tauri/
state.rs

1// Copyright 2019-2024 Tauri Programme within The Commons Conservancy
2// SPDX-License-Identifier: Apache-2.0
3// SPDX-License-Identifier: MIT
4
5use std::{
6  any::{Any, TypeId},
7  collections::HashMap,
8  hash::BuildHasherDefault,
9  pin::Pin,
10  sync::Mutex,
11};
12
13use crate::{
14  ipc::{CommandArg, CommandItem, InvokeError},
15  Runtime,
16};
17
18/// A guard for a state value.
19///
20/// See [`Manager::manage`](`crate::Manager::manage`) for usage examples.
21pub struct State<'r, T: Send + Sync + 'static>(&'r T);
22
23impl<'r, T: Send + Sync + 'static> State<'r, T> {
24  /// Retrieve a borrow to the underlying value with a lifetime of `'r`.
25  /// Using this method is typically unnecessary as `State` implements
26  /// [`std::ops::Deref`] with a [`std::ops::Deref::Target`] of `T`.
27  #[inline(always)]
28  pub fn inner(&self) -> &'r T {
29    self.0
30  }
31}
32
33impl<T: Send + Sync + 'static> std::ops::Deref for State<'_, T> {
34  type Target = T;
35
36  #[inline(always)]
37  fn deref(&self) -> &T {
38    self.0
39  }
40}
41
42impl<T: Send + Sync + 'static> Clone for State<'_, T> {
43  fn clone(&self) -> Self {
44    State(self.0)
45  }
46}
47
48impl<T: Send + Sync + 'static + PartialEq> PartialEq for State<'_, T> {
49  fn eq(&self, other: &Self) -> bool {
50    self.0 == other.0
51  }
52}
53
54impl<T: Send + Sync + std::fmt::Debug> std::fmt::Debug for State<'_, T> {
55  fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
56    f.debug_tuple("State").field(&self.0).finish()
57  }
58}
59
60impl<'r, 'de: 'r, T: Send + Sync + 'static, R: Runtime> CommandArg<'de, R> for State<'r, T> {
61  /// Grabs the [`State`] from the [`CommandItem`]. This will never fail.
62  fn from_command(command: CommandItem<'de, R>) -> Result<Self, InvokeError> {
63    command.message.state_ref().try_get().ok_or_else(|| {
64      InvokeError::from_anyhow(anyhow::anyhow!(
65        "state not managed for field `{}` on command `{}`. You must call `.manage()` before using this command",
66        command.key, command.name
67      ))
68    })
69  }
70}
71
72// Taken from: https://github.com/SergioBenitez/state/blob/556c1b94db8ce8427a0e72de7983ab5a9af4cc41/src/ident_hash.rs
73// This is a _super_ stupid hash. It just uses its input as the hash value. This
74// hash is meant to be used _only_ for "prehashed" values. In particular, we use
75// this so that hashing a TypeId is essentially a noop. This is because TypeIds
76// are already unique integers.
77#[derive(Default)]
78struct IdentHash(u64);
79
80impl std::hash::Hasher for IdentHash {
81  fn finish(&self) -> u64 {
82    self.0
83  }
84
85  fn write(&mut self, bytes: &[u8]) {
86    for byte in bytes {
87      self.write_u8(*byte);
88    }
89  }
90
91  fn write_u8(&mut self, i: u8) {
92    self.0 = (self.0 << 8) | (i as u64);
93  }
94
95  fn write_u64(&mut self, i: u64) {
96    self.0 = i;
97  }
98}
99
100/// Safety:
101/// - The `key` must equal to `(*value).type_id()`, see the safety doc in methods of [StateManager] for details.
102/// - Once you insert a value, you can't remove/mutated/move it anymore, see [StateManager::try_get] for details.
103type TypeIdMap = HashMap<TypeId, Pin<Box<dyn Any + Sync + Send>>, BuildHasherDefault<IdentHash>>;
104
105/// The Tauri state manager.
106#[derive(Debug)]
107pub struct StateManager {
108  map: Mutex<TypeIdMap>,
109}
110
111impl StateManager {
112  pub(crate) fn new() -> Self {
113    Self {
114      map: Default::default(),
115    }
116  }
117
118  pub(crate) fn set<T: Send + Sync + 'static>(&self, state: T) -> bool {
119    let mut map = self.map.lock().unwrap();
120    let type_id = TypeId::of::<T>();
121    let already_set = map.contains_key(&type_id);
122    if !already_set {
123      let ptr = Box::new(state) as Box<dyn Any + Sync + Send>;
124      let pinned_ptr = Box::into_pin(ptr);
125      map.insert(
126        type_id,
127        // SAFETY: keep the type of the key is the same as the type of the value，
128        // see [try_get] methods for details.
129        pinned_ptr,
130      );
131    }
132    !already_set
133  }
134
135  /// SAFETY: Calling this method will move the `value`,
136  /// which will cause references obtained through [Self::try_get] to dangle.
137  pub(crate) unsafe fn unmanage<T: Send + Sync + 'static>(&self) -> Option<T> {
138    let mut map = self.map.lock().unwrap();
139    let type_id = TypeId::of::<T>();
140    let pinned_ptr = map.remove(&type_id)?;
141    // SAFETY: The caller decides to break the immovability/safety here, then OK, just let it go.
142    let ptr = unsafe { Pin::into_inner_unchecked(pinned_ptr) };
143    let value = unsafe {
144      ptr
145        .downcast::<T>()
146        // SAFETY: the type of the key is the same as the type of the value
147        .unwrap_unchecked()
148    };
149    Some(*value)
150  }
151
152  /// Gets the state associated with the specified type.
