Dual-licensed under MIT or the UNLICENSE.
Add this to your Cargo.toml
:
[dependencies] aho-corasick = "0.7"
and this to your crate root (if you're using Rust 2015):
extern crate aho_corasick;
This example shows how to search for occurrences of multiple patterns simultaneously. Each match includes the pattern that matched along with the byte offsets of the match.
use aho_corasick::AhoCorasick; let patterns = &["apple", "maple", "Snapple"]; let haystack = "Nobody likes maple in their apple flavored Snapple."; let ac = AhoCorasick::new(patterns); let mut matches = vec![]; for mat in ac.find_iter(haystack) { matches.push((mat.pattern(), mat.start(), mat.end())); } assert_eq!(matches, vec![ (1, 13, 18), (0, 28, 33), (2, 43, 50), ]);
This is like the previous example, but matches Snapple
case insensitively using AhoCorasickBuilder
:
use aho_corasick::AhoCorasickBuilder; let patterns = &["apple", "maple", "snapple"]; let haystack = "Nobody likes maple in their apple flavored Snapple."; let ac = AhoCorasickBuilder::new() .ascii_case_insensitive(true) .build(patterns); let mut matches = vec![]; for mat in ac.find_iter(haystack) { matches.push((mat.pattern(), mat.start(), mat.end())); } assert_eq!(matches, vec![ (1, 13, 18), (0, 28, 33), (2, 43, 50), ]);
This example shows how to execute a search and replace on a stream without loading the entire stream into memory first.
use aho_corasick::AhoCorasick; let patterns = &["fox", "brown", "quick"]; let replace_with = &["sloth", "grey", "slow"]; // In a real example, these might be `std::fs::File`s instead. All you need to // do is supply a pair of `std::io::Read` and `std::io::Write` implementations. let rdr = "The quick brown fox."; let mut wtr = vec![]; let ac = AhoCorasick::new(patterns); ac.stream_replace_all(rdr.as_bytes(), &mut wtr, replace_with)?; assert_eq!(b"The slow grey sloth.".to_vec(), wtr);
In the textbook description of Aho-Corasick, its formulation is typically structured such that it reports all possible matches, even when they overlap with another. In many cases, overlapping matches may not be desired, such as the case of finding all successive non-overlapping matches like you might with a standard regular expression.
Unfortunately the “obvious” way to modify the Aho-Corasick algorithm to do this doesn't always work in the expected way, since it will report matches as soon as they are seen. For example, consider matching the regex Samwise|Sam
against the text Samwise
. Most regex engines (that are Perl-like, or non-POSIX) will report Samwise
as a match, but the standard Aho-Corasick algorithm modified for reporting non-overlapping matches will report Sam
.
A novel contribution of this library is the ability to change the match semantics of Aho-Corasick (without additional search time overhead) such that Samwise
is reported instead. For example, here's the standard approach:
use aho_corasick::AhoCorasick; let patterns = &["Samwise", "Sam"]; let haystack = "Samwise"; let ac = AhoCorasick::new(patterns); let mat = ac.find(haystack).expect("should have a match"); assert_eq!("Sam", &haystack[mat.start()..mat.end()]);
And now here's the leftmost-first version, which matches how a Perl-like regex will work:
use aho_corasick::{AhoCorasickBuilder, MatchKind}; let patterns = &["Samwise", "Sam"]; let haystack = "Samwise"; let ac = AhoCorasickBuilder::new() .match_kind(MatchKind::LeftmostFirst) .build(patterns); let mat = ac.find(haystack).expect("should have a match"); assert_eq!("Samwise", &haystack[mat.start()..mat.end()]);
In addition to leftmost-first semantics, this library also supports leftmost-longest semantics, which match the POSIX behavior of a regular expression alternation. See MatchKind
in the docs for more details.
This crate's minimum supported rustc
version is 1.28.0
.
The current policy is that the minimum Rust version required to use this crate can be increased in minor version updates. For example, if crate 1.0
requires Rust 1.20.0, then crate 1.0.z
for all values of z
will also require Rust 1.20.0 or newer. However, crate 1.y
for y > 0
may require a newer minimum version of Rust.
In general, this crate will be conservative with respect to the minimum supported version of Rust.
Here are some plans for the future:
1.0
version of this crate some time in the next 6-12 months.