diff options
Diffstat (limited to 'rust/alloc/vec/mod.rs')
| -rw-r--r-- | rust/alloc/vec/mod.rs | 286 |
1 files changed, 283 insertions, 3 deletions
diff --git a/rust/alloc/vec/mod.rs b/rust/alloc/vec/mod.rs index 540787804cc2..4ae81b890fd9 100644 --- a/rust/alloc/vec/mod.rs +++ b/rust/alloc/vec/mod.rs @@ -120,10 +120,8 @@ use self::spec_from_elem::SpecFromElem; #[cfg(not(no_global_oom_handling))] mod spec_from_elem; -#[cfg(not(no_global_oom_handling))] use self::set_len_on_drop::SetLenOnDrop; -#[cfg(not(no_global_oom_handling))] mod set_len_on_drop; #[cfg(not(no_global_oom_handling))] @@ -147,7 +145,8 @@ mod spec_from_iter; #[cfg(not(no_global_oom_handling))] use self::spec_extend::SpecExtend; -#[cfg(not(no_global_oom_handling))] +use self::spec_extend::TrySpecExtend; + mod spec_extend; /// A contiguous growable array type, written as `Vec<T>`, short for 'vector'. @@ -472,6 +471,48 @@ impl<T> Vec<T> { Self::with_capacity_in(capacity, Global) } + /// Tries to construct a new, empty `Vec<T>` with the specified capacity. + /// + /// The vector will be able to hold exactly `capacity` elements without + /// reallocating. If `capacity` is 0, the vector will not allocate. + /// + /// It is important to note that although the returned vector has the + /// *capacity* specified, the vector will have a zero *length*. For an + /// explanation of the difference between length and capacity, see + /// *[Capacity and reallocation]*. + /// + /// [Capacity and reallocation]: #capacity-and-reallocation + /// + /// # Examples + /// + /// ``` + /// let mut vec = Vec::try_with_capacity(10).unwrap(); + /// + /// // The vector contains no items, even though it has capacity for more + /// assert_eq!(vec.len(), 0); + /// assert_eq!(vec.capacity(), 10); + /// + /// // These are all done without reallocating... + /// for i in 0..10 { + /// vec.push(i); + /// } + /// assert_eq!(vec.len(), 10); + /// assert_eq!(vec.capacity(), 10); + /// + /// // ...but this may make the vector reallocate + /// vec.push(11); + /// assert_eq!(vec.len(), 11); + /// assert!(vec.capacity() >= 11); + /// + /// let mut result = Vec::try_with_capacity(usize::MAX); + /// assert!(result.is_err()); + /// ``` + #[inline] + #[stable(feature = "kernel", since = "1.0.0")] + pub fn try_with_capacity(capacity: usize) -> Result<Self, TryReserveError> { + Self::try_with_capacity_in(capacity, Global) + } + /// Creates a `Vec<T>` directly from the raw components of another vector. /// /// # Safety @@ -617,6 +658,53 @@ impl<T, A: Allocator> Vec<T, A> { Vec { buf: RawVec::with_capacity_in(capacity, alloc), len: 0 } } + /// Tries to construct a new, empty `Vec<T, A>` with the specified capacity + /// with the provided allocator. + /// + /// The vector will be able to hold exactly `capacity` elements without + /// reallocating. If `capacity` is 0, the vector will not allocate. + /// + /// It is important to note that although the returned vector has the + /// *capacity* specified, the vector will have a zero *length*. For an + /// explanation of the difference between length and capacity, see + /// *[Capacity and reallocation]*. + /// + /// [Capacity and reallocation]: #capacity-and-reallocation + /// + /// # Examples + /// + /// ``` + /// #![feature(allocator_api)] + /// + /// use std::alloc::System; + /// + /// let mut vec = Vec::try_with_capacity_in(10, System).unwrap(); + /// + /// // The vector contains no items, even though it has capacity for more + /// assert_eq!(vec.len(), 0); + /// assert_eq!(vec.capacity(), 10); + /// + /// // These are all done without reallocating... + /// for i in 0..10 { + /// vec.push(i); + /// } + /// assert_eq!(vec.len(), 10); + /// assert_eq!(vec.capacity(), 10); + /// + /// // ...but this may make the vector reallocate + /// vec.push(11); + /// assert_eq!(vec.len(), 11); + /// assert!(vec.capacity() >= 11); + /// + /// let mut result = Vec::try_with_capacity_in(usize::MAX, System); + /// assert!