From 21d1704319fd747f67276149afbd7a285700de20 Mon Sep 17 00:00:00 2001
From: Mathias Gottschlag <mgottschlag@gmail.com>
Date: Thu, 14 May 2020 09:06:21 +0200
Subject: [PATCH] Deduplicate event reading code.

---
 src/async_tokio.rs | 29 +++++------------------
 src/lib.rs         | 59 +++++++++++++++++++++++-----------------------
 2 files changed, 35 insertions(+), 53 deletions(-)

diff --git a/src/async_tokio.rs b/src/async_tokio.rs
index 8f8d873..3c439fb 100644
--- a/src/async_tokio.rs
+++ b/src/async_tokio.rs
@@ -17,13 +17,11 @@ use mio::{PollOpt, Ready, Token};
 use tokio::io::PollEvented;
 
 use std::io;
-use std::mem;
 use std::os::unix::io::AsRawFd;
 use std::pin::Pin;
-use std::slice;
 
 use super::errors::event_err;
-use super::{ffi, LineEvent, LineEventHandle, Result};
+use super::{LineEvent, LineEventHandle, Result};
 
 struct PollWrapper {
     handle: LineEventHandle,
@@ -123,26 +121,11 @@ impl Stream for AsyncLineEventHandle {
             return Poll::Ready(Some(Err(e.into())));
         }
 
-        // TODO: This code should not be duplicated here.
-        let mut data: ffi::gpioevent_data = unsafe { mem::zeroed() };
-        let mut data_as_buf = unsafe {
-            slice::from_raw_parts_mut(
-                &mut data as *mut ffi::gpioevent_data as *mut u8,
-                mem::size_of::<ffi::gpioevent_data>(),
-            )
-        };
-        match nix::unistd::read(
-            self.evented.get_ref().handle.file.as_raw_fd(),
-            &mut data_as_buf,
-        ) {
-            Ok(bytes_read) => {
-                if bytes_read != mem::size_of::<ffi::gpioevent_data>() {
-                    let e = nix::Error::Sys(nix::errno::Errno::EIO);
-                    Poll::Ready(Some(Err(event_err(e))))
-                } else {
-                    Poll::Ready(Some(Ok(LineEvent(data))))
-                }
-            }
+        match self.evented.get_ref().handle.read_event() {
+            Ok(Some(event)) => Poll::Ready(Some(Ok(event))),
+            Ok(None) => Poll::Ready(Some(Err(event_err(nix::Error::Sys(
+                nix::errno::Errno::EIO,
+            ))))),
             Err(nix::Error::Sys(nix::errno::Errno::EAGAIN)) => {
                 self.evented.clear_read_ready(cx, ready)?;
                 Poll::Pending
diff --git a/src/lib.rs b/src/lib.rs
index d91f53f..0fc6f7c 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -950,21 +950,10 @@ impl LineEventHandle {
     /// kernel for the line which matches the subscription criteria
     /// specified in the `event_flags` when the handle was created.
     pub fn get_event(&self) -> Result<LineEvent> {
-        let mut data: ffi::gpioevent_data = unsafe { mem::zeroed() };
-        let mut data_as_buf = unsafe {
-            slice::from_raw_parts_mut(
-                &mut data as *mut ffi::gpioevent_data as *mut u8,
-                mem::size_of::<ffi::gpioevent_data>(),
-            )
-        };
-        let bytes_read =
-            nix::unistd::read(self.file.as_raw_fd(), &mut data_as_buf).map_err(event_err)?;
-
-        if bytes_read != mem::size_of::<ffi::gpioevent_data>() {
-            let e = nix::Error::Sys(nix::errno::Errno::EIO);
-            Err(event_err(e))
-        } else {
-            Ok(LineEvent(data))
+        match self.read_event() {
+            Ok(Some(event)) => Ok(event),
+            Ok(None) => Err(event_err(nix::Error::Sys(nix::errno::Errno::EIO))),
+            Err(e) => Err(event_err(e)),
         }
     }
 
@@ -984,6 +973,28 @@ impl LineEventHandle {
     pub fn line(&self) -> &Line {
         &self.line
     }
+
+    /// Helper function which returns the line event if a complete event was read, Ok(None) if not
+    /// enough data was read or the error returned by `read()`.
+    ///
+    /// This function allows access to the raw `nix::Error` as required, for example, to theck
+    /// whether read() returned -EAGAIN.
+    pub(crate) fn read_event(&self) -> std::result::Result<Option<LineEvent>, nix::Error> {
+        let mut data: ffi::gpioevent_data = unsafe { mem::zeroed() };
+        let mut data_as_buf = unsafe {
+            slice::from_raw_parts_mut(
+                &mut data as *mut ffi::gpioevent_data as *mut u8,
+                mem::size_of::<ffi::gpioevent_data>(),
+            )
+        };
+        let bytes_read = nix::unistd::read(self.file.as_raw_fd(), &mut data_as_buf)?;
+
+        if bytes_read != mem::size_of::<ffi::gpioevent_data>() {
+            Ok(None)
+        } else {
+            Ok(Some(LineEvent(data)))
+        }
+    }
 }
 
 impl AsRawFd for LineEventHandle {
@@ -997,21 +1008,9 @@ impl Iterator for LineEventHandle {
     type Item = Result<LineEvent>;
 
     fn next(&mut self) -> Option<Result<LineEvent>> {
-        let mut data: ffi::gpioevent_data = unsafe { mem::zeroed() };
-        let mut data_as_buf = unsafe {
-            slice::from_raw_parts_mut(
-                &mut data as *mut ffi::gpioevent_data as *mut u8,
-                mem::size_of::<ffi::gpioevent_data>(),
-            )
-        };
-        match nix::unistd::read(self.file.as_raw_fd(), &mut data_as_buf) {
-            Ok(bytes_read) => {
-                if bytes_read != mem::size_of::<ffi::gpioevent_data>() {
-                    None
-                } else {
-                    Some(Ok(LineEvent(data)))
-                }
-            }
+        match self.read_event() {
+            Ok(None) => None,
+            Ok(Some(event)) => Some(Ok(event)),
             Err(e) => Some(Err(event_err(e))),
         }
     }