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
//! Trait object serialization for rkyv. //! //! With `rkyv_dyn`, trait objects can be serialized with rkyv then the methods //! can be called without deserializing. All it takes is some macro magic. //! //! See [`SerializeDyn`] for an example of how to use rkyv_dyn. //! //! ## Features //! //! - `nightly`: Enables some nightly features, such as //! [`likely`](std::intrinsics::likely). //! - `strict`: Guarantees that types will have the same representations across //! platforms and compilations. This is already the case in practice, but this //! feature provides a guarantee. //! - `validation`: Enables validation support through `bytecheck`. //! - `vtable_cache`: Enables local vtable caching to speed up lookups after the //! first. This requires mutating the archive, which is not possible for all //! use cases. #![cfg_attr(feature = "nightly", feature(core_intrinsics))] #[cfg(feature = "validation")] pub mod validation; use core::{ alloc, any::Any, hash::{Hash, Hasher}, marker::PhantomData, sync::atomic::AtomicU64, }; use ptr_meta::{DynMetadata, Pointee}; use rkyv::{de::Deserializer, ser::Serializer, Fallible, Serialize}; pub use rkyv_dyn_derive::archive_dyn; use rkyv_typename::TypeName; use std::collections::{hash_map::DefaultHasher, HashMap}; #[cfg(feature = "validation")] pub use validation::{CheckDynError, DynContext}; #[doc(hidden)] pub use inventory; #[cfg(all(feature = "vtable_cache", feature = "nightly"))] use core::intrinsics::likely; #[cfg(all(feature = "vtable_cache", not(feature = "nightly")))] #[inline] fn likely(b: bool) -> bool { b } /// An error that can occur while serializing and deserializing trait objects. pub type DynError = Box<dyn Any>; /// An object-safe version of `Serializer`. /// /// Instead of an associated error type, `DynSerializer` returns the /// [`DynError`] type. If you have a serializer that already implements /// `Serializer`, then it will automatically implement `DynSerializer`. pub trait DynSerializer { /// Returns the current position of the serializer. fn pos_dyn(&self) -> usize; /// Attempts to write the given bytes to the serializer. fn write_dyn(&mut self, bytes: &[u8]) -> Result<(), DynError>; } impl<'a> Fallible for dyn DynSerializer + 'a { type Error = DynError; } impl<'a> Serializer for dyn DynSerializer + 'a { fn pos(&self) -> usize { self.pos_dyn() } fn write(&mut self, bytes: &[u8]) -> Result<(), Self::Error> { self.write_dyn(bytes) } } impl<S: Serializer + ?Sized> DynSerializer for &mut S { fn pos_dyn(&self) -> usize { self.pos() } fn write_dyn(&mut self, bytes: &[u8]) -> Result<(), DynError> { match self.write(bytes) { Ok(()) => Ok(()), Err(e) => Err(Box::new(e)), } } } fn hash_type<T: TypeName + ?Sized>() -> u64 { let mut hasher = DefaultHasher::new(); T::build_type_name(|piece| piece.hash(&mut hasher)); hasher.finish() } /// A trait object that can be archived. /// /// To add archive support for a trait object: /// /// 1. Add [`archive_dyn`](macro@archive_dyn) on your trait to make a /// serializable version of it. By default, it will be named "Serialize" + your /// trait name. To rename the trait, pass the argument `serialize = "..."` as a /// parameter. /// 2. Implement `Archive` and `Serialize` for the type you want to make trait /// objects of and `TypeName` for the archived versions of them. /// 3. Implement your trait for your type and add the attribute `#[archive_dyn]` /// to it. Make sure to implement your trait for your archived type as well. /// This invocation must have the same attributes as the trait invocation. /// 4. If deserialization support is desired, add `deserialize` or /// `deserialize = "..."