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Diffstat (limited to 'src/pkg/time/zoneinfo_unix.go')
-rw-r--r-- | src/pkg/time/zoneinfo_unix.go | 213 |
1 files changed, 213 insertions, 0 deletions
diff --git a/src/pkg/time/zoneinfo_unix.go b/src/pkg/time/zoneinfo_unix.go new file mode 100644 index 000000000..f3ea7b6fd --- /dev/null +++ b/src/pkg/time/zoneinfo_unix.go @@ -0,0 +1,213 @@ +// 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 +) + +// 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) +} + +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) +} + +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. + // Many systems use /usr/share/zoneinfo, Solaris 2 has + // /usr/share/lib/zoneinfo, IRIX 6 has /usr/lib/locale/TZ. + zoneDirs := []string{"/usr/share/zoneinfo/", + "/usr/share/lib/zoneinfo/", + "/usr/lib/locale/TZ/"} + + tz, err := os.Getenverror("TZ") + switch { + case err == os.ENOENV: + zones, _ = readinfofile("/etc/localtime") + case len(tz) > 0: + for _, zoneDir := range zoneDirs { + var ok bool + if zones, ok = readinfofile(zoneDir + tz); ok { + break + } + } + case len(tz) == 0: + // do nothing: use UTC + } +} |