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

// TrackedString telemetry tests — only compiled and run when `telemetry` is enabled.
// Verify that:
//   1. wrap_from records creation.
//   2. with_capacity_named records creation and capacity on Drop.
//   3. CapInspect works on TrackedString.

use std::sync::atomic::Ordering;

use crate::registry;
use crate::{CapInspect, IntoInner, TrackedString};

fn peak(name: &'static str) -> usize {
    let mut m = 0;
    registry::registry().scan(|_, stats| {
        if stats.name == name {
            let samples = stats.samples.snapshot();
            if let Some(&max_here) = samples.iter().max() {
                m = m.max(max_here);
            }
        }
    });
    m
}

fn count(name: &'static str) -> u64 {
    let mut s = 0;
    registry::registry().scan(|_, stats| {
        if stats.name == name {
            s += stats.creation_count.load(Ordering::Relaxed);
        }
    });
    s
}

#[test]
fn wrap_from_records_creation() {
    let before = count("test/string/wrap_creation");
    let inner = String::with_capacity(32);
    let _t = TrackedString::wrap_from(
        inner,
        "test/string/wrap_creation",
        file!(),
        line!(),
        column!(),
    );
    let after = count("test/string/wrap_creation");
    assert_eq!(after - before, 1, "wrap_from must increment creation_count");
}

#[test]
fn wrap_from_preserves_capacity() {
    let inner = String::with_capacity(64);
    let cap = inner.capacity();
    let t = TrackedString::wrap_from(inner, "test/string/wrap_cap", file!(), line!(), column!());
    assert_eq!(t.capacity(), cap, "wrap_from must not reallocate");
    drop(t);
    assert!(
        peak("test/string/wrap_cap") >= cap,
        "drop must record sample >= initial capacity"
    );
}

#[test]
fn drop_records_capacity_sample() {
    {
        let s = TrackedString::with_capacity_named(
            128,
            "test/string/drop_cap",
            file!(),
            line!(),
            column!(),
        );
        drop(s);
    }
    assert!(
        peak("test/string/drop_cap") >= 128,
        "peak must be at least the initial capacity"
    );
}

#[test]
fn into_inner_converts_to_bare_string() {
    let t = TrackedString::with_capacity_named(
        16,
        "test/string/into_inner",
        file!(),
        line!(),
        column!(),
    );
    let bare: String = t.into_inner();
    assert!(bare.capacity() >= 16);
    assert!(peak("test/string/into_inner") >= 16);
}

#[test]
fn deref_allows_string_methods() {
    let mut t =
        TrackedString::with_capacity_named(64, "test/string/deref", file!(), line!(), column!());
    t.push_str("hello world");
    assert_eq!(t.len(), 11);
    assert!(t.contains("world"));
}

#[test]
fn cap_inspect_works() {
    let t = TrackedString::with_capacity_named(
        256,
        "test/string/cap_inspect",
        file!(),
        line!(),
        column!(),
    );
    // cap_inspect_at reads capacity and records it; this must not panic.
    t.cap_inspect_at("test/string/cap_inspect_at", file!(), line!(), column!());
    // The record is an initial-cap record (via record_initial).  The peak here is 256.
    assert!(t.capacity() >= 256);
}

#[test]
fn as_ref_str_and_bytes_forward_to_inner() {
    let mut t =
        TrackedString::with_capacity_named(64, "test/string/as_ref", file!(), line!(), column!());
    t.push_str("hello");
    let as_str: &str = t.as_ref();
    assert_eq!(as_str, "hello");
    let as_bytes: &[u8] = t.as_ref();
    assert_eq!(as_bytes, b"hello");
}

#[test]
fn as_ref_bytes_satisfies_generic_bound() {
    // Regression test: a bare `&TrackedString` must satisfy `impl AsRef<[u8]>`
    // bounds (e.g. tokio::fs::write) at a borrow position, not just method
    // calls that go through Deref. Compile-time check via a generic helper.
    fn takes_bytes(_b: impl AsRef<[u8]>) {}
    let t = TrackedString::with_capacity_named(
        8,
        "test/string/as_ref_bound",
        file!(),
        line!(),
        column!(),
    );
    takes_bytes(&t);
}