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

use crate::bytes::{NumBytes, Read, ReadError, Write, WriteError};

/// Variable Length Signed Integer. This provides more efficient serialization
/// of 32-bit signed int. It serializes a 32-bit signed integer in as few bytes
/// as possible. `SignedInt` is signed and uses
/// [Zig-Zag encoding](https://developers.google.com/protocol-buffers/docs/encoding#signed-integers)
/// <https://github.com/EOSIO/eosio.cdt/blob/4985359a30da1f883418b7133593f835927b8046/libraries/eosiolib/core/eosio/varint.hpp#L239-L465>
#[derive(PartialEq, Eq, PartialOrd, Ord, Debug, Clone, Hash, Default)]
pub struct SignedInt(i32);

impl From<isize> for SignedInt {
    #[must_use]
    #[allow(clippy::cast_possible_truncation)]
    fn from(v: isize) -> Self {
        Self(v as i32)
    }
}

impl From<SignedInt> for isize {
    #[must_use]
    fn from(v: SignedInt) -> Self {
        v.0 as Self
    }
}

impl From<i32> for SignedInt {
    #[must_use]
    fn from(v: i32) -> Self {
        Self(v)
    }
}

impl From<SignedInt> for i32 {
    #[must_use]
    fn from(v: SignedInt) -> Self {
        v.0
    }
}

impl From<i16> for SignedInt {
    #[must_use]
    fn from(v: i16) -> Self {
        Self(v.into())
    }
}

impl From<i8> for SignedInt {
    #[must_use]
    fn from(v: i8) -> Self {
        Self(v.into())
    }
}

impl NumBytes for SignedInt {
    #[inline]
    #[must_use]
    #[allow(clippy::cast_sign_loss)]
    fn num_bytes(&self) -> usize {
        let mut val = ((self.0 << 1) ^ (self.0 >> 31)) as u32;
        let mut bytes = 0_usize;
        loop {
            val >>= 7;
            bytes += 1;
            if val == 0 {
                break;
            }
        }
        bytes
    }
}

impl Read for SignedInt {
    #[inline]
    #[allow(clippy::cast_possible_wrap, clippy::cast_possible_truncation)]
    fn read(bytes: &[u8], pos: &mut usize) -> Result<Self, ReadError> {
        let mut v = 0_u32;
        let mut by = 0_u32;
        loop {
            let b = u8::read(bytes, pos)?;
            v |= u32::from(b & 0x7f) << by;
            by += 7;
            if b & 0x80 == 0 {
                break;
            }
        }
        let value = (v >> 1) ^ ((u64::from(!(v & 1)) + 1_u64) as u32);
        Ok(Self(value as i32))
    }
}

impl Write for SignedInt {
    #[inline]
    #[allow(clippy::cast_possible_truncation, clippy::cast_sign_loss)]
    fn write(
        &self,
        bytes: &mut [u8],
        pos: &mut usize,
    ) -> Result<(), WriteError> {
        let mut val = ((self.0 << 1) ^ (self.0 >> 31)) as u32;
        loop {
            let mut b = (val as u8) & 0x7f;
            val >>= 7;
            b |= ((val > 0) as u8) << 7;
            b.write(bytes, pos)?;
            if val == 0 {
                break;
            }
        }
        Ok(())
    }
}

#[cfg(test)]
mod signed_int_tests {
    use super::SignedInt;
    use crate::bytes::{NumBytes, Read, Write};

    macro_rules! write_read_tests {
        ($($i:ident, $v:expr, $n:expr)*) => ($(
            #[test]
            fn $i() {
                let mut bytes = [0_u8; 10];
                let mut write_pos = 0;
                let varint: SignedInt = $v.into();
                assert_eq!(varint.num_bytes(), $n);

                varint.write(&mut bytes, &mut write_pos).unwrap();
                assert_eq!(write_pos, $n);
                let mut read_pos = 0;
                let result = SignedInt::read(&bytes, &mut read_pos).unwrap();
                assert_eq!(result, varint);
                assert_eq!(read_pos, write_pos);
            }
        )*)
    }

    write_read_tests! {
        read_write_1, 1_i32, 1
        read_write_1_neg, -1_i32, 1
        read_write_50, 50_i32, 1
        read_write_50_neg, -50_i32, 1
        read_write_i8_min, i8::min_value(), 2
        read_write_i8_zero, 0_i8, 1
        read_write_i8_max, i8::max_value(), 2
        read_write_i16_min, i16::min_value(), 3
        read_write_i16_zero, 0_i16, 1
        read_write_i16_max, i16::max_value(), 3
        read_write_i32_min, i32::min_value(), 5
        read_write_i32_zero, 0_i32, 1
        read_write_i32_max, i32::max_value(), 5
    }
}