Struct wasmtime::Global

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#[repr(transparent)]
pub struct Global(_);
Expand description

A WebAssembly global value which can be read and written to.

A global in WebAssembly is sort of like a global variable within an Instance. The global.get and global.set instructions will modify and read global values in a wasm module. Globals can either be imported or exported from wasm modules.

A Global “belongs” to the store that it was originally created within (either via Global::new or via instantiating a Module). Operations on a Global only work with the store it belongs to, and if another store is passed in by accident then methods will panic.

Implementations§

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impl Global

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pub fn new(store: impl AsContextMut, ty: GlobalType, val: Val) -> Result<Global>

Creates a new WebAssembly global value with the provide type ty and initial value val.

The store argument will be the owner of the Global returned. Using the returned Global other items in the store may access this global. For example this could be provided as an argument to Instance::new or Linker::define.

Errors

Returns an error if the ty provided does not match the type of the value val, or if val comes from a different store than store.

Examples
let engine = Engine::default();
let mut store = Store::new(&engine, ());

let ty = GlobalType::new(ValType::I32, Mutability::Const);
let i32_const = Global::new(&mut store, ty, 1i32.into())?;
let ty = GlobalType::new(ValType::F64, Mutability::Var);
let f64_mut = Global::new(&mut store, ty, 2.0f64.into())?;

let module = Module::new(
    &engine,
    "(module
        (global (import \"\" \"i32-const\") i32)
        (global (import \"\" \"f64-mut\") (mut f64))
    )"
)?;

let mut linker = Linker::new(&engine);
linker.define(&store, "", "i32-const", i32_const)?;
linker.define(&store, "", "f64-mut", f64_mut)?;

let instance = linker.instantiate(&mut store, &module)?;
// ...
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pub fn ty(&self, store: impl AsContext) -> GlobalType

Returns the underlying type of this global.

Panics

Panics if store does not own this global.

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pub fn get(&self, store: impl AsContextMut) -> Val

Returns the current Val of this global.

Panics

Panics if store does not own this global.

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pub fn set(&self, store: impl AsContextMut, val: Val) -> Result<()>

Attempts to set the current value of this global to Val.

Errors

Returns an error if this global has a different type than Val, if it’s not a mutable global, or if val comes from a different store than the one provided.

Panics

Panics if store does not own this global.

Trait Implementations§

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impl Clone for Global

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fn clone(&self) -> Global

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl Debug for Global

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

Formats the value using the given formatter. Read more
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impl From<Global> for Extern

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fn from(r: Global) -> Self

Converts to this type from the input type.
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impl Copy for Global

Auto Trait Implementations§

Blanket Implementations§

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impl<T> Any for Twhere 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 Twhere 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 Twhere 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 Twhere 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> Pointable for T

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const ALIGN: usize = mem::align_of::<T>()

The alignment of pointer.
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type Init = T

The type for initializers.
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unsafe fn init(init: <T as Pointable>::Init) -> usize

Initializes a with the given initializer. Read more
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unsafe fn deref<'a>(ptr: usize) -> &'a T

Dereferences the given pointer. Read more
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unsafe fn deref_mut<'a>(ptr: usize) -> &'a mut T

Mutably dereferences the given pointer. Read more
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unsafe fn drop(ptr: usize)

Drops the object pointed to by the given pointer. Read more
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impl<T> Same<T> for T

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type Output = T

Should always be Self
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impl<T> ToOwned for Twhere T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T, U> TryFrom<U> for Twhere 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 Twhere 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.