【erlang ets】

shijiang1130

1. cache_create() ->
   
2.     ets:new(cm_tab, [set,{keypos, #channel.local_id}]).
   
3. 
   
4. cache_lookup(Cache, Key) ->
   
5.     case ets:lookup(Cache, Key) of
   
6.         [Channel] ->
   
7.             Channel;
   
8.         [] ->
   
9.             undefined
   
10.     end.
    
11. 
    
12. cache_update(Cache, #channel{local_id = Id} = Entry) when Id =/= undefined ->
    
13.     ets:insert(Cache, Entry).
    
14. 
    
15. cache_delete(Cache, Key) ->
    
16.     ets:delete(Cache, Key).
    
17. 
    
18. cache_delete(Cache) ->
    
19.     ets:delete(Cache).
    
20. 
    
21. cache_foldl(Fun, Acc, Cache) ->
    
22.     ets:foldl(Fun, Acc, Cache).
    
23.    
    
24. cache_find(ChannelPid, Cache) ->
    
25.    case ets:match_object(Cache, #channel{user = ChannelPid}) of
    
26.        [] ->
    
27.            undefined;
    
28.        [Channel] ->
    
29.            Channel
    
30.    end.

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shijiang1130

1. {keypos,Pos} Specfies which element in the stored tuples should be used as key. By default, it is the first element, i.e. Pos=1. However, this is not always appropriate. In particular, we do not want the first element to be the key if we want to store Erlang records in a table.
   
2. 
   
3. Note that any tuple stored in the table must have at least Pos number of elements.

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