//! Implements methods for disassembling and printing a representation
//! of compiled code, as well as tracing the runtime stack during
//! execution.
use std::io::{Stderr, Write};
use tabwriter::TabWriter;
use crate::chunk::Chunk;
use crate::opcode::OpCode;
use crate::value::Value;
/// Helper struct to trace runtime values and automatically flush the
/// output after the value is dropped (i.e. in both success and
/// failure exits from the VM).
pub struct Tracer(TabWriter<Stderr>);
impl Tracer {
pub fn new() -> Self {
let mut tw = TabWriter::new(std::io::stderr());
write!(&mut tw, "=== runtime trace ===\n").ok();
Tracer(tw)
}
pub fn trace(&mut self, op: &OpCode, ip: usize, stack: &[Value]) {
write!(&mut self.0, "{:04} {:?}\t[ ", ip, op).ok();
for val in stack {
write!(&mut self.0, "{} ", val).ok();
}
write!(&mut self.0, "]\n").ok();
}
}
impl Drop for Tracer {
fn drop(&mut self) {
self.0.flush().ok();
}
}
fn disassemble_op(tw: &mut TabWriter<Stderr>, chunk: &Chunk, offset: usize) {
let code_width = format!("{}", chunk.code.len()).len();
write!(tw, "{:0width$}\t ", width = code_width).ok();
match chunk.code[offset] {
OpCode::OpConstant(idx) => write!(tw, "OpConstant({})\n", chunk.constant(idx)).ok(),
op => write!(tw, "{:?}\n", op).ok(),
};
}
/// Disassemble a chunk of code, printing out the operations in a
/// reasonable, human-readable format.
pub fn disassemble_chunk(chunk: &Chunk) {
let mut tw = TabWriter::new(std::io::stderr());
write!(
&mut tw,
"=== compiled bytecode ({} operations) ===\n",
chunk.code.len()
)
.ok();
for (idx, _) in chunk.code.iter().enumerate() {
disassemble_op(&mut tw, chunk, idx);
}
tw.flush().ok();
}
