A little problem about hashmap about sc HOT 2 CLOSED

Yes, it's clear. I understand, thank you very much!

from sc.

Hi @JustDoIt0910

Internally, map uses an array (struct sc_map_item_str *mem above). struct sc_map_item_xx is like:

struct sc_map_item_##name {
	K key; 
	V value;
	uint32_t hash;
}; 

This array contains some key value pairs, some of them are used some of them are not.
If the key of an array item is zero (key == 0), it means that item/slot is empty. So, we can place the new item there.

What if user wants to store key=0, (say key = 0, value = 15). How are we going to distinguish between "empty indicator" key=0 and this valid item?

Hashmap does a trick, if user wants to put key=0, hashmap stores it as the first item:

So, how do you know if that special slot is empty or not? Hashmap uses used boolean for that. If user puts key=0 to the map, it will be stored as the first item and used value will be true. So, when user calls get(key=0), we'll know if there is a real value in that special slot.

For pointer types (like str, void*), special key is NULL btw.

Let me know if this is clear. Cheers!

from sc.