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%%% This module implements "setq"-like variables. But, this seems a bit
%%% distasteful because of concurrent updates and so on. Maybe there is
%%% better way to do variables in general (or just program-internal
%%% variables).
-module(edit_var).
-behaviour(gen_server).
%% External exports
-export([start_link/0]).
-export([lookup/1, lookup/2, set/2, permanent/2, add_to_list/2]).
%% gen_server callbacks
-export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2, code_change/3]).
-record(state, {ets, dets}).
%%%----------------------------------------------------------------------
%%% API
%%%----------------------------------------------------------------------
start_link() ->
gen_server:start_link({local, edit_var}, edit_var, [], []).
%% Return: Value | undefined
lookup(Name) ->
lookup(Name, undefined).
lookup(Name, Default) ->
gen_server:call(?MODULE, {lookup, Name, Default}).
set(Name, Value) ->
gen_server:call(?MODULE, {set, Name, Value}).
%% permanent(Name, true | false)
permanent(Name, Flag) ->
gen_server:call(?MODULE, {permanent, Name, Flag}).
add_to_list(Name, Value) ->
List = lookup(Name, []),
edit_var:set(Name, include(List, Value)).
include([], Value) -> [Value];
include([Value|T], Value) -> [Value|T];
include([H|T], Value) -> [H|include(T, Value)].
%%%----------------------------------------------------------------------
%%% Callback functions from gen_server
%%%----------------------------------------------------------------------
%%----------------------------------------------------------------------
%% Func: init/1
%% Returns: {ok, State} |
%% {ok, State, Timeout} |
%% ignore |
%% {stop, Reason}
%%----------------------------------------------------------------------
init([]) ->
Filename = filename:join(os:getenv("HOME"), "edit_var.dets"),
Ets = ets:new(edit_mem_var, [set, public, named_table]),
{ok, Dets} = dets:open_file(edit_disk_var, [{type, set}, {file, Filename}]),
load_file(Dets, Ets),
State = #state{ets = Ets, dets = Dets},
{ok, State}.
%%----------------------------------------------------------------------
%% Func: handle_call/3
%% Returns: {reply, Reply, State} |
%% {reply, Reply, State, Timeout} |
%% {noreply, State} |
%% {noreply, State, Timeout} |
%% {stop, Reason, Reply, State} | (terminate/2 is called)
%% {stop, Reason, State} (terminate/2 is called)
%%----------------------------------------------------------------------
handle_call({lookup, Name, Default}, From, State) ->
{reply, do_lookup(State, Name, Default), State};
handle_call({set, Name, Value}, From, State) ->
ets:insert(State#state.ets, {Name, Value}),
case is_permanent(State, Name) of
true ->
dets:insert(State#state.dets, {Name, Value});
false ->
ok
end,
{reply, ok, State};
handle_call({permanent, Name, Flag}, From, State) ->
case Flag of
false ->
dets:delete(State#state.dets, Name);
true ->
dets:insert(State#state.dets, {Name, do_lookup(State, Name)})
end,
{reply, ok, State}.
%%----------------------------------------------------------------------
%% Func: handle_cast/2
%% Returns: {noreply, State} |
%% {noreply, State, Timeout} |
%% {stop, Reason, State} (terminate/2 is called)
%%----------------------------------------------------------------------
handle_cast(Msg, State) ->
{noreply, State}.
%%----------------------------------------------------------------------
%% Func: handle_info/2
%% Returns: {noreply, State} |
%% {noreply, State, Timeout} |
%% {stop, Reason, State} (terminate/2 is called)
%%----------------------------------------------------------------------
handle_info(Info, State) ->
{noreply, State}.
%%----------------------------------------------------------------------
%% Func: terminate/2
%% Purpose: Shutdown the server
%% Returns: any (ignored by gen_server)
%%----------------------------------------------------------------------
terminate(Reason, State) ->
ok.
%%----------------------------------------------------------------------
%% Func: code_change/3
%% Purpose: Convert process state when code is changed
%% Returns: {ok, NewState}
%%----------------------------------------------------------------------
code_change(OldVsn, State, Extra) ->
{ok, State}.
%%%----------------------------------------------------------------------
%%% Internal functions
%%%----------------------------------------------------------------------
load_file(Dets, Ets) ->
F = fun(X) -> ets:insert(Ets, X) end,
dets:traverse(Dets, F).
do_lookup(State, Name) ->
do_lookup(State, Name, undefined).
do_lookup(State, Name, Default) ->
case ets:lookup(State#state.ets, Name) of
[{_, Value}] ->
Value;
[] ->
Default
end.
is_permanent(State, Name) ->
case dets:lookup(State#state.dets, Name) of
[] ->
false;
_ ->
true
end.
|
