unorthidox use of GAllocator and GSList?

[Ben Johnson <ben@xxxxxxxxx>]

Hi

I'm wondering if I should cease and desist.  I'm using the GSList and
the GAllocator in way that they may not be designed for.  The reason I
am doing it this way is I want to allocate space for my list nodes and
my data in the same big chunk.  In other words, I'm creating list nodes
that contain more information than just a next pointer and a data
pointer, and then using the usual g_slist*() interface to manage the
memory and and the (extended) list nodes.  code blurbs included below...
I haven't tested this very thoroughly yet, but it does appear to work.

What I want to know is, should I avoid doing this?  I worry there's a
possibility glib may change in a way that will cause my app to crash or
fail to compile, etc..

Thanks,

- Ben



typedef struct menu_page menu_page_t;

struct menu_page {
    GSList listnode;
    char page_name[PAGE_LABEL_LEN+1];
    int page_number;
    unsigned int row_count;
    unsigned int col_count;
    menu_option_group_t * grouplist;
};

void
func1( GAllocator ** a )
{
    sqlbuf = queries[i];
    count = db_run_count_query(sqlbuf, strlen(sqlbuf));

    /* gslist.c showed me how to do this.  */
    *a = g_allocator_new("my allocator", count);
    (*a)->type       = G_ALLOCATOR_SLIST;
    (*a)->free_lists = NULL;
    (*a)->mem_chunk  = g_mem_chunk_new((*a)->name,
                                       sizeof(menu_page_t),
                                       sizeof(menu_page_t) * (*a)->n_preallocs,
                                       G_ALLOC_ONLY);
}

static menu_page_t * menu_pages = NULL;

void 
func2( GAllocator * a )
{
    g_slist_push_allocator( a );
    /* g_slist_append() returns the list node you pass to it,
     * except when you pass NULL, then it a new node. so,  */
    if( ! menu_pages ) {
        /* make first node */
        menu_pages = (menu_page_t *)g_slist_append(NULL, NULL);
        new_menu_page = menu_pages;
    } else {
        /* returns node passed. */
        g_slist_append( (GSList*)new_menu_page, NULL );

        /* make sure new_menu_page is always the
        * latest added and the last in the list. */
        new_menu_page = (menu_page_t *)((GSList*)new_menu_page)->next;
    }
    g_slist_pop_allocator();

    initialize_new_node( new_menu_page );

    /* and so on */
}

static GAllocator * menu_page_allocator = NULL;

void func0(void)
{
    /* create my allocator */
    func1( &menu_page_allocator );

    /* add a node to the list using the allocator */
    func2( menu_page_allocator );
}

_______________________________________________

gtk-list@xxxxxxxxx
http://mail.gnome.org/mailman/listinfo/gtk-list