615 lines
23 KiB
Rust
615 lines
23 KiB
Rust
// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
|
|
// file at the top-level directory of this distribution and at
|
|
// http://rust-lang.org/COPYRIGHT.
|
|
//
|
|
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
|
|
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
|
|
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
|
|
// option. This file may not be copied, modified, or distributed
|
|
// except according to those terms.
|
|
|
|
use core::ptr::Unique;
|
|
use core::mem;
|
|
use core::slice;
|
|
use heap;
|
|
use super::oom;
|
|
use super::boxed::Box;
|
|
use core::ops::Drop;
|
|
use core::cmp;
|
|
|
|
/// A low-level utility for more ergonomically allocating, reallocating, and deallocating
|
|
/// a buffer of memory on the heap without having to worry about all the corner cases
|
|
/// involved. This type is excellent for building your own data structures like Vec and VecDeque.
|
|
/// In particular:
|
|
///
|
|
/// * Produces heap::EMPTY on zero-sized types
|
|
/// * Produces heap::EMPTY on zero-length allocations
|
|
/// * Catches all overflows in capacity computations (promotes them to "capacity overflow" panics)
|
|
/// * Guards against 32-bit systems allocating more than isize::MAX bytes
|
|
/// * Guards against overflowing your length
|
|
/// * Aborts on OOM
|
|
/// * Avoids freeing heap::EMPTY
|
|
/// * Contains a ptr::Unique and thus endows the user with all related benefits
|
|
///
|
|
/// This type does not in anyway inspect the memory that it manages. When dropped it *will*
|
|
/// free its memory, but it *won't* try to Drop its contents. It is up to the user of RawVec
|
|
/// to handle the actual things *stored* inside of a RawVec.
|
|
///
|
|
/// Note that a RawVec always forces its capacity to be usize::MAX for zero-sized types.
|
|
/// This enables you to use capacity growing logic catch the overflows in your length
|
|
/// that might occur with zero-sized types.
|
|
///
|
|
/// However this means that you need to be careful when roundtripping this type
|
|
/// with a `Box<[T]>`: `cap()` won't yield the len. However `with_capacity`,
|
|
/// `shrink_to_fit`, and `from_box` will actually set RawVec's private capacity
|
|
/// field. This allows zero-sized types to not be special-cased by consumers of
|
|
/// this type.
|
|
pub struct RawVec<T> {
|
|
ptr: Unique<T>,
|
|
cap: usize,
|
|
}
|
|
|
|
impl<T> RawVec<T> {
|
|
/// Creates the biggest possible RawVec without allocating. If T has positive
|
|
/// size, then this makes a RawVec with capacity 0. If T has 0 size, then it
|
|
/// it makes a RawVec with capacity `usize::MAX`. Useful for implementing
|
|
/// delayed allocation.
|
|
pub fn new() -> Self {
|
|
unsafe {
|
|
// !0 is usize::MAX. This branch should be stripped at compile time.
|
|
let cap = if mem::size_of::<T>() == 0 { !0 } else { 0 };
|
|
|
|
// heap::EMPTY doubles as "unallocated" and "zero-sized allocation"
|
|
RawVec {
|
|
ptr: Unique::new(heap::EMPTY as *mut T),
|
|
cap: cap,
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Creates a RawVec with exactly the capacity and alignment requirements
|
|
/// for a `[T; cap]`. This is equivalent to calling RawVec::new when `cap` is 0
|
|
/// or T is zero-sized. Note that if `T` is zero-sized this means you will *not*
|
|
/// get a RawVec with the requested capacity!
|
|
///
|
|
/// # Panics
|
|
///
|
|
/// * Panics if the requested capacity exceeds `usize::MAX` bytes.
|
|
/// * Panics on 32-bit platforms if the requested capacity exceeds
|
|
/// `isize::MAX` bytes.
|
|
///
|
|
/// # Aborts
|
|
///
|
|
/// Aborts on OOM
|
|
pub fn with_capacity(cap: usize) -> Self {
|
|
unsafe {
|
|
let elem_size = mem::size_of::<T>();
|
|
|
|
let alloc_size = cap.checked_mul(elem_size).expect("capacity overflow");
|
|
alloc_guard(alloc_size);
|
|
|
|
// handles ZSTs and `cap = 0` alike
|
|
let ptr = if alloc_size == 0 {
|
|
heap::EMPTY as *mut u8
|
|
} else {
|
|
let align = mem::align_of::<T>();
|
|
let ptr = heap::allocate(alloc_size, align);
|
|
if ptr.is_null() {
|
|
oom()
|
|
}
|
|
ptr
|
|
};
|
|
|
|
RawVec {
|
|
ptr: Unique::new(ptr as *mut _),
|
|
cap: cap,
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Reconstitutes a RawVec from a pointer and capacity.
