Struct wasmer::Memory [−][src]
pub struct Memory { /* fields omitted */ }
Expand description
A WebAssembly memory
instance.
A memory instance is the runtime representation of a linear memory. It consists of a vector of bytes and an optional maximum size.
The length of the vector always is a multiple of the WebAssembly page size, which is defined to be the constant 65536 – abbreviated 64Ki. Like in a memory type, the maximum size in a memory instance is given in units of this page size.
A memory created by the host or in WebAssembly code will be accessible and mutable from both host and WebAssembly.
Spec: https://webassembly.github.io/spec/core/exec/runtime.html#memory-instances
Implementations
Creates a new host Memory
from the provided MemoryType
.
This function will construct the Memory
using the store
BaseTunables
.
Example
let m = Memory::new(&store, MemoryType::new(1, None, false)).unwrap();
Returns the MemoryType
of the Memory
.
Example
let mt = MemoryType::new(1, None, false);
let m = Memory::new(&store, mt).unwrap();
assert_eq!(m.ty(), mt);
Retrieve a slice of the memory contents.
Safety
Until the returned slice is dropped, it is undefined behaviour to modify the memory contents in any way including by calling a wasm function that writes to the memory or by resizing the memory.
Retrieve a mutable slice of the memory contents.
Safety
This method provides interior mutability without an UnsafeCell. Until the returned value is dropped, it is undefined behaviour to read or write to the pointed-to memory in any way except through this slice, including by calling a wasm function that reads the memory contents or by resizing this Memory.
Grow memory by the specified amount of WebAssembly Pages
and return
the previous memory size.
Example
let m = Memory::new(&store, MemoryType::new(1, Some(3), false)).unwrap();
let p = m.grow(2).unwrap();
assert_eq!(p, Pages(1));
assert_eq!(m.size(), Pages(3));
Errors
Returns an error if memory can’t be grown by the specified amount of pages.
let m = Memory::new(&store, MemoryType::new(1, Some(1), false)).unwrap();
// This results in an error: `MemoryError::CouldNotGrow`.
let s = m.grow(1).unwrap();
Return a “view” of the currently accessible memory. By
default, the view is unsynchronized, using regular memory
accesses. You can force a memory view to use atomic accesses
by calling the MemoryView::atomically
method.
Notes:
This method is safe (as in, it won’t cause the host to crash or have UB), but it doesn’t obey rust’s rules involving data races, especially concurrent ones. Therefore, if this memory is shared between multiple threads, a single memory location can be mutated concurrently without synchronization.
Usage:
// Without synchronization.
let view: MemoryView<u8> = memory.view();
for byte in view[0x1000 .. 0x1010].iter().map(Cell::get) {
println!("byte: {}", byte);
}
// With synchronization.
let atomic_view = view.atomically();
for byte in atomic_view[0x1000 .. 0x1010].iter().map(|atom| atom.load(Ordering::SeqCst)) {
println!("byte: {}", byte);
}
Trait Implementations
Convert the extern internally to hold a weak reference to the InstanceRef
.
This is useful for preventing cycles, for example for data stored in a
type implementing WasmerEnv
. Read more
Returns the size of the referenced value in bytes. Read more
Auto Trait Implementations
impl !RefUnwindSafe for Memory
impl !UnwindSafe for Memory
Blanket Implementations
type ArchivedMetadata = ()
type ArchivedMetadata = ()
The archived version of the pointer metadata for this type.
pub fn pointer_metadata(
&<T as ArchivePointee>::ArchivedMetadata
) -> <T as Pointee>::Metadata
pub fn pointer_metadata(
&<T as ArchivePointee>::ArchivedMetadata
) -> <T as Pointee>::Metadata
Converts some archived metadata to the pointer metadata for itself.
Mutably borrows from an owned value. Read more
pub fn vzip(self) -> V
Attaches the provided Subscriber
to this type, returning a
WithDispatch
wrapper. Read more
Attaches the current default Subscriber
to this type, returning a
WithDispatch
wrapper. Read more