interprocess 2.2.2

Interprocess communication toolkit
Documentation 
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use super::{c_wrappers, downgrade_eof, winprelude::*};
use crate::{AsMutPtr, OrErrno, SubUsizeExt, TryClone};
use std::{io, mem::MaybeUninit, ptr};
use windows_sys::Win32::{
	Foundation::MAX_PATH,
	Storage::FileSystem::{FlushFileBuffers, GetFinalPathNameByHandleW, ReadFile, WriteFile},
};

/// Newtype wrapper which defines file I/O operations on a handle to a file.
#[repr(transparent)]
pub(crate) struct FileHandle(OwnedHandle);
impl FileHandle {
	pub fn read(&self, buf: &mut [MaybeUninit<u8>]) -> io::Result<usize> {
		let len = u32::try_from(buf.len()).unwrap_or(u32::MAX);

		let mut bytes_read: u32 = 0;
		unsafe {
			ReadFile(
				self.as_int_handle(),
				buf.as_mut_ptr().cast(),
				len,
				bytes_read.as_mut_ptr(),
				ptr::null_mut(),
			)
		}
		.true_val_or_errno(bytes_read.to_usize())
	}
	pub fn write(&self, buf: &[u8]) -> io::Result<usize> {
		let len = u32::try_from(buf.len()).unwrap_or(u32::MAX);

		let mut bytes_written: u32 = 0;
		unsafe {
			WriteFile(
				self.as_int_handle(),
				buf.as_ptr().cast(),
				len,
				bytes_written.as_mut_ptr(),
				ptr::null_mut(),
			)
		}
		.true_val_or_errno(bytes_written.to_usize())
	}
	#[inline(always)]
	pub fn flush(&self) -> io::Result<()> {
		Self::flush_hndl(self.as_int_handle())
	}
	#[inline]
	pub fn flush_hndl(handle: HANDLE) -> io::Result<()> {
		downgrade_eof(unsafe { FlushFileBuffers(handle) }.true_val_or_errno(()))
	}

	// The second arm is unreachable if cap > len.
	#[allow(dead_code, clippy::arithmetic_side_effects)]
	pub fn path(handle: BorrowedHandle<'_>) -> io::Result<Vec<u16>> {
		let mut buf = Vec::with_capacity((MAX_PATH + 1).to_usize());
		match Self::_path(handle.as_int_handle(), &mut buf) {
			(_, Ok(true)) => Ok(buf),
			(len, Ok(false)) => {
				buf.reserve_exact(len - buf.capacity());
				match Self::_path(handle.as_int_handle(), &mut buf) {
					(_, Ok(true)) => Ok(buf),
					(_, Ok(false)) => unreachable!(),
					(_, Err(e)) => Err(e),
				}
			}
			(_, Err(e)) => Err(e),
		}
	}
	#[allow(clippy::arithmetic_side_effects)] // Path lengths can never overflow usize.
	fn _path(handle: HANDLE, buf: &mut Vec<u16>) -> (usize, io::Result<bool>) {
		buf.clear();
		let buflen = buf.capacity().try_into().unwrap_or(u32::MAX);
		let rslt = unsafe { GetFinalPathNameByHandleW(handle, buf.as_mut_ptr(), buflen, 0) };
		let len = rslt.to_usize();
		let e = if rslt >= buflen {
			Ok(false)
		} else if rslt == 0 {
			Err(io::Error::last_os_error())
		} else {
			// +1 to include the nul terminator in the size.
			unsafe { buf.set_len(rslt.to_usize() + 1) }
			Ok(true)
		};
		(len, e)
	}
}
impl TryClone for FileHandle {
	fn try_clone(&self) -> io::Result<Self> {
		c_wrappers::duplicate_handle(self.as_handle()).map(Self)
	}
}

multimacro! {
	FileHandle,
	forward_handle,
	forward_debug,
	derive_raw,
}