1 files changed, 68 insertions, 0 deletions
diff --git a/include/comphelper/windowserrorstring.hxx b/include/comphelper/windowserrorstring.hxx
new file mode 100644
index 000000000..1b50f1ead
--- /dev/null
+++ b/include/comphelper/windowserrorstring.hxx
@@ -0,0 +1,68 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_COMPHELPER_WINDOWSERRORSTRING_HXX
+#define INCLUDED_COMPHELPER_WINDOWSERRORSTRING_HXX
+
+#include <prewin.h>
+#include <postwin.h>
+#include <rtl/ustring.hxx>
+#include <o3tl/char16_t2wchar_t.hxx>
+
+namespace {
+
+inline OUString WindowsErrorString(DWORD nErrorCode)
+{
+    LPWSTR pMsgBuf;
+
+    if (FormatMessageW(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
+                       nullptr,
+                       nErrorCode,
+                       MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+                       reinterpret_cast<LPWSTR>(&pMsgBuf),
+                       0,
+                       nullptr) == 0)
+        return OUString::number(nErrorCode, 16);
+
+    OUString result(o3tl::toU(pMsgBuf));
+    result.endsWith("\r\n", &result);
+
+    HeapFree(GetProcessHeap(), 0, pMsgBuf);
+
+    return result;
+}
+
+inline OUString WindowsErrorStringFromHRESULT(HRESULT hr)
+{
+    // See https://blogs.msdn.microsoft.com/oldnewthing/20061103-07/?p=29133
+    // Also https://social.msdn.microsoft.com/Forums/vstudio/en-US/c33d9a4a-1077-4efd-99e8-0c222743d2f8
+    // (which refers to https://msdn.microsoft.com/en-us/library/aa382475)
+    // explains why can't we just reinterpret_cast HRESULT to DWORD Win32 error:
+    // we might actually have a Win32 error code converted using HRESULT_FROM_WIN32 macro
+
+    DWORD nErrorCode = DWORD(hr);
+    if (HRESULT(hr & 0xFFFF0000) == MAKE_HRESULT(SEVERITY_ERROR, FACILITY_WIN32, 0) || hr == S_OK)
+    {
+        nErrorCode = HRESULT_CODE(hr);
+        // https://msdn.microsoft.com/en-us/library/ms679360 mentions that the codes might have
+        // high word bits set (e.g., bit 29 could be set if error comes from a 3rd-party library).
+        // So try to restore the original error code to avoid wrong error messages
+        DWORD nLastError = GetLastError();
+        if ((nLastError & 0xFFFF) == nErrorCode)
+            nErrorCode = nLastError;
+    }
+
+    return WindowsErrorString(nErrorCode);
+}
+
+} // anonymous namespace
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */