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//! A contiguous growable array type with heap-allocated contents, written //! `Vec<T>`. //! //! Vectors have `O(1)` indexing, amortized `O(1)` push (to the end) and //! `O(1)` pop (from the end). //! //! # Examples //! //! You can explicitly create a [`Vec<T>`] with [`new`]: //! //! ``` //! let v: Vec<i32> = Vec::new(); //! ``` //! //! ...or by using the [`vec!`] macro: //! //! ``` //! let v: Vec<i32> = vec![]; //! //! let v = vec![1, 2, 3, 4, 5]; //! //! let v = vec![0; 10]; // ten zeroes //! ``` //! //! You can [`push`] values onto the end of a vector (which will grow the vector //! as needed): //! //! ``` //! let mut v = vec![1, 2]; //! //! v.push(3); //! ``` //! //! Popping values works in much the same way: //! //! ``` //! let mut v = vec![1, 2]; //! //! let two = v.pop(); //! ``` //! //! Vectors also support indexing (through the [`Index`] and [`IndexMut`] traits): //! //! ``` //! let mut v = vec![1, 2, 3]; //! let three = v[2]; //! v[1] = v[1] + 5; //! ``` //! //! [`Vec<T>`]: ../../std/vec/struct.Vec.html //! [`new`]: ../../std/vec/struct.Vec.html#method.new //! [`push`]: ../../std/vec/struct.Vec.html#method.push //! [`Index`]: ../../std/ops/trait.Index.html //! [`IndexMut`]: ../../std/ops/trait.IndexMut.html //! [`vec!`]: ../../std/macro.vec.html #![stable(feature = "rust1", since = "1.0.0")] use core::array::LengthAtMost32; use core::cmp::{self, Ordering}; use core::fmt; use core::hash::{self, Hash}; use core::intrinsics::{arith_offset, assume}; use core::iter::{FromIterator, FusedIterator, TrustedLen}; use core::marker::PhantomData; use core::mem; use core::ops::{self, Index, IndexMut, RangeBounds}; use core::ops::Bound::{Excluded, Included, Unbounded}; use core::ptr::{self, NonNull}; use core::slice::{self, SliceIndex}; use crate::borrow::{ToOwned, Cow}; use crate::collections::TryReserveError; use crate::boxed::Box; use crate::raw_vec::RawVec; /// A contiguous growable array type, written `Vec<T>` but pronounced 'vector'. /// /// # Examples /// /// ``` /// let mut vec = Vec::new(); /// vec.push(1); /// vec.push(2); /// /// assert_eq!(vec.len(), 2); /// assert_eq!(vec[0], 1); /// /// assert_eq!(vec.pop(), Some(2)); /// assert_eq!(vec.len(), 1); /// /// vec[0] = 7; /// assert_eq!(vec[0], 7); /// /// vec.extend([1, 2, 3].iter().cloned()); /// /// for x in &vec { /// println!("{}", x); /// } /// assert_eq!(vec, [7, 1, 2, 3]); /// ``` /// /// The [`vec!`] macro is provided to make initialization more convenient: /// /// ``` /// let mut vec = vec![1, 2, 3]; /// vec.push(4); /// assert_eq!(vec, [1, 2, 3, 4]); /// ``` /// /// It can also initialize each element of a `Vec<T>` with a given value. /// This may be more efficient than performing allocation and initialization /// in separate steps, especially when initializing a vector of zeros: /// /// ``` /// let vec = vec![0; 5]; /// assert_eq!(vec, [0, 0, 0, 0, 0]); /// /// // The following is equivalent, but potentially slower: /// let mut vec1 = Vec::with_capacity(5); /// vec1.resize(5, 0); /// ``` /// /// Use a `Vec<T>` as an efficient stack: /// /// ``` /// let mut stack = Vec::new(); /// /// stack.push(1); /// stack.push(2); /// stack.push(3); /// /// while let Some(top) = stack.pop() { /// // Prints 3, 2, 1 /// println!("{}", top); /// } /// ``` /// /// # Indexing /// /// The `Vec` type allows to access values by index, because it implements the /// [`Index`] trait. An example will be more explicit: /// /// ``` /// let v = vec![0, 2, 4, 6]; /// println!("{}", v[1]); // it will display '2' /// ``` /// /// However be careful: if you try to access an index which isn't in the `Vec`, /// your software will panic! You cannot do this: /// /// ```should_panic /// let v = vec![0, 2, 4, 6]; /// println!("{}", v[6]); // it will panic! /// ``` /// /// In conclusion: always check if the index you want to get really exists /// before doing it. /// /// # Slicing /// /// A `Vec` can be mutable. Slices, on the other hand, are read-only objects. /// To get a slice, use `&`. Example: /// /// ``` /// fn read_slice(slice: &[usize]) { /// // ... /// } /// /// let v = vec![0, 1]; /// read_slice(&v); /// /// // ... and that's all! /// // you can also do it like this: /// let x : &[usize] = &v; /// ``` /// /// In Rust, it's more common to pass slices as arguments rather than vectors /// when you just want to provide a read access. The same goes for [`String`] and /// [`&str`]. /// /// # Capacity and reallocation /// /// The capacity of a vector is the amount of space allocated for any future /// elements that will be added onto the vector. This is not to be confused with /// the *length* of a vector, which specifies the number of actual elements /// within the vector. If a vector's length exceeds its capacity, its capacity /// will automatically be increased, but its elements will have to be /// reallocated. /// /// For example, a vector with capacity 10 and length 0 would be an empty vector /// with space for 10 more elements. Pushing 10 or fewer elements onto the /// vector will not change its capacity or cause reallocation to occur. However, /// if the vector's length is increased to 11, it will have to reallocate, which /// can be slow. For this reason, it is recommended to use [`Vec::with_capacity`] /// whenever possible to specify how big the vector is expected to get. /// /// # Guarantees /// /// Due to its incredibly fundamental nature, `Vec` makes a lot of guarantees /// about its design. This ensures that it's as low-overhead as possible in /// the general case, and can be correctly manipulated in primitive ways /// by unsafe code. Note that these guarantees refer to an unqualified `Vec<T>`. /// If additional type parameters are added (e.g., to support custom allocators), /// overriding their defaults may change the behavior. /// /// Most fundamentally, `Vec` is and always will be a (pointer, capacity, length) /// triplet. No more, no less. The order of these fields is completely /// unspecified, and you should use the appropriate methods to modify these. /// The pointer will never be null, so this type is null-pointer-optimized. /// /// However, the pointer may not actually point to allocated memory. In particular, /// if you construct a `Vec` with capacity 0 via [`Vec::new`], [`vec![]`][`vec!`], /// [`Vec::with_capacity(0)`][`Vec::with_capacity`], or by calling [`shrink_to_fit`] /// on an empty Vec, it will not allocate memory. Similarly, if you store zero-sized /// types inside a `Vec`, it will not allocate space for them. *Note that in this case /// the `Vec` may not report a [`capacity`] of 0*. `Vec` will allocate if and only /// if [`mem::size_of::<T>`]`() * capacity() > 0`. In general, `Vec`'s allocation /// details are very subtle — if you intend to allocate memory using a `Vec` /// and use it for something else (either to pass to unsafe code, or to build your /// own memory-backed collection), be sure to deallocate this memory by using /// `from_raw_parts` to recover the `Vec` and then dropping it. /// /// If a `Vec` *has* allocated memory, then the memory it points to is on the heap /// (as defined by the allocator Rust is configured to use by default), and its /// pointer points to [`len`] initialized, contiguous elements in order (what /// you would see if you coerced it to a slice), followed by [`capacity`]` - /// `[`len`] logically uninitialized, contiguous elements. /// /// `Vec` will never perform a "small optimization" where elements are actually /// stored on the stack for two reasons: /// /// * It would make it more difficult for unsafe code to correctly manipulate /// a `Vec`. The contents of a `Vec` wouldn't have a stable address if it were /// only moved, and it would be more difficult to determine if a `Vec` had /// actually allocated memory. /// /// * It would penalize the general case, incurring an additional branch /// on every access. /// /// `Vec` will never automatically shrink itself, even if completely empty. This /// ensures no unnecessary allocations or deallocations occur. Emptying a `Vec` /// and then filling it back up to the same [`len`] should incur no calls to /// the allocator. If you wish to free up unused memory, use /// [`shrink_to_fit`][`shrink_to_fit`]. /// /// [`push`] and [`insert`] will never (re)allocate if the reported capacity is /// sufficient. [`push`] and [`insert`] *will* (re)allocate if /// [`len`]` == `[`capacity`]. That is, the reported capacity is completely /// accurate, and can be relied on. It can even be used to manually free the memory /// allocated by a `Vec` if desired. Bulk insertion methods *may* reallocate, even /// when not necessary. /// /// `Vec` does not guarantee any particular growth strategy when reallocating /// when full, nor when [`reserve`] is called. The current strategy is basic /// and it may prove desirable to use a non-constant growth factor. Whatever /// strategy is used will of course guarantee `O(1)` amortized [`push`]. /// /// `vec![x; n]`, `vec![a, b, c, d]`, and /// [`Vec::with_capacity(n)`][`Vec::with_capacity`], will all produce a `Vec` /// with exactly the requested capacity. If [`len`]` == `[`capacity`], /// (as is the case for the [`vec!