(result.is_err()); + /// ``` + #[inline] + #[stable(feature = "kernel", since = "1.0.0")] + pub fn try_with_capacity_in(capacity: usize, alloc: A) -> Result<Self, TryReserveError> { + Ok(Vec { buf: RawVec::try_with_capacity_in(capacity, alloc)?, len: 0 }) + } + /// Creates a `Vec<T, A>` directly from the raw components of another vector. /// /// # Safety @@ -948,6 +1036,32 @@ impl<T, A: Allocator> Vec<T, A> { } } + /// Tries to shrink the capacity of the vector as much as possible. + /// + /// It will drop down as close as possible to the length but the allocator + /// may still inform the vector that there is space for a few more elements. + /// + /// # Examples + /// + /// ``` + /// let mut vec = Vec::with_capacity(10); + /// vec.extend([1, 2, 3]); + /// assert_eq!(vec.capacity(), 10); + /// vec.try_shrink_to_fit().unwrap(); + /// assert!(vec.capacity() >= 3); + /// ``` + #[stable(feature = "kernel", since = "1.0.0")] + pub fn try_shrink_to_fit(&mut self) -> Result<(), TryReserveError> { + // The capacity is never less than the length, and there's nothing to do when + // they are equal, so we can avoid the panic case in `RawVec::try_shrink_to_fit` + // by only calling it with a greater capacity. + if self.capacity() <= self.len { + return Ok(()); + } + + self.buf.try_shrink_to_fit(self.len) + } + /// Shrinks the capacity of the vector with a lower bound. /// /// The capacity will remain at least as large as both the length @@ -1010,6 +1124,41 @@ impl<T, A: Allocator> Vec<T, A> { } } + /// Tries to convert the vector into [`Box<[T]>`][owned slice]. + /// + /// Note that this will drop any excess capacity. + /// + /// [owned slice]: Box + /// + /// # Examples + /// + /// ``` + /// let v = vec![1, 2, 3]; + /// + /// let slice = v.try_into_boxed_slice().unwrap(); + /// ``` + /// + /// Any excess capacity is removed: + /// + /// ``` + /// let mut vec = Vec::with_capacity(10); + /// vec.extend([1, 2, 3]); + /// + /// assert_eq!(vec.capacity(), 10); + /// let slice = vec.try_into_boxed_slice().unwrap(); + /// assert_eq!(slice.into_vec().capacity(), 3); + /// ``` + #[stable(feature = "kernel", since = "1.0.0")] + pub fn try_into_boxed_slice(mut self) -> Result<Box<[T], A>, TryReserveError> { + unsafe { + self.try_shrink_to_fit()?; + let me = ManuallyDrop::new(self); + let buf = ptr::read(&me.buf); + let len = me.len(); + Ok(buf.into_box(len).assume_init()) + } + } + /// Shortens the vector, keeping the first `len` elements and dropping /// the rest. /// @@ -1828,6 +1977,17 @@ impl<T, A: Allocator> Vec<T, A> { self.len += count; } + /// Tries to append elements to `self` from other buffer. + #[inline] + unsafe fn try_append_elements(&mut self, other: *const [T]) -> Result<(), TryReserveError> { + let count = unsafe { (*other).len() }; + self.try_reserve(count)?; + let len = self.len(); + unsafe { ptr::copy_nonoverlapping(other as *const T, self.as_mut_ptr().add(len), count) }; + self.len += count; + Ok(()) + } + /// Removes the specified range from the vector in bulk, returning all /// removed elements as an iterator. If the iterator is dropped before /// being fully consumed, it drops the remaining removed elements. @@ -2249,6 +2409,44 @@ impl<T: Clone, A: Allocator> Vec<T, A> { } } + /// Tries to resize the `Vec` in-place so that `len` is equal to `new_len`. + /// + /// If `new_len` is greater than `len`, the `Vec` is extended by the + /// difference, with each additional slot filled with `value`. + /// If `new_len` is less than `len`, the `Vec` is simply truncated. + /// + /// This method requires `T` to implement [`Clone`], + /// in order to be able to clone the passed value. + /// If you need more flexibility (or want to rely on [`Default`] instead of + /// [`Clone`]), use [`Vec::resize_with`]. + /// + /// # Examples + /// + /// ``` + /// let mut vec = vec!["hello"]; + /// vec.try_resize(3, "world").unwrap(); + /// assert_eq!