archive/zip: support functions to get modified time in ns from MS-DOS time

R=rsc, r, bradfitz, r, adg
CC=golang-dev
https://golang.org/cl/4748056

src/pkg/archive/zip/reader_test.go

@@ -11,6 +11,7 @@ import (
 	"io/ioutil"
 	"os"
 	"testing"
+	"time"
 )
 
 type ZipTest struct {
@@ -24,8 +25,19 @@ type ZipTestFile struct {
 	Name    string
 	Content []byte // if blank, will attempt to compare against File
 	File    string // name of file to compare to (relative to testdata/)
+	Mtime   string // modified time in format "mm-dd-yy hh:mm:ss"
 }
 
+// Caution: The Mtime values found for the test files should correspond to
+//          the values listed with unzip -l <zipfile>. However, the values
+//          listed by unzip appear to be off by some hours. When creating
+//          fresh test files and testing them, this issue is not present.
+//          The test files were created in Sydney, so there might be a time
+//          zone issue. The time zone information does have to be encoded
+//          somewhere, because otherwise unzip -l could not provide a different
+//          time from what the archive/zip package provides, but there appears
+//          to be no documentation about this.
+
 var tests = []ZipTest{
 	{
 		Name:    "test.zip",
@@ -34,10 +46,12 @@ var tests = []ZipTest{
 			{
 				Name:    "test.txt",
 				Content: []byte("This is a test text file.\n"),
+				Mtime:   "09-05-10 12:12:02",
 			},
 			{
 				Name:  "gophercolor16x16.png",
 				File:  "gophercolor16x16.png",
+				Mtime: "09-05-10 15:52:58",
 			},
 		},
 	},
@@ -47,6 +61,7 @@ var tests = []ZipTest{
 			{
 				Name:  "r/r.zip",
 				File:  "r.zip",
+				Mtime: "03-04-10 00:24:16",
 			},
 		},
 	},
@@ -58,6 +73,7 @@ var tests = []ZipTest{
 			{
 				Name:    "filename",
 				Content: []byte("This is a test textfile.\n"),
+				Mtime:   "02-02-11 13:06:20",
 			},
 		},
 	},
@@ -136,18 +152,30 @@ func readTestFile(t *testing.T, ft ZipTestFile, f *File) {
 	if f.Name != ft.Name {
 		t.Errorf("name=%q, want %q", f.Name, ft.Name)
 	}
+
+	mtime, err := time.Parse("01-02-06 15:04:05", ft.Mtime)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+	if got, want := f.Mtime_ns()/1e9, mtime.Seconds(); got != want {
+		t.Errorf("%s: mtime=%s (%d); want %s (%d)", f.Name, time.SecondsToUTC(got), got, mtime, want)
+	}
+
 	var b bytes.Buffer
 	r, err := f.Open()
 	if err != nil {
 		t.Error(err)
 		return
 	}
+
 	_, err = io.Copy(&b, r)
 	if err != nil {
 		t.Error(err)
 		return
 	}
 	r.Close()
+
 	var c []byte
 	if len(ft.Content) != 0 {
 		c = ft.Content
@@ -155,10 +183,12 @@ func readTestFile(t *testing.T, ft ZipTestFile, f *File) {
 		t.Error(err)
 		return
 	}
+
 	if b.Len() != len(c) {
 		t.Errorf("%s: len=%d, want %d", f.Name, b.Len(), len(c))
 		return
 	}
+
 	for i, b := range b.Bytes() {
 		if b != c[i] {
 			t.Errorf("%s: content[%d]=%q want %q", f.Name, i, b, c[i])

src/pkg/archive/zip/struct.go

@@ -12,6 +12,7 @@ This package does not support ZIP64 or disk spanning.
 package zip
 
 import "os"
+import "time"
 
 // Compression methods.
 const (
@@ -32,8 +33,8 @@ type FileHeader struct {
 	ReaderVersion    uint16
 	Flags            uint16
 	Method           uint16
-	ModifiedTime     uint16
-	ModifiedDate     uint16
+	ModifiedTime     uint16 // MS-DOS time
+	ModifiedDate     uint16 // MS-DOS date
 	CRC32            uint32
 	CompressedSize   uint32
 	UncompressedSize uint32
@@ -61,3 +62,27 @@ func recoverError(err *os.Error) {
 		panic(e)
 	}
 }
+
+// msDosTimeToTime converts an MS-DOS date and time into a time.Time.
+// The resolution is 2s.
+// See: http://msdn.microsoft.com/en-us/library/ms724247(v=VS.85).aspx
+func msDosTimeToTime(dosDate, dosTime uint16) time.Time {
+	return time.Time{
+		// date bits 0-4: day of month; 5-8: month; 9-15: years since 1980
+		Year:  int64(dosDate>>9 + 1980),
+		Month: int(dosDate >> 5 & 0xf),
+		Day:   int(dosDate & 0x1f),
+
+		// time bits 0-4: second/2; 5-10: minute; 11-15: hour
+		Hour:   int(dosTime >> 11),
+		Minute: int(dosTime >> 5 & 0x3f),
+		Second: int(dosTime & 0x1f * 2),
+	}
+}
+
+// Mtime_ns returns the modified time in ns since epoch.
+// The resolution is 2s.
+func (h *FileHeader) Mtime_ns() int64 {
+	t := msDosTimeToTime(h.ModifiedDate, h.ModifiedTime)
+	return t.Seconds() * 1e9
+}