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

// 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 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::any::Any;
use std::collections::HashMap;

/// 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, (String, Box<dyn Resource>)>;

#[derive(Default)]
pub struct ResourceTable {
  map: ResourceMap,
  next_id: u32,
}

impl ResourceTable {
  pub fn has(&self, rid: ResourceId) -> bool {
    self.map.contains_key(&rid)
  }

  pub fn get<T: Resource>(&self, rid: ResourceId) -> Option<&T> {
    if let Some((_name, resource)) = self.map.get(&rid) {
      return resource.downcast_ref::<T>();
    }

    None
  }

  pub fn get_mut<T: Resource>(&mut self, rid: ResourceId) -> Option<&mut T> {
    if let Some((_name, resource)) = self.map.get_mut(&rid) {
      return resource.downcast_mut::<T>();
    }

    None
  }

  // 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, name: &str, resource: Box<dyn Resource>) -> ResourceId {
    let rid = self.next_rid();
    let r = self.map.insert(rid, (name.to_string(), resource));
    assert!(r.is_none());
    rid
  }

  pub fn entries(&self) -> Vec<(ResourceId, String)> {
    self
      .map
      .iter()
      .map(|(key, (name, _resource))| (*key, name.clone()))
      .collect()
  }

  // 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) -> Option<()> {
    self.map.remove(&rid).map(|(_name, _resource)| ())
  }

  pub fn remove<T: Resource>(&mut self, rid: ResourceId) -> Option<Box<T>> {
    if let Some((_name, resource)) = self.map.remove(&rid) {
      let res = match resource.downcast::<T>() {
        Ok(res) => Some(res),
        Err(_e) => None,
      };
      return res;
    }
    None
  }
}

/// Abstract type representing resource in Deno.
///
/// The only thing it does is implementing `Downcast` trait
/// that allows to cast resource to concrete type in `TableResource::get`
/// and `TableResource::get_mut` methods.
pub trait Resource: Downcast + Any {}
impl<T> Resource for T where T: Downcast + Any {}
impl_downcast!(Resource);

#[cfg(test)]
mod tests {
  use super::*;

  struct FakeResource {
    not_empty: u128,
  }

  impl FakeResource {
    fn new(value: u128) -> FakeResource {
      FakeResource { not_empty: value }
    }
  }

  #[test]
  fn test_create_resource_table_default() {
    let table = ResourceTable::default();
    assert_eq!(table.map.len(), 0);
  }

  #[test]
  fn test_add_to_resource_table_not_empty() {
    let mut table = ResourceTable::default();
    table.add("fake1", Box::new(FakeResource::new(1)));
    table.add("fake2", Box::new(FakeResource::new(2)));
    assert_eq!(table.map.len(), 2);
  }

  #[test]
  fn test_add_to_resource_table_are_contiguous() {
    let mut table = ResourceTable::default();
    let rid1 = table.add("fake1", Box::new(FakeResource::new(1)));
    let rid2 = table.add("fake2", Box::new(FakeResource::new(2)));
    assert_eq!(rid1 + 1, rid2);
  }

  #[test]
  fn test_get_from_resource_table_is_what_was_given() {
    let mut table = ResourceTable::default();
    let rid = table.add("fake", Box::new(FakeResource::new(7)));
    let resource = table.get::<FakeResource>(rid);
    assert_eq!(resource.unwrap().not_empty, 7);
  }

  #[test]
  fn test_remove_from_resource_table() {
    let mut table = ResourceTable::default();
    let rid1 = table.add("fake1", Box::new(FakeResource::new(1)));
    let rid2 = table.add("fake2", Box::new(FakeResource::new(2)));
    assert_eq!(table.map.len(), 2);
    table.close(rid1);
    assert_eq!(table.map.len(), 1);
    table.close(rid2);
    assert_eq!(table.map.len(), 0);
  }

  #[test]
  fn test_take_from_resource_table() {
    let mut table = ResourceTable::default();
    let rid1 = table.add("fake1", Box::new(FakeResource::new(1)));
    let rid2 = table.add("fake2", Box::new(FakeResource::new(2)));
    assert_eq!(table.map.len(), 2);
    let res1 = table.remove::<FakeResource>(rid1);
    assert_eq!(table.map.len(), 1);
    assert!(res1.is_some());
    let res2 = table.remove::<FakeResource>(rid2);
    assert_eq!(table.map.len(), 0);
    assert!(res2.is_some());
  }
}