u/windows: Add files and u_winerror string format helper

src/xrt/auxiliary/util/CMakeLists.txt

@@ -110,6 +110,11 @@ target_link_libraries(
 		aux_math
 	)
 
+# Only uses normal Windows libraries, doesn't add anything extra.
+if(WIN32)
+	target_sources(aux_util PRIVATE u_windows.c u_windows.h)
+endif()
+
 # Is basically used everywhere, unavoidable.
 if(XRT_HAVE_SYSTEM_CJSON)
 	target_link_libraries(aux_util PUBLIC cJSON::cJSON)

src/xrt/auxiliary/util/u_windows.c

@@ -0,0 +1,61 @@
+// Copyright 2022, Collabora, Ltd.
+// SPDX-License-Identifier: BSL-1.0
+/*!
+ * @file
+ * @brief  Various helpers for doing Windows specific things.
+ * @author Jakob Bornecrantz <jakob@collabora.com>
+ *
+ * @ingroup aux_os
+ */
+
+#include "xrt/xrt_windows.h"
+#include "util/u_windows.h"
+
+#include "assert.h"
+
+
+/*
+ *
+ * 'Exported' functions.
+ *
+ */
+
+const char *
+u_winerror(char *s, size_t size, DWORD err, bool remove_end)
+{
+	DWORD dSize = (DWORD)size;
+	assert(dSize == size);
+	BOOL bRet;
+
+	bRet = FormatMessageA(          //
+	    FORMAT_MESSAGE_FROM_SYSTEM, //
+	    NULL,                       //
+	    err,                        //
+	    LANG_SYSTEM_DEFAULT,        //
+	    s,                          //
+	    dSize,                      //
+	    NULL);                      //
+	if (!bRet) {
+		s[0] = 0;
+	}
+
+	if (!remove_end) {
+		return s;
+	}
+
+	// Remove newline and period from message.
+	size = strnlen_s(s, size);
+	for (size_t i = size; i-- > 0;) {
+		switch (s[i]) {
+		case '.':
+		case '\n':
+		case '\r': //
+			s[i] = '\0';
+			continue;
+		default: break;
+		}
+		break;
+	}
+
+	return s;
+}

src/xrt/auxiliary/util/u_windows.h

@@ -0,0 +1,37 @@
+// Copyright 2022, Collabora, Ltd.
+// SPDX-License-Identifier: BSL-1.0
+/*!
+ * @file
+ * @brief  Various helpers for doing Windows specific things.
+ * @author Jakob Bornecrantz <jakob@collabora.com>
+ *
+ * @ingroup aux_os
+ */
+
+#pragma once
+
+#include "xrt/xrt_compiler.h"
+#include "xrt/xrt_windows.h"
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+/*!
+ * This function formats a Windows error number, as returned by `GetLastError`,
+ * and writes it into the given buffer.
+ *
+ * @param buffer     Buffer to format the error into.
+ * @param size       Size of the given buffer.
+ * @param err        Error number to format a string for.
+ * @param remove_end Removes and trailing `\n`, `\r` and `.` characters.
+ */
+const char *
+u_winerror(char *buffer, size_t size, DWORD err, bool remove_end);
+
+
+#ifdef __cplusplus
+}
+#endif