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

// Copyright (c) The Diem Core Contributors
// SPDX-License-Identifier: Apache-2.0

#![forbid(unsafe_code)]

//! `Nibble` represents a four-bit unsigned integer.

pub mod nibble_path;

use diem_crypto::HashValue;
#[cfg(any(test, feature = "fuzzing"))]
use proptest::prelude::*;
use serde::{Deserialize, Serialize};
use std::fmt;

/// The hardcoded maximum height of a state merkle tree in nibbles.
pub const ROOT_NIBBLE_HEIGHT: usize = HashValue::LENGTH * 2;

#[derive(Clone, Copy, Debug, Hash, Eq, PartialEq, Ord, PartialOrd, Serialize, Deserialize)]
pub struct Nibble(u8);

impl From<u8> for Nibble {
    fn from(nibble: u8) -> Self {
        assert!(nibble < 16, "Nibble out of range: {}", nibble);
        Self(nibble)
    }
}

impl From<Nibble> for u8 {
    fn from(nibble: Nibble) -> Self {
        nibble.0
    }
}

impl fmt::LowerHex for Nibble {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{:x}", self.0)
    }
}

#[cfg(any(test, feature = "fuzzing"))]
impl Arbitrary for Nibble {
    type Parameters = ();
    type Strategy = BoxedStrategy<Self>;

    fn arbitrary_with(_args: Self::Parameters) -> Self::Strategy {
        (0..16u8).prop_map(Self::from).boxed()
    }
}