memchr.rs.html -- source
Description: Source to the Rust file `src/libstd/memchr.rs`.
Keywords: rust, rustlang, rust-lang

      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

    // Original implementation taken from rust-memchr.
    // Copyright 2015 Andrew Gallant, bluss and Nicolas Koch

    /// A safe interface to `memchr`.
    ///
    /// Returns the index corresponding to the first occurrence of `needle` in
    /// `haystack`, or `None` if one is not found.
    ///
    /// memchr reduces to super-optimized machine code at around an order of
    /// magnitude faster than `haystack.iter().position(|&b| b == needle)`.
    /// (See benchmarks.)
    ///
    /// # Examples
    ///
    /// This shows how to find the first position of a byte in a byte string.
    ///
    /// ```ignore (cannot-doctest-private-modules)
    /// use memchr::memchr;
    ///
    /// let haystack = b"the quick brown fox";
    /// assert_eq!(memchr(b'k', haystack), Some(8));
    /// ```
    #[inline]
    pub fn memchr(needle: u8, haystack: &[u8]) -> Option<usize> {
        crate::sys::memchr::memchr(needle, haystack)
    }

    /// A safe interface to `memrchr`.
    ///
    /// Returns the index corresponding to the last occurrence of `needle` in
    /// `haystack`, or `None` if one is not found.
    ///
    /// # Examples
    ///
    /// This shows how to find the last position of a byte in a byte string.
    ///
    /// ```ignore (cannot-doctest-private-modules)
    /// use memchr::memrchr;
    ///
    /// let haystack = b"the quick brown fox";
    /// assert_eq!(memrchr(b'o', haystack), Some(17));
    /// ```
    #[inline]
    pub fn memrchr(needle: u8, haystack: &[u8]) -> Option<usize> {
        crate::sys::memchr::memrchr(needle, haystack)
    }

    #[cfg(test)]
    mod tests {
        // test the implementations for the current platform
        use super::{memchr, memrchr};

        #[test]
        fn matches_one() {
            assert_eq!(Some(0), memchr(b'a', b"a"));
        }

        #[test]
        fn matches_begin() {
            assert_eq!(Some(0), memchr(b'a', b"aaaa"));
        }

        #[test]
        fn matches_end() {
            assert_eq!(Some(4), memchr(b'z', b"aaaaz"));
        }

        #[test]
        fn matches_nul() {
            assert_eq!(Some(4), memchr(b'\x00', b"aaaa\x00"));
        }

        #[test]
        fn matches_past_nul() {
            assert_eq!(Some(5), memchr(b'z', b"aaaa\x00z"));
        }

        #[test]
        fn no_match_empty() {
            assert_eq!(None, memchr(b'a', b""));
        }

        #[test]
        fn no_match() {
            assert_eq!(None, memchr(b'a', b"xyz"));
        }

        #[test]
        fn matches_one_reversed() {
            assert_eq!(Some(0), memrchr(b'a', b"a"));
        }

        #[test]
        fn matches_begin_reversed() {
            assert_eq!(Some(3), memrchr(b'a', b"aaaa"));
        }

        #[test]
        fn matches_end_reversed() {
            assert_eq!(Some(0), memrchr(b'z', b"zaaaa"));
        }

        #[test]
        fn matches_nul_reversed() {
            assert_eq!(Some(4), memrchr(b'\x00', b"aaaa\x00"));
        }

        #[test]
        fn matches_past_nul_reversed() {
            assert_eq!(Some(0), memrchr(b'z', b"z\x00aaaa"));
        }

        #[test]
        fn no_match_empty_reversed() {
            assert_eq!(None, memrchr(b'a', b""));
        }

        #[test]
        fn no_match_reversed() {
            assert_eq!(None, memrchr(b'a', b"xyz"));
        }

        #[test]
        fn each_alignment() {
            let mut data = [1u8; 64];
            let needle = 2;
            let pos = 40;
            data[pos] = needle;
            for start in 0..16 {
                assert_eq!(Some(pos - start), memchr(needle, &data[start..]));
            }
        }
    }