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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 Tracer {
pub fn new() -> Self {
Tracer(TabWriter::new(std::io::stderr()))
}
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();
}
pub fn literal(&mut self, line: &str) {
let _ = write!(&mut self.0, "{}\n", line);
}
}
impl Drop for Tracer {
fn drop(&mut self) {
self.0.flush().ok();
}
}
fn disassemble_op(tw: &mut TabWriter<Stderr>, chunk: &Chunk, width: usize, offset: usize) {
write!(tw, "{:0width$}\t ", offset, width = width).ok();
let span = chunk.get_span(CodeIdx(offset));
if offset > 0 && chunk.get_span(CodeIdx(offset - 1)) == span {
write!(tw, " |\t").unwrap();
} else {
let loc = chunk.codemap.look_up_span(span);
write!(tw, "{:4}\t", loc.begin.line + 1).unwrap();
}
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();
let width = format!("{}", chunk.code.len()).len();
for (idx, _) in chunk.code.iter().enumerate() {
disassemble_op(&mut tw, chunk, width, idx);
}
tw.flush().ok();
}
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