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//! This module encapsulates some logic for upvalue handling, which is
//! relevant to both thunks (delayed computations for lazy-evaluation)
//! as well as closures (lambdas that capture variables from the
//! surrounding scope).
use std::{
cell::{Ref, RefMut},
ops::Index,
};
use crate::{opcode::UpvalueIdx, Value};
/// Structure for carrying upvalues inside of thunks & closures. The
/// implementation of this struct encapsulates the logic for capturing
/// and accessing upvalues.
#[derive(Clone, Debug)]
pub struct Upvalues {
upvalues: Vec<Value>,
with_stack: Option<Vec<Value>>,
}
impl Upvalues {
pub fn with_capacity(count: usize) -> Self {
Upvalues {
upvalues: Vec::with_capacity(count),
with_stack: None,
}
}
/// Push an upvalue at the end of the upvalue list.
pub fn push(&mut self, value: Value) {
self.upvalues.push(value);
}
/// Set the captured with stack.
pub fn set_with_stack(&mut self, with_stack: Vec<Value>) {
self.with_stack = Some(with_stack);
}
pub fn with_stack(&self) -> Option<&Vec<Value>> {
self.with_stack.as_ref()
}
pub fn with_stack_len(&self) -> usize {
match &self.with_stack {
None => 0,
Some(stack) => stack.len(),
}
}
}
impl Index<UpvalueIdx> for Upvalues {
type Output = Value;
fn index(&self, index: UpvalueIdx) -> &Self::Output {
&self.upvalues[index.0]
}
}
/// `UpvalueCarrier` is implemented by all types that carry upvalues.
pub trait UpvalueCarrier {
fn upvalue_count(&self) -> usize;
/// Read-only accessor for the stored upvalues.
fn upvalues(&self) -> Ref<'_, Upvalues>;
/// Mutable accessor for stored upvalues.
fn upvalues_mut(&self) -> RefMut<'_, Upvalues>;
/// Read an upvalue at the given index.
fn upvalue(&self, idx: UpvalueIdx) -> Ref<'_, Value> {
Ref::map(self.upvalues(), |v| &v.upvalues[idx.0])
}
/// Resolve deferred upvalues from the provided stack slice,
/// mutating them in the internal upvalue slots.
fn resolve_deferred_upvalues(&self, stack: &[Value]) {
for upvalue in self.upvalues_mut().upvalues.iter_mut() {
if let Value::DeferredUpvalue(idx) = upvalue {
*upvalue = stack[idx.0].clone();
}
}
}
}
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