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Add a ByteOrder trait for abstracting over endian conversions

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The `Bitwise::swap_bytes` method was also moved into the `ByteOrder` trait. This was because it works on the byte level rather than the bit level.
This commit is contained in:
Brendan Zabarauskas 2014-06-14 22:53:55 -07:00 committed by Alex Crichton
parent 1273f94cbb
commit 87c529c43a
4 changed files with 263 additions and 167 deletions
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336
src/libcore/mem.rs
View File

@ -13,6 +13,7 @@
//! This module contains functions for querying the size and alignment of
//! types, initializing and manipulating memory.
use clone::Clone;
use ptr;
use intrinsics;
use intrinsics::{bswap16, bswap32, bswap64};
@ -169,151 +170,238 @@ pub unsafe fn move_val_init<T>(dst: &mut T, src: T) {
ptr::write(dst, src)
}
/// Convert an u16 to little endian from the target's endianness.
///
/// On little endian, this is a no-op. On big endian, the bytes are swapped.
#[cfg(target_endian = "little")] #[inline] pub fn to_le16(x: u16) -> u16 { x }
/// A type that can have its bytes re-ordered.
pub trait ByteOrder: Clone {
/// Reverses the byte order of the value.
///
/// # Example
///
/// ```rust
/// use std::mem::ByteOrder;
///
/// let n = 0x0123456789ABCDEFu64;
/// let m = 0xEFCDAB8967452301u64;
///
/// assert_eq!(n.swap_bytes(), m);
/// ```
fn swap_bytes(&self) -> Self;
/// Convert a value from big endian to the target's endianness.
///
/// On big endian this is a no-op. On little endian the bytes are swapped.
///
/// # Example
///
/// ```rust
/// use std::mem::ByteOrder;
///
/// let n = 0x0123456789ABCDEFu64;
///
/// if cfg!(target_endian = "big") {
/// assert_eq!(ByteOrder::from_big_endian(n), n)
/// } else {
/// assert_eq!(ByteOrder::from_big_endian(n), n.swap_bytes())
/// }
/// ```
#[inline]
fn from_big_endian(x: Self) -> Self {
if cfg!(target_endian = "big") { x } else { x.swap_bytes() }
}
/// Convert a value from little endian to the target's endianness.
///
/// On little endian this is a no-op. On big endian the bytes are swapped.
///
/// # Example
///
/// ```rust
/// use std::mem::ByteOrder;
///
/// let n = 0x0123456789ABCDEFu64;
///
/// if cfg!(target_endian = "little") {
/// assert_eq!(ByteOrder::from_little_endian(n), n)
/// } else {
/// assert_eq!(ByteOrder::from_little_endian(n), n.swap_bytes())
/// }
/// ```
#[inline]
fn from_little_endian(x: Self) -> Self {
if cfg!(target_endian = "little") { x } else { x.swap_bytes() }
}
/// Convert the value to big endian from the target's endianness.
///
/// On big endian this is a no-op. On little endian the bytes are swapped.
///
/// # Example
///
/// ```rust
/// use std::mem::ByteOrder;
///
/// let n = 0x0123456789ABCDEFu64;
///
/// if cfg!(target_endian = "big") {
/// assert_eq!(n.to_big_endian(), n)
/// } else {
/// assert_eq!(n.to_big_endian(), n.swap_bytes())
/// }
/// ```
#[inline]
fn to_big_endian(&self) -> Self {
if cfg!(target_endian = "big") { self.clone() } else { self.swap_bytes() }
}
/// Convert the value to little endian from the target's endianness.
///
/// On little endian this is a no-op. On big endian the bytes are swapped.
