bitcode/derive/
duration.rs

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1use crate::coder::{Buffer, Decoder, Encoder, Result, View};
2use crate::{Decode, Encode};
3use alloc::vec::Vec;
4use bytemuck::CheckedBitPattern;
5use core::num::NonZeroUsize;
6use core::time::Duration;
7
8#[derive(Default)]
9pub struct DurationEncoder {
10    secs: <u64 as Encode>::Encoder,
11    subsec_nanos: <u32 as Encode>::Encoder,
12}
13impl Encoder<Duration> for DurationEncoder {
14    #[inline(always)]
15    fn encode(&mut self, t: &Duration) {
16        self.secs.encode(&t.as_secs());
17        self.subsec_nanos.encode(&t.subsec_nanos());
18    }
19}
20impl Buffer for DurationEncoder {
21    fn collect_into(&mut self, out: &mut Vec<u8>) {
22        self.secs.collect_into(out);
23        self.subsec_nanos.collect_into(out);
24    }
25
26    fn reserve(&mut self, additional: NonZeroUsize) {
27        self.secs.reserve(additional);
28        self.subsec_nanos.reserve(additional);
29    }
30}
31impl Encode for Duration {
32    type Encoder = DurationEncoder;
33}
34
35/// A u32 guaranteed to be < 1 billion. Prevents Duration::new from panicking.
36#[derive(Copy, Clone)]
37#[repr(transparent)]
38struct Nanoseconds(u32);
39// Safety: u32 and Nanoseconds have the same layout since Nanoseconds is #[repr(transparent)].
40unsafe impl CheckedBitPattern for Nanoseconds {
41    type Bits = u32;
42    #[inline(always)]
43    fn is_valid_bit_pattern(bits: &Self::Bits) -> bool {
44        *bits < 1_000_000_000
45    }
46}
47impl<'a> Decode<'a> for Nanoseconds {
48    type Decoder = crate::int::CheckedIntDecoder<'a, Nanoseconds, u32>;
49}
50
51#[derive(Default)]
52pub struct DurationDecoder<'a> {
53    secs: <u64 as Decode<'a>>::Decoder,
54    subsec_nanos: <Nanoseconds as Decode<'a>>::Decoder,
55}
56impl<'a> View<'a> for DurationDecoder<'a> {
57    fn populate(&mut self, input: &mut &'a [u8], length: usize) -> Result<()> {
58        self.secs.populate(input, length)?;
59        self.subsec_nanos.populate(input, length)?;
60        Ok(())
61    }
62}
63impl<'a> Decoder<'a, Duration> for DurationDecoder<'a> {
64    #[inline(always)]
65    fn decode(&mut self) -> Duration {
66        let secs = self.secs.decode();
67        let Nanoseconds(subsec_nanos) = self.subsec_nanos.decode();
68        // Makes Duration::new 4x faster since it can skip checks and division.
69        // Safety: impl CheckedBitPattern for Nanoseconds guarantees this.
70        unsafe {
71            if !Nanoseconds::is_valid_bit_pattern(&subsec_nanos) {
72                core::hint::unreachable_unchecked();
73            }
74        }
75        Duration::new(secs, subsec_nanos)
76    }
77}
78impl<'a> Decode<'a> for Duration {
79    type Decoder = DurationDecoder<'a>;
80}
81
82#[cfg(test)]
83mod tests {
84    #[test]
85    fn test() {
86        assert!(crate::decode::<Duration>(&crate::encode(&(u64::MAX, 999_999_999))).is_ok());
87        assert!(crate::decode::<Duration>(&crate::encode(&(u64::MAX, 1_000_000_000))).is_err());
88    }
89
90    use alloc::vec::Vec;
91    use core::time::Duration;
92    fn bench_data() -> Vec<Duration> {
93        crate::random_data(1000)
94            .into_iter()
95            .map(|(s, n): (_, u32)| Duration::new(s, n % 1_000_000_000))
96            .collect()
97    }
98    crate::bench_encode_decode!(duration_vec: Vec<_>);
99}
bitcode/derive/duration.rs

bitcode/derive/
duration.rs
