The rust-memchr crate uses libc's memchr if it's available and known to be fast. Otherwise, it falls back to a pure Rust implementation (written by bluss, not me).
> Is burntsushi's Rust implementation of memchr notably slower than libc's?
Not as far as I know. A lot of this benchmarksgame code has evolved slowly over time and hasn't been cleaned up yet to use "modern" crates and language features.
