vendor/generic-array/src/sequence.rs - toolchain/rustc - Git at Google

 //! Useful traits for manipulating sequences of data stored in `GenericArray`s

 use super::*;
 use core::ops::{Add, Sub};
 use core::mem::MaybeUninit;
 use core::ptr;
 use typenum::operator_aliases::*;

 /// Defines some sequence with an associated length and iteration capabilities.
 ///
 /// This is useful for passing N-length generic arrays as generics.
 pub unsafe trait GenericSequence<T>: Sized + IntoIterator {
     /// `GenericArray` associated length
     type Length: ArrayLength<T>;

     /// Concrete sequence type used in conjuction with reference implementations of `GenericSequence`
     type Sequence: GenericSequence<T, Length = Self::Length> + FromIterator<T>;

     /// Initializes a new sequence instance using the given function.
     ///
     /// If the generator function panics while initializing the sequence,
     /// any already initialized elements will be dropped.
     fn generate<F>(f: F) -> Self::Sequence
     where
         F: FnMut(usize) -> T;

     #[doc(hidden)]
     fn inverted_zip<B, U, F>(
         self,
         lhs: GenericArray<B, Self::Length>,
         mut f: F,
     ) -> MappedSequence<GenericArray<B, Self::Length>, B, U>
     where
         GenericArray<B, Self::Length>: GenericSequence<B, Length = Self::Length>
             + MappedGenericSequence<B, U>,
         Self: MappedGenericSequence<T, U>,
         Self::Length: ArrayLength<B> + ArrayLength<U>,
         F: FnMut(B, Self::Item) -> U,
     {
         unsafe {
             let mut left = ArrayConsumer::new(lhs);

             let (left_array_iter, left_position) = left.iter_position();

             FromIterator::from_iter(left_array_iter.zip(self.into_iter()).map(
                 |(l, right_value)| {
                         let left_value = ptr::read(l);

                         *left_position += 1;

                         f(left_value, right_value)
                 },
             ))
         }
     }

     #[doc(hidden)]
     fn inverted_zip2<B, Lhs, U, F>(self, lhs: Lhs, mut f: F) -> MappedSequence<Lhs, B, U>
     where
         Lhs: GenericSequence<B, Length = Self::Length> + MappedGenericSequence<B, U>,
         Self: MappedGenericSequence<T, U>,
         Self::Length: ArrayLength<B> + ArrayLength<U>,
         F: FnMut(Lhs::Item, Self::Item) -> U,
     {
         FromIterator::from_iter(lhs.into_iter().zip(self.into_iter()).map(|(l, r)| f(l, r)))
     }
 }

 /// Accessor for `GenericSequence` item type, which is really `IntoIterator::Item`
 ///
 /// For deeply nested generic mapped sequence types, like shown in `tests/generics.rs`,
 /// this can be useful for keeping things organized.
 pub type SequenceItem<T> = <T as IntoIterator>::Item;

 unsafe impl<'a, T: 'a, S: GenericSequence<T>> GenericSequence<T> for &'a S
 where
     &'a S: IntoIterator,
 {
     type Length = S::Length;
     type Sequence = S::Sequence;

     #[inline]
     fn generate<F>(f: F) -> Self::Sequence
     where
         F: FnMut(usize) -> T,
     {
         S::generate(f)
     }
 }

 unsafe impl<'a, T: 'a, S: GenericSequence<T>> GenericSequence<T> for &'a mut S
 where
     &'a mut S: IntoIterator,
 {
     type Length = S::Length;
     type Sequence = S::Sequence;

     #[inline]
     fn generate<F>(f: F) -> Self::Sequence
     where
         F: FnMut(usize) -> T,
     {
         S::generate(f)
     }
 }

 /// Defines any `GenericSequence` which can be lengthened or extended by appending
 /// or prepending an element to it.
 ///
 /// Any lengthened sequence can be shortened back to the original using `pop_front` or `pop_back`
 pub unsafe trait Lengthen<T>: Sized + GenericSequence<T> {
     /// `GenericSequence` that has one more element than `Self`
     type Longer: Shorten<T, Shorter = Self>;

