web-assembler 0.1.2

An in memory wasm assembler for Rust.
Documentation 
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

#[inline]
pub fn write_uint8(buf: &mut Vec<u8>, u: u8) -> usize {
    buf.push(u);
    1
}

#[inline]
pub fn write_uint16(buf: &mut Vec<u8>, u: u16) -> usize {
    let mut size = 0;
    size += write_uint8(buf, (u & 0xff) as u8);
    size += write_uint8(buf, ((u >> 8) & 0xff) as u8);
    size
}

#[inline]
pub fn write_uint32(buf: &mut Vec<u8>, u: u32) -> usize {
    let mut size = 0;
    size += write_uint16(buf, (u & 0xffff) as u16);
    size += write_uint16(buf, ((u >> 16) & 0xffff) as u16);
    size
}

#[inline]
pub fn write_uint64(buf: &mut Vec<u8>, u: u64) -> usize {
    let mut size = 0;
    size += write_uint32(buf, (u & 0xffffffff) as u32);
    size += write_uint32(buf, ((u >> 32) & 0xffffffff) as u32);
    size
}

#[inline]
pub fn write_varuint1(buf: &mut Vec<u8>, u: u8) -> usize {
    write_uint8(buf, u)
}

#[allow(dead_code)]
#[inline]
pub fn write_varuint7(buf: &mut Vec<u8>, u: u8) -> usize {
    write_uint8(buf, u)
}

#[inline]
pub fn write_varint7(buf: &mut Vec<u8>, i: i8) -> usize {
    write_uint8(buf, (i as u8) ^ 0x80)
}

macro_rules! gen_write_var_unsigned {
    ($name: ident, $ty: ty) => {
        #[inline]
        #[allow(unused_comparisons)]
        #[allow(overflowing_literals)]
        pub fn $name(buf: &mut Vec<u8>, mut u: $ty) -> usize {
            let end: i8 = if u < 0 { 0xff } else { 0 };

            let mut size = 0;
            let bit7 = 0b01111111;
            let mut cur: u8 = (u & bit7) as u8;
            // rust generates sar for i32 by >>
            u >>= 7;
            while u != (end as $ty) {
                size += write_uint8(buf, cur | 0x80);
                cur = (u & bit7) as u8;
                u >>= 7;
            }
            size += write_uint8(buf, cur);
            size
        }
    };
}

macro_rules! gen_write_var_signed {
    ($name: ident, $ty: ty) => {
        #[inline]
        pub fn $name(buf: &mut Vec<u8>, mut u: $ty) -> usize {
            let mut size = 0;
            let bit7 = 0b0111_1111;
            let mut cur: u8 = (u & bit7) as u8;
            let upper = 64 as $ty;
            let lower = -64 as $ty;
            while u < lower || upper <= u {
                size += write_uint8(buf, cur | 0x80);
                u >>= 7;
                cur = (u & bit7) as u8;
            }
            size += write_uint8(buf, cur);
            size
        }
    };
}

gen_write_var_unsigned!(write_varuint32, u32);
gen_write_var_signed!(write_varint32, i32);
gen_write_var_signed!(write_varint64, i64);

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn test_write_varint32() {
        let mut buf = vec![];
        let size = write_varint32(&mut buf, 0b0110_0001);
        assert_eq!(size, 2);
        assert_eq!(buf, &[0b1110_0001, 0b0000_0000]);
    }

    #[test]
    fn test_write_varint32_edge1() {
        let mut buf = vec![];
        let size = write_varint32(&mut buf, 63);
        assert_eq!(size, 1);
        assert_eq!(buf, &[0b0011_1111]);
    }

    #[test]
    fn test_write_varint32_edge2() {
        let mut buf = vec![];
        let size = write_varint32(&mut buf, 64);
        assert_eq!(size, 2);
        assert_eq!(buf, &[0b1100_0000, 0b0000_0000]);
    }

    #[test]
    fn test_write_varint32_edge3() {
        let mut buf = vec![];
        let size = write_varint32(&mut buf, -64);
        assert_eq!(size, 1);
        assert_eq!(buf, &[0b0100_0000]);
    }

    #[test]
    fn test_write_varint32_edge4() {
        let mut buf = vec![];
        let size = write_varint32(&mut buf, -65);
        assert_eq!(size, 2);
        assert_eq!(buf, &[0b1011_1111, 0b0111_1111]);
    }
}

#[inline]
pub fn write_slice(buf: &mut Vec<u8>, u: &[u8]) -> usize {
    buf.extend_from_slice(u);
    u.len()
}