`] macro), then a `Vec<T>` can be converted to /// and from a [`Box<[T]>`][owned slice] without reallocating or moving the elements. /// /// `Vec` will not specifically overwrite any data that is removed from it, /// but also won't specifically preserve it. Its uninitialized memory is /// scratch space that it may use however it wants. It will generally just do /// whatever is most efficient or otherwise easy to implement. Do not rely on /// removed data to be erased for security purposes. Even if you drop a `Vec`, its /// buffer may simply be reused by another `Vec`. Even if you zero a `Vec`'s memory /// first, that may not actually happen because the optimizer does not consider /// this a side-effect that must be preserved. There is one case which we will /// not break, however: using `unsafe` code to write to the excess capacity, /// and then increasing the length to match, is always valid. /// /// `Vec` does not currently guarantee the order in which elements are dropped. /// The order has changed in the past and may change again. /// /// [`vec!`]: ../../std/macro.vec.html /// [`Index`]: ../../std/ops/trait.Index.html /// [`String`]: ../../std/string/struct.String.html /// [`&str`]: ../../std/primitive.str.html /// [`Vec::with_capacity`]: ../../std/vec/struct.Vec.html#method.with_capacity /// [`Vec::new`]: ../../std/vec/struct.Vec.html#method.new /// [`shrink_to_fit`]: ../../std/vec/struct.Vec.html#method.shrink_to_fit /// [`capacity`]: ../../std/vec/struct.Vec.html#method.capacity /// [`mem::size_of::<T>`]: ../../std/mem/fn.size_of.html /// [`len`]: ../../std/vec/struct.Vec.html#method.len /// [`push`]: ../../std/vec/struct.Vec.html#method.push /// [`insert`]: ../../std/vec/struct.Vec.html#method.insert /// [`reserve`]: ../../std/vec/struct.Vec.html#method.reserve /// [owned slice]: ../../std/boxed/struct.Box.html #[stable(feature = "rust1", since = "1.0.0")] #[cfg_attr(all(not(bootstrap), not(test)), rustc_diagnostic_item = "vec_type")] pub struct Vec<T> { buf: RawVec<T>, len: usize, } //////////////////////////////////////////////////////////////////////////////// // Inherent methods //////////////////////////////////////////////////////////////////////////////// impl<T> Vec<T> { /// Constructs a new, empty `Vec<T>`. /// /// The vector will not allocate until elements are pushed onto it. /// /// # Examples /// /// ``` /// # #![allow(unused_mut)] /// let mut vec: Vec<i32> = Vec::new(); /// ``` #[inline] #[stable(feature = "rust1", since = "1.0.0")] #[cfg_attr(bootstrap, rustc_const_unstable(feature = "const_vec_new"))] pub const fn new() -> Vec<T> { Vec { buf: RawVec::NEW, len: 0, } } /// Constructs 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::with_capacity(10); /// /// // The vector contains no items, even though it has capacity for more /// assert_eq!(vec.len(), 0); /// /// // These are all done without reallocating... /// for i in 0..10 { /// vec.push(i); /// } /// /// // ...but this may make the vector reallocate /// vec.push(11); /// ``` #[inline] #[stable(feature = "rust1", since = "1.0.0")] pub fn with_capacity(capacity: usize) -> Vec<T> { Vec { buf: RawVec::with_capacity(capacity), len: 0, } } /// Creates a `Vec<T>` directly from the raw components of another vector. /// /// # Safety /// /// This is highly unsafe, due to the number of invariants that aren't /// checked: /// /// * `ptr` needs to have been previously allocated via [`String`]/`Vec<T>` /// (at least, it's highly likely to be incorrect if it wasn't). /// * `ptr`'s `T` needs to have the same size and alignment as it was allocated with. /// * `length` needs to be less than or equal to `capacity`. /// * `capacity` needs to be the capacity that the pointer was allocated with. /// /// Violating these may cause problems like corrupting the allocator's /// internal data structures. For example it is **not** safe /// to build a `Vec<u8>` from a pointer to a C `char` array and a `size_t`. /// /// The ownership of `ptr` is effectively transferred to the /// `Vec<T>` which may then deallocate, reallocate or change the /// contents of memory pointed to by the pointer at will. Ensure /// that nothing else uses the pointer after calling this /// function. /// /// [`String`]: ../../std/string/struct.String.html /// /// # Examples /// /// ``` /// use std::ptr; /// use std::mem; /// /// fn main() { /// let mut v = vec![1, 2, 3]; /// /// // Pull out the various important pieces of information about `v` /// let p = v.as_mut_ptr(); /// let len = v.len(); /// let cap = v.capacity(); /// /// unsafe { /// // Cast `v` into the void: no destructor run, so we are in /// // complete control of the allocation to which `p` points. /// mem::forget(v); /// /// // Overwrite memory with 4, 5, 6 /// for i in 0..len as isize { /// ptr::write(p.offset(i), 4 + i); /// } /// /// // Put everything back together into a Vec /// let rebuilt = Vec::from_raw_parts(p, len, cap); /// assert_eq!(rebuilt, [4, 5, 6]); /// } /// } /// ``` #[stable(feature = "rust1", since = "1.0.0")] pub unsafe fn from_raw_parts(ptr: *mut T, length: usize, capacity: usize) -> Vec<T> { Vec { buf: RawVec::from_raw_parts(ptr, capacity), len: length, } } /// Returns the number of elements the vector can hold without /// reallocating. /// /// # Examples /// /// ``` /// let vec: Vec<i32> = Vec::with_capacity(10); /// assert_eq!(vec.capacity(), 10); /// ``` #[inline] #[stable(feature = "rust1", since = "1.0.0")] pub fn capacity(&self) -> usize { self.buf.capacity() } /// Reserves capacity for at least `additional` more elements to be inserted /// in the given `Vec<T>`. The collection may reserve more space to avoid /// frequent reallocations. After calling `reserve`, capacity will be /// greater than or equal to `self.len() + additional`. Does nothing if /// capacity is already sufficient. /// /// # Panics /// /// Panics if the new capacity overflows `usize`. /// /// # Examples /// /// ``` /// let mut vec = vec![1]; /// vec.reserve(10); /// assert!(vec.capacity() >= 11); /// ``` #[stable(feature = "rust1", since = "1.0.0")] pub fn reserve(&mut self, additional: usize) { self.buf.reserve(self.len, additional); } /// Reserves the minimum capacity for exactly `additional` more elements to /// be inserted in the given `Vec<T>`. After calling `reserve_exact`, /// capacity will be greater than or equal to `self.len() + additional`. /// Does nothing if the capacity is already sufficient. /// /// Note that the allocator may give the collection more space than it /// requests. Therefore, capacity can not be relied upon to be precisely /// minimal. Prefer `reserve` if future insertions are expected. /// /// # Panics /// /// Panics if the new capacity overflows `usize`. /// /// # Examples /// /// ``` /// let mut vec = vec![1]; /// vec.reserve_exact(10); /// assert!(vec.capacity() >= 11); /// ``` #[stable(feature = "rust1", since = "1.0.0")] pub fn reserve_exact(&mut self, additional: usize) { self.buf.reserve_exact(self.len, additional); } /// Tries to reserve capacity for at least `additional` more elements to be inserted /// in the given `Vec<T>`. The collection may reserve more space to avoid /// frequent reallocations. After calling `reserve`, capacity will be /// greater than or equal to `self.len() + additional`. Does nothing if /// capacity is already sufficient. /// /// # Errors /// /// If the capacity overflows, or the allocator reports a failure, then an error /// is returned. /// /// # Examples /// /// ``` /// #![feature(try_reserve)] /// use std::collections::TryReserveError; /// /// fn process_data(data: &[u32]) -> Result<Vec<u32>, TryReserveError> { /// let mut output = Vec::new(); /// /// // Pre-reserve the memory, exiting if we can't /// output.try_reserve(data.len())?; /// /// // Now we know this can't OOM in the middle of our complex work /// output.extend(data.iter().map(|&val| { /// val * 2 + 5 // very complicated /// })); /// /// Ok(output) /// } /// # process_data(&[1, 2, 3]).expect("why is the test harness OOMing on 12 bytes?"); /// ``` #[unstable(feature = "try_reserve", reason = "new API", issue="48043")] pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> { self.buf.try_reserve(self.len, additional) } /// Tries to reserves the minimum capacity for exactly `additional` more elements to /// be inserted in the given `Vec<T>`. After calling `reserve_exact`, /// capacity will be greater than or equal to `self.len() + additional`. /// Does nothing if the capacity is already sufficient. /// /// Note that the allocator may give the collection more space than it /// requests. Therefore, capacity can not be relied upon to be precisely /// minimal. Prefer `reserve` if future insertions are expected. /// /// # Errors /// /// If the capacity overflows, or the allocator reports a failure, then an error /// is returned. /// /// # Examples /// /// ``` /// #![feature(try_reserve)] /// use std::collections::TryReserveError; /// /// fn process_data(data: &[u32]) -> Result<Vec<u32>, TryReserveError> { /// let mut output = Vec::new(); /// /// // Pre-reserve the memory, exiting if we can't /// output.try_reserve(data.len())?; /// /// // Now we know this can't OOM in the middle of our complex work /// output.extend(data.iter().map(|&val| { /// val * 2 + 5 // very complicated /// })); /// /// Ok(output) /// } /// # process_data(&[1, 2, 3]).expect("why is the test harness OOMing on 12 bytes?"); /// ``` #[unstable(feature = "try_reserve", reason = "new API", issue="48043")] pub fn try_reserve_exact(&mut self, additional: usize) -> Result<(), TryReserveError> { self.buf.try_reserve_exact(self.len, additional) } /// Shrinks 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].iter().cloned()); /// assert_eq!(vec.capacity(), 10); /// vec.shrink_to_fit(); /// assert!(vec.capacity() >= 3); /// ``` #[stable(feature = "rust1", since = "1.0.0")] pub fn shrink_to_fit(&mut self) { if self.capacity() != self.len { self.buf.