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Diffstat (limited to 'src/pkg/time/zoneinfo.go')
| -rw-r--r-- | src/pkg/time/zoneinfo.go | 287 |
1 files changed, 0 insertions, 287 deletions
diff --git a/src/pkg/time/zoneinfo.go b/src/pkg/time/zoneinfo.go deleted file mode 100644 index c8e53a27c..000000000 --- a/src/pkg/time/zoneinfo.go +++ /dev/null @@ -1,287 +0,0 @@ -// Copyright 2011 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 ( - "sync" - "syscall" -) - -// A Location maps time instants to the zone in use at that time. -// Typically, the Location represents the collection of time offsets -// in use in a geographical area, such as CEST and CET for central Europe. -type Location struct { - name string - zone []zone - tx []zoneTrans - - // Most lookups will be for the current time. - // To avoid the binary search through tx, keep a - // static one-element cache that gives the correct - // zone for the time when the Location was created. - // if cacheStart <= t <= cacheEnd, - // lookup can return cacheZone. - // The units for cacheStart and cacheEnd are seconds - // since January 1, 1970 UTC, to match the argument - // to lookup. - cacheStart int64 - cacheEnd int64 - cacheZone *zone -} - -// A zone represents a single time zone such as CEST or CET. -type zone struct { - name string // abbreviated name, "CET" - offset int // seconds east of UTC - isDST bool // is this zone Daylight Savings Time? -} - -// A zoneTrans represents a single time zone transition. -type zoneTrans struct { - when int64 // transition time, in seconds since 1970 GMT - index uint8 // the index of the zone that goes into effect at that time - isstd, isutc bool // ignored - no idea what these mean -} - -// alpha and omega are the beginning and end of time for zone -// transitions. -const ( - alpha = -1 << 63 // math.MinInt64 - omega = 1<<63 - 1 // math.MaxInt64 -) - -// UTC represents Universal Coordinated Time (UTC). -var UTC *Location = &utcLoc - -// utcLoc is separate so that get can refer to &utcLoc -// and ensure that it never returns a nil *Location, -// even if a badly behaved client has changed UTC. -var utcLoc = Location{name: "UTC"} - -// Local represents the system's local time zone. -var Local *Location = &localLoc - -// localLoc is separate so that initLocal can initialize -// it even if a client has changed Local. -var localLoc Location -var localOnce sync.Once - -func (l *Location) get() *Location { - if l == nil { - return &utcLoc - } - if l == &localLoc { - localOnce.Do(initLocal) - } - return l -} - -// String returns a descriptive name for the time zone information, -// corresponding to the argument to LoadLocation. -func (l *Location) String() string { - return l.get().name -} - -// FixedZone returns a Location that always uses -// the given zone name and offset (seconds east of UTC). -func FixedZone(name string, offset int) *Location { - l := &Location{ - name: name, - zone: []zone{{name, offset, false}}, - tx: []zoneTrans{{alpha, 0, false, false}}, - cacheStart: alpha, - cacheEnd: omega, - } - l.cacheZone = &l.zone[0] - return l -} - -// lookup returns information about the time zone in use at an -// instant in time expressed as seconds since January 1, 1970 00:00:00 UTC. -// -// The returned information gives the name of the zone (such as "CET"), -// the start and end times bracketing sec when that zone is in effect, -// the offset in seconds east of UTC (such as -5*60*60), and whether -// the daylight savings is being observed at that time. -func (l *Location) lookup(sec int64) (name string, offset int, isDST bool, start, end int64) { - l = l.get() - - if len(l.zone) == 0 { - name = "UTC" - offset = 0 - isDST = false - start = alpha - end = omega - return - } - - if zone := l.cacheZone; zone != nil && l.cacheStart <= sec && sec < l.cacheEnd { - name = zone.name - offset = zone.offset - isDST = zone.isDST - start = l.cacheStart - end = l.cacheEnd - return - } - - if len(l.tx) == 0 || sec < l.tx[0].when { - zone := &l.zone[l.lookupFirstZone()] - name = zone.name - offset = zone.offset - isDST = zone.isDST - start = alpha - if len(l.tx) > 0 { - end = l.tx[0].when - } else { - end = omega - } - return - } - - // Binary search for entry with largest time <= sec. - // Not using sort.Search to avoid dependencies. - tx := l.tx - end = omega - lo := 0 - hi := len(tx) - for hi-lo > 1 { - m := lo + (hi-lo)/2 - lim := tx[m].when - if sec < lim { - end = lim - hi = m - } else { - lo = m - } - } - zone := &l.zone[tx[lo].index] - name = zone.name - offset = zone.offset - isDST = zone.isDST - start = tx[lo].when - // end = maintained during the search - return -} - -// lookupFirstZone returns the index of the time zone to use for times -// before the first transition time, or when there are no transition -// times. -// -// The reference implementation in localtime.c from -// http://www.iana.org/time-zones/repository/releases/tzcode2013g.tar.gz -// implements the following algorithm for these cases: -// 1) If the first zone is unused by the transitions, use it. -// 2) Otherwise, if there are transition times, and the first -// transition is to a zone in daylight time, find the first -// non-daylight-time zone before and closest to the first transition -// zone. -// 3) Otherwise, use the first zone that is not daylight time, if -// there is one. -// 4) Otherwise, use the first zone. -func (l *Location) lookupFirstZone() int { - // Case 1. - if !l.firstZoneUsed() { - return 0 - } - - // Case 2. - if len(l.tx) > 0 && l.zone[l.tx[0].index].isDST { - for zi := int(l.tx[0].index) - 1; zi >= 0; zi-- { - if !l.zone[zi].isDST { - return zi - } - } - } - - // Case 3. - for zi := range l.zone { - if !l.zone[zi].isDST { - return zi - } - } - - // Case 4. - return 0 -} - -// firstZoneUsed returns whether the first zone is used by some -// transition. -func (l *Location) firstZoneUsed() bool { - for _, tx := range l.tx { - if tx.index == 0 { - return true - } - } - return false -} - -// lookupName returns information about the time zone with -// the given name (such as "EST") at the given pseudo-Unix time -// (what the given time of day would be in UTC). -func (l *Location) lookupName(name string, unix int64) (offset int, isDST bool, ok bool) { - l = l.get() - - // First try for a zone with the right name that was actually - // in effect at the given time. (In Sydney, Australia, both standard - // and daylight-savings time are abbreviated "EST". Using the - // offset helps us pick the right one for the given time. - // It's not perfect: during the backward transition we might pick - // either one.) - for i := range l.zone { - zone := &l.zone[i] - if zone.name == name { - nam, offset, isDST, _, _ := l.lookup(unix - int64(zone.offset)) - if nam == zone.name { - return offset, isDST, true - } - } - } - - // Otherwise fall back to an ordinary name match. - for i := range l.zone { - zone := &l.zone[i] - if zone.name == name { - return zone.offset, zone.isDST, true - } - } - - // Otherwise, give up. - return -} - -// NOTE(rsc): Eventually we will need to accept the POSIX TZ environment -// syntax too, but I don't feel like implementing it today. - -var zoneinfo, _ = syscall.Getenv("ZONEINFO") - -// LoadLocation returns the Location with the given name. -// -// If the name is "" or "UTC", LoadLocation returns UTC. -// If the name is "Local", LoadLocation returns Local. -// -// Otherwise, the name is taken to be a location name corresponding to a file -// in the IANA Time Zone database, such as "America/New_York". -// -// The time zone database needed by LoadLocation may not be -// present on all systems, especially non-Unix systems. -// LoadLocation looks in the directory or uncompressed zip file -// named by the ZONEINFO environment variable, if any, then looks in -// known installation locations on Unix systems, -// and finally looks in $GOROOT/lib/time/zoneinfo.zip. -func LoadLocation(name string) (*Location, error) { - if name == "" || name == "UTC" { - return UTC, nil - } - if name == "Local" { - return Local, nil - } - if zoneinfo != "" { - if z, err := loadZoneFile(zoneinfo, name); err == nil { - z.name = name - return z, nil - } - } - return loadLocation(name) -} |