+++ /dev/null
-// 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.
-
-// Parse "zoneinfo" time zone file.
-// This is a fairly standard file format used on OS X, Linux, BSD, Sun, and others.
-// See tzfile(5), http://en.wikipedia.org/wiki/Zoneinfo,
-// and ftp://munnari.oz.au/pub/oldtz/
-
-package time
-
-import (
- "io/ioutil"
- "os"
-)
-
-const (
- headerSize = 4 + 16 + 4*7
- zoneDir = "/usr/share/zoneinfo/"
-)
-
-// Simple I/O interface to binary blob of data.
-type data struct {
- p []byte
- error bool
-}
-
-
-func (d *data) read(n int) []byte {
- if len(d.p) < n {
- d.p = nil
- d.error = true
- return nil
- }
- p := d.p[0:n]
- d.p = d.p[n:]
- return p
-}
-
-func (d *data) big4() (n uint32, ok bool) {
- p := d.read(4)
- if len(p) < 4 {
- d.error = true
- return 0, false
- }
- return uint32(p[0])<<24 | uint32(p[1])<<16 | uint32(p[2])<<8 | uint32(p[3]), true
-}
-
-func (d *data) byte() (n byte, ok bool) {
- p := d.read(1)
- if len(p) < 1 {
- d.error = true
- return 0, false
- }
- return p[0], true
-}
-
-
-// Make a string by stopping at the first NUL
-func byteString(p []byte) string {
- for i := 0; i < len(p); i++ {
- if p[i] == 0 {
- return string(p[0:i])
- }
- }
- return string(p)
-}
-
-// Parsed representation
-type zone struct {
- utcoff int
- isdst bool
- name string
-}
-
-type zonetime struct {
- time int32 // transition time, in seconds since 1970 GMT
- zone *zone // the zone that goes into effect at that time
- isstd, isutc bool // ignored - no idea what these mean
-}
-
-func parseinfo(bytes []byte) (zt []zonetime, ok bool) {
- d := data{bytes, false}
-
- // 4-byte magic "TZif"
- if magic := d.read(4); string(magic) != "TZif" {
- return nil, false
- }
-
- // 1-byte version, then 15 bytes of padding
- var p []byte
- if p = d.read(16); len(p) != 16 || p[0] != 0 && p[0] != '2' {
- return nil, false
- }
-
- // six big-endian 32-bit integers:
- // number of UTC/local indicators
- // number of standard/wall indicators
- // number of leap seconds
- // number of transition times
- // number of local time zones
- // number of characters of time zone abbrev strings
- const (
- NUTCLocal = iota
- NStdWall
- NLeap
- NTime
- NZone
- NChar
- )
- var n [6]int
- for i := 0; i < 6; i++ {
- nn, ok := d.big4()
- if !ok {
- return nil, false
- }
- n[i] = int(nn)
- }
-
- // Transition times.
- txtimes := data{d.read(n[NTime] * 4), false}
-
- // Time zone indices for transition times.
- txzones := d.read(n[NTime])
-
- // Zone info structures
- zonedata := data{d.read(n[NZone] * 6), false}
-
- // Time zone abbreviations.
- abbrev := d.read(n[NChar])
-
- // Leap-second time pairs
- d.read(n[NLeap] * 8)
-
- // Whether tx times associated with local time types
- // are specified as standard time or wall time.
- isstd := d.read(n[NStdWall])
-
- // Whether tx times associated with local time types
- // are specified as UTC or local time.
- isutc := d.read(n[NUTCLocal])
-
- if d.error { // ran out of data
- return nil, false
- }
-
- // If version == 2, the entire file repeats, this time using
- // 8-byte ints for txtimes and leap seconds.
- // We won't need those until 2106.
-
- // Now we can build up a useful data structure.
- // First the zone information.
- // utcoff[4] isdst[1] nameindex[1]
- z := make([]zone, n[NZone])
- for i := 0; i < len(z); i++ {
- var ok bool
- var n uint32
- if n, ok = zonedata.big4(); !ok {
- return nil, false
- }
- z[i].utcoff = int(n)
- var b byte
- if b, ok = zonedata.byte(); !ok {
- return nil, false
- }
- z[i].isdst = b != 0
- if b, ok = zonedata.byte(); !ok || int(b) >= len(abbrev) {
- return nil, false
- }
- z[i].name = byteString(abbrev[b:])
- }
-
- // Now the transition time info.
- zt = make([]zonetime, n[NTime])
- for i := 0; i < len(zt); i++ {
- var ok bool
- var n uint32
- if n, ok = txtimes.big4(); !ok {
- return nil, false
- }
- zt[i].time = int32(n)
- if int(txzones[i]) >= len(z) {
- return nil, false
- }
- zt[i].zone = &z[txzones[i]]
- if i < len(isstd) {
- zt[i].isstd = isstd[i] != 0
- }
- if i < len(isutc) {
- zt[i].isutc = isutc[i] != 0
- }
- }
- return zt, true
-}
-
-func readinfofile(name string) ([]zonetime, bool) {
- buf, err := ioutil.ReadFile(name)
- if err != nil {
- return nil, false
- }
- return parseinfo(buf)
-}
-
-var zones []zonetime
-var onceSetupZone sync.Once
-
-func setupZone() {
- // consult $TZ to find the time zone to use.
- // no $TZ means use the system default /etc/localtime.
- // $TZ="" means use UTC.
- // $TZ="foo" means use /usr/share/zoneinfo/foo.
-
- tz, err := os.Getenverror("TZ")
- switch {
- case err == os.ENOENV:
- zones, _ = readinfofile("/etc/localtime")
- case len(tz) > 0:
- zones, _ = readinfofile(zoneDir + tz)
- case len(tz) == 0:
- // do nothing: use UTC
- }
-}
-
-// Look up the correct time zone (daylight savings or not) for the given unix time, in the current location.
-func lookupTimezone(sec int64) (zone string, offset int) {
- onceSetupZone.Do(setupZone)
- if len(zones) == 0 {
- return "UTC", 0
- }
-
- // Binary search for entry with largest time <= sec
- tz := zones
- for len(tz) > 1 {
- m := len(tz) / 2
- if sec < int64(tz[m].time) {
- tz = tz[0:m]
- } else {
- tz = tz[m:]
- }
- }
- z := tz[0].zone
- return z.name, z.utcoff
-}