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use std::alloc::{alloc, dealloc, handle_alloc_error, Layout}; use std::marker::PhantomData; use std::mem::{transmute, MaybeUninit}; use std::ptr::{self, NonNull}; use std::sync::atomic::{AtomicUsize, Ordering}; use std::{fmt, mem, ops}; static NEXT_BUILDER_ID: AtomicUsize = AtomicUsize::new(0); /// Creates a new [`Builder`]. /// /// # Examples /// /// ```rust /// let builder = stadium::builder(); /// /// /* profit */ /// ``` /// /// [`Builder`]: `struct.Builder.html` #[inline(always)] pub fn builder<'a>() -> Builder<'a> { Builder::new() } /// A chunk of allocated memory that stores a bunch of values of different types. /// /// # Examples /// /// ```rust /// let mut builder = stadium::builder(); /// /// let h_vec = builder.insert(vec![1, 2, 3, 4]); /// let h_string = builder.insert(String::from("Hello")); /// let h_str = builder.insert("World"); /// /// let mut stadium = builder.build(); /// /// stadium[h_vec][0] = 2; /// assert_eq!(&stadium[h_vec][..], &[2, 2, 3, 4]); /// /// assert_eq!(stadium[h_str], "World"); /// ``` /// /// Note that using a `String` or a `Vec` inside of a [`Stadium`] defies a bit of its /// original purpose (which is storing those different types localy in memory). /// /// [`Stadium`]: struct.Stadium.html pub struct Stadium<'a> { /// The id of the stadium. This id is unique and prevent a user to use a handle /// from another stadium. id: usize, /// A pointer to the owned data. /// /// In the case of an empty allocation, this pointer is `NonNull::dangling()`. data: NonNull<u8>, /// The layout that was used to allocate the stadium. layout: Layout, /// Maps an `index` to the location of an object. /// /// SAFETY: All the `Location`s within this vector must reference objects /// owned by the stadium. /// /// When a handle is given by a `Builder`, the `index` and the `T` of that /// handle must always match the `Location` at the given index in this vector. locations: Box<[Location]>, /// The lifetime of the types used inside of the stadium. _lifetime: PhantomData<&'a ()>, } impl<'a> Stadium<'a> { /// Creates a new [`Builder`]. /// /// # Examples /// /// ```rust /// use stadium::Stadium; /// /// let builder = Stadium::builder(); /// ``` /// /// [`Builder`] struct.Builder.html #[inline(always)] pub fn builder() -> Builder<'a> { Builder::new() } /// Checks if the given [`Handle`] can be safely used with this [`Stadium`]. /// /// # Examples /// /// ```rust /// let mut builder_1 = stadium::builder(); /// let handle_1 = builder_1.insert("I'm a string inserted in the first stadium"); /// let stadium_1 = builder_1.build(); /// /// let mut builder_2 = stadium::builder(); /// let handle_2 = builder_2.insert("I'm a string inserted in the second stadium"); /// let stadium_2 = builder_2.build(); /// /// assert_eq!(stadium_1.is_associated_with(handle_2), false); /// assert_eq!(stadium_1.is_associated_with(handle_1), true); /// assert_eq!(stadium_2.is_associated_with(handle_2), true); /// assert_eq!(stadium_2.is_associated_with(handle_1), false); /// ``` /// /// [`Handle`]: struct.Handle.html /// [`Stadium`]: struct.Stadium.html #[inline(always)] pub fn is_associated_with<T: 'a>(&self, handle: Handle<T>) -> bool { handle.id == self.id } /// Replaces the object referenced by the given [`Handle`]. /// /// # Safety /// /// The provided [`Handle`] must be associated with this [`Stadium`]. /// /// To check if a [`Handle`] can be safely used with a given [`Stadium`], use the /// [`Stadium::is_associated_with`] function. /// /// # Examples /// /// ```rust /// let mut builder = stadium::builder(); /// let handle = builder.insert(4); /// let mut stadium = builder.build(); /// /// // SAFETY: The handle was created for this stadium. /// unsafe { /// assert_eq!(stadium.replace_unchecked(handle, 5), 4); /// assert_eq!