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Source file src/time/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  )
    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  }
    80  

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