1 files changed, 586 insertions, 0 deletions
diff --git a/src/time/zoneinfo_read.go b/src/time/zoneinfo_read.go
new file mode 100644
index 0000000..b983026
--- /dev/null
+++ b/src/time/zoneinfo_read.go
@@ -0,0 +1,586 @@
+// 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"
+)
+
+// registerLoadFromEmbeddedTZData is called by the time/tzdata package,
+// if it is imported.
+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
+}