aboutsummaryrefslogtreecommitdiff
path: root/src/stream.rs
blob: 88c3fed484ffdec212bd547781d6730bfce09df0 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
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)
}