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 /// and the supplied value. /// /// Panics if the current capacity is smaller than the supplied /// minimum capacity. /// /// # Examples /// /// ``` /// #![feature(shrink_to)] /// let mut vec = Vec::with_capacity(10); /// vec.extend([1, 2, 3].iter().cloned()); /// assert_eq!(vec.capacity(), 10); /// vec.shrink_to(4); /// assert!(vec.capacity() >= 4); /// vec.shrink_to(0); /// assert!(vec.capacity() >= 3); /// ``` #[unstable(feature = "shrink_to", reason = "new API", issue="56431")] pub fn shrink_to(&mut self, min_capacity: usize) { self.buf.shrink_to_fit(cmp::max(self.len, min_capacity)); } /// Converts the vector into [`Box<[T]>`][owned slice]. /// /// Note that this will drop any excess capacity. /// /// [owned slice]: ../../std/boxed/struct.Box.html /// /// # Examples /// /// ``` /// let v = vec![1, 2, 3]; /// /// let slice = v.into_boxed_slice(); /// ``` /// /// Any excess capacity is removed: /// /// ``` /// let mut vec = Vec::with_capacity(10); /// vec.extend([1, 2, 3].iter().cloned()); /// /// assert_eq!(vec.capacity(), 10); /// let slice = vec.into_boxed_slice(); /// assert_eq!(slice.into_vec().capacity(), 3); /// ``` #[stable(feature = "rust1", since = "1.0.0")] pub fn into_boxed_slice(mut self) -> Box<[T]> { unsafe { self.shrink_to_fit(); let buf = ptr::read(&self.buf); mem::forget(self); buf.into_box() } } /// Shortens the vector, keeping the first `len` elements and dropping /// the rest. /// /// If `len` is greater than the vector's current length, this has no /// effect. /// /// The [`drain`] method can emulate `truncate`, but causes the excess /// elements to be returned instead of dropped. /// /// Note that this method has no effect on the allocated capacity /// of the vector. /// /// # Examples /// /// Truncating a five element vector to two elements: /// /// ``` /// let mut vec = vec![1, 2, 3, 4, 5]; /// vec.truncate(2); /// assert_eq!(vec, [1, 2]); /// ``` /// /// No truncation occurs when `len` is greater than the vector's current /// length: /// /// ``` /// let mut vec = vec![1, 2, 3]; /// vec.truncate(8); /// assert_eq!(vec, [1, 2, 3]); /// ``` /// /// Truncating when `len == 0` is equivalent to calling the [`clear`] /// method. /// /// ``` /// let mut vec = vec![1, 2, 3]; /// vec.truncate(0); /// assert_eq!(vec, []); /// ``` /// /// [`clear`]: #method.clear /// [`drain`]: #method.drain #[stable(feature = "rust1", since = "1.0.0")] pub fn truncate(&mut self, len: usize) { if mem::needs_drop::<T>() { let current_len = self.len; unsafe { let mut ptr = self.as_mut_ptr().add(self.len); // Set the final length at the end, keeping in mind that // dropping an element might panic. Works around a missed // optimization, as seen in the following issue: // https://github.com/rust-lang/rust/issues/51802 let mut local_len = SetLenOnDrop::new(&mut self.len); // drop any extra elements for _ in len..current_len { local_len.decrement_len(1); ptr = ptr.offset(-1); ptr::drop_in_place(ptr); } } } else if len <= self.len { self.len = len; } } /// Extracts a slice containing the entire vector. /// /// Equivalent to `&s[..]`. /// /// # Examples /// /// ``` /// use std::io::{self, Write}; /// let buffer = vec![1, 2, 3, 5, 8]; /// io::sink().write(buffer.as_slice()).unwrap(); /// ``` #[inline] #[stable(feature = "vec_as_slice", since = "1.7.0")] pub fn as_slice(&self) -> &[T] { self } /// Extracts a mutable slice of the entire vector. /// /// Equivalent to `&mut s[..]`. /// /// # Examples /// /// ``` /// use std::io::{self, Read}; /// let mut buffer = vec![0; 3]; /// io::repeat(0b101).read_exact(buffer.as_mut_slice()).unwrap(); /// ``` #[inline] #[stable(feature = "vec_as_slice", since = "1.7.0")] pub fn as_mut_slice(&mut self) -> &mut [T] { self } /// Returns a raw pointer to the vector's buffer. /// /// The caller must ensure that the vector outlives the pointer this /// function returns, or else it will end up pointing to garbage. /// Modifying the vector may cause its buffer to be reallocated, /// which would also make any pointers to it invalid. /// /// The caller must also ensure that the memory the pointer (non-transitively) points to /// is never written to (except inside an `UnsafeCell`) using this pointer or any pointer /// derived from it. If you need to mutate the contents of the slice, use [`as_mut_ptr`]. /// /// # Examples /// /// ``` /// let x = vec![1, 2, 4]; /// let x_ptr = x.as_ptr(); /// /// unsafe { /// for i in 0..x.len() { /// assert_eq!(*x_ptr.add(i), 1 << i); /// } /// } /// ``` /// /// [`as_mut_ptr`]: #method.as_mut_ptr #[stable(feature = "vec_as_ptr", since = "1.37.0")] #[inline] pub fn as_ptr(&self) -> *const T { // We shadow the slice method of the same name to avoid going through // `deref`, which creates an intermediate reference. let ptr = self.buf.ptr(); unsafe { assume(!ptr.is_null()); } ptr } /// Returns an unsafe mutable pointer to the vector's buffer. /// /// The caller must ensure that the vector outlives the pointer this /// function returns, or else it will end up pointing to garbage. /// Modifying the vector may cause its buffer to be reallocated, /// which would also make any pointers to it invalid. /// /// # Examples /// /// ``` /// // Allocate vector big enough for 4 elements. /// let size = 4; /// let mut x: Vec<i32> = Vec::with_capacity(size); /// let x_ptr = x.as_mut_ptr(); /// /// // Initialize elements via raw pointer writes, then set length. /// unsafe { /// for i in 0..size { /// *x_ptr.add(i) = i as i32; /// } /// x.set_len(size); /// } /// assert_eq!(&*x, &[0,1,2,3]); /// ``` #[stable(feature = "vec_as_ptr", since = "1.37.0")] #[inline] pub fn as_mut_ptr(&mut self) -> *mut T { // We shadow the slice method of the same name to avoid going through // `deref_mut`, which creates an intermediate reference. let ptr = self.buf.ptr(); unsafe { assume(!ptr.is_null()); } ptr } /// Forces the length of the vector to `new_len`. /// /// This is a low-level operation that maintains none of the normal /// invariants of the type. Normally changing the length of a vector /// is done using one of the safe operations instead, such as /// [`truncate`], [`resize`], [`extend`], or [`clear`]. /// /// [`truncate`]: #method.truncate /// [`resize`]: #method.resize /// [`extend`]: #method.extend-1 /// [`clear`]: #method.clear /// /// # Safety /// /// - `new_len` must be less than or equal to [`capacity()`]. /// - The elements at `old_len..new_len` must be initialized. /// /// [`capacity()`]: #method.capacity /// /// # Examples /// /// This method can be useful for situations in which the vector /// is serving as a buffer for other code, particularly over FFI: /// /// ```no_run /// # #![allow(dead_code)] /// # // This is just a minimal skeleton for the doc example; /// # // don't use this as a starting point for a real library. /// # pub struct StreamWrapper { strm: *mut std::ffi::c_void } /// # const Z_OK: i32 = 0; /// # extern "C" { /// # fn deflateGetDictionary( /// # strm: *mut std::ffi::c_void, /// # dictionary: *mut u8, /// # dictLength: *mut usize, /// # ) -> i32; /// # } /// # impl StreamWrapper { /// pub fn get_dictionary(&self) -> Option<Vec<u8>> { /// // Per the FFI method's docs, "32768 bytes is always enough". /// let mut dict = Vec::with_capacity(32_768); /// let mut dict_length = 0; /// // SAFETY: When `deflateGetDictionary` returns `Z_OK`, it holds that: /// // 1. `dict_length` elements were initialized. /// // 2. `dict_length` <= the capacity (32_768) /// // which makes `set_len` safe to call. /// unsafe { /// // Make the FFI call... /// let r = deflateGetDictionary(self.strm, dict.as_mut_ptr(), &mut dict_length); /// if r == Z_OK { /// // ...and update the length to what was initialized. /// dict.set_len(dict_length); /// Some(dict) /// } else { /// None /// } /// } /// } /// # } /// ``` /// /// While the following example is sound, there is a memory leak since /// the inner vectors were not freed prior to the `set_len` call: /// /// ``` /// let mut vec = vec![vec![1, 0, 0], /// vec![0, 1, 0], /// vec![0, 0, 1]]; /// // SAFETY: /// // 1. `old_len..0` is empty so no elements need to be initialized. /// // 2. `0 <= capacity` always holds whatever `capacity` is. /// unsafe { /// vec.set_len(0); /// } /// ``` /// /// Normally, here, one would use [`clear`] instead to correctly drop /// the contents and thus not leak memory. #[inline] #[stable(feature = "rust1", since = "1.0.0")] pub unsafe fn set_len(&mut self, new_len: usize) { debug_assert!(new_len <= self.capacity()); self.len = new_len; } /// Removes an element from the vector and returns it. /// /// The removed element is replaced by the last element of the vector. /// /// This does not preserve ordering, but is O(1). /// /// # Panics /// /// Panics if `index` is out of bounds. /// /// # Examples /// /// ``` /// let mut v = vec!["foo", "bar", "baz", "qux"]; /// /// assert_eq!(v.swap_remove(1), "bar"); /// assert_eq!(v, ["foo", "qux", "baz"]); /// /// assert_eq!(v.swap_remove(0), "foo"); /// assert_eq!(v, ["baz", "qux"]); /// ``` #[inline] #[stable(feature = "rust1", since = "1.0.0")] pub fn swap_remove(&mut self, index: usize) -> T { unsafe { // We replace self[index] with the last element. Note that if the // bounds check on hole succeeds there must be a last element (which // can be self[index] itself). let hole: *mut T = &mut self[index]; let last = ptr::read(self.get_unchecked(self.len - 1)); self.len -= 1; ptr::replace(hole, last) } } /// Inserts an element at position `index` within the vector, shifting all /// elements after it to the right. /// /// # Panics /// /// Panics if `index > len`. /// /// # Examples /// /// ``` /// let mut vec = vec![1, 2, 3]; /// vec.insert(1, 4); /// assert_eq!