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//
// This file defines trait `EncastMem`
//
use crate::{Cast, Endian, Flip, include_doc};
use core::{mem, ptr};
#[cfg(doc)]
use crate::BE;
#[cfg(feature = "alloc")]
use crate::experimental::PushBulk;
#[cfg(feature = "alloc")]
use alloc::vec::Vec;
#[doc = include_doc!("trait_encast_mem.md")]
pub trait EncastMem {
///
/// Encasts a byte representation of type `T` at the head of `self`
/// as a value of type `T`.
///
/// If successful, the resulting value is returned in [`Some`]`(T)`.
/// On failure, [`None`] is returned.
///
/// The endianness of the resulting value is the same as the
/// endianness of the source bytes. In typical cases, both are
/// the native endianness.
///
fn encast<T: Cast>(&self) -> Option<T>;
///
/// Encasts a byte representation of type `T` at the head of `self`
/// as a value of type `T`.
///
/// If successful, the resulting value is returned in [`Some`]`(T)`.
/// On failure, [`None`] is returned.
///
/// The resulting value is in native-endian. The endianness of
/// the source bytes is specified by `endian`.
///
fn encastf<T: Cast + Flip>(&self, endian: Endian) -> Option<T>;
///
/// Encasts a byte representation of type `T` at the head of `self`
/// as values of type `T`.
///
/// If successful, the resulting values are saved in `slice` and
/// the number of the source bytes is returned in [`Some`]`(usize)`.
/// On failure, [`None`] is returned.
///
/// The endianness of each resulting value is the same as the
/// endianness of the corresponding source bytes. In typical
/// cases, all are the native endiannesses.
///
fn encasts<T: Cast>(&self, slice: &mut [T]) -> Option<usize>;
///
/// Encasts a byte representation of type `T` at the head of `self`
/// as values of type `T`.
///
/// If successful, the resulting values are saved in `slice` and
/// the number of the source bytes is returned in [`Some`]`(usize)`.
/// On failure, [`None`] is returned.
///
/// The resulting values are in native-endian. The endianness of
/// the source bytes is specified by `endian`.
///
fn encastsf<T: Cast + Flip>(
&self,
slice: &mut [T],
endian: Endian,
) -> Option<usize>;
///
/// Encasts a byte representation of type `T` at the head of `self`
/// as values of type `T`. The number of values in the source bytes
/// is specified by `len`.
///
/// If successful, the resulting values are returned in
/// [`Some`]`(Vec<T>)`. On failure, [`None`] is returned.
///
/// The endianness of each resulting value is the same as the
/// endianness of the corresponding source bytes. In typical
/// cases, all are the native endiannesses.
///
#[cfg(feature = "alloc")]
fn encastv<T: Cast>(&self, len: usize) -> Option<Vec<T>>;
///
/// Encasts a byte representation of type `T` at the head of `self`
/// as values of type `T`. The number of values in the source bytes
/// is specified by `len`.
///
/// If successful, the resulting values are returned in
/// [`Some`]`(Vec<T>)`. On failure, [`None`] is returned.
///
/// The resulting values are in native-endian. The endianness of
/// the source bytes is specified by `endian`.
///
#[cfg(feature = "alloc")]
fn encastvf<T: Cast + Flip>(
&self,
len: usize,
endian: Endian,
) -> Option<Vec<T>>;
}
impl EncastMem for [u8] {
#[inline]
fn encast<T: Cast>(&self) -> Option<T> {
if self.len() >= mem::size_of::<T>() {
unsafe {
// SAFETY: The following function call to `ptr::read_unaligned`
// is safe because those types that implement trait Cast can be
// duplicated simply by copying bits by the definition of trait
// Cast.
