update README.md

README.md

 # json-editor
 
-javascript style json editor for c
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+Json-editor is a library built on top of json-c to offer a syntax akin to javascript when modifying JSON.
+
+## Building
+
+The library is built using cmake. To build and install the library on your machine run the following instructions from the root directory:
+
+```
+mkdir build
+cd build
+cmake ../ -DCMAKE_BUILD_TYPE=Release
+make
+sudo make install
+```
+
+## API
+
+The library currently offers three features, a getter and setter accepting a javascript format string representing the syntax, and two functions reading/writing JSON to a file.
+
+### Setter
+
+The setter function, ```json_object_set_by_string_delimiter(5)```, takes five arguments, albeit with recommended to be used through a wrapper function ```json_object_set_by_string(4)```, defaulting the delimiter to a dot,```.```.
+
+```
+int json_object_set_by_string_delimiter(struct json_object **src, char *fmt, char *val, enum json_type type, const char *delimiter)
+```
+
+```src``` is a pointer to the address of a ```struct json_object```, if it is a null pointer an object will be created.
+```fmt``` is a string representing the syntax pointing to the object to be set, i.e. ```device.macaddr```, note that this syntax may contain nested objects or arrays without restrictions, i.e. ```a.b[1][0].c```. Additionally, if a key, array or index is missing it will be created and added to the ```src``` pointer. *NULL represents root key.*
+```val``` represents the value to be set. This should always be presented in a string format, albeit can be used to represent integers, strings, arrays of object depending on syntax, i.e. ```{\"macaddr\":\"11:22:33:44:55:66\"}```.
+```type``` expects an enum of ```json_type```, to declare as what object type the input should be added.
+```delimiter``` is syntactical delimiter in the format string.
+
+#### Example usage
+
+```
+    json_object_set_by_string(&e->modify_obj, "nested0.nested1.integer", "1", json_type_int);
+    json_object_set_by_string(&e->modify_obj, "ints", "[ 1, 2, 3 ]", json_type_array);
+    json_object_set_by_string(&e->modify_obj, "string", "1", json_type_string);
+    json_object_set_by_string(&e->modify_obj, "integer", "1", json_type_int);
+    json_object_set_by_string(&e->modify_obj, "obj", "{\"test2\":\"success\"}", json_type_object);
+```
+
+Assuming an empty starting object this results in the object:
+
+```
+{ "nested0": { "nested1": { "integer": 1 } }, "ints": [ 1, 2, 3 ], "string": "1", "integer": 1, "obj": { "test2": "success" } }
+```
+
+For more example usage see ```test/api_test.c```.
+
+### Getter
+
+The getter function, ```json_object_get_by_string_delimiter(5)```, similarily to the setter, takes five arguments, recommended to be used through a wrapper function ```json_object_get_by_string(4)```, defaulting the delimiter to a dot,```.```. If the specified format is not present in the object NULL is returned.
+
+```
+struct json_object *json_object_get_by_string_delimiter(struct json_object *src, char *fmt, const char *delimiter);
+```
+
+```src``` is a pointer to the  ```struct json_object``` to traverse.
+```fmt``` is a string representing the syntax pointing to the object to be set, i.e. ```device.macaddr```, note that this syntax may contain nested objects or arrays without restrictions, i.e. ```a.b[1][0].c```.
+```delimiter``` is syntactical delimiter in the format string.
+
+#### Example usage
+
+Assuming the starting json:
+
+```
+{ "nested0": { "nested1": { "integer": 1 } }, "ints": [ 1, 2, 3 ], "string": "1", "integer": 1, "obj": { "test2": "success" } }
+```
+Using the getter:
+
+```
+   json_object_get_by_string(e->file_obj, "integer");
+```
+
+Will return an json object containing ```1```.
+
+For more example usage see ```test/api_test.c```.
+
+### Read/Write to file
+
+A file to json and a json to file functions have been prepared.
+
+```
+struct json_object *json_object_file_to_obj(const char *path);
+int json_object_obj_to_file(struct json_object *obj, const char *path);
+```
+The ```json_object_file_to_obj(1)``` function takes the path to read from as an input and returns an allocated ```struct json_object``` pointer on success, NULL on failure.
+
+```json_object_obj_to_file(2)``` takes the object to write to file as first argument, and path to the file as second argument. On success 0 is returned, on failure -1.
+
+For example usage see ```test/api_test.c```.
+
+## Tests
+
+During the development of this library cmocka unit testing was utilized. In total 28 unit tests are prepared, testing a varity of scenarios, with a focus on setters, these unit tests are furthermore tested with valgrind to ensure no memory leaks are present.
+
+To run the tests perform the same steps as described under the build section and then run
+
+```
+sudo make test
+```
+
+This should run the test cases available:
+```
+Running tests...
+Test project /home/jakob/git/json-editor/build/test
+    Start 1: api_test
+1/2 Test #1: api_test .........................   Passed    0.00 sec
+    Start 2: api_test_valgrind
+2/2 Test #2: api_test_valgrind ................   Passed    0.57 sec
+
+100% tests passed, 0 tests failed out of 2
+
+Total Test time (real) =   0.57 sec
+```
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