num_traits/ops/bytes.rs
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use core::borrow::{Borrow, BorrowMut};
use core::cmp::{Eq, Ord, PartialEq, PartialOrd};
use core::fmt::Debug;
use core::hash::Hash;
pub trait NumBytes:
Debug
+ AsRef<[u8]>
+ AsMut<[u8]>
+ PartialEq
+ Eq
+ PartialOrd
+ Ord
+ Hash
+ Borrow<[u8]>
+ BorrowMut<[u8]>
{
}
impl<T> NumBytes for T where
T: Debug
+ AsRef<[u8]>
+ AsMut<[u8]>
+ PartialEq
+ Eq
+ PartialOrd
+ Ord
+ Hash
+ Borrow<[u8]>
+ BorrowMut<[u8]>
+ ?Sized
{
}
pub trait ToBytes {
type Bytes: NumBytes;
/// Return the memory representation of this number as a byte array in big-endian byte order.
///
/// # Examples
///
/// ```
/// use num_traits::ToBytes;
///
/// let bytes = ToBytes::to_be_bytes(&0x12345678u32);
/// assert_eq!(bytes, [0x12, 0x34, 0x56, 0x78]);
/// ```
fn to_be_bytes(&self) -> Self::Bytes;
/// Return the memory representation of this number as a byte array in little-endian byte order.
///
/// # Examples
///
/// ```
/// use num_traits::ToBytes;
///
/// let bytes = ToBytes::to_le_bytes(&0x12345678u32);
/// assert_eq!(bytes, [0x78, 0x56, 0x34, 0x12]);
/// ```
fn to_le_bytes(&self) -> Self::Bytes;
/// Return the memory representation of this number as a byte array in native byte order.
///
/// As the target platform's native endianness is used,
/// portable code should use [`to_be_bytes`] or [`to_le_bytes`], as appropriate, instead.
///
/// [`to_be_bytes`]: #method.to_be_bytes
/// [`to_le_bytes`]: #method.to_le_bytes
///
/// # Examples
///
/// ```
/// use num_traits::ToBytes;
///
/// #[cfg(target_endian = "big")]
/// let expected = [0x12, 0x34, 0x56, 0x78];
///
/// #[cfg(target_endian = "little")]
/// let expected = [0x78, 0x56, 0x34, 0x12];
///
/// let bytes = ToBytes::to_ne_bytes(&0x12345678u32);
/// assert_eq!(bytes, expected)
/// ```
fn to_ne_bytes(&self) -> Self::Bytes {
#[cfg(target_endian = "big")]
let bytes = self.to_be_bytes();
#[cfg(target_endian = "little")]
let bytes = self.to_le_bytes();
bytes
}
}
pub trait FromBytes: Sized {
type Bytes: NumBytes + ?Sized;
/// Create a number from its representation as a byte array in big endian.
///
/// # Examples
///
/// ```
/// use num_traits::FromBytes;
///
/// let value: u32 = FromBytes::from_be_bytes(&[0x12, 0x34, 0x56, 0x78]);
/// assert_eq!(value, 0x12345678);
/// ```
fn from_be_bytes(bytes: &Self::Bytes) -> Self;
/// Create a number from its representation as a byte array in little endian.
///
/// # Examples
///
/// ```
/// use num_traits::FromBytes;
///
/// let value: u32 = FromBytes::from_le_bytes(&[0x78, 0x56, 0x34, 0x12]);
/// assert_eq!(value, 0x12345678);
/// ```
fn from_le_bytes(bytes: &Self::Bytes) -> Self;
/// Create a number from its memory representation as a byte array in native endianness.
///
/// As the target platform's native endianness is used,
/// portable code likely wants to use [`from_be_bytes`] or [`from_le_bytes`], as appropriate instead.
