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         "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 }