|
|
///
|
|
/// # Undefined Behavior
|
|
///
|
|
/// The ptr must be allocated, and with the given capacity. The
|
|
/// capacity cannot exceed `isize::MAX` (only a concern on 32-bit systems).
|
|
/// If the ptr and capacity come from a RawVec, then this is guaranteed.
|
|
pub unsafe fn from_raw_parts(ptr: *mut T, cap: usize) -> Self {
|
|
RawVec {
|
|
ptr: Unique::new(ptr),
|
|
cap: cap,
|
|
}
|
|
}
|
|
|
|
/// Converts a `Box<[T]>` into a `RawVec<T>`.
|
|
pub fn from_box(mut slice: Box<[T]>) -> Self {
|
|
unsafe {
|
|
let result = RawVec::from_raw_parts(slice.as_mut_ptr(), slice.len());
|
|
mem::forget(slice);
|
|
result
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<T> RawVec<T> {
|
|
/// Gets a raw pointer to the start of the allocation. Note that this is
|
|
/// heap::EMPTY if `cap = 0` or T is zero-sized. In the former case, you must
|
|
/// be careful.
|
|
pub fn ptr(&self) -> *mut T {
|
|
*self.ptr
|
|
}
|
|
|
|
/// Gets the capacity of the allocation.
|
|
///
|
|
/// This will always be `usize::MAX` if `T` is zero-sized.
|
|
#[inline(always)]
|
|
pub fn cap(&self) -> usize {
|
|
if mem::size_of::<T>() == 0 {
|
|
!0
|
|
} else {
|
|
self.cap
|
|
}
|
|
}
|
|
|
|
/// Doubles the size of the type's backing allocation. This is common enough
|
|
/// to want to do that it's easiest to just have a dedicated method. Slightly
|
|
/// more efficient logic can be provided for this than the general case.
|
|
///
|
|
/// This function is ideal for when pushing elements one-at-a-time because
|
|
/// you don't need to incur the costs of the more general computations
|
|
/// reserve needs to do to guard against overflow. You do however need to
|
|
/// manually check if your `len == cap`.
|
|
///
|
|
/// # Panics
|
|
///
|
|
/// * Panics if T is zero-sized on the assumption that you managed to exhaust
|
|
/// all `usize::MAX` slots in your imaginary buffer.
|
|
/// * Panics on 32-bit platforms if the requested capacity exceeds
|
|
/// `isize::MAX` bytes.
|
|
///
|
|
/// # Aborts
|
|
///
|
|
/// Aborts on OOM
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```ignore
|
|
/// struct MyVec<T> {
|
|
/// buf: RawVec<T>,
|
|
/// len: usize,
|
|
/// }
|
|
///
|
|
/// impl<T> MyVec<T> {
|
|
/// pub fn push(&mut self, elem: T) {
|
|
/// if self.len == self.buf.cap() { self.buf.double(); }
|
|
/// // double would have aborted or panicked if the len exceeded
|
|
/// // `isize::MAX` so this is safe to do unchecked now.
|
|
/// unsafe {
|
|
/// ptr::write(self.buf.ptr().offset(self.len as isize), elem);
|
|
/// }
|
|
/// self.len += 1;
|
|
/// }
|
|
/// }
|
|
/// ```
|
|
#[inline(never)]
|
|
#[cold]
|
|
pub fn double(&mut self) {
|
|
unsafe {
|
|
let elem_size = mem::size_of::<T>();
|
|
|
|
// since we set the capacity to usize::MAX when elem_size is
|
|
// 0, getting to here necessarily means the RawVec is overfull.
