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// This file must stay in sync with encoding.csc.
use crate::bytecode::{Arg, Local, Op};
use crate::data::Value;
use std::io;
use std::io::Read;
fn read_const<T: Read>(prog: &mut T) -> Result<Value, String> {
let mut buf = [0; 8];
match prog.read_exact(&mut buf) {
Ok(()) => (),
Err(e) => {
return Err(format!("error reading input: {}", e));
}
};
Ok(Value(u64::from_le_bytes(buf)))
}
fn read_local<T: Read>(prog: &mut T) -> Result<Local, String> {
let mut buf = [0; 1];
match prog.read_exact(&mut buf) {
Ok(()) => (),
Err(e) => {
return Err(format!("error reading input: {}", e));
}
};
Ok(Local(buf[0]))
}
fn read_arg<T: Read>(prog: &mut T, is_const: bool) -> Result<Arg, String> {
if is_const {
let c = read_const(prog)?;
return Ok(Arg::Const(c));
}
let l = read_local(prog)?;
Ok(Arg::L(l))
}
fn op_decoding<T: Read>(prog: &mut T) -> Result<Option<Op>, String> {
let mut buf = [0; 1];
match prog.read_exact(&mut buf) {
Ok(()) => (),
Err(e) if e.kind() == io::ErrorKind::UnexpectedEof => {
return Ok(None);
}
Err(e) => {
return Err(format!("error reading input: {}", e));
}
};
let tag = buf[0] >> 2;
let arg1_const = buf[0] & 2 != 0;
let arg2_const = buf[0] & 1 != 0;
let op = match tag {
// Note: arguments are evaluated left to right.
0 => Op::Mov(read_local(prog)?, read_arg(prog, arg1_const)?),
1 => Op::JmpIf(read_arg(prog, arg1_const)?, read_arg(prog, arg2_const)?),
2 => Op::Jmp(read_arg(prog, arg1_const)?),
3 => Op::Alloc(read_local(prog)?, read_arg(prog, arg1_const)?),
4 => Op::Peek(
read_local(prog)?,
read_arg(prog, arg1_const)?,
read_arg(prog, arg2_const)?,
),
5 => Op::Poke(
read_arg(prog, arg1_const)?,
read_arg(prog, false)?,
read_arg(prog, arg2_const)?,
),
6 => Op::Add(
read_local(prog)?,
read_arg(prog, arg1_const)?,
read_arg(prog, arg2_const)?,
),
7 => Op::Sub(
read_local(prog)?,
read_arg(prog, arg1_const)?,
read_arg(prog, arg2_const)?,
),
8 => Op::Mul(
read_local(prog)?,
read_arg(prog, arg1_const)?,
read_arg(prog, arg2_const)?,
),
9 => Op::Div(
read_local(prog)?,
read_arg(prog, arg1_const)?,
read_arg(prog, arg2_const)?,
),
10 => Op::Mod(
read_local(prog)?,
read_arg(prog, arg1_const)?,
read_arg(prog, arg2_const)?,
),
11 => Op::PeekByte(
read_local(prog)?,
read_arg(prog, arg1_const)?,
read_arg(prog, arg2_const)?,
),
12 => Op::PokeByte(
read_arg(prog, arg1_const)?,
read_arg(prog, false)?,
read_arg(prog, arg2_const)?,
),
13 => Op::Exit(read_arg(prog, arg1_const)?),
14 => Op::AllocBytevector(read_local(prog)?, read_arg(prog, arg1_const)?),
_ => {
return Err(String::from("invalid opcode"));
}
};
Ok(Some(op))
}
pub fn decode<T: Read>(prog: &mut T) -> Result<Vec<Op>, String> {
let mut out = Vec::new();
loop {
match op_decoding(prog)? {
Some(op) => {
out.push(op);
}
None => {
return Ok(out);
}
}
}
}
mod tests {
use super::*;
use Arg::*;
use Op::*;
#[test]
fn decode_mov_const() {
assert_eq!(
Ok(vec![Mov(Local(0), Const(Value::from_int(10)))]),
decode(&mut vec![0x2, 0, 0x15, 0, 0, 0, 0, 0, 0, 0].as_slice())
);
}
#[test]
fn decode_mov_local() {
assert_eq!(
Ok(vec![Mov(Local(0), L(Local(1)))]),
decode(&mut vec![0, 0, 1].as_slice()),
);
}
#[test]
fn decode_jmpif() {
assert_eq!(
Ok(vec![JmpIf(L(Local(0)), L(Local(1)))]),
decode(&mut vec![4, 0, 1].as_slice())
);
}
#[test]
fn decode_jmp() {
assert_eq!(
Ok(vec![Jmp(L(Local(0)))]),
decode(&mut vec![8, 0].as_slice())
);
}
#[test]
fn decode_alloc() {
assert_eq!(
Ok(vec![Alloc(Local(0), L(Local(1)))]),
decode(&mut vec![12, 0, 1].as_slice())
);
}
}
|
