djin_protocol/wire/
reader.rs

1use crate::{Error, ErrorKind, Parcel, Settings};
2use std::io;
3use std::io::prelude::*;
4
5/// A receive buffer that waits until enough data is ready
6/// and then returns the parsed parcels.
7///
8/// This mechanism can be used to send parcels without
9/// length prefixes.
10///
11///
12/// # Adding data to the receive buffer
13///
14/// `Reader` implements `std::io::Write`. Any bytes written
15/// to the reader are added to the receive queue for future
16/// processing.
17///
18/// # Example
19///
20/// This example shows a reader only returning a `u32`
21/// once enough data has been buffered.
22///
23/// ```
24/// use djin_protocol;
25/// use std::io::Write;
26///
27/// let mut reader = djin_protocol::wire::Reader::new();
28/// let settings = djin_protocol::Settings::default();
29///
30/// // No bytes received yet.
31/// assert_eq!(None, reader.poll::<u32>(&settings).unwrap());
32///
33/// // Two bytes received.
34/// reader.write(&[0xff, 0x00]).unwrap();
35/// assert_eq!(None, reader.poll::<u32>(&settings).unwrap());
36///
37/// // Three bytes received.
38/// reader.write(&[0x00]).unwrap();
39/// assert_eq!(None, reader.poll::<u32>(&settings).unwrap());
40///
41/// // All four bytes received.
42/// reader.write(&[0x00]).unwrap();
43/// assert_eq!(Some(0xff000000), reader.poll::<u32>(&settings).unwrap());
44/// ```
45#[derive(Debug)]
46pub struct Reader {
47    /// The internal receive buffer.
48    ///
49    /// Contains all bytes that have been received but not yet parsed
50    /// into a packet.
51    receive_buffer: Vec<u8>,
52}
53
54impl Reader {
55    /// Creates a new parcel reader.
56    pub fn new() -> Self {
57        Reader {
58            receive_buffer: Vec::new(),
59        }
60    }
61
62    /// Polls the reader for a value.
63    ///
64    /// Returns `Ok(None)` if further data must be received in order
65    /// to interpret the value.
66    ///
67    /// Returns `Ok(Some(value))` if the value is ready to be read
68    /// from the stream.
69    ///
70    /// Returns `Err(e)` on error.
71    pub fn poll<P>(&mut self,
72                   settings: &Settings)
73        -> Result<Option<P>, Error>
74        where P: Parcel {
75        let mut cursor = io::Cursor::new(self.receive_buffer.clone());
76
77        match Parcel::read(&mut cursor, settings) {
78            Ok(value) => {
79                // Remove the interpreted bytes from the receive buffer.
80                let bytes_read = cursor.position() as usize;
81                self.receive_buffer.drain(0..bytes_read);
82
83                Ok(Some(value))
84            },
85            Err(e) => match e.0 {
86                ErrorKind::Io(io) => {
87                    // Ignore errors caused by the receive buffer
88                    // not having enough data yet.
89                    if io.kind() == io::ErrorKind::UnexpectedEof {
90                        Ok(None)
91                    } else {
92                        // An actual IO error.
93                        Err(ErrorKind::Io(io).into())
94                    }
95                },
96                _ => Err(e),
97            },
98        }
99    }
100}
101
102impl Write for Reader {
103    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
104        self.receive_buffer.extend(buf);
105        Ok(buf.len())
106    }
107
108    fn flush(&mut self) -> io::Result<()> { Ok(()) }
109}
110
111impl Default for Reader {
112    fn default() -> Self {
113        Reader::new()
114    }
115}
116
djin_protocol/wire/reader.rs

djin_protocol/wire/
reader.rs
