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+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package time provides functionality for measuring and displaying time.
+//
+// The calendrical calculations always assume a Gregorian calendar, with
+// no leap seconds.
+//
+// Monotonic Clocks
+//
+// Operating systems provide both a “wall clock,” which is subject to
+// changes for clock synchronization, and a “monotonic clock,” which is
+// not. The general rule is that the wall clock is for telling time and
+// the monotonic clock is for measuring time. Rather than split the API,
+// in this package the Time returned by time.Now contains both a wall
+// clock reading and a monotonic clock reading; later time-telling
+// operations use the wall clock reading, but later time-measuring
+// operations, specifically comparisons and subtractions, use the
+// monotonic clock reading.
+//
+// For example, this code always computes a positive elapsed time of
+// approximately 20 milliseconds, even if the wall clock is changed during
+// the operation being timed:
+//
+// start := time.Now()
+// ... operation that takes 20 milliseconds ...
+// t := time.Now()
+// elapsed := t.Sub(start)
+//
+// Other idioms, such as time.Since(start), time.Until(deadline), and
+// time.Now().Before(deadline), are similarly robust against wall clock
+// resets.
+//
+// The rest of this section gives the precise details of how operations
+// use monotonic clocks, but understanding those details is not required
+// to use this package.
+//
+// The Time returned by time.Now contains a monotonic clock reading.
+// If Time t has a monotonic clock reading, t.Add adds the same duration to
+// both the wall clock and monotonic clock readings to compute the result.
+// Because t.AddDate(y, m, d), t.Round(d), and t.Truncate(d) are wall time
+// computations, they always strip any monotonic clock reading from their results.
+// Because t.In, t.Local, and t.UTC are used for their effect on the interpretation
+// of the wall time, they also strip any monotonic clock reading from their results.
+// The canonical way to strip a monotonic clock reading is to use t = t.Round(0).
+//
+// If Times t and u both contain monotonic clock readings, the operations
+// t.After(u), t.Before(u), t.Equal(u), and t.Sub(u) are carried out
+// using the monotonic clock readings alone, ignoring the wall clock
+// readings. If either t or u contains no monotonic clock reading, these
+// operations fall back to using the wall clock readings.
+//
+// On some systems the monotonic clock will stop if the computer goes to sleep.
+// On such a system, t.Sub(u) may not accurately reflect the actual
+// time that passed between t and u.
+//
+// Because the monotonic clock reading has no meaning outside
+// the current process, the serialized forms generated by t.GobEncode,
+// t.MarshalBinary, t.MarshalJSON, and t.MarshalText omit the monotonic
+// clock reading, and t.Format provides no format for it. Similarly, the
+// constructors time.Date, time.Parse, time.ParseInLocation, and time.Unix,
+// as well as the unmarshalers t.GobDecode, t.UnmarshalBinary.
+// t.UnmarshalJSON, and t.UnmarshalText always create times with
+// no monotonic clock reading.
+//
+// Note that the Go == operator compares not just the time instant but
+// also the Location and the monotonic clock reading. See the
+// documentation for the Time type for a discussion of equality
+// testing for Time values.
+//
+// For debugging, the result of t.String does include the monotonic
+// clock reading if present. If t != u because of different monotonic clock readings,
+// that difference will be visible when printing t.String() and u.String().
+//
+package time
+
+import (
+ "errors"
+ _ "unsafe" // for go:linkname
+)
+
+// A Time represents an instant in time with nanosecond precision.
+//
+// Programs using times should typically store and pass them as values,
+// not pointers. That is, time variables and struct fields should be of
+// type time.Time, not *time.Time.
+//
+// A Time value can be used by multiple goroutines simultaneously except
+// that the methods GobDecode, UnmarshalBinary, UnmarshalJSON and
+// UnmarshalText are not concurrency-safe.
+//
+// Time instants can be compared using the Before, After, and Equal methods.
+// The Sub method subtracts two instants, producing a Duration.
+// The Add method adds a Time and a Duration, producing a Time.
+//
+// The zero value of type Time is January 1, year 1, 00:00:00.000000000 UTC.
+// As this time is unlikely to come up in practice, the IsZero method gives
+// a simple way of detecting a time that has not been initialized explicitly.
+//
+// Each Time has associated with it a Location, consulted when computing the
+// presentation form of the time, such as in the Format, Hour, and Year methods.
+// The methods Local, UTC, and In return a Time with a specific location.
+// Changing the location in this way changes only the presentation; it does not
+// change the instant in time being denoted and therefore does not affect the
+// computations described in earlier paragraphs.
+//
+// Representations of a Time value saved by the GobEncode, MarshalBinary,
+// MarshalJSON, and MarshalText methods store the Time.Location's offset, but not
+// the location name. They therefore lose information about Daylight Saving Time.
+//
+// In addition to the required “wall clock” reading, a Time may contain an optional
+// reading of the current process's monotonic clock, to provide additional precision
+// for comparison or subtraction.
+// See the “Monotonic Clocks” section in the package documentation for details.
+//
+// Note that the Go == operator compares not just the time instant but also the
+// Location and the monotonic clock reading. Therefore, Time values should not
+// be used as map or database keys without first guaranteeing that the
+// identical Location has been set for all values, which can be achieved
+// through use of the UTC or Local method, and that the monotonic clock reading
+// has been stripped by setting t = t.Round(0). In general, prefer t.Equal(u)
+// to t == u, since t.Equal uses the most accurate comparison available and
+// correctly handles the case when only one of its arguments has a monotonic
+// clock reading.
+//
+type Time struct {
+ // wall and ext encode the wall time seconds, wall time nanoseconds,
+ // and optional monotonic clock reading in nanoseconds.
+ //
+ // From high to low bit position, wall encodes a 1-bit flag (hasMonotonic),
+ // a 33-bit seconds field, and a 30-bit wall time nanoseconds field.
+ // The nanoseconds field is in the range [0, 999999999].
+ // If the hasMonotonic bit is 0, then the 33-bit field must be zero
+ // and the full signed 64-bit wall seconds since Jan 1 year 1 is stored in ext.
+ // If the hasMonotonic bit is 1, then the 33-bit field holds a 33-bit
+ // unsigned wall seconds since Jan 1 year 1885, and ext holds a
+ // signed 64-bit monotonic clock reading, nanoseconds since process start.
+ wall uint64
+ ext int64
+
+ // loc specifies the Location that should be used to
+ // determine the minute, hour, month, day, and year
+ // that correspond to this Time.
+ // The nil location means UTC.
+ // All UTC times are represented with loc==nil, never loc==&utcLoc.
+ loc *Location
+}
+
+const (
+ hasMonotonic = 1 << 63
+ maxWall = wallToInternal + (1<<33 - 1) // year 2157
+ minWall = wallToInternal // year 1885
+ nsecMask = 1<<30 - 1
+ nsecShift = 30
+)
+
+// These helpers for manipulating the wall and monotonic clock readings
+// take pointer receivers, even when they don't modify the time,
+// to make them cheaper to call.
