automatically called when the resource is dropped or closed.
  ///
  /// If this method is not implemented, the default implementation will error
  /// with a "not supported" error.
  fn shutdown(self: Rc<Self>) -> AsyncResult<()> {
    Box::pin(futures::future::err(not_supported()))
  }

  /// 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>) {}

  /// Resources backed by a file descriptor can let ops know to allow for
  /// low-level optimizations.
  #[cfg(unix)]
  fn backing_fd(self: Rc<Self>) -> Option<std::os::unix::prelude::RawFd> {
    None
  }

  fn size_hint(&self) -> (u64, Option<u64>) {
    (0, None)
  }
}

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>;
      // TODO(piscisaureus): safety comment
      #[allow(clippy::undocumented_unsafe_blocks)]
      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: BTreeMap<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>;
    self.add_rc_dyn(resource)
  }

  pub fn add_rc_dyn(&mut self, resource: Rc<dyn Resource>) -> ResourceId {
    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) -> Result<Rc<T>, Error> {
    self
      .index
      .get(&rid)
      .and_then(|rc| rc.downcast_rc::<T>())
      .map(Clone::clone)
      .ok_or_else(bad_resource_id)
  }

  pub fn get_any(&self, rid: ResourceId) -> Result<Rc<dyn Resource>, Error> {
    self
      .index
      .get(&rid)
      .map(Clone::clone)
      .ok_or_else(bad_resource_id)
  }

  /// Replaces a resource with a new resource.
  ///
  /// Panics if the resource does not exist.
  pub fn replace<T: Resource>(&mut self, rid: ResourceId, resource: T) {
    let result = self
      .index
      .insert(rid, Rc::new(resource) as Rc<dyn Resource>);
    assert!(result.is_some());
  }

  /// 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) -> Result<Rc<T>, Error> {
    let resource = self.get::<T>(rid)?;
    self.index.remove(&rid);
    Ok(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,
  ) -> Result<Rc<dyn Resource>, Error> {
    self.index.remove(&rid).ok_or_else(bad_resource_id)
  }

  /// 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) -> Result<(), Error> {
    self
      .index
      .remove(&rid)
      .ok_or_else(bad_resource_id)
      .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()))
  }
}

#[macro_export]
macro_rules! impl_readable_byob {
  () => {
    fn read(self: Rc<Self>, limit: usize) -> AsyncResult<$crate::BufView> {
      Box::pin(async move {
        let mut vec = vec![0; limit];
        let nread = self.read(&mut vec).await?;
        if nread != vec.len() {
          vec.truncate(nread);
        }
        let view = $crate::BufView::from(vec);
        Ok(view)
      })
    }

    fn read_byob(
      self: Rc<Self>,
      mut buf: $crate::BufMutView,
    ) -> AsyncResult<(usize, $crate::BufMutView)> {
      Box::pin(async move {
        let nread = self.read(buf.as_mut()).await?;
        Ok((nread, buf))
      })
    }
  };
}

#[macro_export]
macro_rules! impl_writable {
  (__write) => {
    fn write(
      self: Rc<Self>,
      view: $crate::BufView,
    ) -> AsyncResult<$crate::WriteOutcome> {
      Box::pin(async move {
        let nwritten = self.write(&view).await?;
        Ok($crate::WriteOutcome::Partial { nwritten, view })
      })
    }
  };
  (__write_all) => {
    fn write_all(self: Rc<Self>, view: $crate::BufView) -> AsyncResult<()> {
      Box::pin(async move {
        self.write_all(&view).await?;
        Ok(())
      })
    }
  };
  () => {
    $crate::impl_writable!(__write);
  };
  (with_all) => {
    $crate::impl_writable!(__write);
    $crate::impl_writable!(__write_all);
  };
}