Add query support

README.md

@@ -75,6 +75,50 @@ Date       SHA        Author
 ...
 ```
 
+###Query
+When you simply read JSON and get values without modifying it, you can use '.' and '[]' to traverse object and array hierarchy.
+```c
+void query_example(void) {
+    JSON_Value *root_value;
+    char *json_string;
+    
+    /* json string to parse */
+    json_string = "{"
+            "\"list\":["
+                "{"
+                    "\"index\":0,"
+                    "\"data\":{"
+                        "\"prop\":\"value\""
+                    "}"
+                "},"
+                "{"
+                    "\"index\":1,"
+                    "\"data\":{"
+                        "\"prop\":null"
+                    "}"
+                "},"
+                "{"
+                    "\"index\":2,"
+                    "\"data\":{"
+                        "\"prop\":123"
+                    "}"
+                "}"
+            "]"
+        "}";
+    
+    /* parsing json string */
+    root_value = json_parse_string(json_string);
+    
+    if (JSONObject == json_type(root_value)) {
+        printf("Query: \"%s\", Result: \"%s\"\n", ".list[0].data.prop", json_value_query_string(root_value, ".list[0].data.prop"));
+        printf("Query: \"%s\", Result: \"%d\"\n", ".list[2].data.prop", (int)json_value_query_number(root_value, ".list[2].data.prop"));
+    }
+    
+    /* cleanup code */
+    json_value_free(root_value);
+}
+```
+
 ###Persistence
 In this example I'm using parson to save user information to a file and then load it and validate later.
 ```c

parson.c

@@ -1929,3 +1929,119 @@ void json_set_allocation_functions(JSON_Malloc_Function malloc_fun, JSON_Free_Fu
     parson_malloc = malloc_fun;
     parson_free = free_fun;
 }
+
+JSON_Value * json_value_query_value(JSON_Value *value, const char *query) {
+    const char *query_start = query, *field_start = query, *field_end = NULL;
+    char *name = NULL;
+    JSON_Value *return_value = NULL;
+    int in_bracket = 0, is_digit = 1;
+    while (query != NULL && *query != '\0') {
+        switch (*query) {
+            case '[':
+                if (in_bracket) {
+                    // Ignore
+                } else if (field_start == query) {
+                    field_start = query + 1;
+                    in_bracket = 1;
+                } else if (field_start < query) {
+                    field_end = query;
+                }
+                break;
+            case ']':
+                if (in_bracket) {
+                    field_end = query;
+                    query++;
+                } else {
+                    return NULL;
+                }
+                break;
+            case '.':
+                if (in_bracket) {
+                    // Ignore
+                } else if (field_start == query) {
+                    if (query_start == query) {
+                        field_start = query + 1;
+                    } else {
+                        // Query ".."
+                        field_end = query;
+                    }
+                } else if (field_start < query) {
+                    field_end = query;
+                    query++;
+                }
+                break;
+            case '0': case '1': case '2': case '3': case '4':
+            case '5': case '6': case '7': case '8': case '9':
+                // Keep is_digit = 1
+                break;
+            default :
+                is_digit = 0;
+                break;
+        }
+        if (field_end != NULL) {
+            break;
+        } else {
+            query++;
+        }
+    }
+    if (query != NULL && query_start < query && !in_bracket && field_end == NULL) {
+        field_end = query;
+    }
+    if (field_end == NULL) {
+        return NULL;
+    }
+    name = parson_strndup(field_start, field_end - field_start);
+    if (name == NULL) {
+        return NULL;
+    }
+    if (0 < strlen(name)) {
+        switch (json_type(value)) {
+            case JSONObject:
+                if (is_digit) {
+                    return_value = json_object_get_value_at(json_value_get_object(value), atol(name));
+                } else {
+                    return_value = json_object_get_value(json_value_get_object(value), name);
+                }
+                break;
+            case JSONArray:
+                if (!is_digit) {
+                    return NULL;
+                }
+                return_value = json_array_get_value(json_value_get_array(value), atol(name));
+                break;
+            default:
+                return NULL;
+        }
+    } else {
+        return_value = value;
+    }
+    parson_free(name);
+    if (*query != '\0' && return_value != NULL) {
+        return_value = json_value_query_value(return_value, query);
+    }
+    return return_value;
+}
+
+const char * json_value_query_string(JSON_Value *value, const char *query) {
+    return json_value_get_string(json_value_query_value(value, query));
+}
+
+JSON_Object * json_value_query_object(JSON_Value *value, const char *query) {
+    return json_value_get_object(json_value_query_value(value, query));
+}
+
+JSON_Array * json_value_query_array(JSON_Value *value, const char *query) {
+    return json_value_get_array(json_value_query_value(value, query));
+}
+
+double json_value_query_number(JSON_Value *value, const char *query) {
+    return json_value_get_number(json_value_query_value(value, query));
+}
+
+int json_value_query_boolean(JSON_Value *value, const char *query) {
+    return json_value_get_boolean(json_value_query_value(value, query));
+}
+
+JSON_Value * json_query(JSON_Value *value, const char *query) {
+    return json_value_query_value(value, query);
+}

