1%% 2%% %CopyrightBegin% 3%% 4%% Copyright Ericsson AB 1997-2016. All Rights Reserved. 5%% 6%% Licensed under the Apache License, Version 2.0 (the "License"); 7%% you may not use this file except in compliance with the License. 8%% You may obtain a copy of the License at 9%% 10%% http://www.apache.org/licenses/LICENSE-2.0 11%% 12%% Unless required by applicable law or agreed to in writing, software 13%% distributed under the License is distributed on an "AS IS" BASIS, 14%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15%% See the License for the specific language governing permissions and 16%% limitations under the License. 17%% 18%% %CopyrightEnd% 19%% 20 21%% 22-module(mnesia_config_backup). 23-author('peterl@erix.ericsson.se'). 24 25%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 26%% 27%% This module is used for testing the backup module config parameter. 28%% 29%% This module is an impostor for the mnesia_backup module. 30%% 31%% 32%% Original doc below: 33%% 34%% This module contains one implementation of callback functions 35%% used by Mnesia at backup and restore. The user may however 36%% write an own module the same interface as mnesia_backup and 37%% configure Mnesia so the alternate module performs the actual 38%% accesses to the backup media. This means that the user may put 39%% the backup on medias that Mnesia does not know about, possibly 40%% on hosts where Erlang is not running. 41%% 42%% The OpaqueData argument is never interpreted by other parts of 43%% Mnesia. It is the property of this module. Alternate implementations 44%% of this module may have different interpretations of OpaqueData. 45%% The OpaqueData argument given to open_write/1 and open_read/1 46%% are forwarded directly from the user. 47%% 48%% All functions must return {ok, NewOpaqueData} or {error, Reason}. 49%% 50%% The NewOpaqueData arguments returned by backup callback functions will 51%% be given as input when the next backup callback function is invoked. 52%% If any return value does not match {ok, _} the backup will be aborted. 53%% 54%% The NewOpaqueData arguments returned by restore callback functions will 55%% be given as input when the next restore callback function is invoked 56%% If any return value does not match {ok, _} the restore will be aborted. 57%% 58%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 59 60-export([ 61 open_write/1, write/2, commit_write/1, abort_write/1, 62 open_read/1, read/1, close_read/1 63 ]). 64 65-record(backup, {name, mode, items}). 66 67open_write(Name) -> 68 file:delete(Name), 69 {ok, #backup{name = Name, mode = write, items = []}}. 70 71write(Opaque, Item) when Opaque#backup.mode == write -> 72 %% Build the list in reverse order 73 {ok, Opaque#backup{items = [Item | Opaque#backup.items]}}. 74 75commit_write(Opaque) when Opaque#backup.mode == write -> 76 Bin = term_to_binary(Opaque#backup.items), 77 case file:write_file(Opaque#backup.name, Bin) of 78 ok -> 79 {ok, Opaque#backup{mode = closed, items = []}}; 80 {error, Reason} -> 81 {error, {commit_write, Reason}} 82 end. 83 84abort_write(Opaque) -> 85 {ok, Opaque#backup{mode = closed, items = []}}. 86 87open_read(Name) -> 88 case file:read_file(Name) of 89 {ok, Bin} -> 90 ReverseList = binary_to_term(Bin), 91 List = lists:reverse(ReverseList), 92 {ok, #backup{name = Name, mode = read, items = List}}; 93 {error, Reason} -> 94 %% {error, {open_read, Reason}} 95 {Reason, error} %% Testing error handling in mnesia 96 end. 97 98read(Opaque) when Opaque#backup.mode == read -> 99 case Opaque#backup.items of 100 [Head | Tail] -> 101 {ok, Opaque#backup{items = Tail}, Head}; 102 [] -> 103 {ok, Opaque#backup{mode = closed}, []} 104 end. 105 106close_read(Opaque) -> 107 {ok, Opaque#backup{mode = closed, items = []}}. 108