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

// Copyright (c) The partial-io Contributors
// SPDX-License-Identifier: MIT

//! This module contains a reader wrapper that breaks its inputs up according to
//! a provided iterator.

use std::{
    cmp, fmt,
    io::{self, Read, Write},
};

use crate::{make_ops, PartialOp};

/// A reader wrapper that breaks inner `Read` instances up according to the
/// provided iterator.
///
/// # Examples
///
/// ```rust
/// use std::io::{Cursor, Read};
///
/// use partial_io::{PartialOp, PartialRead};
///
/// let reader = Cursor::new(vec![1, 2, 3, 4]);
/// let iter = ::std::iter::repeat(PartialOp::Limited(1));
/// let mut partial_reader = PartialRead::new(reader, iter);
/// let mut out = vec![0; 256];
///
/// let size = partial_reader.read(&mut out).unwrap();
/// assert_eq!(size, 1);
/// assert_eq!(&out[..1], &[1]);
/// ```
pub struct PartialRead<R> {
    inner: R,
    ops: Box<dyn Iterator<Item = PartialOp> + Send>,
}

impl<R> PartialRead<R>
where
    R: Read,
{
    /// Creates a new `PartialRead` wrapper over the reader with the specified `PartialOp`s.
    pub fn new<I>(inner: R, iter: I) -> Self
    where
        I: IntoIterator<Item = PartialOp> + 'static,
        I::IntoIter: Send,
    {
        PartialRead {
            inner,
            ops: make_ops(iter),
        }
    }

    /// Sets the `PartialOp`s for this reader.
    pub fn set_ops<I>(&mut self, iter: I) -> &mut Self
    where
        I: IntoIterator<Item = PartialOp> + 'static,
        I::IntoIter: Send,
    {
        self.ops = make_ops(iter);
        self
    }

    /// Acquires a reference to the underlying reader.
    pub fn get_ref(&self) -> &R {
        &self.inner
    }

    /// Acquires a mutable reference to the underlying reader.
    pub fn get_mut(&mut self) -> &mut R {
        &mut self.inner
    }

    /// Consumes this wrapper, returning the underlying reader.
    pub fn into_inner(self) -> R {
        self.inner
    }
}

impl<R> Read for PartialRead<R>
where
    R: Read,
{
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        match self.ops.next() {
            Some(PartialOp::Limited(n)) => {
                let len = cmp::min(n, buf.len());
                self.inner.read(&mut buf[..len])
            }
            Some(PartialOp::Err(err)) => Err(io::Error::new(
                err,
                "error during read, generated by partial-io",
            )),
            Some(PartialOp::Unlimited) | None => self.inner.read(buf),
        }
    }
}

// Forwarding impl to support duplex structs.
impl<R> Write for PartialRead<R>
where
    R: Read + Write,
{
    #[inline]
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        self.inner.write(buf)
    }

    #[inline]
    fn flush(&mut self) -> io::Result<()> {
        self.inner.flush()
    }
}

impl<R> fmt::Debug for PartialRead<R>
where
    R: fmt::Debug,
{
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("PartialRead")
            .field("inner", &self.inner)
            .finish()
    }
}

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

    use std::fs::File;

    use crate::tests::assert_send;

    #[test]
    fn test_sendable() {
        assert_send::<PartialRead<File>>();
    }
}