Struct LengthConstraint 

pub struct LengthConstraint { /* private fields */ }

A constraint that enforces hard minimum and maximum token-count limits.

• While count < min_len: if a stop_token is configured it is excluded from the mask (cannot stop early).
• While count >= max_len: if a stop_token is configured only that token is allowed; otherwise an all-false mask is returned, signalling the caller to halt generation externally.
• Between min_len and max_len: all tokens are allowed (None).

Completion is defined as either reaching max_len OR generating min_len or more tokens followed by the stop_token.

Example

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

// Must generate at least 2 tokens, stop token is 1 (EOS), max 10.
let mut c = LengthConstraint::new(2, 10, Some(1));
// Before min_len: stop_token excluded
let mask = c.allowed_tokens(&[], 4).unwrap();
assert!(!mask[1]);  // stop token blocked
assert!(mask[0]);   // other tokens allowed

Implementations

impl LengthConstraint

pub fn new(min_len: usize, max_len: usize, stop_token: Option<u32>) -> Self

Create a new LengthConstraint.

min_len must be <= max_len.

pub fn count(&self) -> usize

Current token count.

Trait Implementations

impl TokenConstraint for LengthConstraint

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

Commits token, updating count and stop_seen. Always returns true.

fn is_complete(&self) -> bool

Returns true when at least min_len tokens have been generated AND either the stop_token was seen or max_len has been reached.

fn reset(&mut self)

Reset to initial state.

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

Given the tokens generated so far, return a bitmask of allowed next tokens.

fn name(&self) -> &str

Human-readable name for debugging and logging.