153  pub fn get<T: Send + Sync + 'static>(&self) -> State<'_, T> {
154    self
155      .try_get()
156      .unwrap_or_else(|| panic!("state not found for type {}", std::any::type_name::<T>()))
157  }
158
159  /// Gets the state associated with the specified type.
160  pub fn try_get<T: Send + Sync + 'static>(&self) -> Option<State<'_, T>> {
161    let map = self.map.lock().unwrap();
162    let type_id = TypeId::of::<T>();
163    let ptr = map.get(&type_id)?;
164    let value = unsafe {
165      ptr
166        .downcast_ref::<T>()
167        // SAFETY: the type of the key is the same as the type of the value
168        .unwrap_unchecked()
169    };
170    // SAFETY: We ensure the lifetime of `value` is the same as [StateManager] and `value` will not be mutated/moved.
171    let v_ref = unsafe { &*(value as *const T) };
172    Some(State(v_ref))
173  }
174}
175
176// Ported from https://github.com/SergioBenitez/state/blob/556c1b94db8ce8427a0e72de7983ab5a9af4cc41/tests/main.rs
177#[cfg(test)]
178mod tests {
179  use super::StateManager;
180
181  use std::sync::{Arc, RwLock};
182  use std::thread;
183
184  // Tiny structures to test that dropping works as expected.
185  struct DroppingStruct(Arc<RwLock<bool>>);
186  struct DroppingStructWrap(#[allow(dead_code)] DroppingStruct);
187
188  impl Drop for DroppingStruct {
189    fn drop(&mut self) {
190      *self.0.write().unwrap() = true;
191    }
192  }
193
194  #[test]
195  #[should_panic(expected = "state not found for type core::option::Option<alloc::string::String>")]
196  fn get_panics() {
197    let state = StateManager::new();
198    state.get::<Option<String>>();
199  }
200
201  #[test]
202  fn simple_set_get() {
203    let state = StateManager::new();
204    assert!(state.set(1u32));
205    assert_eq!(*state.get::<u32>(), 1);
206  }
207
208  #[test]
209  fn simple_set_get_unmanage() {
210    let state = StateManager::new();
211    assert!(state.set(1u32));
212    assert_eq!(*state.get::<u32>(), 1);
213    // safety: the reference returned by `try_get` is already dropped.
214    assert!(unsafe { state.unmanage::<u32>() }.is_some());
215    assert!(unsafe { state.unmanage::<u32>() }.is_none());
216    assert_eq!(state.try_get::<u32>(), None);
217    assert!(state.set(2u32));
218    assert_eq!(*state.get::<u32>(), 2);
219  }
220
221  #[test]
222  fn dst_set_get() {
223    let state = StateManager::new();
224    assert!(state.set::<[u32; 4]>([1, 2, 3, 4u32]));
225    assert_eq!(*state.get::<[u32; 4]>(), [1, 2, 3, 4]);
226  }
227
228  #[test]
229  fn set_get_remote() {
230    let state = Arc::new(StateManager::new());
231    let sate_ = Arc::clone(&state);
232    thread::spawn(move || {
233      sate_.set(10isize);
234    })
235    .join()
236    .unwrap();
237
238    assert_eq!(*state.get::<isize>(), 10);
239  }
240
241  #[test]
242  fn two_put_get() {
243    let state = StateManager::new();
244    assert!(state.set("Hello, world!".to_string()));
245
246    let s_old = state.get::<String>();
247    assert_eq!(*s_old, "Hello, world!");
248
249    assert!(!state.set::<String>("Bye bye!".into()));
250    assert_eq!(*state.get::<String>(), "Hello, world!");
251    assert_eq!(state.get::<String>(), s_old);
252  }
253
254  #[test]
255  fn many_puts_only_one_succeeds() {
256    let state = Arc::new(StateManager::new());
257    let mut threads = vec![];
258    for _ in 0..1000 {
259      let state_ = Arc::clone(&state);
260      threads.push(thread::spawn(move || state_.set(10i64)))
261    }
262
263    let results: Vec<bool> = threads.into_iter().map(|t| t.join().unwrap()).collect();
264    assert_eq!(results.into_iter().filter(|&b| b).count(), 1);
265    assert_eq!(*state.get::<i64>(), 10);
266  }
267
268  // Ensure setting when already set doesn't cause a drop.
269  #[test]
270  fn test_no_drop_on_set() {
271    let state = StateManager::new();
272    let drop_flag = Arc::new(RwLock::new(false));
273    let dropping_struct = DroppingStruct(drop_flag.clone());
274
275    let _drop_flag_ignore = Arc::new(RwLock::new(false));
276    let _dropping_struct_ignore = DroppingStruct(_drop_flag_ignore);
277
278    state.set::<DroppingStruct>(dropping_struct);
279    assert!(!state.set::<DroppingStruct>(_dropping_struct_ignore));
280    assert!(!*drop_flag.read().unwrap());
281  }
282
283  // Ensure dropping a type_map drops its contents.
284  #[test]
285  fn drop_inners_on_drop() {
286    let drop_flag_a = Arc::new(RwLock::new(false));
287    let dropping_struct_a = DroppingStruct(drop_flag_a.clone());
288
289    let drop_flag_b = Arc::new(RwLock::new(false));
290    let dropping_struct_b = DroppingStructWrap(DroppingStruct(drop_flag_b.clone()));
291
292    {
293      let state = StateManager::new();
294      state.set(dropping_struct_a);
295      assert!(!*drop_flag_a.read().unwrap());
296
297      state.set(dropping_struct_b);
298      assert!(!*drop_flag_a.read().unwrap());
299      assert!(!*drop_flag_b.read().unwrap());
300    }
301
302    assert!(*drop_flag_a.read().unwrap());
303    assert!(*drop_flag_b.read().unwrap());
304  }
305}
tauri/state.rs

tauri/
state.rs
