vecdb 0.10.2

High-performance mutable persistent vectors built on rawdb
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

use std::marker::PhantomData;

use rawdb::{Reader, Region};

use crate::{AnyStoredVec, HEADER_OFFSET, ReadOnlyRawVec, VecIndex, VecValue};

use super::super::{RawStrategy, ReadWriteRawVec};

/// Read-only random-access handle into a raw vector's stored data.
///
/// Created via `raw_vec.reader()` (available on BytesVec/ZeroCopyVec via Deref).
/// Provides O(1) point reads directly from the memory-mapped file.
///
/// Only sees **stored** (persisted) values — does not check holes, updates,
/// or pushed values. For full dirty-state reads, use `get_any_or_read`.
pub struct VecReader<I, T, S> {
    _reader: Reader,
    data: *const u8,
    stored_len: usize,
    _marker: PhantomData<(I, T, S)>,
}

unsafe impl<I: Send, T: Send, S: Send> Send for VecReader<I, T, S> {}
unsafe impl<I: Sync, T: Sync, S: Sync> Sync for VecReader<I, T, S> {}

impl<I, T, S> VecReader<I, T, S>
where
    T: VecValue,
    S: RawStrategy<T>,
{
    const SIZE_OF_T: usize = size_of::<T>();

    pub(crate) fn from_region(region: &Region, stored_len: usize) -> Self {
        let reader = region.create_reader();
        let slice = reader.prefixed(HEADER_OFFSET);
        let ptr = slice.as_ptr();

        Self {
            _reader: reader,
            data: ptr,
            stored_len,
            _marker: PhantomData,
        }
    }

    pub fn from_read_write(vec: &ReadWriteRawVec<I, T, S>) -> Self
    where
        I: VecIndex,
    {
        Self::from_region(vec.region(), vec.stored_len())
    }

    pub fn from_read_only(vec: &ReadOnlyRawVec<I, T, S>) -> Self
    where
        I: VecIndex,
    {
        Self::from_region(vec.region(), vec.stored_len())
    }

    /// Returns the value at `index`.
    ///
    /// # Panics
    /// Panics if `index >= len()`.
    #[inline(always)]
    pub fn get(&self, index: usize) -> T {
        assert!(
            index < self.stored_len,
            "index {index} out of bounds (len {})",
            self.stored_len
        );
        // SAFETY: index < stored_len guarantees offset + SIZE_OF_T <= data_len
        unsafe { S::read_from_ptr(self.data, index * Self::SIZE_OF_T) }
    }

    /// Returns the value at `index`, or `None` if out of bounds.
    #[inline(always)]
    pub fn try_get(&self, index: usize) -> Option<T> {
        if index >= self.stored_len {
            return None;
        }
        // SAFETY: index < stored_len guarantees offset + SIZE_OF_T <= data_len
        Some(unsafe { S::read_from_ptr(self.data, index * Self::SIZE_OF_T) })
    }

    /// Returns the number of stored values.
    #[inline(always)]
    pub fn len(&self) -> usize {
        self.stored_len
    }

    /// Returns `true` if the reader is empty.
    #[inline(always)]
    pub fn is_empty(&self) -> bool {
        self.stored_len == 0
    }
}