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

// Copyright 2021 Conflux Foundation. All rights reserved.
// Conflux is free software and distributed under GNU General Public License.
// See http://www.gnu.org/licenses/

#![forbid(unsafe_code)]

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

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

#[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(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()
    }
}