(stadium.get_unchecked(handle), &5); /// } /// ``` /// /// [`Handle`]: struct.Handle.html /// [`Stadium`]: struct.Stadium.html /// [`Stadium::is_associated_with`]: struct.Stadium.html#method.is_associated_with #[inline(always)] pub unsafe fn replace_unchecked<T: 'a>(&mut self, handle: Handle<T>, val: T) -> T { mem::replace(self.get_unchecked_mut(handle), val) } /// Replaces the object referenced by the given [`Handle`] with the given value. /// /// # Panics /// /// This function panics if `handle` is not associated with this [`Stadium`]. /// /// To check if a [`Handle`] can be safely used with a given [`Stadium`], use the /// [`Stadium::is_associated_with`] function. /// /// # Examples /// /// ```rust /// let mut builder = stadium::builder(); /// let handle = builder.insert(5); /// let mut stadium = builder.build(); /// /// assert_eq!(stadium.replace(handle, 6), 5); /// assert_eq!(stadium.get(handle), &6); /// ``` /// /// [`Handle`]: struct.Handle.html /// [`Stadium`]: struct.Stadium.html /// [`Stadium::is_associated_with`]: struct.Stadium.html#method.is_associated_with #[inline(always)] pub fn replace<T: 'a>(&mut self, handle: Handle<T>, val: T) -> T { mem::replace(self.get_mut(handle), val) } /// Gets a reference to a value that is part of the [`Stadium`]. /// /// # Panics /// /// This function panics if `handle` is not associated with this `Stadium`. /// /// To check if a [`Handle`] can be safely used with a given [`Stadium`], use the /// [`Stadium::is_associated_with`] function. /// /// # Examples /// /// ```rust /// let mut builder = stadium::builder(); /// /// let h_num = builder.insert(2023); /// let h_str = builder.insert("Hello, world"); /// /// let stadium = builder.build(); /// /// assert_eq!(stadium.get(h_str), &"Hello, world"); /// assert_eq!(stadium.get(h_num), &2023); /// ``` /// /// [`Handle`]: struct.Handle.html /// [`Stadium`]: struct.Stadium.html /// [`Stadium::is_associated_with`]: struct.Stadium.html#method.is_associated_with #[inline] pub fn get<T: 'a>(&self, handle: Handle<T>) -> &T { assert!( self.is_associated_with(handle), "The given handle was not created for this stadium" ); // SAFETY: If a handle is valid, its index is always in the bounds of `locations`. unsafe { // SAFETY: The handle was created for this stadium. // The object has a location. self.get_unchecked(handle) } } /// Gets a reference to a value that is part of the [`Stadium`]. /// /// # Panics /// /// This function panics if `handle` is not associated with this [`Stadium`]. /// /// To check if a [`Handle`] can be safely used with a given [`Stadium`], use the /// [`Stadium::is_associated_with`] function. /// /// # Examples /// /// ```rust /// let mut builder = stadium::builder(); /// /// let h_num = builder.insert(250); /// let h_vec = builder.insert(vec![1, 2, 3]); /// /// let mut stadium = builder.build(); /// /// *stadium.get_mut(h_num) = 5; /// stadium.get_mut(h_vec).push(4); /// /// assert_eq!(stadium.get(h_num), &5); /// assert_eq!(&stadium.get(h_vec)[..], &[1, 2, 3, 4]) /// ``` /// /// [`Handle`]: struct.Handle.html /// [`Stadium`]: struct.Stadium.html /// [`Stadium::is_associated_with`]: struct.Stadium.html#method.is_associated_with #[inline] pub fn get_mut<T: 'a>(&mut self, handle: Handle<T>) -> &mut T { assert!( self.is_associated_with(handle), "The given handle was not created for this stadium" ); // SAFETY: see `Stadium::get` unsafe { self.get_unchecked_mut(handle) } } /// Gets a reference to a value that is part of the [`Stadium`]. /// /// # Safety /// /// The provided [`Handle`] must be associated with this [`Stadium`]. /// /// To check if a [`Handle`] can be safely used with a given [`Stadium`], use the /// [`Stadium::is_associated_with`] function. /// /// # Examples /// /// ```rust /// let mut builder = stadium::builder(); /// let handle = builder.insert(5); /// let mut stadium = builder.build(); /// /// // SAFETY: The handle was provided by the builder of this stadium. /// unsafe { assert_eq!