core_io 0.1.20210325

This is a copy of libstd::io with all the parts that don't work in core removed. Most importantly, it provides the Read and Write traits. This crate is (mostly) automatically generated from the rust git source. The version of the source that corresponds to your compiler version will be selected automatically by the build script. 
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

use crate::cmp::{max, min};
use crate::io::prelude::*;
use crate::io::{
    copy, empty, repeat, sink, BufWriter, Empty, Repeat, Result, SeekFrom, Sink, DEFAULT_BUF_SIZE,
};

#[test]
fn copy_copies() {
    let mut r = repeat(0).take(4);
    let mut w = sink();
    assert_eq!(copy(&mut r, &mut w).unwrap(), 4);

    let mut r = repeat(0).take(1 << 17);
    assert_eq!(copy(&mut r as &mut dyn Read, &mut w as &mut dyn Write).unwrap(), 1 << 17);
}

struct ShortReader {
    cap: usize,
    read_size: usize,
    observed_buffer: usize,
}

impl Read for ShortReader {
    fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
        let bytes = min(self.cap, self.read_size);
        self.cap -= bytes;
        self.observed_buffer = max(self.observed_buffer, buf.len());
        Ok(bytes)
    }
}

struct WriteObserver {
    observed_buffer: usize,
}

impl Write for WriteObserver {
    fn write(&mut self, buf: &[u8]) -> Result<usize> {
        self.observed_buffer = max(self.observed_buffer, buf.len());
        Ok(buf.len())
    }

    fn flush(&mut self) -> Result<()> {
        Ok(())
    }
}

#[test]
fn copy_specializes_bufwriter() {
    let cap = 117 * 1024;
    let buf_sz = 16 * 1024;
    let mut r = ShortReader { cap, observed_buffer: 0, read_size: 1337 };
    let mut w = BufWriter::with_capacity(buf_sz, WriteObserver { observed_buffer: 0 });
    assert_eq!(
        copy(&mut r, &mut w).unwrap(),
        cap as u64,
        "expected the whole capacity to be copied"
    );
    assert_eq!(r.observed_buffer, buf_sz, "expected a large buffer to be provided to the reader");
    assert!(w.get_mut().observed_buffer > DEFAULT_BUF_SIZE, "expected coalesced writes");
}

#[test]
fn sink_sinks() {
    let mut s = sink();
    assert_eq!(s.write(&[]).unwrap(), 0);
    assert_eq!(s.write(&[0]).unwrap(), 1);
    assert_eq!(s.write(&[0; 1024]).unwrap(), 1024);
    assert_eq!(s.by_ref().write(&[0; 1024]).unwrap(), 1024);
}

#[test]
fn empty_reads() {
    let mut e = empty();
    assert_eq!(e.read(&mut []).unwrap(), 0);
    assert_eq!(e.read(&mut [0]).unwrap(), 0);
    assert_eq!(e.read(&mut [0; 1024]).unwrap(), 0);
    assert_eq!(e.by_ref().read(&mut [0; 1024]).unwrap(), 0);
}

#[test]
fn empty_seeks() {
    let mut e = empty();
    assert!(matches!(e.seek(SeekFrom::Start(0)), Ok(0)));
    assert!(matches!(e.seek(SeekFrom::Start(1)), Ok(0)));
    assert!(matches!(e.seek(SeekFrom::Start(u64::MAX)), Ok(0)));

    assert!(matches!(e.seek(SeekFrom::End(i64::MIN)), Ok(0)));
    assert!(matches!(e.seek(SeekFrom::End(-1)), Ok(0)));
    assert!(matches!(e.seek(SeekFrom::End(0)), Ok(0)));
    assert!(matches!(e.seek(SeekFrom::End(1)), Ok(0)));
    assert!(matches!(e.seek(SeekFrom::End(i64::MAX)), Ok(0)));

    assert!(matches!(e.seek(SeekFrom::Current(i64::MIN)), Ok(0)));
    assert!(matches!(e.seek(SeekFrom::Current(-1)), Ok(0)));
    assert!(matches!(e.seek(SeekFrom::Current(0)), Ok(0)));
    assert!(matches!(e.seek(SeekFrom::Current(1)), Ok(0)));
    assert!(matches!(e.seek(SeekFrom::Current(i64::MAX)), Ok(0)));
}

#[test]
fn repeat_repeats() {
    let mut r = repeat(4);
    let mut b = [0; 1024];
    assert_eq!(r.read(&mut b).unwrap(), 1024);
    assert!(b.iter().all(|b| *b == 4));
}

#[test]
fn take_some_bytes() {
    assert_eq!(repeat(4).take(100).bytes().count(), 100);
    assert_eq!(repeat(4).take(100).bytes().next().unwrap().unwrap(), 4);
    assert_eq!(repeat(1).take(10).chain(repeat(2).take(10)).bytes().count(), 20);
}

#[allow(dead_code)]
fn const_utils() {
    const _: Empty = empty();
    const _: Repeat = repeat(b'c');
    const _: Sink = sink();
}