///
/// # Example
///
/// ```rust
/// use std::mem::ByteOrder;
///
/// let n = 0x0123456789ABCDEFu64;
///
/// if cfg!(target_endian = "little") {
/// assert_eq!(n.to_little_endian(), n)
/// } else {
/// assert_eq!(n.to_little_endian(), n.swap_bytes())
/// }
/// ```
#[inline]
fn to_little_endian(&self) -> Self {
if cfg!(target_endian = "little") { self.clone() } else { self.swap_bytes() }
}
}
impl ByteOrder for u8 {
#[inline]
fn swap_bytes(&self) -> u8 {
*self // swapping a single byte does nothing
}
}
impl ByteOrder for u16 {
#[inline]
fn swap_bytes(&self) -> u16 {
unsafe { intrinsics::bswap16(*self) }
}
}
impl ByteOrder for u32 {
#[inline]
fn swap_bytes(&self) -> u32 {
unsafe { intrinsics::bswap32(*self) }
}
}
impl ByteOrder for u64 {
#[inline]
fn swap_bytes(&self) -> u64 {
unsafe { intrinsics::bswap64(*self) }
}
}
#[cfg(target_word_size = "32")]
impl ByteOrder for uint {
#[inline]
fn swap_bytes(&self) -> uint {
(*self as u32).swap_bytes() as uint
}
}
#[cfg(target_word_size = "64")]
impl ByteOrder for uint {
#[inline]
fn swap_bytes(&self) -> uint {
(*self as u64).swap_bytes() as uint
}
}
/// Convert an u16 to little endian from the target's endianness.
///
/// On little endian, this is a no-op. On big endian, the bytes are swapped.
#[cfg(target_endian = "big")] #[inline] #[stable]
pub fn to_le16(x: u16) -> u16 { unsafe { bswap16(x) } }
#[inline]
#[stable]
pub fn to_le16(x: u16) -> u16 { x.to_little_endian() }
/// Convert an u32 to little endian from the target's endianness.
///
/// On little endian, this is a no-op. On big endian, the bytes are swapped.
#[cfg(target_endian = "little")] #[inline] #[stable]
pub fn to_le32(x: u32) -> u32 { x }
/// Convert an u32 to little endian from the target's endianness.
///
/// On little endian, this is a no-op. On big endian, the bytes are swapped.
#[cfg(target_endian = "big")] #[inline] #[stable]
pub fn to_le32(x: u32) -> u32 { unsafe { bswap32(x) } }
#[inline]
#[stable]
pub fn to_le32(x: u32) -> u32 { x.to_little_endian() }
/// Convert an u64 to little endian from the target's endianness.
///
/// On little endian, this is a no-op. On big endian, the bytes are swapped.
#[cfg(target_endian = "little")] #[inline] #[stable]
pub fn to_le64(x: u64) -> u64 { x }
/// Convert an u64 to little endian from the target's endianness.
///
/// On little endian, this is a no-op. On big endian, the bytes are swapped.
#[cfg(target_endian = "big")] #[inline] #[stable]
pub fn to_le64(x: u64) -> u64 { unsafe { bswap64(x) } }
#[inline]
#[stable]
pub fn to_le64(x: u64) -> u64 { x.to_little_endian() }
/// Convert an u16 to big endian from the target's endianness.
///
/// On big endian, this is a no-op. On little endian, the bytes are swapped.
#[cfg(target_endian = "little")] #[inline] #[stable]
pub fn to_be16(x: u16) -> u16 { unsafe { bswap16(x) } }
/// Convert an u16 to big endian from the target's endianness.
///
/// On big endian, this is a no-op. On little endian, the bytes are swapped.
#[cfg(target_endian = "big")] #[inline] #[stable]
pub fn to_be16(x: u16) -> u16 { x }
#[inline]
#[stable]
pub fn to_be16(x: u16) -> u16 { x.to_big_endian() }
/// Convert an u32 to big endian from the target's endianness.
///
/// On big endian, this is a no-op. On little endian, the bytes are swapped.
#[cfg(target_endian = "little")] #[inline] #[stable]
pub fn to_be32(x: u32) -> u32 { unsafe { bswap32(x) } }
/// Convert an u32 to big endian from the target's endianness.