(stadium.get_unchecked(handle), &5) }; /// ``` /// /// [`Handle`]: struct.Handle.html /// [`Stadium`]: struct.Stadium.html /// [`Stadium::is_associated_with`]: struct.Stadium.html#method.is_associated_with #[inline(always)] pub unsafe fn get_unchecked<T: 'a>(&self, handle: Handle<T>) -> &T { // SAFETY: This function can only be called using a shared reference to `self` // This ensure that no one has a mutable reference to this `T`. // // The caller must ensure that `handle` is associated with this `Stadium`. &*self.get_ptr(handle) } /// Gets a reference to a value that is part of the [`Stadium`]. /// /// # Safety /// /// The provided [`Handle`] must be associated with this [`Stadium`]. /// /// To check if a [`Handle`] can be safely used with a given [`Stadium`], use the /// [`Stadium::is_associated_with`] function. /// /// # Examples /// /// ```rust /// let mut builder = stadium::builder(); /// let handle = builder.insert(5); /// let mut stadium = builder.build(); /// /// // SAFETY: The handle was provided by the builder of this stadium. /// unsafe { /// *stadium.get_unchecked_mut(handle) = 4; /// assert_eq!(stadium.get_unchecked(handle), &4); /// } /// ``` /// /// [`Handle`]: struct.Handle.html /// [`Stadium`]: struct.Stadium.html /// [`Stadium::is_associated_with`]: struct.Stadium.html#method.is_associated_with #[inline(always)] pub unsafe fn get_unchecked_mut<T: 'a>(&mut self, handle: Handle<T>) -> &mut T { // SAFETY: This function was called using a mutable reference to `self`. // This ensure that no one else has a mutable reference to this `T`. // // The caller must ensure that `handle` is associated with this `Stadium`. &mut *self.get_ptr_mut(handle) } /// Gets a pointer to the element referenced by the given [`RawHandle`]. /// /// # Safety /// /// This function is unsafe unless: /// * The given [`Handle`] is associated with this [`Stadium`]. /// * The returned pointer is used *as if* it was a `*const T` where /// `T` is the type of the original [`Handle`] (it was `Handle<T>`). /// /// To check if a [`Handle`] can be safely used with a given [`Stadium`], use the /// [`Stadium::is_associated_with`] function. /// /// [`Handle`]: struct.Handle.html /// [`Stadium`]: struct.Stadium.html /// [`Stadium::is_associated_with`]: struct.Stadium.html#method.is_associated_with /// [`RawHandle`]: struct.RawHandle.html #[inline(always)] pub unsafe fn get_ptr_raw(&self, handle: RawHandle) -> *const u8 { // SAFETY: The caller must ensure that the handle is actually valid. // A valid handle hold an index that is in bounds. self.locations.get_unchecked(handle.index).data } /// Gets a pointer to the element referenced by the given [`RawHandle`]. /// /// # Safety /// /// This function is unsafe unless: /// * The given [`Handle`] is associated with this [`Stadium`]. /// * The returned pointer is used *as if* it was a `*mut T` where /// `T` is the type of the original [`Handle`] (it was `Handle<T>`). /// /// To check if a [`Handle`] can be safely used with a given [`Stadium`], use the /// [`Stadium::is_associated_with`] function. /// /// [`Handle`]: struct.Handle.html /// [`Stadium`]: struct.Stadium.html /// [`Stadium::is_associated_with`]: struct.Stadium.html#method.is_associated_with /// [`RawHandle`]: struct.RawHandle.html #[inline(always)] pub unsafe fn get_ptr_mut_raw(&mut self, handle: RawHandle) -> *mut u8 { // SAFETY: The caller must ensure that the handle is actually valid. // A valid handle hold an index that is in bounds. self.locations.get_unchecked_mut(handle.index).data } /// Gets a pointer to the element referenced by the given [`Handle`]. /// /// # Safety /// /// The given [`Handle`] must be