(vec, [1, 4, 2, 3]); /// vec.insert(4, 5); /// assert_eq!(vec, [1, 4, 2, 3, 5]); /// ``` #[stable(feature = "rust1", since = "1.0.0")] pub fn insert(&mut self, index: usize, element: T) { let len = self.len(); assert!(index <= len); // space for the new element if len == self.buf.capacity() { self.reserve(1); } unsafe { // infallible // The spot to put the new value { let p = self.as_mut_ptr().add(index); // Shift everything over to make space. (Duplicating the // `index`th element into two consecutive places.) ptr::copy(p, p.offset(1), len - index); // Write it in, overwriting the first copy of the `index`th // element. ptr::write(p, element); } self.set_len(len + 1); } } /// Removes and returns the element at position `index` within the vector, /// shifting all elements after it to the left. /// /// # Panics /// /// Panics if `index` is out of bounds. /// /// # Examples /// /// ``` /// let mut v = vec![1, 2, 3]; /// assert_eq!(v.remove(1), 2); /// assert_eq!(v, [1, 3]); /// ``` #[stable(feature = "rust1", since = "1.0.0")] pub fn remove(&mut self, index: usize) -> T { let len = self.len(); assert!(index < len); unsafe { // infallible let ret; { // the place we are taking from. let ptr = self.as_mut_ptr().add(index); // copy it out, unsafely having a copy of the value on // the stack and in the vector at the same time. ret = ptr::read(ptr); // Shift everything down to fill in that spot. ptr::copy(ptr.offset(1), ptr, len - index - 1); } self.set_len(len - 1); ret } } /// Retains only the elements specified by the predicate. /// /// In other words, remove all elements `e` such that `f(&e)` returns `false`. /// This method operates in place, visiting each element exactly once in the /// original order, and preserves the order of the retained elements. /// /// # Examples /// /// ``` /// let mut vec = vec![1, 2, 3, 4]; /// vec.retain(|&x| x%2 == 0); /// assert_eq!(vec, [2, 4]); /// ``` /// /// The exact order may be useful for tracking external state, like an index. /// /// ``` /// let mut vec = vec![1, 2, 3, 4, 5]; /// let keep = [false, true, true, false, true]; /// let mut i = 0; /// vec.retain(|_| (keep[i], i += 1).0); /// assert_eq!(vec, [2, 3, 5]); /// ``` #[stable(feature = "rust1", since = "1.0.0")] pub fn retain<F>(&mut self, mut f: F) where F: FnMut(&T) -> bool { self.drain_filter(|x| !f(x)); } /// Removes all but the first of consecutive elements in the vector that resolve to the same /// key. /// /// If the vector is sorted, this removes all duplicates. /// /// # Examples /// /// ``` /// let mut vec = vec![10, 20, 21, 30, 20]; /// /// vec.dedup_by_key(|i| *i / 10); /// /// assert_eq!(vec, [10, 20, 30, 20]); /// ``` #[stable(feature = "dedup_by", since = "1.16.0")] #[inline] pub fn dedup_by_key<F, K>(&mut self, mut key: F) where F: FnMut(&mut T) -> K, K: PartialEq { self.dedup_by(|a, b| key(a) == key(b)) } /// Removes all but the first of consecutive elements in the vector satisfying a given equality /// relation. /// /// The `same_bucket` function is passed references to two elements from the vector and /// must determine if the elements compare equal. The elements are passed in opposite order /// from their order in the slice, so if `same_bucket(a, b)` returns `true`, `a` is removed. /// /// If the vector is sorted, this removes all duplicates. /// /// # Examples /// /// ``` /// let mut vec = vec!["foo", "bar", "Bar", "baz", "bar"]; /// /// vec.dedup_by(|a, b| a.eq_ignore_ascii_case(b)); /// /// assert_eq!(vec, ["foo", "bar", "baz", "bar"]); /// ``` #[stable(feature = "dedup_by", since = "1.16.0")] pub fn dedup_by<F>(&mut self, same_bucket: F) where F: FnMut(&mut T, &mut T) -> bool { let len = { let (dedup, _) = self.as_mut_slice().partition_dedup_by(same_bucket); dedup.len() }; self.truncate(len); } /// Appends an element to the back of a collection. /// /// # Panics /// /// Panics if the number of elements in the vector overflows a `usize`. /// /// # Examples /// /// ``` /// let mut vec = vec![1, 2]; /// vec.push(3); /// assert_eq!(vec, [1, 2, 3]); /// ``` #[inline] #[stable(feature = "rust1", since = "1.0.0")] pub fn push(&mut self, value: T) { // This will panic or abort if we would allocate > isize::MAX bytes // or if the length increment would overflow for zero-sized types. if self.len == self.buf.capacity() { self.reserve(1); } unsafe { let end = self.as_mut_ptr().add(self.len); ptr::write(end, value); self.len += 1; } } /// Removes the last element from a vector and returns it, or [`None`] if it /// is empty. /// /// [`None`]: ../../std/option/enum.Option.html#variant.None /// /// # Examples /// /// ``` /// let mut vec = vec![1, 2, 3]; /// assert_eq!(vec.pop(), Some(3)); /// assert_eq!(vec, [1, 2]); /// ``` #[inline] #[stable(feature = "rust1", since = "1.0.0")] pub fn pop(&mut self) -> Option<T> { if self.len == 0 { None } else { unsafe { self.len -= 1; Some(ptr::read(self.get_unchecked(self.len()))) } } } /// Moves all the elements of `other` into `Self`, leaving `other` empty. /// /// # Panics /// /// Panics if the number of elements in the vector overflows a `usize`. /// /// # Examples /// /// ``` /// let mut vec = vec![1, 2, 3]; /// let mut vec2 = vec![4, 5, 6]; /// vec.append(&mut vec2); /// assert_eq!(vec, [1, 2, 3, 4, 5, 6]); /// assert_eq!(vec2, []); /// ``` #[inline] #[stable(feature = "append", since = "1.4.0")] pub fn append(&mut self, other: &mut Self) { unsafe { self.append_elements(other.as_slice() as _); other.set_len(0); } } /// Appends elements to `Self` from other buffer. #[inline] unsafe fn append_elements(&mut self, other: *const [T]) { let count = (*other).len(); self.reserve(count); let len = self.len(); ptr::copy_nonoverlapping(other as *const T, self.as_mut_ptr().add(len), count); self.len += count; } /// Creates a draining iterator that removes the specified range in the vector /// and yields the removed items. /// /// Note 1: The element range is removed even if the iterator is only /// partially consumed or not consumed at all. /// /// Note 2: It is unspecified how many elements are removed from the vector /// if the `Drain` value is leaked. /// /// # Panics /// /// Panics if the starting point is greater than the end point or if /// the end point is greater than the length of the vector. /// /// # Examples /// /// ``` /// let mut v = vec![1, 2, 3]; /// let u: Vec<_> = v.drain(1..).collect(); /// assert_eq!(v, &[1]); /// assert_eq!(u, &[2, 3]); /// /// // A full range clears the vector /// v.drain(..); /// assert_eq!(v, &[]); /// ``` #[stable(feature = "drain", since = "1.6.0")] pub fn drain<R>(&mut self, range: R) -> Drain<'_, T> where R: RangeBounds<usize> { // Memory safety // // When the Drain is first created, it shortens the length of // the source vector to make sure no uninitialized or moved-from elements // are accessible at all if the Drain's destructor never gets to run. // // Drain will ptr::read out the values to remove. // When finished, remaining tail of the vec is copied back to cover // the hole, and the vector length is restored to the new length. // let len = self.len(); let start = match range.start_bound() { Included(&n) => n, Excluded(&n) => n + 1, Unbounded => 0, }; let end = match range.end_bound() { Included(&n) => n + 1, Excluded(&n) => n, Unbounded => len, }; assert!(start <= end); assert!(end <= len); unsafe { // set self.vec length's to start, to be safe in case Drain is leaked self.set_len(start); // Use the borrow in the IterMut to indicate borrowing behavior of the // whole Drain iterator (like &mut T). let range_slice = slice::from_raw_parts_mut(self.as_mut_ptr().add(start), end - start); Drain { tail_start: end, tail_len: len - end, iter: range_slice.iter(), vec: NonNull::from(self), } } } /// Clears the vector, removing all values. /// /// Note that this method has no effect on the allocated capacity /// of the vector. /// /// # Examples /// /// ``` /// let mut v = vec![1, 2, 3]; /// /// v.clear(); /// /// assert!(v.is_empty()); /// ``` #[inline] #[stable(feature = "rust1", since = "1.0.0")] pub fn clear(&mut self) { self.truncate(0) } /// Returns the number of elements in the vector, also referred to /// as its 'length'. /// /// # Examples /// /// ``` /// let a = vec![1, 2, 3]; /// assert_eq!(a.len(), 3); /// ``` #[inline] #[stable(feature = "rust1", since = "1.0.0")] pub fn len(&self) -> usize { self.len } /// Returns `true` if the vector contains no elements. /// /// # Examples /// /// ``` /// let mut v = Vec::new(); /// assert!(v.is_empty()); /// /// v.push(1); /// assert!(!v.is_empty()); /// ``` #[stable(feature = "rust1", since = "1.0.0")] pub fn is_empty(&self) -> bool { self.len() == 0 } /// Splits the collection into two at the given index. /// /// Returns a newly allocated `Self`. `self` contains elements `[0, at)`, /// and the returned `Self` contains elements `[at, len)`. /// /// Note that the capacity of `self` does not change. /// /// # Panics /// /// Panics if `at > len`. /// /// # Examples /// /// ``` /// let mut vec = vec![1,2,3]; /// let vec2 = vec.split_off(1); /// assert_eq!(vec, [1]); /// assert_eq!(vec2, [2, 3]); /// ``` #[inline] #[stable(feature = "split_off", since = "1.4.0")] pub fn split_off(&mut self, at: usize) -> Self { assert!