///
/// On big endian, this is a no-op. On little endian, the bytes are swapped.
#[cfg(target_endian = "big")] #[inline] #[stable]
pub fn to_be32(x: u32) -> u32 { x }
#[inline]
#[stable]
pub fn to_be32(x: u32) -> u32 { x.to_big_endian() }
/// Convert an u64 to big endian from the target's endianness.
///
/// On big endian, this is a no-op. On little endian, the bytes are swapped.
#[cfg(target_endian = "little")] #[inline] #[stable]
pub fn to_be64(x: u64) -> u64 { unsafe { bswap64(x) } }
/// Convert an u64 to big endian from the target's endianness.
///
/// On big endian, this is a no-op. On little endian, the bytes are swapped.
#[cfg(target_endian = "big")] #[inline] #[stable]
pub fn to_be64(x: u64) -> u64 { x }
#[inline]
#[stable]
pub fn to_be64(x: u64) -> u64 { x.to_big_endian() }
/// Convert an u16 from little endian to the target's endianness.
///
/// On little endian, this is a no-op. On big endian, the bytes are swapped.
#[cfg(target_endian = "little")] #[inline] #[stable]
pub fn from_le16(x: u16) -> u16 { x }
/// Convert an u16 from little endian to the target's endianness.
///
/// On little endian, this is a no-op. On big endian, the bytes are swapped.
#[cfg(target_endian = "big")] #[inline] #[stable]
pub fn from_le16(x: u16) -> u16 { unsafe { bswap16(x) } }
#[inline]
#[stable]
pub fn from_le16(x: u16) -> u16 { ByteOrder::from_little_endian(x) }
/// Convert an u32 from little endian to the target's endianness.
///
/// On little endian, this is a no-op. On big endian, the bytes are swapped.
#[cfg(target_endian = "little")] #[inline] #[stable]
pub fn from_le32(x: u32) -> u32 { x }
/// Convert an u32 from little endian to the target's endianness.
///
/// On little endian, this is a no-op. On big endian, the bytes are swapped.
#[cfg(target_endian = "big")] #[inline] #[stable]
pub fn from_le32(x: u32) -> u32 { unsafe { bswap32(x) } }
#[inline]
#[stable]
pub fn from_le32(x: u32) -> u32 { ByteOrder::from_little_endian(x) }
/// Convert an u64 from little endian to the target's endianness.
///
/// On little endian, this is a no-op. On big endian, the bytes are swapped.
#[cfg(target_endian = "little")] #[inline] #[stable]
pub fn from_le64(x: u64) -> u64 { x }
/// Convert an u64 from little endian to the target's endianness.
///
/// On little endian, this is a no-op. On big endian, the bytes are swapped.
#[cfg(target_endian = "big")] #[inline] #[stable]
pub fn from_le64(x: u64) -> u64 { unsafe { bswap64(x) } }
#[inline]
#[stable]
pub fn from_le64(x: u64) -> u64 { ByteOrder::from_little_endian(x) }
/// Convert an u16 from big endian to the target's endianness.
///
/// On big endian, this is a no-op. On little endian, the bytes are swapped.
#[cfg(target_endian = "little")] #[inline] #[stable]
pub fn from_be16(x: u16) -> u16 { unsafe { bswap16(x) } }
/// Convert an u16 from big endian to the target's endianness.
///
/// On big endian, this is a no-op. On little endian, the bytes are swapped.
#[cfg(target_endian = "big")] #[inline] #[stable]
pub fn from_be16(x: u16) -> u16 { x }
#[inline]
#[stable]
pub fn from_be16(x: u16) -> u16 { ByteOrder::from_big_endian(x) }
/// Convert an u32 from big endian to the target's endianness.
///
/// On big endian, this is a no-op. On little endian, the bytes are swapped.
#[cfg(target_endian = "little")] #[inline] #[stable]
pub fn from_be32(x: u32) -> u32 { unsafe { bswap32(x) } }
/// Convert an u32 from big endian to the target's endianness.
