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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563
use crate::std_core::{cell, fmt, hash, marker::PhantomData, ops, ptr::NonNull}; use super::{Token, Unsync}; /// A singleton unforgeable token used to access the contents of a /// `TokenLock`. /// /// It's a singleton object, meaning there can be only one instance of /// `SingletonToken<Tag>` for each specific `Tag`. The instances of /// `SingletonToken` are solely distinguished by its type parameter `Tag`, /// making this type zero-sized. /// /// This type lacks a `Clone` implementation to ensure exclusive access to /// [`TokenLock`]. /// /// This type is invariant over `Tag`. /// /// The second type parameter (`Variant`) is internal use only and exempt from /// the API stability guarantee. /// /// [`TokenLock`]: crate::TokenLock /// /// # `Sync`-ness Conversion /// /// `SingletonToken` can be converted back and forth to its non-`Sync` /// variation, [`UnsyncSingletonToken`], by the following methods: /// /// | | | To `Sync` | To `!Sync` | /// | ------- | ------ | -------------------- | --------------------- | /// | `Sync` | `&mut` | [`borrow_mut`] | [`borrow_unsync_mut`] | /// | | `&` | [`borrow`] | † | /// | | owned | | [`into_unsync`] | /// | `!Sync` | `&mut` | [`borrow_sync_mut`] | [`borrow_mut`] | /// | | `&` | [`borrow_sync`] | [`borrow`] | /// | | owned | [`into_sync`] | | /// /// [`borrow_mut`]: SingletonToken::borrow_mut /// [`borrow_unsync_mut`]: SingletonToken::borrow_unsync_mut /// [`borrow`]: SingletonToken::borrow /// [`borrow_sync_mut`]: SingletonToken::borrow_sync_mut /// [`borrow_sync`]: SingletonToken::borrow_sync /// [`into_unsync`]: SingletonToken::into_unsync /// [`into_sync`]: SingletonToken::into_sync /// /// † `borrow_unsync` doesn't exist because `&SingletonToken` (the `Sync` /// variation) might already be owned by multiple threads, so converting them /// to the `!Sync` variation would violate the `!Sync` requirement. /// /// The non-`Sync` variation can be used to access the contents of /// [`UnsyncTokenLock`]. /// /// [`UnsyncTokenLock`]: crate::UnsyncTokenLock pub struct SingletonToken<Tag: ?Sized, Variant = SyncVariant>( PhantomData<(Invariant<Tag>, Variant)>, ); /// The `!Sync` variant of [`SingletonToken`]. /// /// /// # Examples /// /// ``` /// # use tokenlock::*; /// use std::{cell::Cell, thread::spawn}; /// struct MyTag; /// impl_singleton_token_factory!(MyTag); /// /// type MyTokenLock<T> = UnsyncTokenLock<T, SingletonTokenId<MyTag>>; /// type MyToken = UnsyncSingletonToken<MyTag>; /// type MyTokenId = SingletonTokenId<MyTag>; /// /// static LOCK1: MyTokenLock<Cell<u32>> = /// MyTokenLock::new(MyTokenId::new(), Cell::new(1)); /// /// // Create a singleton token with a runtime uniqueness check /// let mut token = MyToken::new().unwrap(); /// /// spawn(move || { /// // Shared references can alias /// let (token_1, token_2) = (token.borrow(), token.borrow()); /// /// LOCK1.read(&*token_1).set(2); /// LOCK1.read(&*token_2).set(4); /// }); /// ``` pub type UnsyncSingletonToken<Tag> = SingletonToken<Tag, UnsyncVariant>; #[doc(hidden)] pub struct SyncVariant(()); #[doc(hidden)] pub struct UnsyncVariant(cell::Cell<()>); #[doc(hidden)] pub trait SingletonTokenVariant: private::Sealed {} impl SingletonTokenVariant for SyncVariant {} impl SingletonTokenVariant for UnsyncVariant {} mod private { pub trait Sealed {} impl Sealed for super::SyncVariant {} impl Sealed for super::UnsyncVariant {} } // FIXME: Work-around for the construction of `PhantomData<fn(...)