(at <= self.len(), "`at` out of bounds"); let other_len = self.len - at; let mut other = Vec::with_capacity(other_len); // Unsafely `set_len` and copy items to `other`. unsafe { self.set_len(at); other.set_len(other_len); ptr::copy_nonoverlapping(self.as_ptr().add(at), other.as_mut_ptr(), other.len()); } other } /// Resizes 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 the result of /// calling the closure `f`. The return values from `f` will end up /// in the `Vec` in the order they have been generated. /// /// If `new_len` is less than `len`, the `Vec` is simply truncated. /// /// This method uses a closure to create new values on every push. If /// you'd rather [`Clone`] a given value, use [`resize`]. If you want /// to use the [`Default`] trait to generate values, you can pass /// [`Default::default()`] as the second argument. /// /// # Examples /// /// ``` /// let mut vec = vec![1, 2, 3]; /// vec.resize_with(5, Default::default); /// assert_eq!(vec, [1, 2, 3, 0, 0]); /// /// let mut vec = vec![]; /// let mut p = 1; /// vec.resize_with(4, || { p *= 2; p }); /// assert_eq!(vec, [2, 4, 8, 16]); /// ``` /// /// [`resize`]: #method.resize /// [`Clone`]: ../../std/clone/trait.Clone.html #[stable(feature = "vec_resize_with", since = "1.33.0")] pub fn resize_with<F>(&mut self, new_len: usize, f: F) where F: FnMut() -> T { let len = self.len(); if new_len > len { self.extend_with(new_len - len, ExtendFunc(f)); } else { self.truncate(new_len); } } /// Consumes and leaks the `Vec`, returning a mutable reference to the contents, /// `&'a mut [T]`. Note that the type `T` must outlive the chosen lifetime /// `'a`. If the type has only static references, or none at all, then this /// may be chosen to be `'static`. /// /// This function is similar to the `leak` function on `Box`. /// /// This function is mainly useful for data that lives for the remainder of /// the program's life. Dropping the returned reference will cause a memory /// leak. /// /// # Examples /// /// Simple usage: /// /// ``` /// #![feature(vec_leak)] /// /// fn main() { /// let x = vec![1, 2, 3]; /// let static_ref: &'static mut [usize] = Vec::leak(x); /// static_ref[0] += 1; /// assert_eq!(static_ref, &[2, 2, 3]); /// } /// ``` #[unstable(feature = "vec_leak", issue = "62195")] #[inline] pub fn leak<'a>(vec: Vec<T>) -> &'a mut [T] where T: 'a // Technically not needed, but kept to be explicit. { Box::leak(vec.into_boxed_slice()) } } impl<T: Clone> Vec<T> { /// Resizes 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 [`Clone`] to be able clone the passed value. If /// you need more flexibility (or want to rely on [`Default`] instead of /// [`Clone`]), use [`resize_with`]. /// /// # Examples /// /// ``` /// let mut vec = vec!["hello"]; /// vec.resize(3, "world"); /// assert_eq!(vec, ["hello", "world", "world"]); /// /// let mut vec = vec![1, 2, 3, 4]; /// vec.resize(2, 0); /// assert_eq!(vec, [1, 2]); /// ``` /// /// [`Clone`]: ../../std/clone/trait.Clone.html /// [`Default`]: ../../std/default/trait.Default.html /// [`resize_with`]: #method.resize_with #[stable(feature = "vec_resize", since = "1.5.0")] pub fn resize(&mut self, new_len: usize, value: T) { let len = self.len(); if new_len > len { self.extend_with(new_len - len, ExtendElement(value)) } else { self.truncate(new_len); } } /// Clones and appends 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` vector 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.extend_from_slice(&[2, 3, 4]); /// assert_eq!(vec, [1, 2, 3, 4]); /// ``` /// /// [`extend`]: #method.extend #[stable(feature = "vec_extend_from_slice", since = "1.6.0")] pub fn extend_from_slice(&mut self, other: &[T]) { self.spec_extend(other.iter()) } } impl<T: Default> Vec<T> { /// Resizes 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 [`Default::default()`]. /// If `new_len` is less than `len`, the `Vec` is simply truncated. /// /// This method uses [`Default`] to create new values on every push. If /// you'd rather [`Clone`] a given value, use [`resize`]. /// /// # Examples /// /// ``` /// # #![allow(deprecated)] /// #![feature(vec_resize_default)] /// /// let mut vec = vec![1, 2, 3]; /// vec.resize_default(5); /// assert_eq!(vec, [1, 2, 3, 0, 0]); /// /// let mut vec = vec![1, 2, 3, 4]; /// vec.resize_default(2); /// assert_eq!(vec, [1, 2]); /// ``` /// /// [`resize`]: #method.resize /// [`Default::default()`]: ../../std/default/trait.Default.html#tymethod.default /// [`Default`]: ../../std/default/trait.Default.html /// [`Clone`]: ../../std/clone/trait.Clone.html #[unstable(feature = "vec_resize_default", issue = "41758")] #[rustc_deprecated(reason = "This is moving towards being removed in favor \ of `.resize_with(Default::default)`. If you disagree, please comment \ in the tracking issue.", since = "1.33.0")] pub fn resize_default(&mut self, new_len: usize) { let len = self.len(); if new_len > len { self.extend_with(new_len - len, ExtendDefault); } else { self.truncate(new_len); } } } // This code generalises `extend_with_{element,default}`. trait ExtendWith<T> { fn next(&mut self) -> T; fn last(self) -> T; } struct ExtendElement<T>(T); impl<T: Clone> ExtendWith<T> for ExtendElement<T> { fn next(&mut self) -> T { self.0.clone() } fn last(self) -> T { self.0 } } struct ExtendDefault; impl<T: Default> ExtendWith<T> for ExtendDefault { fn next(&mut self) -> T { Default::default() } fn last(self) -> T { Default::default() } } struct ExtendFunc<F>(F); impl<T, F: FnMut() -> T> ExtendWith<T> for ExtendFunc<F> { fn next(&mut self) -> T { (self.0)() } fn last(mut self) -> T { (self.0)() } } impl<T> Vec<T> { /// Extend the vector by `n` values, using the given generator. fn extend_with<E: ExtendWith<T>>(&mut self, n: usize, mut value: E) { self.reserve(n); unsafe { let mut ptr = self.as_mut_ptr().add(self.len()); // Use SetLenOnDrop to work around bug where compiler // may 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 } } } // Set the length of the vec when the `SetLenOnDrop` value goes out of scope. // // The idea is: The length field in SetLenOnDrop is a local variable // that the optimizer will see does not alias with any stores through the Vec's data // pointer. This is a workaround for alias analysis issue #32155 struct SetLenOnDrop<'a> { len: &'a mut usize, local_len: usize, } impl<'a> SetLenOnDrop<'a> { #[inline] fn new(len: &'a mut usize) -> Self { SetLenOnDrop { local_len: *len, len: len } } #[inline] fn increment_len(&mut self, increment: usize) { self.local_len += increment; } #[inline] fn decrement_len(&mut self, decrement: usize) { self.local_len -= decrement; } } impl Drop for SetLenOnDrop<'_> { #[inline] fn drop(&mut self) { *self.len = self.local_len; } } impl<T: PartialEq> Vec<T> { /// Removes consecutive repeated elements in the vector according to the /// [`PartialEq`] trait implementation. /// /// If the vector is sorted, this removes all duplicates. /// /// # Examples /// /// ``` /// let mut vec = vec![1, 2, 2, 3, 2]; /// /// vec.dedup(); /// /// assert_eq!(vec, [1, 2, 3, 2]); /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn dedup(&mut self) { self.dedup_by(|a, b| a == b) } /// Removes the first instance of `item` from the vector if the item exists. /// /// # Examples /// /// ``` /// # #![feature(vec_remove_item)] /// let mut vec = vec![1, 2, 3, 1]; /// /// vec.remove_item(&1); /// /// assert_eq!(vec, vec![2, 3, 1]); /// ``` #[unstable(feature = "vec_remove_item", reason = "recently added", issue = "40062")] pub fn remove_item(&mut self, item: &T) -> Option<T> { let pos = self.iter().position(|x| *x == *item)?; Some(self.remove(pos)) } } //////////////////////////////////////////////////////////////////////////////// // Internal methods and functions //////////////////////////////////////////////////////////////////////////////// #[doc(hidden)] #[stable(feature = "rust1", since = "1.0.0")] pub fn from_elem<T: Clone>(elem: T, n: usize) -> Vec<T> { <T as SpecFromElem>::from_elem(elem, n) } // Specialization trait used for Vec::from_elem trait SpecFromElem: Sized { fn from_elem(elem: Self, n: usize) -> Vec<Self>; } impl<T: Clone> SpecFromElem for T { default fn from_elem(elem: Self, n: usize) -> Vec<Self> { let mut v = Vec::with_capacity(n); v.extend_with(n, ExtendElement(elem)); v } } impl SpecFromElem for u8 { #[inline] fn from_elem(elem: u8, n: usize) -> Vec<u8> { if elem == 0 { return Vec { buf: RawVec::with_capacity_zeroed(n), len: n, } } unsafe { let mut v = Vec::with_capacity(n); ptr::write_bytes(v.as_mut_ptr(), elem, n); v.set_len(n); v } } } impl<T: Clone + IsZero> SpecFromElem for T { #[inline] fn from_elem(elem: T, n: usize) -> Vec<T> { if elem.is_zero() { return Vec { buf: RawVec::with_capacity_zeroed(n), len: n, } } let mut v = Vec::with_capacity(n); v.extend_with(n, ExtendElement(elem)); v } } unsafe trait IsZero { /// Whether this value is zero fn is_zero(&self) -> bool; } macro_rules! impl_is_zero { ($t: ty, $is_zero: expr) => { unsafe impl IsZero for $t { #[inline] fn is_zero(&self) -> bool { $is_zero(*self) } } } } impl_is_zero!(i8, |x| x == 0); impl_is_zero!(i16, |x| x == 0); impl_is_zero!(i32, |x| x == 0); impl_is_zero!(i64, |x| x == 0); impl_is_zero!(i128, |x| x == 0); impl_is_zero!(isize, |x| x == 0); impl_is_zero!(u16, |x| x == 0); impl_is_zero!(u32, |x| x == 0); impl_is_zero!(u64, |x| x == 0); impl_is_zero!(u128, |x| x == 0); impl_is_zero!(usize, |x| x == 0); impl_is_zero!(bool, |x| x == false); impl_is_zero!(char, |x| x == '\0'); impl_is_zero!(f32, |x: f32| x.to_bits() == 0); impl_is_zero!