Struct Global

pub(crate) struct Global(pub(crate) BackendGlobal);

A WebAssembly global instance.

A global instance is the runtime representation of a global variable. It consists of an individual value and a flag indicating whether it is mutable.

Spec: https://webassembly.github.io/spec/core/exec/runtime.html#global-instances

Tuple Fields

0: BackendGlobal

Implementations

impl Global

pub fn new(store: &mut impl AsStoreMut, val: Value) -> Global

Create a new global with the initial Value.

Example

let g = Global::new(&mut store, Value::I32(1));

assert_eq!(g.get(&mut store), Value::I32(1));
assert_eq!(g.ty(&mut store).mutability, Mutability::Const);

pub fn new_mut(store: &mut impl AsStoreMut, val: Value) -> Global

Create a mutable global with the initial Value.

Example

let g = Global::new_mut(&mut store, Value::I32(1));

assert_eq!(g.get(&mut store), Value::I32(1));
assert_eq!(g.ty(&mut store).mutability, Mutability::Var);

pub fn ty(&self, store: &impl AsStoreRef) -> GlobalType

Returns the [GlobalType] of the global.

Example

let c = Global::new(&mut store, Value::I32(1));
let v = Global::new_mut(&mut store, Value::I64(1));

assert_eq!(c.ty(&mut store), GlobalType::new(Type::I32, Mutability::Const));
assert_eq!(v.ty(&mut store), GlobalType::new(Type::I64, Mutability::Var));

pub fn get(&self, store: &mut impl AsStoreMut) -> Value

Retrieves the current value Value that the global has.

Example

let g = Global::new(&mut store, Value::I32(1));

assert_eq!(g.get(&mut store), Value::I32(1));

pub fn set( &self, store: &mut impl AsStoreMut, val: Value, ) -> Result<(), RuntimeError>

Sets a custom Value to the runtime global.

Example

let g = Global::new_mut(&mut store, Value::I32(1));

assert_eq!(g.get(&mut store), Value::I32(1));

g.set(&mut store, Value::I32(2));

assert_eq!(g.get(&mut store), Value::I32(2));

Errors

Trying to mutate a immutable global will raise an error:

let g = Global::new(&mut store, Value::I32(1));

g.set(&mut store, Value::I32(2)).unwrap();

Trying to set a value of a incompatible type will raise an error:

let g = Global::new(&mut store, Value::I32(1));

// This results in an error: `RuntimeError`.
g.set(&mut store, Value::I64(2)).unwrap();

pub fn is_from_store(&self, store: &impl AsStoreRef) -> bool

Checks whether this global can be used with the given context.

Trait Implementations

impl Clone for Global

fn clone(&self) -> Global

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Global

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

Formats the value using the given formatter.

impl<'a> Exportable<'a> for Global

fn get_self_from_extern(_extern: &'a Extern) -> Result<&'a Global, ExportError>

Implementation of how to get the export corresponding to the implementing type from an Instance by name.

impl From<BackendGlobal> for Global

fn from(value: BackendGlobal) -> Global

Converts to this type from the input type.

impl From<Global> for Extern

fn from(r: Global) -> Extern

Converts to this type from the input type.

impl PartialEq for Global

fn eq(&self, other: &Global) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Eq for Global

impl StructuralPartialEq for Global