include: data: add missing __cplusplus checks

This patch adds `extern "C"` linkage directives so the header files can
be included by C++ source files.

Signed-off-by: Markus Fuchs <markus.fuchs@de.sauter-bc.com>

include/data/json.h

@@ -7,7 +7,14 @@
 #ifndef ZEPHYR_INCLUDE_DATA_JSON_H_
 #define ZEPHYR_INCLUDE_DATA_JSON_H_
 
+#include <sys/util.h>
+#include <stddef.h>
+#include <zephyr/types.h>
+#include <sys/types.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
 
 /**
  * @brief Structured Data
@@ -21,11 +28,6 @@
  * @{
  */
 
-#include <sys/util.h>
-#include <stddef.h>
-#include <zephyr/types.h>
-#include <sys/types.h>
-
 enum json_tokens {
 	/* Before changing this enum, ensure that its maximum
 	 * value is still within 7 bits. See comment next to the
@@ -632,6 +634,10 @@ int json_obj_encode(const struct json_obj_descr *descr, size_t descr_len,
 		    const void *val, json_append_bytes_t append_bytes,
 		    void *data);
 
+#ifdef __cplusplus
+}
+#endif
+
 /**
  * @}
  */

include/data/jwt.h

@@ -10,6 +10,10 @@
 #include <zephyr/types.h>
 #include <stdbool.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /**
  * @brief JSON Web Token (JWT)
  * @defgroup jwt JSON Web Token (JWT)
@@ -89,6 +93,10 @@ static inline size_t jwt_payload_len(struct jwt_builder *builder)
 	return (builder->buf - builder->base);
 }
 
+#ifdef __cplusplus
+}
+#endif
+
 /**
  * @}
  */