Add getNumberValue function

* Add GetNumberValue function and testcase

Co-authored-by: Alan Wang <wp_scut@163.com>

cJSON.c

@@ -79,14 +79,26 @@ CJSON_PUBLIC(const char *) cJSON_GetErrorPtr(void)
     return (const char*) (global_error.json + global_error.position);
 }
 
-CJSON_PUBLIC(char *) cJSON_GetStringValue(const cJSON * const item) {
-    if (!cJSON_IsString(item)) {
+CJSON_PUBLIC(char *) cJSON_GetStringValue(cJSON *item) 
+{
+    if (!cJSON_IsString(item)) 
+    {
         return NULL;
     }
 
     return item->valuestring;
 }
 
+CJSON_PUBLIC(double) cJSON_GetNumberValue(cJSON *item) 
+{
+    if (!cJSON_IsNumber(item)) 
+    {
+        return 0.0/0.0;
+    }
+
+    return item->valuedouble;
+}
+
 /* This is a safeguard to prevent copy-pasters from using incompatible C and header files */
 #if (CJSON_VERSION_MAJOR != 1) || (CJSON_VERSION_MINOR != 7) || (CJSON_VERSION_PATCH != 12)
     #error cJSON.h and cJSON.c have different versions. Make sure that both have the same.

cJSON.h

@@ -180,8 +180,9 @@ CJSON_PUBLIC(cJSON_bool) cJSON_HasObjectItem(const cJSON *object, const char *st
 /* For analysing failed parses. This returns a pointer to the parse error. You'll probably need to look a few chars back to make sense of it. Defined when cJSON_Parse() returns 0. 0 when cJSON_Parse() succeeds. */
 CJSON_PUBLIC(const char *) cJSON_GetErrorPtr(void);
 
-/* Check if the item is a string and return its valuestring */
-CJSON_PUBLIC(char *) cJSON_GetStringValue(const cJSON * const item);
+/* Check item type and return its value */
+CJSON_PUBLIC(char *) cJSON_GetStringValue(cJSON *item);
+CJSON_PUBLIC(double) cJSON_GetNumberValue(cJSON *item);
 
 /* These functions check the type of an item */
 CJSON_PUBLIC(cJSON_bool) cJSON_IsInvalid(const cJSON * const item);

tests/misc_tests.c

@@ -486,6 +486,19 @@ static void cjson_get_string_value_should_get_a_string(void)
     cJSON_Delete(string);
 }
 
+static void cjson_get_number_value_should_get_a_number(void)
+{
+    cJSON *string = cJSON_CreateString("test");
+    cJSON *number = cJSON_CreateNumber(1);
+
+    TEST_ASSERT_EQUAL_DOUBLE(cJSON_GetNumberValue(number), number->valuedouble);
+    TEST_ASSERT_DOUBLE_IS_NAN(cJSON_GetNumberValue(string));
+    TEST_ASSERT_DOUBLE_IS_NAN(cJSON_GetNumberValue(NULL));
+    
+    cJSON_Delete(number);
+    cJSON_Delete(string);
+}
+
 static void cjson_create_string_reference_should_create_a_string_reference(void) {
     const char *string = "I am a string!";
 
@@ -604,6 +617,7 @@ int CJSON_CDECL main(void)
     RUN_TEST(skip_utf8_bom_should_skip_bom);
     RUN_TEST(skip_utf8_bom_should_not_skip_bom_if_not_at_beginning);
     RUN_TEST(cjson_get_string_value_should_get_a_string);
+    RUN_TEST(cjson_get_number_value_should_get_a_number);
     RUN_TEST(cjson_create_string_reference_should_create_a_string_reference);
     RUN_TEST(cjson_create_object_reference_should_create_an_object_reference);
     RUN_TEST(cjson_create_array_reference_should_create_an_array_reference);