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//
// This file defines trait `DecastIO`
//
use crate::{
Cast, Endian, Flip, include_doc,
experimental::AsifBytes,
};
use core::mem;
use std::io;
#[cfg(doc)]
use crate::BE;
#[doc = include_doc!("trait_decast_io.md")]
pub trait DecastIO {
///
/// Decasts a value of type `T` in `value` as a byte representation
/// of type `T`.
///
/// If successful, the resulting bytes are written to `self` using
/// trait [`std::io::Write`] and the number of the bytes is
/// returned in [`Ok`]`(usize)`. On failure, an error value is
/// returned in [`Err`].
///
/// The endianness of the resulting bytes is the same as the
/// endianness of the value in `value`. In typical cases, both
/// are the native endianness.
///
fn decast<T: Cast>(&mut self, value: &T) -> io::Result<usize>;
///
/// Decasts a value of type `T` in `value` as a byte representation
/// of type `T`.
///
/// If successful, the resulting bytes are written to `self` using
/// trait [`std::io::Write`] and the number of the bytes is
/// returned in [`Ok`]`(usize)`. On failure, an error value is
/// returned in [`Err`].
///
/// The resulting bytes are in `endian` on the assumption that the
/// value in `value` is in native-endian.
///
fn decastf<T: Cast + Flip>(
&mut self,
value: &T,
endian: Endian,
) -> io::Result<usize>;
///
/// Decasts values of type `T` in `slice` as byte representations
/// of type `T`.
///
/// If successful, the resulting bytes are written to `self` using
/// trait [`std::io::Write`] and the number of the bytes is
/// returned in [`Ok`]`(usize)`. On failure, an error value is
/// returned in [`Err`].
///
/// The endianness of the resulting bytes is the same as the
/// endianness of the values in `slice`. In typical cases,
/// both are the native endianness.
///
fn decasts<T: Cast>(&mut self, slice: &[T]) -> io::Result<usize>;
///
/// Decasts values of type `T` in `slice` as byte representations
/// of type `T`.
///
/// If successful, the resulting bytes are written to `self` using
/// trait [`std::io::Write`] and the number of the bytes is
/// returned in [`Ok`]`(usize)`. On failure, an error value is
/// returned in [`Err`].
///
/// The resulting bytes are in `endian` on the assumption that the
/// value in `value` is in native-endian.
///
fn decastsf<T: Cast + Flip>(
&mut self,
slice: &[T],
endian: Endian,
) -> io::Result<usize>;
///
/// Is equivalent to [`DecastIO::decasts`].
///
/// This method will be deprecated in a future release.
///
fn decastv<T: Cast>(&mut self, slice: &[T]) -> io::Result<usize>;
///
/// Is equivalent to [`DecastIO::decastsf`].
///
/// This method will be deprecated in a future release.
///
fn decastvf<T: Cast + Flip>(
&mut self,
slice: &[T],
endian: Endian,
) -> io::Result<usize>;
}
impl<W: ?Sized + io::Write> DecastIO for W {
#[inline]
fn decast<T: Cast>(&mut self, value: &T) -> io::Result<usize> {
unsafe {
// SAFETY: The following function call to `io::Write::write_all`
// is safe because those types that implement trait Cast can be
// duplicated simply by copying bits by the definition of trait
// Cast.
self.write_all(value.asif_bytes_ref())?;
}
Ok(mem::size_of_val(value))
}
#[inline]
fn decastf<T: Cast + Flip>(
&mut self,
value: &T,
endian: Endian,
) -> io::Result<usize> {
if !endian.need_swap() {
// The endianness must not be reversed.
self.decast::<T>(value)
} else {
// The endianness must be reversed.
self.decast::<T>(&value.flip_val_swapped())
}
}
#[inline]
fn decasts<T: Cast>(&mut self, slice: &[T]) -> io::Result<usize> {
unsafe {
// SAFETY: The following function call to `io::Write::write_all`
// is safe because those types that implement trait Cast can be
// duplicated simply by copying bits by the definition of trait
// Cast.
self.write_all(slice.asif_bytes_ref())?;
}
Ok(mem::size_of_val(slice))
}
#[inline]
fn decastsf<T: Cast + Flip>(
&mut self,
slice: &[T],
endian: Endian,
) -> io::Result<usize> {
if !endian.need_swap() {
// The endianness must not be reversed.
self.decasts::<T>(slice)
} else {
// The endianness must be reversed.
self.decastsf_swapped(slice)
}
}
#[inline]
fn decastv<T: Cast>(&mut self, slice: &[T]) -> io::Result<usize> {
// `decastv` is equivalent to `decasts`.
self.decasts(slice)
}
#[inline]
fn decastvf<T: Cast + Flip>(
&mut self,
slice: &[T],
endian: Endian,
) -> io::Result<usize> {
// `decastvf` is equivalent to `decastsf`.
self.decastsf(slice, endian)
}
}
///
/// Provides internal methods for trait `DecastIO`.
///
trait DecastIOInternal {
/// Writes the memory representation of the values in `slice` to a
/// writer `self` and returns the number of output bytes in
/// `Ok(usize)`.
///
/// The endianness of the output bytes is the swapped one of the
/// endianness of `slice`.
///
/// If an error is detected, `Err(io::Error)` is returned.
fn decastsf_swapped<T: Cast + Flip>(
&mut self,
slice: &[T],
) -> io::Result<usize>;
}
impl<W: ?Sized + io::Write> DecastIOInternal for W {
fn decastsf_swapped<T: Cast + Flip>(
&mut self,
slice: &[T],
) -> io::Result<usize> {
for elem in slice {
// Read values from `slice`, reverse their endiannesses, then
// write the resulting byte representations to `self`.
self.decast::<T>(&elem.flip_val_swapped())?;
}
Ok(mem::size_of_val(slice))
}
}