|
|
assert!(elem_size != 0, "capacity overflow");
|
|
|
|
let align = mem::align_of::<T>();
|
|
|
|
let (new_cap, ptr) = if self.cap == 0 {
|
|
// skip to 4 because tiny Vec's are dumb; but not if that would cause overflow
|
|
let new_cap = if elem_size > (!0) / 8 { 1 } else { 4 };
|
|
let ptr = heap::allocate(new_cap * elem_size, align);
|
|
(new_cap, ptr)
|
|
} else {
|
|
// Since we guarantee that we never allocate more than isize::MAX bytes,
|
|
// `elem_size * self.cap <= isize::MAX` as a precondition, so this can't overflow
|
|
let new_cap = 2 * self.cap;
|
|
let new_alloc_size = new_cap * elem_size;
|
|
alloc_guard(new_alloc_size);
|
|
let ptr = heap::reallocate(self.ptr() as *mut _,
|
|
self.cap * elem_size,
|
|
new_alloc_size,
|
|
align);
|
|
(new_cap, ptr)
|
|
};
|
|
|
|
// If allocate or reallocate fail, we'll get `null` back
|
|
if ptr.is_null() {
|
|
oom()
|
|
}
|
|
|
|
self.ptr = Unique::new(ptr as *mut _);
|
|
self.cap = new_cap;
|
|
}
|
|
}
|
|
|
|
/// Attempts to double the size of the type's backing allocation in place. This is common
|
|
/// enough to want to do that it's easiest to just have a dedicated method. Slightly
|
|
/// more efficient logic can be provided for this than the general case.
|
|
///
|
|
/// Returns true if the reallocation attempt has succeeded, or false otherwise.
|
|
///
|
|
/// # Panics
|
|
///
|
|
/// * Panics if T is zero-sized on the assumption that you managed to exhaust
|
|
/// all `usize::MAX` slots in your imaginary buffer.
|
|
/// * Panics on 32-bit platforms if the requested capacity exceeds
|
|
/// `isize::MAX` bytes.
|
|
#[inline(never)]
|
|
#[cold]
|
|
pub fn double_in_place(&mut self) -> bool {
|
|
unsafe {
|
|
let elem_size = mem::size_of::<T>();
|
|
let align = mem::align_of::<T>();
|
|
|
|
// since we set the capacity to usize::MAX when elem_size is
|
|
// 0, getting to here necessarily means the RawVec is overfull.
|
|
assert!(elem_size != 0, "capacity overflow");
|
|
|
|
// Since we guarantee that we never allocate more than isize::MAX bytes,
|
|
// `elem_size * self.cap <= isize::MAX` as a precondition, so this can't overflow
|
|
let new_cap = 2 * self.cap;
|
|
let new_alloc_size = new_cap * elem_size;
|
|
|
|
alloc_guard(new_alloc_size);
|
|
let size = heap::reallocate_inplace(self.ptr() as *mut _,
|
|
self.cap * elem_size,
|
|
new_alloc_size,
|
|
align);
|
|
if size >= new_alloc_size {
|
|
// We can't directly divide `size`.
|
|
self.cap = new_cap;
|
|
}
|
|
size >= new_alloc_size
|
|
}
|
|
}
|
|
|
|
/// Ensures that the buffer contains at least enough space to hold
|
|
/// `used_cap + needed_extra_cap` elements. If it doesn't already,
|
|
/// will reallocate the minimum possible amount of memory necessary.
|
|
/// Generally this will be exactly the amount of memory necessary,
|
|
/// but in principle the allocator is free to give back more than
|
|
/// we asked for.
|
|
///
|
|
/// If `used_cap` exceeds `self.cap()`, this may fail to actually allocate
|
|
/// the requested space. This is not really unsafe, but the unsafe
|
|
/// code *you* write that relies on the behavior of this function may break.
|
|
///
|
|
/// # Panics
|
|
///
|
|
/// * Panics if the requested capacity exceeds `usize::MAX` bytes.
|
|
/// * Panics on 32-bit platforms if the requested capacity exceeds
|
|
/// `isize::MAX` bytes.
|
|
///
|
|
/// # Aborts
|
|
///
|
|
/// Aborts on OOM
|
|
pub fn reserve_exact(&mut self, used_cap: usize, needed_extra_cap: usize) {
|
|
unsafe {
|
|
let elem_size = mem::size_of::<T>();
|
|
let align = mem::align_of::<T>();
|
|
|
|
// NOTE: we don't early branch on ZSTs here because we want this
|
|
// to actually catch "asking for more than usize::MAX" in that case.
|
|
// If we make it past the first branch then we are guaranteed to
|
|
// panic.
|
|
|
|
// Don't actually need any more capacity.
