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Improve performance of adding item to array (#448)

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* use prev pointer when adding item to array

Co-authored-by: xiaomianhehe <hongshaokai@hotmail.com>
Co-authored-by: Alanscut <scut@163.com>

Date:   Tue Feb 18 11:54:23 2020 +0800

* add testcase for cJSON_DeleteItemFromArray
This commit is contained in:
Alan Wang 2020-03-24 16:17:25 +08:00 committed by GitHub
parent fa28d82f2e
commit 3ece4c893c
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 67 additions and 13 deletions
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37
cJSON.c
View File

@ -1871,20 +1871,33 @@ static cJSON_bool add_item_to_array(cJSON *array, cJSON *item)
}
child = array->child;
/*
* To find the last item in array quickly, we use prev in array
*/
if (child == NULL)
{
/* list is empty, start new one */
array->child = item;
item->prev = item;
item->next = NULL;
}
else
{
/* append to the end */
while (child->next)
if (child->prev)
{
child = child->next;
suffix_object(child->prev, item);
array->child->prev = item;
}
else
{
while (child->next)
{
child = child->next;
}
suffix_object(child, item);
array->child->prev = item;
}
suffix_object(child, item);
}
return true;
@ -2095,7 +2108,7 @@ CJSON_PUBLIC(cJSON *) cJSON_DetachItemViaPointer(cJSON *parent, cJSON * const it
return NULL;
}
if (item->prev != NULL)
if (item != parent->child)
{
/* not the first element */
item->prev->next = item->next;
@ -2206,14 +2219,20 @@ CJSON_PUBLIC(cJSON_bool) cJSON_ReplaceItemViaPointer(cJSON * const parent, cJSON
{
replacement->next->prev = replacement;
}
if (replacement->prev != NULL)
{
replacement->prev->next = replacement;
}
if (parent->child == item)
{
parent->child = replacement;
}
else
{ /*
* To find the last item in array quickly, we use prev in array.
* We can't modify the last item's next pointer where this item was the parent's child
*/
if (replacement->prev != NULL)
{
replacement->prev->next = replacement;
}
}
item->next = NULL;
item->prev = NULL;

43
tests/misc_tests.c
View File

@ -255,6 +255,7 @@ static void cjson_detach_item_via_pointer_should_detach_items(void)
list[3].prev = &(list[2]);
list[2].prev = &(list[1]);
list[1].prev = &(list[0]);
list[0].prev = &(list[3]);
parent->child = &list[0];
@ -266,7 +267,7 @@ static void cjson_detach_item_via_pointer_should_detach_items(void)
/* detach beginning (list[0]) */
TEST_ASSERT_TRUE_MESSAGE(cJSON_DetachItemViaPointer(parent, &(list[0])) == &(list[0]), "Failed to detach beginning.");
TEST_ASSERT_TRUE_MESSAGE((list[0].prev == NULL) && (list[0].next == NULL), "Didn't set pointers of detached item to NULL.");
TEST_ASSERT_TRUE_MESSAGE((list[2].prev == NULL) && (parent->child == &(list[2])), "Didn't set the new beginning.");
TEST_ASSERT_TRUE_MESSAGE((list[2].prev == &(list[3])) && (parent->child == &(list[2])), "Didn't set the new beginning.");
/* detach end (list[3])*/
TEST_ASSERT_TRUE_MESSAGE(cJSON_DetachItemViaPointer(parent, &(list[3])) == &(list[3]), "Failed to detach end.");
@ -306,7 +307,7 @@ static void cjson_replace_item_via_pointer_should_replace_items(void)
/* replace beginning */
TEST_ASSERT_TRUE(cJSON_ReplaceItemViaPointer(array, beginning, &(replacements[0])));
TEST_ASSERT_NULL(replacements[0].prev);
TEST_ASSERT_TRUE(replacements[0].prev == end);
TEST_ASSERT_TRUE(replacements[0].next == middle);
TEST_ASSERT_TRUE(middle->prev == &(replacements[0]));
TEST_ASSERT_TRUE(array->child == &(replacements[0]));
@ -346,7 +347,7 @@ static void cjson_replace_item_in_object_should_preserve_name(void)
cJSON_Delete(replacement);
}
static void cjson_functions_shouldnt_crash_with_null_pointers(void)
static void cjson_functions_should_not_crash_with_null_pointers(void)
{
char buffer[10];
cJSON *item = cJSON_CreateString("item");
@ -549,6 +550,39 @@ static void cjson_add_item_to_object_should_not_use_after_free_when_string_is_al
cJSON_Delete(object);
}
static void cjson_delete_item_from_array_should_not_broken_list_structure(void) {
const char expected_json1[] = "{\"rd\":[{\"a\":\"123\"}]}";
const char expected_json2[] = "{\"rd\":[{\"a\":\"123\"},{\"b\":\"456\"}]}";
const char expected_json3[] = "{\"rd\":[{\"b\":\"456\"}]}";
char* str1 = NULL;
char* str2 = NULL;
char* str3 = NULL;
cJSON* root = cJSON_Parse("{}");
cJSON* array = cJSON_AddArrayToObject(root, "rd");
cJSON* item1 = cJSON_Parse("{\"a\":\"123\"}");
cJSON* item2 = cJSON_Parse("{\"b\":\"456\"}");
cJSON_AddItemToArray(array, item1);
str1 = cJSON_PrintUnformatted(root);
TEST_ASSERT_EQUAL_STRING(expected_json1, str1);
free(str1);
cJSON_AddItemToArray(array, item2);
str2 = cJSON_PrintUnformatted(root);
TEST_ASSERT_EQUAL_STRING(expected_json2, str2);
free(str2);
/* this should not broken list structure */
cJSON_DeleteItemFromArray(array, 0);
str3 = cJSON_PrintUnformatted(root);
TEST_ASSERT_EQUAL_STRING(expected_json3, str3);
free(str3);
cJSON_Delete(root);
}
int CJSON_CDECL main(void)
{
UNITY_BEGIN();
@ -565,7 +599,7 @@ int CJSON_CDECL main(void)
RUN_TEST(cjson_detach_item_via_pointer_should_detach_items);
RUN_TEST(cjson_replace_item_via_pointer_should_replace_items);
RUN_TEST(cjson_replace_item_in_object_should_preserve_name);
RUN_TEST(cjson_functions_shouldnt_crash_with_null_pointers);
RUN_TEST(cjson_functions_should_not_crash_with_null_pointers);
RUN_TEST(ensure_should_fail_on_failed_realloc);
RUN_TEST(skip_utf8_bom_should_skip_bom);
RUN_TEST(skip_utf8_bom_should_not_skip_bom_if_not_at_beginning);
@ -574,6 +608,7 @@ int CJSON_CDECL main(void)
RUN_TEST(cjson_create_object_reference_should_create_an_object_reference);
RUN_TEST(cjson_create_array_reference_should_create_an_array_reference);
RUN_TEST(cjson_add_item_to_object_should_not_use_after_free_when_string_is_aliased);
RUN_TEST(cjson_delete_item_from_array_should_not_broken_list_structure);
return UNITY_END();
}