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% Licensed under the Apache License, Version 2.0 (the "License"); you may not
% use this file except in compliance with the License. You may obtain a copy of
% the License at
%
% http://www.apache.org/licenses/LICENSE-2.0
%
% Unless required by applicable law or agreed to in writing, software
% distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
% WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
% License for the specific language governing permissions and limitations under
% the License.
%% @doc Reads CouchDB's ini file and gets queried for configuration parameters.
%% This module is initialized with a list of ini files that it
%% consecutively reads Key/Value pairs from and saves them in an ets
%% table. If more an one ini file is specified, the last one is used to
%% write changes that are made with store/2 back to that ini file.
-module(couch_config).
-include("couch_db.hrl").
-behaviour(gen_server).
-export([start_link/1, init/1,
handle_call/3, handle_cast/2, handle_info/2,
terminate/2, code_change/3]).
-export([store/2, register/1, register/2,
get/1, get/2,
lookup_match/1, lookup_match/2,
all/0, unset/1, load_ini_file/1]).
-record(config,
{notify_funs=[],
writeback_filename=""
}).
%% Public API %%
%% @type etstable() = integer().
start_link(IniFiles) -> gen_server:start_link({local, ?MODULE}, ?MODULE, IniFiles, []).
%% @spec store(Key::any(), Value::any()) -> {ok, Tab::etsatable()}
%% @doc Public API function that triggers storage of a Key/Value pair into the
%% local ets table and writes it to the storage ini file.
store(Key, Value) -> gen_server:call(?MODULE, {store, [{Key, Value}]}).
%% @spec get(Key::any()) -> Value::any() | undefined
%% @doc Returns the value that is stored under key::any() or undefined::atom() if no
%% such Key exists.
get(Key) ->
?MODULE:get(Key, undefined).
%% @spec get(Key::any(), Default::any()) -> Value::any() | Default
%% @doc Returns the value that is stored under key::any() or Default::any() if
%% no such Key exists.
get(Key, Default) ->
fix_lookup_result(ets:lookup(?MODULE, Key), Default).
%% @spec lookup_match(Key::any()) -> Value::any() | undefined:atom()
%% @doc Lets you look for a Key's Value specifying a pattern that gets passed
%% to ets::match(). Returns undefined::atom() if no Key is found.
lookup_match(Key) -> gen_server:call(?MODULE, {lookup_match, Key}).
%% @spec lookup_match(Key::any(), Default::any()) -> Value::any() | Default
%% @doc Lets you look for a Key's Value specifying a pattern that gets passed
%% to ets::match(). Returns Default::any() if no Key is found
lookup_match(Key, Default) -> gen_server:call(?MODULE, {lookup_match, Key, Default}).
all() -> gen_server:call(?MODULE, all).
register(Fun) -> gen_server:call(?MODULE, {register, Fun, self()}).
register(Fun, Pid) -> gen_server:call(?MODULE, {register, Fun, Pid}).
%% @spec unset(Key::any) -> ok
%% @doc Public API call to remove the configuration entry from the internal
%% ets table. This change is _not_ written to the storage ini file.
unset(Key) -> gen_server:call(?MODULE, {unset, Key}).
%% Private API %%
%% @spec init(List::list([])) -> {ok, Tab::etsatable()}
%% @doc Creates a new ets table of the type "set".
init(IniFiles) ->
ets:new(?MODULE, [named_table, set, protected]),
[ok = load_ini_file(IniFile) || IniFile <- IniFiles],
{ok, #config{writeback_filename=lists:last(IniFiles)}}.