>` being // unstable <https://github.com/rust-lang/rust/issues/67649> struct Invariant<Tag: ?Sized>(fn(&Tag) -> &Tag); impl<Tag: ?Sized, Variant: SingletonTokenVariant> fmt::Debug for SingletonToken<Tag, Variant> { #[inline] fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f.write_str("SingletonToken") } } impl<Tag: ?Sized, Variant: SingletonTokenVariant> PartialEq for SingletonToken<Tag, Variant> { #[inline] fn eq(&self, _: &Self) -> bool { false } } impl<Tag: ?Sized, Variant: SingletonTokenVariant> Eq for SingletonToken<Tag, Variant> {} impl<Tag: ?Sized, Variant: SingletonTokenVariant> hash::Hash for SingletonToken<Tag, Variant> { #[inline] fn hash<H: hash::Hasher>(&self, _: &mut H) {} } impl<Tag: ?Sized, Variant> SingletonToken<Tag, Variant> { /// Construct `Self` without checking the singleton invariant. /// /// # Safety /// /// Having more than one instance of `SingletonToken<Tag>` for a /// particular `Tag` violates [`Token`]'s requirements and allows a /// `TokenLock` to be mutably borrowed simultaneously, violating the pointer /// aliasing rules. #[inline(always)] pub const unsafe fn new_unchecked() -> Self { Self(PhantomData) } /// Construct an [`SingletonTokenId`] that equates to `self`. #[inline(always)] pub fn id(&self) -> SingletonTokenId<Tag> { SingletonTokenId(PhantomData) } /// Borrow `self` as [`SingletonTokenRef`] or [`UnsyncSingletonTokenRef`] /// of the same `Sync`-ness as `Self`. /// /// `SingletonTokenRef` is truly zero-sized, so it's more efficient to /// store and pass than `&SingletonToken`. #[inline] pub fn borrow(&self) -> SingletonTokenRef<'_, Tag, Variant> { SingletonTokenRef(PhantomData) } /// Borrow `self` mutably as [`SingletonTokenRefMut`] /// or [`UnsyncSingletonTokenRefMut`] of the same `Sync`-ness as `Self`. /// /// `SingletonTokenRefMut` is truly zero-sized, so it's more efficient to /// store and pass than `&mut SingletonToken`. #[inline] pub fn borrow_mut(&mut self) -> SingletonTokenRefMut<'_, Tag, Variant> { SingletonTokenRefMut(PhantomData) } } impl<Tag: ?Sized> UnsyncSingletonToken<Tag> { /// Borrow `self: UnsyncSingletonToken` as [`SingletonTokenRef`]. #[inline] pub fn borrow_sync(&self) -> SingletonTokenRef<'_, Tag> { SingletonTokenRef(PhantomData) } /// Borrow `self: UnsyncSingletonToken` mutably as [`SingletonTokenRefMut`]. #[inline] pub fn borrow_sync_mut(&mut self) -> SingletonTokenRefMut<'_, Tag> { SingletonTokenRefMut(PhantomData) } } impl<Tag: ?Sized> SingletonToken<Tag> { /// Borrow `self: SingletonToken` mutably as [`UnsyncSingletonTokenRefMut`]. /// /// There is no `borrow_unsync` because that would allow /// `UnsyncSingletonToken` to be logically borrowed by multiple threads. #[inline] pub fn borrow_unsync_mut(&mut self) -> UnsyncSingletonTokenRefMut<'_, Tag> { SingletonTokenRefMut(PhantomData) } } impl<Tag: ?Sized> SingletonToken<Tag> { /// Convert `SingletonToken` to the `!Sync` variant. #[inline] pub const fn into_unsync(self) -> UnsyncSingletonToken<Tag> { SingletonToken(PhantomData) } } impl<Tag: ?Sized> UnsyncSingletonToken<Tag> { /// Convert `UnsyncSingletonToken` to the `Sync` variant. #[inline] pub const fn into_sync(self) -> SingletonToken<Tag> { SingletonToken(PhantomData) } } unsafe