associated with this [`Stadium`]. /// /// To check if a [`Handle`] can be safely used with a given [`Stadium`], use the /// [`Stadium::is_associated_with`] function. /// /// [`Handle`]: struct.Handle.html /// [`Stadium`]: struct.Stadium.html /// [`Stadium::is_associated_with`]: struct.Stadium.html#method.is_associated_with #[inline(always)] pub unsafe fn get_ptr<T: 'a>(&self, handle: Handle<T>) -> *const T { // SAFETY: The caller must ensure that the handle was associated with this // `Stadium`. // The raw handle was created from a `Handle<T>`. self.get_ptr_raw(handle.raw()).cast() } /// Gets a pointer to the element referenced by the given [`Handle`]. /// /// # Safety /// /// The given [`Handle`] must be associated with this [`Stadium`]. /// /// To check if a [`Handle`] can be safely used with a given [`Stadium`], use the /// [`Stadium::is_associated_with`] function. /// /// [`Handle`]: struct.Handle.html /// [`Stadium`]: struct.Stadium.html /// [`Stadium::is_associated_with`]: struct.Stadium.html#method.is_associated_with #[inline(always)] pub unsafe fn get_ptr_mut<T: 'a>(&mut self, handle: Handle<T>) -> *mut T { // SAFETY: The caller must ensure that the handle was associated with this // `Stadium`. // The raw handle was created from a `Handle<T>`. self.get_ptr_mut_raw(handle.raw()).cast() } /// Swaps the values referenced by `a` and `b` within this [`Stadium`]. /// /// # Safety /// /// * This given handles `a` and `b` must both be associated with this [`Stadium`]. /// * `a` must be different from `b` /// /// # Examples /// /// ```rust /// let mut builder = stadium::builder(); /// let a = builder.insert("Foo"); /// let b = builder.insert("Bar"); /// let mut s = builder.build(); /// /// assert_eq!(s[a], "Foo"); /// assert_eq!(s[b], "Bar"); /// /// // SAFETY: Those two handles are associated with `s`. /// unsafe { s.swap_unchecked(a, b); } /// /// assert_eq!(s[a], "Bar"); /// assert_eq!(s[b], "Foo"); /// ``` /// /// [`Stadium`]: struct.Stadium.html pub unsafe fn swap_unchecked<T: 'a>(&mut self, a: Handle<T>, b: Handle<T>) { // SAFETY: This function was called using a mutable reference to `self` // which mean no one else has a reference to any of those two objects. // // The caller must ensure that the given handle is actually valid AND // distinct. let a = &mut *self.get_ptr_mut(a); let b = &mut *self.get_ptr_mut(b); mem::swap(a, b); } /// Swaps the values referenced by `a` and `b` within this [`Stadium`]. /// /// # Panics /// /// This function panics if one of `a` or `b` is not associated with tihs [`Stadium`]. /// /// To check if a [`Handle`] can be safely used with a given [`Stadium`], use the /// [`Stadium::is_associated_with`] function. /// /// # Examples /// /// ```rust /// let mut builder = stadium::builder(); /// let a = builder.insert("Foo"); /// let b = builder.insert("Bar"); /// let mut s = builder.build(); /// /// assert_eq!(s[a], "Foo"); /// assert_eq!(s[b], "Bar"); /// /// s.swap(a, b); /// /// assert_eq!(s[a], "Bar"); /// assert_eq!(s[b], "Foo"); /// ``` /// /// [`Handle`]: struct.Handle.html /// [`Stadium`]: struct.Stadium.html /// [`Stadium::is_associated_with`]: struct.Stadium.html#method.is_associated_with pub fn swap<T: 'a>(&mut self, a: Handle<T>, b: Handle<T>) { if a != b { assert!( self.is_associated_with(a), "`a` is not associated with this `Stadium`" ); assert!