     /// Returns a new array with the given element appended to the end of it.
     ///
     /// Example:
     ///
     /// ```rust
     /// # use generic_array::{arr, sequence::Lengthen};
     /// # fn main() {
     /// let a = arr![i32; 1, 2, 3];
     ///
     /// let b = a.append(4);
     ///
     /// assert_eq!(b, arr![i32; 1, 2, 3, 4]);
     /// # }
     /// ```
     fn append(self, last: T) -> Self::Longer;

     /// Returns a new array with the given element prepended to the front of it.
     ///
     /// Example:
     ///
     /// ```rust
     /// # use generic_array::{arr, sequence::Lengthen};
     /// # fn main() {
     /// let a = arr![i32; 1, 2, 3];
     ///
     /// let b = a.prepend(4);
     ///
     /// assert_eq!(b, arr![i32; 4, 1, 2, 3]);
     /// # }
     /// ```
     fn prepend(self, first: T) -> Self::Longer;
 }

 /// Defines a `GenericSequence` which can be shortened by removing the first or last element from it.
 ///
 /// Additionally, any shortened sequence can be lengthened by
 /// appending or prepending an element to it.
 pub unsafe trait Shorten<T>: Sized + GenericSequence<T> {
     /// `GenericSequence` that has one less element than `Self`
     type Shorter: Lengthen<T, Longer = Self>;

     /// Returns a new array without the last element, and the last element.
     ///
     /// Example:
     ///
     /// ```rust
     /// # use generic_array::{arr, sequence::Shorten};
     /// # fn main() {
     /// let a = arr![i32; 1, 2, 3, 4];
     ///
     /// let (init, last) = a.pop_back();
     ///
     /// assert_eq!(init, arr![i32; 1, 2, 3]);
     /// assert_eq!(last, 4);
     /// # }
     /// ```
     fn pop_back(self) -> (Self::Shorter, T);

     /// Returns a new array without the first element, and the first element.
     /// Example:
     ///
     /// ```rust
     /// # use generic_array::{arr, sequence::Shorten};
     /// # fn main() {
     /// let a = arr![i32; 1, 2, 3, 4];
     ///
     /// let (head, tail) = a.pop_front();
     ///
     /// assert_eq!(head, 1);
     /// assert_eq!(tail, arr![i32; 2, 3, 4]);
     /// # }
     /// ```
     fn pop_front(self) -> (T, Self::Shorter);
 }

 unsafe impl<T, N: ArrayLength<T>> Lengthen<T> for GenericArray<T, N>
 where
     N: Add<B1>,
     Add1<N>: ArrayLength<T>,
     Add1<N>: Sub<B1, Output = N>,
     Sub1<Add1<N>>: ArrayLength<T>,
 {
     type Longer = GenericArray<T, Add1<N>>;

     fn append(self, last: T) -> Self::Longer {
         let mut longer: MaybeUninit<Self::Longer> = MaybeUninit::uninit();

         // Note this is *mut Self, so add(1) increments by the whole array
         let out_ptr = longer.as_mut_ptr() as *mut Self;

         unsafe {
             // write self first
             ptr::write(out_ptr, self);
             // increment past self, then write the last
             ptr::write(out_ptr.add(1) as *mut T, last);

             longer.assume_init()
         }
     }

     fn prepend(self, first: T) -> Self::Longer {
         let mut longer: MaybeUninit<Self::Longer> = MaybeUninit::uninit();

         // Note this is *mut T, so add(1) increments by a single T
         let out_ptr = longer.as_mut_ptr() as *mut T;

         unsafe {
             // write the first at the start
             ptr::write(out_ptr, first);
             // increment past the first, then write self
             ptr::write(out_ptr.add(1) as *mut Self, self);

             longer.assume_init()
         }
     }
 }

 unsafe impl<T, N: ArrayLength<T>> Shorten<T> for GenericArray<T, N>
 where
     N: Sub<B1>,
     Sub1<N>: ArrayLength<T>,
     Sub1<N>: Add<B1, Output = N>,
     Add1<Sub1<N>>: ArrayLength<T>,
 {
     type Shorter = GenericArray<T, Sub1<N>>;

     fn pop_back(self) -> (Self::Shorter, T) {
         let whole = ManuallyDrop::new(self);

         unsafe {
             let init = ptr::read(whole.as_ptr() as _);
             let last = ptr::read(whole.as_ptr().add(Sub1::<N>::USIZE) as _);