impl<Tag: ?Sized, Variant: SingletonTokenVariant> Token<SingletonTokenId<Tag>> for SingletonToken<Tag, Variant> { #[inline(always)] fn eq_id(&self, _: &SingletonTokenId<Tag>) -> bool { true } } unsafe impl<Tag: ?Sized> Unsync for UnsyncSingletonToken<Tag> {} /// Zero-sized logical equivalent of `&'a `[`SingletonToken`]`<Tag>`. /// /// The second type parameter (`Variant`) is internal use only and exempt from /// the API stability guarantee. /// /// # Examples /// /// ``` /// # use tokenlock::*; /// struct MyTag; /// impl_singleton_token_factory!(MyTag); /// let token = SingletonToken::<MyTag>::new().unwrap(); /// let lock = TokenLock::new(token.id(), 1); /// /// // `SingletonTokenRef` is zero-sized (unlike `&SingletonToken`), so there is /// // no runtime overhead involved with passing `SingletonTokenRef`. /// access_lock(token.borrow(), &lock); /// /// fn access_lock( /// token: SingletonTokenRef<'_, MyTag>, /// lock: &TokenLock<u32, SingletonTokenId<MyTag>>, /// ) { /// assert_eq!(*lock.read(&*token), 1); /// } /// ``` /// /// `SingletonTokenRef` does not allow mutable borrow: /// /// ```rust,compile_fail /// # use tokenlock::*; /// # struct MyTag; /// # impl_singleton_token_factory!(MyTag); /// # let token = SingletonToken::<MyTag>::new().unwrap(); /// # let lock = TokenLock::new(token.id(), 1); /// let token_ref: SingletonTokenRef<MyTag> = token.borrow(); /// /// // compile error: `SingletonTokenRef` does not implement `DerefMut` /// *lock.write(&mut *token_ref) = 4; /// ``` /// /// `SingletonTokenRef` is `Send`-able because [`SingletonToken`] is `Sync`: /// /// ```rust /// # use tokenlock::*; /// # struct MyTag; /// # impl_singleton_token_factory!(MyTag); /// let token: &'static SingletonTokenGuard<MyTag> = /// Box::leak(Box::new(SingletonToken::<MyTag>::new().unwrap())); /// let token_ref: SingletonTokenRef<MyTag> = token.borrow(); /// std::thread::spawn(move || { /// let _token_ref = token_ref; /// }); /// ``` pub struct SingletonTokenRef<'a, Tag: ?Sized, Variant = SyncVariant>( PhantomData<&'a SingletonToken<Tag, Variant>>, ); /// Zero-sized logical equivalent of `&'a `[`UnsyncSingletonToken`]`<Tag>`. The /// `!Sync` variant of [`SingletonTokenRef`]. /// /// # Examples /// /// ``` /// # use tokenlock::*; /// struct MyTag; /// impl_singleton_token_factory!(MyTag); /// let token = UnsyncSingletonToken::<MyTag>::new().unwrap(); /// let lock = UnsyncTokenLock::new(token.id(), 1); /// /// // `UnsyncSingletonTokenRef` is zero-sized (unlike `&UnsyncSingletonToken`), so there is /// // no runtime overhead involved with passing `UnsyncSingletonTokenRef`. /// access_lock(token.borrow(), &lock); /// /// fn access_lock( /// token: UnsyncSingletonTokenRef<'_, MyTag>, /// lock: &UnsyncTokenLock<u32, SingletonTokenId<MyTag>>, /// ) { /// assert_eq!(*lock.read(&*token), 1); /// } /// ``` /// /// `UnsyncSingletonTokenRef` does not allow mutable borrow: /// /// ```rust,compile_fail /// # use tokenlock::*; /// # struct MyTag; /// # impl_singleton_token_factory!(MyTag); /// # let token = UnsyncSingletonToken::<MyTag>::new().unwrap(); /// # let lock = UnsyncTokenLock::new(token.id(), 1); /// let token_ref: UnsyncSingletonTokenRef<MyTag> = token.borrow(); /// /// // compile error: `UnsyncSingletonTokenRef` does not implement `DerefMut` /// *lock.write(&mut *token_ref) = 4; /// ``` /// /// `UnsyncSingletonTokenRef` is not `Send`-able because /// [`UnsyncSingletonToken`] is not `Sync`: /// /// ```rust,compile_fail /// # use tokenlock::*; /// # struct MyTag; /// # impl_singleton_token_factory!