netvsp/
rx_bufs.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
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
// Copyright (c) Microsoft Corporation.
// Licensed under the MIT License.

//! Data structure for tracking receive buffer state.

use thiserror::Error;

/// State of networking receive buffers.
pub struct RxBuffers {
    /// Chains together rx receive buffers that are used as part of the same
    /// VMBus request. `state[i]` specifies the index of the next receive buffer
    /// in the request, or `END` if `i` is the last buffer. The beginning of
    /// each chain has `state[id] & START_MASK == START_MASK`. `INVALID`
    /// indicates the buffer is not in use.
    state: Vec<u32>,
}

const START_MASK: u32 = 0x80000000;
const INVALID: u32 = !START_MASK;
const END: u32 = !1 & !START_MASK;

#[derive(Debug, Error)]
#[error("suballocation is already in use")]
pub struct SubAllocationInUse;

impl RxBuffers {
    pub fn new(count: u32) -> Self {
        Self {
            state: (0..count).map(|_| INVALID).collect(),
        }
    }

    pub fn is_free(&self, id: u32) -> bool {
        self.state[id as usize] == INVALID
    }

    pub fn allocate<I: Iterator<Item = u32> + Clone>(
        &mut self,
        ids: impl IntoIterator<Item = u32, IntoIter = I>,
    ) -> Result<(), SubAllocationInUse> {
        let ids = ids.into_iter();
        let first = ids.clone().next().unwrap();
        let next_ids = ids.clone().skip(1).chain(std::iter::once(END));
        for (n, (id, next_id)) in ids.clone().zip(next_ids).enumerate() {
            if self.state[id as usize] != INVALID {
                for id in ids.take(n) {
                    self.state[id as usize] = INVALID;
                }
                return Err(SubAllocationInUse);
            }
            self.state[id as usize] = next_id;
        }
        self.state[first as usize] |= START_MASK;
        Ok(())
    }

    pub fn free(&mut self, id: u32) -> Option<FreeIterator<'_>> {
        let next = self.state.get(id as usize)?;
        if next & START_MASK == 0 {
            return None;
        }
        Some(FreeIterator {
            id,
            state: &mut self.state,
        })
    }

    pub fn allocated(&self) -> RxIterator<'_> {
        RxIterator {
            id: 0,
            chained_rx_id: &self.state,
        }
    }
}

pub struct RxIterator<'a> {
    id: usize,
    chained_rx_id: &'a Vec<u32>,
}

impl<'a> Iterator for RxIterator<'a> {
    type Item = ReadIterator<'a>;

    fn next(&mut self) -> Option<Self::Item> {
        while self.id < self.chained_rx_id.len() {
            let id = self.id;
            self.id += 1;
            if self.chained_rx_id[id] & START_MASK != 0 {
                return Some(ReadIterator {
                    id: id as u32,
                    state: self.chained_rx_id,
                });
            }
        }
        None
    }
}

pub struct ReadIterator<'a> {
    id: u32,
    state: &'a Vec<u32>,
}

impl Iterator for ReadIterator<'_> {
    type Item = u32;

    fn next(&mut self) -> Option<Self::Item> {
        let id = self.id;
        if id == END {
            return None;
        }
        self.id = self.state[id as usize] & !START_MASK;
        Some(id)
    }
}

pub struct FreeIterator<'a> {
    id: u32,
    state: &'a mut Vec<u32>,
}

impl Iterator for FreeIterator<'_> {
    type Item = u32;

    fn next(&mut self) -> Option<Self::Item> {
        let id = self.id;
        if id == END {
            return None;
        }
        self.id = self.state[id as usize] & !START_MASK;
        self.state[id as usize] = INVALID;
        Some(id)
    }
}

impl Drop for FreeIterator<'_> {
    fn drop(&mut self) {
        while self.next().is_some() {}
    }
}

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

    #[test]
    fn test_rx_bufs() {
        let mut bufs = RxBuffers::new(20);
        bufs.allocate([0, 1, 2]).unwrap();
        bufs.allocate([6, 9, 5]).unwrap();
        bufs.allocate([3, 10, 15, 0, 4]).unwrap_err();
        bufs.allocate([3, 10, 12]).unwrap();
        assert!(!bufs.is_free(1));
        assert!(!bufs.is_free(3));
        assert!(bufs.is_free(4));
        assert!(bufs.free(9).is_none());
        assert!(bufs.free(12).is_none());
        assert!(bufs.free(6).unwrap().eq([6, 9, 5]));
        assert!(
            bufs.allocated()
                .map(Vec::from_iter)
                .eq([[0, 1, 2], [3, 10, 12]])
        );
    }
}