(f64, |x: f64| x.to_bits() == 0); unsafe impl<T: ?Sized> IsZero for *const T { #[inline] fn is_zero(&self) -> bool { (*self).is_null() } } unsafe impl<T: ?Sized> IsZero for *mut T { #[inline] fn is_zero(&self) -> bool { (*self).is_null() } } //////////////////////////////////////////////////////////////////////////////// // Common trait implementations for Vec //////////////////////////////////////////////////////////////////////////////// #[stable(feature = "rust1", since = "1.0.0")] impl<T: Clone> Clone for Vec<T> { #[cfg(not(test))] fn clone(&self) -> Vec<T> { <[T]>::to_vec(&**self) } // HACK(japaric): with cfg(test) the inherent `[T]::to_vec` method, which is // required for this method definition, is not available. Instead use the // `slice::to_vec` function which is only available with cfg(test) // NB see the slice::hack module in slice.rs for more information #[cfg(test)] fn clone(&self) -> Vec<T> { crate::slice::to_vec(&**self) } fn clone_from(&mut self, other: &Vec<T>) { other.as_slice().clone_into(self); } } #[stable(feature = "rust1", since = "1.0.0")] impl<T: Hash> Hash for Vec<T> { #[inline] fn hash<H: hash::Hasher>(&self, state: &mut H) { Hash::hash(&**self, state) } } #[stable(feature = "rust1", since = "1.0.0")] #[rustc_on_unimplemented( message="vector indices are of type `usize` or ranges of `usize`", label="vector indices are of type `usize` or ranges of `usize`", )] impl<T, I: SliceIndex<[T]>> Index<I> for Vec<T> { type Output = I::Output; #[inline] fn index(&self, index: I) -> &Self::Output { Index::index(&**self, index) } } #[stable(feature = "rust1", since = "1.0.0")] #[rustc_on_unimplemented( message="vector indices are of type `usize` or ranges of `usize`", label="vector indices are of type `usize` or ranges of `usize`", )] impl<T, I: SliceIndex<[T]>> IndexMut<I> for Vec<T> { #[inline] fn index_mut(&mut self, index: I) -> &mut Self::Output { IndexMut::index_mut(&mut **self, index) } } #[stable(feature = "rust1", since = "1.0.0")] impl<T> ops::Deref for Vec<T> { type Target = [T]; fn deref(&self) -> &[T] { unsafe { slice::from_raw_parts(self.as_ptr(), self.len) } } } #[stable(feature = "rust1", since = "1.0.0")] impl<T> ops::DerefMut for Vec<T> { fn deref_mut(&mut self) -> &mut [T] { unsafe { slice::from_raw_parts_mut(self.as_mut_ptr(), self.len) } } } #[stable(feature = "rust1", since = "1.0.0")] impl<T> FromIterator<T> for Vec<T> { #[inline] fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Vec<T> { <Self as SpecExtend<T, I::IntoIter>>::from_iter(iter.into_iter()) } } #[stable(feature = "rust1", since = "1.0.0")] impl<T> IntoIterator for Vec<T> { type Item = T; type IntoIter = IntoIter<T>; /// Creates a consuming iterator, that is, one that moves each value out of /// the vector (from start to end). The vector cannot be used after calling /// this. /// /// # Examples /// /// ``` /// let v = vec!["a".to_string(), "b".to_string()]; /// for s in v.into_iter() { /// // s has type String, not &String /// println!("{}", s); /// } /// ``` #[inline] fn into_iter(mut self) -> IntoIter<T> { unsafe { let begin = self.as_mut_ptr(); let end = if mem::size_of::<T>() == 0 { arith_offset(begin as *const i8, self.len() as isize) as *const T } else { begin.add(self.len()) as *const T }; let cap = self.buf.capacity(); mem::forget(self); IntoIter { buf: NonNull::new_unchecked(begin), phantom: PhantomData, cap, ptr: begin, end, } } } } #[stable(feature = "rust1", since = "1.0.0")] impl<'a, T> IntoIterator for &'a Vec<T> { type Item = &'a T; type IntoIter = slice::Iter<'a, T>; fn into_iter(self) -> slice::Iter<'a, T> { self.iter() } } #[stable(feature = "rust1", since = "1.0.0")] impl<'a, T> IntoIterator for &'a mut Vec<T> { type Item = &'a mut T; type IntoIter = slice::IterMut<'a, T>; fn into_iter(self) -> slice::IterMut<'a, T> { self.iter_mut() } } #[stable(feature = "rust1", since = "1.0.0")] impl<T> Extend<T> for Vec<T> { #[inline] fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) { <Self as SpecExtend<T, I::IntoIter>>::spec_extend(self, iter.into_iter()) } } // Specialization trait used for Vec::from_iter and Vec::extend trait SpecExtend<T, I> { fn from_iter(iter: I) -> Self; fn spec_extend(&mut self, iter: I); } impl<T, I> SpecExtend<T, I> for Vec<T> where I: Iterator<Item=T>, { default fn from_iter(mut iterator: I) -> Self { // Unroll the first iteration, as the vector is going to be // expanded on this iteration in every case when the iterable is not // empty, but the loop in extend_desugared() is not going to see the // vector being full in the few subsequent loop iterations. // So we get better branch prediction. let mut vector = match iterator.next() { None => return Vec::new(), Some(element) => { let (lower, _) = iterator.size_hint(); let mut vector = Vec::with_capacity(lower.saturating_add(1)); unsafe { ptr::write(vector.get_unchecked_mut(0), element); vector.set_len(1); } vector } }; <Vec<T> as SpecExtend<T, I>>::spec_extend(&mut vector, iterator); vector } default fn spec_extend(&mut self, iter: I) { self.extend_desugared(iter) } } impl<T, I> SpecExtend<T, I> for Vec<T> where I: TrustedLen<Item=T>, { default fn from_iter(iterator: I) -> Self { let mut vector = Vec::new(); vector.spec_extend(iterator); vector } default fn spec_extend(&mut self, iterator: I) { // This is the case for a TrustedLen iterator. let (low, high) = iterator.size_hint(); if let Some(high_value) = high { debug_assert_eq!(low, high_value, "TrustedLen iterator's size hint is not exact: {:?}", (low, high)); } if let Some(additional) = high { self.reserve(additional); unsafe { let mut ptr = self.as_mut_ptr().add(self.len()); let mut local_len = SetLenOnDrop::new(&mut self.len); iterator.for_each(move |element| { ptr::write(ptr, element); ptr = ptr.offset(1); // NB can't overflow since we would have had to alloc the address space local_len.increment_len(1); }); } } else { self.extend_desugared(iterator) } } } impl<T> SpecExtend<T, IntoIter<T>> for Vec<T> { fn from_iter(iterator: IntoIter<T>) -> Self { // A common case is passing a vector into a function which immediately // re-collects into a vector. We can short circuit this if the IntoIter // has not been advanced at all. if iterator.buf.as_ptr() as *const _ == iterator.ptr { unsafe { let vec = Vec::from_raw_parts(iterator.buf.as_ptr(), iterator.len(), iterator.cap); mem::forget(iterator); vec } } else { let mut vector = Vec::new(); vector.spec_extend(iterator); vector } } fn spec_extend(&mut self, mut iterator: IntoIter<T>) { unsafe { self.append_elements(iterator.as_slice() as _); } iterator.ptr = iterator.end; } } impl<'a, T: 'a, I> SpecExtend<&'a T, I> for Vec<T> where I: Iterator<Item=&'a T>, T: Clone, { default fn from_iter(iterator: I) -> Self { SpecExtend::from_iter(iterator.cloned()) } default fn spec_extend(&mut self, iterator: I) { self.spec_extend(iterator.cloned()) } } impl<'a, T: 'a> SpecExtend<&'a T, slice::Iter<'a, T>> for Vec<T> where T: Copy, { fn spec_extend(&mut self, iterator: slice::Iter<'a, T>) { let slice = iterator.as_slice(); self.reserve(slice.len()); unsafe { let len = self.len(); self.set_len(len + slice.len()); self.get_unchecked_mut(len..).copy_from_slice(slice); } } } impl<T> Vec<T> { fn extend_desugared<I: Iterator<Item = T>>(&mut self, mut iterator: I) { // 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.reserve(lower.saturating_add(1)); } unsafe { ptr::write(self.get_unchecked_mut(len), element); // NB can't overflow since we would have had to alloc the address space self.set_len(len + 1); } } } /// 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`. /// /// The element range is removed even if the iterator is not consumed until the end. /// /// It is unspecified how many elements are removed from the vector /// if the `Splice` value is leaked. /// /// The input iterator `replace_with` is only consumed when the `Splice` value is dropped. /// /// This is optimal if: /// /// * The tail (elements in the vector after `range`) is empty, /// * or `replace_with` yields fewer elements than `range`’s length /// * or the lower bound of its `size_hint()` is exact. /// /// Otherwise, a temporary vector is allocated and the tail is moved twice. /// /// # Panics /// /// Panics if the starting point is greater than the end point or if /// the end point is greater than the length of the vector. /// /// # Examples /// /// ``` /// let mut v = vec![1, 2, 3]; /// let new = [7, 8]; /// let u: Vec<_> = v.splice(..2, new.iter().cloned()).collect(); /// assert_eq!(v, &[7, 8, 3]); /// assert_eq!(u, &[1, 2]); /// ``` #[inline] #[stable(feature = "vec_splice", since = "1.21.0")] pub fn splice<R, I>(&mut self, range: R, replace_with: I) -> Splice<'_, I::IntoIter> where R: RangeBounds<usize>, I: IntoIterator<Item=T> { Splice { drain: self.drain(range), replace_with: replace_with.into_iter(), } } /// Creates an iterator which uses a closure to determine if an element should be removed. /// /// If the closure returns true, then the element is removed and yielded. /// If the closure returns false, the element will remain in the vector and will not be yielded /// by the iterator. /// /// Using this method is equivalent to the following code: /// /// ``` /// # let some_predicate = |x: &mut i32| { *x == 2 || *x == 3 || *x == 6 }; /// # let mut vec = vec![1, 2, 3, 4, 5, 6]; /// let mut i = 0; /// while i != vec.len() { /// if some_predicate(&mut vec[i]) { /// let val = vec.remove(i); /// // your code here /// } else { /// i += 1; /// } /// } /// /// # assert_eq!(vec, vec![1, 4, 5]); /// ``` /// /// But `drain_filter` is easier to use. `drain_filter` is also more efficient, /// because it can backshift the elements of the array in bulk. /// /// Note that `drain_filter` also lets you mutate every element in the filter closure, /// regardless of whether you choose to keep or remove it. /// /// /// # Examples /// /// Splitting an array into evens and odds, reusing the original allocation: /// /// ``` /// #![feature(drain_filter)] /// let mut numbers = vec![1, 2, 3, 4, 5, 6, 8, 9, 11, 13, 14, 15]; /// /// let evens = numbers.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>(); /// let odds = numbers; /// /// assert_eq!