Struct wasmer::Global

pub struct Global { /* private fields */ }

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

Implementations

impl Global

pub fn new(store: &Store, val: Val) -> Self

Create a new Global with the initial value Val.

Example

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

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

pub fn new_mut(store: &Store, val: Val) -> Self

Create a mutable Global with the initial value Val.

Example

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

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

pub fn ty(&self) -> &GlobalType

Returns the GlobalType of the Global.

Example

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

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

pub fn store(&self) -> &Store

Returns the Store where the Global belongs.

Example

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

assert_eq!(g.store(), &store);

pub fn get(&self) -> Val

Retrieves the current value Val that the Global has.

Example

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

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

pub fn set(&self, val: Val) -> Result<(), RuntimeError>

Sets a custom value Val to the runtime Global.

Example

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

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

g.set(Value::I32(2));

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

Errors

Trying to mutate a immutable global will raise an error:

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

g.set(Value::I32(2)).unwrap();

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

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

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

pub fn same(&self, other: &Self) -> bool

Returns whether or not these two globals refer to the same data.

Example

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

assert!(g.same(&g));

Trait Implementations

impl Clone for Global

fn clone(&self) -> Self

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, formatter: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

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

fn to_export(&self) -> Export

This function is used when providedd the Extern as exportable, so it can be used while instantiating the Module.

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

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

fn into_weak_instance_ref(&mut self)

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.

impl From<Global> for Extern

fn from(r: Global) -> Self

Performs the conversion.

impl MemoryUsage for Global

fn size_of_val(&self, visited: &mut dyn MemoryUsageTracker) -> usize

Returns the size of the referenced value in bytes.