1memchr 2====== 3The `memchr` crate provides heavily optimized routines for searching bytes. 4 5[![Build status](https://api.travis-ci.org/BurntSushi/rust-memchr.png)](https://travis-ci.org/BurntSushi/rust-memchr) 6[![Build status](https://ci.appveyor.com/api/projects/status/8i9484t8l4w7uql0/branch/master?svg=true)](https://ci.appveyor.com/project/BurntSushi/rust-memchr/branch/master) 7[![](http://meritbadge.herokuapp.com/memchr)](https://crates.io/crates/memchr) 8 9Dual-licensed under MIT or the [UNLICENSE](http://unlicense.org). 10 11 12### Documentation 13 14[https://docs.rs/memchr](https://docs.rs/memchr) 15 16 17### Overview 18 19The `memchr` function is traditionally provided by libc, however, the 20performance of `memchr` can vary significantly depending on the specific 21implementation of libc that is used. They can range from manually tuned 22Assembly implementations (like that found in GNU's libc) all the way to 23non-vectorized C implementations (like that found in MUSL). 24 25To smooth out the differences between implementations of libc, at least 26on `x86_64` for Rust 1.27+, this crate provides its own implementation of 27`memchr` that should perform competitively with the one found in GNU's libc. 28The implementation is in pure Rust and has no dependency on a C compiler or an 29Assembler. 30 31Additionally, GNU libc also provides an extension, `memrchr`. This crate 32provides its own implementation of `memrchr` as well, on top of `memchr2`, 33`memchr3`, `memrchr2` and `memrchr3`. The difference between `memchr` and 34`memchr2` is that that `memchr2` permits finding all occurrences of two bytes 35instead of one. Similarly for `memchr3`. 36 37### Compiling without the standard library 38 39memchr links to the standard library by default, but you can disable the 40`use_std` feature if you want to use it in a `#![no_std]` crate: 41 42```toml 43[dependencies] 44memchr = { version = "2", default-features = false } 45``` 46 47On x86 platforms, when the `use_std` feature is disabled, the SSE2 48implementation of memchr will be used in compilers that support it. When 49`use_std` is enabled, the AVX implementation of memchr will be used if the CPU 50is determined to support it at runtime. 51 52### Using libc 53 54`memchr` is a routine that is part of libc, although this crate does not use 55libc by default. Instead, it uses its own routines, which are either vectorized 56or generic fallback routines. In general, these should be competitive with 57what's in libc, although this has not been tested for all architectures. If 58using `memchr` from libc is desirable and a vectorized routine is not otherwise 59available in this crate, then enabling the `libc` feature will use libc's 60version of `memchr`. 61 62The rest of the functions in this crate, e.g., `memchr2` or `memrchr3`, are not 63a standard part of libc, so they will always use the implementations in this 64crate. One exception to this is `memrchr`, which is an extension commonly found 65on Linux. On Linux, `memrchr` is used in precisely the same scenario as 66`memchr`, as described above. 67