             (init, last)
         }
     }

     fn pop_front(self) -> (T, Self::Shorter) {
         // ensure this doesn't get dropped
         let whole = ManuallyDrop::new(self);

         unsafe {
             let head = ptr::read(whole.as_ptr() as _);
             let tail = ptr::read(whole.as_ptr().offset(1) as _);

             (head, tail)
         }
     }
 }

 /// Defines a `GenericSequence` that can be split into two parts at a given pivot index.
 pub unsafe trait Split<T, K>: GenericSequence<T>
 where
     K: ArrayLength<T>,
 {
     /// First part of the resulting split array
     type First: GenericSequence<T>;
     /// Second part of the resulting split array
     type Second: GenericSequence<T>;

     /// Splits an array at the given index, returning the separate parts of the array.
     fn split(self) -> (Self::First, Self::Second);
 }

 unsafe impl<T, N, K> Split<T, K> for GenericArray<T, N>
 where
     N: ArrayLength<T>,
     K: ArrayLength<T>,
     N: Sub<K>,
     Diff<N, K>: ArrayLength<T>,
 {
     type First = GenericArray<T, K>;
     type Second = GenericArray<T, Diff<N, K>>;

     fn split(self) -> (Self::First, Self::Second) {
         unsafe {
             // ensure this doesn't get dropped
             let whole = ManuallyDrop::new(self);

             let head = ptr::read(whole.as_ptr() as *const _);
             let tail = ptr::read(whole.as_ptr().add(K::USIZE) as *const _);

             (head, tail)
         }
     }
 }

 unsafe impl<'a, T, N, K> Split<T, K> for &'a GenericArray<T, N>
 where
     N: ArrayLength<T>,
     K: ArrayLength<T> + 'static,
     N: Sub<K>,
     Diff<N, K>: ArrayLength<T>,
 {
     type First = &'a GenericArray<T, K>;
     type Second = &'a GenericArray<T, Diff<N, K>>;

     fn split(self) -> (Self::First, Self::Second) {
         unsafe {
             let ptr_to_first: *const T = self.as_ptr();
             let head = &*(ptr_to_first as *const _);
             let tail = &*(ptr_to_first.add(K::USIZE) as *const _);
             (head, tail)
         }
     }
 }

 unsafe impl<'a, T, N, K> Split<T, K> for &'a mut GenericArray<T, N>
 where
     N: ArrayLength<T>,
     K: ArrayLength<T> + 'static,
     N: Sub<K>,
     Diff<N, K>: ArrayLength<T>,
 {
     type First = &'a mut GenericArray<T, K>;
     type Second = &'a mut GenericArray<T, Diff<N, K>>;

     fn split(self) -> (Self::First, Self::Second) {
         unsafe {
             let ptr_to_first: *mut T = self.as_mut_ptr();
             let head = &mut *(ptr_to_first as *mut _);
             let tail = &mut *(ptr_to_first.add(K::USIZE) as *mut _);
             (head, tail)
         }
     }
 }

 /// Defines `GenericSequence`s which can be joined together, forming a larger array.
 pub unsafe trait Concat<T, M>: GenericSequence<T>
 where
     M: ArrayLength<T>,
 {
     /// Sequence to be concatenated with `self`
     type Rest: GenericSequence<T, Length = M>;

     /// Resulting sequence formed by the concatenation.
     type Output: GenericSequence<T>;

     /// Concatenate, or join, two sequences.
     fn concat(self, rest: Self::Rest) -> Self::Output;
 }

 unsafe impl<T, N, M> Concat<T, M> for GenericArray<T, N>
 where
     N: ArrayLength<T> + Add<M>,
     M: ArrayLength<T>,
     Sum<N, M>: ArrayLength<T>,
 {
     type Rest = GenericArray<T, M>;
     type Output = GenericArray<T, Sum<N, M>>;

     fn concat(self, rest: Self::Rest) -> Self::Output {
         let mut output: MaybeUninit<Self::Output> = MaybeUninit::uninit();

         let out_ptr = output.as_mut_ptr() as *mut Self;

         unsafe {
             // write all of self to the pointer
             ptr::write(out_ptr, self);
             // increment past self, then write the rest
             ptr::write(out_ptr.add(1) as *mut _, rest);

             output.assume_init()
         }
     }
 }
	//! Useful traits for manipulating sequences of data stored in `GenericArray`s

	use super::*;
	use core::ops::{Add, Sub};
	use core::mem::MaybeUninit;
	use core::ptr;
	use typenum::operator_aliases::*;