///
/// On big endian, this is a no-op. On little endian, the bytes are swapped.
#[cfg(target_endian = "big")] #[inline] #[stable]
pub fn from_be32(x: u32) -> u32 { x }
#[inline]
#[stable]
pub fn from_be32(x: u32) -> u32 { ByteOrder::from_big_endian(x) }
/// Convert an u64 from big endian to the target's endianness.
///
/// On big endian, this is a no-op. On little endian, the bytes are swapped.
#[cfg(target_endian = "little")] #[inline] #[stable]
pub fn from_be64(x: u64) -> u64 { unsafe { bswap64(x) } }
/// Convert an u64 from big endian to the target's endianness.
///
/// On big endian, this is a no-op. On little endian, the bytes are swapped.
#[cfg(target_endian = "big")] #[inline] #[stable]
pub fn from_be64(x: u64) -> u64 { x }
#[inline]
#[stable]
pub fn from_be64(x: u64) -> u64 { ByteOrder::from_big_endian(x) }
/**
* Swap the values at two mutable locations of the same type, without
@ -558,6 +646,60 @@ mod tests {
assert!(Vec::from_slice([76u8]) == transmute("L".to_string()));
}
}
macro_rules! test_byte_order {
($T:ident) => {
mod $T {
use mem::ByteOrder;
static A: $T = 0b0101100;
static B: $T = 0b0100001;
static C: $T = 0b1111001;
static _0: $T = 0;
static _1: $T = !0;
#[test]
fn test_swap_bytes() {
assert_eq!(A.swap_bytes().swap_bytes(), A);
assert_eq!(B.swap_bytes().swap_bytes(), B);
assert_eq!(C.swap_bytes().swap_bytes(), C);
// Swapping these should make no difference
assert_eq!(_0.swap_bytes(), _0);
assert_eq!(_1.swap_bytes(), _1);
}
#[test]
fn test_little_endian() {
assert_eq!(ByteOrder::from_little_endian(A.to_little_endian()), A);
assert_eq!(ByteOrder::from_little_endian(B.to_little_endian()), B);
assert_eq!(ByteOrder::from_little_endian(C.to_little_endian()), C);
assert_eq!(ByteOrder::from_little_endian(_0), _0);
assert_eq!(ByteOrder::from_little_endian(_1), _1);
assert_eq!(_0.to_little_endian(), _0);
assert_eq!(_1.to_little_endian(), _1);
}
#[test]
fn test_big_endian() {
assert_eq!(ByteOrder::from_big_endian(A.to_big_endian()), A);
assert_eq!(ByteOrder::from_big_endian(B.to_big_endian()), B);
assert_eq!(ByteOrder::from_big_endian(C.to_big_endian()), C);
assert_eq!(ByteOrder::from_big_endian(_0), _0);
assert_eq!(ByteOrder::from_big_endian(_1), _1);
assert_eq!(_0.to_big_endian(), _0);
assert_eq!(_1.to_big_endian(), _1);
}
}
}
}
test_byte_order!(u8)
test_byte_order!(u16)
test_byte_order!(u32)
test_byte_order!(u64)
test_byte_order!(uint)
}
// FIXME #13642 (these benchmarks should be in another place)

11
src/libcore/num/int_macros.rs
View File

@ -113,17 +113,6 @@ mod tests {
assert!((0b1111001 as $T).count_zeros() == BITS as $T - 5);
}
#[test]
fn test_swap_bytes() {
let n: $T = 0b0101100; assert_eq!(n.swap_bytes().swap_bytes(), n);
let n: $T = 0b0100001; assert_eq!(n.swap_bytes().swap_bytes(), n);
let n: $T = 0b1111001; assert_eq!(n.swap_bytes().swap_bytes(), n);
// Swapping these should make no difference
let n: $T = 0; assert_eq!(n.swap_bytes(), n);
let n: $T = -1; assert_eq!(n.swap_bytes(), n);
}
#[test]
fn test_rotate() {
let n: $T = 0b0101100; assert_eq!(n.rotate_left(6).rotate_right(2).rotate_right(4), n);

72
src/libcore/num/mod.rs
View File

@ -437,19 +437,6 @@ pub trait Bitwise: Bounded
/// ```
fn trailing_zeros(&self) -> Self;
/// Reverses the byte order of a binary number.
