> But it does not get the task done I talked about: type safe container
> like stuff.
I think it would be hard to create a generic type-safe container library in C.
I only see two options: rewrite container manipulation code for every type of
object (as is done in Vim) or define the container code as a set of
preprocessor macros. In both cases a lot of code is duplicated either by the
programmer or by the compiler. Also a lot of code in Vim relies on linked lists
so it would be a huge and error-prone task to change all that.
A solution compatible with the current state of Vim would be to use helpers for
various containers. A helper for the linked list would look like:
struct ListHelper
{
void** list_head_ptr;
void** list_tail_ptr;
int offset_of_next;
int offset_of_prev;
};
void
_lsthlpr_add_head(self, item)
ListHelper* self;
void* item;
{
void *pit = *self->list_head_ptr;
*self->list_head_ptr = item;
*(void**)((char*)item + self->offset_of_next) = pit; /* item->next = pit */
if (self->list_tail_ptr && ! *self->list_tail_ptr)
*self->list_tail_ptr = pit;
}
A list of Node structures along with it's helper would be initialized as:
struct Node
{
Node* next;
int data;
};
Node* my_nodes;
ListHelper my_node_list;
my_node_list.list_head_ptr = &my_nodes;
my_node_list.list_tail_ptr = NULL; // we only use the forward pointer
my_node_list.offset_of_next = offsetof(Node, next);
my_node_list.offset_of_prev = -1; // reverse pointer doesn't exist
Node* pnode = createNode();
_lsthlpr_add_head(&my_node_list, pnode);
You can still traverse the list in a type-safe way through my_nodes. The
manipulation of the list through the list helper is type unsafe.
If you feel it is absolutely necessary, a kind of run-time type safety could be
achieved by adding a typeid member to the beginning of every structure that
would be used in a container. The typeid for a structure would be set in a
'constructor' like createNode(). The same typeid would also be set in the
helper during initialization. The helper methods would compare the value from
the element to the value of the container.
A more complex implementation of the ListHelper is in the file puls_st.c
starting around line 108. It's not exactly C (without some preprocessing) but
it will give you an idea.
http://code.google.com/r/markomahnic-vim-popuplist/source/browse/src/puls_st.c?name=vim-popuplist
A use example is in puls_st.c around line 2466 (_txmfac_init).
http://code.google.com/r/markomahnic-vim-popuplist/source/browse/src/popuplst.c?name=vim-popuplist
Marko
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