+
+// nsec returns the time's nanoseconds.
+func (t *Time) nsec() int32 {
+ return int32(t.wall & nsecMask)
+}
+
+// sec returns the time's seconds since Jan 1 year 1.
+func (t *Time) sec() int64 {
+ if t.wall&hasMonotonic != 0 {
+ return wallToInternal + int64(t.wall<<1>>(nsecShift+1))
+ }
+ return t.ext
+}
+
+// unixSec returns the time's seconds since Jan 1 1970 (Unix time).
+func (t *Time) unixSec() int64 { return t.sec() + internalToUnix }
+
+// addSec adds d seconds to the time.
+func (t *Time) addSec(d int64) {
+ if t.wall&hasMonotonic != 0 {
+ sec := int64(t.wall << 1 >> (nsecShift + 1))
+ dsec := sec + d
+ if 0 <= dsec && dsec <= 1<<33-1 {
+ t.wall = t.wall&nsecMask | uint64(dsec)<<nsecShift | hasMonotonic
+ return
+ }
+ // Wall second now out of range for packed field.
+ // Move to ext.
+ t.stripMono()
+ }
+
+ // Check if the sum of t.ext and d overflows and handle it properly.
+ sum := t.ext + d
+ if (sum > t.ext) == (d > 0) {
+ t.ext = sum
+ } else if d > 0 {
+ t.ext = 1<<63 - 1
+ } else {
+ t.ext = -(1<<63 - 1)
+ }
+}
+
+// setLoc sets the location associated with the time.
+func (t *Time) setLoc(loc *Location) {
+ if loc == &utcLoc {
+ loc = nil
+ }
+ t.stripMono()
+ t.loc = loc
+}
+
+// stripMono strips the monotonic clock reading in t.
+func (t *Time) stripMono() {
+ if t.wall&hasMonotonic != 0 {
+ t.ext = t.sec()
+ t.wall &= nsecMask
+ }
+}
+
+// setMono sets the monotonic clock reading in t.
+// If t cannot hold a monotonic clock reading,
+// because its wall time is too large,
+// setMono is a no-op.
+func (t *Time) setMono(m int64) {
+ if t.wall&hasMonotonic == 0 {
+ sec := t.ext
+ if sec < minWall || maxWall < sec {
+ return
+ }
+ t.wall |= hasMonotonic | uint64(sec-minWall)<<nsecShift
+ }
+ t.ext = m
+}
+
+// mono returns t's monotonic clock reading.
+// It returns 0 for a missing reading.
+// This function is used only for testing,
+// so it's OK that technically 0 is a valid
+// monotonic clock reading as well.
+func (t *Time) mono() int64 {
+ if t.wall&hasMonotonic == 0 {
+ return 0
+ }
+ return t.ext
+}
+
+// After reports whether the time instant t is after u.
+func (t Time) After(u Time) bool {
+ if t.wall&u.wall&hasMonotonic != 0 {
+ return t.ext > u.ext
+ }
+ ts := t.sec()
+ us := u.sec()
+ return ts > us || ts == us && t.nsec() > u.nsec()
+}
+
+// Before reports whether the time instant t is before u.
+func (t Time) Before(u Time) bool {
+ if t.wall&u.wall&hasMonotonic != 0 {
+ return t.ext < u.ext
+ }
+ ts := t.sec()
+ us := u.sec()
+ return ts < us || ts == us && t.nsec() < u.nsec()
+}
+
+// Equal reports whether t and u represent the same time instant.
+// Two times can be equal even if they are in different locations.
+// For example, 6:00 +0200 and 4:00 UTC are Equal.
+// See the documentation on the Time type for the pitfalls of using == with
+// Time values; most code should use Equal instead.
+func (t Time) Equal(u Time) bool {
+ if t.wall&u.wall&hasMonotonic != 0 {
+ return t.ext == u.ext
+ }
+ return t.sec() == u.sec() && t.nsec() == u.nsec()
+}
+
+// A Month specifies a month of the year (January = 1, ...).
+type Month int
+
+const (
+ January Month = 1 + iota
+ February
+ March
+ April
+ May
+ June
+ July
+ August
+ September
+ October
+ November
+ December
+)
+
+// String returns the English name of the month ("January", "February", ...).
+func (m Month) String() string {
+ if January <= m && m <= December {
+ return longMonthNames[m-1]
+ }
+ buf := make([]byte, 20)
+ n := fmtInt(buf, uint64(m))
+ return "%!Month(" + string(buf[n:]) + ")"
+}
+
+// A Weekday specifies a day of the week (Sunday = 0, ...).
+type Weekday int
+
+const (
+ Sunday Weekday = iota
+ Monday
+ Tuesday
+ Wednesday
+ Thursday
+ Friday
+ Saturday
+)
+
+// String returns the English name of the day ("Sunday", "Monday", ...).
+func (d Weekday) String() string {
+ if Sunday <= d && d <= Saturday {
+ return longDayNames[d]
+ }
+ buf := make([]byte, 20)
+ n := fmtInt(buf, uint64(d))
+ return "%!Weekday(" + string(buf[n:]) + ")"
+}
+
+// Computations on time.
+//
+// The zero value for a Time is defined to be
+// January 1, year 1, 00:00:00.000000000 UTC
+// which (1) looks like a zero, or as close as you can get in a date
+// (1-1-1 00:00:00 UTC), (2) is unlikely enough to arise in practice to
+// be a suitable "not set" sentinel, unlike Jan 1 1970, and (3) has a
+// non-negative year even in time zones west of UTC, unlike 1-1-0
+// 00:00:00 UTC, which would be 12-31-(-1) 19:00:00 in New York.
+//
+// The zero Time value does not force a specific epoch for the time
+// representation. For example, to use the Unix epoch internally, we
+// could define that to distinguish a zero value from Jan 1 1970, that
+// time would be represented by sec=-1, nsec=1e9. However, it does
+// suggest a representation, namely using 1-1-1 00:00:00 UTC as the
+// epoch, and that's what we do.
+//
+// The Add and Sub computations are oblivious to the choice of epoch.
+//
+// The presentation computations - year, month, minute, and so on - all
+// rely heavily on division and modulus by positive constants. For
+// calendrical calculations we want these divisions to round down, even
+// for negative values, so that the remainder is always positive, but
+// Go's division (like most hardware division instructions) rounds to
+// zero. We can still do those computations and then adjust the result
+// for a negative numerator, but it's annoying to write the adjustment
+// over and over. Instead, we can change to a different epoch so long
+// ago that all the times we care about will be positive, and then round
+// to zero and round down coincide. These presentation routines already
+// have to add the zone offset, so adding the translation to the
+// alternate epoch is cheap. For example, having a non-negative time t
+// means that we can write
+//
+// sec = t % 60
+//
+// instead of
+//
+// sec = t % 60
+// if sec < 0 {
+// sec += 60
+// }
+//
+// everywhere.
