Struct AllowListConstraint 

pub struct AllowListConstraint { /* private fields */ }

A constraint that forces the generated token sequence to exactly match one of a finite set of allowed token-id sequences (e.g., multiple-choice answers).

At each step only the union of next tokens across all still-active candidates is permitted. A candidate becomes inactive the moment any token in the prefix fails to match. Generation is considered complete once the full token sequence of at least one candidate has been consumed.

Example

use oxibonsai_runtime::constrained_decoding::{AllowListConstraint, TokenConstraint};

// Two candidates: [10, 20] and [10, 30]
let mut c = AllowListConstraint::new(vec![vec![10, 20], vec![10, 30]]);
// First token: only 10 is allowed (shared prefix)
let mask = c.allowed_tokens(&[], 50).unwrap();
assert!(mask[10]);
assert!(!mask[20]);
assert!(!mask[30]);

Implementations

impl AllowListConstraint

pub fn new(candidates: Vec<Vec<u32>>) -> Self

Create a new AllowListConstraint from a list of allowed token sequences.

pub fn active_count(&self) -> usize

Returns the number of candidate sequences that are still active.

Trait Implementations

impl TokenConstraint for AllowListConstraint

fn allowed_tokens( &self, _generated: &[u32], vocab_size: usize, ) -> Option<Vec<bool>>

Returns a bitmask of tokens that are valid next tokens across all still-active candidates at the current position. Always returns Some (never unconstrained).

fn advance(&mut self, token: u32) -> bool

Commits token at the current position.

Any candidate where candidates[i][position] != token (or the candidate is already exhausted) is deactivated. Returns true when at least one candidate remains active or a candidate was just completed at this position.

fn is_complete(&self) -> bool

Returns true when the consumed token sequence fully matches at least one candidate, i.e. position == candidates[i].len() for some active i.

fn reset(&mut self)

Reset to initial state (all candidates active, position zero).

fn name(&self) -> &str

Human-readable name for debugging and logging.