The R13B03 release.OTP_R13B03

1 files changed, 201 insertions, 0 deletions

diff --git a/lib/mnesia/src/mnesia_backup.erl b/lib/mnesia/src/mnesia_backup.erl
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+%%
+%% %CopyrightBegin%
+%% 
+%% Copyright Ericsson AB 1996-2009. All Rights Reserved.
+%% 
+%% The contents of this file are subject to the Erlang Public License,
+%% Version 1.1, (the "License"); you may not use this file except in
+%% compliance with the License. You should have received a copy of the
+%% Erlang Public License along with this software. If not, it can be
+%% retrieved online at http://www.erlang.org/.
+%% 
+%% Software distributed under the License is distributed on an "AS IS"
+%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+%% the License for the specific language governing rights and limitations
+%% under the License.
+%% 
+%% %CopyrightEnd%
+%%
+
+%%
+
+%%-behaviour(mnesia_backup).
+%0
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%
+%% 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.
+%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+-module(mnesia_backup).
+
+-include_lib("kernel/include/file.hrl").
+
+-export([
+	 %% Write access
+         open_write/1, 
+	 write/2, 
+	 commit_write/1, 
+	 abort_write/1,
+
+	 %% Read access
+         open_read/1, 
+	 read/1, 
+	 close_read/1
+        ]).
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% Backup callback interface
+-record(backup, {tmp_file, file, file_desc}).
+
+%% Opens backup media for write
+%%
+%% Returns {ok, OpaqueData} or {error, Reason}
+open_write(OpaqueData) ->
+    File = OpaqueData,
+    Tmp = lists:concat([File,".BUPTMP"]),
+    file:delete(Tmp),
+    file:delete(File),
+    case disk_log:open([{name, make_ref()},
+			{file, Tmp},
+			{repair, false},
+			{linkto, self()}]) of
+	{ok, Fd} ->
+	    {ok, #backup{tmp_file = Tmp, file = File, file_desc = Fd}};
+	{error, Reason} ->
+	    {error, Reason}
+    end.
+
+%% Writes BackupItems to the backup media
+%%
+%% Returns {ok, OpaqueData} or {error, Reason}
+write(OpaqueData, BackupItems) ->
+    B = OpaqueData,
+    case disk_log:log_terms(B#backup.file_desc, BackupItems) of
+        ok ->
+            {ok, B};
+        {error, Reason} ->
+            abort_write(B),
+            {error, Reason}
+    end.
+
+%% Closes the backup media after a successful backup
+%%
+%% Returns {ok, ReturnValueToUser} or {error, Reason}
+commit_write(OpaqueData) ->
+    B = OpaqueData,
+    case disk_log:sync(B#backup.file_desc) of
+        ok ->
+            case disk_log:close(B#backup.file_desc) of
+                ok ->
+		    case file:rename(B#backup.tmp_file, B#backup.file) of
+		       ok ->
+			    {ok, B#backup.file};
+		       {error, Reason} ->
+			    {error, Reason}
+		    end;
+                {error, Reason} ->
+		    {error, Reason}
+            end;
+        {error, Reason} ->
+            {error, Reason}
+    end.
+
+%% Closes the backup media after an interrupted backup
+%%
+%% Returns {ok, ReturnValueToUser} or {error, Reason}
+abort_write(BackupRef) ->
+    Res = disk_log:close(BackupRef#backup.file_desc),
+    file:delete(BackupRef#backup.tmp_file),
+    case Res of
+        ok ->
+            {ok, BackupRef#backup.file};
+        {error, Reason} ->
+            {error, Reason}
+    end.
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% Restore callback interface
+
+-record(restore, {file, file_desc, cont}).
+
+%% Opens backup media for read
+%%
+%% Returns {ok, OpaqueData} or {error, Reason}
+open_read(OpaqueData) ->
+    File = OpaqueData,
+    case file:read_file_info(File) of
+	{error, Reason} ->
+	    {error, Reason};
+	_FileInfo -> %% file exists
+	    case disk_log:open([{file, File},
+				{name, make_ref()},
+				{repair, false},
+				{mode, read_only},
+				{linkto, self()}]) of
+		{ok, Fd} ->
+		    {ok, #restore{file = File, file_desc = Fd, cont = start}};
+		{repaired, Fd, _, {badbytes, 0}} ->
+		    {ok, #restore{file = File, file_desc = Fd, cont = start}};
+		{repaired, Fd, _, _} ->
+		    {ok, #restore{file = File, file_desc = Fd, cont = start}};
+		{error, Reason} ->
+		    {error, Reason}
+	    end
+    end.
+
+%% Reads BackupItems from the backup media
+%%
+%% Returns {ok, OpaqueData, BackupItems} or {error, Reason}
+%%
+%% BackupItems == [] is interpreted as eof
+read(OpaqueData) ->
+    R = OpaqueData,
+    Fd = R#restore.file_desc,
+    case disk_log:chunk(Fd, R#restore.cont) of
+        {error, Reason} ->
+            {error, {"Possibly truncated", Reason}};
+        eof ->
+            {ok, R, []};
+        {Cont, []} ->
+            read(R#restore{cont = Cont});
+        {Cont, BackupItems, _BadBytes} ->
+            {ok, R#restore{cont = Cont}, BackupItems};
+        {Cont, BackupItems} ->
+            {ok, R#restore{cont = Cont}, BackupItems}
+    end.
+
+%% Closes the backup media after restore
+%%
+%% Returns {ok, ReturnValueToUser} or {error, Reason}
+close_read(OpaqueData) ->
+    R = OpaqueData,
+    case disk_log:close(R#restore.file_desc) of
+        ok -> {ok, R#restore.file};
+        {error, Reason} -> {error, Reason}
+    end.
+%0
+