serial_traits 1.1.2

A trait that allows you to serialize to and parse from Vec<u8> buffers. Comes with implementations for primitive types, String and generic collection types (if the item type implements the trait too.)
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
145
146
147
148
149
150
151
152
153

use crate::unwrap_return;

// there is no type that all integers have which works nicely
// and lets us cast from/to our target types
// From<T> and Into<T> do not work
pub trait ExtensibleInteger {
    fn is_byte() -> bool;
    fn is_signed() -> bool;

    fn to_u8(&self) -> u8;
    fn from_u8(value: u8) -> Self;

    fn to_u128(&self) -> u128;
    fn from_u128(value: u128) -> Self;

    fn to_i128(&self) -> i128;
    fn from_i128(value: i128) -> Self;
}

macro_rules! impl_int_traits {
	( $( ($type:ty, $is_byte:expr, $is_signed:expr), )* ) => {
		$(
			impl ExtensibleInteger for $type {
                fn is_byte() -> bool { $is_byte }
                fn is_signed() -> bool { $is_signed }

				fn to_u8(&self) -> u8 { *self as u8 }
				fn from_u8(value: u8) -> Self { value as Self }

                fn to_u128(&self) -> u128 { *self as u128 }
				fn from_u128(value: u128) -> Self { value as Self }

                fn to_i128(&self) -> i128 { *self as i128 }
				fn from_i128(value: i128) -> Self { value as Self }
			}
		)*
	};
}

impl_int_traits!(
    (u8, true, false),
    (u16, false, false),
    (u32, false, false),
    (u64, false, false),
    (u128, false, false),
    (usize, false, false),
    (i8, true, true),
    (i16, false, true),
    (i32, false, true),
    (i64, false, true),
    (i128, false, true),
    (isize, false, true),
);

// 1-byte-size Optimisation
// types that are 1 byte large are directly written into a buffer as they are
// when serialized and are just directly returned when parsed

// https://en.wikipedia.org/wiki/LEB128#Encode_signed_32-bit_integer
fn serialize_i128(mut value: i128, serialized: &mut Vec<u8>) {
    loop {
        let byte = value as u8 & 0x7f;
        value >>= 7;
        if (value == 0 && (byte & 0x40) == 0) || (value == -1 && (byte & 0x40) != 0) {
            serialized.push(byte);
            break;
        }
        serialized.push(byte | 0x80);
    }
}

// https://en.wikipedia.org/wiki/LEB128#Encode_unsigned_integer
fn serialize_u128(mut value: u128, serialized: &mut Vec<u8>) {
    loop {
        let mut byte = value & 0x7f;
        value >>= 7;
        if value != 0 {
            byte |= 0x80;
        }
        serialized.push(byte as u8);
        if value == 0 {
            break;
        }
    }
}

pub fn serialize<T: ExtensibleInteger>(source: T) -> Vec<u8> {
    let mut serialized = vec![];
    if T::is_byte() {
        serialized.push(source.to_u8());
    } else if T::is_signed() {
        serialize_i128(source.to_i128(), &mut serialized);
    } else {
        serialize_u128(source.to_u128(), &mut serialized);
    }

    serialized
}

macro_rules! get_byte {
    ($bytevec:tt) => {
        unwrap_return!($bytevec.drain(0..1).next())
    };
    ($bytevec:tt, $type:ty) => {
        get_byte!($bytevec) as $type
    };
}

// https://en.wikipedia.org/wiki/LEB128#Decode_signed_32-bit_integer
fn parse_i128(data: &mut Vec<u8>) -> Option<i128> {
    let mut result = 0;
    let mut shift = 0;
    loop {
        let byte = get_byte!(data, i128);
        result |= (byte & 0x7f) << shift;
        shift += 7;
        if 0x80 & byte == 0 {
            if shift < 128 && (byte & 0x40) != 0 {
                result |= !0 << shift;
            }
            break;
        }
    }

    Some(result)
}

// https://en.wikipedia.org/wiki/LEB128#Encode_unsigned_integer
fn parse_u128(data: &mut Vec<u8>) -> Option<u128> {
    let mut result = 0;
    let mut shift = 0;

    loop {
        let byte = get_byte!(data, u128);
        result |= (byte & 0x7f) << shift;
        if byte & 0x80 == 0 {
            break;
        }
        shift += 7;
    }

    Some(result)
}

pub fn parse<T: ExtensibleInteger>(data: &mut Vec<u8>) -> Option<T> {
    if T::is_byte() {
        Some(T::from_u8(get_byte!(data)))
    } else if T::is_signed() {
        parse_i128(data).map(T::from_i128)
    } else {
        parse_u128(data).map(T::from_u128)
    }
}