util: add json_object_add_format() function

This is to add a format string into the json object.

Signed-off-by: Tokunori Ikegami <[email protected]>

Author: ikegami-t

util/json.c

@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 #include <stdio.h>
 #include <errno.h>
+#include <stdarg.h>
 
 #include "json.h"
 #include "types.h"
@@ -135,3 +136,18 @@ void json_object_add_0nprix64(struct json_object *o, const char *k, uint64_t v,
 	sprintf(str, "0x%0*"PRIx64"", width, v);
 	json_object_add_value_string(o, k, str);
 }
+
+void json_object_add_format(struct json_object *o, const char *k, const char *format, ...)
+{
+	_cleanup_free_ char *value = NULL;
+	va_list ap;
+
+	va_start(ap, format);
+
+	if (vasprintf(&value, format, ap) < 0)
+		value = NULL;
+
+	json_object_add_value_string(o, k, value ? value : "Could not allocate string");
+
+	va_end(ap);
+}

util/json.h

@@ -78,5 +78,6 @@ void json_object_add_byte_array(struct json_object *o, const char *k, unsigned c
 void json_object_add_nprix64(struct json_object *o, const char *k, uint64_t v);
 void json_object_add_uint_0nx(struct json_object *o, const char *k, __u32 v, int width);
 void json_object_add_0nprix64(struct json_object *o, const char *k, uint64_t v, int width);
+void json_object_add_format(struct json_object *o, const char *k, const char *format, ...);
 
 #endif /* __JSON__H */