openethereum/util/src/bytes.rs

// Copyright 2015, 2016 Ethcore (UK) Ltd.
// This file is part of Parity.

// Parity 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 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.  If not, see <http://www.gnu.org/licenses/>.

//! Unified interfaces for bytes operations on basic types
//!
//! # Examples
//! ```rust
//! extern crate ethcore_util as util;
//!
//! fn bytes_convertable() {
//! 	use util::bytes::BytesConvertable;
//!
//! 	let arr = [0; 5];
//! 	let slice: &[u8] = arr.as_slice();
//! }
//!
//! fn main() {
//! 	bytes_convertable();
//! }
//! ```

use std::fmt;
use std::slice;
use std::ops::{Deref, DerefMut};

/// Slice pretty print helper
pub struct PrettySlice<'a> (&'a [u8]);

impl<'a> fmt::Debug for PrettySlice<'a> {
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
		for i in 0..self.0.len() {
			match i > 0 {
				true => { try!(write!(f, "·{:02x}", self.0[i])); },
				false => { try!(write!(f, "{:02x}", self.0[i])); },
			}
		}
		Ok(())
	}
}

impl<'a> fmt::Display for PrettySlice<'a> {
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
		for i in 0..self.0.len() {
			try!(write!(f, "{:02x}", self.0[i]));
		}
		Ok(())
	}
}

/// Trait to allow a type to be pretty-printed in `format!`, where unoverridable
/// defaults cannot otherwise be avoided.
pub trait ToPretty {
	/// Convert a type into a derivative form in order to make `format!` print it prettily.
	fn pretty(&self) -> PrettySlice;
	/// Express the object as a hex string.
	fn to_hex(&self) -> String {
		format!("{}", self.pretty())
	}
}

impl<'a> ToPretty for &'a [u8] {
	fn pretty(&self) -> PrettySlice {
		PrettySlice(self)
	}
}

impl<'a> ToPretty for &'a Bytes {
	fn pretty(&self) -> PrettySlice {
		PrettySlice(self.as_slice())
	}
}
impl ToPretty for Bytes {
	fn pretty(&self) -> PrettySlice {
		PrettySlice(self.as_slice())
	}
}

/// A byte collection reference that can either be a slice or a vector
pub enum BytesRef<'a> {
	/// This is a reference to a vector
	Flexible(&'a mut Bytes),
	/// This is a reference to a slice
	Fixed(&'a mut [u8])
}

impl<'a> Deref for BytesRef<'a> {
	type Target = [u8];

	fn deref(&self) -> &[u8] {
		match *self {
			BytesRef::Flexible(ref bytes) => bytes,
			BytesRef::Fixed(ref bytes) => bytes,
		}
	}
}

impl <'a> DerefMut for BytesRef<'a> {
	fn deref_mut(&mut self) -> &mut [u8] {
		match *self {
			BytesRef::Flexible(ref mut bytes) => bytes,
			BytesRef::Fixed(ref mut bytes) => bytes,
		}
	}
}

/// Vector of bytes
pub type Bytes = Vec<u8>;

/// Slice of bytes to underlying memory
pub trait BytesConvertable {
	/// Get the underlying byte-wise representation of the value.
	fn as_slice(&self) -> &[u8];
	/// Get a copy of the underlying byte-wise representation.
	fn to_bytes(&self) -> Bytes { self.as_slice().to_vec() }
}

impl<T> BytesConvertable for T where T: AsRef<[u8]> {
	fn as_slice(&self) -> &[u8] { self.as_ref() }
}

#[test]
fn bytes_convertable() {
	assert_eq!(vec![0x12u8, 0x34].as_slice(), &[0x12u8, 0x34]);
	assert!([0u8; 0].as_slice().is_empty());
}

/// Simple trait to allow for raw population of a Sized object from a byte slice.
pub trait Populatable {
	/// Copies a bunch of bytes `d` to `self`, overwriting as necessary.
	///
	/// If `d` is smaller, zero-out the remaining bytes.
	fn populate_raw(&mut self, d: &[u8]) {
		let mut s = self.as_slice_mut();
		for i in 0..s.len() {
			s[i] = if i < d.len() {d[i]} else {0};
		}
	}

	/// Copies a bunch of bytes `d` to `self`, overwriting as necessary.
	///
	/// If `d` is smaller, will leave some bytes untouched.
	fn copy_raw(&mut self, d: &[u8]) {
		use std::io::Write;
		self.as_slice_mut().write(d).unwrap();
	}

	/// Copies the raw representation of an object `d` to `self`, overwriting as necessary.
	///
	/// If `d` is smaller, zero-out the remaining bytes.
	fn populate_raw_from(&mut self, d: &BytesConvertable) { self.populate_raw(d.as_slice()); }

	/// Copies the raw representation of an object `d` to `self`, overwriting as necessary.
	///
	/// If `d` is smaller, will leave some bytes untouched.
	fn copy_raw_from(&mut self, d: &BytesConvertable) { self.copy_raw(d.as_slice()); }

	/// Get the raw slice for this object.
	fn as_slice_mut(&mut self) -> &mut [u8];
}

impl<T> Populatable for T where T: Sized {
	fn as_slice_mut(&mut self) -> &mut [u8] {
		use std::mem;
		unsafe {
			slice::from_raw_parts_mut(self as *mut T as *mut u8, mem::size_of::<T>())
		}
	}
}

impl<T> Populatable for [T] where T: Sized {
	fn as_slice_mut(&mut self) -> &mut [u8] {
		use std::mem;
		unsafe {
			slice::from_raw_parts_mut(self.as_mut_ptr() as *mut u8, mem::size_of::<T>() * self.len())
		}
	}
}

#[test]
fn fax_raw() {
	let mut x = [255u8; 4];
	x.copy_raw(&[1u8; 2][..]);
	assert_eq!(x, [1u8, 1, 255, 255]);
	let mut x = [255u8; 4];
	x.copy_raw(&[1u8; 6][..]);
	assert_eq!(x, [1u8, 1, 1, 1]);
}

#[test]
fn populate_raw() {
	let mut x = [255u8; 4];
	x.populate_raw(&[1u8; 2][..]);
	assert_eq!(x, [1u8, 1, 0, 0]);
	let mut x = [255u8; 4];
	x.populate_raw(&[1u8; 6][..]);
	assert_eq!(x, [1u8, 1, 1, 1]);
}

#[test]
fn populate_raw_dyn() {
	let mut x = [255u8; 4];
	x.populate_raw(&[1u8; 2][..]);
	assert_eq!(&x[..], [1u8, 1, 0, 0]);
	let mut x = [255u8; 4];
	x.populate_raw(&[1u8; 6][..]);
	assert_eq!(&x[..], [1u8, 1, 1, 1]);
}

#[test]
fn fax_raw_dyn() {
	let mut x = [255u8; 4];
	x.copy_raw(&[1u8; 2][..]);
	assert_eq!(&x[..], [1u8, 1, 255, 255]);
	let mut x = [255u8; 4];
	x.copy_raw(&[1u8; 6][..]);
	assert_eq!(&x[..], [1u8, 1, 1, 1]);
}

#[test]
fn populate_big_types() {
	use hash::*;
	let a: H160 = "ffffffffffffffffffffffffffffffffffffffff".into();
	let mut h: H256 = 0x69.into();
	h.populate_raw_from(&a);
	assert_eq!(h, "ffffffffffffffffffffffffffffffffffffffff000000000000000000000000".into());

	let mut h: H256 = 0x69.into();
	h.copy_raw_from(&a);
	assert_eq!(h, "ffffffffffffffffffffffffffffffffffffffff000000000000000000000069".into());
}