## IsolatedAlloc

# Struct IsolatedAlloc

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    pub struct IsolatedAlloc {
        page_ptrs: Vec<NonNull<u8>>,
        page_infos: Vec<DenseBitSet<usize>>,
        huge_ptrs: Vec<(NonNull<u8>, usize)>,
        page_size: usize,
    }

Expand description

A dedicated allocator for interpreter memory contents, ensuring they are stored on dedicated pages (not mixed with Miri’s own memory). This is used in native-lib mode.

## Fields§

§`page_ptrs: Vec<NonNull<u8>>`

Pointers to page-aligned memory that has been claimed by the allocator. Every pointer here must point to a page-sized allocation claimed via mmap. These pointers are used for “small” allocations.

§`page_infos: Vec<DenseBitSet<usize>>`

Metadata about which bytes have been allocated on each page. The length of this vector must be the same as that of `page_ptrs`, and the domain size of the bitset must be exactly `page_size / COMPRESSION_FACTOR`.

Conceptually, each bit of the bitset represents the allocation status of one n-byte chunk on the corresponding element of `page_ptrs`. Thus, indexing into it should be done with a value one-nth of the corresponding offset on the matching `page_ptrs` element (n = `COMPRESSION_FACTOR`).

§`huge_ptrs: Vec<(NonNull<u8>, usize)>`

Pointers to multiple-page-sized allocations. These must also be page-aligned, with their size stored as the second element of the vector.

§`page_size: usize`

The host (not emulated) page size.

## Implementations§

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### impl IsolatedAlloc

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#### pub fn new() -> Self

Creates an empty allocator.

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#### pub fn page_size(&self) -> usize

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#### fn normalized_layout(layout: Layout) -> Layout

For simplicity, we serve small allocations in multiples of COMPRESSION_FACTOR bytes with at least that alignment.

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#### fn huge_normalized_layout(&self, layout: Layout) -> usize

For greater-than-page-sized allocations, returns the allocation size we need to request including the slack we need to satisfy the alignment request.

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#### fn is_huge_alloc(&self, layout: &Layout) -> bool

Determined whether a given normalized (size, align) should be sent to `alloc_huge` / `dealloc_huge`.

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#### pub unsafe fn alloc(&mut self, layout: Layout) -> *mut u8

Allocates memory as described in `Layout`. This memory should be deallocated by calling `dealloc` on this same allocator.

SAFETY: See `alloc::alloc()`.

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#### pub unsafe fn alloc_zeroed(&mut self, layout: Layout) -> *mut u8

Same as `alloc`, but zeroes out the memory.

SAFETY: See `alloc::alloc_zeroed()`.

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#### unsafe fn allocate(&mut self, layout: Layout, zeroed: bool) -> *mut u8

Abstracts over the logic of `alloc_zeroed` vs `alloc`, as determined by the `zeroed` argument.

SAFETY: See `alloc::alloc()`.

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#### unsafe fn alloc_small( page_size: usize, layout: Layout, page: NonNull<u8>, pinfo: &mut DenseBitSet<usize>, zeroed: bool, ) -> Option<*mut u8>

Used internally by `allocate` to abstract over some logic.

SAFETY: `page` must be a page-aligned pointer to an allocated page, where the allocation is (at least) `page_size` bytes.

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#### fn add_page(&mut self) -> (NonNull<u8>, &mut DenseBitSet<usize>)

Expands the available memory pool by adding one page.

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#### unsafe fn alloc_huge(&mut self, layout: Layout) -> *mut u8

Allocates in multiples of one page on the host system. Will always be zeroed.

SAFETY: Same as `alloc()`.

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#### pub unsafe fn dealloc(&mut self, ptr: *mut u8, layout: Layout)

Deallocates a pointer from this allocator.

SAFETY: This pointer must have been allocated by calling `alloc()` (or `alloc_zeroed()`) with the same layout as the one passed on this same `IsolatedAlloc`.

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#### unsafe fn dealloc_small(&mut self, ptr: *mut u8, layout: Layout) -> usize

Returns the index of the page that this was deallocated from.

SAFETY: the pointer must have been allocated with `alloc_small`.

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#### unsafe fn dealloc_huge(&mut self, ptr: *mut u8, layout: Layout)

SAFETY: Same as `dealloc()` with the added requirement that `layout` must ask for a size larger than the host pagesize.

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#### pub fn pages(&self) -> impl Iterator<Item = (NonNull<u8>, usize)>

Returns a list of page ranges managed by the allocator, given in terms of pointers and size (in bytes).

## Trait Implementations§

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### impl Debug for IsolatedAlloc

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#### fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more

## Auto Trait Implementations§

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### impl Freeze for IsolatedAlloc

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### impl RefUnwindSafe for IsolatedAlloc

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### impl !Send for IsolatedAlloc

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### impl !Sync for IsolatedAlloc

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### impl Unpin for IsolatedAlloc

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### impl UnwindSafe for IsolatedAlloc

## Blanket Implementations§

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### impl<T> Any for T
where T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
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### impl<T> Borrow<T> for T
where T: ?Sized,

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#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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### impl<T> BorrowMut<T> for T
where T: ?Sized,

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#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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### impl<T> From<T> for T

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#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T, U> Into<U> for T
where U: From<T>,

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#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T> Same for T

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#### type Output = T

Should always be `Self`
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### impl<T, U> TryFrom<U> for T
where U: Into<T>,

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#### type Error = Infallible

The type returned in the event of a conversion error.
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#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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### impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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### impl<V, T> VZip<V> for T
where V: MultiLane<T>,

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#### fn vzip(self) -> V

## Layout§

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain `repr(...)` attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 80 bytes