1 files changed, 285 insertions, 0 deletions
diff --git a/src/pkg/time/zoneinfo.go b/src/pkg/time/zoneinfo.go
new file mode 100644
index 000000000..751afc931
--- /dev/null
+++ b/src/pkg/time/zoneinfo.go
@@ -0,0 +1,285 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Parse "zoneinfo" time zone file.
+// This is a fairly standard file format used on OS X, Linux, BSD, Sun, and others.
+// See tzfile(5), http://en.wikipedia.org/wiki/Zoneinfo,
+// and ftp://munnari.oz.au/pub/oldtz/
+
+package time
+
+import (
+	"io";
+	"once";
+	"os"
+)
+
+const (
+	maxFileSize = 8192;	// actual files are closer to 1K
+	headerSize = 4+16+4*7;
+
+	zoneDir = "/usr/share/zoneinfo/";
+)
+
+// Errors that can be generated recovering time zone information.
+type TimeZoneError struct {
+	os.ErrorString
+}
+
+var errShort = TimeZoneError{ "time: short zone file" }
+var errInvalid = TimeZoneError{ "time: invalid zone file" }
+var errLong = TimeZoneError{ "time: zone file too long" }
+
+// Simple I/O interface to binary blob of data.
+type data struct {
+	p []byte;
+	error bool;
+}
+
+
+func (d *data) read(n int) []byte {
+	if len(d.p) < n {
+		d.p = nil;
+		d.error = true;
+		return nil;
+	}
+	p := d.p[0:n];
+	d.p = d.p[n:len(d.p)];
+	return p
+}
+
+func (d *data) big4() (n uint32, ok bool) {
+	p := d.read(4);
+	if len(p) < 4 {
+		d.error = true;
+		return 0, false
+	}
+	return uint32(p[0]) << 24 | uint32(p[1]) << 16 | uint32(p[2]) << 8 | uint32(p[3]), true
+}
+
+func (d *data) byte() (n byte, ok bool) {
+	p := d.read(1);
+	if len(p) < 1 {
+		d.error = true;
+		return 0, false
+	}
+	return p[0], true
+}
+
+
+// Make a string by stopping at the first NUL
+func byteString(p []byte) string {
+	for i := 0; i < len(p); i++ {
+		if p[i] == 0 {
+			return string(p[0:i])
+		}
+	}
+	return string(p)
+}
+
+// Parsed representation
+type zone struct {
+	utcoff int;
+	isdst bool;
+	name string;
+}
+
+type zonetime struct {
+	time int32;		// transition time, in seconds since 1970 GMT
+	zone *zone;		// the zone that goes into effect at that time
+	isstd, isutc bool;	// ignored - no idea what these mean
+}
+
+func parseinfo(bytes []byte) (zt []zonetime, err os.Error) {
+	d := data{bytes, false};
+
+	// 4-byte magic "TZif"
+	if magic := d.read(4); string(magic) != "TZif" {
+		return nil, TimeZoneError{ "time: bad zone magic" }
+	}
+
+	// 1-byte version, then 15 bytes of padding
+	var p []byte;
+	if p = d.read(16); len(p) != 16 || p[0] != 0 && p[0] != '2' {
+		return nil, TimeZoneError { "time: bad zone file version" }
+	}
+	vers := p[0];
+
+	// six big-endian 32-bit integers:
+	//	number of UTC/local indicators
+	//	number of standard/wall indicators
+	//	number of leap seconds
+	//	number of transition times
+	//	number of local time zones
+	//	number of characters of time zone abbrev strings
+	const (
+		NUTCLocal = iota;
+		NStdWall;
+		NLeap;
+		NTime;
+		NZone;
+		NChar
+	)
+	var n [6]int;
+	for i := 0; i < 6; i++ {
+		nn, ok := d.big4();
+		if !ok {
+			return nil, errShort
+		}
+		n[i] = int(nn);
+	}
+
+	// Transition times.
+	txtimes := data{d.read(n[NTime]*4), false};
+
+	// Time zone indices for transition times.
+	txzones := d.read(n[NTime]);
+
+	// Zone info structures
+	zonedata := data{d.read(n[NZone]*6), false};
+
+	// Time zone abbreviations.
