essential_constraint_vm/
total_control_flow.rs

1use essential_types::convert::bool_from_word;
2
3use crate::{
4    error::{OpError, StackError, TotalControlFlowError},
5    OpResult, Stack,
6};
7
8#[cfg(test)]
9mod tests;
10
11#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
12/// Update the program to a new position or halt it.
13pub enum ProgramControlFlow {
14    /// New program counter position.
15    Pc(usize),
16    /// Halt the program.
17    Halt,
18}
19
20pub fn jump_forward_if(stack: &mut Stack, pc: usize) -> OpResult<Option<ProgramControlFlow>> {
21    let [dist, cond] = stack.pop2()?;
22    let cond = bool_from_word(cond).ok_or(TotalControlFlowError::InvalidJumpForwardIfCondition)?;
23    if cond {
24        let dist = usize::try_from(dist).map_err(|_| StackError::IndexOutOfBounds)?;
25        if dist == 0 {
26            return Err(TotalControlFlowError::JumpedToSelf.into());
27        }
28        let pc = pc.checked_add(dist).ok_or(OpError::PcOverflow)?;
29        Ok(Some(ProgramControlFlow::Pc(pc)))
30    } else {
31        Ok(None)
32    }
33}
34
35pub fn halt_if(stack: &mut Stack) -> OpResult<Option<ProgramControlFlow>> {
36    let cond = stack.pop()?;
37    let cond = bool_from_word(cond).ok_or(TotalControlFlowError::InvalidHaltIfCondition)?;
38    if cond {
39        Ok(Some(ProgramControlFlow::Halt))
40    } else {
41        Ok(None)
42    }
43}
44
45/// Implementation of the `PanicIf` operation.
46pub fn panic_if(stack: &mut Stack) -> OpResult<()> {
47    let cond = stack.pop()?;
48    let cond = bool_from_word(cond).ok_or(TotalControlFlowError::InvalidPanicIfCondition)?;
49    if cond {
50        let stack = stack.iter().copied().collect();
51        Err(TotalControlFlowError::Panic(stack).into())
52    } else {
53        Ok(())
54    }
55}
essential_constraint_vm/total_control_flow.rs

essential_constraint_vm/
total_control_flow.rs