	/// Defines some sequence with an associated length and iteration capabilities.
	///
	/// This is useful for passing N-length generic arrays as generics.
	pub unsafe trait GenericSequence<T>: Sized + IntoIterator {
	/// `GenericArray` associated length
	type Length: ArrayLength<T>;

	/// Concrete sequence type used in conjuction with reference implementations of `GenericSequence`
	type Sequence: GenericSequence<T, Length = Self::Length> + FromIterator<T>;

	/// Initializes a new sequence instance using the given function.
	///
	/// If the generator function panics while initializing the sequence,
	/// any already initialized elements will be dropped.
	fn generate<F>(f: F) -> Self::Sequence
	where
	F: FnMut(usize) -> T;

	#[doc(hidden)]
	fn inverted_zip<B, U, F>(
	self,
	lhs: GenericArray<B, Self::Length>,
	mut f: F,
	) -> MappedSequence<GenericArray<B, Self::Length>, B, U>
	where
	GenericArray<B, Self::Length>: GenericSequence<B, Length = Self::Length>
	+ MappedGenericSequence<B, U>,
	Self: MappedGenericSequence<T, U>,
	Self::Length: ArrayLength<B> + ArrayLength<U>,
	F: FnMut(B, Self::Item) -> U,
	{
	unsafe {
	let mut left = ArrayConsumer::new(lhs);

	let (left_array_iter, left_position) = left.iter_position();

	FromIterator::from_iter(left_array_iter.zip(self.into_iter()).map(
	\|(l, right_value)\| {
	let left_value = ptr::read(l);

	*left_position += 1;

	f(left_value, right_value)
	},
	))
	}
	}

	#[doc(hidden)]
	fn inverted_zip2<B, Lhs, U, F>(self, lhs: Lhs, mut f: F) -> MappedSequence<Lhs, B, U>
	where
	Lhs: GenericSequence<B, Length = Self::Length> + MappedGenericSequence<B, U>,
	Self: MappedGenericSequence<T, U>,
	Self::Length: ArrayLength<B> + ArrayLength<U>,
	F: FnMut(Lhs::Item, Self::Item) -> U,
	{
	FromIterator::from_iter(lhs.into_iter().zip(self.into_iter()).map(\|(l, r)\| f(l, r)))
	}
	}

	/// Accessor for `GenericSequence` item type, which is really `IntoIterator::Item`
	///
	/// For deeply nested generic mapped sequence types, like shown in `tests/generics.rs`,
	/// this can be useful for keeping things organized.
	pub type SequenceItem<T> = <T as IntoIterator>::Item;

	unsafe impl<'a, T: 'a, S: GenericSequence<T>> GenericSequence<T> for &'a S
	where
	&'a S: IntoIterator,
	{
	type Length = S::Length;
	type Sequence = S::Sequence;

	#[inline]
	fn generate<F>(f: F) -> Self::Sequence
	where
	F: FnMut(usize) -> T,
	{
	S::generate(f)
	}
	}

	unsafe impl<'a, T: 'a, S: GenericSequence<T>> GenericSequence<T> for &'a mut S
	where
	&'a mut S: IntoIterator,
	{
	type Length = S::Length;
	type Sequence = S::Sequence;

	#[inline]
	fn generate<F>(f: F) -> Self::Sequence
	where
	F: FnMut(usize) -> T,
	{
	S::generate(f)
	}
	}

	/// Defines any `GenericSequence` which can be lengthened or extended by appending
	/// or prepending an element to it.
	///
	/// Any lengthened sequence can be shortened back to the original using `pop_front` or `pop_back`
	pub unsafe trait Lengthen<T>: Sized + GenericSequence<T> {
	/// `GenericSequence` that has one more element than `Self`
	type Longer: Shorten<T, Shorter = Self>;

