Adds IsDir and Seek to platform.File (#1441)

Signed-off-by: Adrian Cole <adrian@tetrate.io>

internal/sys/fs.go

@@ -214,6 +214,11 @@ func (r *lazyDir) AccessMode() int {
 	return syscall.O_RDONLY
 }
 
+// IsDir implements the same method as documented on platform.File
+func (r *lazyDir) IsDir() (bool, syscall.Errno) {
+	return true, 0
+}
+
 // Stat implements the same method as documented on platform.File
 func (r *lazyDir) Stat() (platform.Stat_t, syscall.Errno) {
 	if f, ok := r.file(); !ok {
@@ -233,6 +238,11 @@ func (r *lazyDir) Pread([]byte, int64) (int, syscall.Errno) {
 	return 0, syscall.EISDIR
 }
 
+// Seek implements File.Seek
+func (r *lazyDir) Seek(int64, int) (int64, syscall.Errno) {
+	return 0, syscall.EISDIR
+}
+
 // Write implements the same method as documented on platform.File
 func (r *lazyDir) Write([]byte) (int, syscall.Errno) {
 	return 0, syscall.EBADF
@@ -359,20 +369,17 @@ type FileEntry struct {
 type cachedStat struct {
 	// Ino is the file serial number, or zero if not available.
 	Ino uint64
-
-	// Type is the same as what's documented on platform.Dirent.
-	Type fs.FileMode
 }
 
-// CachedStat returns the cacheable parts of platform.Stat_t or an error if
-// they couldn't be retrieved.
-func (f *FileEntry) CachedStat() (ino uint64, fileType fs.FileMode, errno syscall.Errno) {
+// Inode returns the cached inode from of platform.Stat_t or an error if it
+// couldn't be retrieved.
+func (f *FileEntry) Inode() (ino uint64, errno syscall.Errno) {
 	if f.cachedStat == nil {
 		if _, errno = f.Stat(); errno != 0 {
 			return
 		}
 	}
-	return f.cachedStat.Ino, f.cachedStat.Type, 0
+	return f.cachedStat.Ino, 0
 }
 
 // Stat returns the underlying stat of this file.
@@ -387,7 +394,7 @@ func (f *FileEntry) Stat() (st platform.Stat_t, errno syscall.Errno) {
 	}
 
 	if errno == 0 {
-		f.cachedStat = &cachedStat{Ino: st.Ino, Type: st.Mode & fs.ModeType}
+		f.cachedStat = &cachedStat{Ino: st.Ino}
 	}
 	return
 }
@@ -547,10 +554,10 @@ func (c *FSContext) ReOpenDir(fd int32) (*FileEntry, syscall.Errno) {
 	f, ok := c.openedFiles.Lookup(fd)
 	if !ok {
 		return nil, syscall.EBADF
-	} else if _, ft, errno := f.CachedStat(); errno != 0 {
+	} else if isDir, errno := f.File.IsDir(); errno != 0 {
 		return nil, errno
-	} else if ft.Type() != fs.ModeDir {
-		return nil, syscall.EISDIR
+	} else if !isDir {
+		return nil, syscall.ENOTDIR
 	}
 
 	if errno := c.reopen(f); errno != 0 {
@@ -583,9 +590,9 @@ func (c *FSContext) ChangeOpenFlag(fd int32, flag int) syscall.Errno {
 	f, ok := c.LookupFile(fd)
 	if !ok {
 		return syscall.EBADF
-	} else if _, ft, errno := f.CachedStat(); errno != 0 {
+	} else if isDir, errno := f.File.IsDir(); errno != 0 {
 		return errno
-	} else if ft.Type() == fs.ModeDir {
+	} else if isDir {
 		return syscall.EISDIR
 	}
 

internal/sys/fs_test.go

@@ -87,7 +87,7 @@ func TestNewFSContext(t *testing.T) {
 			// test to ensure that our implementation properly reuses descriptor
 			// numbers but if we were to change the reuse strategy, this test
 			// would likely break and need to be updated.
-			require.Zero(t, fsc.CloseFile(f1))
+			require.EqualErrno(t, 0, fsc.CloseFile(f1))
 			f2, errno := fsc.OpenFile(preopenedDir.FS, preopenedDir.Name, 0, 0)
 			require.EqualErrno(t, 0, errno)
 			require.Equal(t, f1, f2)
@@ -113,7 +113,7 @@ func TestFSContext_CloseFile(t *testing.T) {
 	require.EqualErrno(t, 0, errno)
 
