Crate xgrammar

Expand description

Safe, idiomatic Rust bindings for the xgrammar C++ library for constrained decoding of large language models.

This crate wraps xgrammar’s grammar compilation and token-level matching so you can drive constrained generation (JSON schema, regex, BNF, structural tags) from Rust while retaining the performance of the upstream C++ implementation.

§Highlights

Grammar, GrammarCompiler, CompiledGrammar, TokenizerInfo — compile grammars (BNF, JSON schema, regex, structural tags) against a tokenizer.
GrammarMatcher — token-by-token constrained decoding, including GrammarMatcher::is_completed (root-rule match without stop token) and GrammarMatcher::fork for speculative / branching decoding.
BatchGrammarMatcher — batched helpers over a slice of matchers: BatchGrammarMatcher::batch_fill_next_token_bitmask is parallel and thread-pool-backed; batch_accept_token / batch_accept_string / batch_rollback are sequential static helpers.

See each item’s documentation for usage details, including when a BatchGrammarMatcher instance is required vs when associated functions can be called directly.