holey-bytes/lang/src/fuzz.rs
2024-10-27 13:57:00 +01:00

140 lines
3.6 KiB
Rust

use {
crate::{
lexer::TokenKind,
parser,
son::{Codegen, CodegenCtx},
},
alloc::string::String,
core::{fmt::Write, hash::BuildHasher, ops::Range},
};
#[derive(Default)]
struct Rand(pub u64);
impl Rand {
pub fn next(&mut self) -> u64 {
self.0 = crate::FnvBuildHasher::default().hash_one(self.0);
self.0
}
pub fn range(&mut self, min: u64, max: u64) -> u64 {
self.next() % (max - min) + min
}
fn bool(&mut self) -> bool {
self.next() % 2 == 0
}
}
#[derive(Default)]
struct FuncGen {
rand: Rand,
buf: String,
vars: u64,
}
impl FuncGen {
fn gen(&mut self, seed: u64) -> &str {
self.rand = Rand(seed);
self.buf.clear();
self.buf.push_str("main := fn(): void ");
self.block().unwrap();
&self.buf
}
fn block(&mut self) -> core::fmt::Result {
let prev_vars = self.vars;
self.buf.push('{');
for _ in 0..self.rand.range(1, 10) {
self.stmt()?;
}
self.buf.push('}');
self.vars = prev_vars;
Ok(())
}
fn stmt(&mut self) -> core::fmt::Result {
match self.rand.range(0, 100) {
0..4 => _ = self.block(),
4..10 => {
write!(self.buf, "var{} := ", self.vars)?;
self.expr()?;
self.vars += 1;
}
10..20 if self.vars != 0 => {
write!(self.buf, "var{} = ", self.rand.range(0, self.vars))?;
self.expr()?;
}
20..23 => {
self.buf.push_str("if ");
self.expr()?;
self.block()?;
if self.rand.bool() {
self.buf.push_str(" else ");
self.block()?;
}
}
_ => {
self.buf.push_str("return ");
self.expr()?;
}
}
self.buf.push(';');
Ok(())
}
fn expr(&mut self) -> core::fmt::Result {
match self.rand.range(0, 100) {
0..80 => {
write!(self.buf, "{}", self.rand.next())
}
80..90 if self.vars != 0 => {
write!(self.buf, "var{}", self.rand.range(0, self.vars))
}
80..100 => {
self.expr()?;
let ops = [
TokenKind::Add,
TokenKind::Sub,
TokenKind::Mul,
TokenKind::Div,
TokenKind::Shl,
TokenKind::Eq,
TokenKind::Ne,
TokenKind::Lt,
TokenKind::Gt,
TokenKind::Le,
TokenKind::Ge,
TokenKind::Band,
TokenKind::Bor,
TokenKind::Xor,
TokenKind::Mod,
TokenKind::Shr,
];
let op = ops[self.rand.range(0, ops.len() as u64) as usize];
write!(self.buf, " {op} ")?;
self.expr()
}
_ => unreachable!(),
}
}
}
pub fn fuzz(seed_range: Range<u64>) {
let mut gen = FuncGen::default();
let mut ctx = CodegenCtx::default();
for i in seed_range {
ctx.clear();
let src = gen.gen(i);
let parsed = parser::Ast::new("fuzz", src, &mut ctx.parser, &mut parser::no_loader);
assert!(ctx.parser.errors.get_mut().is_empty());
let mut cdg = Codegen::new(core::slice::from_ref(&parsed), &mut ctx);
cdg.generate(0);
}
}