os: fix Readdir in Plan 9

'TestReaddir.*' tests now passes.

R=golang-dev, lucio, r
CC=golang-dev
https://golang.org/cl/4381048

src/pkg/os/dir_plan9.go

@@ -8,72 +8,56 @@ import (
 	"syscall"
 )
 
-type dirInfo int
-
-var markDirectory dirInfo = ^0
-
 // Readdir reads the contents of the directory associated with file and
-// returns an array of up to count FileInfo structures, as would be returned
-// by Lstat, in directory order.  Subsequent calls on the same file will yield
-// further FileInfos. A negative count means to read the entire directory.
+// returns an array of up to count FileInfo structures, in directory order. 
+// Subsequent calls on the same file will yield further FileInfos.
+// A negative count means to read until EOF.
 // Readdir returns the array and an Error, if any.
 func (file *File) Readdir(count int) (fi []FileInfo, err Error) {
 	// If this file has no dirinfo, create one.
 	if file.dirinfo == nil {
-		file.dirinfo = &markDirectory
+		file.dirinfo = new(dirInfo)
 	}
-
+	d := file.dirinfo
 	size := count
 	if size < 0 {
 		size = 100
 	}
-
-	result := make([]FileInfo, 0, size)
-	var buf [syscall.STATMAX]byte
-
-	for {
-		n, e := file.Read(buf[:])
-
-		if e != nil {
+	result := make([]FileInfo, 0, size) // Empty with room to grow.
+	for count != 0 {
+		// Refill the buffer if necessary
+		if d.bufp >= d.nbuf {
+			d.bufp = 0
+			var e Error
+			d.nbuf, e = file.Read(d.buf[:])
+			if e != nil && e != EOF {
+				return nil, &PathError{"readdir", file.name, e}
+			}
 			if e == EOF {
 				break
 			}
-
-			return []FileInfo{}, &PathError{"readdir", file.name, e}
+			if d.nbuf < syscall.STATFIXLEN {
+				return nil, &PathError{"readdir", file.name, Eshortstat}
+			}
 		}
 
-		if n < syscall.STATFIXLEN {
-			return []FileInfo{}, &PathError{"readdir", file.name, Eshortstat}
-		}
-
-		for i := 0; i < n; {
-			m, _ := gbit16(buf[i:])
+		// Get a record from buffer
+		m, _ := gbit16(d.buf[d.bufp:])
 		m += 2
-
 		if m < syscall.STATFIXLEN {
-				return []FileInfo{}, &PathError{"readdir", file.name, Eshortstat}
+			return nil, &PathError{"readdir", file.name, Eshortstat}
 		}
-
-			d, e := UnmarshalDir(buf[i : i+int(m)])
-
+		dir, e := UnmarshalDir(d.buf[d.bufp : d.bufp+int(m)])
 		if e != nil {
-				return []FileInfo{}, &PathError{"readdir", file.name, e}
+			return nil, &PathError{"readdir", file.name, e}
 		}
-
 		var f FileInfo
-			fileInfoFromStat(&f, d)
-
+		fileInfoFromStat(&f, dir)
 		result = append(result, f)
 
-			// a negative count means to read until EOF.
-			if count > 0 && len(result) >= count {
-				break
+		d.bufp += int(m)
+		count--
 	}
-
-			i += int(m)
-		}
-	}
-
 	return result, nil
 }
 

src/pkg/os/error_plan9.go

@@ -37,12 +37,15 @@ var (
 	Enonexist  = NewError("file does not exist")
 	Eexist     = NewError("file already exists")
 	Eio        = NewError("i/o error")
+	Eperm      = NewError("permission denied")
 
 	EINVAL  = Ebadarg
 	ENOTDIR = Enotdir
 	ENOENT  = Enonexist
 	EEXIST  = Eexist
 	EIO     = Eio
+	EACCES  = Eperm
+	EISDIR  = syscall.EISDIR
 
 	ENAMETOOLONG = NewError("file name too long")
 	ERANGE       = NewError("math result not representable")

src/pkg/os/file_plan9.go

@@ -9,6 +9,13 @@ import (
 	"syscall"
 )
 
+// Auxiliary information if the File describes a directory
+type dirInfo struct {
+	buf  [syscall.STATMAX]byte // buffer for directory I/O
+	nbuf int                   // length of buf; return value from Read
+	bufp int                   // location of next record in buf.
+}
+
 func epipecheck(file *File, e syscall.Error) {
 }
 

src/pkg/os/os_test.go

@@ -45,6 +45,14 @@ var sysdir = func() (sd *sysDir) {
 				"services",
 			},
 		}
+	case "plan9":
+		sd = &sysDir{
+			"/lib/ndb",
+			[]string{
+				"common",
+				"local",
+			},
+		}
 	default:
 		sd = &sysDir{
 			"/etc",
@@ -245,8 +253,11 @@ func smallReaddirnames(file *File, length int, t *testing.T) []string {
 func TestReaddirnamesOneAtATime(t *testing.T) {
 	// big directory that doesn't change often.
 	dir := "/usr/bin"
-	if syscall.OS == "windows" {
+	switch syscall.OS {
+	case "windows":
 		dir = Getenv("SystemRoot") + "\\system32"
+	case "plan9":
+		dir = "/bin"
 	}
 	file, err := Open(dir)
 	defer file.Close()
@@ -262,6 +273,9 @@ func TestReaddirnamesOneAtATime(t *testing.T) {
 		t.Fatalf("open %q failed: %v", dir, err2)
 	}
 	small := smallReaddirnames(file1, len(all)+100, t) // +100 in case we screw up
+	if len(small) < len(all) {
+		t.Fatalf("len(small) is %d, less than %d", len(small), len(all))
+	}
 	for i, n := range all {
 		if small[i] != n {
 			t.Errorf("small read %q mismatch: %v", small[i], n)