Module memchr

Fast byte search primitives with SIMD acceleration.

• Crate ::memchr.
• docs.rs
• crates.io
• GitHub

memchr provides optimized routines for searching bytes in slices, using SIMD acceleration on supported architectures. It is significantly faster than naive byte-by-byte searching, often by an order of magnitude for larger inputs.

The primary functions are memchr for finding a single byte, memchr2 and memchr3 for finding one of 2-3 bytes, and the memmem module for substring search.

This crate is a foundational building block used by higher-level crates like regex.

Examples

Finding a single byte:

use memchr::memchr;

let haystack = b"hello world";
let needle = b'o';

assert_eq!(memchr(needle, haystack), Some(4));

Finding any of multiple bytes:

use memchr::memchr2;

let haystack = b"hello world";
// Find the first 'l' or 'w'
assert_eq!(memchr2(b'l', b'w', haystack), Some(2));

Substring search with the memmem module:

use memchr::memmem;

let haystack = b"the quick brown fox";
let needle = b"quick";

let finder = memmem::Finder::new(needle);
assert_eq!(finder.find(haystack), Some(4));

Finding all occurrences:

use memchr::memchr_iter;

let haystack = b"hello";
let positions: Vec<_> = memchr_iter(b'l', haystack).collect();
assert_eq!(positions, vec![2, 3]);