From 71da5e610f0a2c77af00f18604e9efc1958d3996 Mon Sep 17 00:00:00 2001
From: Avril <flanchan@cumallover.me>
Date: Wed, 2 Nov 2022 18:21:48 +0000
Subject: [PATCH] Added io::Read/Write impls for `ManagedFD` and `MemoryFile`.
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Fortune for mapped-file's current commit: Small blessing − 小吉
---
 Cargo.toml          |  2 +-
 src/file/managed.rs |  4 +-
 src/file/memory.rs  |  4 +-
 src/file/raw.rs     | 90 +++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 95 insertions(+), 5 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index a99239f..84b2673 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -2,7 +2,7 @@
 name = "mapped-file"
 description = "Construct a memory mapping over any file object"
 keywords = ["unix", "mmap", "generic", "file", "fd"]
-version = "0.0.4"
+version = "0.0.5"
 edition = "2021"
 repository="https://github.com/notflan/mapped-file"
 license="MIT"
diff --git a/src/file/managed.rs b/src/file/managed.rs
index 2b1071b..b9bdb86 100644
--- a/src/file/managed.rs
+++ b/src/file/managed.rs
@@ -24,8 +24,6 @@ impl Clone for ManagedFD {
     }
 }
 
-//TODO: io::Read/io::Write impls for ManagedFD
-
 impl ManagedFD
 {
     #[inline] 
@@ -115,3 +113,5 @@ impl From<ManagedFD> for std::fs::File
 	}
     }
 }
+
+raw::impl_io_for_fd!(ManagedFD => .0.get());
diff --git a/src/file/memory.rs b/src/file/memory.rs
index 8702a8c..9dfbba2 100644
--- a/src/file/memory.rs
+++ b/src/file/memory.rs
@@ -79,7 +79,7 @@ impl ops::Deref for NamedMemoryFile
     }
 }
 
-//TODO: impl `MemoryFile` (memfd_create() fd wrapper)
+//impl `MemoryFile` (memfd_create() fd wrapper)
 impl MemoryFile
 {
     /// Create a new, empty, memory file with no name and no flags.
@@ -234,4 +234,4 @@ impl From<MemoryFile> for std::fs::File
     }
 }
 
-//TODO: io::Read/io::Write impls for MemoryFile
+raw::impl_io_for_fd!(MemoryFile => .0.as_raw_fd());
diff --git a/src/file/raw.rs b/src/file/raw.rs
index 3e0f32a..0aa1c0c 100644
--- a/src/file/raw.rs
+++ b/src/file/raw.rs
@@ -117,3 +117,93 @@ impl From<i32> for NonNegativeI32
     }
 }
 
+/// Implements `io::Read` and `io::Write` for a type that implements an accessor for a raw file-descriptor.
+///
+/// Usage:
+/// ```no_compile
+/// struct HasFd(UnmanagedFD);
+/// impl_io_for_fd(HasFd => .0);
+/// ```
+macro_rules! impl_io_for_fd {
+    ($type:ty => .$($fd_path:tt)+) => {
+	const _:() = {
+	    use std::io;
+	    #[inline(always)]
+	    fn check_error() -> bool
+	    {
+		use libc::{
+		    EINTR,
+		    __errno_location,
+		};
+		match unsafe { *__errno_location() } {
+		    EINTR => true,
+		    _ => false,
+		}
+	    }
+	    
+	    impl io::Write for $type
+	    {
+		fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+		    match unsafe { libc::write(self.$($fd_path)+, buf.as_ptr()  as *const _, buf.len()) } {
+			-1 => Err(io::Error::last_os_error()),
+			n => Ok(n as usize)
+		    }
+		}
+		fn write_all(&mut self, mut buf: &[u8]) -> io::Result<()> {
+		    
+		    loop {
+			buf = match buf {
+			    [] => break Ok(()),
+			    buf => {
+				match unsafe{ libc::write(self.$($fd_path)+, buf.as_ptr() as *const _, buf.len()) } {
+				    -1 if check_error() => {
+					return Err(io::Error::last_os_error());
+				    },
+				    -1 => continue,
+				    0 => return Err(io::Error::new(io::ErrorKind::UnexpectedEof, "write returned 0")),
+				    n => &buf[(n as usize)..],
+				}
+			    },
+			};
+		    }
+		}
+		
+		#[inline] 
+		fn flush(&mut self) -> io::Result<()> {
+		    Ok(())
+		}
+	    }
+
+	    impl io::Read for $type
+	    {
+		fn read(&mut self, buf: &mut [u8]) -> io::Result<usize>
+		{
+		    match unsafe { libc::read(self.$($fd_path)+, buf.as_mut_ptr() as *mut _, buf.len()) } {
+			-1 => Err(io::Error::last_os_error()),
+			n => Ok(n as usize),
+		    }
+		}
+		fn read_exact(&mut self, mut buf: &mut [u8]) -> io::Result<()>
+		{
+		    loop {
+			let n = match &mut buf {
+			    [] => break Ok(()),
+			    buf => {
+				match unsafe { libc::read(self.$($fd_path)+, (**buf).as_mut_ptr() as *mut libc::c_void, buf.len()) } {
+				    -1 if check_error() => {
+					return Err(io::Error::last_os_error());
+				    },
+				    -1 => continue,
+				    0 => return Err(io::Error::new(io::ErrorKind::UnexpectedEof, "read returned 0")),
+				    n => n as usize,
+				}
+			    }
+			};
+			buf = &mut buf[n..];
+		    }
+		}
+	    }
+	};
+    };
+}
+pub(super) use impl_io_for_fd;