//! # Performance //! //! ## Runtime Performance //! //! See also the general Rust [Performance Book](https://nnethercote.github.io/perf-book/) //! //! Tips //! - Try `cargo add winnow -F simd`. For some it offers significant performance improvements //! - When enough cases of an [`alt`] have unique prefixes, prefer [`dispatch`] //! - When parsing text, try to parse as bytes (`u8`) rather than `char`s ([`BStr`] can make //! debugging easier) //! - Find simplified subsets of the grammar to parse, falling back to the full grammar when it //! doesn't work. For example, when parsing json strings, parse them without support for escapes, //! falling back to escape support if it fails. //! - Watch for large return types. A surprising place these can show up is when chaining parsers //! with a tuple. //! //! ## Build-time Performance //! //! Returning complex types as `impl Trait` can negatively impact build times. This can hit in //! surprising cases like: //! ```rust //! # use winnow::prelude::*; //! fn foo() -> impl Parser //! # where //! # I: winnow::stream::Stream, //! # I: winnow::stream::StreamIsPartial, //! # E: winnow::error::ParserError, //! { //! // ...some chained combinators... //! # winnow::token::any //! } //! ``` //! //! Instead, wrap the combinators in a closure to simplify the type: //! ```rust //! # use winnow::prelude::*; //! fn foo() -> impl Parser //! # where //! # I: winnow::stream::Stream, //! # I: winnow::stream::StreamIsPartial, //! # E: winnow::error::ParserError, //! { //! move |input: &mut I| { //! // ...some chained combinators... //! # winnow::token::any //! .parse_next(input) //! } //! } //! ``` #![allow(unused_imports)] use crate::combinator::alt; use crate::combinator::dispatch; use crate::stream::BStr;