75 lines
1.8 KiB
Rust
75 lines
1.8 KiB
Rust
use std::rc::Rc;
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use std::cell::Cell;
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use value::RuntimeValue;
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use Error;
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use types::ValueType;
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use parity_wasm::elements::{ValueType as EValueType};
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/// Reference to a [`GlobalInstance`].
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///
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/// This reference has a reference-counting semantics.
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///
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/// [`GlobalInstance`]: struct.GlobalInstance.html
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///
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#[derive(Clone, Debug)]
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pub struct GlobalRef(Rc<GlobalInstance>);
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impl ::std::ops::Deref for GlobalRef {
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type Target = GlobalInstance;
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fn deref(&self) -> &GlobalInstance {
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&self.0
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}
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}
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/// Runtime representation of a global variable (or `global` for short).
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///
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/// Global contains a value of a specified type and flag which specifies whether this
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/// global are mutable or immutable. Neither type of the value nor immutability can't be changed
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/// after creation.
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///
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/// Attempt to change value of immutable global or to change type of
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/// the value (e.g. assign I32 value to a global that was created with I64 type) will lead to an error.
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///
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#[derive(Debug)]
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pub struct GlobalInstance {
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val: Cell<RuntimeValue>,
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mutable: bool,
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}
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impl GlobalInstance {
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pub fn alloc(val: RuntimeValue, mutable: bool) -> GlobalRef {
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GlobalRef(Rc::new(GlobalInstance {
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val: Cell::new(val),
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mutable,
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}))
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}
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pub fn set(&self, val: RuntimeValue) -> Result<(), Error> {
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if !self.mutable {
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return Err(Error::Global("Attempt to change an immutable variable".into()));
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}
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if self.value_type() != val.value_type() {
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return Err(Error::Global("Attempt to change variable type".into()));
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}
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self.val.set(val);
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Ok(())
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}
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pub fn get(&self) -> RuntimeValue {
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self.val.get()
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}
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pub fn is_mutable(&self) -> bool {
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self.mutable
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}
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pub fn value_type(&self) -> ValueType {
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self.val.get().value_type()
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}
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pub(crate) fn elements_value_type(&self) -> EValueType {
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self.value_type().into_elements()
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}
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}
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