( self.is_associated_with(b), "`b` is not associated with this `Stadium`" ); // SAFETY: a != b and those handles are both // associated with this `Stadium`. unsafe { self.swap_unchecked(a, b) }; } } } impl Drop for Stadium<'_> { fn drop(&mut self) { for location in self.locations.iter() { if let Some(drop_fn) = location.meta.drop_fn { // SAFETY: The data in the stadium is always initialized. unsafe { drop_fn(location.data) }; } } // Now that all objects are dropped // We can deallocate the chunk of memory // check for empty stadiums if self.data != NonNull::dangling() { // SAFETY: The chunk was allocated with the same allocator and layout. unsafe { dealloc(self.data.as_ptr(), self.layout) }; } } } impl<'a, T: 'a> ops::Index<Handle<T>> for Stadium<'a> { type Output = T; #[inline(always)] fn index(&self, handle: Handle<T>) -> &Self::Output { self.get(handle) } } impl<'a, T: 'a> ops::IndexMut<Handle<T>> for Stadium<'a> { #[inline(always)] fn index_mut(&mut self, handle: Handle<T>) -> &mut Self::Output { self.get_mut(handle) } } /// Locates an object within a `Stadium`. struct Location { /// A pointer to the actual object. data: *mut u8, /// Information about the object. meta: ObjectMeta, } /// A structure used to create a [`Stadium`]. This function can be created using /// the [`stadium::builder`] function. /// /// [`Stadium`]: struct.Stadium.html /// [`stadium::builder`]: fn.builder.html pub struct Builder<'a> { id: usize, reserved_objects: Vec<Reserved<'a>>, } impl<'a> Builder<'a> { /// Creates a new instance of [`Builder`]. /// /// # Examples /// /// ```rust /// let builder = stadium::Builder::new(); /// // That it! Now you have your own builder. /// ``` /// /// [`Builder`]: struct.Builder.html #[inline(always)] pub fn new() -> Self { Self { id: NEXT_BUILDER_ID.fetch_add(1, Ordering::Relaxed), reserved_objects: Vec::new(), } } /// Prepares the insertion of `init` into the [`Stadium`]. /// /// # Panics /// /// This function panics if it fails to allocate a box for `init`. /// /// [`Stadium`]: struct.Stadium.html pub fn insert<T: 'a>(&mut self, init: T) -> Handle<T> { let index = self.reserved_objects.len(); self.reserved_objects.push(Reserved::new(init)); Handle { id: self.id, index, _marker: PhantomData, } } /// Prepares the insertion of a `MaybeUninit<T>` into the [`Stadium`] where /// `T` is the type described by the given [`ObjectMeta`] structure. /// /// [`ObjectMeta`]: struct.ObjectMeta.html /// [`Stadium`]: struct.Stadium.html pub fn insert_raw(&mut self, meta: ObjectMeta) -> RawHandle { let index = self.reserved_objects.len(); self.reserved_objects.push(Reserved::uninit(meta)); RawHandle { index } } /// Prepares the insertion of a `MaybeUninit<T>` into the [`Stadium`]. /// /// [`Stadium`]: struct.Stadium.html pub fn insert_uninit<T>(&mut self) -> Handle<MaybeUninit<T>> { let meta = ObjectMeta::of::<T>(); let handle = self.insert_raw(meta); unsafe { handle.trust_with_builder(&self) } } /// Prepares the insertion of a `T` into the [`Stadium`] where `T` is the type /// described by the given [`ObjectMeta`] structure. /// /// # Safety /// /// `T` must be safely created using `mem::zeroed()`. /// /// [`ObjectMeta`]: struct.ObjectMeta.html /// [`Stadium`]: struct.Stadium.html pub unsafe fn insert_zeroed_raw(&mut self, meta: ObjectMeta) -> RawHandle { let index = self.reserved_objects.len(); self.reserved_objects.push(Reserved::zeroed(meta)); RawHandle { index } } /// Prepares the insertion of a `T` into the [`Stadium`]. /// /// # Safety /// /// `T` must be safely created using `mem::zeroed()`. /// /// [`Stadium`]: struct.Stadium.html pub unsafe fn insert_zeroed<T>(&mut self) -> Handle<T> { let meta = ObjectMeta::of::<T>(); let handle = self.insert_zeroed_raw(meta); handle.trust_with_builder(self) } /// Prepares the insertion of a `T` into the [`Stadium`]. /// The `T` will be automatically initialized to its default value. /// /// [`Stadium`]: struct.Stadium.html pub fn insert_default<T: Default>(&mut self) -> Handle<T> { unsafe fn write_default<T: Default>(ptr: *mut T) { ptr.write(T::default()) } let index = self.reserved_objects.len(); self.reserved_objects .push(unsafe { Reserved::func(write_default::<T>) }); Handle { id: self.id, index, _marker: PhantomData, } } /// Builds a new [`Stadium`]. /// /// # Panics /// /// This