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// Copyright 2018 Theodore Cipicchio // // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your // option. This file may not be copied, modified, or distributed // except according to those terms. //! `Allocation` type implementation. use core::fmt; use core::ptr; use core::slice; use super::{ ConcatenateSlice, Error, ErrorKind, IntoMutSliceLikePtr, SliceLike, }; use core::marker::PhantomData; use core::mem::forget; use core::ops::{Deref, DerefMut}; use core::ptr::NonNull; /// Scratchpad [`Marker`] allocation. /// /// Markers implement the [`Deref`] and [`DerefMut`] traits, allowing the data /// to be dereferenced explicitly using the unary `*` operator (e.g. /// `*allocation`) or implicitly by the compiler under various circumstances. /// /// An allocation is statically bound to the lifetime of the [`Marker`] from /// which it is allocated, ensuring that no dangling references can be left /// when the [`Marker`] is dropped. /// /// [`Marker`]: trait.Marker.html /// [`Deref`]: https://doc.rust-lang.org/std/ops/trait.Deref.html /// [`DerefMut`]: https://doc.rust-lang.org/std/ops/trait.DerefMut.html pub struct Allocation<'marker, T> where T: ?Sized, { /// Allocation data. pub(crate) data: NonNull<T>, /// Dummy reference for ensuring the allocation does not outlive the /// `Marker` from which it was allocated. pub(crate) _phantom: PhantomData<&'marker ()>, } impl<'marker, T> Allocation<'marker, T> where T: Sized, { /// Moves the value out of the `Allocation`. /// /// Note that this is only implemented for [`Sized`] value types. /// /// # Examples /// /// ``` /// use scratchpad::Scratchpad; /// /// let x = { /// let scratchpad = Scratchpad::<[u64; 1], [usize; 1]>::new( /// [0], /// [0], /// ); /// let marker = scratchpad.mark_front().unwrap(); /// let allocation = marker.allocate(3.14159).unwrap(); /// /// allocation.unwrap() /// }; /// /// // Value was moved out of the allocation, so it can now outlive the /// // scratchpad in which it was initially created. /// assert_eq!(x, 3.14159); /// ``` /// /// [`Sized`]: https://doc.rust-lang.org/std/marker/trait.Sized.html pub fn unwrap(self) -> T { unsafe { let value = ptr::read(self.data.as_ptr()); forget(self); value } } } impl<'marker, T> Allocation<'marker, T> where T: ?Sized, { /// Converts this allocation into an allocation of a compatible /// [`SliceLike`] type without altering the allocation data. /// /// # Examples /// /// ``` /// use scratchpad::{Allocation, Scratchpad}; /// /// let scratchpad = Scratchpad::<[i32; 6], [usize; 1]>::static_new(); /// let marker = scratchpad.mark_front().unwrap(); /// /// let scalar = marker.allocate(3).unwrap(); /// assert_eq!(*scalar.into_slice_like_allocation(), [3]); /// /// let slice = marker.allocate_array_with(2, |index| index as i32) /// .unwrap(); /// assert_eq!(*slice.into_slice_like_allocation(), [0, 1]); /// /// // Automatic conversion of an array into a slice is ambiguous, as the /// // compiler can't tell whether we want a slice with the same length as /// // the array or a slice with only one element containing the entire /// // array. We must explicitly specify the slice type in this example. /// let array = marker.allocate([9, 8, 7]).unwrap(); /// let array_slice: Allocation<[i32]> = array /// .into_slice_like_allocation(); /// assert_eq!(*array_slice, [9, 8, 7]); /// ``` /// /// [`SliceLike`]: trait.SliceLike.html #[inline] pub fn into_slice_like_allocation<U>(self) -> Allocation<'marker, U> where T: IntoMutSliceLikePtr<U>, U: SliceLike + ?Sized, { let data = unsafe { NonNull::new_unchecked(T::into_mut_slice_like_ptr( self.data.as_ptr(), )) }; forget(self); Allocation { data, _phantom: PhantomData, } } /// Combines this allocation with an allocation immediately following it /// in memory, returning a single slice allocation. /// /// Allocations must fulfill the following requirements to be able to be /// concatenated: /// /// - Each allocation must contain an instance, array, or slice of the /// same type. Any combination of these can be used. /// - Allocations must come from markers with the *exact* same lifetime. /// Concatenating allocations from different markers is possible, as the /// matching lifetimes ensure that neither marker can be invalidated /// before the combined allocation is dropped. /// - The first allocation must occupy the memory *immediately before* the /// second allocation. For allocations made from a [`MarkerBack`], this /// means that the allocations need to be specified in the reverse order /// in which they were made since back markers allocate memory /// downwards. /// - No gaps in memory can reside between the allocations, even if that /// memory is no longer in use. /// /// The first two requirements are checked at compile time, while the last /// two are checked at runtime. /// /// # Examples /// /// ``` /// use scratchpad::{ErrorKind, Scratchpad}; /// /// let scratchpad = Scratchpad::<[i32; 8], [usize; 2]>::static_new(); /// /// { /// let marker = scratchpad.mark_front().unwrap(); /// let a = marker.allocate(1).unwrap(); /// let b = marker.allocate([2, 3]).unwrap(); /// let c = marker.allocate_array_with(3, |index| index as i32 + 4) /// .unwrap(); /// /// // `a` and `c` cannot be concatenated since they are not adjacent. /// let error = a.concat(c).unwrap_err(); /// assert_eq!