Create shared GUID module to simplify session guid handling

common/guid.h

@@ -0,0 +1,75 @@
+/**
+ * xrdp: A Remote Desktop Protocol server.
+ *
+ * Copyright (C) Jay Sorg 2004-2021
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+/**
+ * @file common/guid.h
+ * @brief GUID manipulation declarations
+  */
+
+#ifndef GUID_H
+#define GUID_H
+
+#include "arch.h"
+
+#define GUID_SIZE 16  /* bytes */
+#define GUID_STR_SIZE (GUID_SIZE * 2 + 1)   /* Size for string representation */
+
+/**
+ * Use a struct for the guid so we can easily copy by assignment
+ */
+struct guid
+{
+    char g[GUID_SIZE];
+};
+
+/**
+ * Get an initialised GUID
+ *
+ * @return new GUID
+ */
+struct guid guid_new(void);
+
+/**
+ * Clears an initialised GUID, so guid_is_set() returns true
+ *
+ * @param guid GUID to clear
+ */
+void
+guid_clear(struct guid *guid);
+
+/**
+ * Checks if a GUID is initialised
+ *
+ * @param guid GUID to check (can be NULL)
+ * @return non-zero if GUID is set
+ */
+int
+guid_is_set(const struct guid *guid);
+
+/**
+ * Converts a GUID to a string representation
+ *
+ * @param guid GUID to represent
+ * @param str pointer to at least GUID_STR_SIZE bytes to store the
+ *            representation
+ * @return str is returned for convenience
+ */
+const char *guid_to_str(const struct guid *guid, char *str);
+
+#endif