libgo/go/time/zoneinfo_android.go

   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 )
  15
  16 var zoneSources = []string{
  17         "/system/usr/share/zoneinfo/tzdata",
  18         "/data/misc/zoneinfo/current/tzdata",
  19         runtime.GOROOT() + "/lib/time/zoneinfo.zip",
  20 }
  21
  22 func initLocal() {
  23         // TODO(elias.naur): getprop persist.sys.timezone
  24         localLoc = *UTC
  25 }
  26
  27 func init() {
  28         loadTzinfoFromTzdata = androidLoadTzinfoFromTzdata
  29 }
  30
  31 func androidLoadTzinfoFromTzdata(file, name string) ([]byte, error) {
  32         const (
  33                 headersize = 12 + 3*4
  34                 namesize   = 40
  35                 entrysize  = namesize + 3*4
  36         )
  37         if len(name) > namesize {
  38                 return nil, errors.New(name + " is longer than the maximum zone name length (40 bytes)")
  39         }
  40         fd, err := open(file)
  41         if err != nil {
  42                 return nil, err
  43         }
  44         defer closefd(fd)
  45
  46         buf := make([]byte, headersize)
  47         if err := preadn(fd, buf, 0); err != nil {
  48                 return nil, errors.New("corrupt tzdata file " + file)
  49         }
  50         d := dataIO{buf, false}
  51         if magic := d.read(6); string(magic) != "tzdata" {
  52                 return nil, errors.New("corrupt tzdata file " + file)
  53         }
  54         d = dataIO{buf[12:], false}
  55         indexOff, _ := d.big4()
  56         dataOff, _ := d.big4()
  57         indexSize := dataOff - indexOff
  58         entrycount := indexSize / entrysize
  59         buf = make([]byte, indexSize)
  60         if err := preadn(fd, buf, int(indexOff)); err != nil {
  61                 return nil, errors.New("corrupt tzdata file " + file)
  62         }
  63         for i := 0; i < int(entrycount); i++ {
  64                 entry := buf[i*entrysize : (i+1)*entrysize]
  65                 // len(name) <= namesize is checked at function entry
  66                 if string(entry[:len(name)]) != name {
  67                         continue
  68                 }
  69                 d := dataIO{entry[namesize:], false}
  70                 off, _ := d.big4()
  71                 size, _ := d.big4()
  72                 buf := make([]byte, size)
  73                 if err := preadn(fd, buf, int(off+dataOff)); err != nil {
  74                         return nil, errors.New("corrupt tzdata file " + file)
  75                 }
  76                 return buf, nil
  77         }
  78         return nil, errors.New("cannot find " + name + " in tzdata file " + file)
  79 }