unix: add Getdents on dragonfly

Add a syscall wrapper for Getdents on dragonfly and use it to
implement ReadDirent

Change-Id: Ie54c0edeaf89491cab2355557fb442bd5bec2987
Reviewed-on: https://go-review.googlesource.com/c/sys/+/183227
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Benny Siegert <bsiegert@gmail.com>

unix/readdirent_getdents.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build aix freebsd linux netbsd openbsd
+// +build aix dragonfly freebsd linux netbsd openbsd
 
 package unix
 

unix/readdirent_getdirentries.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin dragonfly
+// +build darwin
 
 package unix
 

unix/syscall_dragonfly.go

@@ -269,6 +269,7 @@ func Sendfile(outfd int, infd int, offset *int64, count int) (written int, err e
 //sys	Fstatfs(fd int, stat *Statfs_t) (err error)
 //sys	Fsync(fd int) (err error)
 //sys	Ftruncate(fd int, length int64) (err error)
+//sys	Getdents(fd int, buf []byte) (n int, err error)
 //sys	Getdirentries(fd int, buf []byte, basep *uintptr) (n int, err error)
 //sys	Getdtablesize() (size int)
 //sysnb	Getegid() (egid int)

unix/zsyscall_dragonfly_amd64.go

@@ -749,6 +749,23 @@ func Ftruncate(fd int, length int64) (err error) {
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
+func Getdents(fd int, buf []byte) (n int, err error) {
+	var _p0 unsafe.Pointer
+	if len(buf) > 0 {
+		_p0 = unsafe.Pointer(&buf[0])
+	} else {
+		_p0 = unsafe.Pointer(&_zero)
+	}
+	r0, _, e1 := Syscall(SYS_GETDENTS, uintptr(fd), uintptr(_p0), uintptr(len(buf)))
+	n = int(r0)
+	if e1 != 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
 func Getdirentries(fd int, buf []byte, basep *uintptr) (n int, err error) {
 	var _p0 unsafe.Pointer
 	if len(buf) > 0 {