///
/// # Example
///
/// ```rust
/// use std::num::Bitwise;
///
/// let n = 0x0123456789ABCDEFu64;
/// let m = 0xEFCDAB8967452301u64;
/// assert_eq!(n.swap_bytes(), m);
/// ```
fn swap_bytes(&self) -> Self;
/// Shifts the bits to the left by a specified amount amount, `r`, wrapping
/// the truncated bits to the end of the resulting value.
///
@ -479,25 +466,17 @@ pub trait Bitwise: Bounded
fn rotate_right(&self, r: uint) -> Self;
}
/// Swapping a single byte does nothing. This is unsafe to be consistent with
/// the other `bswap` intrinsics.
#[inline]
unsafe fn bswap8(x: u8) -> u8 { x }
macro_rules! bitwise_impl(
($t:ty, $bits:expr, $co:ident, $lz:ident, $tz:ident, $bs:path) => {
macro_rules! bitwise_impl {
($t:ty, $bits:expr, $co:path, $lz:path, $tz:path) => {
impl Bitwise for $t {
#[inline]
fn count_ones(&self) -> $t { unsafe { intrinsics::$co(*self) } }
fn count_ones(&self) -> $t { unsafe { $co(*self) } }
#[inline]
fn leading_zeros(&self) -> $t { unsafe { intrinsics::$lz(*self) } }
fn leading_zeros(&self) -> $t { unsafe { $lz(*self) } }
#[inline]
fn trailing_zeros(&self) -> $t { unsafe { intrinsics::$tz(*self) } }
#[inline]
fn swap_bytes(&self) -> $t { unsafe { $bs(*self) } }
fn trailing_zeros(&self) -> $t { unsafe { $tz(*self) } }
#[inline]
fn rotate_left(&self, r: uint) -> $t {
@ -514,22 +493,19 @@ macro_rules! bitwise_impl(
}
}
}
)
}
macro_rules! bitwise_cast_impl(
($t:ty, $t_cast:ty, $bits:expr, $co:ident, $lz:ident, $tz:ident, $bs:path) => {
macro_rules! bitwise_cast_impl {
($t:ty, $t_cast:ty, $bits:expr, $co:path, $lz:path, $tz:path) => {
impl Bitwise for $t {
#[inline]
fn count_ones(&self) -> $t { unsafe { intrinsics::$co(*self as $t_cast) as $t } }
fn count_ones(&self) -> $t { unsafe { $co(*self as $t_cast) as $t } }
#[inline]
fn leading_zeros(&self) -> $t { unsafe { intrinsics::$lz(*self as $t_cast) as $t } }
fn leading_zeros(&self) -> $t { unsafe { $lz(*self as $t_cast) as $t } }
#[inline]
fn trailing_zeros(&self) -> $t { unsafe { intrinsics::$tz(*self as $t_cast) as $t } }
#[inline]
fn swap_bytes(&self) -> $t { unsafe { $bs(*self as $t_cast) as $t } }
fn trailing_zeros(&self) -> $t { unsafe { $tz(*self as $t_cast) as $t } }
#[inline]
fn rotate_left(&self, r: uint) -> $t {
@ -544,27 +520,27 @@ macro_rules! bitwise_cast_impl(
}
}
}
)
}
#[cfg(target_word_size = "32")]
bitwise_cast_impl!(uint, u32, 32, ctpop32, ctlz32, cttz32, intrinsics::bswap32)
bitwise_cast_impl!(uint, u32, 32, intrinsics::ctpop32, intrinsics::ctlz32, intrinsics::cttz32)
#[cfg(target_word_size = "64")]
bitwise_cast_impl!(uint, u64, 64, ctpop64, ctlz64, cttz64, intrinsics::bswap64)