function can panics if one of the following events occure: /// * The builder is empty /// * The function fails to allocate for the stadium /// /// [`Stadium`]: struct.Stadium.html pub fn build(self) -> Stadium<'a> { let objects = self.reserved_objects; let id = self.id; let mut total_size = 0; let mut max_align = 1; for obj in &objects { total_size += obj.meta.layout.size(); max_align = Ord::max(max_align, obj.meta.layout.align()); } let layout = Layout::from_size_align(total_size, max_align) .expect("Failed to compute the layout of the stadium"); let ptr = unsafe { if total_size == 0 { // The stadium will be either empty or only store zero-sized types. NonNull::dangling() // zero-sized allocation } else { NonNull::new(alloc(layout)).unwrap_or_else(|| handle_alloc_error(layout)) } }; let object_count = objects.len(); let mut sorted_vector: Vec<(usize, Reserved)> = objects.into_iter().enumerate().collect(); // Sort the vector so that objects are sorted by align (ascending). sorted_vector.sort_unstable_by_key(|(_, o)| o.meta.layout.align()); // We need this structure to map the handles that the builder has given // to actual objects within the stadium. // TODO: use `Box::new_uninit_slice` when stable. let mut locations: Vec<Location> = Vec::with_capacity(object_count); let mut cursor = ptr.as_ptr(); for (original_index, obj) in sorted_vector.into_iter().rev() { // Safety check that should always pass assert_eq!(cursor as usize % obj.meta.layout.align(), 0); // SAFETY: We just checked if cursor was well-aligned. // We know cursor cannot be null. // We own the memory and have exclusive access to it. let meta = unsafe { obj.consume(cursor) }; // The cursor stays aligned because the size of an object is always // a multiple of its alignement. Because we are iterating in reversed // order (large align -> little align), the cursor is always aligned // to the current object. // // This works because the alignement is always a power of 2. // SAFETY: it is important that the index is the same as the index that // was given to the used through the `Handle`. This index will // be trusted by the `Stadium` for the type of the object and for its // location. // // The `locations` vector was created with a capacity of `object_count` // The values of `original_index` are all differents and // `0 <= original_index < object_count`. unsafe { locations .as_mut_ptr() .add(original_index) .write(Location { meta, data: cursor }); } // SAFETY: We own the data. A safety check will be done after the loop. cursor = unsafe { cursor.add(meta.layout.size()) }; } // SAFETY: This vector was properly initialized inside the loop and has a // capacity of `object_count`. unsafe { locations.set_len(object_count) }; // Safety check that should always pass assert_eq!(cursor as usize, ptr.as_ptr() as usize + total_size); // Now the stadium is properly initialized. Stadium { id, data: ptr, layout, locations: locations.into_boxed_slice(), _lifetime: PhantomData, } } } impl<'a> From<Builder<'a>> for Stadium<'a> { #[inline(always)] fn from(builder: Builder<'a>) -> Self { builder.build() } } // In the following documentation, the type `T` is refering to the type of the reserved // object. /// Stores information about a `T`. #[derive(Clone, Copy)] pub struct ObjectMeta { /// The layout of `T`. layout: Layout, /// A function that causes a `T` to be dropped. /// /// # Safety /// /// * The given pointer must reference an initialized `T`. drop_fn: Option<unsafe fn(*mut u8)>, } impl ObjectMeta { /// Computes the [`ObjectMeta`] of the type `T`. /// /// [`ObjectMeta`]: struct.ObjectMeta.html pub fn of<T>() -> Self { Self { layout: Layout::new::<T>(), drop_fn: if mem::needs_drop::<T>() { Some(|ptr: *mut u8| unsafe { ptr::drop_in_place(ptr as *mut T) }) } else { None }, } } } /// Describes how a reserved