(evens, vec![2, 4, 6, 8, 14]); /// assert_eq!(odds, vec![1, 3, 5, 9, 11, 13, 15]); /// ``` #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")] pub fn drain_filter<F>(&mut self, filter: F) -> DrainFilter<'_, T, F> where F: FnMut(&mut T) -> bool, { let old_len = self.len(); // Guard against us getting leaked (leak amplification) unsafe { self.set_len(0); } DrainFilter { vec: self, idx: 0, del: 0, old_len, pred: filter, panic_flag: false, } } } /// Extend implementation that copies elements out of references before pushing them onto the Vec. /// /// This implementation is specialized for slice iterators, where it uses [`copy_from_slice`] to /// append the entire slice at once. /// /// [`copy_from_slice`]: ../../std/primitive.slice.html#method.copy_from_slice #[stable(feature = "extend_ref", since = "1.2.0")] impl<'a, T: 'a + Copy> Extend<&'a T> for Vec<T> { fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) { self.spec_extend(iter.into_iter()) } } macro_rules! __impl_slice_eq1 { ([$($vars:tt)*] $lhs:ty, $rhs:ty, $($constraints:tt)*) => { #[stable(feature = "rust1", since = "1.0.0")] impl<A, B, $($vars)*> PartialEq<$rhs> for $lhs where A: PartialEq<B>, $($constraints)* { #[inline] fn eq(&self, other: &$rhs) -> bool { self[..] == other[..] } #[inline] fn ne(&self, other: &$rhs) -> bool { self[..] != other[..] } } } } __impl_slice_eq1! { [] Vec<A>, Vec<B>, } __impl_slice_eq1! { [] Vec<A>, &[B], } __impl_slice_eq1! { [] Vec<A>, &mut [B], } __impl_slice_eq1! { [] Cow<'_, [A]>, &[B], A: Clone } __impl_slice_eq1! { [] Cow<'_, [A]>, &mut [B], A: Clone } __impl_slice_eq1! { [] Cow<'_, [A]>, Vec<B>, A: Clone } __impl_slice_eq1! { [const N: usize] Vec<A>, [B; N], [B; N]: LengthAtMost32 } __impl_slice_eq1! { [const N: usize] Vec<A>, &[B; N], [B; N]: LengthAtMost32 } // NOTE: some less important impls are omitted to reduce code bloat // FIXME(Centril): Reconsider this? //__impl_slice_eq1! { [const N: usize] Vec<A>, &mut [B; N], [B; N]: LengthAtMost32 } //__impl_slice_eq1! { [const N: usize] Cow<'a, [A]>, [B; N], [B; N]: LengthAtMost32 } //__impl_slice_eq1! { [const N: usize] Cow<'a, [A]>, &[B; N], [B; N]: LengthAtMost32 } //__impl_slice_eq1! { [const N: usize] Cow<'a, [A]>, &mut [B; N], [B; N]: LengthAtMost32 } /// Implements comparison of vectors, lexicographically. #[stable(feature = "rust1", since = "1.0.0")] impl<T: PartialOrd> PartialOrd for Vec<T> { #[inline] fn partial_cmp(&self, other: &Vec<T>) -> Option<Ordering> { PartialOrd::partial_cmp(&**self, &**other) } } #[stable(feature = "rust1", since = "1.0.0")] impl<T: Eq> Eq for Vec<T> {} /// Implements ordering of vectors, lexicographically. #[stable(feature = "rust1", since = "1.0.0")] impl<T: Ord> Ord for Vec<T> { #[inline] fn cmp(&self, other: &Vec<T>) -> Ordering { Ord::cmp(&**self, &**other) } } #[stable(feature = "rust1", since = "1.0.0")] unsafe impl<#[may_dangle] T> Drop for Vec<T> { fn drop(&mut self) { unsafe { // use drop for [T] ptr::drop_in_place(&mut self[..]); } // RawVec handles deallocation } } #[stable(feature = "rust1", since = "1.0.0")] impl<T> Default for Vec<T> { /// Creates an empty `Vec<T>`. fn default() -> Vec<T> { Vec::new() } } #[stable(feature = "rust1", since = "1.0.0")] impl<T: fmt::Debug> fmt::Debug for Vec<T> { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { fmt::Debug::fmt(&**self, f) } } #[stable(feature = "rust1", since = "1.0.0")] impl<T> AsRef<Vec<T>> for Vec<T> { fn as_ref(&self) -> &Vec<T> { self } } #[stable(feature = "vec_as_mut", since = "1.5.0")] impl<T> AsMut<Vec<T>> for Vec<T> { fn as_mut(&mut self) -> &mut Vec<T> { self } } #[stable(feature = "rust1", since = "1.0.0")] impl<T> AsRef<[T]> for Vec<T> { fn as_ref(&self) -> &[T] { self } } #[stable(feature = "vec_as_mut", since = "1.5.0")] impl<T> AsMut<[T]> for Vec<T> { fn as_mut(&mut self) -> &mut [T] { self } } #[stable(feature = "rust1", since = "1.0.0")] impl<T: Clone> From<&[T]> for Vec<T> { #[cfg(not(test))] fn from(s: &[T]) -> Vec<T> { s.to_vec() } #[cfg(test)] fn from(s: &[T]) -> Vec<T> { crate::slice::to_vec(s) } } #[stable(feature = "vec_from_mut", since = "1.19.0")] impl<T: Clone> From<&mut [T]> for Vec<T> { #[cfg(not(test))] fn from(s: &mut [T]) -> Vec<T> { s.to_vec() } #[cfg(test)] fn from(s: &mut [T]) -> Vec<T> { crate::slice::to_vec(s) } } #[stable(feature = "vec_from_cow_slice", since = "1.14.0")] impl<'a, T> From<Cow<'a, [T]>> for Vec<T> where [T]: ToOwned<Owned=Vec<T>> { fn from(s: Cow<'a, [T]>) -> Vec<T> { s.into_owned() } } // note: test pulls in libstd, which causes errors here #[cfg(not(test))] #[stable(feature = "vec_from_box", since = "1.18.0")] impl<T> From<Box<[T]>> for Vec<T> { fn from(s: Box<[T]>) -> Vec<T> { s.into_vec() } } // note: test pulls in libstd, which causes errors here #[cfg(not(test))] #[stable(feature = "box_from_vec", since = "1.20.0")] impl<T> From<Vec<T>> for Box<[T]> { fn from(v: Vec<T>) -> Box<[T]> { v.into_boxed_slice() } } #[stable(feature = "rust1", since = "1.0.0")] impl From<&str> for Vec<u8> { fn from(s: &str) -> Vec<u8> { From::from(s.as_bytes()) } } //////////////////////////////////////////////////////////////////////////////// // Clone-on-write //////////////////////////////////////////////////////////////////////////////// #[stable(feature = "cow_from_vec", since = "1.8.0")] impl<'a, T: Clone> From<&'a [T]> for Cow<'a, [T]> { fn from(s: &'a [T]) -> Cow<'a, [T]> { Cow::Borrowed(s) } } #[stable(feature = "cow_from_vec", since = "1.8.0")] impl<'a, T: Clone> From<Vec<T>> for Cow<'a, [T]> { fn from(v: Vec<T>) -> Cow<'a, [T]> { Cow::Owned(v) } } #[stable(feature = "cow_from_vec_ref", since = "1.28.0")] impl<'a, T: Clone> From<&'a Vec<T>> for Cow<'a, [T]> { fn from(v: &'a Vec<T>) -> Cow<'a, [T]> { Cow::Borrowed(v.as_slice()) } } #[stable(feature = "rust1", since = "1.0.0")] impl<'a, T> FromIterator<T> for Cow<'a, [T]> where T: Clone { fn from_iter<I: IntoIterator<Item = T>>(it: I) -> Cow<'a, [T]> { Cow::Owned(FromIterator::from_iter(it)) } } //////////////////////////////////////////////////////////////////////////////// // Iterators //////////////////////////////////////////////////////////////////////////////// /// An iterator that moves out of a vector. /// /// This `struct` is created by the `into_iter` method on [`Vec`][`Vec`] (provided /// by the [`IntoIterator`] trait). /// /// [`Vec`]: struct.Vec.html /// [`IntoIterator`]: ../../std/iter/trait.IntoIterator.html #[stable(feature = "rust1", since = "1.0.0")] pub struct IntoIter<T> { buf: NonNull<T>, phantom: PhantomData<T>, cap: usize, ptr: *const T, end: *const T, } #[stable(feature = "vec_intoiter_debug", since = "1.13.0")] impl<T: fmt::Debug> fmt::Debug for IntoIter<T> { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f.debug_tuple("IntoIter") .field(&self.as_slice()) .finish() } } impl<T> IntoIter<T> { /// Returns the remaining items of this iterator as a slice. /// /// # Examples /// /// ``` /// let vec = vec!['a', 'b', 'c']; /// let mut into_iter = vec.into_iter(); /// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']); /// let _ = into_iter.next().unwrap(); /// assert_eq!(into_iter.as_slice(), &['b', 'c']); /// ``` #[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")] pub fn as_slice(&self) -> &[T] { unsafe { slice::from_raw_parts(self.ptr, self.len()) } } /// Returns the remaining items of this iterator as a mutable slice. /// /// # Examples /// /// ``` /// let vec = vec!['a', 'b', 'c']; /// let mut into_iter = vec.into_iter(); /// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']); /// into_iter.as_mut_slice()[2] = 'z'; /// assert_eq!(into_iter.next().unwrap(), 'a'); /// assert_eq!(into_iter.next().unwrap(), 'b'); /// assert_eq!(into_iter.next().unwrap(), 'z'); /// ``` #[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")] pub fn as_mut_slice(&mut self) -> &mut [T] { unsafe { slice::from_raw_parts_mut(self.ptr as *mut T, self.len()) } } } #[stable(feature = "rust1", since = "1.0.0")] unsafe impl<T: Send> Send for IntoIter<T> {} #[stable(feature = "rust1", since = "1.0.0")] unsafe impl<T: Sync> Sync for IntoIter<T> {} #[stable(feature = "rust1", since = "1.0.0")] impl<T> Iterator for IntoIter<T> { type Item = T; #[inline] fn next(&mut self) -> Option<T> { unsafe { if self.ptr as *const _ == self.end { None } else { if mem::size_of::<T>() == 0 { // purposefully don't use 'ptr.offset' because for // vectors with 0-size elements this would return the // same pointer. self.ptr = arith_offset(self.ptr as *const i8, 1) as *mut T; // Make up a value of this ZST. Some(mem::zeroed()) } else { let old = self.ptr; self.ptr = self.ptr.offset(1); Some(ptr::read(old)) } } } } #[inline] fn size_hint(&self) -> (usize, Option<usize>) { let exact = if mem::size_of::<T>() == 0 { (self.end as usize).wrapping_sub(self.ptr as usize) } else { unsafe { self.end.offset_from(self.ptr) as usize } }; (exact, Some(exact)) } #[inline] fn count(self) -> usize { self.len() } } #[stable(feature = "rust1", since = "1.0.0")] impl<T> DoubleEndedIterator for IntoIter<T> { #[inline] fn next_back(&mut self) -> Option<T> { unsafe { if self.end == self.ptr { None } else { if mem::size_of::<T>() == 0 { // See above for why 'ptr.offset' isn't used self.end = arith_offset(self.end as *const i8, -1) as *mut T; // Make up a value of this ZST. Some(mem::zeroed()) } else { self.end = self.end.offset(-1); Some(ptr::read(self.end)) } } } } } #[stable(feature = "rust1", since = "1.0.0")] impl<T> ExactSizeIterator for IntoIter<T> { fn is_empty(&self) -> bool { self.ptr == self.end } } #[stable(feature = "fused", since = "1.26.0")] impl<T> FusedIterator for IntoIter<T> {} #[unstable(feature = "trusted_len", issue = "37572")] unsafe impl<T> TrustedLen for IntoIter<T> {} #[stable(feature = "vec_into_iter_clone", since = "1.8.0")] impl<T: Clone> Clone for IntoIter<T> { fn clone(&self) -> IntoIter<T> { self.as_slice().to_owned().into_iter() } } #[stable(feature = "rust1", since = "1.0.0")] unsafe impl<#[may_dangle] T> Drop for IntoIter<T> { fn drop(&mut self) { // destroy the remaining elements for _x in self.by_ref() {} // RawVec handles deallocation let _ = unsafe { RawVec::from_raw_parts(self.buf.as_ptr(), self.cap) }; } } /// A draining iterator for `Vec<T>`. /// /// This `struct` is created by the [`drain`] method on [`Vec`]. /// /// [`drain`]: struct.Vec.html#method.drain /// [`Vec`]: struct.Vec.html #[stable(feature = "drain", since = "1.6.0")] pub struct Drain<'a, T: 'a> { /// Index of tail to preserve tail_start: usize, /// Length of tail tail_len: usize, /// Current remaining range to remove iter: slice::Iter<'a, T>, vec: NonNull<Vec<T>>, } #[stable(feature = "collection_debug", since = "1.17.0")] impl<T: fmt::Debug> fmt::Debug for Drain<'_, T> { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f.debug_tuple("Drain") .field(&self.iter.as_slice()) .finish() } } impl<'a, T> Drain<'a, T> { /// Returns the remaining items of this iterator as a slice. /// /// # Examples /// /// ``` /// # #![feature(vec_drain_as_slice)] /// let mut vec = vec!