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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 codemap::CodeMap;
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();
}
}
pub fn disassemble_op<W: Write>(
tw: &mut W,
codemap: &CodeMap,
chunk: &Chunk,
width: usize,
idx: CodeIdx,
) {
let _ = write!(tw, "{:#width$x}\t ", idx.0, width = width);
// Print continuation character if the previous operation was at
// the same line, otherwise print the line.
let line = chunk.get_line(codemap, idx);
if idx.0 > 0 && chunk.get_line(codemap, CodeIdx(idx.0 - 1)) == line {
write!(tw, " |\t").unwrap();
} else {
write!(tw, "{:4}\t", line).unwrap();
}
let _ = match chunk[idx] {
OpCode::OpConstant(idx) => writeln!(tw, "OpConstant({}@{})", chunk[idx], idx.0),
op => writeln!(tw, "{:?}", op),
};
}
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