+	abbrev := d.read(n[NChar]);
+
+	// Leap-second time pairs
+	leapdata := data{d.read(n[NLeap]*8), false};
+
+	// Whether tx times associated with local time types
+	// are specified as standard time or wall time.
+	isstd := d.read(n[NStdWall]);
+
+	// Whether tx times associated with local time types
+	// are specified as UTC or local time.
+	isutc := d.read(n[NUTCLocal]);
+
+	if d.error {	// ran out of data
+		return nil, errShort
+	}
+
+	// If version == 2, 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]
+	z := make([]zone, n[NZone]);
+	for i := 0; i < len(z); i++ {
+		var ok bool;
+		var n uint32;
+		if n, ok = zonedata.big4(); !ok {
+			return nil, errShort
+		}
+		z[i].utcoff = int(n);
+		var b byte;
+		if b, ok = zonedata.byte(); !ok {
+			return nil, errShort
+		}
+		z[i].isdst = b != 0;
+		if b, ok = zonedata.byte(); !ok || int(b) >= len(abbrev) {
+			return nil, errInvalid
+		}
+		z[i].name = byteString(abbrev[b:len(abbrev)])
+	}
+
+	// Now the transition time info.
+	zt = make([]zonetime, n[NTime]);
+	for i := 0; i < len(zt); i++ {
+		var ok bool;
+		var n uint32;
+		if n, ok = txtimes.big4(); !ok {
+			return nil, errShort
+		}
+		zt[i].time = int32(n);
+		if int(txzones[i]) >= len(z) {
+			return nil, errInvalid
+		}
+		zt[i].zone = &z[txzones[i]];
+		if i < len(isstd) {
+			zt[i].isstd = isstd[i] != 0
+		}
+		if i < len(isutc) {
+			zt[i].isutc = isutc[i] != 0
+		}
+	}
+	return zt, nil
+}
+
+func readfile(name string, max int) (p []byte, err os.Error) {
+	f, e := os.Open(name, os.O_RDONLY, 0);
+	if e != nil {
+		return nil, e;
+	}
+	p = make([]byte, max);
+	n, err1 := io.FullRead(f, p);
+	f.Close();
+	if err1 == nil {	// too long
+		return nil, errLong;
+	}
+	if err1 != io.ErrEOF {
+		return nil, err1;
+	}
+	return p[0:n], nil;
+}
+
+func readinfofile(name string) ([]zonetime, os.Error) {
+	buf, err := readfile(name, maxFileSize);
+	if err != nil {
+		goto Error;
+	}
+	tx, err := parseinfo(buf);
+	if err != nil {
+		goto Error;
+	}
+	return tx, nil;
+
+Error:
+	if tzerr, ok := err.(TimeZoneError); ok {
+		tzerr.ErrorString = os.ErrorString(tzerr.String() + ": " + name)
+	}
+	return nil, err
+}
+
+var zones []zonetime
+var zoneerr os.Error
+
+func setupZone() {
+	// consult $TZ to find the time zone to use.
+	// no $TZ means use the system default /etc/localtime.
+	// $TZ="" means use UTC.
+	// $TZ="foo" means use /usr/share/zoneinfo/foo.
+
+	tz, err := os.Getenv("TZ");
+	var file string;
+	switch {
+	case err == os.ENOENV:
+		zones, zoneerr = readinfofile("/etc/localtime");
+	case err != nil:
+		zoneerr = err;
+	case len(tz) > 0:
+		zones, zoneerr = readinfofile(zoneDir + tz);
+	case len(tz) == 0:
+		// do nothing: use UTC
+	}
+}
+
+func lookupTimezone(sec int64) (zone string, offset int, err os.Error) {
+	once.Do(setupZone);
+	if zoneerr != nil || len(zones) == 0 {
+		return "UTC", 0, zoneerr
+	}
+
+	// Binary search for entry with largest time <= sec
+	tz := zones;
+	for len(tz) > 1 {
+		m := len(tz)/2;
+		if sec < int64(tz[m].time) {
+			tz = tz[0:m]
+		} else {
+			tz = tz[m:len(tz)]
+		}
+	}
+	z := tz[0].zone;
+	return z.name, z.utcoff, nil
+}