///
/// [`from_be_bytes`]: #method.from_be_bytes
/// [`from_le_bytes`]: #method.from_le_bytes
///
/// # Examples
///
/// ```
/// use num_traits::FromBytes;
///
/// #[cfg(target_endian = "big")]
/// let bytes = [0x12, 0x34, 0x56, 0x78];
///
/// #[cfg(target_endian = "little")]
/// let bytes = [0x78, 0x56, 0x34, 0x12];
///
/// let value: u32 = FromBytes::from_ne_bytes(&bytes);
/// assert_eq!(value, 0x12345678)
/// ```
fn from_ne_bytes(bytes: &Self::Bytes) -> Self {
#[cfg(target_endian = "big")]
let this = Self::from_be_bytes(bytes);
#[cfg(target_endian = "little")]
let this = Self::from_le_bytes(bytes);
this
}
}
macro_rules! float_to_from_bytes_impl {
($T:ty, $L:expr) => {
impl ToBytes for $T {
type Bytes = [u8; $L];
#[inline]
fn to_be_bytes(&self) -> Self::Bytes {
<$T>::to_be_bytes(*self)
}
#[inline]
fn to_le_bytes(&self) -> Self::Bytes {
<$T>::to_le_bytes(*self)
}
#[inline]
fn to_ne_bytes(&self) -> Self::Bytes {
<$T>::to_ne_bytes(*self)
}
}
impl FromBytes for $T {
type Bytes = [u8; $L];
#[inline]
fn from_be_bytes(bytes: &Self::Bytes) -> Self {
<$T>::from_be_bytes(*bytes)
}
#[inline]
fn from_le_bytes(bytes: &Self::Bytes) -> Self {
<$T>::from_le_bytes(*bytes)
}
#[inline]
fn from_ne_bytes(bytes: &Self::Bytes) -> Self {
<$T>::from_ne_bytes(*bytes)
}
}
};
}
macro_rules! int_to_from_bytes_impl {
($T:ty, $L:expr) => {
impl ToBytes for $T {
type Bytes = [u8; $L];
#[inline]
fn to_be_bytes(&self) -> Self::Bytes {
<$T>::to_be_bytes(*self)
}
#[inline]
fn to_le_bytes(&self) -> Self::Bytes {
<$T>::to_le_bytes(*self)
}
#[inline]
fn to_ne_bytes(&self) -> Self::Bytes {
<$T>::to_ne_bytes(*self)
}
}
impl FromBytes for $T {
type Bytes = [u8; $L];
#[inline]
fn from_be_bytes(bytes: &Self::Bytes) -> Self {
<$T>::from_be_bytes(*bytes)
}
#[inline]
fn from_le_bytes(bytes: &Self::Bytes) -> Self {
<$T>::from_le_bytes(*bytes)
}
#[inline]
fn from_ne_bytes(bytes: &Self::Bytes) -> Self {
<$T>::from_ne_bytes(*bytes)
}
}
};
}
int_to_from_bytes_impl!(u8, 1);
int_to_from_bytes_impl!(u16, 2);
int_to_from_bytes_impl!(u32, 4);
int_to_from_bytes_impl!(u64, 8);
int_to_from_bytes_impl!(u128, 16);
#[cfg(target_pointer_width = "64")]
int_to_from_bytes_impl!(usize, 8);
#[cfg(target_pointer_width = "32")]
int_to_from_bytes_impl!(usize, 4);
int_to_from_bytes_impl!(i8, 1);
int_to_from_bytes_impl!(i16, 2);
int_to_from_bytes_impl!(i32, 4);
int_to_from_bytes_impl!(i64, 8);
int_to_from_bytes_impl!(i128, 16);
#[cfg(target_pointer_width = "64")]
int_to_from_bytes_impl!(isize, 8);
#[cfg(target_pointer_width = "32")]
int_to_from_bytes_impl!(isize, 4);
float_to_from_bytes_impl!(f32, 4);
float_to_from_bytes_impl!(f64, 8);
#[cfg(test)]
mod tests {
use super::*;
macro_rules! check_to_from_bytes {
($( $ty:ty )+) => {$({
let n = 1;
let be = <$ty as ToBytes>::to_be_bytes(&n);
let le = <$ty as ToBytes>::to_le_bytes(&n);
let ne = <$ty as ToBytes>::to_ne_bytes(&n);
assert_eq!(*be.last().unwrap(), 1);
assert_eq!(*le.first().unwrap(), 1);
if cfg!(target_endian = "big") {
assert_eq!(*ne.last().unwrap(), 1);
} else {
assert_eq!(*ne.first().unwrap(), 1);
}
assert_eq!(<$ty as FromBytes>::from_be_bytes(&be), n);
assert_eq!(<$ty as FromBytes>::from_le_bytes(&le), n);
if cfg!(target_endian = "big") {
assert_eq!(<$ty as FromBytes>::from_ne_bytes(&be), n);
} else {
assert_eq!(<$ty as FromBytes>::from_ne_bytes(&le), n);
}
})+}
}
#[test]
fn convert_between_int_and_bytes() {
check_to_from_bytes!(u8 u16 u32 u64 u128 usize);
check_to_from_bytes!(i8 i16 i32 i64 i128 isize);
}
#[test]
fn convert_between_float_and_bytes() {
macro_rules! check_to_from_bytes {
($( $ty:ty )+) => {$(
let n: $ty = 3.14;
let be = <$ty as ToBytes>::to_be_bytes(&n);
let le = <$ty as ToBytes>::to_le_bytes(&n);
let ne = <$ty as ToBytes>::to_ne_bytes(&n);
assert_eq!(<$ty as FromBytes>::from_be_bytes(&be), n);
assert_eq!(<$ty as FromBytes>::from_le_bytes(&le), n);
if cfg!(target_endian = "big") {
assert_eq!(ne, be);
assert_eq!(<$ty as FromBytes>::from_ne_bytes(&be), n);
} else {
assert_eq!(ne, le);
assert_eq!(<$ty as FromBytes>::from_ne_bytes(&le), n);
}
)+}
}
check_to_from_bytes!(f32 f64);
}
}