1 files changed, 202 insertions, 0 deletions
diff --git a/src/stream.rs b/src/stream.rs
new file mode 100644
index 0000000..88c3fed
--- /dev/null
+++ b/src/stream.rs
@@ -0,0 +1,202 @@
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+use bytes::Bytes;
+
+use futures::Future;
+use futures::{Stream, StreamExt};
+use tokio::io::AsyncRead;
+
+use crate::bytes_buf::BytesBuf;
+
+/// A stream of bytes (click to read more).
+///
+/// When sent through Netapp, the Vec may be split in smaller chunk in such a way
+/// consecutive Vec may get merged, but Vec and error code may not be reordered
+///
+/// Items sent in the ByteStream may be errors of type `std::io::Error`.
+/// An error indicates the end of the ByteStream: a reader should no longer read
+/// after recieving an error, and a writer should stop writing after sending an error.
+pub type ByteStream = Pin<Box<dyn Stream<Item = Packet> + Send + Sync>>;
+
+/// A packet sent in a ByteStream, which may contain either
+/// a Bytes object or an error
+pub type Packet = Result<Bytes, std::io::Error>;
+
+// ----
+
+/// A helper struct to read defined lengths of data from a BytesStream
+pub struct ByteStreamReader {
+	stream: ByteStream,
+	buf: BytesBuf,
+	eos: bool,
+	err: Option<std::io::Error>,
+}
+
+impl ByteStreamReader {
+	/// Creates a new `ByteStreamReader` from a `ByteStream`
+	pub fn new(stream: ByteStream) -> Self {
+		ByteStreamReader {
+			stream,
+			buf: BytesBuf::new(),
+			eos: false,
+			err: None,
+		}
+	}
+
+	/// Read exactly `read_len` bytes from the underlying stream
+	/// (returns a future)
+	pub fn read_exact(&mut self, read_len: usize) -> ByteStreamReadExact<'_> {
+		ByteStreamReadExact {
+			reader: self,
+			read_len,
+			fail_on_eos: true,
+		}
+	}
+
+	/// Read at most `read_len` bytes from the underlying stream, or less
+	/// if the end of the stream is reached (returns a future)
+	pub fn read_exact_or_eos(&mut self, read_len: usize) -> ByteStreamReadExact<'_> {
+		ByteStreamReadExact {
+			reader: self,
+			read_len,
+			fail_on_eos: false,
+		}
+	}
+
+	/// Read exactly one byte from the underlying stream and returns it
+	/// as an u8
+	pub async fn read_u8(&mut self) -> Result<u8, ReadExactError> {
+		Ok(self.read_exact(1).await?[0])
+	}
+
+	/// Read exactly two bytes from the underlying stream and returns them as an u16 (using
+	/// big-endian decoding)
+	pub async fn read_u16(&mut self) -> Result<u16, ReadExactError> {
+		let bytes = self.read_exact(2).await?;
+		let mut b = [0u8; 2];
+		b.copy_from_slice(&bytes[..]);
+		Ok(u16::from_be_bytes(b))
+	}
+
+	/// Read exactly four bytes from the underlying stream and returns them as an u32 (using
+	/// big-endian decoding)
+	pub async fn read_u32(&mut self) -> Result<u32, ReadExactError> {
+		let bytes = self.read_exact(4).await?;
+		let mut b = [0u8; 4];
+		b.copy_from_slice(&bytes[..]);
+		Ok(u32::from_be_bytes(b))
+	}
+
+	/// Transforms the stream reader back into the underlying stream (starting
+	/// after everything that the reader has read)
+	pub fn into_stream(self) -> ByteStream {
+		let buf_stream = futures::stream::iter(self.buf.into_slices().into_iter().map(Ok));
+		if let Some(err) = self.err {
+			Box::pin(buf_stream.chain(futures::stream::once(async move { Err(err) })))
+		} else if self.eos {
+			Box::pin(buf_stream)
+		} else {
+			Box::pin(buf_stream.chain(self.stream))
+		}
+	}
+
+	/// Tries to fill the internal read buffer from the underlying stream if it is empty.
+	/// Calling this might be necessary to ensure that `.eos()` returns a correct
+	/// result, otherwise the reader might not be aware that the underlying
+	/// stream has nothing left to return.
+	pub async fn fill_buffer(&mut self) {
+		if self.buf.is_empty() {
+			let packet = self.stream.next().await;
+			self.add_stream_next(packet);
+		}
+	}
+
+	/// Clears the internal read buffer and returns its content
+	pub fn take_buffer(&mut self) -> Bytes {
+		self.buf.take_all()
+	}
+
+	/// Returns true if the end of the underlying stream has been reached
+	pub fn eos(&self) -> bool {
+		self.buf.is_empty() && self.eos
+	}
+
+	fn try_get(&mut self, read_len: usize) -> Option<Bytes> {
+		self.buf.take_exact(read_len)
+	}
+
+	fn add_stream_next(&mut self, packet: Option<Packet>) {
+		match packet {
+			Some(Ok(slice)) => {
+				self.buf.extend(slice);
+			}
+			Some(Err(e)) => {
+				self.err = Some(e);
+				self.eos = true;
+			}
+			None => {
+				self.eos = true;
+			}
+		}
+	}
+}
+
+/// The error kind that can be returned by `ByteStreamReader::read_exact` and
+/// `ByteStreamReader::read_exact_or_eos`
+pub enum ReadExactError {
+	/// The end of the stream was reached before the requested number of bytes could be read
+	UnexpectedEos,
+	/// The underlying data stream returned an IO error when trying to read
+	Stream(std::io::Error),
+}
+
+/// The future returned by `ByteStreamReader::read_exact` and
+/// `ByteStreamReader::read_exact_or_eos`
+#[pin_project::pin_project]
+pub struct ByteStreamReadExact<'a> {
+	#[pin]
+	reader: &'a mut ByteStreamReader,
+	read_len: usize,
+	fail_on_eos: bool,
+}
+
+impl<'a> Future for ByteStreamReadExact<'a> {
+	type Output = Result<Bytes, ReadExactError>;
+
+	fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<Bytes, ReadExactError>> {
+		let mut this = self.project();
+
+		loop {
+			if let Some(bytes) = this.reader.try_get(*this.read_len) {
+				return Poll::Ready(Ok(bytes));
+			}
+			if let Some(err) = &this.reader.err {
+				let err = std::io::Error::new(err.kind(), format!("{}", err));
+				return Poll::Ready(Err(ReadExactError::Stream(err)));
+			}
+			if this.reader.eos {
+				if *this.fail_on_eos {
+					return Poll::Ready(Err(ReadExactError::UnexpectedEos));
+				} else {
+					return Poll::Ready(Ok(this.reader.take_buffer()));
+				}
+			}
+
+			let next_packet = futures::ready!(this.reader.stream.as_mut().poll_next(cx));
+			this.reader.add_stream_next(next_packet);
+		}
+	}
+}
+
+// ----
+
+/// Turns a `tokio::io::AsyncRead` asynchronous reader into a `ByteStream`
+pub fn asyncread_stream<R: AsyncRead + Send + Sync + 'static>(reader: R) -> ByteStream {
+	Box::pin(tokio_util::io::ReaderStream::new(reader))
+}
+
+/// Turns a `ByteStream` into a `tokio::io::AsyncRead` asynchronous reader
+pub fn stream_asyncread(stream: ByteStream) -> impl AsyncRead + Send + Sync + 'static {
+	tokio_util::io::StreamReader::new(stream)
+}