zoneinfo_android.go

Documentation: time

     1  // Copyright 2016 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Parse the "tzdata" packed timezone file used on Android.
     6  // The format is lifted from ZoneInfoDB.java and ZoneInfo.java in
     7  // java/libcore/util in the AOSP.
     8  
     9  package time
    10  
    11  import (
    12  	"errors"
    13  	"runtime"
    14  	"syscall"
    15  )
    16  
    17  var zoneSources = []string{
    18  	"/system/usr/share/zoneinfo/tzdata",
    19  	"/data/misc/zoneinfo/current/tzdata",
    20  	runtime.GOROOT() + "/lib/time/zoneinfo.zip",
    21  }
    22  
    23  func initLocal() {
    24  	// TODO(elias.naur): getprop persist.sys.timezone
    25  	localLoc = *UTC
    26  }
    27  
    28  func init() {
    29  	loadTzinfoFromTzdata = androidLoadTzinfoFromTzdata
    30  }
    31  
    32  func androidLoadTzinfoFromTzdata(file, name string) ([]byte, error) {
    33  	const (
    34  		headersize = 12 + 3*4
    35  		namesize   = 40
    36  		entrysize  = namesize + 3*4
    37  	)
    38  	if len(name) > namesize {
    39  		return nil, errors.New(name + " is longer than the maximum zone name length (40 bytes)")
    40  	}
    41  	fd, err := open(file)
    42  	if err != nil {
    43  		return nil, err
    44  	}
    45  	defer closefd(fd)
    46  
    47  	buf := make([]byte, headersize)
    48  	if err := preadn(fd, buf, 0); err != nil {
    49  		return nil, errors.New("corrupt tzdata file " + file)
    50  	}
    51  	d := dataIO{buf, false}
    52  	if magic := d.read(6); string(magic) != "tzdata" {
    53  		return nil, errors.New("corrupt tzdata file " + file)
    54  	}
    55  	d = dataIO{buf[12:], false}
    56  	indexOff, _ := d.big4()
    57  	dataOff, _ := d.big4()
    58  	indexSize := dataOff - indexOff
    59  	entrycount := indexSize / entrysize
    60  	buf = make([]byte, indexSize)
    61  	if err := preadn(fd, buf, int(indexOff)); err != nil {
    62  		return nil, errors.New("corrupt tzdata file " + file)
    63  	}
    64  	for i := 0; i < int(entrycount); i++ {
    65  		entry := buf[i*entrysize : (i+1)*entrysize]
    66  		// len(name) <= namesize is checked at function entry
    67  		if string(entry[:len(name)]) != name {
    68  			continue
    69  		}
    70  		d := dataIO{entry[namesize:], false}
    71  		off, _ := d.big4()
    72  		size, _ := d.big4()
    73  		buf := make([]byte, size)
    74  		if err := preadn(fd, buf, int(off+dataOff)); err != nil {
    75  			return nil, errors.New("corrupt tzdata file " + file)
    76  		}
    77  		return buf, nil
    78  	}
    79  	return nil, syscall.ENOENT
    80  }
    81
View as plain text