introduce json_object_new_string_noalloc()

On some low memory systems, calling malloc (by the use of strdup) causes
memory fragmentation which eventually results in out of memory
situation. using json_object_new_string_noalloc helps to solve this
issue.

also add basic test for json_object_new_string_noalloc

json_object.c

@@ -1015,6 +1015,23 @@ static void json_object_string_delete(struct json_object* jso)
 	json_object_generic_delete(jso);
 }
 
+struct json_object* json_object_new_string_noalloc(char *s)
+{
+	struct json_object *jso = json_object_new(json_type_string);
+	if (!jso)
+		return NULL;
+	jso->_delete = &json_object_string_delete;
+	jso->_to_json_string = &json_object_string_to_json_string;
+	jso->o.c_string.len = strlen(s);
+	if(jso->o.c_string.len < LEN_DIRECT_STRING_DATA) {
+		memcpy(jso->o.c_string.str.data, s, jso->o.c_string.len);
+		free(s);
+	} else {
+		jso->o.c_string.str.ptr = s;
+	}
+	return jso;
+}
+
 struct json_object* json_object_new_string(const char *s)
 {
 	struct json_object *jso = json_object_new(json_type_string);

json_object.h

@@ -893,6 +893,19 @@ JSON_EXPORT int json_object_set_double(struct json_object *obj,double new_value)
 
 /* string type methods */
 
+/** Create a new empty json_object of type json_type_string
+ *
+ * Use given string as is, do not call malloc if given string is longer
+ * than internal buffer size. Ownership of s will be transferred to
+ * json_object and s will be freed when json_object_put decided to free
+ * memory of json_object.
+ *
+ * @param s the string, must be heap alloacted and must not be freed.
+ * @returns a json_object of type json_type_string
+ * @see json_object_new_string_len()
+ */
+JSON_EXPORT struct json_object* json_object_new_string_noalloc(char *s);
+
 /** Create a new empty json_object of type json_type_string
  *
  * A copy of the string is made and the memory is managed by the json_object

tests/Makefile.am

@@ -27,6 +27,7 @@ TESTS+= test_set_value.test
 TESTS+= test_visit.test
 TESTS+= test_json_pointer.test
 TESTS+= test_int_add.test
+TESTS+= test_string_noalloc.test
 
 check_PROGRAMS=
 check_PROGRAMS += $(TESTS:.test=)

tests/test_string_noalloc.c

@@ -0,0 +1,48 @@
+/*
+ * Tests if binary strings are supported.
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <string.h>
+#include "config.h"
+
+#include "json_inttypes.h"
+#include "json_object.h"
+#include "json_tokener.h"
+
+int main(void)
+{
+	/* this test has a space after the null character. check that it's still included */
+	char *str1 = strdup("This string should be longer than 32 characters");
+	char *str2 = strdup("this string is short");
+	struct json_object *jso_str = NULL;
+
+	if (!str1 || !str2)
+	{
+		puts("FAIL: strdup() returned NULL");
+		return 1;
+	}
+
+	jso_str = json_object_new_string_noalloc(str1);
+	if (!jso_str)
+	{
+		puts("FAIL: json_object_new_string_noalloc(str1) returned NULL");
+		return 2;
+	}
+
+	json_object_put(jso_str);
+	jso_str = NULL;
+
+	jso_str = json_object_new_string_noalloc(str2);
+	if (!jso_str)
+	{
+		puts("FAIL: json_object_new_string_noalloc(str2) returned NULL");
+		return 3;
+	}
+
+	json_object_put(jso_str);
+
+	puts("PASS");
+	return 0;
+}

tests/test_string_noalloc.expected

@@ -0,0 +1 @@
+PASS

tests/test_string_noalloc.test

@@ -0,0 +1 @@
+test_basic.test