keywords: correctly handle time keywords

Previously, the time generation code would inexplicably drop parts of
the nanotime -- potentially causing validation to succeed when it should
fail. This was probably do to a bug in the remainder logic, but instead
we should be using .Nanosecond() anyway.

After changing the time of a file with a test case like this:

    // Change the time to something known with nanosec != 0.
    chtime := time.Unix(100, 987654321)
    if err := os.Chtimes("somefile", chtime, chtime); err != nil {
	// panic
    }

timeKeywordFunc() would return the wrong value (time=100.000000021).
This fixes the issue and adds a test case.

Signed-off-by: Aleksa Sarai <asarai@suse.de>

keywords.go

@@ -287,14 +287,12 @@ var (
 		}
 	}
 	tartimeKeywordFunc = func(path string, info os.FileInfo, r io.Reader) (string, error) {
-		return fmt.Sprintf("tar_time=%d.000000000", info.ModTime().Unix()), nil
+		return fmt.Sprintf("tar_time=%d.%9.9d", info.ModTime().Unix(), 0), nil
 	}
 	timeKeywordFunc = func(path string, info os.FileInfo, r io.Reader) (string, error) {
-		t := info.ModTime().UnixNano()
-		if t == 0 {
-			return "time=0.000000000", nil
-		}
-		return fmt.Sprintf("time=%d.%9.9d", (t / 1e9), (t % (t / 1e9))), nil
+		tSec := info.ModTime().Unix()
+		tNano := info.ModTime().Nanosecond()
+		return fmt.Sprintf("time=%d.%9.9d", tSec, tNano), nil
 	}
 	linkKeywordFunc = func(path string, info os.FileInfo, r io.Reader) (string, error) {
 		if sys, ok := info.Sys().(*tar.Header); ok {

keywords_test.go

@@ -0,0 +1,95 @@
+package mtree
+
+import (
+	"fmt"
+	"os"
+	"testing"
+	"time"
+)
+
+type fakeFileInfo struct {
+	mtime time.Time
+}
+
+func (ffi fakeFileInfo) Name() string {
+	// noop
+	return ""
+}
+
+func (ffi fakeFileInfo) Size() int64 {
+	// noop
+	return -1
+}
+
+func (ffi fakeFileInfo) Mode() os.FileMode {
+	// noop
+	return 0
+}
+
+func (ffi fakeFileInfo) ModTime() time.Time {
+	return ffi.mtime
+}
+
+func (ffi fakeFileInfo) IsDir() bool {
+	return ffi.Mode().IsDir()
+}
+
+func (ffi fakeFileInfo) Sys() interface{} {
+	// noop
+	return nil
+}
+
+func TestKeywordsTimeNano(t *testing.T) {
+	// We have to make sure that timeKeywordFunc always returns the correct
+	// formatting with regards to the nanotime.
+
+	for _, test := range []struct {
+		sec, nsec int64
+	}{
+		{1234, 123456789},
+		{5555, 987654321},
+		{1337, 100000000},
+		{8888, 999999999},
+		{144123582122, 1},
+		{857125628319, 0},
+	} {
+		mtime := time.Unix(test.sec, test.nsec)
+		expected := fmt.Sprintf("time=%d.%9.9d", test.sec, test.nsec)
+		got, err := timeKeywordFunc("", fakeFileInfo{
+			mtime: mtime,
+		}, nil)
+		if err != nil {
+			t.Errorf("unexpected error while parsing '%q': %q", mtime, err)
+		}
+		if expected != got {
+			t.Errorf("keyword didn't match, expected '%s' got '%s'", expected, got)
+		}
+	}
+}
+
+func TestKeywordsTimeTar(t *testing.T) {
+	// tartimeKeywordFunc always has nsec = 0.
+
+	for _, test := range []struct {
+		sec, nsec int64
+	}{
+		{1234, 123456789},
+		{5555, 987654321},
+		{1337, 100000000},
+		{8888, 999999999},
+		{144123582122, 1},
+		{857125628319, 0},
+	} {
+		mtime := time.Unix(test.sec, test.nsec)
+		expected := fmt.Sprintf("tar_time=%d.%9.9d", test.sec, 0)
+		got, err := tartimeKeywordFunc("", fakeFileInfo{
+			mtime: mtime,
+		}, nil)
+		if err != nil {
+			t.Errorf("unexpected error while parsing '%q': %q", mtime, err)
+		}
+		if expected != got {
+			t.Errorf("keyword didn't match, expected '%s' got '%s'", expected, got)
+		}
+	}
+}