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use crate::sys::exports::{ExportError, Exportable};
use crate::sys::externals::Extern;
use crate::sys::store::{AsStoreMut, AsStoreRef};
use crate::sys::value::Value;
use crate::sys::GlobalType;
use crate::sys::Mutability;
use crate::sys::RuntimeError;
use wasmer_vm::{InternalStoreHandle, StoreHandle, VMExtern, VMGlobal};
/// 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>
#[derive(Debug, Clone)]
pub struct Global {
handle: StoreHandle<VMGlobal>,
}
impl Global {
/// Create a new `Global` with the initial value [`Value`].
///
/// # Example
///
/// ```
/// # use wasmer::{Global, Mutability, Store, Value};
/// # let mut store = Store::default();
/// #
/// 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(store: &mut impl AsStoreMut, val: Value) -> Self {
Self::from_value(store, val, Mutability::Const).unwrap()
}
/// Create a mutable `Global` with the initial value [`Value`].
///
/// # Example
///
/// ```
/// # use wasmer::{Global, Mutability, Store, Value};
/// # let mut store = Store::default();
/// #
/// 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 new_mut(store: &mut impl AsStoreMut, val: Value) -> Self {
Self::from_value(store, val, Mutability::Var).unwrap()
}
/// Create a `Global` with the initial value [`Value`] and the provided [`Mutability`].
fn from_value(
store: &mut impl AsStoreMut,
val: Value,
mutability: Mutability,
) -> Result<Self, RuntimeError> {
if !val.is_from_store(store) {
return Err(RuntimeError::new(
"cross-`Context` values are not supported",
));
}
let global = VMGlobal::new(GlobalType {
mutability,
ty: val.ty(),
});
unsafe {
global.vmglobal().as_mut().val = val.as_raw(store);
}
Ok(Self {
handle: StoreHandle::new(store.objects_mut(), global),
})
}
/// Returns the [`GlobalType`] of the `Global`.
///
/// # Example
///
/// ```
/// # use wasmer::{Global, Mutability, Store, Type, Value, GlobalType};
/// # let mut store = Store::default();
/// #
/// 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 ty(&self, store: &impl AsStoreRef) -> GlobalType {
*self.handle.get(store.as_store_ref().objects()).ty()
}
#[cfg(feature = "compiler")]
/// Retrieves the current value [`Value`] that the Global has.
///
/// # Example
///
/// ```
/// # use wasmer::{Global, Store, Value};
/// # let mut store = Store::default();
/// #
/// let g = Global::new(&mut store, Value::I32(1));
///
/// assert_eq!(g.get(&mut store), Value::I32(1));
/// ```
pub fn get(&self, store: &mut impl AsStoreMut) -> Value {
unsafe {
let raw = self
.handle
.get(store.as_store_ref().objects())
.vmglobal()
.as_ref()
.val;
let ty = self.handle.get(store.as_store_ref().objects()).ty().ty;
Value::from_raw(store, ty, raw)
}
}
/// Sets a custom value [`Value`] to the runtime Global.
///
/// # Example
///
/// ```
/// # use wasmer::{Global, Store, Value};
/// # let mut store = Store::default();
/// #
/// 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:
///
/// ```should_panic
/// # use wasmer::{Global, Store, Value};
/// # let mut store = Store::default();
/// #
/// 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:
///
/// ```should_panic
/// # use wasmer::{Global, Store, Value};
/// # let mut store = Store::default();
/// #
/// 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 set(&self, store: &mut impl AsStoreMut, val: Value) -> Result<(), RuntimeError> {
if !val.is_from_store(store) {
return Err(RuntimeError::new(
"cross-`Context` values are not supported",
));
}
if self.ty(store).mutability != Mutability::Var {
return Err(RuntimeError::new("Attempted to set an immutable global"));
}
if val.ty() != self.ty(store).ty {
return Err(RuntimeError::new(format!(
"Attempted to operate on a global of type {expected} as a global of type {found}",
expected = self.ty(store).ty,
found = val.ty(),
)));
}
unsafe {
self.handle
.get_mut(store.objects_mut())
.vmglobal()
.as_mut()
.val = val.as_raw(store);
}
Ok(())
}
pub(crate) fn from_vm_extern(
store: &mut impl AsStoreMut,
internal: InternalStoreHandle<VMGlobal>,
) -> Self {
Self {
handle: unsafe {
StoreHandle::from_internal(store.as_store_ref().objects().id(), internal)
},
}
}
/// Checks whether this `Global` can be used with the given context.
pub fn is_from_store(&self, store: &impl AsStoreRef) -> bool {
self.handle.store_id() == store.as_store_ref().objects().id()
}
pub(crate) fn to_vm_extern(&self) -> VMExtern {
VMExtern::Global(self.handle.internal_handle())
}
}
impl std::cmp::PartialEq for Global {
fn eq(&self, other: &Self) -> bool {
self.handle == other.handle
}
}
impl std::cmp::Eq for Global {}
impl<'a> Exportable<'a> for Global {
fn get_self_from_extern(_extern: &'a Extern) -> Result<&'a Self, ExportError> {
match _extern {
Extern::Global(global) => Ok(global),
_ => Err(ExportError::IncompatibleType),
}
}
}