|
|
// Wrapping in case they gave a bad `used_cap`.
|
|
if self.cap().wrapping_sub(used_cap) >= needed_extra_cap {
|
|
return;
|
|
}
|
|
|
|
// Nothing we can really do about these checks :(
|
|
let new_cap = used_cap.checked_add(needed_extra_cap).expect("capacity overflow");
|
|
let new_alloc_size = new_cap.checked_mul(elem_size).expect("capacity overflow");
|
|
alloc_guard(new_alloc_size);
|
|
|
|
let ptr = if self.cap == 0 {
|
|
heap::allocate(new_alloc_size, align)
|
|
} else {
|
|
heap::reallocate(self.ptr() as *mut _,
|
|
self.cap * elem_size,
|
|
new_alloc_size,
|
|
align)
|
|
};
|
|
|
|
// If allocate or reallocate fail, we'll get `null` back
|
|
if ptr.is_null() {
|
|
oom()
|
|
}
|
|
|
|
self.ptr = Unique::new(ptr as *mut _);
|
|
self.cap = new_cap;
|
|
}
|
|
}
|
|
|
|
/// Calculates the buffer's new size given that it'll hold `used_cap +
|
|
/// needed_extra_cap` elements. This logic is used in amortized reserve methods.
|
|
/// Returns `(new_capacity, new_alloc_size)`.
|
|
fn amortized_new_size(&self, used_cap: usize, needed_extra_cap: usize) -> (usize, usize) {
|
|
let elem_size = mem::size_of::<T>();
|
|
// Nothing we can really do about these checks :(
|
|
let required_cap = used_cap.checked_add(needed_extra_cap)
|
|
.expect("capacity overflow");
|
|
// Cannot overflow, because `cap <= isize::MAX`, and type of `cap` is `usize`.
|
|
let double_cap = self.cap * 2;
|
|
// `double_cap` guarantees exponential growth.
|
|
let new_cap = cmp::max(double_cap, required_cap);
|
|
let new_alloc_size = new_cap.checked_mul(elem_size).expect("capacity overflow");
|
|
(new_cap, new_alloc_size)
|
|
}
|
|
|
|
/// Ensures that the buffer contains at least enough space to hold
|
|
/// `used_cap + needed_extra_cap` elements. If it doesn't already have
|
|
/// enough capacity, will reallocate enough space plus comfortable slack
|
|
/// space to get amortized `O(1)` behavior. Will limit this behavior
|
|
/// if it would needlessly cause itself to panic.
|
|
///
|
|
/// If `used_cap` exceeds `self.cap()`, this may fail to actually allocate
|
|
/// the requested space. This is not really unsafe, but the unsafe
|
|
/// code *you* write that relies on the behavior of this function may break.
|
|
///
|
|
/// This is ideal for implementing a bulk-push operation like `extend`.
|
|
///
|
|
/// # Panics
|
|
///
|
|
/// * Panics if the requested capacity exceeds `usize::MAX` bytes.
|
|
/// * Panics on 32-bit platforms if the requested capacity exceeds
|
|
/// `isize::MAX` bytes.
|
|
///
|
|
/// # Aborts
|
|
///
|
|
/// Aborts on OOM
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```ignore
|
|
/// struct MyVec<T> {
|
|
/// buf: RawVec<T>,
|
|
/// len: usize,
|
|
/// }
|
|
///
|
|
/// impl<T> MyVec<T> {
|
|
/// pub fn push_all(&mut self, elems: &[T]) {
|
|
/// self.buf.reserve(self.len, elems.len());
|
|
/// // reserve would have aborted or panicked if the len exceeded
|
|
/// // `isize::MAX` so this is safe to do unchecked now.
|
|
/// for x in elems {
|
|
/// unsafe {
|
|
/// ptr::write(self.buf.ptr().offset(self.len as isize), x.clone());
|
|
/// }
|
|
/// self.len += 1;
|
|
/// }
|
|
/// }
|
|
/// }
|
|
/// ```
|
|
pub fn reserve(&mut self, used_cap: usize, needed_extra_cap: usize) {
|
|
unsafe {
|
|
let elem_size = mem::size_of::<T>();
|
|
let align = mem::align_of::<T>();
|
|
|
|
// NOTE: we don't early branch on ZSTs here because we want this
|
|
// to actually catch "asking for more than usize::MAX" in that case.
