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use std::collections::HashMap;
use std::ops::Index;
#[derive(Clone, Debug, PartialEq)]
pub enum OpCode {
Num(i32),
Str(usize, usize),
WordI(usize),
Word(&'static str),
Add,
Sub,
Ret,
}
#[derive(Debug)]
pub(super) struct ByteCode(pub(super) Vec<OpCode>);
impl ByteCode {
pub fn len(&self) -> usize {
self.0.len()
}
}
impl Index<usize> for ByteCode {
type Output = OpCode;
fn index(&self, index: usize) -> &Self::Output {
&self.0[index]
}
}
#[derive(Debug, Copy, Clone, PartialEq)]
pub(super) struct InstructionPointer(pub(super) usize);
#[derive(Debug)]
pub(super) struct DataStack(pub(super) Vec<i32>);
#[derive(Debug)]
pub(super) struct CallStack(pub(super) Vec<InstructionPointer>);
#[derive(Debug)]
pub(super) struct WordList(pub(super) HashMap<&'static str, InstructionPointer>);
#[derive(Debug)]
pub(super) struct WordCatalog<'a>(pub(super) HashMap<&'a str, usize>);
#[derive(Debug)]
pub struct Interp {
stack: DataStack,
callstack: CallStack,
wordlist: WordList,
bytecode: ByteCode,
ip: InstructionPointer,
}
#[derive(Debug)]
pub enum RuntimeError {
StackUnderflow,
UndefinedWord,
}
impl Interp {
pub fn new() -> Self {
Self {
stack: DataStack(Vec::new()),
callstack: CallStack(Vec::new()),
wordlist: WordList(HashMap::new()),
bytecode: ByteCode(Vec::new()),
ip: InstructionPointer(0),
}
}
pub fn tick(&mut self) -> Result<(), RuntimeError> {
match self.bytecode[self.ip.0] {
OpCode::Num(n) => self.stack.0.push(n),
OpCode::Str(start, end) => eprintln!("got str: {} to {}", start, end),
OpCode::Add => {
let n1 = self.stack.0.pop().ok_or(RuntimeError::StackUnderflow)?;
let n2 = self.stack.0.pop().ok_or(RuntimeError::StackUnderflow)?;
self.stack.0.push(n2 + n1);
},
OpCode::Sub => {
let n1 = self.stack.0.pop().ok_or(RuntimeError::StackUnderflow)?;
let n2 = self.stack.0.pop().ok_or(RuntimeError::StackUnderflow)?;
self.stack.0.push(n2 - n1);
},
OpCode::Ret => {
let ip = self.callstack.0.pop().ok_or(RuntimeError::StackUnderflow)?;
self.ip = ip;
},
OpCode::Word(w) => {
let ip = self.wordlist.0.get(w).ok_or(RuntimeError::UndefinedWord)?;
self.callstack.0.push(self.ip);
self.ip.0 = ip.0 - 1; // we auto-increment at the end
},
OpCode::WordI(i) => {
eprintln!("should jump to word based on index {}", i);
}
}
self.ip.0 += 1;
Ok(())
}
}
#[cfg(test)]
mod tests {
use super::*;
use super::OpCode;
#[test]
fn simple_ticks() -> Result<(), RuntimeError> {
let mut interp = Interp::new();
interp.bytecode = ByteCode(vec![OpCode::Num(2), OpCode::Num(3), OpCode::Add]);
interp.tick()?;
assert_eq!(interp.ip.0, 1);
assert_eq!(interp.stack.0.len(), 1);
assert_eq!(interp.stack.0[0], 2, "first argument");
interp.tick()?;
assert_eq!(interp.ip.0, 2);
assert_eq!(interp.stack.0.len(), 2);
assert_eq!(interp.stack.0[1], 3, "second argument");
interp.tick()?;
assert_eq!(interp.ip.0, 3);
assert_eq!(interp.stack.0.len(), 1);
assert_eq!(interp.stack.0[0], 5, "result of addition");
Ok(())
}
#[test]
fn custom_word() -> Result<(), RuntimeError> {
let mut interp = Interp::new();
interp.bytecode = ByteCode(vec![
OpCode::Num(2), OpCode::Num(3), OpCode::Word("sub"), OpCode::Num(-2), OpCode::Add,
// "sub" definition
OpCode::Sub, OpCode::Ret,
]);
// 5 is offset of w
interp.wordlist.0.insert("sub", InstructionPointer(5));
interp.tick()?;
assert_eq!(interp.ip.0, 1);
assert_eq!(interp.stack.0.len(), 1);
assert_eq!(interp.stack.0[0], 2, "first argument");
interp.tick()?;
assert_eq!(interp.ip.0, 2);
assert_eq!(interp.stack.0.len(), 2);
assert_eq!(interp.stack.0[1], 3, "second argument");
interp.tick()?; // call sub
assert_eq!(interp.ip.0, 5);
assert_eq!(interp.stack.0.len(), 2);
interp.tick()?; // -
assert_eq!(interp.ip.0, 6);
assert_eq!(interp.stack.0.len(), 1);
interp.tick()?; // ret
assert_eq!(interp.ip.0, 3);
assert_eq!(interp.stack.0.len(), 1);
assert_eq!(interp.stack.0[0], -1, "result of sub word");
interp.tick()?; // 2
assert_eq!(interp.ip.0, 4);
assert_eq!(interp.stack.0.len(), 2);
assert_eq!(interp.stack.0[1], -2, "post sub arg");
interp.tick()?; // -
assert_eq!(interp.ip.0, 5);
assert_eq!(interp.stack.0.len(), 1);
assert_eq!(interp.stack.0[0], -3, "add opcode result");
Ok(())
}
}
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