1 files changed, 156 insertions, 0 deletions
diff --git a/src/time/genzabbrs.go b/src/time/genzabbrs.go
new file mode 100644
index 0000000..7dbd22f
--- /dev/null
+++ b/src/time/genzabbrs.go
@@ -0,0 +1,156 @@
+// Copyright 2013 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.
+
+//go:build ignore
+
+//
+// usage:
+//
+// go run genzabbrs.go -output zoneinfo_abbrs_windows.go
+//
+
+package main
+
+import (
+	"bytes"
+	"encoding/xml"
+	"flag"
+	"go/format"
+	"io"
+	"log"
+	"net/http"
+	"os"
+	"sort"
+	"text/template"
+	"time"
+)
+
+var filename = flag.String("output", "zoneinfo_abbrs_windows.go", "output file name")
+
+// getAbbrs finds timezone abbreviations (standard and daylight saving time)
+// for location l.
+func getAbbrs(l *time.Location) (st, dt string) {
+	t := time.Date(time.Now().Year(), 0, 1, 0, 0, 0, 0, l)
+	abbr1, off1 := t.Zone()
+	for i := 0; i < 12; i++ {
+		t = t.AddDate(0, 1, 0)
+		abbr2, off2 := t.Zone()
+		if abbr1 != abbr2 {
+			if off2-off1 < 0 { // southern hemisphere
+				abbr1, abbr2 = abbr2, abbr1
+			}
+			return abbr1, abbr2
+		}
+	}
+	return abbr1, abbr1
+}
+
+type zone struct {
+	WinName  string
+	UnixName string
+	StTime   string
+	DSTime   string
+}
+
+const wzURL = "https://raw.githubusercontent.com/unicode-org/cldr/main/common/supplemental/windowsZones.xml"
+
+type MapZone struct {
+	Other     string `xml:"other,attr"`
+	Territory string `xml:"territory,attr"`
+	Type      string `xml:"type,attr"`
+}
+
+type SupplementalData struct {
+	Zones []MapZone `xml:"windowsZones>mapTimezones>mapZone"`
+}
+
+func readWindowsZones() ([]*zone, error) {
+	r, err := http.Get(wzURL)
+	if err != nil {
+		return nil, err
+	}
+	defer r.Body.Close()
+
+	data, err := io.ReadAll(r.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	var sd SupplementalData
+	err = xml.Unmarshal(data, &sd)
+	if err != nil {
+		return nil, err
+	}
+	zs := make([]*zone, 0)
+	for _, z := range sd.Zones {
+		if z.Territory != "001" {
+			// to avoid dups. I don't know why.
+			continue
+		}
+		l, err := time.LoadLocation(z.Type)
+		if err != nil {
+			return nil, err
+		}
+		st, dt := getAbbrs(l)
+		zs = append(zs, &zone{
+			WinName:  z.Other,
+			UnixName: z.Type,
+			StTime:   st,
+			DSTime:   dt,
+		})
+	}
+	return zs, nil
+}
+
+func main() {
+	flag.Parse()
+	zs, err := readWindowsZones()
+	if err != nil {
+		log.Fatal(err)
+	}
+	sort.Slice(zs, func(i, j int) bool {
+		return zs[i].UnixName < zs[j].UnixName
+	})
+	var v = struct {
+		URL string
+		Zs  []*zone
+	}{
+		wzURL,
+		zs,
+	}
+	var buf bytes.Buffer
+	err = template.Must(template.New("prog").Parse(prog)).Execute(&buf, v)
+	if err != nil {
+		log.Fatal(err)
+	}
+	data, err := format.Source(buf.Bytes())
+	if err != nil {
+		log.Fatal(err)
+	}
+	err = os.WriteFile(*filename, data, 0644)
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+
+const prog = `
+// Copyright 2013 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.
+
+// Code generated by genzabbrs.go; DO NOT EDIT.
+// Based on information from {{.URL}}
+
+package time
+
+type abbr struct {
+	std string
+	dst string
+}
+
+var abbrs = map[string]abbr{
+{{range .Zs}}	"{{.WinName}}": {"{{.StTime}}", "{{.DSTime}}"}, // {{.UnixName}}
+{{end}}}
+
+`