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use crate::heap;
use crate::value::Value;
use std::error::Error;
#[derive(Debug, Clone, Copy)]
pub enum Arg {
Local(u8),
Const(Value),
}
#[derive(Debug, Clone, Copy)]
pub struct Alloc {
pub out: u8,
pub size: Arg,
}
#[derive(Debug, Clone, Copy)]
pub struct Poke {
pub offset: usize,
pub ptr: u8,
pub val: Arg,
}
#[derive(Debug, Clone, Copy)]
pub struct Peek {
pub out: u8,
pub offset: usize,
pub val: Arg,
}
#[derive(Debug, Clone, Copy)]
pub struct Shuf {
pub out: u8,
pub val: Arg,
}
#[derive(Debug, Clone, Copy)]
pub struct Exit {
pub val: Arg,
}
#[derive(Debug, Clone, Copy)]
pub enum Op {
Alloc(Alloc),
Call,
Poke(Poke),
Peek(Peek),
Shuf(Shuf),
Exit(Exit),
}
struct Reader<'a> {
data: &'a [u8],
n: usize,
}
impl Reader<'_> {
fn advance(&mut self, size: usize) {
self.data = &self.data[size..];
self.n += size;
}
fn parse_byte(&mut self) -> Result<u8, Box<dyn Error>> {
if self.data.is_empty() {
return Err(Box::from("read byte: no data"));
}
let res = self.data[0];
self.advance(1);
Ok(res)
}
fn parse_local(&mut self) -> Result<u8, Box<dyn Error>> {
if self.data.is_empty() {
return Err(Box::from("local: no data"));
}
let res = self.data[0];
if usize::from(res) >= heap::NUM_LOCALS {
return Err(Box::from(format!("invalid local (out of range): {}", res)));
}
self.advance(1);
Ok(res)
}
fn parse_value(&mut self) -> Result<Value, Box<dyn Error>> {
if self.data.len() < 8 {
return Err(Box::from("value: no data"));
}
let mut res = [0; 8];
res.copy_from_slice(&self.data[..8]);
self.advance(8);
Ok(Value(u64::from_le_bytes(res)))
}
fn parse_arg(&mut self, is_const: bool) -> Result<Arg, Box<dyn Error>> {
if is_const {
Ok(Arg::Const(self.parse_value()?))
} else {
Ok(Arg::Local(self.parse_local()?))
}
}
}
impl Op {
pub fn parse(data: &[u8]) -> Result<(usize, Op), Box<dyn Error>> {
let mut r = Reader { data, n: 0 };
let code_byte = r.parse_byte()?;
let code = code_byte >> 2;
let arg1_const = code_byte & 2 != 0;
// let arg2_const = code_byte & 1 != 0;
let op = match code {
1 => {
let out = r.parse_local()?;
let size = r.parse_arg(arg1_const)?;
Op::Alloc(Alloc { out, size })
}
2 => Op::Call,
3 => {
let Some(ioffset) = r.parse_value()?.to_int() else {
return Err(Box::from("invalid offset"));
};
let offset = usize::try_from(ioffset)?;
let ptr = r.parse_local()?;
let val = r.parse_arg(arg1_const)?;
Op::Poke(Poke { offset, ptr, val })
}
4 => {
let out = r.parse_local()?;
let Some(ioffset) = r.parse_value()?.to_int() else {
return Err(Box::from("invalid offset"));
};
let offset = usize::try_from(ioffset)?;
let val = r.parse_arg(arg1_const)?;
Op::Peek(Peek { out, offset, val })
}
5 => {
let out = r.parse_local()?;
let val = r.parse_arg(arg1_const)?;
Op::Shuf(Shuf { out, val })
}
6 => {
let val = r.parse_arg(arg1_const)?;
Op::Exit(Exit { val })
}
_ => {
return Err(Box::from(format!("invalid code {}", code)));
}
};
Ok((r.n, op))
}
}
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