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|
use super::*;
use std::cell::Cell;
#[test]
fn allocator_param() {
use crate::alloc::AllocError;
// Writing a test of integration between third-party
// allocators and `RawVec` is a little tricky because the `RawVec`
// API does not expose fallible allocation methods, so we
// cannot check what happens when allocator is exhausted
// (beyond detecting a panic).
//
// Instead, this just checks that the `RawVec` methods do at
// least go through the Allocator API when it reserves
// storage.
// A dumb allocator that consumes a fixed amount of fuel
// before allocation attempts start failing.
struct BoundedAlloc {
fuel: Cell<usize>,
}
unsafe impl Allocator for BoundedAlloc {
fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
let size = layout.size();
if size > self.fuel.get() {
return Err(AllocError);
}
match Global.allocate(layout) {
ok @ Ok(_) => {
self.fuel.set(self.fuel.get() - size);
ok
}
err @ Err(_) => err,
}
}
unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
unsafe { Global.deallocate(ptr, layout) }
}
}
let a = BoundedAlloc { fuel: Cell::new(500) };
let mut v: RawVec<u8, _> = RawVec::with_capacity_in(50, a);
assert_eq!(v.alloc.fuel.get(), 450);
v.reserve(50, 150); // (causes a realloc, thus using 50 + 150 = 200 units of fuel)
assert_eq!(v.alloc.fuel.get(), 250);
}
#[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.capacity());
}
{
let mut v: RawVec<u32> = RawVec::new();
v.reserve(0, 7);
assert_eq!(7, v.capacity());
// 97 is more than double of 7, so `reserve` should work
// like `reserve_exact`.
v.reserve(7, 90);
assert_eq!(97, v.capacity());
}
{
let mut v: RawVec<u32> = RawVec::new();
v.reserve(0, 12);
assert_eq!(12, v.capacity());
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.capacity() >= 12 + 12 / 2);
}
}
|
