Jetscii

A tiny library to efficiently search strings for substrings or sets of ASCII characters.

Examples

Searching for a set of ASCII characters

use jetscii::AsciiChars;
let mut search = AsciiChars::new();
search.push(b'-');
search.push(b':');
let part_number = "86-J52:rev1";
let parts: Vec<_> = part_number.split(search.with_fallback(|c| {
    c == b'-' || c == b':'
})).collect();
assert_eq!(&parts, &["86", "J52", "rev1"]);

Searching for a substring

use jetscii::Substring;
let colors: Vec<_> = "red, blue, green".split(Substring::new(", ")).collect();
assert_eq!(&colors, &["red", "blue", "green"]);

What's so special about this library?

We use a particular set of x86-64 SSE 4.2 instructions (PCMPESTRI and PCMPESTRM) to gain great speedups. This method stays fast even when searching for a character in a set of up to 16 choices.

When the PCMPxSTRx instructions are not available, we fall back to reasonably fast but universally-supported methods.

Benchmarks

Single character

Searching a 5MiB string of as with a single space at the end:

Method	Speed
`str.find(AsciiChars)`	5719 MB/s
`str.as_bytes().iter().position(	&v
`str.find(	c
`str.find(' ')`	1085 MB/s
`str.find(&[' '][..])`	602 MB/s
`str.find(" ")`	293 MB/s

Set of characters

Searching a 5MiB string of as with a single ampersand at the end:

Method	Speed
`str.find(AsciiChars)`	5688 MB/s
`str.as_bytes().iter().position(	&v
`str.find(	c
`str.find(&['<', '>', '&'][..])`	361 MB/s

Substrings

Method	Speed
`str.find(Substring::new("xyzzy"))`	5017 MB/s
str.find("xyzzy"	3837 MB/s

Contributing

Fork it ( https://github.com/shepmaster/jetscii/fork )
Create your feature branch (git checkout -b my-new-feature)
Add a failing test.
Add code to pass the test.
Commit your changes (git commit -am 'Add some feature')
Ensure tests pass.
Push to the branch (git push origin my-new-feature)
Create a new Pull Request

jetscii 0.3.0