syscall: implement windows version of Fsync

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/4158043

src/pkg/syscall/syscall_windows.go

@@ -158,6 +158,7 @@ func NewCallback(fn interface{}) uintptr
 //sys	CommandLineToArgv(cmd *uint16, argc *int32) (argv *[8192]*[8192]uint16, errno int) [failretval==nil] = shell32.CommandLineToArgvW
 //sys	LocalFree(hmem uint32) (handle uint32, errno int) [failretval!=0]
 //sys	SetHandleInformation(handle int32, mask uint32, flags uint32) (ok bool, errno int)
+//sys	FlushFileBuffers(handle int32) (ok bool, errno int)
 
 // syscall interface implementation for other packages
 
@@ -478,6 +479,13 @@ func Utimes(path string, tv []Timeval) (errno int) {
 	return 0
 }
 
+func Fsync(fd int) (errno int) {
+	if ok, e := FlushFileBuffers(int32(fd)); !ok {
+		return e
+	}
+	return 0
+}
+
 // net api calls
 
 //sys	WSAStartup(verreq uint32, data *WSAData) (sockerrno int) = wsock32.WSAStartup
@@ -732,9 +740,6 @@ func Chown(path string, uid int, gid int) (errno int)     { return EWINDOWS }
 func Lchown(path string, uid int, gid int) (errno int)    { return EWINDOWS }
 func Fchown(fd int, uid int, gid int) (errno int)         { return EWINDOWS }
 
-// TODO(brainman): use FlushFileBuffers Windows api to implement Fsync.
-func Fsync(fd int) (errno int) { return EWINDOWS }
-
 func Getuid() (uid int)                  { return -1 }
 func Geteuid() (euid int)                { return -1 }
 func Getgid() (gid int)                  { return -1 }

src/pkg/syscall/zsyscall_windows_386.go

@@ -67,6 +67,7 @@ var (
 	procCommandLineToArgvW         = getSysProcAddr(modshell32, "CommandLineToArgvW")
 	procLocalFree                  = getSysProcAddr(modkernel32, "LocalFree")
 	procSetHandleInformation       = getSysProcAddr(modkernel32, "SetHandleInformation")
+	procFlushFileBuffers           = getSysProcAddr(modkernel32, "FlushFileBuffers")
 	procWSAStartup                 = getSysProcAddr(modwsock32, "WSAStartup")
 	procWSACleanup                 = getSysProcAddr(modwsock32, "WSACleanup")
 	procsocket                     = getSysProcAddr(modwsock32, "socket")
@@ -883,6 +884,21 @@ func SetHandleInformation(handle int32, mask uint32, flags uint32) (ok bool, err
 	return
 }
 
+func FlushFileBuffers(handle int32) (ok bool, errno int) {
+	r0, _, e1 := Syscall(procFlushFileBuffers, 1, uintptr(handle), 0, 0)
+	ok = bool(r0 != 0)
+	if !ok {
+		if e1 != 0 {
+			errno = int(e1)
+		} else {
+			errno = EINVAL
+		}
+	} else {
+		errno = 0
+	}
+	return
+}
+
 func WSAStartup(verreq uint32, data *WSAData) (sockerrno int) {
 	r0, _, _ := Syscall(procWSAStartup, 2, uintptr(verreq), uintptr(unsafe.Pointer(data)), 0)
 	sockerrno = int(r0)