1memchr 2====== 3The `memchr` crate provides heavily optimized routines for searching bytes. 4 5[![Build status](https://github.com/BurntSushi/rust-memchr/workflows/ci/badge.svg)](https://github.com/BurntSushi/rust-memchr/actions) 6[![](http://meritbadge.herokuapp.com/memchr)](https://crates.io/crates/memchr) 7 8Dual-licensed under MIT or the [UNLICENSE](http://unlicense.org). 9 10 11### Documentation 12 13[https://docs.rs/memchr](https://docs.rs/memchr) 14 15 16### Overview 17 18The `memchr` function is traditionally provided by libc, but its 19performance can vary significantly depending on the specific 20implementation of libc that is used. They can range from manually tuned 21Assembly implementations (like that found in GNU's libc) all the way to 22non-vectorized C implementations (like that found in MUSL). 23 24To smooth out the differences between implementations of libc, at least 25on `x86_64` for Rust 1.27+, this crate provides its own implementation of 26`memchr` that should perform competitively with the one found in GNU's libc. 27The implementation is in pure Rust and has no dependency on a C compiler or an 28Assembler. 29 30Additionally, GNU libc also provides an extension, `memrchr`. This crate 31provides its own implementation of `memrchr` as well, on top of `memchr2`, 32`memchr3`, `memrchr2` and `memrchr3`. The difference between `memchr` and 33`memchr2` is that `memchr2` permits finding all occurrences of two bytes 34instead of one. Similarly for `memchr3`. 35 36### Compiling without the standard library 37 38memchr links to the standard library by default, but you can disable the 39`std` feature if you want to use it in a `#![no_std]` crate: 40 41```toml 42[dependencies] 43memchr = { version = "2", default-features = false } 44``` 45 46On x86 platforms, when the `std` feature is disabled, the SSE2 47implementation of memchr will be used in compilers that support it. When 48`std` is enabled, the AVX implementation of memchr will be used if the CPU 49is determined to support it at runtime. 50 51### Using libc 52 53`memchr` is a routine that is part of libc, although this crate does not use 54libc by default. Instead, it uses its own routines, which are either vectorized 55or generic fallback routines. In general, these should be competitive with 56what's in libc, although this has not been tested for all architectures. If 57using `memchr` from libc is desirable and a vectorized routine is not otherwise 58available in this crate, then enabling the `libc` feature will use libc's 59version of `memchr`. 60 61The rest of the functions in this crate, e.g., `memchr2` or `memrchr3`, are not 62a standard part of libc, so they will always use the implementations in this 63crate. One exception to this is `memrchr`, which is an extension commonly found 64on Linux. On Linux, `memrchr` is used in precisely the same scenario as 65`memchr`, as described above. 66 67 68### Minimum Rust version policy 69 70This crate's minimum supported `rustc` version is `1.28.0`. 71 72The current policy is that the minimum Rust version required to use this crate 73can be increased in minor version updates. For example, if `crate 1.0` requires 74Rust 1.20.0, then `crate 1.0.z` for all values of `z` will also require Rust 751.20.0 or newer. However, `crate 1.y` for `y > 0` may require a newer minimum 76version of Rust. 77 78In general, this crate will be conservative with respect to the minimum 79supported version of Rust. 80