value should be initialized when a stadium is /// created. enum InitialValue { /// The value may be left uninitialized. Uninit, /// The value should be initialized using `mem::zeroed()`. Zeroed, /// The value should be initialized by a function. /// /// # Safety /// /// The `*mut u8` given to the inner function must be a valid location for /// a `T` to be written. Fn(unsafe fn(*mut u8)), /// The value should be initialized using the allocated value. Value(NonNull<u8>), } /// Stores information about a `T` as well as an initialized instance of `T`. struct Reserved<'a> { /// Stores information about a `T`. meta: ObjectMeta, /// The actual reserved value. initial_value: InitialValue, // The lifetime of `T`. _lifetime: PhantomData<&'a ()>, } impl<'a> Reserved<'a> { /// Creates a new instance of `Reserved` from the given initial value. /// /// # Panics /// /// This function panics if it fails to allocate a box for the given `T`. fn new<T: 'a>(init: T) -> Self { let meta = ObjectMeta::of::<T>(); let initial_value = unsafe { if meta.layout.size() == 0 { // ZSTs can be left uninitialized. InitialValue::Uninit } else { // SAFETY: `T` is not a zero-sized type. let ptr = NonNull::new(alloc(meta.layout)) .unwrap_or_else(|| handle_alloc_error(meta.layout)); // Initialize the value. ptr.as_ptr().cast::<T>().write(init); InitialValue::Value(ptr) } }; // The initial value is now properly initialized. Self { meta, initial_value, _lifetime: PhantomData, } } /// Creates a new instance of `Reserved` for a `MaybeUninit<T>` /// where `T` is the type of the object described by the given `ObjectMeta`. /// /// # Panics /// /// This function panics if it fails to allocate a box for `T`. fn uninit(meta: ObjectMeta) -> Self { // Being uninit is a valid state for a `MaybeUninit<T>` Self { initial_value: InitialValue::Uninit, meta, _lifetime: PhantomData, } } /// Creates a new instance of `Reserved` for a `T` where `T` is the object /// described by the given `ObjectMeta`. /// /// # Safety /// /// `T` must be safely created using `mem::zeroed()`. /// unsafe fn zeroed(meta: ObjectMeta) -> Self { let initial_value = if meta.layout.size() == 0 { InitialValue::Uninit } else { InitialValue::Zeroed }; Self { meta, initial_value, _lifetime: PhantomData, } } /// Creates a new instance of `Reserved` for a `T` where `T` is the object /// described by the given `ObjectMeta`. /// /// # Safety /// /// The given function must properly initialize the given `T`. unsafe fn func<T>(f: unsafe fn(*mut T)) -> Self { let meta = ObjectMeta::of::<T>(); let f = transmute(f); let initial_value = if meta.layout.size() == 0 { InitialValue::Uninit } else { InitialValue::Fn(f) }; Self { meta, initial_value, _lifetime: PhantomData, } } /// Consumes `self` and turns it into its inner `T`. The value is written on the /// given pointer `target`. /// /// # Safety /// /// `target` must be a valid location for an object of type `T` to be written on. unsafe fn consume(self, target: *mut u8) -> ObjectMeta { // SAFETY: We're moving out the value. let initial_value = ptr::read(&self.initial_value); let meta = self.meta; // `self` mut not be dropped because this would cause the value at `initial_value` // to be dropped even though it was moved. mem::forget(self); match initial_value { InitialValue::Value(ptr) => { // SAFETY: We are moving the value referenced by `initial_value` to // `target`. ptr::copy_nonoverlapping(ptr.as_ptr(), target, meta.layout.size()); // We have to dealloc the layout though. dealloc(ptr.as_ptr(), meta.layout); } InitialValue::Fn(f) => f(target), InitialValue::Zeroed => ptr::write_bytes(target, 0u8, meta.layout.size()), InitialValue::Uninit => (), } meta } } impl Drop for Reserved<'_> { fn drop(&mut self) { if let InitialValue::Value(ptr) = self.initial_value { // We have to drop the initial