(vec, ["hello", "world", "world"]); + /// + /// let mut vec = vec![1, 2, 3, 4]; + /// vec.try_resize(2, 0).unwrap(); + /// assert_eq!(vec, [1, 2]); + /// + /// let mut vec = vec![42]; + /// let result = vec.try_resize(usize::MAX, 0); + /// assert!(result.is_err()); + /// ``` + #[stable(feature = "kernel", since = "1.0.0")] + pub fn try_resize(&mut self, new_len: usize, value: T) -> Result<(), TryReserveError> { + let len = self.len(); + + if new_len > len { + self.try_extend_with(new_len - len, ExtendElement(value)) + } else { + self.truncate(new_len); + Ok(()) + } + } + /// Clones and appends all elements in a slice to the `Vec`. /// /// Iterates over the slice `other`, clones each element, and then appends @@ -2274,6 +2472,30 @@ impl<T: Clone, A: Allocator> Vec<T, A> { self.spec_extend(other.iter()) } + /// Tries to clone and append all elements in a slice to the `Vec`. + /// + /// Iterates over the slice `other`, clones each element, and then appends + /// it to this `Vec`. The `other` slice is traversed in-order. + /// + /// Note that this function is same as [`extend`] except that it is + /// specialized to work with slices instead. If and when Rust gets + /// specialization this function will likely be deprecated (but still + /// available). + /// + /// # Examples + /// + /// ``` + /// let mut vec = vec![1]; + /// vec.try_extend_from_slice(&[2, 3, 4]).unwrap(); + /// assert_eq!(vec, [1, 2, 3, 4]); + /// ``` + /// + /// [`extend`]: Vec::extend + #[stable(feature = "kernel", since = "1.0.0")] + pub fn try_extend_from_slice(&mut self, other: &[T]) -> Result<(), TryReserveError> { + self.try_spec_extend(other.iter()) + } + /// Copies elements from `src` range to the end of the vector. /// /// # Panics @@ -2413,6 +2635,36 @@ impl<T, A: Allocator> Vec<T, A> { // len set by scope guard } } + + /// Try to extend the vector by `n` values, using the given generator. + fn try_extend_with<E: ExtendWith<T>>(&mut self, n: usize, mut value: E) -> Result<(), TryReserveError> { + self.try_reserve(n)?; + + unsafe { + let mut ptr = self.as_mut_ptr().add(self.len()); + // Use SetLenOnDrop to work around bug where compiler + // might not realize the store through `ptr` through self.set_len() + // don't alias. + let mut local_len = SetLenOnDrop::new(&mut self.len); + + // Write all elements except the last one + for _ in 1..n { + ptr::write(ptr, value.next()); + ptr = ptr.offset(1); + // Increment the length in every step in case next() panics + local_len.increment_len(1); + } + + if n > 0 { + // We can write the last element directly without cloning needlessly + ptr::write(ptr, value.last()); + local_len.increment_len(1); + } + + // len set by scope guard + Ok(()) + } + } } impl<T: PartialEq, A: Allocator> Vec<T, A> { @@ -2747,6 +2999,34 @@ impl<T, A: Allocator> Vec<T, A> { } } + // leaf method to which various SpecFrom/SpecExtend implementations delegate when + // they have no further optimizations to apply + fn try_extend_desugared<I: Iterator<Item = T>>(&mut self, mut iterator: I) -> Result<(), TryReserveError> { + // This is the case for a general iterator. + // + // This function should be the moral equivalent of: + // + // for item in iterator { + // self.push(item); + // } + while let Some(element) = iterator.next() { + let len = self.len(); + if len == self.capacity() { + let (lower, _) = iterator.size_hint(); + self.try_reserve(lower.saturating_add(1))?; + } + unsafe { + ptr::write(self.as_mut_ptr().add(len), element); + // Since next() executes user code which can panic we have to bump the length + // after each step. + // NB can't overflow since we would have had to alloc the address space + self.set_len(len + 1); + } + } + + Ok(()) + } + /// Creates a splicing iterator that replaces the specified range in the vector /// with the given `replace_with` iterator and yields the removed items. /// `replace_with` does not need to be the same length as `range`. |