+//
+// The calendar runs on an exact 400 year cycle: a 400-year calendar
+// printed for 1970-2369 will apply as well to 2370-2769. Even the days
+// of the week match up. It simplifies the computations to choose the
+// cycle boundaries so that the exceptional years are always delayed as
+// long as possible. That means choosing a year equal to 1 mod 400, so
+// that the first leap year is the 4th year, the first missed leap year
+// is the 100th year, and the missed missed leap year is the 400th year.
+// So we'd prefer instead to print a calendar for 2001-2400 and reuse it
+// for 2401-2800.
+//
+// Finally, it's convenient if the delta between the Unix epoch and
+// long-ago epoch is representable by an int64 constant.
+//
+// These three considerations—choose an epoch as early as possible, that
+// uses a year equal to 1 mod 400, and that is no more than 2⁶³ seconds
+// earlier than 1970—bring us to the year -292277022399. We refer to
+// this year as the absolute zero year, and to times measured as a uint64
+// seconds since this year as absolute times.
+//
+// Times measured as an int64 seconds since the year 1—the representation
+// used for Time's sec field—are called internal times.
+//
+// Times measured as an int64 seconds since the year 1970 are called Unix
+// times.
+//
+// It is tempting to just use the year 1 as the absolute epoch, defining
+// that the routines are only valid for years >= 1. However, the
+// routines would then be invalid when displaying the epoch in time zones
+// west of UTC, since it is year 0. It doesn't seem tenable to say that
+// printing the zero time correctly isn't supported in half the time
+// zones. By comparison, it's reasonable to mishandle some times in
+// the year -292277022399.
+//
+// All this is opaque to clients of the API and can be changed if a
+// better implementation presents itself.
+
+const (
+ // The unsigned zero year for internal calculations.
+ // Must be 1 mod 400, and times before it will not compute correctly,
+ // but otherwise can be changed at will.
+ absoluteZeroYear = -292277022399
+
+ // The year of the zero Time.
+ // Assumed by the unixToInternal computation below.
+ internalYear = 1
+
+ // Offsets to convert between internal and absolute or Unix times.
+ absoluteToInternal int64 = (absoluteZeroYear - internalYear) * 365.2425 * secondsPerDay
+ internalToAbsolute = -absoluteToInternal
+
+ unixToInternal int64 = (1969*365 + 1969/4 - 1969/100 + 1969/400) * secondsPerDay
+ internalToUnix int64 = -unixToInternal
+
+ wallToInternal int64 = (1884*365 + 1884/4 - 1884/100 + 1884/400) * secondsPerDay
+ internalToWall int64 = -wallToInternal
+)
+
+// IsZero reports whether t represents the zero time instant,
+// January 1, year 1, 00:00:00 UTC.
+func (t Time) IsZero() bool {
+ return t.sec() == 0 && t.nsec() == 0
+}
+
+// abs returns the time t as an absolute time, adjusted by the zone offset.
+// It is called when computing a presentation property like Month or Hour.
+func (t Time) abs() uint64 {
+ l := t.loc
+ // Avoid function calls when possible.
+ if l == nil || l == &localLoc {
+ l = l.get()
+ }
+ sec := t.unixSec()
+ if l != &utcLoc {
+ if l.cacheZone != nil && l.cacheStart <= sec && sec < l.cacheEnd {
+ sec += int64(l.cacheZone.offset)
+ } else {
+ _, offset, _, _, _ := l.lookup(sec)
+ sec += int64(offset)
+ }
+ }
+ return uint64(sec + (unixToInternal + internalToAbsolute))
+}
+
+// locabs is a combination of the Zone and abs methods,
+// extracting both return values from a single zone lookup.
+func (t Time) locabs() (name string, offset int, abs uint64) {
+ l := t.loc
+ if l == nil || l == &localLoc {
+ l = l.get()
+ }
+ // Avoid function call if we hit the local time cache.
+ sec := t.unixSec()
+ if l != &utcLoc {
+ if l.cacheZone != nil && l.cacheStart <= sec && sec < l.cacheEnd {
+ name = l.cacheZone.name
+ offset = l.cacheZone.offset
+ } else {
+ name, offset, _, _, _ = l.lookup(sec)
+ }
+ sec += int64(offset)
+ } else {
+ name = "UTC"
+ }
+ abs = uint64(sec + (unixToInternal + internalToAbsolute))
+ return
+}
+
+// Date returns the year, month, and day in which t occurs.
+func (t Time) Date() (year int, month Month, day int) {
+ year, month, day, _ = t.date(true)
+ return
+}
+
+// Year returns the year in which t occurs.
+func (t Time) Year() int {
+ year, _, _, _ := t.date(false)
+ return year
+}
+
+// Month returns the month of the year specified by t.
+func (t Time) Month() Month {
+ _, month, _, _ := t.date(true)
+ return month
+}
+
+// Day returns the day of the month specified by t.
+func (t Time) Day() int {
+ _, _, day, _ := t.date(true)
+ return day
+}
+
+// Weekday returns the day of the week specified by t.
+func (t Time) Weekday() Weekday {
+ return absWeekday(t.abs())
+}
+
+// absWeekday is like Weekday but operates on an absolute time.
+func absWeekday(abs uint64) Weekday {
+ // January 1 of the absolute year, like January 1 of 2001, was a Monday.
+ sec := (abs + uint64(Monday)*secondsPerDay) % secondsPerWeek
+ return Weekday(int(sec) / secondsPerDay)
+}
+
+// ISOWeek returns the ISO 8601 year and week number in which t occurs.
+// Week ranges from 1 to 53. Jan 01 to Jan 03 of year n might belong to
+// week 52 or 53 of year n-1, and Dec 29 to Dec 31 might belong to week 1
+// of year n+1.
+func (t Time) ISOWeek() (year, week int) {
+ // According to the rule that the first calendar week of a calendar year is
+ // the week including the first Thursday of that year, and that the last one is
+ // the week immediately preceding the first calendar week of the next calendar year.
+ // See https://www.iso.org/obp/ui#iso:std:iso:8601:-1:ed-1:v1:en:term:3.1.1.23 for details.
+
+ // weeks start with Monday
+ // Monday Tuesday Wednesday Thursday Friday Saturday Sunday
+ // 1 2 3 4 5 6 7
+ // +3 +2 +1 0 -1 -2 -3
+ // the offset to Thursday
+ abs := t.abs()
+ d := Thursday - absWeekday(abs)
+ // handle Sunday
+ if d == 4 {
+ d = -3
+ }
+ // find the Thursday of the calendar week
+ abs += uint64(d) * secondsPerDay
+ year, _, _, yday := absDate(abs, false)
+ return year, yday/7 + 1
+}
+
+// Clock returns the hour, minute, and second within the day specified by t.
