Struct pages::Page [−][src]
#[repr(transparent)]pub struct Page<H, T>(_);
Expand description
An owned, heap-backed, dynamically-sized data page comprising a user-chosen
header and data array packed into a single allocation. It is an owned object and
the internal representation is a [NonNull
].
Example
use pages::Page; use core::mem::MaybeUninit; // A really crappy replacement for Box<Option<usize>> struct Maybe(Page::<bool, usize>); impl Maybe { fn new() -> Self { Maybe(Page::new(false, 1)) } fn put(&mut self, value: usize) { *self.0.header_mut() = true; // occupied unsafe { self.0.data().write(MaybeUninit::new(value)) }; } fn get(&mut self) -> Option<usize> { if !(*self.0.header()) { return None; } *self.0.header_mut() = false; // free Some(unsafe { self.0.data().read().assume_init() }) } } let mut maybe = Maybe::new(); assert_eq!(maybe.get(), None); maybe.put(42); assert_eq!(maybe.get(), Some(42));
Notes
Data is exposed as a MaybeUninit
pointer for maximum flexibility.
Unfortunately this means we’re unable to automatically drop the data
for you in our destructor. You could cause a memory leak if you don’t.
Implementations
Access to this page’s header by mut reference.
Access to the start of the data array as a mut pointer.
Returns the PageLayout
describing the memory layout of this Page
Creates a new Page
from a pointer to uninitialised memory, a header and
a PageLayout
.
Safety
You must ensure:
- The pointer was allocated according to the provided
PageLayout
.- Synchronise all reads and writes to
- Suppress the destructor of all but one of them (e.g. by wrapping in [
ManuallyDrop
]).
- If the pointer did not originate from the global allocator, you must
suppress the destructor (e.g. by wrapping in [
ManuallyDrop
]).