Specialize the conversion between wchar_t* and Go string on Windows o…

…nly.

wchar.go

@@ -21,6 +21,8 @@
 // OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 // SUCH DAMAGE.
 
+//go:build !windows
+
 package hid
 
 /*

wchar_windows.go

@@ -0,0 +1,29 @@
+package hid
+
+/*
+#include <wchar.h>
+*/
+import "C"
+
+import (
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+// gotowcs converts a Go string to a C wide string. The returned string must
+// be freed by the caller by calling C.free.
+func gotowcs(s string) *C.wchar_t {
+	u16s, err := windows.UTF16FromString(s)
+	if err != nil {
+		panic(err)
+	}
+	n := C.size_t(len(u16s))
+	wcs := (*C.wchar_t)(calloc(n+1, C.sizeof_wchar_t))
+	return C.wmemcpy(wcs, (*C.wchar_t)(unsafe.Pointer(&u16s[0])), n)
+}
+
+// wcstogo converts a C wide string to a Go string.
+func wcstogo(wcs *C.wchar_t) string {
+	return windows.UTF16PtrToString((*uint16)(unsafe.Pointer(wcs)))
+}