+func (t Time) Clock() (hour, min, sec int) {
+ return absClock(t.abs())
+}
+
+// absClock is like clock but operates on an absolute time.
+func absClock(abs uint64) (hour, min, sec int) {
+ sec = int(abs % secondsPerDay)
+ hour = sec / secondsPerHour
+ sec -= hour * secondsPerHour
+ min = sec / secondsPerMinute
+ sec -= min * secondsPerMinute
+ return
+}
+
+// Hour returns the hour within the day specified by t, in the range [0, 23].
+func (t Time) Hour() int {
+ return int(t.abs()%secondsPerDay) / secondsPerHour
+}
+
+// Minute returns the minute offset within the hour specified by t, in the range [0, 59].
+func (t Time) Minute() int {
+ return int(t.abs()%secondsPerHour) / secondsPerMinute
+}
+
+// Second returns the second offset within the minute specified by t, in the range [0, 59].
+func (t Time) Second() int {
+ return int(t.abs() % secondsPerMinute)
+}
+
+// Nanosecond returns the nanosecond offset within the second specified by t,
+// in the range [0, 999999999].
+func (t Time) Nanosecond() int {
+ return int(t.nsec())
+}
+
+// YearDay returns the day of the year specified by t, in the range [1,365] for non-leap years,
+// and [1,366] in leap years.
+func (t Time) YearDay() int {
+ _, _, _, yday := t.date(false)
+ return yday + 1
+}
+
+// A Duration represents the elapsed time between two instants
+// as an int64 nanosecond count. The representation limits the
+// largest representable duration to approximately 290 years.
+type Duration int64
+
+const (
+ minDuration Duration = -1 << 63
+ maxDuration Duration = 1<<63 - 1
+)
+
+// Common durations. There is no definition for units of Day or larger
+// to avoid confusion across daylight savings time zone transitions.
+//
+// To count the number of units in a Duration, divide:
+// second := time.Second
+// fmt.Print(int64(second/time.Millisecond)) // prints 1000
+//
+// To convert an integer number of units to a Duration, multiply:
+// seconds := 10
+// fmt.Print(time.Duration(seconds)*time.Second) // prints 10s
+//
+const (
+ Nanosecond Duration = 1
+ Microsecond = 1000 * Nanosecond
+ Millisecond = 1000 * Microsecond
+ Second = 1000 * Millisecond
+ Minute = 60 * Second
+ Hour = 60 * Minute
+)
+
+// String returns a string representing the duration in the form "72h3m0.5s".
+// Leading zero units are omitted. As a special case, durations less than one
+// second format use a smaller unit (milli-, micro-, or nanoseconds) to ensure
+// that the leading digit is non-zero. The zero duration formats as 0s.
+func (d Duration) String() string {
+ // Largest time is 2540400h10m10.000000000s
+ var buf [32]byte
+ w := len(buf)
+
+ u := uint64(d)
+ neg := d < 0
+ if neg {
+ u = -u
+ }
+
+ if u < uint64(Second) {
+ // Special case: if duration is smaller than a second,
+ // use smaller units, like 1.2ms
+ var prec int
+ w--
+ buf[w] = 's'
+ w--
+ switch {
+ case u == 0:
+ return "0s"
+ case u < uint64(Microsecond):
+ // print nanoseconds
+ prec = 0
+ buf[w] = 'n'
+ case u < uint64(Millisecond):
+ // print microseconds
+ prec = 3
+ // U+00B5 'µ' micro sign == 0xC2 0xB5
+ w-- // Need room for two bytes.
+ copy(buf[w:], "µ")
+ default:
+ // print milliseconds
+ prec = 6
+ buf[w] = 'm'
+ }
+ w, u = fmtFrac(buf[:w], u, prec)
+ w = fmtInt(buf[:w], u)
+ } else {
+ w--
+ buf[w] = 's'
+
+ w, u = fmtFrac(buf[:w], u, 9)
+
+ // u is now integer seconds
+ w = fmtInt(buf[:w], u%60)
+ u /= 60
+
+ // u is now integer minutes
+ if u > 0 {
+ w--
+ buf[w] = 'm'
+ w = fmtInt(buf[:w], u%60)
+ u /= 60
+
+ // u is now integer hours
+ // Stop at hours because days can be different lengths.
+ if u > 0 {
+ w--
+ buf[w] = 'h'
+ w = fmtInt(buf[:w], u)
+ }
+ }
+ }
+
+ if neg {
+ w--
+ buf[w] = '-'
+ }
+
+ return string(buf[w:])
+}
+
+// fmtFrac formats the fraction of v/10**prec (e.g., ".12345") into the
+// tail of buf, omitting trailing zeros. It omits the decimal
+// point too when the fraction is 0. It returns the index where the
+// output bytes begin and the value v/10**prec.
+func fmtFrac(buf []byte, v uint64, prec int) (nw int, nv uint64) {
+ // Omit trailing zeros up to and including decimal point.
+ w := len(buf)
+ print := false
+ for i := 0; i < prec; i++ {
+ digit := v % 10
+ print = print || digit != 0
+ if print {
+ w--
+ buf[w] = byte(digit) + '0'
+ }
+ v /= 10
+ }
+ if print {
+ w--
+ buf[w] = '.'
+ }
+ return w, v
+}
+
+// fmtInt formats v into the tail of buf.
+// It returns the index where the output begins.
+func fmtInt(buf []byte, v uint64) int {
+ w := len(buf)
+ if v == 0 {
+ w--
+ buf[w] = '0'
+ } else {
+ for v > 0 {
+ w--
+ buf[w] = byte(v%10) + '0'
+ v /= 10
+ }
+ }
+ return w
+}
+
+// Nanoseconds returns the duration as an integer nanosecond count.
+func (d Duration) Nanoseconds() int64 { return int64(d) }
+
+// Microseconds returns the duration as an integer microsecond count.
+func (d Duration) Microseconds() int64 { return int64(d) / 1e3 }
+
+// Milliseconds returns the duration as an integer millisecond count.
+func (d Duration) Milliseconds() int64 { return int64(d) / 1e6 }
+
+// These methods return float64 because the dominant
+// use case is for printing a floating point number like 1.5s, and
+// a truncation to integer would make them not useful in those cases.
+// Splitting the integer and fraction ourselves guarantees that
+// converting the returned float64 to an integer rounds the same
+// way that a pure integer conversion would have, even in cases
+// where, say, float64(d.Nanoseconds())/1e9 would have rounded
+// differently.
+
+// Seconds returns the duration as a floating point number of seconds.
+func (d Duration) Seconds() float64 {
+ sec := d / Second
+ nsec := d % Second
+ return float64(sec) + float64(nsec)/1e9
+}
+
+// Minutes returns the duration as a floating point number of minutes.
+func (d Duration) Minutes() float64 {
+ min := d / Minute
+ nsec := d % Minute
+ return float64(min) + float64(nsec)/(60*1e9)
+}
+
+// Hours returns the duration as a floating point number of hours.