parson.h

@@ -224,6 +224,15 @@ const char  *   json_string (const JSON_Value *value);
 double          json_number (const JSON_Value *value);
 int             json_boolean(const JSON_Value *value);
 
+/* Query */
+JSON_Value  * json_value_query_value  (JSON_Value *value, const char *query);
+const char  * json_value_query_string (JSON_Value *value, const char *query);
+JSON_Object * json_value_query_object (JSON_Value *value, const char *query);
+JSON_Array  * json_value_query_array  (JSON_Value *value, const char *query);
+double        json_value_query_number (JSON_Value *value, const char *query); /* returns 0 on fail */
+int           json_value_query_boolean(JSON_Value *value, const char *query); /* returns -1 on fail */
+JSON_Value  * json_query              (JSON_Value *value, const char *query); /* shorter version of json_value_query_value */
+
 #ifdef __cplusplus
 }
 #endif

tests.c

@@ -208,6 +208,36 @@ void test_suite_2(JSON_Value *root_value) {
     TEST(json_object_get_object(root_object, "empty object") != NULL);
     TEST(json_object_get_array(root_object, "empty array") != NULL);
 
+    TEST((json_value_query_value(root_value, ".") == root_value));
+    TEST((json_value_query_value(root_value, "..") == root_value));
+    TEST((json_value_query_value(root_value, "...") == root_value));
+    TEST((json_value_query_value(root_value, "[]") == root_value));
+    TEST((json_value_query_value(root_value, NULL) == NULL));
+    TEST((json_value_query_value(root_value, "") == NULL));
+    TEST((json_value_query_value(root_value, "noexist") == NULL));
+    TEST((json_value_query_value(root_value, ".noexist") == NULL));
+    TEST((json_value_query_value(root_value, "..noexist") == NULL));
+    TEST((json_value_query_value(root_value, "noexist.prop") == NULL));
+    TEST((json_value_query_value(root_value, ".noexist.prop") == NULL));
+    TEST((json_value_query_value(root_value, "..noexist.prop") == NULL));
+    TEST((json_value_query_value(root_value, ".[.no[[exist].prop") == NULL));
+    TEST((json_value_query_value(root_value, ".object].nested true") == NULL));
+    TEST(STREQ(json_value_query_string(root_value, "[0]"), "lorem ipsum"));
+    TEST(STREQ(json_value_query_string(root_value, "object.nested object.lorem"), "ipsum"));
+    TEST(STREQ(json_value_query_string(root_value, "object.nested object[0]"), "ipsum"));
+    TEST(STREQ(json_value_query_string(root_value, "object.nested array[0]"), "lorem"));
+    TEST(STREQ(json_value_query_string(root_value, ".object[nested array][1]"), "ipsum"));
+    TEST((json_value_query_number(root_value, ".object[nested number]") == 123));
+    TEST((json_value_query_boolean(root_value, ".object[nested true]") == 1));
+
+    array = json_value_query_array(root_value, ".object[nested array][]");
+    TEST(array != NULL);
+    TEST(json_array_get_count(array) == 2);
+
+    array = json_value_query_array(root_value, ".[x^2 array][]");
+    TEST(array != NULL);
+    TEST(json_array_get_count(array) == 11);
+
 }
 
 void test_suite_2_no_comments(void) {