subspace_farmer/single_disk_farm/farming/
rayon_files.rs

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
//! Files abstraction that allows reading concurrently using thread pool

use std::fs::{File, OpenOptions};
use std::io;
use std::path::Path;
use subspace_farmer_components::file_ext::{FileExt, OpenOptionsExt};
use subspace_farmer_components::ReadAtSync;

/// Wrapper data structure for multiple files to be used with [`rayon`] thread pool, where the same
/// file is opened multiple times, once for each thread for faster concurrent reads
#[derive(Debug)]
pub struct RayonFiles<File> {
    files: Vec<File>,
}

impl<File> ReadAtSync for RayonFiles<File>
where
    File: ReadAtSync,
{
    fn read_at(&self, buf: &mut [u8], offset: u64) -> io::Result<()> {
        let thread_index = rayon::current_thread_index().unwrap_or_default();
        let file = self.files.get(thread_index).ok_or_else(|| {
            io::Error::new(io::ErrorKind::Other, "No files entry for this rayon thread")
        })?;

        file.read_at(buf, offset)
    }
}

impl<File> ReadAtSync for &RayonFiles<File>
where
    File: ReadAtSync,
{
    #[inline]
    fn read_at(&self, buf: &mut [u8], offset: u64) -> io::Result<()> {
        (*self).read_at(buf, offset)
    }
}

impl RayonFiles<File> {
    /// Open file at specified path as many times as there is number of threads in current [`rayon`]
    /// thread pool.
    pub fn open<P>(path: P) -> io::Result<Self>
    where
        P: AsRef<Path>,
    {
        let files = (0..rayon::current_num_threads())
            .map(|_| {
                let file = OpenOptions::new()
                    .read(true)
                    .advise_random_access()
                    .open(path.as_ref())?;
                file.advise_random_access()?;

                Ok::<_, io::Error>(file)
            })
            .collect::<Result<Vec<_>, _>>()?;

        Ok(Self { files })
    }
}

impl<File> RayonFiles<File>
where
    File: ReadAtSync,
{
    /// Open file at specified path as many times as there is number of threads in current [`rayon`]
    /// thread pool with a provided function
    pub fn open_with<P>(path: P, open: fn(&Path) -> io::Result<File>) -> io::Result<Self>
    where
        P: AsRef<Path>,
    {
        let files = (0..rayon::current_num_threads())
            .map(|_| open(path.as_ref()))
            .collect::<Result<Vec<_>, _>>()?;

        Ok(Self { files })
    }
}