(MyTag); /// let token: &'static UnsyncSingletonTokenGuard<MyTag> = /// Box::leak(Box::new(UnsyncSingletonToken::<MyTag>::new().unwrap())); /// let token_ref: UnsyncSingletonTokenRef<MyTag> = token.borrow(); /// // compile error: `UnsyncSingletonTokenRef` is not `Send` /// std::thread::spawn(move || { /// let _token_ref = token_ref; /// }); /// ``` pub type UnsyncSingletonTokenRef<'a, Tag> = SingletonTokenRef<'a, Tag, UnsyncVariant>; impl<Tag: ?Sized, Variant: SingletonTokenVariant> fmt::Debug for SingletonTokenRef<'_, Tag, Variant> { #[inline] fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f.write_str("SingletonTokenRef") } } impl<Tag: ?Sized, Variant: SingletonTokenVariant> PartialEq for SingletonTokenRef<'_, Tag, Variant> { #[inline] fn eq(&self, _: &Self) -> bool { false } } impl<Tag: ?Sized, Variant: SingletonTokenVariant> Eq for SingletonTokenRef<'_, Tag, Variant> {} impl<Tag: ?Sized, Variant: SingletonTokenVariant> hash::Hash for SingletonTokenRef<'_, Tag, Variant> { #[inline] fn hash<H: hash::Hasher>(&self, _: &mut H) {} } impl<Tag: ?Sized, Variant: SingletonTokenVariant> ops::Deref for SingletonTokenRef<'_, Tag, Variant> { type Target = SingletonToken<Tag, Variant>; #[inline(always)] fn deref(&self) -> &Self::Target { &SingletonToken(PhantomData) } } /// Zero-sized logical equivalent of `&'a mut `[`SingletonToken`]`<Tag>`. /// /// The second type parameter (`Variant`) is internal use only and exempt from /// the API stability guarantee. /// /// # Examples /// /// ``` /// # use tokenlock::*; /// struct MyTag; /// impl_singleton_token_factory!(MyTag); /// let mut token = SingletonToken::<MyTag>::new().unwrap(); /// let lock = TokenLock::new(token.id(), 1); /// /// // `SingletonTokenRefMut` is zero-sized (unlike `&SingletonToken`), so there is /// // no runtime overhead involved with passing `SingletonTokenRefMut`. /// access_lock(token.borrow_mut(), &lock); /// /// fn access_lock( /// mut token: SingletonTokenRefMut<'_, MyTag>, /// lock: &TokenLock<u32, SingletonTokenId<MyTag>>, /// ) { /// assert_eq!(*lock.read(&*token), 1); /// lock.replace(&mut *token, 2); /// } /// ``` /// /// `SingletonTokenRefMut` is `Send`-able because [`SingletonToken`] is `Send`: /// /// ```rust /// # use tokenlock::*; /// # struct MyTag; /// # impl_singleton_token_factory!(MyTag); /// let token: &'static mut SingletonTokenGuard<MyTag> = /// Box::leak(Box::new(SingletonToken::<MyTag>::new().unwrap())); /// let token_ref: SingletonTokenRefMut<MyTag> = token.borrow_mut(); /// std::thread::spawn(move || { /// let _token_ref = token_ref; /// }); /// ``` pub struct SingletonTokenRefMut<'a, Tag: ?Sized, Variant = SyncVariant>( PhantomData<&'a mut SingletonToken<Tag, Variant>>, ); /// Zero-sized logical equivalent of `&'a mut `[`UnsyncSingletonToken`]`<Tag>`. The /// `!Sync` variant of [`SingletonTokenRefMut`]. /// /// # Examples /// /// `UnsyncSingletonTokenRefMut` is `Send`-able because [`UnsyncSingletonToken`] /// is `Send`: /// /// ```rust /// # use tokenlock::*; /// # struct MyTag; /// # impl_singleton_token_factory!