zoneinfo_windows.go

Documentation: time

     1  // Copyright 2009 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  package time
     6  
     7  import (
     8  	"errors"
     9  	"internal/syscall/windows/registry"
    10  	"runtime"
    11  	"syscall"
    12  )
    13  
    14  var zoneSources = []string{
    15  	runtime.GOROOT() + "/lib/time/zoneinfo.zip",
    16  }
    17  
    18  // TODO(rsc): Fall back to copy of zoneinfo files.
    19  
    20  // BUG(brainman,rsc): On Windows, the operating system does not provide complete
    21  // time zone information.
    22  // The implementation assumes that this year's rules for daylight savings
    23  // time apply to all previous and future years as well.
    24  
    25  // matchZoneKey checks if stdname and dstname match the corresponding key
    26  // values "MUI_Std" and MUI_Dlt" or "Std" and "Dlt" (the latter down-level
    27  // from Vista) in the kname key stored under the open registry key zones.
    28  func matchZoneKey(zones registry.Key, kname string, stdname, dstname string) (matched bool, err2 error) {
    29  	k, err := registry.OpenKey(zones, kname, registry.READ)
    30  	if err != nil {
    31  		return false, err
    32  	}
    33  	defer k.Close()
    34  
    35  	var std, dlt string
    36  	if err = registry.LoadRegLoadMUIString(); err == nil {
    37  		// Try MUI_Std and MUI_Dlt first, fallback to Std and Dlt if *any* error occurs
    38  		std, err = k.GetMUIStringValue("MUI_Std")
    39  		if err == nil {
    40  			dlt, err = k.GetMUIStringValue("MUI_Dlt")
    41  		}
    42  	}
    43  	if err != nil { // Fallback to Std and Dlt
    44  		if std, _, err = k.GetStringValue("Std"); err != nil {
    45  			return false, err
    46  		}
    47  		if dlt, _, err = k.GetStringValue("Dlt"); err != nil {
    48  			return false, err
    49  		}
    50  	}
    51  
    52  	if std != stdname {
    53  		return false, nil
    54  	}
    55  	if dlt != dstname && dstname != stdname {
    56  		return false, nil
    57  	}
    58  	return true, nil
    59  }
    60  
    61  // toEnglishName searches the registry for an English name of a time zone
    62  // whose zone names are stdname and dstname and returns the English name.
    63  func toEnglishName(stdname, dstname string) (string, error) {
    64  	k, err := registry.OpenKey(registry.LOCAL_MACHINE, `SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones`, registry.ENUMERATE_SUB_KEYS|registry.QUERY_VALUE)
    65  	if err != nil {
    66  		return "", err
    67  	}
    68  	defer k.Close()
    69  
    70  	names, err := k.ReadSubKeyNames()
    71  	if err != nil {
    72  		return "", err
    73  	}
    74  	for _, name := range names {
    75  		matched, err := matchZoneKey(k, name, stdname, dstname)
    76  		if err == nil && matched {
    77  			return name, nil
    78  		}
    79  	}
    80  	return "", errors.New(`English name for time zone "` + stdname + `" not found in registry`)
    81  }
    82  
    83  // extractCAPS extracts capital letters from description desc.
    84  func extractCAPS(desc string) string {
    85  	var short []rune
    86  	for _, c := range desc {
    87  		if 'A' <= c && c <= 'Z' {
    88  			short = append(short, c)
    89  		}
    90  	}
    91  	return string(short)
    92  }
    93  
    94  // abbrev returns the abbreviations to use for the given zone z.
    95  func abbrev(z *syscall.Timezoneinformation) (std, dst string) {
    96  	stdName := syscall.UTF16ToString(z.StandardName[:])
    97  	a, ok := abbrs[stdName]
    98  	if !ok {
    99  		dstName := syscall.UTF16ToString(z.DaylightName[:])
   100  		// Perhaps stdName is not English. Try to convert it.
   101  		englishName, err := toEnglishName(stdName, dstName)
   102  		if err == nil {
   103  			a, ok = abbrs[englishName]
   104  			if ok {
   105  				return a.std, a.dst
   106  			}
   107  		}
   108  		// fallback to using capital letters
   109  		return extractCAPS(stdName), extractCAPS(dstName)
   110  	}
   111  	return a.std, a.dst
   112  }
   113  
   114  // pseudoUnix returns the pseudo-Unix time (seconds since Jan 1 1970 *LOCAL TIME*)
   115  // denoted by the system date+time d in the given year.
   116  // It is up to the caller to convert this local time into a UTC-based time.
   117  func pseudoUnix(year int, d *syscall.Systemtime) int64 {
   118  	// Windows specifies daylight savings information in "day in month" format:
   119  	// d.Month is month number (1-12)
   120  	// d.DayOfWeek is appropriate weekday (Sunday=0 to Saturday=6)
   121  	// d.Day is week within the month (1 to 5, where 5 is last week of the month)
   122  	// d.Hour, d.Minute and d.Second are absolute time
   123  	day := 1
   124  	t := Date(year, Month(d.Month), day, int(d.Hour), int(d.Minute), int(d.Second), 0, UTC)
   125  	i := int(d.DayOfWeek) - int(t.Weekday())
   126  	if i < 0 {
   127  		i += 7
   128  	}
   129  	day += i
   130  	if week := int(d.Day) - 1; week < 4 {
   131  		day += week * 7
   132  	} else {
   133  		// "Last" instance of the day.