+func (d Duration) Hours() float64 {
+ hour := d / Hour
+ nsec := d % Hour
+ return float64(hour) + float64(nsec)/(60*60*1e9)
+}
+
+// Truncate returns the result of rounding d toward zero to a multiple of m.
+// If m <= 0, Truncate returns d unchanged.
+func (d Duration) Truncate(m Duration) Duration {
+ if m <= 0 {
+ return d
+ }
+ return d - d%m
+}
+
+// lessThanHalf reports whether x+x < y but avoids overflow,
+// assuming x and y are both positive (Duration is signed).
+func lessThanHalf(x, y Duration) bool {
+ return uint64(x)+uint64(x) < uint64(y)
+}
+
+// Round returns the result of rounding d to the nearest multiple of m.
+// The rounding behavior for halfway values is to round away from zero.
+// If the result exceeds the maximum (or minimum)
+// value that can be stored in a Duration,
+// Round returns the maximum (or minimum) duration.
+// If m <= 0, Round returns d unchanged.
+func (d Duration) Round(m Duration) Duration {
+ if m <= 0 {
+ return d
+ }
+ r := d % m
+ if d < 0 {
+ r = -r
+ if lessThanHalf(r, m) {
+ return d + r
+ }
+ if d1 := d - m + r; d1 < d {
+ return d1
+ }
+ return minDuration // overflow
+ }
+ if lessThanHalf(r, m) {
+ return d - r
+ }
+ if d1 := d + m - r; d1 > d {
+ return d1
+ }
+ return maxDuration // overflow
+}
+
+// Add returns the time t+d.
+func (t Time) Add(d Duration) Time {
+ dsec := int64(d / 1e9)
+ nsec := t.nsec() + int32(d%1e9)
+ if nsec >= 1e9 {
+ dsec++
+ nsec -= 1e9
+ } else if nsec < 0 {
+ dsec--
+ nsec += 1e9
+ }
+ t.wall = t.wall&^nsecMask | uint64(nsec) // update nsec
+ t.addSec(dsec)
+ if t.wall&hasMonotonic != 0 {
+ te := t.ext + int64(d)
+ if d < 0 && te > t.ext || d > 0 && te < t.ext {
+ // Monotonic clock reading now out of range; degrade to wall-only.
+ t.stripMono()
+ } else {
+ t.ext = te
+ }
+ }
+ return t
+}
+
+// Sub returns the duration t-u. If the result exceeds the maximum (or minimum)
+// value that can be stored in a Duration, the maximum (or minimum) duration
+// will be returned.
+// To compute t-d for a duration d, use t.Add(-d).
+func (t Time) Sub(u Time) Duration {
+ if t.wall&u.wall&hasMonotonic != 0 {
+ te := t.ext
+ ue := u.ext
+ d := Duration(te - ue)
+ if d < 0 && te > ue {
+ return maxDuration // t - u is positive out of range
+ }
+ if d > 0 && te < ue {
+ return minDuration // t - u is negative out of range
+ }
+ return d
+ }
+ d := Duration(t.sec()-u.sec())*Second + Duration(t.nsec()-u.nsec())
+ // Check for overflow or underflow.
+ switch {
+ case u.Add(d).Equal(t):
+ return d // d is correct
+ case t.Before(u):
+ return minDuration // t - u is negative out of range
+ default:
+ return maxDuration // t - u is positive out of range
+ }
+}
+
+// Since returns the time elapsed since t.
+// It is shorthand for time.Now().Sub(t).
+func Since(t Time) Duration {
+ var now Time
+ if t.wall&hasMonotonic != 0 {
+ // Common case optimization: if t has monotonic time, then Sub will use only it.
+ now = Time{hasMonotonic, runtimeNano() - startNano, nil}
+ } else {
+ now = Now()
+ }
+ return now.Sub(t)
+}
+
+// Until returns the duration until t.
+// It is shorthand for t.Sub(time.Now()).
+func Until(t Time) Duration {
+ var now Time
+ if t.wall&hasMonotonic != 0 {
+ // Common case optimization: if t has monotonic time, then Sub will use only it.
+ now = Time{hasMonotonic, runtimeNano() - startNano, nil}
+ } else {
+ now = Now()
+ }
+ return t.Sub(now)
+}
+
+// AddDate returns the time corresponding to adding the
+// given number of years, months, and days to t.
+// For example, AddDate(-1, 2, 3) applied to January 1, 2011
+// returns March 4, 2010.
+//
+// AddDate normalizes its result in the same way that Date does,
+// so, for example, adding one month to October 31 yields
+// December 1, the normalized form for November 31.
+func (t Time) AddDate(years int, months int, days int) Time {
+ year, month, day := t.Date()
+ hour, min, sec := t.Clock()
+ return Date(year+years, month+Month(months), day+days, hour, min, sec, int(t.nsec()), t.Location())
+}
+
+const (
+ secondsPerMinute = 60
+ secondsPerHour = 60 * secondsPerMinute
+ secondsPerDay = 24 * secondsPerHour
+ secondsPerWeek = 7 * secondsPerDay
+ daysPer400Years = 365*400 + 97
+ daysPer100Years = 365*100 + 24
+ daysPer4Years = 365*4 + 1
+)
+
+// date computes the year, day of year, and when full=true,
+// the month and day in which t occurs.
+func (t Time) date(full bool) (year int, month Month, day int, yday int) {
+ return absDate(t.abs(), full)
+}
+
+// absDate is like date but operates on an absolute time.
+func absDate(abs uint64, full bool) (year int, month Month, day int, yday int) {
+ // Split into time and day.
+ d := abs / secondsPerDay
+
+ // Account for 400 year cycles.
+ n := d / daysPer400Years
+ y := 400 * n
+ d -= daysPer400Years * n
+
+ // Cut off 100-year cycles.
+ // The last cycle has one extra leap year, so on the last day
+ // of that year, day / daysPer100Years will be 4 instead of 3.
+ // Cut it back down to 3 by subtracting n>>2.
+ n = d / daysPer100Years
+ n -= n >> 2
+ y += 100 * n
+ d -= daysPer100Years * n
+
+ // Cut off 4-year cycles.
+ // The last cycle has a missing leap year, which does not
+ // affect the computation.
+ n = d / daysPer4Years
+ y += 4 * n
+ d -= daysPer4Years * n
+
+ // Cut off years within a 4-year cycle.
+ // The last year is a leap year, so on the last day of that year,
+ // day / 365 will be 4 instead of 3. Cut it back down to 3
+ // by subtracting n>>2.
+ n = d / 365
+ n -= n >> 2
+ y += n
+ d -= 365 * n
+
+ year = int(int64(y) + absoluteZeroYear)
+ yday = int(d)
+
+ if !full {
+ return
+ }
+
+ day = yday
+ if isLeap(year) {
+ // Leap year
+ switch {
+ case day > 31+29-1:
+ // After leap day; pretend it wasn't there.
