captrack 0.1.0

Capacity telemetry for Rust collections — call-site macros that record peak capacity, with zero overhead when disabled.
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

use smallvec::SmallVec;

use crate::registry;
use crate::IntoInner;

/// A `SmallVec<A>` wrapper that records creation count and capacity samples in
/// the global capacity-telemetry registry.
///
/// Compiled only when the `telemetry` feature is enabled; in off-feature mode
/// the `tsmallvec!` macro expands directly to `::smallvec::SmallVec::with_capacity(cap)`
/// with zero overhead.
pub struct TrackedSmallVec<A: smallvec::Array> {
    inner: SmallVec<A>,
    #[allow(dead_code)]
    name: &'static str,
    file: &'static str,
    line: u32,
    column: u32,
}

impl<A: smallvec::Array> TrackedSmallVec<A> {
    /// Create a new `TrackedSmallVec` with the given capacity and register the
    /// creation in the global registry.
    pub fn with_capacity_named(
        cap: usize,
        name: &'static str,
        file: &'static str,
        line: u32,
        column: u32,
    ) -> Self {
        registry::record_creation(name, file, line, column);
        Self {
            inner: SmallVec::with_capacity(cap),
            name,
            file,
            line,
            column,
        }
    }

    /// Wrap an already-constructed `SmallVec<A>` for capacity telemetry.
    ///
    /// Records creation in the registry; `inner` is moved as-is — no
    /// reallocation.  Capacity sample recorded at `Drop` as usual.
    ///
    /// This is the key entry-point for Phase K instrumentation: `smallvec![a, b, c]`
    /// can now be wrapped universally without losing elements:
    /// `TrackedSmallVec::wrap_from(smallvec![a, b, c], "auto:...", file!(), line!(), column!())`.
    #[inline]
    pub fn wrap_from(
        inner: SmallVec<A>,
        name: &'static str,
        file: &'static str,
        line: u32,
        column: u32,
    ) -> Self {
        registry::record_creation(name, file, line, column);
        Self {
            inner,
            name,
            file,
            line,
            column,
        }
    }
}

impl<A: smallvec::Array> std::ops::Deref for TrackedSmallVec<A> {
    type Target = SmallVec<A>;
    fn deref(&self) -> &SmallVec<A> {
        &self.inner
    }
}

impl<A: smallvec::Array> std::ops::DerefMut for TrackedSmallVec<A> {
    fn deref_mut(&mut self) -> &mut SmallVec<A> {
        &mut self.inner
    }
}

impl<A: smallvec::Array> Drop for TrackedSmallVec<A> {
    fn drop(&mut self) {
        registry::record_sample(self.file, self.line, self.column, self.inner.capacity());
    }
}

// Cross-feature boundary bridge: converting `TrackedSmallVec<A>` to bare
// `SmallVec<A>` at API boundaries.  Records the final capacity sample (same as
// Drop would) and then unwraps `inner`.
impl<A: smallvec::Array> From<TrackedSmallVec<A>> for SmallVec<A> {
    fn from(tracked: TrackedSmallVec<A>) -> SmallVec<A> {
        registry::record_sample(
            tracked.file,
            tracked.line,
            tracked.column,
            tracked.inner.capacity(),
        );
        // SAFETY: `tracked` is owned by us and will be forgotten on the next
        // line, so its Drop never runs.  `ptr::read` bit-copies `inner` out;
        // ownership moves to the returned value.
        let inner = unsafe { std::ptr::read(&tracked.inner) };
        std::mem::forget(tracked);
        inner
    }
}

impl<A: smallvec::Array> IntoInner for TrackedSmallVec<A> {
    type Inner = SmallVec<A>;
    #[inline]
    fn into_inner(self) -> SmallVec<A> {
        SmallVec::from(self)
    }
}

impl<A: smallvec::Array> IntoIterator for TrackedSmallVec<A> {
    type Item = A::Item;
    type IntoIter = smallvec::IntoIter<A>;

    fn into_iter(self) -> Self::IntoIter {
        // Record sample before consuming `inner`.  We must do this explicitly
        // here because `into_iter` moves out of `self.inner` — if we let `Drop`
        // run afterwards it would see `capacity() == 0` and record a false
        // zero.  `std::mem::forget(self)` prevents the Drop from running a
        // second time.
        //
        // SAFETY: `self` is owned by us and will be forgotten on the next
        // line, so its Drop never runs.  `ptr::read` bit-copies `inner` out.
        registry::record_sample(self.file, self.line, self.column, self.inner.capacity());
        let inner = unsafe { std::ptr::read(&self.inner) };
        std::mem::forget(self);
        inner.into_iter()
    }
}

impl<'a, A: smallvec::Array> IntoIterator for &'a TrackedSmallVec<A> {
    type Item = &'a A::Item;
    type IntoIter = std::slice::Iter<'a, A::Item>;
    fn into_iter(self) -> Self::IntoIter {
        self.inner.iter()
    }
}

impl<'a, A: smallvec::Array> IntoIterator for &'a mut TrackedSmallVec<A> {
    type Item = &'a mut A::Item;
    type IntoIter = std::slice::IterMut<'a, A::Item>;
    fn into_iter(self) -> Self::IntoIter {
        self.inner.iter_mut()
    }
}