	/// Returns a new array with the given element appended to the end of it.
	///
	/// Example:
	///
	/// ```rust
	/// # use generic_array::{arr, sequence::Lengthen};
	/// # fn main() {
	/// let a = arr![i32; 1, 2, 3];
	///
	/// let b = a.append(4);
	///
	/// assert_eq!(b, arr![i32; 1, 2, 3, 4]);
	/// # }
	/// ```
	fn append(self, last: T) -> Self::Longer;

	/// Returns a new array with the given element prepended to the front of it.
	///
	/// Example:
	///
	/// ```rust
	/// # use generic_array::{arr, sequence::Lengthen};
	/// # fn main() {
	/// let a = arr![i32; 1, 2, 3];
	///
	/// let b = a.prepend(4);
	///
	/// assert_eq!(b, arr![i32; 4, 1, 2, 3]);
	/// # }
	/// ```
	fn prepend(self, first: T) -> Self::Longer;
	}

	/// Defines a `GenericSequence` which can be shortened by removing the first or last element from it.
	///
	/// Additionally, any shortened sequence can be lengthened by
	/// appending or prepending an element to it.
	pub unsafe trait Shorten<T>: Sized + GenericSequence<T> {
	/// `GenericSequence` that has one less element than `Self`
	type Shorter: Lengthen<T, Longer = Self>;

	/// Returns a new array without the last element, and the last element.
	///
	/// Example:
	///
	/// ```rust
	/// # use generic_array::{arr, sequence::Shorten};
	/// # fn main() {
	/// let a = arr![i32; 1, 2, 3, 4];
	///
	/// let (init, last) = a.pop_back();
	///
	/// assert_eq!(init, arr![i32; 1, 2, 3]);
	/// assert_eq!(last, 4);
	/// # }
	/// ```
	fn pop_back(self) -> (Self::Shorter, T);

	/// Returns a new array without the first element, and the first element.
	/// Example:
	///
	/// ```rust
	/// # use generic_array::{arr, sequence::Shorten};
	/// # fn main() {
	/// let a = arr![i32; 1, 2, 3, 4];
	///
	/// let (head, tail) = a.pop_front();
	///
	/// assert_eq!(head, 1);
	/// assert_eq!(tail, arr![i32; 2, 3, 4]);
	/// # }
	/// ```
	fn pop_front(self) -> (T, Self::Shorter);
	}

	unsafe impl<T, N: ArrayLength<T>> Lengthen<T> for GenericArray<T, N>
	where
	N: Add<B1>,
	Add1<N>: ArrayLength<T>,
	Add1<N>: Sub<B1, Output = N>,
	Sub1<Add1<N>>: ArrayLength<T>,
	{
	type Longer = GenericArray<T, Add1<N>>;

	fn append(self, last: T) -> Self::Longer {
	let mut longer: MaybeUninit<Self::Longer> = MaybeUninit::uninit();

	// Note this is *mut Self, so add(1) increments by the whole array
	let out_ptr = longer.as_mut_ptr() as *mut Self;

	unsafe {
	// write self first
	ptr::write(out_ptr, self);
	// increment past self, then write the last
	ptr::write(out_ptr.add(1) as *mut T, last);

	longer.assume_init()
	}
	}

	fn prepend(self, first: T) -> Self::Longer {
	let mut longer: MaybeUninit<Self::Longer> = MaybeUninit::uninit();

	// Note this is *mut T, so add(1) increments by a single T
	let out_ptr = longer.as_mut_ptr() as *mut T;

	unsafe {
	// write the first at the start
	ptr::write(out_ptr, first);
	// increment past the first, then write self
	ptr::write(out_ptr.add(1) as *mut Self, self);

	longer.assume_init()
	}
	}
	}

	unsafe impl<T, N: ArrayLength<T>> Shorten<T> for GenericArray<T, N>
	where
	N: Sub<B1>,
	Sub1<N>: ArrayLength<T>,
	Sub1<N>: Add<B1, Output = N>,
	Add1<Sub1<N>>: ArrayLength<T>,
	{
	type Shorter = GenericArray<T, Sub1<N>>;

	fn pop_back(self) -> (Self::Shorter, T) {
	let whole = ManuallyDrop::new(self);

	unsafe {
	let init = ptr::read(whole.as_ptr() as _);
	let last = ptr::read(whole.as_ptr().add(Sub1::<N>::USIZE) as _);

