casper_wasmi/
global.rs

1use crate::{pwasm::PwasmCompat, Error, RuntimeValue, ValueType};
2use alloc::rc::Rc;
3use casper_wasm::elements::ValueType as EValueType;
4use core::cell::Cell;
5
6/// Reference to a global variable (See [`GlobalInstance`] for details).
7///
8/// This reference has a reference-counting semantics.
9///
10/// [`GlobalInstance`]: struct.GlobalInstance.html
11#[derive(Clone, Debug)]
12pub struct GlobalRef(Rc<GlobalInstance>);
13
14impl ::core::ops::Deref for GlobalRef {
15    type Target = GlobalInstance;
16    fn deref(&self) -> &GlobalInstance {
17        &self.0
18    }
19}
20
21/// Runtime representation of a global variable (or `global` for short).
22///
23/// Global contains a value of a specified type and flag which specifies whether this
24/// global are mutable or immutable. Neither type of the value nor immutability can't be changed
25/// after creation.
26///
27/// Attempt to change value of immutable global or to change type of
28/// the value (e.g. assign [`I32`] value to a global that was created with [`I64`] type) will lead to an error.
29///
30/// [`I32`]: enum.Value.html#variant.I32
31/// [`I64`]: enum.Value.html#variant.I64
32#[derive(Debug)]
33pub struct GlobalInstance {
34    val: Cell<RuntimeValue>,
35    mutable: bool,
36}
37
38impl GlobalInstance {
39    /// Allocate a global variable instance.
40    ///
41    /// Since it is possible to export only immutable globals,
42    /// users likely want to set `mutable` to `false`.
43    pub fn alloc(val: RuntimeValue, mutable: bool) -> GlobalRef {
44        GlobalRef(Rc::new(GlobalInstance {
45            val: Cell::new(val),
46            mutable,
47        }))
48    }
49
50    /// Change the value of this global variable.
51    ///
52    /// # Errors
53    ///
54    /// Returns `Err` if this global isn't mutable or if
55    /// type of `val` doesn't match global's type.
56    pub fn set(&self, val: RuntimeValue) -> Result<(), Error> {
57        if !self.mutable {
58            return Err(Error::Global(
59                "Attempt to change an immutable variable".into(),
60            ));
61        }
62        if self.value_type() != val.value_type() {
63            return Err(Error::Global("Attempt to change variable type".into()));
64        }
65        self.val.set(val);
66        Ok(())
67    }
68
69    /// Get the value of this global variable.
70    pub fn get(&self) -> RuntimeValue {
71        self.val.get()
72    }
73
74    /// Returns if this global variable is mutable.
75    ///
76    /// Note: Imported and/or exported globals are always immutable.
77    pub fn is_mutable(&self) -> bool {
78        self.mutable
79    }
80
81    /// Returns value type of this global variable.
82    pub fn value_type(&self) -> ValueType {
83        self.val.get().value_type()
84    }
85
86    pub(crate) fn elements_value_type(&self) -> EValueType {
87        self.value_type().into_elements()
88    }
89}
casper_wasmi/global.rs

casper_wasmi/
global.rs