+ day--
+ case day == 31+29-1:
+ // Leap day.
+ month = February
+ day = 29
+ return
+ }
+ }
+
+ // Estimate month on assumption that every month has 31 days.
+ // The estimate may be too low by at most one month, so adjust.
+ month = Month(day / 31)
+ end := int(daysBefore[month+1])
+ var begin int
+ if day >= end {
+ month++
+ begin = end
+ } else {
+ begin = int(daysBefore[month])
+ }
+
+ month++ // because January is 1
+ day = day - begin + 1
+ return
+}
+
+// daysBefore[m] counts the number of days in a non-leap year
+// before month m begins. There is an entry for m=12, counting
+// the number of days before January of next year (365).
+var daysBefore = [...]int32{
+ 0,
+ 31,
+ 31 + 28,
+ 31 + 28 + 31,
+ 31 + 28 + 31 + 30,
+ 31 + 28 + 31 + 30 + 31,
+ 31 + 28 + 31 + 30 + 31 + 30,
+ 31 + 28 + 31 + 30 + 31 + 30 + 31,
+ 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31,
+ 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30,
+ 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31,
+ 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + 30,
+ 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + 30 + 31,
+}
+
+func daysIn(m Month, year int) int {
+ if m == February && isLeap(year) {
+ return 29
+ }
+ return int(daysBefore[m] - daysBefore[m-1])
+}
+
+// daysSinceEpoch takes a year and returns the number of days from
+// the absolute epoch to the start of that year.
+// This is basically (year - zeroYear) * 365, but accounting for leap days.
+func daysSinceEpoch(year int) uint64 {
+ y := uint64(int64(year) - absoluteZeroYear)
+
+ // Add in days from 400-year cycles.
+ n := y / 400
+ y -= 400 * n
+ d := daysPer400Years * n
+
+ // Add in 100-year cycles.
+ n = y / 100
+ y -= 100 * n
+ d += daysPer100Years * n
+
+ // Add in 4-year cycles.
+ n = y / 4
+ y -= 4 * n
+ d += daysPer4Years * n
+
+ // Add in non-leap years.
+ n = y
+ d += 365 * n
+
+ return d
+}
+
+// Provided by package runtime.
+func now() (sec int64, nsec int32, mono int64)
+
+// runtimeNano returns the current value of the runtime clock in nanoseconds.
+//go:linkname runtimeNano runtime.nanotime
+func runtimeNano() int64
+
+// Monotonic times are reported as offsets from startNano.
+// We initialize startNano to runtimeNano() - 1 so that on systems where
+// monotonic time resolution is fairly low (e.g. Windows 2008
+// which appears to have a default resolution of 15ms),
+// we avoid ever reporting a monotonic time of 0.
+// (Callers may want to use 0 as "time not set".)
+var startNano int64 = runtimeNano() - 1
+
+// Now returns the current local time.
+func Now() Time {
+ sec, nsec, mono := now()
+ mono -= startNano
+ sec += unixToInternal - minWall
+ if uint64(sec)>>33 != 0 {
+ return Time{uint64(nsec), sec + minWall, Local}
+ }
+ return Time{hasMonotonic | uint64(sec)<<nsecShift | uint64(nsec), mono, Local}
+}
+
+func unixTime(sec int64, nsec int32) Time {
+ return Time{uint64(nsec), sec + unixToInternal, Local}
+}
+
+// UTC returns t with the location set to UTC.
+func (t Time) UTC() Time {
+ t.setLoc(&utcLoc)
+ return t
+}
+
+// Local returns t with the location set to local time.
+func (t Time) Local() Time {
+ t.setLoc(Local)
+ return t
+}
+
+// In returns a copy of t representing the same time instant, but
+// with the copy's location information set to loc for display
+// purposes.
+//
+// In panics if loc is nil.
+func (t Time) In(loc *Location) Time {
+ if loc == nil {
+ panic("time: missing Location in call to Time.In")
+ }
+ t.setLoc(loc)
+ return t
+}
+
+// Location returns the time zone information associated with t.
+func (t Time) Location() *Location {
+ l := t.loc
+ if l == nil {
+ l = UTC
+ }
+ return l
+}
+
+// Zone computes the time zone in effect at time t, returning the abbreviated
+// name of the zone (such as "CET") and its offset in seconds east of UTC.
+func (t Time) Zone() (name string, offset int) {
+ name, offset, _, _, _ = t.loc.lookup(t.unixSec())
+ return
+}
+
+// Unix returns t as a Unix time, the number of seconds elapsed
+// since January 1, 1970 UTC. The result does not depend on the
+// location associated with t.
+// Unix-like operating systems often record time as a 32-bit
+// count of seconds, but since the method here returns a 64-bit
+// value it is valid for billions of years into the past or future.
+func (t Time) Unix() int64 {
+ return t.unixSec()
+}
+
+// UnixMilli returns t as a Unix time, the number of milliseconds elapsed since
+// January 1, 1970 UTC. The result is undefined if the Unix time in
+// milliseconds cannot be represented by an int64 (a date more than 292 million
+// years before or after 1970). The result does not depend on the
+// location associated with t.
+func (t Time) UnixMilli() int64 {
+ return t.unixSec()*1e3 + int64(t.nsec())/1e6
+}
+
+// UnixMicro returns t as a Unix time, the number of microseconds elapsed since
+// January 1, 1970 UTC. The result is undefined if the Unix time in
+// microseconds cannot be represented by an int64 (a date before year -290307 or
+// after year 294246). The result does not depend on the location associated
+// with t.
+func (t Time) UnixMicro() int64 {
+ return t.unixSec()*1e6 + int64(t.nsec())/1e3
+}
+
+// UnixNano returns t as a Unix time, the number of nanoseconds elapsed
+// since January 1, 1970 UTC. The result is undefined if the Unix time
+// in nanoseconds cannot be represented by an int64 (a date before the year
+// 1678 or after 2262). Note that this means the result of calling UnixNano
+// on the zero Time is undefined. The result does not depend on the
+// location associated with t.
+func (t Time) UnixNano() int64 {
+ return (t.unixSec())*1e9 + int64(t.nsec())
+}
+
+const timeBinaryVersion byte = 1
+
+// MarshalBinary implements the encoding.BinaryMarshaler interface.
+func (t Time) MarshalBinary() ([]byte, error) {
+ var offsetMin int16 // minutes east of UTC. -1 is UTC.
