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
use std::io;
use std::fmt;
use std::cmp;

use super::*;

/// Duplicates the underlying `BufferedReader` without consuming any
/// of the data.
///
/// Note: this will likely cause the underlying stream to buffer as
/// much data as you read.  Thus, it should only be used for peeking
/// at the underlying `BufferedReader`.
#[derive(Debug)]
pub struct Dup<T: BufferedReader<C>, C: fmt::Debug + Sync + Send> {
    // The number of bytes that have been consumed.
    cursor: usize,

    // The user settable cookie.
    cookie: C,

    reader: T,
}

assert_send_and_sync!(Dup<T, C>
                      where T: BufferedReader<C>,
                            C: fmt::Debug);

impl<T: BufferedReader<C>, C: fmt::Debug + Sync + Send> fmt::Display for Dup<T, C> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.debug_struct("Dup")
            .field("cursor", &self.cursor)
            .finish()
    }
}

impl<T: BufferedReader<()>> Dup<T, ()> {
    /// Instantiates a new `Dup` buffered reader.
    ///
    /// `reader` is the `BufferedReader` to duplicate.
    pub fn new(reader: T) -> Self {
        Self::with_cookie(reader, ())
    }
}

impl<T: BufferedReader<C>, C: fmt::Debug + Sync + Send> Dup<T, C> {
    /// Like [`Self::new`], but uses a cookie.
    ///
    /// The cookie can be retrieved using the [`BufferedReader::cookie_ref`] and
    /// [`BufferedReader::cookie_mut`] methods, and set using the [`BufferedReader::cookie_set`] method.
    pub fn with_cookie(reader: T, cookie: C) -> Self {
        Dup {
            reader,
            cursor: 0,
            cookie,
        }
    }

    /// Returns the number of bytes that this reader has consumed.
    pub fn total_out(&self) -> usize {
        self.cursor
    }

    /// Resets the cursor to the beginning of the stream.
    pub fn rewind(&mut self) {
        self.cursor = 0;
    }
}

impl<T: BufferedReader<C>, C: fmt::Debug + Sync + Send> io::Read for Dup<T, C> {
    fn read(&mut self, buf: &mut [u8]) -> Result<usize, io::Error> {
        let data = self.reader.data(self.cursor + buf.len())?;
        assert!(data.len() >= self.cursor);
        let data = &data[self.cursor..];

        let amount = cmp::min(buf.len(), data.len());
        buf[..amount].copy_from_slice(&data[..amount]);

        self.cursor += amount;

        Ok(amount)
    }
}

impl<T: BufferedReader<C>, C: fmt::Debug + Send + Sync> BufferedReader<C> for Dup<T, C> {
    fn buffer(&self) -> &[u8] {
        let data = self.reader.buffer();
        assert!(data.len() >= self.cursor);
        &data[self.cursor..]
    }

    fn data(&mut self, amount: usize) -> Result<&[u8], io::Error> {
        let data = self.reader.data(self.cursor + amount)?;
        assert!(data.len() >= self.cursor);
        Ok(&data[self.cursor..])
    }

    fn consume(&mut self, amount: usize) -> &[u8] {
        let data = self.reader.buffer();
        assert!(data.len() >= self.cursor + amount);
        let data = &data[self.cursor..];
        self.cursor += amount;
        data
    }

    fn data_consume(&mut self, amount: usize) -> Result<&[u8], io::Error> {
        let data = self.reader.data(self.cursor + amount)?;
        assert!(data.len() >= self.cursor);
        let data = &data[self.cursor..];
        self.cursor += cmp::min(data.len(), amount);
        Ok(data)
    }

    fn data_consume_hard(&mut self, amount: usize) -> Result<&[u8], io::Error> {
        let data = self.reader.data_hard(self.cursor + amount)?;
        assert!(data.len() >= self.cursor + amount);
        let data = &data[self.cursor..];
        self.cursor += amount;
        Ok(data)
    }

    fn get_mut(&mut self) -> Option<&mut dyn BufferedReader<C>> {
        Some(&mut self.reader)
    }

    fn get_ref(&self) -> Option<&dyn BufferedReader<C>> {
        Some(&self.reader)
    }

    fn into_inner<'b>(self: Box<Self>) -> Option<Box<dyn BufferedReader<C> + 'b>>
            where Self: 'b {
        Some(self.reader.into_boxed())
    }

    fn cookie_set(&mut self, cookie: C) -> C {
        use std::mem;

        mem::replace(&mut self.cookie, cookie)
    }

    fn cookie_ref(&self) -> &C {
        &self.cookie
    }

    fn cookie_mut(&mut self) -> &mut C {
        &mut self.cookie
    }
}

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn buffered_reader_memory_test () {
        let data = crate::BUFFERED_READER_TEST_DATA;
        let reader = Memory::new(data);
        let mut reader = Dup::new(reader);

        buffered_reader_test_data_check(&mut reader);

        let consumed = reader.total_out();
        assert_eq!(consumed, data.len());

        // Since we haven't consumed the inner buffer, this should
        // still work.
        let mut reader = Box::new(reader).into_inner().unwrap();

        // Try to read consumed + 1 bytes (which shouldn't be
        // possible).
        assert_eq!(consumed, reader.data(consumed + 1).unwrap().len());

        buffered_reader_test_data_check(&mut reader);
    }

    // Test that buffer() returns the same data as data().
    #[test]
    fn buffer_test() {
        // Test vector.  A Dup returns all unconsumed
        // data.  So, use a relatively small buffer size.
        let size = default_buf_size();
        let mut input = Vec::with_capacity(size);
        let mut v = 0u8;
        for _ in 0..size {
            input.push(v);
            if v == std::u8::MAX {
                v = 0;
            } else {
                v += 1;
            }
        }

        let reader = Memory::new(&input[..]);
        let mut reader = Dup::new(reader);

        for i in 0..input.len() {
            let data = reader.data(default_buf_size() + 1).unwrap().to_vec();
            assert!(!data.is_empty());
            assert_eq!(data, reader.buffer());
            // And, we may as well check to make sure we read the
            // right data.
            assert_eq!(data, &input[i..i+data.len()]);

            // Consume one byte and see what happens.
            reader.consume(1);
        }
    }
}