 	// Close
-	require.Zero(t, fsc.CloseFile(fdToClose))
+	require.EqualErrno(t, 0, fsc.CloseFile(fdToClose))
 
 	// Verify fdToClose is closed and removed from the opened FDs.
 	_, ok := fsc.LookupFile(fdToClose)
@@ -127,7 +127,7 @@ func TestFSContext_CloseFile(t *testing.T) {
 		require.EqualErrno(t, syscall.EBADF, fsc.CloseFile(42)) // 42 is an arbitrary invalid FD
 	})
 	t.Run("Can close a pre-open", func(t *testing.T) {
-		require.Zero(t, fsc.CloseFile(FdPreopen))
+		require.EqualErrno(t, 0, fsc.CloseFile(FdPreopen))
 	})
 }
 
@@ -275,7 +275,7 @@ func TestFSContext_ReOpenDir(t *testing.T) {
 		require.EqualErrno(t, 0, errno)
 
 		_, errno = fsc.ReOpenDir(fd)
-		require.EqualErrno(t, syscall.EISDIR, errno)
+		require.EqualErrno(t, syscall.ENOTDIR, errno)
 	})
 }
 
@@ -301,7 +301,7 @@ func TestFSContext_Renumber(t *testing.T) {
 		prevDirFile, ok := fsc.LookupFile(fromFd)
 		require.True(t, ok)
 
-		require.Zero(t, fsc.Renumber(fromFd, toFd))
+		require.EqualErrno(t, 0, fsc.Renumber(fromFd, toFd))
 
 		renumberedDirFile, ok := fsc.LookupFile(toFd)
 		require.True(t, ok)
@@ -355,13 +355,13 @@ func TestFSContext_ChangeOpenFlag(t *testing.T) {
 	require.Equal(t, f0.openFlag&syscall.O_APPEND, 0)
 
 	// Set the APPEND flag.
-	require.Zero(t, fsc.ChangeOpenFlag(fd, syscall.O_APPEND))
+	require.EqualErrno(t, 0, fsc.ChangeOpenFlag(fd, syscall.O_APPEND))
 	f1, ok := fsc.openedFiles.Lookup(fd)
 	require.True(t, ok)
 	require.Equal(t, f1.openFlag&syscall.O_APPEND, syscall.O_APPEND)
 
 	// Remove the APPEND flag.
-	require.Zero(t, fsc.ChangeOpenFlag(fd, 0))
+	require.EqualErrno(t, 0, fsc.ChangeOpenFlag(fd, 0))
 	f2, ok := fsc.openedFiles.Lookup(fd)
 	require.True(t, ok)
 	require.Equal(t, f2.openFlag&syscall.O_APPEND, 0)

internal/sys/sys_test.go

@@ -2,7 +2,6 @@ package sys
 
 import (
 	"bytes"
-	"io/fs"
 	"runtime"
 	"strings"
 	"testing"
@@ -67,7 +66,7 @@ func TestDefaultSysContext(t *testing.T) {
 	require.Equal(t, expectedOpenedFiles, sysCtx.FS().openedFiles)
 }
 
-func TestFileEntry_cachedStat(t *testing.T) {
+func TestFileEntryInode(t *testing.T) {
 	t.Parallel()
 
 	tmpDir := t.TempDir()
@@ -98,14 +97,13 @@ func TestFileEntry_cachedStat(t *testing.T) {
 
 			f, ok := fsc.LookupFile(FdPreopen)
 			require.True(t, ok)
-			ino, ft, errno := f.CachedStat()
+			ino, errno := f.Inode()
 			require.EqualErrno(t, 0, errno)
-			require.Equal(t, fs.ModeDir, ft)
 			if !canReadDirInode() {
 				tc.expectedIno = 0
 			}
 			require.Equal(t, tc.expectedIno, ino)
-			require.Equal(t, &cachedStat{Ino: tc.expectedIno, Type: fs.ModeDir}, f.cachedStat)
+			require.Equal(t, &cachedStat{Ino: tc.expectedIno}, f.cachedStat)
 		})
 	}
 }