   134  		day += 4 * 7
   135  		if day > daysIn(Month(d.Month), year) {
   136  			day -= 7
   137  		}
   138  	}
   139  	return t.sec() + int64(day-1)*secondsPerDay + internalToUnix
   140  }
   141  
   142  func initLocalFromTZI(i *syscall.Timezoneinformation) {
   143  	l := &localLoc
   144  
   145  	l.name = "Local"
   146  
   147  	nzone := 1
   148  	if i.StandardDate.Month > 0 {
   149  		nzone++
   150  	}
   151  	l.zone = make([]zone, nzone)
   152  
   153  	stdname, dstname := abbrev(i)
   154  
   155  	std := &l.zone[0]
   156  	std.name = stdname
   157  	if nzone == 1 {
   158  		// No daylight savings.
   159  		std.offset = -int(i.Bias) * 60
   160  		l.cacheStart = alpha
   161  		l.cacheEnd = omega
   162  		l.cacheZone = std
   163  		l.tx = make([]zoneTrans, 1)
   164  		l.tx[0].when = l.cacheStart
   165  		l.tx[0].index = 0
   166  		return
   167  	}
   168  
   169  	// StandardBias must be ignored if StandardDate is not set,
   170  	// so this computation is delayed until after the nzone==1
   171  	// return above.
   172  	std.offset = -int(i.Bias+i.StandardBias) * 60
   173  
   174  	dst := &l.zone[1]
   175  	dst.name = dstname
   176  	dst.offset = -int(i.Bias+i.DaylightBias) * 60
   177  	dst.isDST = true
   178  
   179  	// Arrange so that d0 is first transition date, d1 second,
   180  	// i0 is index of zone after first transition, i1 second.
   181  	d0 := &i.StandardDate
   182  	d1 := &i.DaylightDate
   183  	i0 := 0
   184  	i1 := 1
   185  	if d0.Month > d1.Month {
   186  		d0, d1 = d1, d0
   187  		i0, i1 = i1, i0
   188  	}
   189  
   190  	// 2 tx per year, 100 years on each side of this year
   191  	l.tx = make([]zoneTrans, 400)
   192  
   193  	t := Now().UTC()
   194  	year := t.Year()
   195  	txi := 0
   196  	for y := year - 100; y < year+100; y++ {
   197  		tx := &l.tx[txi]
   198  		tx.when = pseudoUnix(y, d0) - int64(l.zone[i1].offset)
   199  		tx.index = uint8(i0)
   200  		txi++
   201  
   202  		tx = &l.tx[txi]
   203  		tx.when = pseudoUnix(y, d1) - int64(l.zone[i0].offset)
   204  		tx.index = uint8(i1)
   205  		txi++
   206  	}
   207  }
   208  
   209  var usPacific = syscall.Timezoneinformation{
   210  	Bias: 8 * 60,
   211  	StandardName: [32]uint16{
   212  		'P', 'a', 'c', 'i', 'f', 'i', 'c', ' ', 'S', 't', 'a', 'n', 'd', 'a', 'r', 'd', ' ', 'T', 'i', 'm', 'e',
   213  	},
   214  	StandardDate: syscall.Systemtime{Month: 11, Day: 1, Hour: 2},
   215  	DaylightName: [32]uint16{
   216  		'P', 'a', 'c', 'i', 'f', 'i', 'c', ' ', 'D', 'a', 'y', 'l', 'i', 'g', 'h', 't', ' ', 'T', 'i', 'm', 'e',
   217  	},
   218  	DaylightDate: syscall.Systemtime{Month: 3, Day: 2, Hour: 2},
   219  	DaylightBias: -60,
   220  }
   221  
   222  var aus = syscall.Timezoneinformation{
   223  	Bias: -10 * 60,
   224  	StandardName: [32]uint16{
   225  		'A', 'U', 'S', ' ', 'E', 'a', 's', 't', 'e', 'r', 'n', ' ', 'S', 't', 'a', 'n', 'd', 'a', 'r', 'd', ' ', 'T', 'i', 'm', 'e',
   226  	},
   227  	StandardDate: syscall.Systemtime{Month: 4, Day: 1, Hour: 3},
   228  	DaylightName: [32]uint16{
   229  		'A', 'U', 'S', ' ', 'E', 'a', 's', 't', 'e', 'r', 'n', ' ', 'D', 'a', 'y', 'l', 'i', 'g', 'h', 't', ' ', 'T', 'i', 'm', 'e',
   230  	},
   231  	DaylightDate: syscall.Systemtime{Month: 10, Day: 1, Hour: 2},
   232  	DaylightBias: -60,
   233  }
   234  
   235  func initLocal() {
   236  	var i syscall.Timezoneinformation
   237  	if _, err := syscall.GetTimeZoneInformation(&i); err != nil {
   238  		localLoc.name = "UTC"
   239  		return
   240  	}
   241  	initLocalFromTZI(&i)
   242  }
   243
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