spill 0.5.2

Modern torrent client
Documentation 
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

//! File selection projected onto v1's indivisible, hash-verified pieces.
//! This is a scheduling plan, not storage authority or a durable checkpoint.
use crate::protocol::metainfo::{FileKind, Layout};
use std::io;

/// Priorities are ordered for scheduling; a boundary piece takes the maximum
/// priority of the data files it overlaps. Padding has no selectable content.
#[derive(
    Clone,
    Copy,
    Debug,
    Default,
    PartialEq,
    Eq,
    PartialOrd,
    Ord,
    serde::Serialize,
    serde::Deserialize,
)]
#[serde(rename_all = "snake_case")]
pub enum FilePriority {
    Skip,
    #[default]
    Normal,
    High,
}

/// Immutable, bounded by the metainfo's file and piece counts. Rebuild after a
/// selection change, then replace only at an owner scheduling boundary.
#[derive(Clone, Debug)]
pub struct FileSelection {
    files: Vec<FilePriority>,
    pieces: Vec<FilePriority>,
    wanted_bytes: u64,
}
impl FileSelection {
    /// Indices follow `Layout::files`, including padding entries (which must be
    /// Skip). Reject a mismatched manifest rather than silently selecting files.
    pub fn new(layout: &Layout<'_>, priorities: &[FilePriority]) -> io::Result<Self> {
        if priorities.len() != layout.files().len() {
            return Err(io::Error::new(
                io::ErrorKind::InvalidInput,
                "file priority count does not match the manifest",
            ));
        }
        let mut selection = Self {
            files: priorities.to_vec(),
            pieces: vec![FilePriority::Skip; layout.piece_count() as usize],
            wanted_bytes: 0,
        };
        let piece_length = u64::from(layout.piece_length());
        for (file, &priority) in layout.files().iter().zip(priorities) {
            if file.kind() == FileKind::Padding {
                if priority != FilePriority::Skip {
                    return Err(io::Error::new(
                        io::ErrorKind::InvalidInput,
                        "padding files cannot be selected",
                    ));
                }
                continue;
            }
            if priority == FilePriority::Skip {
                continue;
            }
            selection.wanted_bytes += file.length();
            if file.length() == 0 {
                continue;
            }
            let first = (file.offset() / piece_length) as usize;
            let end = (file.offset() + file.length()).div_ceil(piece_length) as usize;
            for piece in &mut selection.pieces[first..end] {
                *piece = (*piece).max(priority);
            }
        }
        Ok(selection)
    }

    pub fn all(layout: &Layout<'_>) -> Self {
        let priorities: Vec<_> = layout
            .files()
            .iter()
            .map(|file| match file.kind() {
                FileKind::Data => FilePriority::Normal,
                FileKind::Padding => FilePriority::Skip,
            })
            .collect();
        Self::new(layout, &priorities).expect("matching manifest and padding priorities")
    }

    pub fn file_priorities(&self) -> &[FilePriority] {
        &self.files
    }

    pub(in crate::engine) fn piece_priorities(&self) -> &[FilePriority] {
        &self.pieces
    }

    /// Selected data bytes only, excluding skipped boundary bytes and padding.
    pub fn wanted_bytes(&self) -> u64 {
        self.wanted_bytes
    }

    /// Selected data bytes covered by a particular piece, excluding boundary
    /// bytes belonging to skipped files and synthesized padding.
    pub(in crate::engine) fn piece_wanted_bytes(&self, layout: &Layout<'_>, index: u32) -> u64 {
        layout
            .piece_range(index)
            .and_then(|range| layout.segments(range))
            .into_iter()
            .flatten()
            .filter(|segment| {
                segment.kind == FileKind::Data
                    && self.files[segment.file_index] != FilePriority::Skip
            })
            .map(|segment| segment.length)
            .sum()
    }

    pub fn verified_bytes(&self, layout: &Layout<'_>, verified: &[u8]) -> u64 {
        self.pieces
            .iter()
            .enumerate()
            .filter(|(index, _)| verified_piece(verified, *index))
            .map(|(index, _)| self.piece_wanted_bytes(layout, index as u32))
            .sum()
    }

    /// All selected content is covered by verified pieces. Bits are MSB-first,
    /// just like peer bitfields and resume checkpoints; missing bytes are false.
    /// This never fabricates membership for a skipped piece.
    pub(in crate::engine) fn is_complete(&self, verified: &[u8]) -> bool {
        self.pieces.iter().enumerate().all(|(index, priority)| {
            *priority == FilePriority::Skip || verified_piece(verified, index)
        })
    }
}

fn verified_piece(verified: &[u8], index: usize) -> bool {
    verified
        .get(index / 8)
        .is_some_and(|byte| byte & (0x80 >> (index % 8)) != 0)
}