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
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
use crate::codec::decoder::Decoder;
use crate::codec::encoder::Encoder;

use bytes::{Buf, BufMut, Bytes, BytesMut};
use std::{cmp, fmt, io, str};

const DEFAULT_SEEK_DELIMITERS: &[u8] = b",;\n\r";
const DEFAULT_SEQUENCE_WRITER: &[u8] = b",";
/// A simple [`Decoder`] and [`Encoder`] implementation that splits up data into chunks based on any character in the given delimiter string.
///
/// [`Decoder`]: crate::codec::Decoder
/// [`Encoder`]: crate::codec::Encoder
///
/// # Example
/// Decode string of bytes containing various different delimiters.
///
/// [`BytesMut`]: bytes::BytesMut
/// [`Error`]: std::io::Error
///
/// ```
/// use tokio_util::codec::{AnyDelimiterCodec, Decoder};
/// use bytes::{BufMut, BytesMut};
///
/// #
/// # #[tokio::main(flavor = "current_thread")]
/// # async fn main() -> Result<(), std::io::Error> {
/// let mut codec = AnyDelimiterCodec::new(b",;\r\n".to_vec(),b";".to_vec());
/// let buf = &mut BytesMut::new();
/// buf.reserve(200);
/// buf.put_slice(b"chunk 1,chunk 2;chunk 3\n\r");
/// assert_eq!("chunk 1", codec.decode(buf).unwrap().unwrap());
/// assert_eq!("chunk 2", codec.decode(buf).unwrap().unwrap());
/// assert_eq!("chunk 3", codec.decode(buf).unwrap().unwrap());
/// assert_eq!("", codec.decode(buf).unwrap().unwrap());
/// assert_eq!(None, codec.decode(buf).unwrap());
/// # Ok(())
/// # }
/// ```
///
#[derive(Clone, Debug, Eq, PartialEq, Ord, PartialOrd, Hash)]
pub struct AnyDelimiterCodec {
    // Stored index of the next index to examine for the delimiter character.
    // This is used to optimize searching.
    // For example, if `decode` was called with `abc` and the delimiter is '{}', it would hold `3`,
    // because that is the next index to examine.
    // The next time `decode` is called with `abcde}`, the method will
    // only look at `de}` before returning.
    next_index: usize,

    /// The maximum length for a given chunk. If `usize::MAX`, chunks will be
    /// read until a delimiter character is reached.
    max_length: usize,

    /// Are we currently discarding the remainder of a chunk which was over
    /// the length limit?
    is_discarding: bool,

    /// The bytes that are using for search during decode
    seek_delimiters: Vec<u8>,

    /// The bytes that are using for encoding
    sequence_writer: Vec<u8>,
}

impl AnyDelimiterCodec {
    /// Returns a `AnyDelimiterCodec` for splitting up data into chunks.
    ///
    /// # Note
    ///
    /// The returned `AnyDelimiterCodec` will not have an upper bound on the length
    /// of a buffered chunk. See the documentation for [`new_with_max_length`]
    /// for information on why this could be a potential security risk.
    ///
    /// [`new_with_max_length`]: crate::codec::AnyDelimiterCodec::new_with_max_length()
    pub fn new(seek_delimiters: Vec<u8>, sequence_writer: Vec<u8>) -> AnyDelimiterCodec {
        AnyDelimiterCodec {
            next_index: 0,
            max_length: usize::MAX,
            is_discarding: false,
            seek_delimiters,
            sequence_writer,
        }
    }

    /// Returns a `AnyDelimiterCodec` with a maximum chunk length limit.
    ///
    /// If this is set, calls to `AnyDelimiterCodec::decode` will return a
    /// [`AnyDelimiterCodecError`] when a chunk exceeds the length limit. Subsequent calls
    /// will discard up to `limit` bytes from that chunk until a delimiter
    /// character is reached, returning `None` until the delimiter over the limit
    /// has been fully discarded. After that point, calls to `decode` will
    /// function as normal.
    ///
    /// # Note
    ///
    /// Setting a length limit is highly recommended for any `AnyDelimiterCodec` which
    /// will be exposed to untrusted input. Otherwise, the size of the buffer
    /// that holds the chunk currently being read is unbounded. An attacker could
    /// exploit this unbounded buffer by sending an unbounded amount of input
    /// without any delimiter characters, causing unbounded memory consumption.
    ///
    /// [`AnyDelimiterCodecError`]: crate::codec::AnyDelimiterCodecError
    pub fn new_with_max_length(
        seek_delimiters: Vec<u8>,
        sequence_writer: Vec<u8>,
        max_length: usize,
    ) -> Self {
        AnyDelimiterCodec {
            max_length,
            ..AnyDelimiterCodec::new(seek_delimiters, sequence_writer)
        }
    }

