// Copyright 2015-2019 Parity Technologies (UK) Ltd.
// This file is part of Parity Ethereum.

// Parity Ethereum is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Parity Ethereum is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Parity Ethereum.  If not, see <http://www.gnu.org/licenses/>.

use std::{
    ops::{Deref, DerefMut},
    ptr,
};

/// Wrapper to zero out memory when dropped.
#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct Memzero<T: AsMut<[u8]>> {
    mem: T,
}

impl<T: AsMut<[u8]>> From<T> for Memzero<T> {
    fn from(mem: T) -> Memzero<T> {
        Memzero { mem }
    }
}

impl<T: AsMut<[u8]>> Drop for Memzero<T> {
    fn drop(&mut self) {
        unsafe {
            for byte_ref in self.mem.as_mut() {
                ptr::write_volatile(byte_ref, 0)
            }
        }
    }
}

impl<T: AsMut<[u8]>> Deref for Memzero<T> {
    type Target = T;

    fn deref(&self) -> &Self::Target {
        &self.mem
    }
}

impl<T: AsMut<[u8]>> DerefMut for Memzero<T> {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.mem
    }
}