essential_vm/
total_control_flow.rs

1use essential_types::convert::bool_from_word;
2
3use crate::{
4    error::{OpSyncError, OpSyncResult, StackError, TotalControlFlowError},
5    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_if(stack: &mut Stack, pc: usize) -> OpSyncResult<Option<ProgramControlFlow>> {
21    let [dist, cond] = stack.pop2()?;
22    let cond = bool_from_word(cond).ok_or(TotalControlFlowError::InvalidJumpForwardIfCondition)?;
23    if cond {
24        let neg = dist < 0;
25        let dist = usize::try_from(dist.abs()).map_err(|_| StackError::IndexOutOfBounds)?;
26        if dist == 0 {
27            return Err(TotalControlFlowError::JumpedToSelf.into());
28        }
29        if neg {
30            let pc = pc.checked_sub(dist).ok_or(OpSyncError::PcOverflow)?;
31            Ok(Some(ProgramControlFlow::Pc(pc)))
32        } else {
33            let pc = pc.checked_add(dist).ok_or(OpSyncError::PcOverflow)?;
34            Ok(Some(ProgramControlFlow::Pc(pc)))
35        }
36    } else {
37        Ok(None)
38    }
39}
40
41pub fn halt_if(stack: &mut Stack) -> OpSyncResult<Option<ProgramControlFlow>> {
42    let cond = stack.pop()?;
43    let cond = bool_from_word(cond).ok_or(TotalControlFlowError::InvalidHaltIfCondition)?;
44    if cond {
45        Ok(Some(ProgramControlFlow::Halt))
46    } else {
47        Ok(None)
48    }
49}
50
51/// Implementation of the `PanicIf` operation.
52pub fn panic_if(stack: &mut Stack) -> OpSyncResult<()> {
53    let cond = stack.pop()?;
54    let cond = bool_from_word(cond).ok_or(TotalControlFlowError::InvalidPanicIfCondition)?;
55    if cond {
56        let stack = stack.iter().copied().collect();
57        Err(TotalControlFlowError::Panic(stack).into())
58    } else {
59        Ok(())
60    }
61}
essential_vm/total_control_flow.rs

essential_vm/
total_control_flow.rs
