use std::convert::TryInto;use std::io;use std::ops::Sub; use crate::Time; /// Indicates if a number is positive or negative for use in [`Time`].#[derive(PartialEq, Eq, Debug, Hash, Ord, PartialOrd, Clone, Copy)]#[cfg_attr(feature = "serde1", derive(serde::Serialize, serde::Deserialize))]#[allow(missing_docs)]pub enum Sign {    Plus,    Minus,} impl From<i32> for Sign {    fn from(v: i32) -> Self {        if v < 0 {            Sign::Minus        } else {            Sign::Plus        }    }} impl Default for Time {    fn default() -> Self {        Time {            seconds_since_unix_epoch: 0,            offset_in_seconds: 0,            sign: Sign::Plus,        }    }} /// Instantiationimpl Time {    /// Create a new instance from seconds and offset.    pub fn new(seconds_since_unix_epoch: u32, offset_in_seconds: i32) -> Self {        Time {            seconds_since_unix_epoch,            offset_in_seconds,            sign: offset_in_seconds.into(),        }    }     /// Return the current time without figuring out a timezone offset    pub fn now_utc() -> Self {        let seconds_since_unix_epoch = time::OffsetDateTime::now_utc()            .sub(std::time::SystemTime::UNIX_EPOCH)            .whole_seconds()            .try_into()            .expect("this is not year 2038");        Self {            seconds_since_unix_epoch,            offset_in_seconds: 0,            sign: Sign::Plus,        }    }     /// Return the current local time, or `None` if the local time wasn't available.    pub fn now_local() -> Option<Self> {        let now = time::OffsetDateTime::now_utc();        let seconds_since_unix_epoch = now            .sub(std::time::SystemTime::UNIX_EPOCH)            .whole_seconds()            .try_into()            .expect("this is not year 2038");        // TODO: make this work without cfg(unsound_local_offset), see        //       https://github.com/time-rs/time/issues/293#issuecomment-909158529        let offset = time::UtcOffset::local_offset_at(now).ok()?;        Self {            seconds_since_unix_epoch,            offset_in_seconds: offset.whole_seconds(),            sign: Sign::Plus,        }        .into()    }     /// Return the current local time, or the one at UTC if the local time wasn't available.    pub fn now_local_or_utc() -> Self {        let now = time::OffsetDateTime::now_utc();        let seconds_since_unix_epoch = now            .sub(std::time::SystemTime::UNIX_EPOCH)            .whole_seconds()            .try_into()            .expect("this is not year 2038");        // TODO: make this work without cfg(unsound_local_offset), see        //       https://github.com/time-rs/time/issues/293#issuecomment-909158529        let offset_in_seconds = time::UtcOffset::local_offset_at(now)            .map(|ofs| ofs.whole_seconds())            .unwrap_or(0);        Self {            seconds_since_unix_epoch,            offset_in_seconds,            sign: Sign::Plus,        }    }} impl Time {    /// Return true if this time has been initialized to anything non-default, i.e. 0.    pub fn is_set(&self) -> bool {        *self != Self::default()    }     /// Return the passed seconds since epoch since this signature was made.    pub fn seconds(&self) -> u32 {        self.seconds_since_unix_epoch    }     /// Serialize this instance to `out` in a format suitable for use in header fields of serialized git commits or tags.    pub fn write_to(&self, mut out: impl io::Write) -> io::Result<()> {        let mut itoa = itoa::Buffer::new();        out.write_all(itoa.format(self.seconds_since_unix_epoch).as_bytes())?;        out.write_all(b" ")?;        out.write_all(match self.sign {            Sign::Plus => b"+",            Sign::Minus => b"-",        })?;         const ZERO: &[u8; 1] = b"0";         const SECONDS_PER_HOUR: i32 = 60 * 60;        let offset = self.offset_in_seconds.abs();        let hours = offset / SECONDS_PER_HOUR;        assert!(hours < 25, "offset is more than a day: {}", hours);        let minutes = (offset - (hours * SECONDS_PER_HOUR)) / 60;         if hours < 10 {            out.write_all(ZERO)?;        }        out.write_all(itoa.format(hours).as_bytes())?;         if minutes < 10 {            out.write_all(ZERO)?;        }        out.write_all(itoa.format(minutes).as_bytes()).map(|_| ())    }     /// Computes the number of bytes necessary to render this time.    pub fn size(&self) -> usize {        // TODO: this is not year 2038 safe…but we also can't parse larger numbers (or represent them) anyway. It's a trap nonetheless        //       that can be fixed by increasing the size to usize.        (if self.seconds_since_unix_epoch >= 1_000_000_000 {            10        } else if self.seconds_since_unix_epoch >= 100_000_000 {            9        } else if self.seconds_since_unix_epoch >= 10_000_000 {            8        } else if self.seconds_since_unix_epoch >= 1_000_000 {            7        } else if self.seconds_since_unix_epoch >= 100_000 {            6        } else if self.seconds_since_unix_epoch >= 10_000 {            5        } else if self.seconds_since_unix_epoch >= 1_000 {            4        } else if self.seconds_since_unix_epoch >= 100 {            3        } else if self.seconds_since_unix_epoch >= 10 {            2        } else {            1        }) + 2 /*space + sign*/ + 2 /*hours*/ + 2 /*minutes*/    }}