Revert "time: enable ZONEINFO tzdata file support and error reporting"

This reverts commit 630d176e.

Reason for revert: the CL moves a parser for what appears to be an
Android-specific file format into the main code and makes it available
on all platforms. Android-specific file formats should be limited to
Android.

Change-Id: I3f19fe03673d65ed1446a0dcf95e5986053e10c0
Reviewed-on: https://go-review.googlesource.com/77950Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/time/zoneinfo.go

@@ -272,7 +272,7 @@ var zoneinfoOnce sync.Once
 //
 // The time zone database needed by LoadLocation may not be
 // present on all systems, especially non-Unix systems.
-// LoadLocation looks in the directory, uncompressed zip file, or tzdata file
+// LoadLocation looks in the directory or uncompressed zip file
 // named by the ZONEINFO environment variable, if any, then looks in
 // known installation locations on Unix systems,
 // and finally looks in $GOROOT/lib/time/zoneinfo.zip.
@@ -292,13 +292,14 @@ func LoadLocation(name string) (*Location, error) {
 		env, _ := syscall.Getenv("ZONEINFO")
 		zoneinfo = &env
 	})
-	sources := zoneSources
 	if *zoneinfo != "" {
-		sources = make([]string, len(zoneSources)+1)
-		sources[0] = *zoneinfo
-		copy(sources[1:], zoneSources)
+		if zoneData, err := loadTzinfoFromDirOrZip(*zoneinfo, name); err == nil {
+			if z, err := newLocationFromTzinfo(name, zoneData); err == nil {
+				return z, nil
 			}
-	return loadLocation(name, sources)
+		}
+	}
+	return loadLocation(name, zoneSources)
 }
 
 // containsDotDot reports whether s contains "..".

src/time/zoneinfo_android.go

@@ -9,6 +9,7 @@
 package time
 
 import (
+	"errors"
 	"runtime"
 )
 
@@ -22,3 +23,57 @@ func initLocal() {
 	// TODO(elias.naur): getprop persist.sys.timezone
 	localLoc = *UTC
 }
+
+func init() {
+	loadTzinfoFromTzdata = androidLoadTzinfoFromTzdata
+}
+
+func androidLoadTzinfoFromTzdata(file, name string) ([]byte, error) {
+	const (
+		headersize = 12 + 3*4
+		namesize   = 40
+		entrysize  = namesize + 3*4
+	)
+	if len(name) > namesize {
+		return nil, errors.New(name + " is longer than the maximum zone name length (40 bytes)")
+	}
+	fd, err := open(file)
+	if err != nil {
+		return nil, err
+	}
+	defer closefd(fd)
+
+	buf := make([]byte, headersize)
+	if err := preadn(fd, buf, 0); err != nil {
+		return nil, errors.New("corrupt tzdata file " + file)
+	}
+	d := data{buf, false}
+	if magic := d.read(6); string(magic) != "tzdata" {
+		return nil, errors.New("corrupt tzdata file " + file)
+	}
+	d = data{buf[12:], false}
+	indexOff, _ := d.big4()
+	dataOff, _ := d.big4()
+	indexSize := dataOff - indexOff
+	entrycount := indexSize / entrysize
+	buf = make([]byte, indexSize)
+	if err := preadn(fd, buf, int(indexOff)); err != nil {
+		return nil, errors.New("corrupt tzdata file " + file)
+	}
+	for i := 0; i < int(entrycount); i++ {
+		entry := buf[i*entrysize : (i+1)*entrysize]
+		// len(name) <= namesize is checked at function entry
+		if string(entry[:len(name)]) != name {
+			continue
+		}
+		d := data{entry[namesize:], false}
+		off, _ := d.big4()
+		size, _ := d.big4()
+		buf := make([]byte, size)
+		if err := preadn(fd, buf, int(off+dataOff)); err != nil {
+			return nil, errors.New("corrupt tzdata file " + file)
+		}
+		return buf, nil
+	}
+	return nil, errors.New("cannot find " + name + " in tzdata file " + file)
+}

src/time/zoneinfo_read.go

@@ -220,6 +220,18 @@ func newLocationFromTzinfo(name string, Tzinfo []byte) (*Location, error) {
 	return l, nil
 }
 
