windows: add module handle functions

These are in internal/syscall/windows, but not here, and they're quite
handy to have.

Change-Id: I79fe78d3c6bc2c001f994b03ce575287908d2c59
Reviewed-on: https://go-review.googlesource.com/c/sys/+/199518
Run-TryBot: Jason A. Donenfeld <Jason@zx2c4.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>

windows/syscall_windows.go

@@ -140,6 +140,8 @@ func NewCallbackCDecl(fn interface{}) uintptr {
 //sys	LoadLibraryEx(libname string, zero Handle, flags uintptr) (handle Handle, err error) = LoadLibraryExW
 //sys	FreeLibrary(handle Handle) (err error)
 //sys	GetProcAddress(module Handle, procname string) (proc uintptr, err error)
+//sys	GetModuleFileName(module Handle, filename *uint16, size uint32) (n uint32, err error) = kernel32.GetModuleFileNameW
+//sys	GetModuleHandleEx(flags uint32, moduleName *uint16, module *Handle) (err error) = kernel32.GetModuleHandleExW
 //sys	GetVersion() (ver uint32, err error)
 //sys	FormatMessage(flags uint32, msgsrc uintptr, msgid uint32, langid uint32, buf []uint16, args *byte) (n uint32, err error) = FormatMessageW
 //sys	ExitProcess(exitcode uint32)

windows/types_windows.go

@@ -1735,3 +1735,10 @@ const (
 
 	SHUTDOWN_NORETRY = 0x1
 )
+
+// Flags used for GetModuleHandleEx
+const (
+	GET_MODULE_HANDLE_EX_FLAG_PIN                = 1
+	GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT = 2
+	GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS       = 4
+)

windows/zsyscall_windows.go

@@ -77,6 +77,8 @@ var (
 	procLoadLibraryExW                                       = modkernel32.NewProc("LoadLibraryExW")
 	procFreeLibrary                                          = modkernel32.NewProc("FreeLibrary")
 	procGetProcAddress                                       = modkernel32.NewProc("GetProcAddress")
+	procGetModuleFileNameW                                   = modkernel32.NewProc("GetModuleFileNameW")
+	procGetModuleHandleExW                                   = modkernel32.NewProc("GetModuleHandleExW")
 	procGetVersion                                           = modkernel32.NewProc("GetVersion")
 	procFormatMessageW                                       = modkernel32.NewProc("FormatMessageW")
 	procExitProcess                                          = modkernel32.NewProc("ExitProcess")
@@ -683,6 +685,31 @@ func _GetProcAddress(module Handle, procname *byte) (proc uintptr, err error) {
 	return
 }
 
+func GetModuleFileName(module Handle, filename *uint16, size uint32) (n uint32, err error) {
+	r0, _, e1 := syscall.Syscall(procGetModuleFileNameW.Addr(), 3, uintptr(module), uintptr(unsafe.Pointer(filename)), uintptr(size))
+	n = uint32(r0)
+	if n == 0 {
+		if e1 != 0 {
+			err = errnoErr(e1)
+		} else {
+			err = syscall.EINVAL
+		}
+	}
+	return
+}
+
+func GetModuleHandleEx(flags uint32, moduleName *uint16, module *Handle) (err error) {
+	r1, _, e1 := syscall.Syscall(procGetModuleHandleExW.Addr(), 3, uintptr(flags), uintptr(unsafe.Pointer(moduleName)), uintptr(unsafe.Pointer(module)))
+	if r1 == 0 {
+		if e1 != 0 {
+			err = errnoErr(e1)
+		} else {
+			err = syscall.EINVAL
+		}
+	}
+	return
+}
+
 func GetVersion() (ver uint32, err error) {
 	r0, _, e1 := syscall.Syscall(procGetVersion.Addr(), 0, 0, 0, 0)
 	ver = uint32(r0)