From 91aeb39e4c83f6d0794fa6f40f43154544418673 Mon Sep 17 00:00:00 2001
From: Kirill Mironov <vetrokm@gmail.com>
Date: Tue, 20 Aug 2019 14:48:15 +0300
Subject: [PATCH] begin implementing BufWriter

---
 src/io/buf_writer.rs | 140 +++++++++++++++++++++++++++++++++++++++++++
 src/io/mod.rs        |   4 ++
 2 files changed, 144 insertions(+)
 create mode 100644 src/io/buf_writer.rs

diff --git a/src/io/buf_writer.rs b/src/io/buf_writer.rs
new file mode 100644
index 0000000..5755063
--- /dev/null
+++ b/src/io/buf_writer.rs
@@ -0,0 +1,140 @@
+use crate::task::{Context, Poll};
+use futures::{ready, AsyncWrite, Future, Stream};
+use std::io::{self, IntoInnerError};
+use std::pin::Pin;
+use std::fmt;
+use crate::io::Write;
+
+const DEFAULT_CAPACITY: usize = 8 * 1024;
+
+
+pub struct BufWriter<W: AsyncWrite> {
+    inner: Option<W>,
+    buf: Vec<u8>,
+    panicked: bool,
+}
+
+impl<W: AsyncWrite + Unpin> BufWriter<W> {
+    pin_utils::unsafe_pinned!(inner: Option<W>);
+    pin_utils::unsafe_unpinned!(panicked: bool);
+
+    pub fn new(inner: W) -> BufWriter<W> {
+        BufWriter::with_capacity(DEFAULT_CAPACITY, inner)
+    }
+
+    pub fn with_capacity(capacity: usize, inner: W) -> BufWriter<W> {
+        BufWriter {
+            inner: Some(inner),
+            buf: Vec::with_capacity(capacity),
+            panicked: false,
+        }
+    }
+
+    pub fn get_ref(&self) -> &W {
+        self.inner.as_ref().unwrap()
+    }
+
+    pub fn get_mut(&mut self) -> &mut W {
+        self.inner.as_mut().unwrap()
+    }
+
+    pub fn buffer(&self) -> &[u8] {
+        &self.buf
+    }
+
+    pub fn poll_flush_buf(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+        let Self {
+            inner,
+            buf,
+            panicked
+        } = Pin::get_mut(self);
+        let mut panicked = Pin::new(panicked);
+        let mut written = 0;
+        let len = buf.len();
+        let mut ret = Ok(());
+        while written < len {
+            *panicked = true;
+            let r = Pin::new(inner.as_mut().unwrap());
+            *panicked = false;
+            match r.poll_write(cx, &buf[written..]) {
+                Poll::Ready(Ok(0)) => {
+                    ret = Err(io::Error::new(
+                        io::ErrorKind::WriteZero,
+                        "Failed to write buffered data",
+                    ));
+                    break;
+                }
+                Poll::Ready(Ok(n)) => written += n,
+                Poll::Ready(Err(ref e)) if e.kind() == io::ErrorKind::Interrupted => {}
+                Poll::Ready(Err(e)) => {
+                    ret = Err(e);
+                    break;
+                }
+                Poll::Pending => return Poll::Pending,
+            }
+        }
+        if written > 0 {
+            buf.drain(..written);
+        }
+        Poll::Ready(ret)
+    }
+
+    pub fn poll_into_inner(
+        mut self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        //TODO: Fix 'expected function, found struct `IntoInnerError`' compiler error
+    ) -> Poll<io::Result<W>> {
+        match ready!(self.as_mut().poll_flush_buf(cx)) {
+            Ok(()) => Poll::Ready(Ok(self.inner().take().unwrap())),
+            Err(e) => Poll::Ready(Err(io::Error::new(io::ErrorKind::Other, "")))
+        }
+    }
+}
+
+impl<W: AsyncWrite + Unpin> AsyncWrite for BufWriter<W> {
+    fn poll_write(
+        mut self: Pin<&mut Self>,
+        cx: &mut Context,
+        buf: &[u8],
+    ) -> Poll<io::Result<usize>> {
+        let panicked = self.as_mut().panicked();
+        if self.as_ref().buf.len() + buf.len() > self.as_ref().buf.capacity() {
+            match ready!(self.as_mut().poll_flush_buf(cx)) {
+                Ok(()) => {},
+                Err(e) => return Poll::Ready(Err(e))
+            }
+        }
+        if buf.len() >= self.as_ref().buf.capacity() {
+            *panicked = true;
+            let r = ready!(self.as_mut().poll_write(cx, buf));
+            *panicked = false;
+            return Poll::Ready(r)
+        } else {
+            return Poll::Ready(ready!(self.as_ref().buf.write(buf).poll()))
+        }
+    }
+
+    fn poll_flush(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<io::Result<()>> {
+        unimplemented!()
+    }
+
+    fn poll_close(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<io::Result<()>> {
+        unimplemented!()
+    }
+}
+
+impl<W: AsyncWrite + fmt::Debug> fmt::Debug for BufWriter<W> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("BufReader")
+            .field("writer", &self.inner)
+            .field(
+                "buf",
+                &self.buf
+            )
+            .finish()
+    }
+}
+
+mod tests {
+
+}
\ No newline at end of file
diff --git a/src/io/mod.rs b/src/io/mod.rs
index 13b91d6..53dab90 100644
--- a/src/io/mod.rs
+++ b/src/io/mod.rs
@@ -21,11 +21,14 @@
 //! # Ok(()) }) }
 //! ```
 
+pub(crate) const DEFAULT_CAPACITY: usize = 8 * 1024;
+
 #[doc(inline)]
 pub use std::io::{Error, ErrorKind, Result, SeekFrom};
 
 pub use buf_read::{BufRead, Lines};
 pub use buf_reader::BufReader;
+pub use buf_writer::BufWriter;
 pub use copy::copy;
 pub use empty::{empty, Empty};
 pub use read::Read;
@@ -39,6 +42,7 @@ pub use write::Write;
 
 mod buf_read;
 mod buf_reader;
+mod buf_writer;
 mod copy;
 mod empty;
 mod read;