Refactor pkg/archive with a platform-independent stat struct

pkg/archive contains code both invoked from cli (cross platform) and
daemon (linux only) and Unix-specific dependencies break compilation on
Windows. We extracted those stat-related funcs into platform specific
implementations at pkg/system and added unit tests.

Signed-off-by: Ahmet Alp Balkan <ahmetb@microsoft.com>

system/lstat.go

@@ -6,11 +6,11 @@ import (
 	"syscall"
 )
 
-func Lstat(path string) (*syscall.Stat_t, error) {
+func Lstat(path string) (*Stat, error) {
 	s := &syscall.Stat_t{}
 	err := syscall.Lstat(path, s)
 	if err != nil {
 		return nil, err
 	}
-	return s, nil
+	return fromStatT(s)
 }

system/lstat_test.go

@@ -0,0 +1,25 @@
+package system
+
+import (
+	"testing"
+)
+
+func TestLstat(t *testing.T) {
+	file, invalid, _ := prepareFiles(t)
+
+	statFile, err := Lstat(file)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if statFile == nil {
+		t.Fatal("returned empty stat for existing file")
+	}
+
+	statInvalid, err := Lstat(invalid)
+	if err == nil {
+		t.Fatal("did not return error for non-existing file")
+	}
+	if statInvalid != nil {
+		t.Fatal("returned non-nil stat for non-existing file")
+	}
+}

system/lstat_windows.go

@@ -2,11 +2,7 @@
 
 package system
 
-import (
-	"syscall"
-)
-
-func Lstat(path string) (*syscall.Win32FileAttributeData, error) {
+func Lstat(path string) (*Stat, error) {
 	// should not be called on cli code path
 	return nil, ErrNotSupportedPlatform
 }

system/stat.go

@@ -0,0 +1,42 @@
+package system
+
+import (
+	"syscall"
+)
+
+type Stat struct {
+	mode uint32
+	uid  uint32
+	gid  uint32
+	rdev uint64
+	size int64
+	mtim syscall.Timespec
+}
+
+func (s Stat) Mode() uint32 {
+	return s.mode
+}
+
+func (s Stat) Uid() uint32 {
+	return s.uid
+}
+
+func (s Stat) Gid() uint32 {
+	return s.gid
+}
+
+func (s Stat) Rdev() uint64 {
+	return s.rdev
+}
+
+func (s Stat) Size() int64 {
+	return s.size
+}
+
+func (s Stat) Mtim() syscall.Timespec {
+	return s.mtim
+}
+
+func (s Stat) GetLastModification() syscall.Timespec {
+	return s.Mtim()
+}

system/stat_linux.go

@@ -4,10 +4,11 @@ import (
 	"syscall"
 )
 
-func GetLastAccess(stat *syscall.Stat_t) syscall.Timespec {
-	return stat.Atim
-}
-
-func GetLastModification(stat *syscall.Stat_t) syscall.Timespec {
-	return stat.Mtim
+func fromStatT(s *syscall.Stat_t) (*Stat, error) {
+	return &Stat{size: s.Size,
+		mode: s.Mode,
+		uid:  s.Uid,
+		gid:  s.Gid,
+		rdev: s.Rdev,
+		mtim: s.Mtim}, nil
 }

system/stat_test.go

@@ -0,0 +1,34 @@
+package system
+
+import (
+	"syscall"
+	"testing"
+)
+
+func TestFromStatT(t *testing.T) {
+	file, _, _ := prepareFiles(t)
+
+	stat := &syscall.Stat_t{}
+	err := syscall.Lstat(file, stat)
+
+	s, err := fromStatT(stat)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if stat.Mode != s.Mode() {
+		t.Fatal("got invalid mode")
+	}
+	if stat.Uid != s.Uid() {
+		t.Fatal("got invalid uid")
+	}
+	if stat.Gid != s.Gid() {
+		t.Fatal("got invalid gid")
+	}
+	if stat.Rdev != s.Rdev() {
+		t.Fatal("got invalid rdev")
+	}
+	if stat.Mtim != s.Mtim() {
+		t.Fatal("got invalid mtim")
+	}
+}

system/stat_unsupported.go

@@ -1,13 +1,16 @@
-// +build !linux
+// +build !linux,!windows
 
 package system
 
-import "syscall"
+import (
+	"syscall"
+)
 
-func GetLastAccess(stat *syscall.Stat_t) syscall.Timespec {
-	return stat.Atimespec
-}
-
-func GetLastModification(stat *syscall.Stat_t) syscall.Timespec {
-	return stat.Mtimespec
+func fromStatT(s *syscall.Stat_t) (*Stat, error) {
+	return &Stat{size: s.Size,
+		mode: uint32(s.Mode),
+		uid:  s.Uid,
+		gid:  s.Gid,
+		rdev: uint64(s.Rdev),
+		mtim: s.Mtimespec}, nil
 }

system/stat_windows.go

@@ -0,0 +1,12 @@
+// +build windows
+
+package system
+
+import (
+	"errors"
+	"syscall"
+)
+
+func fromStatT(s *syscall.Win32FileAttributeData) (*Stat, error) {
+	return nil, errors.New("fromStatT should not be called on windows path")
+}