524 lines
12 KiB
Go
524 lines
12 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Parse "zoneinfo" time zone file.
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// This is a fairly standard file format used on OS X, Linux, BSD, Sun, and others.
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// See tzfile(5), https://en.wikipedia.org/wiki/Zoneinfo,
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// and ftp://munnari.oz.au/pub/oldtz/
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package time
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import (
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"errors"
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"runtime"
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"syscall"
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)
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// maxFileSize is the max permitted size of files read by readFile.
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// As reference, the zoneinfo.zip distributed by Go is ~350 KB,
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// so 10MB is overkill.
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const maxFileSize = 10 << 20
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type fileSizeError string
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func (f fileSizeError) Error() string {
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return "time: file " + string(f) + " is too large"
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}
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// Copies of io.Seek* constants to avoid importing "io":
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const (
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seekStart = 0
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seekCurrent = 1
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seekEnd = 2
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)
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// Simple I/O interface to binary blob of data.
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type dataIO struct {
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p []byte
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error bool
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}
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func (d *dataIO) read(n int) []byte {
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if len(d.p) < n {
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d.p = nil
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d.error = true
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return nil
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}
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p := d.p[0:n]
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d.p = d.p[n:]
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return p
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}
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func (d *dataIO) big4() (n uint32, ok bool) {
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p := d.read(4)
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if len(p) < 4 {
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d.error = true
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return 0, false
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}
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return uint32(p[3]) | uint32(p[2])<<8 | uint32(p[1])<<16 | uint32(p[0])<<24, true
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}
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func (d *dataIO) big8() (n uint64, ok bool) {
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n1, ok1 := d.big4()
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n2, ok2 := d.big4()
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if !ok1 || !ok2 {
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d.error = true
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return 0, false
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}
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return (uint64(n1) << 32) | uint64(n2), true
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}
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func (d *dataIO) byte() (n byte, ok bool) {
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p := d.read(1)
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if len(p) < 1 {
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d.error = true
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return 0, false
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}
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return p[0], true
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}
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// Make a string by stopping at the first NUL
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func byteString(p []byte) string {
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for i := 0; i < len(p); i++ {
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if p[i] == 0 {
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return string(p[0:i])
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}
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}
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return string(p)
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}
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var badData = errors.New("malformed time zone information")
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// LoadLocationFromTZData returns a Location with the given name
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// initialized from the IANA Time Zone database-formatted data.
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// The data should be in the format of a standard IANA time zone file
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// (for example, the content of /etc/localtime on Unix systems).
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func LoadLocationFromTZData(name string, data []byte) (*Location, error) {
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d := dataIO{data, false}
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// 4-byte magic "TZif"
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if magic := d.read(4); string(magic) != "TZif" {
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return nil, badData
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}
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// 1-byte version, then 15 bytes of padding
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var version int
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var p []byte
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if p = d.read(16); len(p) != 16 {
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return nil, badData
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} else {
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switch p[0] {
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case 0:
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version = 1
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case '2':
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version = 2
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case '3':
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version = 3
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default:
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return nil, badData
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}
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}
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// six big-endian 32-bit integers:
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// number of UTC/local indicators
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// number of standard/wall indicators
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// number of leap seconds
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// number of transition times
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// number of local time zones
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// number of characters of time zone abbrev strings
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const (
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NUTCLocal = iota
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NStdWall
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NLeap
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NTime
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NZone
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NChar
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)
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var n [6]int
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for i := 0; i < 6; i++ {
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nn, ok := d.big4()
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if !ok {
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return nil, badData
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}
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if uint32(int(nn)) != nn {
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return nil, badData
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}
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n[i] = int(nn)
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}
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// If we have version 2 or 3, then the data is first written out
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// in a 32-bit format, then written out again in a 64-bit format.
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// Skip the 32-bit format and read the 64-bit one, as it can
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// describe a broader range of dates.
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is64 := false
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if version > 1 {
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// Skip the 32-bit data.
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skip := n[NTime]*4 +
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n[NTime] +
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n[NZone]*6 +
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n[NChar] +
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n[NLeap]*8 +
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n[NStdWall] +
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n[NUTCLocal]
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// Skip the version 2 header that we just read.
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skip += 4 + 16
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d.read(skip)
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is64 = true
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// Read the counts again, they can differ.
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for i := 0; i < 6; i++ {
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nn, ok := d.big4()
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if !ok {
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return nil, badData
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}
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if uint32(int(nn)) != nn {
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return nil, badData
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}
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n[i] = int(nn)
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}
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}
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size := 4
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if is64 {
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size = 8
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}
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// Transition times.
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txtimes := dataIO{d.read(n[NTime] * size), false}
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// Time zone indices for transition times.
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txzones := d.read(n[NTime])
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// Zone info structures
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zonedata := dataIO{d.read(n[NZone] * 6), false}
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// Time zone abbreviations.
