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use super::chunk;
use super::errors::*;
use super::opcode::OpCode;
use super::value::Value;
pub struct VM {
chunk: chunk::Chunk,
// TODO(tazjin): Accessing array elements constantly is not ideal,
// lets see if something clever can be done with iterators.
ip: usize,
stack: Vec<Value>,
}
impl VM {
fn push(&mut self, value: Value) {
self.stack.push(value)
}
fn pop(&mut self) -> Value {
self.stack.pop().expect("fatal error: stack empty!")
}
}
macro_rules! binary_op {
( $vm:ident, $op:tt ) => {{
let a = $vm.pop();
let b = $vm.pop();
$vm.push(a $op b);
}}
}
impl VM {
fn run(&mut self) -> LoxResult<Value> {
loop {
let op = &self.chunk.code[self.ip];
#[cfg(feature = "disassemble")]
chunk::disassemble_instruction(&self.chunk, self.ip);
self.ip += 1;
match op {
OpCode::OpReturn => return Ok(self.pop()),
OpCode::OpConstant(idx) => {
let c = *self.chunk.constant(*idx);
self.push(c);
}
OpCode::OpNegate => {
let v = self.pop();
self.push(-v)
}
OpCode::OpAdd => binary_op!(self, +),
OpCode::OpSubtract => binary_op!(self, -),
OpCode::OpMultiply => binary_op!(self, *),
OpCode::OpDivide => binary_op!(self, /),
}
}
}
}
pub fn interpret(chunk: chunk::Chunk) -> LoxResult<Value> {
let mut vm = VM {
chunk,
ip: 0,
stack: vec![],
};
vm.run()
}
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