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use super::{AsContext, AsContextMut, Stored};
use crate::{
collections::arena::ArenaIndex,
core::{UntypedVal, ValType},
value::WithType,
Val,
};
use core::{fmt, fmt::Display, ptr::NonNull};
/// A raw index to a global variable entity.
#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
pub struct GlobalIdx(u32);
impl ArenaIndex for GlobalIdx {
fn into_usize(self) -> usize {
self.0 as usize
}
fn from_usize(value: usize) -> Self {
let value = value.try_into().unwrap_or_else(|error| {
panic!("index {value} is out of bounds as global index: {error}")
});
Self(value)
}
}
/// An error that may occur upon operating on global variables.
#[derive(Debug)]
#[non_exhaustive]
pub enum GlobalError {
/// Occurs when trying to write to an immutable global variable.
ImmutableWrite,
/// Occurs when trying writing a value with mismatching type to a global variable.
TypeMismatch {
/// The type of the global variable.
expected: ValType,
/// The type of the new value that mismatches the type of the global variable.
encountered: ValType,
},
/// Occurs when a global type does not satisfy the constraints of another.
UnsatisfyingGlobalType {
/// The unsatisfying [`GlobalType`].
unsatisfying: GlobalType,
/// The required [`GlobalType`].
required: GlobalType,
},
}
#[cfg(feature = "std")]
impl std::error::Error for GlobalError {}
impl Display for GlobalError {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self {
Self::ImmutableWrite => write!(f, "tried to write to immutable global variable"),
Self::TypeMismatch {
expected,
encountered,
} => {
write!(
f,
"type mismatch upon writing global variable. \
expected {expected:?} but encountered {encountered:?}.",
)
}
Self::UnsatisfyingGlobalType {
unsatisfying,
required,
} => {
write!(
f,
"global type {unsatisfying:?} does not \
satisfy requirements of {required:?}",
)
}
}
}
}
/// The mutability of a global variable.
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub enum Mutability {
/// The value of the global variable is a constant.
Const,
/// The value of the global variable is mutable.
Var,
}
impl Mutability {
/// Returns `true` if this mutability is [`Mutability::Const`].
pub fn is_const(&self) -> bool {
matches!(self, Self::Const)
}
/// Returns `true` if this mutability is [`Mutability::Var`].
pub fn is_mut(&self) -> bool {
matches!(self, Self::Var)
}
}
/// The type of a global variable.
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub struct GlobalType {
/// The value type of the global variable.
content: ValType,
/// The mutability of the global variable.
mutability: Mutability,
}
impl GlobalType {
/// Creates a new [`GlobalType`] from the given [`ValType`] and [`Mutability`].
pub fn new(content: ValType, mutability: Mutability) -> Self {
Self {
content,
mutability,
}
}
/// Returns the [`ValType`] of the global variable.
pub fn content(&self) -> ValType {
self.content
}
/// Returns the [`Mutability`] of the global variable.
pub fn mutability(&self) -> Mutability {
self.mutability
}
/// Checks if `self` satisfies the given `GlobalType`.
///
/// # Errors
///
/// - If the initial limits of the `required` [`GlobalType`] are greater than `self`.
/// - If the maximum limits of the `required` [`GlobalType`] are greater than `self`.
pub(crate) fn satisfies(&self, required: &GlobalType) -> Result<(), GlobalError> {
if self != required {
return Err(GlobalError::UnsatisfyingGlobalType {
unsatisfying: *self,
required: *required,
});
}
Ok(())
}
}
/// A global variable entity.
#[derive(Debug)]
pub struct GlobalEntity {
/// The current value of the global variable.
value: UntypedVal,
/// The type of the global variable.
ty: GlobalType,
}
impl GlobalEntity {
/// Creates a new global entity with the given initial value and mutability.
pub fn new(initial_value: Val, mutability: Mutability) -> Self {
Self {
ty: GlobalType::new(initial_value.ty(), mutability),
value: initial_value.into(),
}
}
/// Returns the [`GlobalType`] of the global variable.
pub fn ty(&self) -> GlobalType {
self.ty
}
/// Sets a new value to the global variable.
///
/// # Errors
///
/// - If the global variable is immutable.
/// - If there is a type mismatch between the global variable and the new value.
pub fn set(&mut self, new_value: Val) -> Result<(), GlobalError> {
if !self.ty().mutability().is_mut() {
return Err(GlobalError::ImmutableWrite);
}
if self.ty().content() != new_value.ty() {
return Err(GlobalError::TypeMismatch {
expected: self.ty().content(),
encountered: new_value.ty(),
});
}
self.set_untyped(new_value.into());
Ok(())
}
/// Sets a new untyped value for the global variable.
///
/// # Note
///
/// This is an inherently unsafe API and only exists to allow
/// for efficient `global.set` through the interpreter which is
/// safe since the interpreter only handles validated Wasm code
/// where the checks in [`Global::set`] cannot fail.
pub(crate) fn set_untyped(&mut self, new_value: UntypedVal) {
self.value = new_value;
}
/// Returns the current value of the global variable.
pub fn get(&self) -> Val {
self.get_untyped().with_type(self.ty().content())
}
/// Returns the current untyped value of the global variable.
pub(crate) fn get_untyped(&self) -> UntypedVal {
self.value
}
/// Returns a pointer to the untyped value of the global variable.
pub(crate) fn get_untyped_ptr(&mut self) -> NonNull<UntypedVal> {
NonNull::from(&mut self.value)
}
}
/// A Wasm global variable reference.
#[derive(Debug, Copy, Clone)]
#[repr(transparent)]
pub struct Global(Stored<GlobalIdx>);
impl Global {
/// Creates a new stored global variable reference.
///
/// # Note
///
/// This API is primarily used by the [`Store`] itself.
///
/// [`Store`]: [`crate::Store`]
pub(super) fn from_inner(stored: Stored<GlobalIdx>) -> Self {
Self(stored)
}
/// Returns the underlying stored representation.
pub(super) fn as_inner(&self) -> &Stored<GlobalIdx> {
&self.0
}
/// Creates a new global variable to the store.
pub fn new(mut ctx: impl AsContextMut, initial_value: Val, mutability: Mutability) -> Self {
ctx.as_context_mut()
.store
.inner
.alloc_global(GlobalEntity::new(initial_value, mutability))
}
/// Returns the [`GlobalType`] of the global variable.
pub fn ty(&self, ctx: impl AsContext) -> GlobalType {
ctx.as_context().store.inner.resolve_global(self).ty()
}
/// Sets a new value to the global variable.
///
/// # Errors
///
/// - If the global variable is immutable.
/// - If there is a type mismatch between the global variable and the new value.
///
/// # Panics
///
/// Panics if `ctx` does not own this [`Global`].
pub fn set(&self, mut ctx: impl AsContextMut, new_value: Val) -> Result<(), GlobalError> {
ctx.as_context_mut()
.store
.inner
.resolve_global_mut(self)
.set(new_value)
}
/// Returns the current value of the global variable.
///
/// # Panics
///
/// Panics if `ctx` does not own this [`Global`].
pub fn get(&self, ctx: impl AsContext) -> Val {
ctx.as_context().store.inner.resolve_global(self).get()
}
}