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