` as parameters and implement `Deserialize` for the /// type. By default, the deserialize trait will be named "Deserialize" + your /// trait name. Passing a trait name will use that name instead. /// /// Then you're ready to serialize boxed trait objects! /// /// Even though your deserialized values are boxed as serialize trait objects, /// your archived values are boxed as regular trait objects. This is because /// your deserialized values have to implement `SerializeDyn` but your archived /// values do not. /// /// ## Examples /// /// See [`archive_dyn`](macro@archive_dyn) for customization options. /// /// ``` /// use rkyv::{ /// archived_value, /// de::deserializers::AllocDeserializer, /// ser::{ /// serializers::WriteSerializer, /// Serializer, /// }, /// Archive, /// Archived, /// Deserialize, /// Serialize, /// }; /// use rkyv_dyn::archive_dyn; /// use rkyv_typename::TypeName; /// /// #[archive_dyn(deserialize)] /// trait ExampleTrait { /// fn value(&self) -> String; /// } /// /// #[derive(Archive, Serialize, Deserialize)] /// #[archive(derive(TypeName))] /// struct StringStruct(String); /// /// #[archive_dyn(deserialize)] /// impl ExampleTrait for StringStruct { /// fn value(&self) -> String { /// self.0.clone() /// } /// } /// /// impl ExampleTrait for Archived<StringStruct> { /// fn value(&self) -> String { /// self.0.as_str().to_string() /// } /// } /// /// #[derive(Archive, Serialize, Deserialize)] /// #[archive(derive(TypeName))] /// struct IntStruct(i32); /// /// #[archive_dyn(deserialize)] /// impl ExampleTrait for IntStruct { /// fn value(&self) -> String { /// format!("{}", self.0) /// } /// } /// /// impl ExampleTrait for Archived<IntStruct> { /// fn value(&self) -> String { /// format!("{}", self.0) /// } /// } /// /// let boxed_int = Box::new(IntStruct(42)) as Box<dyn SerializeExampleTrait>; /// let boxed_string = Box::new(StringStruct("hello world".to_string())) as Box<dyn SerializeExampleTrait>; /// let mut serializer = WriteSerializer::new(Vec::new()); /// let int_pos = serializer.serialize_value(&boxed_int) /// .expect("failed to archive boxed int"); /// let string_pos = serializer.serialize_value(&boxed_string) /// .expect("failed to archive boxed string"); /// let buf = serializer.into_inner(); /// let archived_int = unsafe { archived_value::<Box<dyn SerializeExampleTrait>>(buf.as_ref(), int_pos) }; /// let archived_string = unsafe { archived_value::<Box<dyn SerializeExampleTrait>>(buf.as_ref(), string_pos) }; /// assert_eq!(archived_int.value(), "42"); /// assert_eq!(archived_string.value(), "hello world"); /// /// let deserialized_int: Box<dyn SerializeExampleTrait> = archived_int.deserialize(&mut AllocDeserializer).unwrap(); /// let deserialized_string: Box<dyn SerializeExampleTrait> = archived_string.deserialize(&mut AllocDeserializer).unwrap(); /// assert_eq!(deserialized_int.value(), "42"); /// assert_eq!