velesdb_core/storage/
guard.rs

1//! Zero-copy guard for vector data from mmap storage.
2
3use memmap2::MmapMut;
4use parking_lot::RwLockReadGuard;
5
6/// Zero-copy guard for vector data from mmap storage.
7///
8/// This guard holds a read lock on the mmap and provides direct access
9/// to the vector data without any memory allocation or copy.
10///
11/// # Performance
12///
13/// Using `VectorSliceGuard` instead of `retrieve()` eliminates:
14/// - Heap allocation for the result `Vec<f32>`
15/// - Memory copy from mmap to the new vector
16///
17/// # Example
18///
19/// ```rust,ignore
20/// let guard = storage.retrieve_ref(id)?.unwrap();
21/// let slice: &[f32] = guard.as_ref();
22/// // Use slice directly - no allocation occurred
23/// ```
24pub struct VectorSliceGuard<'a> {
25    /// Read guard holding the mmap lock
26    pub(super) _guard: RwLockReadGuard<'a, MmapMut>,
27    /// Pointer to the start of vector data
28    pub(super) ptr: *const f32,
29    /// Number of f32 elements
30    pub(super) len: usize,
31}
32
33// SAFETY: VectorSliceGuard is Send+Sync because:
34// 1. The underlying data is in a memory-mapped file (shared memory)
35// 2. We hold a RwLockReadGuard which ensures exclusive read access
36// 3. The pointer is derived from the guard and valid for its lifetime
37unsafe impl Send for VectorSliceGuard<'_> {}
38unsafe impl Sync for VectorSliceGuard<'_> {}
39
40impl VectorSliceGuard<'_> {
41    /// Returns the vector data as a slice.
42    #[inline]
43    #[must_use]
44    pub fn as_slice(&self) -> &[f32] {
45        // SAFETY: ptr and len were validated during construction,
46        // and the guard ensures the mmap remains valid
47        unsafe { std::slice::from_raw_parts(self.ptr, self.len) }
48    }
49}
50
51impl AsRef<[f32]> for VectorSliceGuard<'_> {
52    #[inline]
53    fn as_ref(&self) -> &[f32] {
54        self.as_slice()
55    }
56}
57
58impl std::ops::Deref for VectorSliceGuard<'_> {
59    type Target = [f32];
60
61    #[inline]
62    fn deref(&self) -> &Self::Target {
63        self.as_slice()
64    }
65}
velesdb_core/storage/guard.rs

velesdb_core/storage/
guard.rs