['a', 'b', 'c']; /// let mut drain = vec.drain(..); /// assert_eq!(drain.as_slice(), &['a', 'b', 'c']); /// let _ = drain.next().unwrap(); /// assert_eq!(drain.as_slice(), &['b', 'c']); /// ``` #[unstable(feature = "vec_drain_as_slice", reason = "recently added", issue = "58957")] pub fn as_slice(&self) -> &[T] { self.iter.as_slice() } } #[stable(feature = "drain", since = "1.6.0")] unsafe impl<T: Sync> Sync for Drain<'_, T> {} #[stable(feature = "drain", since = "1.6.0")] unsafe impl<T: Send> Send for Drain<'_, T> {} #[stable(feature = "drain", since = "1.6.0")] impl<T> Iterator for Drain<'_, T> { type Item = T; #[inline] fn next(&mut self) -> Option<T> { self.iter.next().map(|elt| unsafe { ptr::read(elt as *const _) }) } fn size_hint(&self) -> (usize, Option<usize>) { self.iter.size_hint() } } #[stable(feature = "drain", since = "1.6.0")] impl<T> DoubleEndedIterator for Drain<'_, T> { #[inline] fn next_back(&mut self) -> Option<T> { self.iter.next_back().map(|elt| unsafe { ptr::read(elt as *const _) }) } } #[stable(feature = "drain", since = "1.6.0")] impl<T> Drop for Drain<'_, T> { fn drop(&mut self) { // exhaust self first self.for_each(drop); if self.tail_len > 0 { unsafe { let source_vec = self.vec.as_mut(); // memmove back untouched tail, update to new length let start = source_vec.len(); let tail = self.tail_start; if tail != start { let src = source_vec.as_ptr().add(tail); let dst = source_vec.as_mut_ptr().add(start); ptr::copy(src, dst, self.tail_len); } source_vec.set_len(start + self.tail_len); } } } } #[stable(feature = "drain", since = "1.6.0")] impl<T> ExactSizeIterator for Drain<'_, T> { fn is_empty(&self) -> bool { self.iter.is_empty() } } #[stable(feature = "fused", since = "1.26.0")] impl<T> FusedIterator for Drain<'_, T> {} /// A splicing iterator for `Vec`. /// /// This struct is created by the [`splice()`] method on [`Vec`]. See its /// documentation for more. /// /// [`splice()`]: struct.Vec.html#method.splice /// [`Vec`]: struct.Vec.html #[derive(Debug)] #[stable(feature = "vec_splice", since = "1.21.0")] pub struct Splice<'a, I: Iterator + 'a> { drain: Drain<'a, I::Item>, replace_with: I, } #[stable(feature = "vec_splice", since = "1.21.0")] impl<I: Iterator> Iterator for Splice<'_, I> { type Item = I::Item; fn next(&mut self) -> Option<Self::Item> { self.drain.next() } fn size_hint(&self) -> (usize, Option<usize>) { self.drain.size_hint() } } #[stable(feature = "vec_splice", since = "1.21.0")] impl<I: Iterator> DoubleEndedIterator for Splice<'_, I> { fn next_back(&mut self) -> Option<Self::Item> { self.drain.next_back() } } #[stable(feature = "vec_splice", since = "1.21.0")] impl<I: Iterator> ExactSizeIterator for Splice<'_, I> {} #[stable(feature = "vec_splice", since = "1.21.0")] impl<I: Iterator> Drop for Splice<'_, I> { fn drop(&mut self) { self.drain.by_ref().for_each(drop); unsafe { if self.drain.tail_len == 0 { self.drain.vec.as_mut().extend(self.replace_with.by_ref()); return } // First fill the range left by drain(). if !self.drain.fill(&mut self.replace_with) { return } // There may be more elements. Use the lower bound as an estimate. // FIXME: Is the upper bound a better guess? Or something else? let (lower_bound, _upper_bound) = self.replace_with.size_hint(); if lower_bound > 0 { self.drain.move_tail(lower_bound); if !self.drain.fill(&mut self.replace_with) { return } } // Collect any remaining elements. // This is a zero-length vector which does not allocate if `lower_bound` was exact. let mut collected = self.replace_with.by_ref().collect::<Vec<I::Item>>().into_iter(); // Now we have an exact count. if collected.len() > 0 { self.drain.move_tail(collected.len()); let filled = self.drain.fill(&mut collected); debug_assert!(filled); debug_assert_eq!(collected.len(), 0); } } // Let `Drain::drop` move the tail back if necessary and restore `vec.len`. } } /// Private helper methods for `Splice::drop` impl<T> Drain<'_, T> { /// The range from `self.vec.len` to `self.tail_start` contains elements /// that have been moved out. /// Fill that range as much as possible with new elements from the `replace_with` iterator. /// Returns `true` if we filled the entire range. (`replace_with.next()` didn’t return `None`.) unsafe fn fill<I: Iterator<Item=T>>(&mut self, replace_with: &mut I) -> bool { let vec = self.vec.as_mut(); let range_start = vec.len; let range_end = self.tail_start; let range_slice = slice::from_raw_parts_mut( vec.as_mut_ptr().add(range_start), range_end - range_start); for place in range_slice { if let Some(new_item) = replace_with.next() { ptr::write(place, new_item); vec.len += 1; } else { return false } } true } /// Makes room for inserting more elements before the tail. unsafe fn move_tail(&mut self, extra_capacity: usize) { let vec = self.vec.as_mut(); let used_capacity = self.tail_start + self.tail_len; vec.buf.reserve(used_capacity, extra_capacity); let new_tail_start = self.tail_start + extra_capacity; let src = vec.as_ptr().add(self.tail_start); let dst = vec.as_mut_ptr().add(new_tail_start); ptr::copy(src, dst, self.tail_len); self.tail_start = new_tail_start; } } /// An iterator produced by calling `drain_filter` on Vec. #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")] #[derive(Debug)] pub struct DrainFilter<'a, T, F> where F: FnMut(&mut T) -> bool, { vec: &'a mut Vec<T>, /// The index of the item that will be inspected by the next call to `next`. idx: usize, /// The number of items that have been drained (removed) thus far. del: usize, /// The original length of `vec` prior to draining. old_len: usize, /// The filter test predicate. pred: F, /// A flag that indicates a panic has occured in the filter test prodicate. /// This is used as a hint in the drop implmentation to prevent consumption /// of the remainder of the `DrainFilter`. Any unprocessed items will be /// backshifted in the `vec`, but no further items will be dropped or /// tested by the filter predicate. panic_flag: bool, } #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")] impl<T, F> Iterator for DrainFilter<'_, T, F> where F: FnMut(&mut T) -> bool, { type Item = T; fn next(&mut self) -> Option<T> { unsafe { while self.idx < self.old_len { let i = self.idx; let v = slice::from_raw_parts_mut(self.vec.as_mut_ptr(), self.old_len); self.panic_flag = true; let drained = (self.pred)(&mut v[i]); self.panic_flag = false; // Update the index *after* the predicate is called. If the index // is updated prior and the predicate panics, the element at this // index would be leaked. self.idx += 1; if drained { self.del += 1; return Some(ptr::read(&v[i])); } else if self.del > 0 { let del = self.del; let src: *const T = &v[i]; let dst: *mut T = &mut v[i - del]; ptr::copy_nonoverlapping(src, dst, 1); } } None } } fn size_hint(&self) -> (usize, Option<usize>) { (0, Some(self.old_len - self.idx)) } } #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")] impl<T, F> Drop for DrainFilter<'_, T, F> where F: FnMut(&mut T) -> bool, { fn drop(&mut self) { struct BackshiftOnDrop<'a, 'b, T, F> where F: FnMut(&mut T) -> bool, { drain: &'b mut DrainFilter<'a, T, F>, } impl<'a, 'b, T, F> Drop for BackshiftOnDrop<'a, 'b, T, F> where F: FnMut(&mut T) -> bool { fn drop(&mut self) { unsafe { if self.drain.idx < self.drain.old_len && self.drain.del > 0 { // This is a pretty messed up state, and there isn't really an // obviously right thing to do. We don't want to keep trying // to execute `pred`, so we just backshift all the unprocessed // elements and tell the vec that they still exist. The backshift // is required to prevent a double-drop of the last successfully // drained item prior to a panic in the predicate. let ptr = self.drain.vec.as_mut_ptr(); let src = ptr.add(self.drain.idx); let dst = src.sub(self.drain.del); let tail_len = self.drain.old_len - self.drain.idx; src.copy_to(dst, tail_len); } self.drain.vec.set_len(self.drain.old_len - self.drain.del); } } } let backshift = BackshiftOnDrop { drain: self }; // Attempt to consume any remaining elements if the filter predicate // has not yet panicked. We'll backshift any remaining elements // whether we've already panicked or if the consumption here panics. if !backshift.drain.panic_flag { backshift.drain.for_each(drop); } } }