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
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
use std::hash::Hasher;

use ahash::AHasher;

use crate::cow::Cow;

/// An allocation-optimized string.
///
/// We specify `SharedString` to attempt to get the best of both worlds: flexibility to provide a
/// static or dynamic (owned) string, while retaining the performance benefits of being able to
/// take ownership of owned strings and borrows of completely static strings.
///
/// `SharedString` can be converted to from either `&'static str` or `String`, with a method,
/// `const_str`, from constructing `SharedString` from `&'static str` in a `const` fashion.
pub type SharedString = Cow<'static, str>;

/// Key-specific hashing algorithm.
///
/// Currently uses AHash - <https://github.com/tkaitchuck/aHash>
///
/// For any use-case within a `metrics`-owned or adjacent crate, where hashing of a key is required,
/// this is the hasher that will be used.
#[derive(Default)]
pub struct KeyHasher(AHasher);

impl Hasher for KeyHasher {
    fn finish(&self) -> u64 {
        self.0.finish()
    }

    fn write(&mut self, bytes: &[u8]) {
        self.0.write(bytes)
    }
}

/// Value of a gauge operation.
#[derive(Clone, Debug)]
pub enum GaugeValue {
    /// Sets the value of the gauge to this value.
    Absolute(f64),
    /// Increments the value of the gauge by this much.
    Increment(f64),
    /// Decrements the value of the gauge by this much.
    Decrement(f64),
}

impl GaugeValue {
    /// Updates an input value based on this gauge value.
    pub fn update_value(&self, input: f64) -> f64 {
        match self {
            GaugeValue::Absolute(val) => *val,
            GaugeValue::Increment(val) => input + val,
            GaugeValue::Decrement(val) => input - val,
        }
    }
}

/// Units for a given metric.
///
/// While metrics do not necessarily need to be tied to a particular unit to be recorded, some
/// downstream systems natively support defining units and so they can be specified during registration.
#[derive(Clone, Copy, Debug, PartialEq)]
pub enum Unit {
    /// Count.
    Count,
    /// Percentage.
    Percent,
    /// Seconds.
    ///
    /// One second is equal to 1000 milliseconds.
    Seconds,
    /// Milliseconds.
    ///
    /// One millisecond is equal to 1000 microseconds.
    Milliseconds,
    /// Microseconds.
    ///
    /// One microsecond is equal to 1000 nanoseconds.
    Microseconds,
    /// Nanoseconds.
    Nanoseconds,
    /// Tebibytes.
    ///
    /// One tebibyte is equal to 1024 gigibytes.
    Tebibytes,
    /// Gigibytes.
    ///
    /// One gigibyte is equal to 1024 mebibytes.
    Gigibytes,
    /// Mebibytes.
    ///
    /// One mebibyte is equal to 1024 kibibytes.
    Mebibytes,
    /// Kibibytes.
    ///
    /// One kibibyte is equal to 1024 bytes.
    Kibibytes,
    /// Bytes.
    Bytes,
    /// Terabits per second.
    ///
    /// One terabit is equal to 1000 gigabits.
    TerabitsPerSecond,
    /// Gigabits per second.
    ///
    /// One gigabit is equal to 1000 megabits.
    GigabitsPerSecond,
    /// Megabits per second.
    ///
    /// One megabit is equal to 1000 kilobits.
    MegabitsPerSecond,
    /// Kilobits per second.
    ///
    /// One kilobit is equal to 1000 bits.
    KilobitsPerSecond,
    /// Bits per second.
    BitsPerSecond,
    /// Count per second.
    CountPerSecond,
}

impl Unit {
    /// Gets the string form of this `Unit`.
    pub fn as_str(&self) -> &str {
        match self {
            Unit::Count => "count",
            Unit::Percent => "percent",
            Unit::Seconds => "seconds",
            Unit::Milliseconds => "milliseconds",
            Unit::Microseconds => "microseconds",
            Unit::Nanoseconds => "nanoseconds",
            Unit::Tebibytes => "tebibytes",
            Unit::Gigibytes => "gigibytes",
            Unit::Mebibytes => "mebibytes",
            Unit::Kibibytes => "kibibytes",
            Unit::Bytes => "bytes",
            Unit::TerabitsPerSecond => "terabits_per_second",
            Unit::GigabitsPerSecond => "gigabits_per_second",
            Unit::MegabitsPerSecond => "megabits_per_second",
            Unit::KilobitsPerSecond => "kilobits_per_second",
            Unit::BitsPerSecond => "bits_per_second",
            Unit::CountPerSecond => "count_per_second",
        }
    }