%% @doc see store/2
handle_call({store, KVs}, _From, Config) ->
[ok = insert_and_commit(Config, KV) || KV <- KVs],
{reply, ok, Config};
%% @doc See init_value/2
handle_call({init_value, Key, Value}, _From, Config) ->
Reply = ets:insert(?MODULE, {Key, Value}),
{reply, Reply, Config};
%% @doc See unset/1
handle_call({unset, Key}, _From, Config) ->
ets:delete(?MODULE, Key),
{reply, ok, Config};
%% @doc See lookup_match/2
handle_call({lookup_match, Key, Default}, _From, Config) ->
{reply, fix_lookup_result(ets:match(?MODULE, Key), Default), Config};
handle_call(all, _From, Config) ->
{reply, lists:sort(ets:tab2list(?MODULE)), Config};
%% @doc See register/2
handle_call({register, Fun, Pid}, _From, #config{notify_funs=PidFuns}=Config) ->
erlang:monitor(process, Pid),
{reply, ok, Config#config{notify_funs=[{Pid, Fun}|PidFuns]}}.
fix_lookup_result([{_Key, Value}], _Default) ->
Value;
fix_lookup_result([], Default) ->
Default;
fix_lookup_result(Values, _Default) ->
[list_to_tuple(Value) || Value <- Values].
%% @spec insert_and_commit(Tab::etstable(), Config::any()) -> ok
%% @doc Inserts a Key/Value pair into the ets table, writes it to the storage
%% ini file and calls all registered callback functions for Key.
insert_and_commit(Config, KV) ->
true = ets:insert(?MODULE, KV),
% notify funs
%[catch Fun(KV) || {_Pid, Fun} <- Config#config.notify_funs],
couch_config_writer:save_to_file(KV, Config#config.writeback_filename).
%% @spec load_ini_file(IniFile::filename()) -> ok
%% @doc Parses an ini file and stores Key/Value Pairs into the ets table.
load_ini_file(IniFile) ->
IniFilename = couch_util:abs_pathname(IniFile),
IniBin =
case file:read_file(IniFilename) of
{ok, IniBin0} ->
IniBin0;
{error, enoent} ->
Msg = io_lib:format("Couldn't find server configuration file ~s.", [IniFilename]),
io:format("~s~n", [Msg]),
throw({startup_error, Msg})
end,
{ok, Lines} = regexp:split(binary_to_list(IniBin), "\r\n|\n|\r|\032"),
{_, ParsedIniValues} =
lists:foldl(fun(Line, {AccSectionName, AccValues}) ->
case string:strip(Line) of
"[" ++ Rest ->
case regexp:split(Rest, "\\]") of
{ok, [NewSectionName, ""]} ->
{NewSectionName, AccValues};
_Else -> % end bracket not at end, ignore this line
{AccSectionName, AccValues}
end;
";" ++ _Comment ->
{AccSectionName, AccValues};
Line2 ->
case regexp:split(Line2, "=") of
{ok, [_SingleElement]} -> % no "=" found, ignore this line
{AccSectionName, AccValues};
{ok, [""|_LineValues]} -> % line begins with "=", ignore
{AccSectionName, AccValues};
{ok, [ValueName|LineValues]} -> % yeehaw, got a line!
RemainingLine = couch_util:implode(LineValues, "="),
{ok, [LineValue | _Rest]} = regexp:split(RemainingLine, " ;|\t;"), % removes comments
{AccSectionName, [{{AccSectionName, ValueName}, LineValue} | AccValues]}
end
end
end, {"", []}, Lines),
[ets:insert(?MODULE, {Key, Value}) || {Key, Value} <- ParsedIniValues],
ok.
% Unused gen_server behaviour API functions that we need to declare.
%% @doc Unused
handle_cast(foo, State) -> {noreply, State}.
handle_info({'DOWN', _, _, DownPid, _}, #config{notify_funs=PidFuns}=Config) ->
% remove any funs registered by the downed process
FilteredPidFuns = [{Pid,Fun} || {Pid,Fun} <- PidFuns, Pid /= DownPid],
{noreply, Config#config{notify_funs=FilteredPidFuns}}.
%% @doc Unused
terminate(_Reason, _State) -> ok.
%% @doc Unused
code_change(_OldVersion, State, _Extra) -> {ok, State}.
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