+
+ if t.Location() == UTC {
+ offsetMin = -1
+ } else {
+ _, offset := t.Zone()
+ if offset%60 != 0 {
+ return nil, errors.New("Time.MarshalBinary: zone offset has fractional minute")
+ }
+ offset /= 60
+ if offset < -32768 || offset == -1 || offset > 32767 {
+ return nil, errors.New("Time.MarshalBinary: unexpected zone offset")
+ }
+ offsetMin = int16(offset)
+ }
+
+ sec := t.sec()
+ nsec := t.nsec()
+ enc := []byte{
+ timeBinaryVersion, // byte 0 : version
+ byte(sec >> 56), // bytes 1-8: seconds
+ byte(sec >> 48),
+ byte(sec >> 40),
+ byte(sec >> 32),
+ byte(sec >> 24),
+ byte(sec >> 16),
+ byte(sec >> 8),
+ byte(sec),
+ byte(nsec >> 24), // bytes 9-12: nanoseconds
+ byte(nsec >> 16),
+ byte(nsec >> 8),
+ byte(nsec),
+ byte(offsetMin >> 8), // bytes 13-14: zone offset in minutes
+ byte(offsetMin),
+ }
+
+ return enc, nil
+}
+
+// UnmarshalBinary implements the encoding.BinaryUnmarshaler interface.
+func (t *Time) UnmarshalBinary(data []byte) error {
+ buf := data
+ if len(buf) == 0 {
+ return errors.New("Time.UnmarshalBinary: no data")
+ }
+
+ if buf[0] != timeBinaryVersion {
+ return errors.New("Time.UnmarshalBinary: unsupported version")
+ }
+
+ if len(buf) != /*version*/ 1+ /*sec*/ 8+ /*nsec*/ 4+ /*zone offset*/ 2 {
+ return errors.New("Time.UnmarshalBinary: invalid length")
+ }
+
+ buf = buf[1:]
+ sec := int64(buf[7]) | int64(buf[6])<<8 | int64(buf[5])<<16 | int64(buf[4])<<24 |
+ int64(buf[3])<<32 | int64(buf[2])<<40 | int64(buf[1])<<48 | int64(buf[0])<<56
+
+ buf = buf[8:]
+ nsec := int32(buf[3]) | int32(buf[2])<<8 | int32(buf[1])<<16 | int32(buf[0])<<24
+
+ buf = buf[4:]
+ offset := int(int16(buf[1])|int16(buf[0])<<8) * 60
+
+ *t = Time{}
+ t.wall = uint64(nsec)
+ t.ext = sec
+
+ if offset == -1*60 {
+ t.setLoc(&utcLoc)
+ } else if _, localoff, _, _, _ := Local.lookup(t.unixSec()); offset == localoff {
+ t.setLoc(Local)
+ } else {
+ t.setLoc(FixedZone("", offset))
+ }
+
+ return nil
+}
+
+// TODO(rsc): Remove GobEncoder, GobDecoder, MarshalJSON, UnmarshalJSON in Go 2.
+// The same semantics will be provided by the generic MarshalBinary, MarshalText,
+// UnmarshalBinary, UnmarshalText.
+
+// GobEncode implements the gob.GobEncoder interface.
+func (t Time) GobEncode() ([]byte, error) {
+ return t.MarshalBinary()
+}
+
+// GobDecode implements the gob.GobDecoder interface.
+func (t *Time) GobDecode(data []byte) error {
+ return t.UnmarshalBinary(data)
+}
+
+// MarshalJSON implements the json.Marshaler interface.
+// The time is a quoted string in RFC 3339 format, with sub-second precision added if present.
+func (t Time) MarshalJSON() ([]byte, error) {
+ if y := t.Year(); y < 0 || y >= 10000 {
+ // RFC 3339 is clear that years are 4 digits exactly.
+ // See golang.org/issue/4556#c15 for more discussion.
+ return nil, errors.New("Time.MarshalJSON: year outside of range [0,9999]")
+ }
+
+ b := make([]byte, 0, len(RFC3339Nano)+2)
+ b = append(b, '"')
+ b = t.AppendFormat(b, RFC3339Nano)
+ b = append(b, '"')
+ return b, nil
+}
+
+// UnmarshalJSON implements the json.Unmarshaler interface.
+// The time is expected to be a quoted string in RFC 3339 format.
+func (t *Time) UnmarshalJSON(data []byte) error {
+ // Ignore null, like in the main JSON package.
+ if string(data) == "null" {
+ return nil
+ }
+ // Fractional seconds are handled implicitly by Parse.
+ var err error
+ *t, err = Parse(`"`+RFC3339+`"`, string(data))
+ return err
+}
+
+// MarshalText implements the encoding.TextMarshaler interface.
+// The time is formatted in RFC 3339 format, with sub-second precision added if present.
+func (t Time) MarshalText() ([]byte, error) {
+ if y := t.Year(); y < 0 || y >= 10000 {
+ return nil, errors.New("Time.MarshalText: year outside of range [0,9999]")
+ }
+
+ b := make([]byte, 0, len(RFC3339Nano))
+ return t.AppendFormat(b, RFC3339Nano), nil
+}
+
+// UnmarshalText implements the encoding.TextUnmarshaler interface.
+// The time is expected to be in RFC 3339 format.
+func (t *Time) UnmarshalText(data []byte) error {
+ // Fractional seconds are handled implicitly by Parse.
+ var err error
+ *t, err = Parse(RFC3339, string(data))
+ return err
+}
+
+// Unix returns the local Time corresponding to the given Unix time,
+// sec seconds and nsec nanoseconds since January 1, 1970 UTC.
+// It is valid to pass nsec outside the range [0, 999999999].
+// Not all sec values have a corresponding time value. One such
+// value is 1<<63-1 (the largest int64 value).
+func Unix(sec int64, nsec int64) Time {
+ if nsec < 0 || nsec >= 1e9 {
+ n := nsec / 1e9
+ sec += n
+ nsec -= n * 1e9
+ if nsec < 0 {
+ nsec += 1e9
+ sec--
+ }
+ }
+ return unixTime(sec, int32(nsec))
+}
+
+// UnixMilli returns the local Time corresponding to the given Unix time,
+// msec milliseconds since January 1, 1970 UTC.
+func UnixMilli(msec int64) Time {
+ return Unix(msec/1e3, (msec%1e3)*1e6)
+}
+
+// UnixMicro returns the local Time corresponding to the given Unix time,
+// usec microseconds since January 1, 1970 UTC.
+func UnixMicro(usec int64) Time {
+ return Unix(usec/1e6, (usec%1e6)*1e3)
+}
+
+// IsDST reports whether the time in the configured location is in Daylight Savings Time.
+func (t Time) IsDST() bool {
+ _, _, _, _, isDST := t.loc.lookup(t.Unix())
+ return isDST
+}
+
+func isLeap(year int) bool {
+ return year%4 == 0 && (year%100 != 0 || year%400 == 0)
+}
+
+// norm returns nhi, nlo such that
+// hi * base + lo == nhi * base + nlo
+// 0 <= nlo < base
+func norm(hi, lo, base int) (nhi, nlo int) {
+ if lo < 0 {
+ n := (-lo-1)/base + 1
+ hi -= n
+ lo += n * base
+ }
+ if lo >= base {
+ n := lo / base
+ hi += n
+ lo -= n * base
+ }
+ return hi, lo
+}
+
+// Date returns the Time corresponding to
+// yyyy-mm-dd hh:mm:ss + nsec nanoseconds
+// in the appropriate zone for that time in the given location.
