Hi Gaganjyot,
your examples are high level but need some note:
> Dwg_Object_LAYER ** extract_layers(Dwg_Data *dwg)
There is a Dwg_Object_LAYER_CONTROL struct in the drawing which represents the
layer table. A good API function would be:
Dwg_Object_LAYER_CONTROL* dwg_get_layer_control(Dwg_Data *dwg);
To access the layer control these functions are possible:
// returns the number of records in the layer table
int dwg_layer_control_get_length(Dwg_Object_LAYER_CONTROL *ctrl);
// returns the layer at a given index
Dwg_Object_LAYER* dwg_layer_control_get_at(Dwg_Object_LAYER_CONTROL *ctrl, int
index);
// returns the layer with a given handle
Dwg_Object_LAYER* dwg_layer_control_get_by_handle(Dwg_Object_LAYER_CONTROL
*ctrl, Dwg_Handle *handle);
// returns the layer with a given handle
Dwg_Object_LAYER* dwg_layer_control_get_by_name(Dwg_Object_LAYER_CONTROL *ctrl,
DWGCHAR *name);
> unsigned char *
> get_layer_name(Dwg_Object_Entity *entity, Dwg_Object_LAYER *layer)
This function is a litle bit too high level. It not only returns the name of a
layer but the layer itself. It wold be better to split the function:
Dwg_Object_LAYER* dwg_entity_get_layer(Dwg_Object_Entity *entity);
DWGCHAR dwg_layer_get_name(Dwg_Object_LAYER *layer);
An API should hide the implementation details, that means a user of the API
should not see the variables of internal structs like Dwg_Object_LAYER_CONTROL.
Declare it as an opaque pointer in the header for the API:
typedef struct Dwg_Object_LAYER_CONTROL Dwg_Object_LAYER_CONTROL;
In the .c file where you implement the functions you can include the dwg.h and
have the detailed definitions of all structs.
regards
Till
Am 24.05.2013 um 17:54 schrieb gagan:
> On 5/24/13, Rodrigo Rodrigues da Silva <pita...@members.fsf.org> wrote:
>
> <snip>
>
>> As for low-level/high-level examples:
>>
>>
>> Dwg_Object * should_be_layer = obj->tio.entity->layer->obj;
>> Dwg_Object_LAYER * layer;
>> unsigned int _type = should_be_layer->type;
>> //dwg_print_object(should_be_layer);
>> printf("type = %u ", _type);
>> if (_type == 51)
>> {
>> layer = obj->tio.entity->layer->obj->tio.object->tio.LAYER; //low
>> level struct access
>>
>> in a higher level c-ish way:
>>
>> Dwg_Object_LAYER * layer;
>>
>> int error = dwg_get_obj_layer(obj, &layer); //higher level c api
>
> <snip>
>
>> another example (I've implemented it already, I guess)
>>
>> int layer_count = dwg_get_layer_count(&dwg_data);
>
> Reading these, I have created 2 examples, Please have a look at them
> and tell me if we can consider them developed in high level C ?
>
> My API code :-
>
> Dwg_Object_LAYER ** extract_layers(Dwg_Data *dwg)
> {
> int i, a=0;
> Dwg_Object_LAYER **layer = (Dwg_Object_LAYER **)malloc(
> dwg_get_layer_count(dwg) * (sizeof (Dwg_Object_LAYER*) + 10));
> for (i = 0; i < dwg->num_objects; i++)
> {
> if(DWG_TYPE_LAYER==dwg->object[i].type)
> {
> layer[a] = dwg->object[i].tio.object->tio.LAYER;
> a++;
> }
> }
> return layer;
> }
>
> Application code :-
>
> extract_layers(&dwg);
>
> My API code :-
>
> unsigned char *
> get_layer_name(Dwg_Object_Entity *entity, Dwg_Object_LAYER *layer)
> {
> layer = entity->layer->obj->tio.object->tio.LAYER;
> return layer->entry_name;
> }
>
> Application code :-
> Dwg_Object_LAYER *layer;
> get_layer_name(entity, layer); //here entity can be any, user should
> know how to get entity here.
>
> --
> Thanks
> Gaganjyot
>
