1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166

#![feature(test, cfg_target_feature, stdsimd)]

extern crate faster;

use faster::prelude::*;

#[cfg(all(target_arch = "x86_64", all(not(target_feature = "avx"), target_feature = "sse2")))]
use std::arch::x86_64::_mm_movemask_epi8 as movemask;

#[cfg(all(target_arch = "x86_64", target_feature = "avx"))]
use std::arch::x86_64::_mm256_movemask_epi8 as movemask;

#[cfg(all(target_arch = "x86", target_feature = "sse2"))]
use std::arch::x86::_mm_movemask_epi8 as movemask;

use std::mem;

#[inline]
pub fn fastchr(needle: u8, haystack: &[u8]) -> Option<usize> {
    let mut iter = haystack.simd_iter();

    while let Some(v) = iter.next_vector() {
        let b = v_to_byte_mask(v, needle);
        if b != 0 {
            return Some(iter.scalar_position() + b.trailing_zeros() as usize - u8s::WIDTH);
        }
    }

    while let Some(s) = iter.next() {
        if s == needle {
            return Some(iter.scalar_position() - 1);
        }
    }

    None
}

#[inline]
fn v_to_byte_mask(v: u8s, needle: u8) -> usize {
    unsafe {
        let v = v.eq(u8s(needle));
        movemask(mem::transmute(v)) as usize 
    }
}



#[cfg(test)]
mod tests {
    extern crate test;
    extern crate memchr;

    use self::test::Bencher;
    use self::memchr::memchr;

    use super::*;

    use std::iter;

    const LONG_PREFIX_LEN: usize = 500000;
    const SHORT_PREFIX_LEN: usize = u8s::WIDTH * 2 - 1;
    const ODD_PREFIX_LEN: usize = 50003;
    const BURIED_SAMPLE_LEN: usize = 241;
    const NEEDLE: u8 = 70;

    fn generate_long_sample() -> Vec<u8> {
            iter::repeat(14u8).take(LONG_PREFIX_LEN)
            .chain(iter::once(NEEDLE))
            .chain(iter::repeat(200u8).take(ODD_PREFIX_LEN))
            .collect()
    }

    fn generate_short_sample() -> Vec<u8> {
            iter::repeat(14u8).take(SHORT_PREFIX_LEN)
            .chain(iter::once(NEEDLE))
            .collect()
    }

    fn generate_odd_sample() -> Vec<u8> {
            iter::repeat(14u8).take(ODD_PREFIX_LEN)
            .chain(iter::once(NEEDLE))
            .collect()
    }
    fn generate_long_negative_sample() -> Vec<u8> {
        iter::repeat(231).take(ODD_PREFIX_LEN)
        .collect()
    }

    fn generate_buried_sample() -> Vec<u8> {
        iter::repeat(231u8).take(BURIED_SAMPLE_LEN)
        .chain(iter::once(NEEDLE))
        .chain(iter::repeat(231u8).take(3))
        .chain(iter::once(NEEDLE))
        .chain(iter::repeat(231u8).take(ODD_PREFIX_LEN))
        .collect()
    }

    #[test]
    fn buried_sample_test() {
        let data = generate_buried_sample();
        assert_eq!(Some(BURIED_SAMPLE_LEN), fastchr(NEEDLE, &data));
    }

    #[test]
    fn negative_sample_test() {
        let data = generate_long_negative_sample();
        assert_eq!(None, fastchr(NEEDLE, &data));
    }
    
    #[test]
    fn qbf_test() {
        let haystack = b"the quick brown fox";
        println!("{:?}", haystack);
        println!("{:?}", (&haystack[..]).simd_iter().next_vector());
        assert_eq!(Some(8), fastchr(b'k', haystack));
    }

    #[test]
    fn memchr_odd_compat_test() {
        let data = generate_odd_sample();
        assert_eq!(memchr(NEEDLE, &data), fastchr(NEEDLE, &data));
    }

    #[test]
    fn memchr_short_compat_test() {
        let data = generate_short_sample();
        assert_eq!(memchr(NEEDLE, &data), fastchr(NEEDLE, &data));
    }

    #[test]
    fn long_find_test() {
        let data = generate_long_sample();
        assert_eq!(Some(LONG_PREFIX_LEN), fastchr(NEEDLE, &data));
    }

    #[test]
    fn short_find_test() {
        let data = generate_short_sample();
        assert_eq!(Some(SHORT_PREFIX_LEN), fastchr(NEEDLE, &data));
    }

    #[test]
    fn odd_find_test() {
        let data = generate_odd_sample();
        assert_eq!(Some(ODD_PREFIX_LEN), fastchr(NEEDLE, &data));
    }

    #[test]
    fn empty_find_test() {
        let data = Vec::new();
        assert_eq!(None, fastchr(NEEDLE, &data));
    }

    #[bench]
    fn fastchr_bench(b: &mut Bencher) {
        let data = generate_long_sample();
        b.iter(|| fastchr(NEEDLE, &data));
    }

    #[bench]
    fn memchr_bench(b: &mut Bencher) {
        let data = generate_long_sample();
        b.iter(|| memchr(NEEDLE, &data));
    }

}