value that was not used. if let Some(drop_fn) = self.meta.drop_fn { // SAFETY: The value is known to be initialized. unsafe { drop_fn(ptr.as_ptr()) }; } // SAFETY: The layout was used to allocate the `T` in `Self::new` and the value // that was here was properly dropped beforehand. unsafe { dealloc(ptr.as_ptr(), self.meta.layout) }; } } } /// A safe handle to a specific object stored in a specific [`Stadium`]. This handle can /// be optained from the [`Builder::insert`] function. /// /// [`Stadium`]: struct.Stadium.html /// [`Builder::insert`]: struct.Builder.html#method.insert pub struct Handle<T> { /// The id of the stadium this handle exist for. id: usize, /// The index of the location of the object referenced by this handle. index: usize, // Invariant T owned by this handle. _marker: PhantomData<*mut T>, } impl<T> Clone for Handle<T> { #[inline(always)] fn clone(&self) -> Self { Self { id: self.id, index: self.index, _marker: PhantomData, } } } impl<T> Copy for Handle<T> {} impl<T> fmt::Debug for Handle<T> { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { f.debug_tuple("Handle").field(&self.index).finish() } } impl<T> PartialEq for Handle<T> { fn eq(&self, other: &Self) -> bool { self.id == other.id && self.index == other.index } } impl<T> Eq for Handle<T> {} impl<T> Handle<T> { /// Converts this [`Handle`] into a [`RawHandle`]. /// /// # Examples /// /// ```rust /// let mut builder = stadium::builder(); /// let raw_handle = builder.insert("Hello").raw(); /// ``` /// /// [`Handle`]: struct.Handle.html /// [`RawHandle`]: struct.RawHandle.html #[inline(always)] pub fn raw(self) -> RawHandle { RawHandle { index: self.index } } } /// A handle to a `T` that does not own a `T`. This handle dos not remember /// what stadium created it. #[derive(Clone, Copy)] pub struct RawHandle { /// The index of the location of the object referenced by this handle. index: usize, } impl RawHandle { /// Recreate an [`Handle`] from this [`RawHandle`]. /// /// # Safety /// /// * The generic type parameter `T` must be the same as the original [`Handle`] /// that was used to produce this [`RawHandle`]. /// * The given [`Stadium`] must be the one associated with the original handle. /// /// # Examples /// /// ```rust /// let mut builder = stadium::builder(); /// let handle = builder.insert(5i32); /// let stadium = builder.build(); /// /// let raw_handle = handle.raw(); /// /// // SAFETY: The handle was given by the builder that created the stadium and was /// // created for a `i32`. /// let handle = unsafe { raw_handle.trust::<i32>(&stadium) }; /// /// assert_eq!(stadium[handle], 5); /// ``` /// /// [`Handle`]: struct.Handle.html /// [`RawHandle`]: struct.RawHandle.html /// [`Stadium`]: struct.Stadium.html #[inline(always)] pub unsafe fn trust<T>(self, stadium: &Stadium) -> Handle<T> { Handle { index: self.index, id: stadium.id, _marker: PhantomData, } } /// Recreate an [`Handle`] from this [`RawHandle`]. /// /// # Safety /// /// * The generic type parameter `T` must be the same as the original [`Handle`] /// that was used to produce this `RawHandle`. /// * The given [`Builder`] must be the one associated with the original handle. /// /// # Examples /// /// ```rust /// let mut builder = stadium::builder(); /// let raw_handle = builder.insert(5i32).raw(); /// /// // SAFETY: The handle was given by this builder and was created for a `i32`. /// let handle = unsafe { raw_handle.trust_with_builder::<i32>(&builder) }; /// /// let stadium = builder.build(); /// assert_eq!(stadium[handle], 5); /// ``` /// /// [`Handle`]: struct.Handle.html /// [`RawHandle`]: struct.RawHandle.html /// [`Builder`]: struct.Builder.html #[inline(always)] pub unsafe fn trust_with_builder<T>(self, builder: &Builder) -> Handle<T> { Handle { index: self.index, id: builder.id, _marker: PhantomData, } } }