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use crate::vm::instr::Instr;
pub fn run(instrs: &[Instr], s: &[u8]) -> bool {
let mut vm = Vm::new(instrs, s);
vm.run()
}
struct Thread {
pc: usize, // program counter
sp: usize, // string pointer
}
impl Thread {
fn new(pc: usize, sp: usize) -> Self {
Self { pc, sp }
}
}
struct Vm<'instr, 'input> {
instrs: &'instr [Instr],
string: &'input [u8],
thread_stack: Vec<Thread>,
}
impl<'instr, 'input> Vm<'instr, 'input> {
fn new(instrs: &'instr [Instr], string: &'input [u8]) -> Self {
let initial_thread = Thread::new(0, 0);
Self {
instrs,
string,
thread_stack: vec![initial_thread],
}
}
fn run(&mut self) -> bool {
while let Some(t) = self.thread_stack.pop() {
let mut pc = t.pc;
let mut sp = t.sp;
loop {
match self.instrs[pc] {
Instr::Char(expected) => {
if let Some(c) = self.string.get(sp) {
if *c == expected {
pc += 1;
sp += 1;
} else {
break;
}
} else {
break;
}
}
Instr::Match => {
return true;
}
Instr::Jmp(a) => {
pc = a;
}
Instr::Split(a, b) => {
self.thread_stack.push(Thread::new(b, sp));
pc = a;
}
}
}
}
false
}
}
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