client server erl

cs.erl

-module(f).

-export([init/0]).
-export([start/0, get_freq/0, stop/0]).
-export([allocate/0, deallocate/1]).

%%
%% server functions
%%

start()->
    register(f, spawn(f, init, [])).

init() ->
    Freq = {get_freq(), []},
    loop(Freq).                 

get_freq()->
    [10,11,12,13,14,15].

%
% client functions
%

stop() -> call(stop).

allocate() ->  call(allocate).

deallocate(Freq) -> call({deallocate, Freq}).

call( Message ) -> 
    f ! { request, self(), Message },
    receive
	{reply, Reply} ->
	    Reply
   end.

%
% The main loop
%

loop(Frequencies) ->
    receive
	{request, Pid, allocate} ->
	    {NewFreq, Reply} = allocate(Frequencies, Pid),
	    reply(Pid, Reply),
	    loop(NewFreq);
	{request, Pid, {deallocate, Freq}} ->
            NewFreq = deallocate(Frequencies, Freq), 
	    reply(Pid, ok),
	    loop(NewFreq);
	{request, Pid, stop} ->
	    reply(Pid, ok)
    end.

reply(Pid, Reply) ->
    Pid ! Reply.

%
% allocate & deallocate
%

allocate({[], Allocated}, _Pid)->
    {{[], Allocated}, {error, no_freqquency}};
allocate({[Freq | Free], Allocated}, Pid) ->
    {{Free, [{Freq , Pid} | Allocated]}, {ok, Freq}}.

deallocate({Free, Allocated}, Freq) ->
    NewAlloc = lists:keydelete(Freq, 1, Allocated),
    {[Freq | Free], NewAlloc}.