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//! 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::{CodeIdx, 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 Default for Tracer {
fn default() -> Self {
Tracer(TabWriter::new(std::io::stderr()))
}
}
impl Tracer {
pub fn trace(&mut self, op: &OpCode, ip: usize, stack: &[Value]) {
let _ = write!(&mut self.0, "{:04} {:?}\t[ ", ip, op);
for val in stack {
let _ = write!(&mut self.0, "{} ", val);
}
let _ = writeln!(&mut self.0, "]");
}
pub fn literal(&mut self, line: &str) {
let _ = writeln!(&mut self.0, "{}", line);
}
}
impl Drop for Tracer {
fn drop(&mut self) {
let _ = self.0.flush();
}
}
fn disassemble_op(tw: &mut TabWriter<Stderr>, chunk: &Chunk, width: usize, offset: usize) {
let _ = write!(tw, "{:0width$}\t ", offset, width = width);
let line = chunk.get_line(CodeIdx(offset));
if offset > 0 && chunk.get_line(CodeIdx(offset - 1)) == line {
write!(tw, " |\t").unwrap();
} else {
write!(tw, "{:4}\t", line).unwrap();
}
let _ = match chunk.code[offset] {
OpCode::OpConstant(idx) => writeln!(tw, "OpConstant({})", chunk.constant(idx)),
op => writeln!(tw, "{:?}", op),
};
}
/// 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());
let _ = writeln!(
&mut tw,
"=== compiled bytecode ({} operations) ===",
chunk.code.len()
);
let width = format!("{}", chunk.code.len()).len();
for (idx, _) in chunk.code.iter().enumerate() {
disassemble_op(&mut tw, chunk, width, idx);
}
let _ = tw.flush();
}
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