    /// Returns the maximum chunk length when decoding.
    ///
    /// ```
    /// use std::usize;
    /// use tokio_util::codec::AnyDelimiterCodec;
    ///
    /// let codec = AnyDelimiterCodec::new(b",;\n".to_vec(), b";".to_vec());
    /// assert_eq!(codec.max_length(), usize::MAX);
    /// ```
    /// ```
    /// use tokio_util::codec::AnyDelimiterCodec;
    ///
    /// let codec = AnyDelimiterCodec::new_with_max_length(b",;\n".to_vec(), b";".to_vec(), 256);
    /// assert_eq!(codec.max_length(), 256);
    /// ```
    pub fn max_length(&self) -> usize {
        self.max_length
    }
}

impl Decoder for AnyDelimiterCodec {
    type Item = Bytes;
    type Error = AnyDelimiterCodecError;

    fn decode(&mut self, buf: &mut BytesMut) -> Result<Option<Bytes>, AnyDelimiterCodecError> {
        loop {
            // Determine how far into the buffer we'll search for a delimiter. If
            // there's no max_length set, we'll read to the end of the buffer.
            let read_to = cmp::min(self.max_length.saturating_add(1), buf.len());

            let new_chunk_offset = buf[self.next_index..read_to].iter().position(|b| {
                self.seek_delimiters
                    .iter()
                    .any(|delimiter| *b == *delimiter)
            });

            match (self.is_discarding, new_chunk_offset) {
                (true, Some(offset)) => {
                    // If we found a new chunk, discard up to that offset and
                    // then stop discarding. On the next iteration, we'll try
                    // to read a chunk normally.
                    buf.advance(offset + self.next_index + 1);
                    self.is_discarding = false;
                    self.next_index = 0;
                }
                (true, None) => {
                    // Otherwise, we didn't find a new chunk, so we'll discard
                    // everything we read. On the next iteration, we'll continue
                    // discarding up to max_len bytes unless we find a new chunk.
                    buf.advance(read_to);
                    self.next_index = 0;
                    if buf.is_empty() {
                        return Ok(None);
                    }
                }
                (false, Some(offset)) => {
                    // Found a chunk!
                    let new_chunk_index = offset + self.next_index;
                    self.next_index = 0;
                    let mut chunk = buf.split_to(new_chunk_index + 1);
                    chunk.truncate(chunk.len() - 1);
                    let chunk = chunk.freeze();
                    return Ok(Some(chunk));
                }
                (false, None) if buf.len() > self.max_length => {
                    // Reached the maximum length without finding a
                    // new chunk, return an error and start discarding on the
                    // next call.
                    self.is_discarding = true;
                    return Err(AnyDelimiterCodecError::MaxChunkLengthExceeded);
                }
                (false, None) => {
                    // We didn't find a chunk or reach the length limit, so the next
                    // call will resume searching at the current offset.
                    self.next_index = read_to;
                    return Ok(None);
                }
            }
        }
    }

    fn decode_eof(&mut self, buf: &mut BytesMut) -> Result<Option<Bytes>, AnyDelimiterCodecError> {
        Ok(match self.decode(buf)? {
            Some(frame) => Some(frame),
            None => {
                // return remaining data, if any
                if buf.is_empty() {
                    None
                } else {
                    let chunk = buf.split_to(buf.len());
                    self.next_index = 0;
                    Some(chunk.freeze())
                }
            }
        })
    }
}

impl<T> Encoder<T> for AnyDelimiterCodec
where
    T: AsRef<str>,
{
    type Error = AnyDelimiterCodecError;

    fn encode(&mut self, chunk: T, buf: &mut BytesMut) -> Result<(), AnyDelimiterCodecError> {
        let chunk = chunk.as_ref();
        buf.reserve(chunk.len() + 1);
        buf.put(chunk.as_bytes());
        buf.put(self.sequence_writer.as_ref());

        Ok(())
    }
}

impl Default for AnyDelimiterCodec {
    fn default() -> Self {
        Self::new(
            DEFAULT_SEEK_DELIMITERS.to_vec(),
            DEFAULT_SEQUENCE_WRITER.to_vec(),
        )
    }
}

/// An error occurred while encoding or decoding a chunk.
#[derive(Debug)]
pub enum AnyDelimiterCodecError {
    /// The maximum chunk length was exceeded.
    MaxChunkLengthExceeded,
    /// An IO error occurred.
    Io(io::Error),
}

impl fmt::Display for AnyDelimiterCodecError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            AnyDelimiterCodecError::MaxChunkLengthExceeded => {
                write!(f, "max chunk length exceeded")
            }
            AnyDelimiterCodecError::Io(e) => write!(f, "{}", e),
        }
    }
}

impl From<io::Error> for AnyDelimiterCodecError {
    fn from(e: io::Error) -> AnyDelimiterCodecError {
        AnyDelimiterCodecError::Io(e)
    }
}

impl std::error::Error for AnyDelimiterCodecError {}