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check for backref cycles in cue

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This commit is contained in:
Jonathan Paprocki 2024-09-14 18:36:12 -04:00
parent d37c4d991f
commit 2124e5b575
1 changed files with 15 additions and 3 deletions
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18
rust/sword/src/serialization.rs
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@ -5,6 +5,7 @@ use crate::mem::NockStack;
use crate::noun::{Atom, Cell, DirectAtom, IndirectAtom, Noun, D};
use bitvec::prelude::{BitSlice, Lsb0};
use either::Either::{Left, Right};
use std::collections::HashSet;
crate::gdb!();
@ -100,6 +101,7 @@ pub fn cue_bitslice(stack: &mut NockStack, buffer: &BitSlice<u64, Lsb0>) -> Resu
let backref_map = MutHamt::<Noun>::new(stack);
let mut result = D(0);
let mut cursor = 0;
let mut in_progress = HashSet::new();
let stack_size = stack.size();
let input_size = buffer.len();
@ -118,12 +120,20 @@ pub fn cue_bitslice(stack: &mut NockStack, buffer: &BitSlice<u64, Lsb0>) -> Resu
// Capture the destination pointer and pop it off the stack
let dest_ptr: *mut Noun = *(stack.top::<*mut Noun>());
stack.pop::<*mut Noun>();
let current_backref = cursor as u64;
// 1 bit
if next_bit(&mut cursor, buffer) {
// 11 tag: backref
if next_bit(&mut cursor, buffer) {
let backref = rub_backref(&mut cursor, buffer)?;
let mut backref_noun =
Atom::new(stack, rub_backref(&mut cursor, buffer)?).as_noun();
Atom::new(stack, backref).as_noun();
in_progress.insert(current_backref);
if in_progress.contains(&backref) {
panic!("Cyclic structure detected during deserialization");
}
*dest_ptr = backref_map
.lookup(stack, &mut backref_noun)
.ok_or(Deterministic(Exit, D(0)))?;
@ -131,18 +141,20 @@ pub fn cue_bitslice(stack: &mut NockStack, buffer: &BitSlice<u64, Lsb0>) -> Resu
// 10 tag: cell
let (cell, cell_mem_ptr) = Cell::new_raw_mut(stack);
*dest_ptr = cell.as_noun();
let mut backref_atom = Atom::new(stack, (cursor - 2) as u64).as_noun();
let mut backref_atom = Atom::new(stack, (current_backref - 2) as u64).as_noun();
backref_map.insert(stack, &mut backref_atom, *dest_ptr);
*(stack.push()) = &mut (*cell_mem_ptr).tail;
*(stack.push()) = &mut (*cell_mem_ptr).head;
}
} else {
// 0 tag: atom
let backref: u64 = (cursor - 1) as u64;
let backref: u64 = (current_backref - 1) as u64;
*dest_ptr = rub_atom(stack, &mut cursor, buffer)?.as_noun();
let mut backref_atom = Atom::new(stack, backref).as_noun();
backref_map.insert(stack, &mut backref_atom, *dest_ptr);
}
in_progress.remove(&current_backref);
}
})
}