|
|
// If we make it past the first branch then we are guaranteed to
|
|
// panic.
|
|
|
|
// Don't actually need any more capacity.
|
|
// Wrapping in case they give a bad `used_cap`
|
|
if self.cap().wrapping_sub(used_cap) >= needed_extra_cap {
|
|
return;
|
|
}
|
|
|
|
let (new_cap, new_alloc_size) = self.amortized_new_size(used_cap, needed_extra_cap);
|
|
// FIXME: may crash and burn on over-reserve
|
|
alloc_guard(new_alloc_size);
|
|
|
|
let ptr = if self.cap == 0 {
|
|
heap::allocate(new_alloc_size, align)
|
|
} else {
|
|
heap::reallocate(self.ptr() as *mut _,
|
|
self.cap * elem_size,
|
|
new_alloc_size,
|
|
align)
|
|
};
|
|
|
|
// If allocate or reallocate fail, we'll get `null` back
|
|
if ptr.is_null() {
|
|
oom()
|
|
}
|
|
|
|
self.ptr = Unique::new(ptr as *mut _);
|
|
self.cap = new_cap;
|
|
}
|
|
}
|
|
|
|
/// Attempts to ensure that the buffer contains at least enough space to hold
|
|
/// `used_cap + needed_extra_cap` elements. If it doesn't already have
|
|
/// enough capacity, will reallocate in place enough space plus comfortable slack
|
|
/// space to get amortized `O(1)` behaviour. Will limit this behaviour
|
|
/// if it would needlessly cause itself to panic.
|
|
///
|
|
/// If `used_cap` exceeds `self.cap()`, this may fail to actually allocate
|
|
/// the requested space. This is not really unsafe, but the unsafe
|
|
/// code *you* write that relies on the behaviour of this function may break.
|
|
///
|
|
/// Returns true if the reallocation attempt has succeeded, or false otherwise.
|
|
///
|
|
/// # Panics
|
|
///
|
|
/// * Panics if the requested capacity exceeds `usize::MAX` bytes.
|
|
/// * Panics on 32-bit platforms if the requested capacity exceeds
|
|
/// `isize::MAX` bytes.
|
|
pub fn reserve_in_place(&mut self, used_cap: usize, needed_extra_cap: usize) -> bool {
|
|
unsafe {
|
|
let elem_size = mem::size_of::<T>();
|
|
let align = mem::align_of::<T>();
|
|
|
|
// NOTE: we don't early branch on ZSTs here because we want this
|
|
// to actually catch "asking for more than usize::MAX" in that case.
|
|
// If we make it past the first branch then we are guaranteed to
|
|
// panic.
|
|
|
|
// Don't actually need any more capacity. If the current `cap` is 0, we can't
|
|
// reallocate in place.
|
|
// Wrapping in case they give a bad `used_cap`
|
|
if self.cap().wrapping_sub(used_cap) >= needed_extra_cap || self.cap == 0 {
|
|
return false;
|
|
}
|
|
|
|
let (_, new_alloc_size) = self.amortized_new_size(used_cap, needed_extra_cap);
|
|
// FIXME: may crash and burn on over-reserve
|
|
alloc_guard(new_alloc_size);
|
|
|
|
let size = heap::reallocate_inplace(self.ptr() as *mut _,
|
|
self.cap * elem_size,
|
|
new_alloc_size,
|
|
align);
|
|
if size >= new_alloc_size {
|
|
self.cap = new_alloc_size / elem_size;
|
|
}
|
|
size >= new_alloc_size
|
|
}
|
|
}
|
|
|
|
/// Shrinks the allocation down to the specified amount. If the given amount
|
|
/// is 0, actually completely deallocates.
|
|
///
|
|
/// # Panics
|
|
///
|
|
/// Panics if the given amount is *larger* than the current capacity.
|
|
///
|
|
/// # Aborts
|
|
///
|
|
/// Aborts on OOM.
|
|
pub fn shrink_to_fit(&mut self, amount: usize) {
|
|
let elem_size = mem::size_of::<T>();
|
|
let align = mem::align_of::<T>();
|
|
|
|
// Set the `cap` because they might be about to promote to a `Box<[T]>`
|
|
if elem_size == 0 {
|
|
self.cap = amount;
|
|
return;
|
|
}
|
|
|
|
// This check is my waterloo; it's the only thing Vec wouldn't have to do.