+//
+// The month, day, hour, min, sec, and nsec values may be outside
+// their usual ranges and will be normalized during the conversion.
+// For example, October 32 converts to November 1.
+//
+// A daylight savings time transition skips or repeats times.
+// For example, in the United States, March 13, 2011 2:15am never occurred,
+// while November 6, 2011 1:15am occurred twice. In such cases, the
+// choice of time zone, and therefore the time, is not well-defined.
+// Date returns a time that is correct in one of the two zones involved
+// in the transition, but it does not guarantee which.
+//
+// Date panics if loc is nil.
+func Date(year int, month Month, day, hour, min, sec, nsec int, loc *Location) Time {
+ if loc == nil {
+ panic("time: missing Location in call to Date")
+ }
+
+ // Normalize month, overflowing into year.
+ m := int(month) - 1
+ year, m = norm(year, m, 12)
+ month = Month(m) + 1
+
+ // Normalize nsec, sec, min, hour, overflowing into day.
+ sec, nsec = norm(sec, nsec, 1e9)
+ min, sec = norm(min, sec, 60)
+ hour, min = norm(hour, min, 60)
+ day, hour = norm(day, hour, 24)
+
+ // Compute days since the absolute epoch.
+ d := daysSinceEpoch(year)
+
+ // Add in days before this month.
+ d += uint64(daysBefore[month-1])
+ if isLeap(year) && month >= March {
+ d++ // February 29
+ }
+
+ // Add in days before today.
+ d += uint64(day - 1)
+
+ // Add in time elapsed today.
+ abs := d * secondsPerDay
+ abs += uint64(hour*secondsPerHour + min*secondsPerMinute + sec)
+
+ unix := int64(abs) + (absoluteToInternal + internalToUnix)
+
+ // Look for zone offset for expected time, so we can adjust to UTC.
+ // The lookup function expects UTC, so first we pass unix in the
+ // hope that it will not be too close to a zone transition,
+ // and then adjust if it is.
+ _, offset, start, end, _ := loc.lookup(unix)
+ if offset != 0 {
+ utc := unix - int64(offset)
+ // If utc is valid for the time zone we found, then we have the right offset.
+ // If not, we get the correct offset by looking up utc in the location.
+ if utc < start || utc >= end {
+ _, offset, _, _, _ = loc.lookup(utc)
+ }
+ unix -= int64(offset)
+ }
+
+ t := unixTime(unix, int32(nsec))
+ t.setLoc(loc)
+ return t
+}
+
+// Truncate returns the result of rounding t down to a multiple of d (since the zero time).
+// If d <= 0, Truncate returns t stripped of any monotonic clock reading but otherwise unchanged.
+//
+// Truncate operates on the time as an absolute duration since the
+// zero time; it does not operate on the presentation form of the
+// time. Thus, Truncate(Hour) may return a time with a non-zero
+// minute, depending on the time's Location.
+func (t Time) Truncate(d Duration) Time {
+ t.stripMono()
+ if d <= 0 {
+ return t
+ }
+ _, r := div(t, d)
+ return t.Add(-r)
+}
+
+// Round returns the result of rounding t to the nearest multiple of d (since the zero time).
+// The rounding behavior for halfway values is to round up.
+// If d <= 0, Round returns t stripped of any monotonic clock reading but otherwise unchanged.
+//
+// Round operates on the time as an absolute duration since the
+// zero time; it does not operate on the presentation form of the
+// time. Thus, Round(Hour) may return a time with a non-zero
+// minute, depending on the time's Location.
+func (t Time) Round(d Duration) Time {
+ t.stripMono()
+ if d <= 0 {
+ return t
+ }
+ _, r := div(t, d)
+ if lessThanHalf(r, d) {
+ return t.Add(-r)
+ }
+ return t.Add(d - r)
+}
+
+// div divides t by d and returns the quotient parity and remainder.
+// We don't use the quotient parity anymore (round half up instead of round to even)
+// but it's still here in case we change our minds.
+func div(t Time, d Duration) (qmod2 int, r Duration) {
+ neg := false
+ nsec := t.nsec()
+ sec := t.sec()
+ if sec < 0 {
+ // Operate on absolute value.
+ neg = true
+ sec = -sec
+ nsec = -nsec
+ if nsec < 0 {
+ nsec += 1e9
+ sec-- // sec >= 1 before the -- so safe
+ }
+ }
+
+ switch {
+ // Special case: 2d divides 1 second.
+ case d < Second && Second%(d+d) == 0:
+ qmod2 = int(nsec/int32(d)) & 1
+ r = Duration(nsec % int32(d))
+
+ // Special case: d is a multiple of 1 second.
+ case d%Second == 0:
+ d1 := int64(d / Second)
+ qmod2 = int(sec/d1) & 1
+ r = Duration(sec%d1)*Second + Duration(nsec)
+
+ // General case.
+ // This could be faster if more cleverness were applied,
+ // but it's really only here to avoid special case restrictions in the API.
+ // No one will care about these cases.
+ default:
+ // Compute nanoseconds as 128-bit number.
+ sec := uint64(sec)
+ tmp := (sec >> 32) * 1e9
+ u1 := tmp >> 32
+ u0 := tmp << 32
+ tmp = (sec & 0xFFFFFFFF) * 1e9
+ u0x, u0 := u0, u0+tmp
+ if u0 < u0x {
+ u1++
+ }
+ u0x, u0 = u0, u0+uint64(nsec)
+ if u0 < u0x {
+ u1++
+ }
+
+ // Compute remainder by subtracting r<<k for decreasing k.
+ // Quotient parity is whether we subtract on last round.
+ d1 := uint64(d)
+ for d1>>63 != 1 {
+ d1 <<= 1
+ }
+ d0 := uint64(0)
+ for {
+ qmod2 = 0
+ if u1 > d1 || u1 == d1 && u0 >= d0 {
+ // subtract
+ qmod2 = 1
+ u0x, u0 = u0, u0-d0
+ if u0 > u0x {
+ u1--
+ }
+ u1 -= d1
+ }
+ if d1 == 0 && d0 == uint64(d) {
+ break
+ }
+ d0 >>= 1
+ d0 |= (d1 & 1) << 63
+ d1 >>= 1
+ }
+ r = Duration(u0)
+ }
+
+ if neg && r != 0 {
+ // If input was negative and not an exact multiple of d, we computed q, r such that
+ // q*d + r = -t
+ // But the right answers are given by -(q-1), d-r:
+ // q*d + r = -t
+ // -q*d - r = t
+ // -(q-1)*d + (d - r) = t
+ qmod2 ^= 1
+ r = d - r
+ }
+ return
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-15 01:17:06 +0000