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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
import (
"errors"
"runtime"
"syscall"
)
// TODO(rsc): Fall back to copy of zoneinfo files.
// BUG(brainman,rsc): On Windows, the operating system does not provide complete
// time zone information.
// The implementation assumes that this year's rules for daylight savings
// time apply to all previous and future years as well.
// Also, time zone abbreviations are unavailable. The implementation constructs
// them using the capital letters from a longer time zone description.
// abbrev returns the abbreviation to use for the given zone name.
func abbrev(name []uint16) string {
// name is 'Pacific Standard Time' but we want 'PST'.
// Extract just capital letters. It's not perfect but the
// information we need is not available from the kernel.
// Because time zone abbreviations are not unique,
// Windows refuses to expose them.
//
// http://social.msdn.microsoft.com/Forums/eu/vclanguage/thread/a87e1d25-fb71-4fe0-ae9c-a9578c9753eb
// http://stackoverflow.com/questions/4195948/windows-time-zone-abbreviations-in-asp-net
var short []rune
for _, c := range name {
if 'A' <= c && c <= 'Z' {
short = append(short, rune(c))
}
}
return string(short)
}
// pseudoUnix returns the pseudo-Unix time (seconds since Jan 1 1970 *LOCAL TIME*)
// denoted by the system date+time d in the given year.
// It is up to the caller to convert this local time into a UTC-based time.
func pseudoUnix(year int, d *syscall.Systemtime) int64 {
// Windows specifies daylight savings information in "day in month" format:
// d.Month is month number (1-12)
// d.DayOfWeek is appropriate weekday (Sunday=0 to Saturday=6)
// d.Day is week within the month (1 to 5, where 5 is last week of the month)
// d.Hour, d.Minute and d.Second are absolute time
day := 1
t := Date(year, Month(d.Month), day, int(d.Hour), int(d.Minute), int(d.Second), 0, UTC)
i := int(d.DayOfWeek) - int(t.Weekday())
if i < 0 {
i += 7
}
day += i
if week := int(d.Day) - 1; week < 4 {
day += week * 7
} else {
// "Last" instance of the day.
day += 4 * 7
if day > daysIn(Month(d.Month), year) {
day -= 7
}
}
return t.sec + int64(day-1)*secondsPerDay + internalToUnix
}
func initLocalFromTZI(i *syscall.Timezoneinformation) {
l := &localLoc
nzone := 1
if i.StandardDate.Month > 0 {
nzone++
}
l.zone = make([]zone, nzone)
std := &l.zone[0]
std.name = abbrev(i.StandardName[0:])
if nzone == 1 {
// No daylight savings.
std.offset = -int(i.Bias) * 60
l.cacheStart = -1 << 63
l.cacheEnd = 1<<63 - 1
l.cacheZone = std
l.tx = make([]zoneTrans, 1)
l.tx[0].when = l.cacheStart
l.tx[0].index = 0
return
}
// StandardBias must be ignored if StandardDate is not set,
// so this computation is delayed until after the nzone==1
// return above.
std.offset = -int(i.Bias+i.StandardBias) * 60
dst := &l.zone[1]
dst.name = abbrev(i.DaylightName[0:])
dst.offset = -int(i.Bias+i.DaylightBias) * 60
dst.isDST = true
// Arrange so that d0 is first transition date, d1 second,
// i0 is index of zone after first transition, i1 second.
d0 := &i.StandardDate
d1 := &i.DaylightDate
i0 := 0
i1 := 1
if d0.Month > d1.Month {
d0, d1 = d1, d0
i0, i1 = i1, i0
}
// 2 tx per year, 100 years on each side of this year
l.tx = make([]zoneTrans, 400)
t := Now().UTC()
year := t.Year()
txi := 0
for y := year - 100; y < year+100; y++ {
tx := &l.tx[txi]
tx.when = pseudoUnix(y, d0) - int64(l.zone[i1].offset)
tx.index = uint8(i0)
txi++
tx = &l.tx[txi]
tx.when = pseudoUnix(y, d1) - int64(l.zone[i0].offset)
tx.index = uint8(i1)
txi++
}
}
var usPacific = syscall.Timezoneinformation{
Bias: 8 * 60,
StandardName: [32]uint16{
'P', 'a', 'c', 'i', 'f', 'i', 'c', ' ', 'S', 't', 'a', 'n', 'd', 'a', 'r', 'd', ' ', 'T', 'i', 'm', 'e',
},
StandardDate: syscall.Systemtime{Month: 11, Day: 1, Hour: 2},
DaylightName: [32]uint16{
'P', 'a', 'c', 'i', 'f', 'i', 'c', ' ', 'D', 'a', 'y', 'l', 'i', 'g', 'h', 't', ' ', 'T', 'i', 'm', 'e',
},
DaylightDate: syscall.Systemtime{Month: 3, Day: 2, Hour: 2},
DaylightBias: -60,
}
func initTestingZone() {
initLocalFromTZI(&usPacific)
}
func initLocal() {
var i syscall.Timezoneinformation
if _, err := syscall.GetTimeZoneInformation(&i); err != nil {
localLoc.name = "UTC"
return
}
initLocalFromTZI(&i)
}
func loadLocation(name string) (*Location, error) {
if z, err := loadZoneFile(runtime.GOROOT()+`\lib\time\zoneinfo.zip`, name); err == nil {
z.name = name
return z, nil
}
return nil, errors.New("unknown time zone " + name)
}
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