Some(ptr::read_unaligned::<T>(self.as_ptr() as *const T))
}
} else {
None
}
}
#[inline]
fn encastf<T: Cast + Flip>(&self, endian: Endian) -> Option<T> {
let mut value = self.encast::<T>()?;
// Flips the endianness of the value in `value` if `endian` is
// not equivalent to the endianness of the target system.
value.flip_var(endian);
Some(value)
}
#[inline]
fn encasts<T: Cast>(&self, slice: &mut [T]) -> Option<usize> {
let nbytes = mem::size_of_val(slice);
if self.len() >= nbytes {
unsafe {
// SAFETY: The following function call to
// `ptr::copy_nonoverlapping` is safe because those types that
// implement trait Cast can be duplicated simply by copying
// bits by the definition of trait Cast.
ptr::copy_nonoverlapping::<u8>(
self.as_ptr(),
slice.as_mut_ptr() as *mut u8,
nbytes,
);
}
Some(nbytes)
} else {
None
}
}
#[inline]
fn encastsf<T: Cast + Flip>(
&self,
slice: &mut [T],
endian: Endian,
) -> Option<usize> {
if !endian.need_swap() {
// The endianness must not be reversed.
self.encasts::<T>(slice)
} else {
// The endianness must be reversed.
self.encastsf_swapped(slice)
}
}
#[cfg(feature = "alloc")]
fn encastv<T: Cast>(&self, len: usize) -> Option<Vec<T>> {
let mut vec: Vec<T> = Vec::new();
unsafe {
// SAFETY: The following method call to `PushBulk::push_bulk` is
// safe because the closure fills whole elements in `new_slice`.
vec.push_bulk(len, |new_slice| {
self.encasts(new_slice).ok_or(())
}).ok()?;
}
Some(vec)
}
#[cfg(feature = "alloc")]
#[inline]
fn encastvf<T: Cast + Flip>(
&self,
len: usize,
endian: Endian,
) -> Option<Vec<T>> {
if !endian.need_swap() {
// The endianness must not be reversed.
self.encastv::<T>(len)
} else {
// The endianness must be reversed.
self.encastvf_swapped(len)
}
}
}
///
/// Provides internal methods for trait `EncastMem`.
///
trait EncastMemInternal {
///
/// Encasts a byte representation of type `T` at the head of
/// `self` as a value of type `T`.
///
/// If successful, the resulting value is returned in [`Some`]`(T)`.
/// On failure, [`None`] is returned.
///
/// The endianness of each resulting value is the swapped
/// endianness of the corresponding source bytes.
///
fn encastsf_swapped<T: Cast + Flip>(
&self,
slice: &mut [T],
) -> Option<usize>;
///
/// Encasts a byte representation of type `T` at the head of
/// `self` as values of type `T`. The number of values in the
/// source bytes is specified by `len`.
///
/// If successful, the resulting values are returned in
/// [`Some`]`(Vec<T>)`. On failure, [`None`] is returned.
///
/// The endianness of each resulting value is the swapped
/// endianness of the corresponding source bytes.
///
fn encastvf_swapped<T: Cast + Flip>(&self, len: usize) -> Option<Vec<T>>;
}
impl EncastMemInternal for [u8] {
fn encastsf_swapped<T: Cast + Flip>(
&self,
slice: &mut [T],
) -> Option<usize> {
if self.len() >= mem::size_of_val(slice) {
let mut off = 0;
// Read byte representations from `self`, reverse their
// endiannesses, then save the resulting values to `elem`
// in `slice`.
for elem in slice {
*elem = self[off ..].encast::<T>()?.flip_val_swapped();
off += mem::size_of_val(elem);
}
Some(off)
} else {
None
}
}
fn encastvf_swapped<T: Cast + Flip>(&self, len: usize) -> Option<Vec<T>> {
let mut vec: Vec<T> = Vec::new();
unsafe {
// SAFETY: The following method call to `PushBulk::push_bulk` is
// safe because the closure fills whole elements in `new_slice`.
vec.push_bulk(len, |new_slice| {
self.encastsf_swapped(new_slice).ok_or(())
}).ok()?;
}
Some(vec)
}
}