Skip to content

Optimize object comparison #971

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
ShaunRember wants to merge 1 commit into
base: master
Choose a base branch
from
Open

Optimize object comparison #971

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
109 changes: 74 additions & 35 deletions cJSON.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3054,6 +3054,77 @@ CJSON_PUBLIC(cJSON_bool) cJSON_IsRaw(const cJSON * const item)
return (item->type & 0xFF) == cJSON_Raw;
}

static cJSON_bool compare_object(const cJSON * const a, const cJSON * const b, const cJSON_bool case_sensitive)
{
cJSON *a_element = NULL;
cJSON *b_element = NULL;
cJSON *last_b = NULL;
cJSON *found_b = NULL;
cJSON_bool keys_are_orderly = true;

a_element = a->child;
b_element = b->child;
while (a_element && b_element)
{
a_element = a_element->next;
b_element = b_element->next;
}
if (a_element != b_element)
{
/* The objects don't have the same number of keys */
return false;
}

a_element = a->child;
b_element = b->child;
while (a_element && keys_are_orderly)
{
if ((case_sensitive && strcmp(a_element->string, b_element->string) == 0) || (!case_sensitive && case_insensitive_strcmp((const unsigned char*)a_element->string, (const unsigned char*)(b_element->string)) == 0))
{
if (!cJSON_Compare(a_element, b_element, case_sensitive))
{
return false;
}
a_element = a_element->next;
b_element = b_element->next;
}
else
{
/* Stop assuming the keys are orderly */
/* Values of a_element and b_element_last_orderly allow us to reuse any work accomplished in this loop */
last_b = b_element;
keys_are_orderly = false;
}
}

if (keys_are_orderly)
{
/* Iterated through all a and b with no key mismatches and all comparisons returned true */
return true;
}

/* The keys mismatch or are in diffrent order so we need to search b for each one */
/* This is O(n^2) at runtime */
for (; a_element; a_element = a_element->next)
{
found_b = NULL;
for (b_element = last_b; b_element && !found_b; b_element = b_element->next)
{
if ((case_sensitive && strcmp(a_element->string, b_element->string) == 0) || (!case_sensitive && case_insensitive_strcmp((const unsigned char*)a_element->string, (const unsigned char*)(b_element->string)) == 0))
{
found_b = b_element;
}
}

if (!found_b || !cJSON_Compare(a_element, found_b, case_sensitive))
{
return false;
}
}

return true;
}

CJSON_PUBLIC(cJSON_bool) cJSON_Compare(const cJSON * const a, const cJSON * const b, const cJSON_bool case_sensitive)
{
if ((a == NULL) || (b == NULL) || ((a->type & 0xFF) != (b->type & 0xFF)))
Expand Down Expand Up @@ -3137,42 +3208,10 @@ CJSON_PUBLIC(cJSON_bool) cJSON_Compare(const cJSON * const a, const cJSON * cons
}

case cJSON_Object:
{
cJSON *a_element = NULL;
cJSON *b_element = NULL;
cJSON_ArrayForEach(a_element, a)
{
/* TODO This has O(n^2) runtime, which is horrible! */
b_element = get_object_item(b, a_element->string, case_sensitive);
if (b_element == NULL)
{
return false;
}

if (!cJSON_Compare(a_element, b_element, case_sensitive))
{
return false;
}
}

/* doing this twice, once on a and b to prevent true comparison if a subset of b
* TODO: Do this the proper way, this is just a fix for now */
cJSON_ArrayForEach(b_element, b)
{
a_element = get_object_item(a, b_element->string, case_sensitive);
if (a_element == NULL)
{
return false;
}

if (!cJSON_Compare(b_element, a_element, case_sensitive))
{
return false;
}
if(compare_object(a, b, case_sensitive)) {
return true;
}

return true;
}
return false;

default:
return false;
Expand Down