设计模式技巧笔记

typedef struct _Item {
    int a;
    char b;
} Item;
typedef struct _ItemList {
    unsigned int size;  // current items count
    unsigned int capacity;  // max items
    Item *items;    // choice-1
    Item **item_ptrs;   //choice-2
} ItemList;
ItemList *NewItemList() {
    ItemList *itemlist_tmp = (ItemList *)malloc(sizeof(ItemList));
    itemlist_tmp->capacity = 4;
    itemlist_tmp->items = (Item *)malloc(sizeof(Item) * itemlist_tmp->capacity);
    if(!itemlist_tmp->items) {
        return NULL;
    }
    itemlist_tmp->item_ptrs = (Item **)malloc(sizeof(Item *) * itemlist_tmp->capacity);
    if(!itemlist_tmp->item_ptrs) {
        return NULL;
    }
    return itemlist_tmp;
}
bool ItemListAdd(ItemList *itemlist, Item *item) {
    if(!itemlist)
        return false;
    
    if(itemlist->size >= itemlist->capacity) {
        Item **item_ptrs_tmp = (Item **)realloc(itemlist->item_ptrs, sizeof(Item *) * itemlist->capacity * 2);
        if(!item_ptrs_tmp)
            return false;
        itemlist->item_ptrs = item_ptrs_tmp;
        itemlist->capacity = itemlist->capacity * 2;
    }
    itemlist->item_ptrs[itemlist->size++] = item;
    return true;
}
Item *ItemListNew(ItemList *itemlist) {
    if(!itemlist)
        return NULL;
    
    if(itemlist->size >= itemlist->capacity) {
        Item *items_tmp = (Item *)realloc(itemlist->items, sizeof(Item) * itemlist->capacity * 2);
        if(!items_tmp)
            return NULL;
        itemlist->items = items_tmp;
        itemlist->capacity = itemlist->capacity * 2;
    }
    return &(itemlist->items[itemlist->size++]);
}
void ItemInitlization() {
    // do something initlizaiton, may be not in this function.
}