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abbrev := d.read(n[NChar])
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// Leap-second time pairs
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d.read(n[NLeap] * (size + 4))
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// Whether tx times associated with local time types
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// are specified as standard time or wall time.
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isstd := d.read(n[NStdWall])
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// Whether tx times associated with local time types
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// are specified as UTC or local time.
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isutc := d.read(n[NUTCLocal])
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if d.error { // ran out of data
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return nil, badData
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}
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// Now we can build up a useful data structure.
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// First the zone information.
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// utcoff[4] isdst[1] nameindex[1]
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nzone := n[NZone]
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if nzone == 0 {
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// Reject tzdata files with no zones. There's nothing useful in them.
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// This also avoids a panic later when we add and then use a fake transition (golang.org/issue/29437).
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return nil, badData
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}
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zone := make([]zone, nzone)
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for i := range zone {
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var ok bool
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var n uint32
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if n, ok = zonedata.big4(); !ok {
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return nil, badData
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}
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if uint32(int(n)) != n {
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return nil, badData
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}
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zone[i].offset = int(int32(n))
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var b byte
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if b, ok = zonedata.byte(); !ok {
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return nil, badData
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}
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zone[i].isDST = b != 0
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if b, ok = zonedata.byte(); !ok || int(b) >= len(abbrev) {
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return nil, badData
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}
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zone[i].name = byteString(abbrev[b:])
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if runtime.GOOS == "aix" && len(name) > 8 && (name[:8] == "Etc/GMT+" || name[:8] == "Etc/GMT-") {
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// There is a bug with AIX 7.2 TL 0 with files in Etc,
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// GMT+1 will return GMT-1 instead of GMT+1 or -01.
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if name != "Etc/GMT+0" {
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// GMT+0 is OK
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zone[i].name = name[4:]
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}
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}
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}
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// Now the transition time info.
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tx := make([]zoneTrans, n[NTime])
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for i := range tx {
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var n int64
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if !is64 {
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if n4, ok := txtimes.big4(); !ok {
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return nil, badData
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} else {
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n = int64(int32(n4))
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}
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} else {
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if n8, ok := txtimes.big8(); !ok {
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return nil, badData
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} else {
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n = int64(n8)
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}
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}
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tx[i].when = n
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if int(txzones[i]) >= len(zone) {
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return nil, badData
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}
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tx[i].index = txzones[i]
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if i < len(isstd) {
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tx[i].isstd = isstd[i] != 0
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}
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if i < len(isutc) {
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tx[i].isutc = isutc[i] != 0
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}
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}
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if len(tx) == 0 {
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// Build fake transition to cover all time.
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// This happens in fixed locations like "Etc/GMT0".
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tx = append(tx, zoneTrans{when: alpha, index: 0})
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}
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// Committed to succeed.
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l := &Location{zone: zone, tx: tx, name: name}
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// Fill in the cache with information about right now,
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// since that will be the most common lookup.
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sec, _, _ := now()
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for i := range tx {
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if tx[i].when <= sec && (i+1 == len(tx) || sec < tx[i+1].when) {
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l.cacheStart = tx[i].when
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l.cacheEnd = omega
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if i+1 < len(tx) {
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l.cacheEnd = tx[i+1].when
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}
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l.cacheZone = &l.zone[tx[i].index]
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}
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}
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return l, nil
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}
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// loadTzinfoFromDirOrZip returns the contents of the file with the given name
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// in dir. dir can either be an uncompressed zip file, or a directory.
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func loadTzinfoFromDirOrZip(dir, name string) ([]byte, error) {
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if len(dir) > 4 && dir[len(dir)-4:] == ".zip" {
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return loadTzinfoFromZip(dir, name)
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}
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if dir != "" {
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name = dir + "/" + name
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}
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return readFile(name)
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}
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// There are 500+ zoneinfo files. Rather than distribute them all
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// individually, we ship them in an uncompressed zip file.
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// Used this way, the zip file format serves as a commonly readable
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// container for the individual small files. We choose zip over tar
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// because zip files have a contiguous table of contents, making
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// individual file lookups faster, and because the per-file overhead
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// in a zip file is considerably less than tar's 512 bytes.
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// get4 returns the little-endian 32-bit value in b.
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func get4(b []byte) int {
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if len(b) < 4 {
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return 0
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}
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return int(b[0]) | int(b[1])<<8 | int(b[2])<<16 | int(b[3])<<24
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}
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// get2 returns the little-endian 16-bit value in b.
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func get2(b []byte) int {
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if len(b) < 2 {
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return 0
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}
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return int(b[0]) | int(b[1])<<8
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}
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// loadTzinfoFromZip returns the contents of the file with the given name
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// in the given uncompressed zip file.
