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use std::{ffi::{c_int, c_void}, fmt::Display, error::Error};
use libc::{read, close, pipe2, O_NONBLOCK, EINTR, EAGAIN, EWOULDBLOCK, EPIPE };
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)};
let e = errno();
if status > 0 {
Ok(Some(buf))
} else if status == 0 && e == Errno(0) {
Err(ReceiveError::SenderHasHungUp)
} else if e.0 == EINTR {
self.read_byte() //got interrupted by a signal, try again.
} else if e.0 == EAGAIN || e.0 == EWOULDBLOCK {
Ok(None) //nothing to receive
} else {
Err(ReceiveError::UnknownError)
}
}
pub(crate) fn file_handle(&self) -> &FileHandle {
&self.handle
}
}
impl Sender {
pub(crate) fn send_byte(&self, byte : u8) -> Result<(), SendError> {
set_errno(Errno(0));
let status = unsafe {libc::write(self.handle.get_raw(), &byte as *const u8 as *const c_void, 1)};
let e = errno();
if status > 0 {
Ok(())
} else if e.0 == EINTR {
self.send_byte(byte) //interrupted, retry
} else if e.0 == EPIPE {
Err(SendError::ReceiverHasHungUp)
} else if e.0 == EAGAIN {
Err(SendError::ChannelFullWouldBlock)
} else {
Err(SendError::UnknownError)
}
}
}
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub(crate) enum SendError{
ReceiverHasHungUp,
ChannelFullWouldBlock,
UnknownError
}
impl Display for SendError {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
match self {
SendError::ReceiverHasHungUp => write!(f, "Write failed, Receiver has closed their end of the pipe."),
SendError::ChannelFullWouldBlock => write!(f, "Write failed, the pipe is clogged."),
SendError::UnknownError => write!(f, "Write failed for unknown reasons. Probably a bug."),
}
}
}
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub(crate) enum ReceiveError {
SenderHasHungUp,
UnknownError,
}
impl Display for ReceiveError{
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
match self {
ReceiveError::SenderHasHungUp => write!(f, "Read failed, Sender has closed their end of the pipe."),
ReceiveError::UnknownError => write!(f, "Read failed for unknown reasons. Probably a bug."),
}
}
}
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]}}
))
}
}
pub(crate) 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);
}
}
}
#[cfg(test)]
mod pipe_chan_test {
use libc::fcntl;
use super::*;
#[test]
fn simple_send_read(){
let (send, recv) = create_pipe_chan().unwrap();
assert_eq!(recv.read_byte(), Ok(None));
send.send_byte(5).unwrap();
send.send_byte(27).unwrap();
assert_eq!(recv.read_byte(), Ok(Some(5)));
assert_eq!(recv.read_byte(), Ok(Some(27)));
assert_eq!(recv.read_byte(), Ok(None));
}
#[test]
fn simple_drop_sender(){
let (send, recv) = create_pipe_chan().unwrap();
assert_eq!(recv.read_byte(), Ok(None));
send.send_byte(5).unwrap();
send.send_byte(27).unwrap();
drop(send);
assert_eq!(recv.read_byte(), Ok(Some(5)));
assert_eq!(recv.read_byte(), Ok(Some(27)));
assert_eq!(recv.read_byte(), Err(ReceiveError::SenderHasHungUp));
}
#[test]
fn simple_drop_receiver(){
let (send, recv) = create_pipe_chan().unwrap();
assert_eq!(recv.read_byte(), Ok(None));
send.send_byte(5).unwrap();
drop(recv);
assert_eq!(send.send_byte(27), Err(SendError::ReceiverHasHungUp));
}
#[test]
fn overfill_sender(){
let (send, recv) = create_pipe_chan().unwrap();
assert_eq!(recv.read_byte(), Ok(None));
let capacity = unsafe {fcntl(send.handle.get_raw(), libc::F_GETPIPE_SZ)};
for _ in 0..capacity {
assert!(send.send_byte(3).is_ok());
}
assert_eq!(send.send_byte(3), Err(SendError::ChannelFullWouldBlock));
}
}
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