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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"
)
// 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) 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)
}
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 p []byte
if p = d.read(16); len(p) != 16 || p[0] != 0 && p[0] != '2' && p[0] != '3' {
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
}
n[i] = int(nn)
}
// Transition times.
txtimes := dataIO{d.read(n[NTime] * 4), 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] * 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, badData
}
// If version == 2 or 3, 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]
zone := make([]zone, n[NZone])
for i := range zone {
var ok bool
var n uint32
if n, ok = zonedata.big4(); !ok {
return nil, badData
}
zone[i].offset = int(int32(n))
var b byte
if b, ok = zonedata.byte(); !ok {
return nil, badData
}
zone[i].isDST = b != 0
if b, ok = zonedata.byte(); !ok || int(b) >= len(abbrev) {
return nil, badData
}
zone[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
zone[i].name = name[4:]
}
}
}
// Now the transition time info.
tx := make([]zoneTrans, n[NTime])
for i := range tx {
var ok bool
var n uint32
if n, ok = txtimes.big4(); !ok {
return nil, badData
}
tx[i].when = int64(int32(n))
if int(txzones[i]) >= len(zone) {
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: zone, tx: tx, name: name}
// 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
if i+1 < len(tx) {
l.cacheEnd = tx[i+1].when
}
l.cacheZone = &l.zone[tx[i].index]
}
}
return l, nil
}
// 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, errors.New("open " + zipfile + ": " + err.Error())
}
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 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 ioutil.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
}