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func loadTzinfoFromZip(zipfile, name string) ([]byte, error) {
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fd, err := open(zipfile)
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if err != nil {
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return nil, err
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}
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defer closefd(fd)
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const (
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zecheader = 0x06054b50
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zcheader = 0x02014b50
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ztailsize = 22
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zheadersize = 30
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zheader = 0x04034b50
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)
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buf := make([]byte, ztailsize)
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if err := preadn(fd, buf, -ztailsize); err != nil || get4(buf) != zecheader {
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return nil, errors.New("corrupt zip file " + zipfile)
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}
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n := get2(buf[10:])
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size := get4(buf[12:])
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off := get4(buf[16:])
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buf = make([]byte, size)
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if err := preadn(fd, buf, off); err != nil {
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return nil, errors.New("corrupt zip file " + zipfile)
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}
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for i := 0; i < n; i++ {
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// zip entry layout:
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// 0 magic[4]
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// 4 madevers[1]
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// 5 madeos[1]
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// 6 extvers[1]
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// 7 extos[1]
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// 8 flags[2]
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// 10 meth[2]
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// 12 modtime[2]
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// 14 moddate[2]
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// 16 crc[4]
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// 20 csize[4]
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// 24 uncsize[4]
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// 28 namelen[2]
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// 30 xlen[2]
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// 32 fclen[2]
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// 34 disknum[2]
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// 36 iattr[2]
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// 38 eattr[4]
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// 42 off[4]
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// 46 name[namelen]
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// 46+namelen+xlen+fclen - next header
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//
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if get4(buf) != zcheader {
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break
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}
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meth := get2(buf[10:])
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size := get4(buf[24:])
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namelen := get2(buf[28:])
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xlen := get2(buf[30:])
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fclen := get2(buf[32:])
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off := get4(buf[42:])
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zname := buf[46 : 46+namelen]
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buf = buf[46+namelen+xlen+fclen:]
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if string(zname) != name {
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continue
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}
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if meth != 0 {
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return nil, errors.New("unsupported compression for " + name + " in " + zipfile)
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}
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// zip per-file header layout:
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// 0 magic[4]
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// 4 extvers[1]
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// 5 extos[1]
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// 6 flags[2]
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// 8 meth[2]
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// 10 modtime[2]
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// 12 moddate[2]
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// 14 crc[4]
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// 18 csize[4]
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// 22 uncsize[4]
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// 26 namelen[2]
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// 28 xlen[2]
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// 30 name[namelen]
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// 30+namelen+xlen - file data
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//
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buf = make([]byte, zheadersize+namelen)
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if err := preadn(fd, buf, off); err != nil ||
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get4(buf) != zheader ||
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get2(buf[8:]) != meth ||
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get2(buf[26:]) != namelen ||
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string(buf[30:30+namelen]) != name {
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return nil, errors.New("corrupt zip file " + zipfile)
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}
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xlen = get2(buf[28:])
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buf = make([]byte, size)
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if err := preadn(fd, buf, off+30+namelen+xlen); err != nil {
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return nil, errors.New("corrupt zip file " + zipfile)
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}
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return buf, nil
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}
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return nil, syscall.ENOENT
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}
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// loadTzinfoFromTzdata returns the time zone information of the time zone
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// with the given name, from a tzdata database file as they are typically
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// found on android.
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var loadTzinfoFromTzdata func(file, name string) ([]byte, error)
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// loadTzinfo returns the time zone information of the time zone
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// with the given name, from a given source. A source may be a
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// timezone database directory, tzdata database file or an uncompressed
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// zip file, containing the contents of such a directory.
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func loadTzinfo(name string, source string) ([]byte, error) {
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if len(source) >= 6 && source[len(source)-6:] == "tzdata" {
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return loadTzinfoFromTzdata(source, name)
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}
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return loadTzinfoFromDirOrZip(source, name)
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}
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// loadLocation returns the Location with the given name from one of
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// the specified sources. See loadTzinfo for a list of supported sources.
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// The first timezone data matching the given name that is successfully loaded
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// and parsed is returned as a Location.
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func loadLocation(name string, sources []string) (z *Location, firstErr error) {
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for _, source := range sources {
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var zoneData, err = loadTzinfo(name, source)
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if err == nil {
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if z, err = LoadLocationFromTZData(name, zoneData); err == nil {
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return z, nil
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}
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}
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if firstErr == nil && err != syscall.ENOENT {
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firstErr = err
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}
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}
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if firstErr != nil {
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return nil, firstErr
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}
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return nil, errors.New("unknown time zone " + name)
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}
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// readFile reads and returns the content of the named file.
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// It is a trivial implementation of ioutil.ReadFile, reimplemented
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// here to avoid depending on io/ioutil or os.
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// It returns an error if name exceeds maxFileSize bytes.
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func readFile(name string) ([]byte, error) {
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f, err := open(name)
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if err != nil {
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return nil, err
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}
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defer closefd(f)
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var (
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buf [4096]byte
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ret []byte
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n int
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)
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for {
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n, err = read(f, buf[:])
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if n > 0 {
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ret = append(ret, buf[:n]...)
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}
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if n == 0 || err != nil {
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break
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}
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if len(ret) > maxFileSize {
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return nil, fileSizeError(name)
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}
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}
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return ret, err
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}
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