|
|
assert!(self.cap >= amount, "Tried to shrink to a larger capacity");
|
|
|
|
if amount == 0 {
|
|
mem::replace(self, RawVec::new());
|
|
} else if self.cap != amount {
|
|
unsafe {
|
|
// Overflow check is unnecessary as the vector is already at
|
|
// least this large.
|
|
let ptr = heap::reallocate(self.ptr() as *mut _,
|
|
self.cap * elem_size,
|
|
amount * elem_size,
|
|
align);
|
|
if ptr.is_null() {
|
|
oom()
|
|
}
|
|
self.ptr = Unique::new(ptr as *mut _);
|
|
}
|
|
self.cap = amount;
|
|
}
|
|
}
|
|
|
|
/// Converts the entire buffer into `Box<[T]>`.
|
|
///
|
|
/// While it is not *strictly* Undefined Behavior to call
|
|
/// this procedure while some of the RawVec is uninitialized,
|
|
/// it certainly makes it trivial to trigger it.
|
|
///
|
|
/// Note that this will correctly reconstitute any `cap` changes
|
|
/// that may have been performed. (see description of type for details)
|
|
pub unsafe fn into_box(self) -> Box<[T]> {
|
|
// NOTE: not calling `cap()` here, actually using the real `cap` field!
|
|
let slice = slice::from_raw_parts_mut(self.ptr(), self.cap);
|
|
let output: Box<[T]> = Box::from_raw(slice);
|
|
mem::forget(self);
|
|
output
|
|
}
|
|
}
|
|
|
|
impl<T> Drop for RawVec<T> {
|
|
#[unsafe_destructor_blind_to_params]
|
|
/// Frees the memory owned by the RawVec *without* trying to Drop its contents.
|
|
fn drop(&mut self) {
|
|
let elem_size = mem::size_of::<T>();
|
|
if elem_size != 0 && self.cap != 0 {
|
|
let align = mem::align_of::<T>();
|
|
|
|
let num_bytes = elem_size * self.cap;
|
|
unsafe {
|
|
heap::deallocate(*self.ptr as *mut _, num_bytes, align);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
|
|
// We need to guarantee the following:
|
|
// * We don't ever allocate `> isize::MAX` byte-size objects
|
|
// * We don't overflow `usize::MAX` and actually allocate too little
|
|
//
|
|
// On 64-bit we just need to check for overflow since trying to allocate
|
|
// `> isize::MAX` bytes will surely fail. On 32-bit and 16-bit we need to add
|
|
// an extra guard for this in case we're running on a platform which can use
|
|
// all 4GB in user-space. e.g. PAE or x32
|
|
|
|
#[inline]
|
|
fn alloc_guard(alloc_size: usize) {
|
|
if mem::size_of::<usize>() < 8 {
|
|
assert!(alloc_size <= ::core::isize::MAX as usize,
|
|
"capacity overflow");
|
|
}
|
|
}
|
|
|
|
|
|
#[cfg(test)]
|
|
mod tests {
|
|
use super::*;
|
|
|
|
#[test]
|
|
fn reserve_does_not_overallocate() {
|
|
{
|
|
let mut v: RawVec<u32> = RawVec::new();
|
|
// First `reserve` allocates like `reserve_exact`
|
|
v.reserve(0, 9);
|
|
assert_eq!(9, v.cap());
|
|
}
|
|
|
|
{
|
|
let mut v: RawVec<u32> = RawVec::new();
|
|
v.reserve(0, 7);
|
|
assert_eq!(7, v.cap());
|
|
// 97 if more than double of 7, so `reserve` should work
|
|
// like `reserve_exact`.
|
|
v.reserve(7, 90);
|
|
assert_eq!(97, v.cap());
|
|
}
|
|
|
|
{
|
|
let mut v: RawVec<u32> = RawVec::new();
|
|
v.reserve(0, 12);
|
|
assert_eq!(12, v.cap());
|
|
v.reserve(12, 3);
|
|
// 3 is less than half of 12, so `reserve` must grow
|
|
// exponentially. At the time of writing this test grow
|
|
// factor is 2, so new capacity is 24, however, grow factor
|
|
// of 1.5 is OK too. Hence `>= 18` in assert.
|
|
assert!(v.cap() >= 12 + 12 / 2);
|
|
}
|
|
}
|
|
|
|
}
|