(deserialized_string.value(), "hello world"); /// ``` pub trait SerializeDyn { /// Writes the value to the serializer and returns the position it was /// written to. fn serialize_dyn(&self, serializer: &mut dyn DynSerializer) -> Result<usize, DynError>; /// Returns the type ID of the archived version of this type. fn archived_type_id(&self) -> u64; } impl<T: for<'a> Serialize<dyn DynSerializer + 'a>> SerializeDyn for T where T::Archived: TypeName, { fn serialize_dyn(&self, serializer: &mut dyn DynSerializer) -> Result<usize, DynError> { Ok(serializer.serialize_value(self)?) } fn archived_type_id(&self) -> u64 { hash_type::<T::Archived>() } } /// An object-safe version of `Deserializer`. pub trait DynDeserializer { /// Allocates and returns memory with the given layout. /// /// # Safety /// /// The memory returned by this function must be deallocated by the global /// allocator. unsafe fn alloc_dyn(&mut self, layout: alloc::Layout) -> Result<*mut u8, DynError>; } impl<'a> Fallible for dyn DynDeserializer + 'a { type Error = DynError; } impl<'a> Deserializer for (dyn DynDeserializer + 'a) { unsafe fn alloc(&mut self, layout: alloc::Layout) -> Result<*mut u8, Self::Error> { self.alloc_dyn(layout) } } impl<D: Deserializer + ?Sized> DynDeserializer for &mut D { unsafe fn alloc_dyn(&mut self, layout: alloc::Layout) -> Result<*mut u8, DynError> { self.alloc(layout).map_err(|e| Box::new(e) as DynError) } } /// A trait object that can be deserialized. /// /// See [`SerializeDyn`] for more information. pub trait DeserializeDyn<T: Pointee + ?Sized> { /// Deserializes the given value as a trait object. /// /// # Safety /// /// The caller must ensure that the memory returned is properly deallocated. unsafe fn deserialize_dyn( &self, deserializer: &mut dyn DynDeserializer, ) -> Result<*mut (), DynError>; /// Returns the metadata for the deserialized version of this value. fn deserialize_dyn_metadata( &self, deserializer: &mut dyn DynDeserializer, ) -> Result<T::Metadata, DynError>; } /// The archived version of `DynMetadata`. #[cfg_attr(feature = "strict", repr(C))] pub struct ArchivedDynMetadata<T: ?Sized> { type_id: u64, #[cfg_attr(not(feature = "vtable_cache"), allow(dead_code))] cached_vtable: AtomicU64, phantom: PhantomData<T>, } impl<T: TypeName + ?Sized> ArchivedDynMetadata<T> { /// Creates a new `ArchivedDynMetadata` for the given type. pub fn new(type_id: u64) -> Self { Self { type_id, cached_vtable: AtomicU64::new(0), phantom: PhantomData, } } fn lookup_vtable(&self) -> usize { IMPL_REGISTRY .get::<T>(self.type_id) .expect("attempted to get vtable for an unregistered impl") .vtable } /// Gets the vtable address for this trait object. With the `vtable_cache` /// feature, this will store the address locally on the first lookup. #[cfg(feature = "vtable_cache")] pub fn vtable(&self) -> usize { use core::sync::atomic::Ordering; let cached_vtable = self.cached_vtable.load(Ordering::Relaxed); if likely(cached_vtable != 0) { return cached_vtable as usize; } let vtable = self.lookup_vtable(); self.cached_vtable .store(vtable as usize as u64, Ordering::Relaxed); vtable } /// Gets the vtable address for this trait object. With the `vtable_cache` /// feature, this will store the address locally on the first lookup. #[cfg(not(feature = "vtable_cache"))] pub fn vtable(&self) -> usize { self.lookup_vtable() } /// Gets the `DynMetadata` associated with this `ArchivedDynMetadata`. pub fn pointer_metadata(&self) -> DynMetadata<T> { unsafe { core::mem::transmute(self.vtable()) } } } #[cfg(debug_assertions)] #[doc(hidden)] #[derive(Copy, Clone)] pub struct ImplDebugInfo { pub file: &'static str, pub line: u32, pub column: u32, } #[cfg(debug_assertions)] #[doc(hidden)] #[macro_export] macro_rules! debug_info { () => { rkyv_dyn::ImplDebugInfo { file: core::file!(), line: core::line!(), column: core::column!