    /// Gets the canonical string label for the given unit.
    ///
    /// For example, the canonical label for `Seconds` would be `s`, while for `Nanoseconds`,
    /// it would be `ns`.
    ///
    /// Not all units have a meaningful display label and so some may be empty.
    pub fn as_canonical_label(&self) -> &str {
        match self {
            Unit::Count => "",
            Unit::Percent => "%",
            Unit::Seconds => "s",
            Unit::Milliseconds => "ms",
            Unit::Microseconds => "μs",
            Unit::Nanoseconds => "ns",
            Unit::Tebibytes => "TiB",
            Unit::Gigibytes => "GiB",
            Unit::Mebibytes => "MiB",
            Unit::Kibibytes => "KiB",
            Unit::Bytes => "B",
            Unit::TerabitsPerSecond => "Tbps",
            Unit::GigabitsPerSecond => "Gbps",
            Unit::MegabitsPerSecond => "Mbps",
            Unit::KilobitsPerSecond => "kbps",
            Unit::BitsPerSecond => "bps",
            Unit::CountPerSecond => "/s",
        }
    }

    /// Converts the string representation of a unit back into `Unit` if possible.
    ///
    /// The value passed here should match the output of [`Unit::as_str`].
    pub fn from_string(s: &str) -> Option<Unit> {
        match s {
            "count" => Some(Unit::Count),
            "percent" => Some(Unit::Percent),
            "seconds" => Some(Unit::Seconds),
            "milliseconds" => Some(Unit::Milliseconds),
            "microseconds" => Some(Unit::Microseconds),
            "nanoseconds" => Some(Unit::Nanoseconds),
            "tebibytes" => Some(Unit::Tebibytes),
            "gigibytes" => Some(Unit::Gigibytes),
            "mebibytes" => Some(Unit::Mebibytes),
            "kibibytes" => Some(Unit::Kibibytes),
            "bytes" => Some(Unit::Bytes),
            "terabits_per_second" => Some(Unit::TerabitsPerSecond),
            "gigabits_per_second" => Some(Unit::GigabitsPerSecond),
            "megabits_per_second" => Some(Unit::MegabitsPerSecond),
            "kilobits_per_second" => Some(Unit::KilobitsPerSecond),
            "bits_per_second" => Some(Unit::BitsPerSecond),
            "count_per_second" => Some(Unit::CountPerSecond),
            _ => None,
        }
    }

    /// Whether or not this unit relates to the measurement of time.
    pub fn is_time_based(&self) -> bool {
        matches!(self, Unit::Seconds | Unit::Milliseconds | Unit::Microseconds | Unit::Nanoseconds)
    }

    /// Whether or not this unit relates to the measurement of data.
    pub fn is_data_based(&self) -> bool {
        matches!(
            self,
            Unit::Tebibytes
                | Unit::Gigibytes
                | Unit::Mebibytes
                | Unit::Kibibytes
                | Unit::Bytes
                | Unit::TerabitsPerSecond
                | Unit::GigabitsPerSecond
                | Unit::MegabitsPerSecond
                | Unit::KilobitsPerSecond
                | Unit::BitsPerSecond
        )
    }

    /// Whether or not this unit relates to the measurement of data rates.
    pub fn is_data_rate_based(&self) -> bool {
        matches!(
            self,
            Unit::TerabitsPerSecond
                | Unit::GigabitsPerSecond
                | Unit::MegabitsPerSecond
                | Unit::KilobitsPerSecond
                | Unit::BitsPerSecond
        )
    }
}

/// An object which can be converted into a `f64` representation.
///
/// This trait provides a mechanism for existing types, which have a natural representation
/// as a 64-bit floating-point number, to be transparently passed in when recording a histogram.
pub trait IntoF64 {
    /// Converts this object to its `f64` representation.
    fn into_f64(self) -> f64;
}

impl IntoF64 for f64 {
    fn into_f64(self) -> f64 {
        self
    }
}

impl IntoF64 for core::time::Duration {
    fn into_f64(self) -> f64 {
        self.as_secs_f64()
    }
}

/// Helper method to allow monomorphization of values passed to the `histogram!` macro.
#[doc(hidden)]
pub fn __into_f64<V: IntoF64>(value: V) -> f64 {
    value.into_f64()
}

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

    #[test]
    fn test_unit_conversions() {
        let all_variants = vec![
            Unit::Count,
            Unit::Percent,
            Unit::Seconds,
            Unit::Milliseconds,
            Unit::Microseconds,
            Unit::Nanoseconds,
            Unit::Tebibytes,
            Unit::Gigibytes,
            Unit::Mebibytes,
            Unit::Kibibytes,
            Unit::Bytes,
            Unit::TerabitsPerSecond,
            Unit::GigabitsPerSecond,
            Unit::MegabitsPerSecond,
            Unit::KilobitsPerSecond,
            Unit::BitsPerSecond,
            Unit::CountPerSecond,
        ];

        for variant in all_variants {
            let s = variant.as_str();
            let parsed = Unit::from_string(s);
            assert_eq!(Some(variant), parsed);
        }
    }
}