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Diffstat (limited to 'third_party/rust/ryu/src/lib.rs')
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diff --git a/third_party/rust/ryu/src/lib.rs b/third_party/rust/ryu/src/lib.rs new file mode 100644 index 0000000000..8aecb51e5b --- /dev/null +++ b/third_party/rust/ryu/src/lib.rs @@ -0,0 +1,111 @@ +//! Pure Rust implementation of Ryū, an algorithm to quickly convert floating +//! point numbers to decimal strings. +//! +//! The PLDI'18 paper [*Ryū: fast float-to-string conversion*][paper] by Ulf +//! Adams includes a complete correctness proof of the algorithm. The paper is +//! available under the creative commons CC-BY-SA license. +//! +//! This Rust implementation is a line-by-line port of Ulf Adams' implementation +//! in C, [https://github.com/ulfjack/ryu][upstream]. +//! +//! [paper]: https://dl.acm.org/citation.cfm?id=3192369 +//! [upstream]: https://github.com/ulfjack/ryu +//! +//! # Example +//! +//! ```edition2018 +//! fn main() { +//! let mut buffer = ryu::Buffer::new(); +//! let printed = buffer.format(1.234); +//! assert_eq!(printed, "1.234"); +//! } +//! ``` +//! +//! ## Performance +//! +//! You can run upstream's benchmarks with: +//! +//! ```console +//! $ git clone https://github.com/ulfjack/ryu c-ryu +//! $ cd c-ryu +//! $ bazel run -c opt //ryu/benchmark +//! ``` +//! +//! And the same benchmark against our implementation with: +//! +//! ```console +//! $ git clone https://github.com/dtolnay/ryu rust-ryu +//! $ cd rust-ryu +//! $ cargo run --example upstream_benchmark --release +//! ``` +//! +//! These benchmarks measure the average time to print a 32-bit float and average +//! time to print a 64-bit float, where the inputs are distributed as uniform random +//! bit patterns 32 and 64 bits wide. +//! +//! The upstream C code, the unsafe direct Rust port, and the safe pretty Rust API +//! all perform the same, taking around 21 nanoseconds to format a 32-bit float and +//! 31 nanoseconds to format a 64-bit float. +//! +//! There is also a Rust-specific benchmark comparing this implementation to the +//! standard library which you can run with: +//! +//! ```console +//! $ cargo bench +//! ``` +//! +//! The benchmark shows Ryu approximately 4-10x faster than the standard library +//! across a range of f32 and f64 inputs. Measurements are in nanoseconds per +//! iteration; smaller is better. +//! +//! | type=f32 | 0.0 | 0.1234 | 2.718281828459045 | f32::MAX | +//! |:--------:|:----:|:------:|:-----------------:|:--------:| +//! | RYU | 3ns | 28ns | 23ns | 22ns | +//! | STD | 40ns | 106ns | 128ns | 110ns | +//! +//! | type=f64 | 0.0 | 0.1234 | 2.718281828459045 | f64::MAX | +//! |:--------:|:----:|:------:|:-----------------:|:--------:| +//! | RYU | 3ns | 50ns | 35ns | 32ns | +//! | STD | 39ns | 105ns | 128ns | 202ns | +//! +//! ## Formatting +//! +//! This library tends to produce more human-readable output than the standard +//! library's to\_string, which never uses scientific notation. Here are two +//! examples: +//! +//! - *ryu:* 1.23e40, *std:* 12300000000000000000000000000000000000000 +//! - *ryu:* 1.23e-40, *std:* 0.000000000000000000000000000000000000000123 +//! +//! Both libraries print short decimals such as 0.0000123 without scientific +//! notation. + +#![no_std] +#![doc(html_root_url = "https://docs.rs/ryu/1.0.2")] +#![cfg_attr(feature = "cargo-clippy", allow(renamed_and_removed_lints))] +#![cfg_attr( + feature = "cargo-clippy", + allow(cast_lossless, many_single_char_names, unreadable_literal,) +)] + +#[cfg(feature = "no-panic")] +extern crate no_panic; + +mod buffer; +mod common; +mod d2s; +#[cfg(not(feature = "small"))] +mod d2s_full_table; +mod d2s_intrinsics; +#[cfg(feature = "small")] +mod d2s_small_table; +mod digit_table; +mod f2s; +mod pretty; + +pub use buffer::{Buffer, Float}; + +/// Unsafe functions that mirror the API of the C implementation of Ryū. +pub mod raw { + pub use pretty::{format32, format64}; +} |