MappedFile: Added `try_new_buffer()`.

Fortune for mapped-file's current commit: Half blessing − 半吉

src/ext.rs

@@ -5,6 +5,10 @@ use std::{
     borrow::{
 	Borrow, BorrowMut
     },
+    mem::{
+	ManuallyDrop,
+	MaybeUninit,
+    },
 };
 
 /// Defer an expression call
@@ -33,16 +37,22 @@ macro_rules! defer {
 pub(crate) use defer;
 
 /// Defer calling `F` until the destructor is ran
-pub struct Deferred<F: ?Sized +  FnOnce() -> ()>(F);
+#[repr(transparent)]
+pub struct Deferred<F: ?Sized +  FnOnce() -> ()>(ManuallyDrop<F>);
 
 /// Defer dropping this value until the container is dropped. The function `F` will be called on the value at drop time.
-pub struct DeferredDrop<T, F: ?Sized + FnOnce(T) -> ()>(T,F);
+pub struct DeferredDrop<T, F: ?Sized + FnOnce(T) -> ()>(T, ManuallyDrop<F>);
 
-impl<F: ?Sized+ FnOnce() -> ()> ops::Drop for Deferred<F>
+impl<F: ?Sized+ (FnOnce() -> ())> ops::Drop for Deferred<F>
 {
     #[inline] 
     fn drop(&mut self) {
-	self.0();
+	todo!("How tf do we get a Box<F> from ManuallyDrop<F>??? We might just have to `transmute()` its `assume_init_mut()` to a higher lifetime");
+	/*let func_ptr = unsafe {
+	    ptr::read(MaybeUninit::assume_init_mut(&mut self.0) as *mut F;
+	    // aosidaosij oijoi jaoile FUCK THIS SHIT, I JUST WANNA CALL THE DAMN THINGt p: *mut F =  ManuallyDrop::borrow_mut(&mut self.0) as *mut _;
+	};
+	func_ptr();*/
     }
 }
 
@@ -50,7 +60,8 @@ impl<T, F: ?Sized+ FnOnce(T) -> ()> ops::Drop for DeferredDrop<T, F>
 {
     #[inline] 
     fn drop(&mut self) {
-	self.1(self.0);
+	todo!("See above...")
+	//self.1(self.0);
     }
 }
 

src/lib.rs

@@ -27,7 +27,7 @@ use ffi::c_try;
 
 
 pub mod hugetlb;
-#[cfg(feature="file")]
+//#[cfg(feature="file")]
 pub mod file;
 
 pub mod ring; //TODO
@@ -135,6 +135,7 @@ impl<T: AsRawFd> MappedFile<T> {
     {
 	Self::try_new_buffer_raw::<B>(file, len, None, false, flags)
     }
+    //TODO: XXX: Test this when we have implemented memfd.
     #[inline] 
     pub(crate) fn try_new_buffer_raw<B: buffer::TwoBufferProvider<T>>(file: T, len: usize, rings: impl Into<Option<std::num::NonZeroUsize>>, allow_unsafe_writes: bool, flags: impl flags::MapFlags) -> Result<(MappedFile<B>, MappedFile<B>), TryNewError<T>>
     {
@@ -228,11 +229,11 @@ impl<T: AsRawFd> MappedFile<T> {
 		let mut root = try_map!(NULL, full_len, libc::PROT_NONE, libc::MAP_PRIVATE | libc::MAP_ANONYMOUS, -1, 0);
 		let pivots = {
 		    let rawfd = file.as_raw_fd();
-		    let pivots: io::Result<Vec<_>> = std::iter::successors(unsafe { Some(root.0.as_mut_ptr().add(full_len)) }, |&x| unsafe { Some(x.sub(len * 2)) }) // Map in reverse, from end of `root`, and overwrite the `root` mapping last.
+		    let pivots: io::Result<Vec<_>> = std::iter::successors(unsafe { Some(root.0.as_mut_ptr().add(full_len - (len * 2))) }, |&x| unsafe { Some(x.sub(len * 2)) }) // Map in reverse, from end of `root`, and overwrite the `root` mapping last.
 			.take(pages.get())
 			.map(|base| {
-			    let tm = try_map_or!(base as *mut _, len, prot_w, flags | libc::MAP_FIXED, rawfd, 0)?;
 			    let rm = try_map_or!(base.add(len) as *mut _, len, prot_r, flags | libc::MAP_FIXED,rawfd, 0 )?;
+			    let tm = try_map_or!(base as *mut _, len, prot_w, flags | libc::MAP_FIXED, rawfd, 0)?;
 
 			    Ok((tm, rm))
 			})

src/ring/buffer.rs

@@ -171,3 +171,47 @@ impl<T: ?Sized> Private<T>
 	&self.0
     }
 }
+
+//TODO: use `dup()` to turn (MappedFile<B>, MappedFile<B>) -> (MappedFile<impl FromRawFd>, MappedFile<impl FromRawFd>)
+
+pub trait BufferExt<T>
+{
+    fn detach(txrx: Self) -> (MappedFile<T>, MappedFile<T>);
+}
+
+impl<B, T> BufferExt<T> for (MappedFile<B>, MappedFile<B>)
+where B: TwoBufferProvider<T> + AsRawFd,
+T: FromRawFd,
+{
+    /// Detach a mapped dual buffer 2-tuple into regular mapped inner types.
+    #[inline] 
+    fn detach((itx, irx): Self) -> (MappedFile<T>, MappedFile<T>) {
+	#[cold]
+	#[inline(never)]
+	fn _panic_bad_dup(fd: RawFd) -> !
+	{
+	    panic!("Failed to dup({fd}): {}", io::Error::last_os_error())
+	}
+	let tx = itx.file.as_raw_fd();
+	let rx = irx.file.as_raw_fd();
+	
+	let (f0, f1) = unsafe {
+	    let fd1 = libc::dup(tx);
+	    if fd1 < 0 {
+		_panic_bad_dup(tx);
+	    }
+	    let fd2 = libc::dup(rx);
+	    if fd2 < 0 {
+		_panic_bad_dup(rx);
+	    }
+	    (T::from_raw_fd(fd1), T::from_raw_fd(fd2))
+	};
+	(MappedFile {
+	    map: itx.map,
+	    file: f0,
+	}, MappedFile {
+	    map: irx.map,
+	    file: f1
+	})
+    }
+}