Start working on pipe_chan

1 files changed, 81 insertions, 0 deletions

diff --git a/alsa/src/communication/pipe_chan.rs b/alsa/src/communication/pipe_chan.rs
new file mode 100644
index 0000000..1a671ea
--- /dev/null
+++ b/alsa/src/communication/pipe_chan.rs
@@ -0,0 +1,81 @@
+use std::{ffi::{c_int, c_void}, fmt::Display, error::Error};
+use libc::{read, close, pipe2, O_NONBLOCK, EINTR };
+use errno::{errno, set_errno, Errno}; //Why isn't this in libc?!?
+
+/// Sends byte data to the corresponding receiver.
+pub(crate) struct Sender {
+    handle : FileHandle,
+}
+/// Receives byte data from the corresponding sender.
+pub(crate) struct Receiver {
+    handle : FileHandle,
+}
+
+impl Receiver {
+    pub(crate) fn read_byte(&self) -> Result<Option<u8>, ReceiveError> {
+        set_errno(Errno(0));
+        let mut buf : u8 = 0;
+        let status = unsafe {read(self.handle.get_raw(),&mut buf as *mut u8 as *mut c_void, 1)};
+        if status == 0 {
+            //need to check errno. if a signal interrupted, then there is no error and we just
+            //retry.
+            //If no error happened, then the sender has hung up and we return err.
+            let e = errno();
+            if e == Errno(0) {
+                Err(ReceiveError::SenderHasHungUp)
+            } else if e.0 == EINTR {
+                self.read_byte()
+            } else {
+                //Not sure what to do
+                todo!()
+            }
+        }
+        else {
+            todo!()
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+pub(crate) enum ReceiveError {
+    SenderHasHungUp
+}
+
+impl Display for ReceiveError{
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "Read failed, Sender has closed their end of the pipe.")
+    }
+}
+
+impl Error for ReceiveError {}
+
+pub(crate) fn create_pipe_chan() -> Result<(Sender, Receiver),()> {
+    let mut handles : [c_int;2] = [0;2];
+    let result = unsafe { pipe2(handles.as_mut_ptr(), O_NONBLOCK) };
+    if result == -1 { 
+        Err(())
+    } else {
+        Ok((
+            Sender{handle : FileHandle{raw : handles[1]}},
+            Receiver{handle : FileHandle{ raw : handles[0]}}
+        ))
+    }
+}
+
+struct FileHandle {
+    raw : c_int,
+}
+
+impl FileHandle {
+    pub(crate) fn get_raw(&self) -> c_int {
+        self.raw
+    }
+}
+
+impl Drop for FileHandle {
+    fn drop(&mut self) {
+        unsafe {
+            close(self.raw);
+        }
+    }
+}