cbor_core/
epoch_time.rs

1use std::time::{Duration, SystemTime};
2
3use crate::{Error, Result, Value, tag};
4
5#[derive(Debug, Clone, Copy, PartialEq)]
6enum Inner {
7    Int(u64),
8    Float(f64),
9}
10
11/// Helper for validated epoch time construction.
12///
13/// Wraps a non-negative integer or finite float in the range 0 to
14/// 253402300799, as required by the CBOR::Core draft. Implements
15/// `TryFrom` for all integer and float primitives as well as
16/// [`SystemTime`], so that [`Value::epoch_time`] can accept all of
17/// these through a single `TryInto<EpochTime>` bound.
18///
19/// Whole-second values are stored as integers; sub-second values
20/// (from floats or `SystemTime` with nanoseconds) are stored as
21/// floats. Converting to [`Value`] produces a tag 1 wrapper.
22#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
23pub struct EpochTime(Inner);
24
25impl Eq for Inner {} // our f64 is always finite
26
27impl Ord for Inner {
28    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
29        match (self, other) {
30            (Self::Int(a), Self::Int(b)) => a.cmp(b),
31            (Self::Float(a), Self::Float(b)) => a.total_cmp(b),
32            // Max epoch value (253402300799) fits in 38 bits, well within f64's
33            // 52-bit mantissa, so the cast is always exact.
34            (Self::Int(a), Self::Float(b)) => (*a as f64).total_cmp(b),
35            (Self::Float(a), Self::Int(b)) => a.total_cmp(&(*b as f64)),
36        }
37    }
38}
39
40impl PartialOrd for Inner {
41    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
42        Some(self.cmp(other))
43    }
44}
45
46impl std::hash::Hash for Inner {
47    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
48        core::mem::discriminant(self).hash(state);
49        match self {
50            Inner::Int(x) => x.hash(state),
51            Inner::Float(x) => x.to_bits().hash(state),
52        }
53    }
54}
55
56impl From<EpochTime> for Value {
57    fn from(value: EpochTime) -> Self {
58        match value.0 {
59            Inner::Int(int) => Self::tag(tag::EPOCH_TIME, int),
60            Inner::Float(float) => Self::tag(tag::EPOCH_TIME, float),
61        }
62    }
63}
64
65impl TryFrom<SystemTime> for EpochTime {
66    type Error = Error;
67
68    fn try_from(value: SystemTime) -> Result<Self> {
69        let time = value
70            .duration_since(SystemTime::UNIX_EPOCH)
71            .or(Err(Error::InvalidValue))?;
72
73        if time > Duration::from_secs(253402300799) {
74            Err(Error::InvalidValue)
75        } else if time.subsec_nanos() == 0 {
76            Ok(Self(Inner::Int(time.as_secs())))
77        } else {
78            Ok(Self(Inner::Float(time.as_secs_f64())))
79        }
80    }
81}
82
83fn from_int<T: TryInto<u64>>(value: T) -> Result<EpochTime> {
84    let value = value.try_into().or(Err(Error::InvalidValue))?;
85
86    if (0..=253402300799).contains(&value) {
87        Ok(EpochTime(Inner::Int(value)))
88    } else {
89        Err(Error::InvalidValue)
90    }
91}
92
93macro_rules! try_from {
94    ($type:ty) => {
95        impl TryFrom<$type> for EpochTime {
96            type Error = Error;
97            fn try_from(value: $type) -> Result<Self> {
98                from_int(value)
99            }
100        }
101    };
102}
103
104try_from!(u8);
105try_from!(u16);
106try_from!(u32);
107try_from!(u64);
108try_from!(u128);
109try_from!(usize);
110
111try_from!(i8);
112try_from!(i16);
113try_from!(i32);
114try_from!(i64);
115try_from!(i128);
116try_from!(isize);
117
118impl TryFrom<f32> for EpochTime {
119    type Error = Error;
120
121    fn try_from(value: f32) -> Result<Self> {
122        Self::try_from(f64::from(value))
123    }
124}
125impl TryFrom<f64> for EpochTime {
126    type Error = Error;
127
128    fn try_from(value: f64) -> Result<Self> {
129        if value.is_finite() && (0.0..=253402300799.0).contains(&value) {
130            Ok(Self(Inner::Float(value)))
131        } else {
132            Err(Error::InvalidValue)
133        }
134    }
135}
cbor_core/epoch_time.rs

cbor_core/
epoch_time.rs