bitwise_cast_impl!(uint, u64, 64, intrinsics::ctpop64, intrinsics::ctlz64, intrinsics::cttz64)
bitwise_impl!(u8, 8, ctpop8, ctlz8, cttz8, bswap8)
bitwise_impl!(u16, 16, ctpop16, ctlz16, cttz16, intrinsics::bswap16)
bitwise_impl!(u32, 32, ctpop32, ctlz32, cttz32, intrinsics::bswap32)
bitwise_impl!(u64, 64, ctpop64, ctlz64, cttz64, intrinsics::bswap64)
bitwise_impl!(u8, 8, intrinsics::ctpop8, intrinsics::ctlz8, intrinsics::cttz8)
bitwise_impl!(u16, 16, intrinsics::ctpop16, intrinsics::ctlz16, intrinsics::cttz16)
bitwise_impl!(u32, 32, intrinsics::ctpop32, intrinsics::ctlz32, intrinsics::cttz32)
bitwise_impl!(u64, 64, intrinsics::ctpop64, intrinsics::ctlz64, intrinsics::cttz64)
#[cfg(target_word_size = "32")]
bitwise_cast_impl!(int, u32, 32, ctpop32, ctlz32, cttz32, intrinsics::bswap32)
bitwise_cast_impl!(int, u32, 32, intrinsics::ctpop32, intrinsics::ctlz32, intrinsics::cttz32)
#[cfg(target_word_size = "64")]
bitwise_cast_impl!(int, u64, 64, ctpop64, ctlz64, cttz64, intrinsics::bswap64)
bitwise_cast_impl!(int, u64, 64, intrinsics::ctpop64, intrinsics::ctlz64, intrinsics::cttz64)
bitwise_cast_impl!(i8, u8, 8, ctpop8, ctlz8, cttz8, bswap8)
bitwise_cast_impl!(i16, u16, 16, ctpop16, ctlz16, cttz16, intrinsics::bswap16)
bitwise_cast_impl!(i32, u32, 32, ctpop32, ctlz32, cttz32, intrinsics::bswap32)
bitwise_cast_impl!(i64, u64, 64, ctpop64, ctlz64, cttz64, intrinsics::bswap64)
bitwise_cast_impl!(i8, u8, 8, intrinsics::ctpop8, intrinsics::ctlz8, intrinsics::cttz8)
bitwise_cast_impl!(i16, u16, 16, intrinsics::ctpop16, intrinsics::ctlz16, intrinsics::cttz16)
bitwise_cast_impl!(i32, u32, 32, intrinsics::ctpop32, intrinsics::ctlz32, intrinsics::cttz32)
bitwise_cast_impl!(i64, u64, 64, intrinsics::ctpop64, intrinsics::ctlz64, intrinsics::cttz64)
/// Specifies the available operations common to all of Rust's core numeric primitives.
/// These may not always make sense from a purely mathematical point of view, but

11
src/libcore/num/uint_macros.rs
View File

@ -64,17 +64,6 @@ mod tests {
assert!((0b1111001 as $T).count_zeros() == BITS as $T - 5);
}
#[test]
fn test_swap_bytes() {
let n: $T = 0b0101100; assert_eq!(n.swap_bytes().swap_bytes(), n);
let n: $T = 0b0100001; assert_eq!(n.swap_bytes().swap_bytes(), n);
let n: $T = 0b1111001; assert_eq!(n.swap_bytes().swap_bytes(), n);
// Swapping these should make no difference
let n: $T = 0; assert_eq!(n.swap_bytes(), n);
let n: $T = MAX; assert_eq!(n.swap_bytes(), n);
}
#[test]
fn test_rotate() {
let n: $T = 0b0101100; assert_eq!(n.rotate_left(6).rotate_right(2).rotate_right(4), n);