(), } }; } #[cfg(not(debug_assertions))] #[doc(hidden)] #[derive(Copy, Clone)] pub struct ImplDebugInfo; #[cfg(not(debug_assertions))] #[doc(hidden)] #[macro_export] macro_rules! debug_info { () => { rkyv_dyn::ImplDebugInfo }; } #[doc(hidden)] #[derive(Clone, Copy)] pub struct ImplData { pub vtable: usize, pub debug_info: ImplDebugInfo, } #[derive(Clone, Copy, Hash, Eq, PartialEq)] struct ImplId { trait_id: u64, type_id: u64, } impl ImplId { fn new<TY: TypeName, TR: TypeName + ?Sized>() -> Self { Self::from_type_id::<TR>(hash_type::<TY>()) } fn from_type_id<TR: TypeName + ?Sized>(type_id: u64) -> Self { Self { trait_id: hash_type::<TR>(), // The last bit of the type ID is set to 1 to make sure we can // differentiate between cached and uncached vtables when the // feature is turned on type_id: type_id | 1, } } } #[doc(hidden)] pub struct ImplEntry { impl_id: ImplId, data: ImplData, } impl ImplEntry { pub fn new<TY: TypeName + RegisteredImpl<TR>, TR: TypeName + ?Sized>() -> Self { Self { impl_id: ImplId::new::<TY, TR>(), data: ImplData { vtable: <TY as RegisteredImpl<TR>>::vtable(), debug_info: <TY as RegisteredImpl<TR>>::debug_info(), }, } } } inventory::collect!(ImplEntry); struct ImplRegistry { id_to_data: HashMap<ImplId, ImplData>, } impl ImplRegistry { fn new() -> Self { Self { id_to_data: HashMap::new(), } } fn add_entry(&mut self, entry: &ImplEntry) { let old_value = self.id_to_data.insert(entry.impl_id, entry.data); #[cfg(debug_assertions)] if let Some(old_data) = old_value { eprintln!("impl id conflict, a trait implementation was likely added twice (but it's possible there was a hash collision)"); eprintln!( "existing impl registered at {}:{}:{}", old_data.debug_info.file, old_data.debug_info.line, old_data.debug_info.column ); eprintln!( "new impl registered at {}:{}:{}", entry.data.debug_info.file, entry.data.debug_info.line, entry.data.debug_info.column ); panic!(); } debug_assert!(old_value.is_none(), "impl id conflict, a trait implementation was likely added twice (but it's possible there was a hash collision)"); } fn get<T: TypeName + ?Sized>(&self, type_id: u64) -> Option<&ImplData> { self.id_to_data.get(&ImplId::from_type_id::<T>(type_id)) } } lazy_static::lazy_static! { static ref IMPL_REGISTRY: ImplRegistry = { let mut result = ImplRegistry::new(); for entry in inventory::iter::<ImplEntry> { result.add_entry(entry); } result }; } /// Guarantees that an impl has been registered for the type as the given trait /// object. #[doc(hidden)] pub unsafe trait RegisteredImpl<T: ?Sized> { fn vtable() -> usize; fn debug_info() -> ImplDebugInfo; } #[doc(hidden)] #[cfg(not(feature = "validation"))] #[macro_export] macro_rules! register_validation { ($type:ty as $trait:ty) => {}; } /// Registers a new impl with the trait object system. /// /// This is called by `#[archive_dyn]` when attached to a trait implementation. /// You might need to call this manually if you're using generic traits and /// types, since each specific instance needs to be individually registered. /// /// Call it like `register_impl!(MyType as dyn MyTrait)`. #[macro_export] macro_rules! register_impl { ($type:ty as $trait:ty) => { const _: () = { use core::mem::MaybeUninit; use rkyv_dyn::{ debug_info, inventory, register_validation, ImplData, ImplDebugInfo, ImplEntry, RegisteredImpl, }; unsafe impl RegisteredImpl<$trait> for $type { fn vtable() -> usize { unsafe { core::mem::transmute(ptr_meta::metadata( core::ptr::null::<$type>() as *const $trait )) } } fn debug_info() -> ImplDebugInfo { debug_info!() } } inventory::submit! { ImplEntry::new::<$type, $trait>() } register_validation!($type as $trait); }; }; }