Enum wasmtime_runtime::Memory

pub enum Memory {
    Static {
        base: &'static mut [u8],
        size: usize,
        make_accessible: fn(_: *mut u8, _: usize) -> Result<()>,
    },
    Dynamic(Box<dyn RuntimeLinearMemory>),
}

Representation of a runtime wasm linear memory.

Variants

Static

Fields

base: &'static mut [u8]

The memory in the host for this wasm memory. The length of this slice is the maximum size of the memory that can be grown to.

size: usize

The current size, in bytes, of this memory.

make_accessible: fn(_: *mut u8, _: usize) -> Result<()>

A callback which makes portions of base accessible for when memory is grown. Otherwise it’s expected that accesses to base will fault.

A “static” memory where the lifetime of the backing memory is managed elsewhere. Currently used with the pooling allocator.

Dynamic(Box<dyn RuntimeLinearMemory>)

A “dynamic” memory whose data is managed at runtime and lifetime is tied to this instance.

Implementations

impl Memory

pub fn new_dynamic(
    plan: &MemoryPlan,
    creator: &dyn RuntimeMemoryCreator,
    store: &mut dyn Store
) -> Result<Self>

Create a new dynamic (movable) memory instance for the specified plan.

pub fn new_static(
    plan: &MemoryPlan,
    base: &'static mut [u8],
    make_accessible: fn(_: *mut u8, _: usize) -> Result<()>,
    store: &mut dyn Store
) -> Result<Self>

Create a new static (immovable) memory instance for the specified plan.

pub fn byte_size(&self) -> usize

Returns the number of allocated wasm pages.

pub fn maximum_byte_size(&self) -> Option<usize>

Returns the maximum number of pages the memory can grow to at runtime.

Returns None if the memory is unbounded.

The runtime maximum may not be equal to the maximum from the linear memory’s Wasm type when it is being constrained by an instance allocator.

pub unsafe fn grow(
    &mut self,
    delta_pages: u64,
    store: &mut dyn Store
) -> Result<Option<usize>, Error>

Grow memory by the specified amount of wasm pages.

Returns None if memory can’t be grown by the specified amount of wasm pages. Returns Some with the old size of memory, in bytes, on successful growth.

Safety

Resizing the memory can reallocate the memory buffer for dynamic memories. An instance’s VMContext may have pointers to the memory’s base and will need to be fixed up after growing the memory.

Generally, prefer using InstanceHandle::memory_grow, which encapsulates this unsafety.

Ensure that the provided Store is not used to get access any Memory which lives inside it.

pub fn vmmemory(&self) -> VMMemoryDefinition

Return a VMMemoryDefinition for exposing the memory to compiled wasm code.

Trait Implementations

impl Default for Memory

fn default() -> Self

Returns the “default value” for a type.