cmp_ascii_lookup.rs

#![feature(test)]

const CHAR_DIGIT: u8 = 0x03;

#[rustfmt::skip]
static CHAR_LOOKUP_TABLE: [u8; 256] = [
    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, b' ', b' ', 0xFF, b' ', b' ', 0xFF, 0xFF, 0xFF, // 0x00 - 0x0F
    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 0x10 - 0x1F
    b' ', b'!', 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, b'(', b')', b'*', 0xFF, b',', 0xFF, b'.', 0xFF, // 0x20 - 0x2F
    0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0xFF, b';', b'<', b'=', b'>', 0xFF, // 0x30 - 0x3F
    0xFF, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, // 0x40 - 0x4F
    0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0xFF, 0xFF, 0xFF, 0xFF, 0x02, // 0x50 - 0x5F
    0xFF, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, // 0x60 - 0x6F
    0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 0x70 - 0x7F
    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 0x80 - 0x8F
    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 0x90 - 0x9F
    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 0xA0 - 0xAF
    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 0xB0 - 0xBF
    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 0xC0 - 0xCF
    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 0xD0 - 0xDF
    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 0xE0 - 0xEF
    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 0xF0 - 0xFF
];

fn main() {
    println!("Hello, world!");
}

#[cfg(test)]
mod tests {
    use test::black_box;
    use test::Bencher;

    use super::*;

    extern crate test;

    #[bench]
    fn bench_digit_check(b: &mut Bencher) {
        b.iter(|| {
            for c in 0..=255_u8 {
                black_box(CHAR_LOOKUP_TABLE[c as usize] == CHAR_DIGIT);
            }
        });
    }

    #[bench]
    fn bench_is_ascii_digit(b: &mut Bencher) {
        b.iter(|| {
            for c in 0..255_u8 {
                black_box(c.is_ascii_digit());
            }
        });
    }
}

gistfile1.txt

$ cargo bench

running 2 tests
test tests::bench_digit_check    ... bench:         124 ns/iter (+/- 15)
test tests::bench_is_ascii_digit ... bench:          85 ns/iter (+/- 10)

test result: ok. 0 passed; 0 failed; 0 ignored; 2 measured; 0 filtered out; finished in 6.77s