(MyTag); /// let token: &'static mut UnsyncSingletonTokenGuard<MyTag> = /// Box::leak(Box::new(UnsyncSingletonToken::<MyTag>::new().unwrap())); /// let token_ref: UnsyncSingletonTokenRefMut<MyTag> = token.borrow_mut(); /// std::thread::spawn(move || { /// let _token_ref = token_ref; /// }); /// ``` pub type UnsyncSingletonTokenRefMut<'a, Tag> = SingletonTokenRefMut<'a, Tag, UnsyncVariant>; impl<Tag: ?Sized, Variant: SingletonTokenVariant> fmt::Debug for SingletonTokenRefMut<'_, Tag, Variant> { #[inline] fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f.write_str("SingletonTokenRefMut") } } impl<Tag: ?Sized, Variant: SingletonTokenVariant> PartialEq for SingletonTokenRefMut<'_, Tag, Variant> { #[inline] fn eq(&self, _: &Self) -> bool { false } } impl<Tag: ?Sized, Variant: SingletonTokenVariant> Eq for SingletonTokenRefMut<'_, Tag, Variant> {} impl<Tag: ?Sized, Variant: SingletonTokenVariant> hash::Hash for SingletonTokenRefMut<'_, Tag, Variant> { #[inline] fn hash<H: hash::Hasher>(&self, _: &mut H) {} } impl<Tag: ?Sized, Variant: SingletonTokenVariant> ops::Deref for SingletonTokenRefMut<'_, Tag, Variant> { type Target = SingletonToken<Tag>; #[inline(always)] fn deref(&self) -> &Self::Target { &SingletonToken(PhantomData) } } impl<Tag: ?Sized, Variant: SingletonTokenVariant> ops::DerefMut for SingletonTokenRefMut<'_, Tag, Variant> { #[inline(always)] fn deref_mut(&mut self) -> &mut Self::Target { // Logically borrow the original `SingletonToken` // Safety: `Self` is zero-sized, so the returned reference does not // point to an invalid memory region. unsafe { &mut *NonNull::dangling().as_ptr() } } } /// Token that cannot be used to access the contents of a [`TokenLock`], but can /// be used to create a new `TokenLock`. /// /// [`TokenLock`]: crate::TokenLock /// /// This type is invariant over `Tag`. /// /// # Examples /// /// `SingletonTokenId` can be cloned while [`SingletonToken`] cannot: /// /// ``` /// # use tokenlock::*; /// struct MyTag; /// impl_singleton_token_factory!(MyTag); /// let token = SingletonToken::<MyTag>::new().unwrap(); /// let token_id = token.id(); /// let lock1 = TokenLock::new(token_id.clone(), 1); /// let lock2 = TokenLock::new(token_id, 2); /// ``` /// /// Unlike other token types, you don't need to construct `SingletonToken` /// first, actually: /// /// ``` /// # use tokenlock::*; /// struct MyTag; /// impl_singleton_token_factory!(MyTag); /// let lock1 = TokenLock::new(SingletonTokenId::<MyTag>::new(), 1); /// let lock2 = TokenLock::new(SingletonTokenId::<MyTag>::new(), 2); /// ``` pub struct SingletonTokenId<Tag: ?Sized>(PhantomData<Invariant<Tag>>); impl<Tag: ?Sized> SingletonTokenId<Tag> { /// Construct `Self`. #[inline] pub const fn new() -> Self { Self(PhantomData) } } impl<Tag: ?Sized> Default for SingletonTokenId<Tag> { #[inline] fn default() -> Self { Self::new() } } impl<Tag: ?Sized> fmt::Debug for SingletonTokenId<Tag> { #[inline] fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f.write_str("SingletonTokenId") } } impl<Tag: ?Sized> Clone for SingletonTokenId<Tag> { #[inline] fn clone(&self) -> Self { Self(PhantomData) } } impl<Tag: ?Sized> Copy for SingletonTokenId<Tag> {} impl<Tag: ?Sized> PartialEq for SingletonTokenId<Tag> { #[inline] fn eq(&self, _: &Self) -> bool { false } } impl<Tag: ?Sized> Eq for SingletonTokenId<Tag> {} impl<Tag: ?Sized> hash::Hash for SingletonTokenId<Tag> { #[inline] fn hash<H: hash::Hasher>(&self, _: &mut H) {} }