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time: read 64-bit data if available

Also store 64-bit data in lib/time/zoneinfo.zip.

The comments argue that we don't need the 64-bit data until 2037 or
2106, but that turns out not to be the case. We also need them for
dates before December 13, 1901, which is time.Unix(-0x80000000, 0).

Fixes #30099

Change-Id: Ib8c9efb29b7b3c08531ae69912c588209d6320e9
Reviewed-on: https://go-review.googlesource.com/c/161202
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
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ianlancetaylor committed Feb 6, 2019
1 parent c1050a8 commit 068a832a7e176121a2c0767d55e774f10705c72b
Showing with 105 additions and 25 deletions.
  1. +0 −13 lib/time/update.bash
  2. BIN lib/time/zoneinfo.zip
  3. +84 −12 src/time/zoneinfo_read.go
  4. +21 −0 src/time/zoneinfo_test.go
@@ -21,21 +21,8 @@ curl -L -O https://www.iana.org/time-zones/repository/releases/tzdata$DATA.tar.g
tar xzf tzcode$CODE.tar.gz
tar xzf tzdata$DATA.tar.gz

# Turn off 64-bit output in time zone files.
# We don't need those until 2037.
perl -p -i -e 's/pass <= 2/pass <= 1/' zic.c

make CFLAGS=-DSTD_INSPIRED AWK=awk TZDIR=zoneinfo posix_only

# America/Los_Angeles should not be bigger than 1100 bytes.
# If it is, we probably failed to disable the 64-bit output, which
# triples the size of the files.
size=$(ls -l zoneinfo/America/Los_Angeles | awk '{print $5}')
if [ $size -gt 1200 ]; then
echo 'zone file too large; 64-bit edit failed?' >&2
exit 2
fi

cd zoneinfo
rm -f ../../zoneinfo.zip
zip -0 -r ../../zoneinfo.zip *
BIN +413 KB (220%) lib/time/zoneinfo.zip
Binary file not shown.
@@ -59,6 +59,16 @@ func (d *dataIO) big4() (n uint32, ok bool) {
return uint32(p[3]) | uint32(p[2])<<8 | uint32(p[1])<<16 | uint32(p[0])<<24, true
}

func (d *dataIO) big8() (n uint64, ok bool) {
n1, ok1 := d.big4()
n2, ok2 := d.big4()
if !ok1 || !ok2 {
d.error = true
return 0, false
}
return (uint64(n1) << 32) | uint64(n2), true
}

func (d *dataIO) byte() (n byte, ok bool) {
p := d.read(1)
if len(p) < 1 {
@@ -93,9 +103,21 @@ func LoadLocationFromTZData(name string, data []byte) (*Location, error) {
}

// 1-byte version, then 15 bytes of padding
var version int
var p []byte
if p = d.read(16); len(p) != 16 || p[0] != 0 && p[0] != '2' && p[0] != '3' {
if p = d.read(16); len(p) != 16 {
return nil, badData
} else {
switch p[0] {
case 0:
version = 1
case '2':
version = 2
case '3':
version = 3
default:
return nil, badData
}
}

// six big-endian 32-bit integers:
@@ -119,11 +141,53 @@ func LoadLocationFromTZData(name string, data []byte) (*Location, error) {
if !ok {
return nil, badData
}
if uint32(int(nn)) != nn {
return nil, badData
}
n[i] = int(nn)
}

// If we have version 2 or 3, then the data is first written out
// in a 32-bit format, then written out again in a 64-bit format.
// Skip the 32-bit format and read the 64-bit one, as it can
// describe a broader range of dates.

is64 := false
if version > 1 {
// Skip the 32-bit data.
skip := n[NTime]*4 +
n[NTime] +
n[NZone]*6 +
n[NChar] +
n[NLeap]*8 +
n[NStdWall] +
n[NUTCLocal]
// Skip the version 2 header that we just read.
skip += 4 + 16
d.read(skip)

is64 = true

// Read the counts again, they can differ.
for i := 0; i < 6; i++ {
nn, ok := d.big4()
if !ok {
return nil, badData
}
if uint32(int(nn)) != nn {
return nil, badData
}
n[i] = int(nn)
}
}

size := 4
if is64 {
size = 8
}

// Transition times.
txtimes := dataIO{d.read(n[NTime] * 4), false}
txtimes := dataIO{d.read(n[NTime] * size), false}

// Time zone indices for transition times.
txzones := d.read(n[NTime])
@@ -135,7 +199,7 @@ func LoadLocationFromTZData(name string, data []byte) (*Location, error) {
abbrev := d.read(n[NChar])

// Leap-second time pairs
d.read(n[NLeap] * 8)
d.read(n[NLeap] * (size + 4))

// Whether tx times associated with local time types
// are specified as standard time or wall time.
@@ -149,10 +213,6 @@ func LoadLocationFromTZData(name string, data []byte) (*Location, error) {
return nil, badData
}

// If version == 2 or 3, the entire file repeats, this time using
// 8-byte ints for txtimes and leap seconds.
// We won't need those until 2106.

// Now we can build up a useful data structure.
// First the zone information.
// utcoff[4] isdst[1] nameindex[1]
@@ -163,6 +223,9 @@ func LoadLocationFromTZData(name string, data []byte) (*Location, error) {
if n, ok = zonedata.big4(); !ok {
return nil, badData
}
if uint32(int(n)) != n {
return nil, badData
}
zone[i].offset = int(int32(n))
var b byte
if b, ok = zonedata.byte(); !ok {
@@ -186,12 +249,21 @@ func LoadLocationFromTZData(name string, data []byte) (*Location, error) {
// Now the transition time info.
tx := make([]zoneTrans, n[NTime])
for i := range tx {
var ok bool
var n uint32
if n, ok = txtimes.big4(); !ok {
return nil, badData
var n int64
if !is64 {
if n4, ok := txtimes.big4(); !ok {
return nil, badData
} else {
n = int64(int32(n4))
}
} else {
if n8, ok := txtimes.big8(); !ok {
return nil, badData
} else {
n = int64(n8)
}
}
tx[i].when = int64(int32(n))
tx[i].when = n
if int(txzones[i]) >= len(zone) {
return nil, badData
}
@@ -152,3 +152,24 @@ func TestLoadLocationFromTZData(t *testing.T) {
t.Errorf("return values of LoadLocationFromTZData and LoadLocation don't match")
}
}

// Issue 30099.
func TestEarlyLocation(t *testing.T) {
time.ForceZipFileForTesting(true)
defer time.ForceZipFileForTesting(false)

const locName = "America/New_York"
loc, err := time.LoadLocation(locName)
if err != nil {
t.Fatal(err)
}

d := time.Date(1900, time.January, 1, 0, 0, 0, 0, loc)
tzName, tzOffset := d.Zone()
if want := "EST"; tzName != want {
t.Errorf("Zone name == %s, want %s", tzName, want)
}
if want := -18000; tzOffset != want {
t.Errorf("Zone offset == %d, want %d", tzOffset, want)
}
}

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