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%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 1997-2010. All Rights Reserved.
%%
%% 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.
%%
%% %CopyrightEnd%
%%
%%
-module(mnesia_config_backup).
-author('[email protected]').
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%
%% This module is used for testing the backup module config parameter.
%%
%% This module is an impostor for the mnesia_backup module.
%%
%%
%% Original doc below:
%%
%% This module contains one implementation of callback functions
%% used by Mnesia at backup and restore. The user may however
%% write an own module the same interface as mnesia_backup and
%% configure Mnesia so the alternate module performs the actual
%% accesses to the backup media. This means that the user may put
%% the backup on medias that Mnesia does not know about, possibly
%% on hosts where Erlang is not running.
%%
%% The OpaqueData argument is never interpreted by other parts of
%% Mnesia. It is the property of this module. Alternate implementations
%% of this module may have different interpretations of OpaqueData.
%% The OpaqueData argument given to open_write/1 and open_read/1
%% are forwarded directly from the user.
%%
%% All functions must return {ok, NewOpaqueData} or {error, Reason}.
%%
%% The NewOpaqueData arguments returned by backup callback functions will
%% be given as input when the next backup callback function is invoked.
%% If any return value does not match {ok, _} the backup will be aborted.
%%
%% The NewOpaqueData arguments returned by restore callback functions will
%% be given as input when the next restore callback function is invoked
%% If any return value does not match {ok, _} the restore will be aborted.
%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-export([
open_write/1, write/2, commit_write/1, abort_write/1,
open_read/1, read/1, close_read/1
]).
-record(backup, {name, mode, items}).
open_write(Name) ->
file:delete(Name),
{ok, #backup{name = Name, mode = write, items = []}}.
write(Opaque, Item) when Opaque#backup.mode == write ->
%% Build the list in reverse order
{ok, Opaque#backup{items = [Item | Opaque#backup.items]}}.
commit_write(Opaque) when Opaque#backup.mode == write ->
Bin = term_to_binary(Opaque#backup.items),
case file:write_file(Opaque#backup.name, Bin) of
ok ->
{ok, Opaque#backup{mode = closed, items = []}};
{error, Reason} ->
{error, {commit_write, Reason}}
end.
abort_write(Opaque) ->
{ok, Opaque#backup{mode = closed, items = []}}.
open_read(Name) ->
case file:read_file(Name) of
{ok, Bin} ->
ReverseList = binary_to_term(Bin),
List = lists:reverse(ReverseList),
{ok, #backup{name = Name, mode = read, items = List}};
{error, Reason} ->
%% {error, {open_read, Reason}}
{Reason, error} %% Testing error handling in mnesia
end.
read(Opaque) when Opaque#backup.mode == read ->
case Opaque#backup.items of
[Head | Tail] ->
{ok, Opaque#backup{items = Tail}, Head};
[] ->
{ok, Opaque#backup{mode = closed}, []}
end.
close_read(Opaque) ->
{ok, Opaque#backup{mode = closed, items = []}}.
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