(error.kind(), ErrorKind::NotAdjacent); /// let (a, c) = error.unwrap_args(); /// /// // `a`, `b`, and `c` can be concatenated as long as adjacent /// // allocations are concatenated first. /// let abc = a.concat(b.concat(c).unwrap()).unwrap(); /// assert_eq!(*abc, [1, 2, 3, 4, 5, 6]); /// } /// /// { /// let marker = scratchpad.mark_back().unwrap(); /// let a = marker.allocate([1]).unwrap(); /// let b = marker.allocate([2, 3]).unwrap(); /// /// // When using a back marker, allocations must be concatenated in /// // the reverse order of creation. /// let error = a.concat::<[i32], _>(b).unwrap_err(); /// assert_eq!(error.kind(), ErrorKind::OutOfOrder); /// let (a, b) = error.unwrap_args(); /// /// let ba = b.concat::<[i32], _>(a).unwrap(); /// assert_eq!(*ba, [2, 3, 1]); /// } /// /// { /// // Both of the markers created here exist until the end of the /// // same scope, so their allocations can be concatenated. /// let marker_a = scratchpad.mark_front().unwrap(); /// let a = marker_a.allocate(1).unwrap(); /// let marker_b = scratchpad.mark_front().unwrap(); /// let b = marker_b.allocate(2).unwrap(); /// /// let ab = a.concat(b).unwrap(); /// assert_eq!(*ab, [1, 2]); /// } /// ``` /// /// [`MarkerBack`]: struct.MarkerBack.html #[allow(unknown_lints, type_complexity)] // Result type lint warning. pub fn concat<U, V>( self, other: Allocation<'marker, V>, ) -> Result< Allocation<'marker, U>, Error<(Allocation<'marker, T>, Allocation<'marker, V>)>, > where T: IntoMutSliceLikePtr<U>, U: ConcatenateSlice + ?Sized, V: IntoMutSliceLikePtr<U> + ?Sized, { unsafe { let data0 = (*T::into_mut_slice_like_ptr(self.data.as_ptr())) .as_element_slice(); let data1 = (*V::into_mut_slice_like_ptr(other.data.as_ptr())) .as_element_slice(); let data0_len = data0.len(); let data1_len = data1.len(); assert!(data0_len <= ::core::isize::MAX as usize); assert!(data1_len <= ::core::isize::MAX as usize); let data0_start = data0.as_ptr(); let data0_end = data0_start.offset(data0_len as isize); let data1_start = data1.as_ptr(); if data0_end != data1_start { return Err(Error::new( if data0_start < data1_start { ErrorKind::NotAdjacent } else { ErrorKind::OutOfOrder }, (self, other), )); } Ok(self.concat_unchecked(other)) } } /// Combines two allocations without performing any runtime checks. /// /// See the safe version, [`concat()`], for requirements and additional /// information. /// /// # Safety /// /// This function is unsafe because it does not check whether the /// allocations are adjacent in memory or whether they are specified in /// the correct order (with `self` residing immediately before `other` in /// memory). Calling this on allocations that do not fit these /// requirements can lead to memory corruption, undefined behavior, or /// crashes. /// /// # Examples /// /// ``` /// use scratchpad::{ErrorKind, Scratchpad}; /// /// let scratchpad = Scratchpad::<[i32; 3], [usize; 1]>::static_new(); /// let marker = scratchpad.mark_front().unwrap(); /// /// let a = marker.allocate(1).unwrap(); /// let b = marker.allocate([2, 3]).unwrap(); /// /// let ab = unsafe { a.concat_unchecked(b) }; /// assert_eq!(*ab, [1, 2, 3]); /// ``` /// /// [`concat()`]: #method.concat #[inline] pub unsafe fn concat_unchecked<U, V>( self, other: Allocation<'marker, V>, ) -> Allocation<'marker, U> where T: IntoMutSliceLikePtr<U>, U: ConcatenateSlice + ?Sized, V: IntoMutSliceLikePtr<U> + ?Sized, { let data0 = (*T::into_mut_slice_like_ptr(self.data.as_ptr())) .as_element_slice_mut(); let data1 = (*V::into_mut_slice_like_ptr(other.data.as_ptr())) .as_element_slice_mut(); forget(self); forget(other); Allocation { data: NonNull::new(<U as SliceLike>::from_element_slice_mut( slice::from_raw_parts_mut( data0.as_mut_ptr(), data0.len() + data1.len(), ), )).unwrap(), _phantom: PhantomData, } } } impl<'marker, T> Deref for Allocation<'marker, T> where T: ?Sized, { type Target = T; #[inline] fn deref(&self) -> &T { unsafe { self.data.as_ref() } } } impl<'marker, T> DerefMut for Allocation<'marker, T> where T: ?Sized, { #[inline] fn deref_mut(&mut self) -> &mut T { unsafe { self.data.as_mut() } } } impl<'marker, T> Drop for Allocation<'marker, T> where T: ?Sized, { #[inline] fn drop(&mut self) { unsafe { ptr::drop_in_place(self.data.as_ptr()) }; } } impl<'marker, T> fmt::Debug for Allocation<'marker, T> where T: ?Sized + fmt::Debug, { #[inline] fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { unsafe { write!(f, "Allocation {{ data: {:?} }}", self.data.as_ref()) } } }