+// loadTzinfoFromDirOrZip returns the contents of the file with the given name
+// in dir. dir can either be an uncompressed zip file, or a directory.
+func loadTzinfoFromDirOrZip(dir, name string) ([]byte, error) {
+	if len(dir) > 4 && dir[len(dir)-4:] == ".zip" {
+		return loadTzinfoFromZip(dir, name)
+	}
+	if dir != "" {
+		name = dir + "/" + name
+	}
+	return readFile(name)
+}
+
 // There are 500+ zoneinfo files. Rather than distribute them all
 // individually, we ship them in an uncompressed zip file.
 // Used this way, the zip file format serves as a commonly readable
@@ -351,61 +363,13 @@ func loadTzinfoFromZip(zipfile, name string) ([]byte, error) {
 		return buf, nil
 	}
 
-	return nil, syscall.ENOENT
+	return nil, errors.New("cannot find " + name + " in zip file " + zipfile)
 }
 
 // loadTzinfoFromTzdata returns the time zone information of the time zone
 // with the given name, from a tzdata database file as they are typically
 // found on android.
-func loadTzinfoFromTzdata(file, name string) ([]byte, error) {
-	const (
-		headersize = 12 + 3*4
-		namesize   = 40
-		entrysize  = namesize + 3*4
-	)
-	if len(name) > namesize {
-		return nil, errors.New(name + " is longer than the maximum zone name length (40 bytes)")
-	}
-	fd, err := open(file)
-	if err != nil {
-		return nil, err
-	}
-	defer closefd(fd)
-
-	buf := make([]byte, headersize)
-	if err := preadn(fd, buf, 0); err != nil {
-		return nil, errors.New("corrupt tzdata file " + file)
-	}
-	d := data{buf, false}
-	if magic := d.read(6); string(magic) != "tzdata" {
-		return nil, errors.New("corrupt tzdata file " + file)
-	}
-	d = data{buf[12:], false}
-	indexOff, _ := d.big4()
-	dataOff, _ := d.big4()
-	indexSize := dataOff - indexOff
-	entrycount := indexSize / entrysize
-	buf = make([]byte, indexSize)
-	if err := preadn(fd, buf, int(indexOff)); err != nil {
-		return nil, errors.New("corrupt tzdata file " + file)
-	}
-	for i := 0; i < int(entrycount); i++ {
-		entry := buf[i*entrysize : (i+1)*entrysize]
-		// len(name) <= namesize is checked at function entry
-		if string(entry[:len(name)]) != name {
-			continue
-		}
-		d := data{entry[namesize:], false}
-		off, _ := d.big4()
-		size, _ := d.big4()
-		buf := make([]byte, size)
-		if err := preadn(fd, buf, int(off+dataOff)); err != nil {
-			return nil, errors.New("corrupt tzdata file " + file)
-		}
-		return buf, nil
-	}
-	return nil, syscall.ENOENT
-}
+var loadTzinfoFromTzdata func(file, name string) ([]byte, error)
 
 // loadTzinfo returns the time zone information of the time zone
 // with the given name, from a given source. A source may be a
@@ -414,13 +378,8 @@ func loadTzinfoFromTzdata(file, name string) ([]byte, error) {
 func loadTzinfo(name string, source string) ([]byte, error) {
 	if len(source) >= 6 && source[len(source)-6:] == "tzdata" {
 		return loadTzinfoFromTzdata(source, name)
-	} else if len(source) > 4 && source[len(source)-4:] == ".zip" {
-		return loadTzinfoFromZip(source, name)
 	}
-	if source != "" {
-		name = source + "/" + name
-	}
-	return readFile(name)
+	return loadTzinfoFromDirOrZip(source, name)
 }
 
 // loadLocation returns the Location with the given name from one of