Specialize conversion between wchar_t* and string on Windows (#7)

wchar.go

@@ -21,6 +21,9 @@
 // OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 // SUCH DAMAGE.
 
+// Except for Windows. See wchar_windows.go for detail.
+//go:build !windows
+
 package hid
 
 /*

wchar_windows.go

@@ -0,0 +1,59 @@
+// Copyright (c) 2023 Steven Stallion <sstallion@gmail.com>
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions
+// are met:
+// 1. Redistributions of source code must retain the above copyright
+//    notice, this list of conditions and the following disclaimer.
+// 2. Redistributions in binary form must reproduce the above copyright
+//    notice, this list of conditions and the following disclaimer in the
+//    documentation and/or other materials provided with the distribution.
+//
+// THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND
+// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+// ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+// OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+// OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+// SUCH DAMAGE.
+
+package hid
+
+// Replace C.mbstowcs() and C.wcstombs() for Windows only.  Those functions
+// don't work on some characters of MBCS (Chinese, Japanese, Korean, or so)
+// because of code pages, encoding, C runtime, and the compiler used by CGO.
+//
+// See the following links for background:
+//
+//   - https://github.com/sstallion/go-hid/pull/7
+//   - https://github.com/sstallion/go-hid/issues/6
+
+/*
+#include <wchar.h>
+*/
+import "C"
+
+import (
+	"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)(&u16s[0]), n)
+}
+
+// wcstogo converts a C wide string to a Go string.
+func wcstogo(wcs *C.wchar_t) string {
+	return windows.UTF16PtrToString((*uint16)(wcs))
+}