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
use crate::iter::Bytes;

pub unsafe fn parse_uri_batch_16(bytes: &mut Bytes) {
    while bytes.as_ref().len() >= 16 {
        let advance = match_url_char_16_sse(bytes.as_ref());
        bytes.advance(advance);

        if advance != 16 {
            break;
        }
    }
}

#[target_feature(enable = "sse4.2")]
#[allow(non_snake_case, overflowing_literals)]
unsafe fn match_url_char_16_sse(buf: &[u8]) -> usize {
    debug_assert!(buf.len() >= 16);

    #[cfg(target_arch = "x86")]
    use core::arch::x86::*;
    #[cfg(target_arch = "x86_64")]
    use core::arch::x86_64::*;

    let ptr = buf.as_ptr();

    let LSH: __m128i = _mm_set1_epi8(0x0f);

    // The first 0xf8 corresponds to the 8 first rows of the first column
    // of URI_MAP in the crate's root, with the first row corresponding to bit 0
    // and the 8th row corresponding to bit 7.
    // The 8 first rows give 0 0 0 1 1 1 1 1, which is 0xf8 (with least
    // significant digit on the left).
    //
    // Another example just to drive the point home: in column 15, '>' is
    // rejected, so the values are 0 0 1 0 1 1 1 1, which gives us 0xf4.
    //
    // Thanks to Vlad Krasnov for explaining this stuff to us mere mortals in
    // a GitHub comment!
    //
    // https://github.com/seanmonstar/httparse/pull/89#issuecomment-807039219

    let URI: __m128i = _mm_setr_epi8(
        0xf8, 0xfc, 0xfc, 0xfc, 0xfc, 0xfc, 0xfc, 0xfc,
        0xfc, 0xfc, 0xfc, 0xfc, 0xf4, 0xfc, 0xf4, 0x7c,
    );
    let ARF: __m128i = _mm_setr_epi8(
        0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    );

    let data = _mm_lddqu_si128(ptr as *const _);
    let rbms = _mm_shuffle_epi8(URI, data);
    let cols = _mm_and_si128(LSH, _mm_srli_epi16(data, 4));
    let bits = _mm_and_si128(_mm_shuffle_epi8(ARF, cols), rbms);

    let v = _mm_cmpeq_epi8(bits, _mm_setzero_si128());
    let r = 0xffff_0000 | _mm_movemask_epi8(v) as u32;

    _tzcnt_u32(r) as usize
}

pub unsafe fn match_header_value_batch_16(bytes: &mut Bytes) {
    while bytes.as_ref().len() >= 16 {
        let advance = match_header_value_char_16_sse(bytes.as_ref());
        bytes.advance(advance);

       if advance != 16 {
            break;
       }
    }
}

#[target_feature(enable = "sse4.2")]
#[allow(non_snake_case)]
unsafe fn match_header_value_char_16_sse(buf: &[u8]) -> usize {
    debug_assert!(buf.len() >= 16);

    #[cfg(target_arch = "x86")]
    use core::arch::x86::*;
    #[cfg(target_arch = "x86_64")]
    use core::arch::x86_64::*;

    let ptr = buf.as_ptr();

    // %x09 %x20-%x7e %x80-%xff
    let TAB: __m128i = _mm_set1_epi8(0x09);
    let DEL: __m128i = _mm_set1_epi8(0x7f);
    let LOW: __m128i = _mm_set1_epi8(0x20);

    let dat = _mm_lddqu_si128(ptr as *const _);
    // unsigned comparison dat >= LOW
    let low = _mm_cmpeq_epi8(_mm_max_epu8(dat, LOW), dat);
    let tab = _mm_cmpeq_epi8(dat, TAB);
    let del = _mm_cmpeq_epi8(dat, DEL);
    let bit = _mm_andnot_si128(del, _mm_or_si128(low, tab));
    let rev = _mm_cmpeq_epi8(bit, _mm_setzero_si128());
    let res = 0xffff_0000 | _mm_movemask_epi8(rev) as u32;

    _tzcnt_u32(res) as usize
}

#[test]
fn sse_code_matches_uri_chars_table() {
    match super::detect() {
        super::SSE_42 | super::AVX_2_AND_SSE_42 => {},
        _ => return,
    }

    unsafe {
        assert!(byte_is_allowed(b'_', parse_uri_batch_16));

        for (b, allowed) in crate::URI_MAP.iter().cloned().enumerate() {
            assert_eq!(
                byte_is_allowed(b as u8, parse_uri_batch_16), allowed,
                "byte_is_allowed({:?}) should be {:?}", b, allowed,
            );
        }
    }
}

#[test]
fn sse_code_matches_header_value_chars_table() {
    match super::detect() {
        super::SSE_42 | super::AVX_2_AND_SSE_42 => {},
        _ => return,
    }

    unsafe {
        assert!(byte_is_allowed(b'_', match_header_value_batch_16));

        for (b, allowed) in crate::HEADER_VALUE_MAP.iter().cloned().enumerate() {
            assert_eq!(
                byte_is_allowed(b as u8, match_header_value_batch_16), allowed,
                "byte_is_allowed({:?}) should be {:?}", b, allowed,
            );
        }
    }
}

#[cfg(test)]
unsafe fn byte_is_allowed(byte: u8, f: unsafe fn(bytes: &mut Bytes<'_>)) -> bool {
    let slice = [
        b'_', b'_', b'_', b'_',
        b'_', b'_', b'_', b'_',
        b'_', b'_', byte, b'_',
        b'_', b'_', b'_', b'_',
    ];
    let mut bytes = Bytes::new(&slice);

    f(&mut bytes);

    match bytes.pos() {
        16 => true,
        10 => false,
        _ => unreachable!(),
    }
}