	(init, last)
	}
	}

	fn pop_front(self) -> (T, Self::Shorter) {
	// ensure this doesn't get dropped
	let whole = ManuallyDrop::new(self);

	unsafe {
	let head = ptr::read(whole.as_ptr() as _);
	let tail = ptr::read(whole.as_ptr().offset(1) as _);

	(head, tail)
	}
	}
	}

	/// Defines a `GenericSequence` that can be split into two parts at a given pivot index.
	pub unsafe trait Split<T, K>: GenericSequence<T>
	where
	K: ArrayLength<T>,
	{
	/// First part of the resulting split array
	type First: GenericSequence<T>;
	/// Second part of the resulting split array
	type Second: GenericSequence<T>;

	/// Splits an array at the given index, returning the separate parts of the array.
	fn split(self) -> (Self::First, Self::Second);
	}

	unsafe impl<T, N, K> Split<T, K> for GenericArray<T, N>
	where
	N: ArrayLength<T>,
	K: ArrayLength<T>,
	N: Sub<K>,
	Diff<N, K>: ArrayLength<T>,
	{
	type First = GenericArray<T, K>;
	type Second = GenericArray<T, Diff<N, K>>;

	fn split(self) -> (Self::First, Self::Second) {
	unsafe {
	// ensure this doesn't get dropped
	let whole = ManuallyDrop::new(self);

	let head = ptr::read(whole.as_ptr() as *const _);
	let tail = ptr::read(whole.as_ptr().add(K::USIZE) as *const _);

	(head, tail)
	}
	}
	}

	unsafe impl<'a, T, N, K> Split<T, K> for &'a GenericArray<T, N>
	where
	N: ArrayLength<T>,
	K: ArrayLength<T> + 'static,
	N: Sub<K>,
	Diff<N, K>: ArrayLength<T>,
	{
	type First = &'a GenericArray<T, K>;
	type Second = &'a GenericArray<T, Diff<N, K>>;

	fn split(self) -> (Self::First, Self::Second) {
	unsafe {
	let ptr_to_first: *const T = self.as_ptr();
	let head = &(ptr_to_first as const _);
	let tail = &(ptr_to_first.add(K::USIZE) as const _);
	(head, tail)
	}
	}
	}

	unsafe impl<'a, T, N, K> Split<T, K> for &'a mut GenericArray<T, N>
	where
	N: ArrayLength<T>,
	K: ArrayLength<T> + 'static,
	N: Sub<K>,
	Diff<N, K>: ArrayLength<T>,
	{
	type First = &'a mut GenericArray<T, K>;
	type Second = &'a mut GenericArray<T, Diff<N, K>>;

	fn split(self) -> (Self::First, Self::Second) {
	unsafe {
	let ptr_to_first: *mut T = self.as_mut_ptr();
	let head = &mut (ptr_to_first as mut _);
	let tail = &mut (ptr_to_first.add(K::USIZE) as mut _);
	(head, tail)
	}
	}
	}

	/// Defines `GenericSequence`s which can be joined together, forming a larger array.
	pub unsafe trait Concat<T, M>: GenericSequence<T>
	where
	M: ArrayLength<T>,
	{
	/// Sequence to be concatenated with `self`
	type Rest: GenericSequence<T, Length = M>;

	/// Resulting sequence formed by the concatenation.
	type Output: GenericSequence<T>;

	/// Concatenate, or join, two sequences.
	fn concat(self, rest: Self::Rest) -> Self::Output;
	}

	unsafe impl<T, N, M> Concat<T, M> for GenericArray<T, N>
	where
	N: ArrayLength<T> + Add<M>,
	M: ArrayLength<T>,
	Sum<N, M>: ArrayLength<T>,
	{
	type Rest = GenericArray<T, M>;
	type Output = GenericArray<T, Sum<N, M>>;

	fn concat(self, rest: Self::Rest) -> Self::Output {
	let mut output: MaybeUninit<Self::Output> = MaybeUninit::uninit();

	let out_ptr = output.as_mut_ptr() as *mut Self;

	unsafe {
	// write all of self to the pointer
	ptr::write(out_ptr, self);
	// increment past self, then write the rest
	ptr::write(out_ptr.add(1) as *mut _, rest);

	output.assume_init()
	}
	}
	}