From 2de221e1663dc050f3c4be35c9ac26475789069a Mon Sep 17 00:00:00 2001
From: Alex Helfet <alex.helfet@gmail.com>
Date: Thu, 21 Dec 2017 03:07:57 +0000
Subject: [PATCH] Move `Channel` into its own module and test it.

---
 src/channel.rs | 105 +++++++++++++++++++++++++++++++++++++++++++++++++
 src/lib.rs     |  67 ++-----------------------------
 2 files changed, 108 insertions(+), 64 deletions(-)
 create mode 100644 src/channel.rs

diff --git a/src/channel.rs b/src/channel.rs
new file mode 100644
index 0000000..1876dc6
--- /dev/null
+++ b/src/channel.rs
@@ -0,0 +1,105 @@
+//! Vec-backed FIFO buffer of bytes for testing.
+
+use std::cell::RefCell;
+use std::io::{Read, Result, Write};
+use std::rc::Rc;
+
+/// Entry point for the module that can construct multiple `Reader`
+/// and `Writer` endpoints using the same backing store.
+pub struct Channel {
+    inner: Rc<RefCell<Inner>>,
+}
+
+struct Inner {
+    v: Vec<u8>,
+    read_pos: usize,
+}
+
+/// Implements `io::Read`, returning data previously written to a
+/// `Writer` instance from the same `Channel`.
+pub struct Reader {
+    inner: Rc<RefCell<Inner>>,
+}
+
+/// Implements `io::Write`, writing data to an underlying `Channel`.
+pub struct Writer {
+    inner: Rc<RefCell<Inner>>,
+}
+
+impl Channel {
+    /// Construct a new `Channel`.
+    pub fn new() -> Channel {
+        Channel {
+            inner: Rc::new(RefCell::new(Inner {
+                v: Vec::new(),
+                read_pos: 0
+            }))
+        }
+    }
+
+    /// Construct a new `Reader` for this `Channel`.
+    pub fn reader(&self) -> Reader {
+        Reader {
+            inner: self.inner.clone(),
+        }
+    }
+
+    /// Construct a new `Writer` for this `Channel`.
+    pub fn writer(&self) -> Writer {
+        Writer {
+            inner: self.inner.clone(),
+        }
+    }
+}
+
+impl Read for Reader {
+    fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
+        let mut inner = self.inner.borrow_mut();
+        let pos = inner.read_pos;
+        assert!(inner.v.len() >= pos);
+
+        let left = inner.v.len() - pos;
+        let len = buf.len().min(left);
+
+        buf[0..len].copy_from_slice(&inner.v[pos..pos + len]);
+        let new_pos = pos + len;
+        assert!(inner.v.len() >= new_pos);
+        inner.read_pos = new_pos;
+
+        Ok(len)
+    }
+}
+
+impl Write for Writer {
+    fn write(&mut self, buf: &[u8]) -> Result<usize> {
+        self.inner.borrow_mut().v.extend_from_slice(buf);
+        Ok(buf.len())
+    }
+
+    fn flush(&mut self) -> Result<()> {
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::io::{Read, Write};
+    use super::Channel;
+
+    #[test]
+    fn ok() {
+        let c = Channel::new();
+        let mut tx = c.writer();
+        let mut rx = c.reader();
+
+        let mut buf = [0u8; 5];
+
+        assert_eq!(rx.read(&mut buf).unwrap(), 0);
+
+        assert_eq!(tx.write(&[1, 2, 3]).unwrap(), 3);
+        assert_eq!(rx.read(&mut buf[0..1]).unwrap(), 1);
+        assert_eq!(buf, [1, 0, 0, 0, 0]);
+        assert_eq!(rx.read(&mut buf[1..5]).unwrap(), 2);
+        assert_eq!(buf, [1, 2, 3, 0, 0]);
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index c292d96..12380b0 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -17,6 +17,8 @@
 #[macro_use]
 extern crate error_chain;
 
+pub mod channel;
+
 pub mod error;
 use error::{Result};
 use std::io::{Read, Write};
@@ -57,6 +59,7 @@ impl<R: Read> Receiver<R> {
 
 #[cfg(test)]
 mod tests {
+    use channel::Channel;
     use std::io::{Read, Write};
     use super::{Receiver, Sender};
 
@@ -75,68 +78,4 @@ mod tests {
         let rx = Receiver::new(c.reader());
         (tx, rx)
     }
-
-    use self::channel::Channel;
-
-    mod channel {
-        use std::io::{Read, Result, Write};
-        use std::rc::Rc;
-
-        /// A Vec-backed buffer that can be read from and written to.
-        pub struct Channel {
-            inner: Rc<Inner>,
-        }
-
-        struct Inner {
-            _v: Vec<u8>,
-            _read_pos: usize,
-        }
-
-        pub struct Reader {
-            _inner: Rc<Inner>,
-        }
-
-        pub struct Writer {
-            _inner: Rc<Inner>,
-        }
-
-        impl Channel {
-            pub fn new() -> Channel {
-                Channel {
-                    inner: Rc::new(Inner {
-                        _v: Vec::new(),
-                        _read_pos: 0
-                    })
-                }
-            }
-
-            pub fn reader(&self) -> Reader {
-                Reader {
-                    _inner: self.inner.clone(),
-                }
-            }
-
-            pub fn writer(&self) -> Writer {
-                Writer {
-                    _inner: self.inner.clone(),
-                }
-            }
-        }
-
-        impl Read for Reader {
-            fn read(&mut self, _buf: &mut [u8]) -> Result<usize> {
-                unimplemented!()
-            }
-        }
-
-        impl Write for Writer {
-            fn write(&mut self, _buf: &[u8]) -> Result<usize> {
-                unimplemented!()
-            }
-
-            fn flush(&mut self) -> Result<()> {
-                unimplemented!()
-            }
-        }
-    }
 }