stdlib: Add 'sync' option to ets:tab2file/3

to improve the chance of some real disk persistence
before tab2file returns.

3 files changed, 44 insertions, 20 deletions

diff --git a/lib/stdlib/doc/src/ets.xml b/lib/stdlib/doc/src/ets.xml
index 3df24bf688..256dd21b01 100644
--- a/lib/stdlib/doc/src/ets.xml
+++ b/lib/stdlib/doc/src/ets.xml
@@ -1429,7 +1429,9 @@ is_integer(X), is_integer(Y), X + Y < 4711]]></code>
 	<p>Whenever the <c>extended_info</c> option is used, it
 	results in a file not readable by versions of ets prior to
 	that in stdlib-1.15.1</p> 
-
+        <p>The <c>sync</c> option, if set to <c>true</c>, ensures that
+	the content of the file is actually written to the disk before
+	<c>tab2file</c> returns. Default is <c>{sync, false}</c>.</p>
       </desc>
     </func>
     <func>
diff --git a/lib/stdlib/src/ets.erl b/lib/stdlib/src/ets.erl
index 93c4f59896..964286c431 100644
--- a/lib/stdlib/src/ets.erl
+++ b/lib/stdlib/src/ets.erl
@@ -695,7 +695,8 @@ do_filter(Tab, Key, F, A, Ack) ->
 -record(filetab_options,
 	{
 	  object_count = false :: boolean(),
-	  md5sum       = false :: boolean()     
+	  md5sum       = false :: boolean(),
+	  sync         = false :: boolean()
 	 }).
 
 -spec tab2file(Tab, Filename) -> 'ok' | {'error', Reason} when
@@ -710,7 +711,7 @@ tab2file(Tab, File) ->
       Tab :: tab(),
       Filename :: file:name(),
       Options :: [Option],
-      Option :: {'extended_info', [ExtInfo]},
+      Option :: {'extended_info', [ExtInfo]} | {'sync', boolean()},
       ExtInfo :: 'md5sum' | 'object_count',
       Reason :: term().
 
@@ -791,6 +792,15 @@ tab2file(Tab, File, Options) ->
 		List ->
 		    LogFun(NewState1,[['$end_of_table',List]])
 	    end,
+	    case FtOptions#filetab_options.sync of
+	        true ->
+		    case disk_log:sync(Name) of
+		        ok -> ok;
+			{error, Reason2} -> throw(Reason2)
+		    end;
+                false ->
+		    ok
+            end,
 	    disk_log:close(Name)
 	catch
 	    throw:TReason ->
@@ -843,23 +853,24 @@ md5terms(State, [H|T]) ->
     {FinState, [B|TL]}.
 
 parse_ft_options(Options) when is_list(Options) ->
-    {Opt,Rest} = case (catch lists:keytake(extended_info,1,Options)) of
-		     false -> 
-			 {[],Options};
-		     {value,{extended_info,L},R} when is_list(L) ->
-			 {L,R}
-		 end,
-    case Rest of
-	[] ->
-	    parse_ft_info_options(#filetab_options{}, Opt);
-	Other ->
-	    throw({unknown_option, Other})
-    end;
-parse_ft_options(Malformed) ->
+    {ok, parse_ft_options(Options, #filetab_options{}, false)}.
+
+parse_ft_options([], FtOpt, _) ->
+    FtOpt;
+parse_ft_options([{sync,true} | Rest], FtOpt, EI) ->
+    parse_ft_options(Rest, FtOpt#filetab_options{sync = true}, EI);
+parse_ft_options([{sync,false} | Rest], FtOpt, EI) ->
+    parse_ft_options(Rest, FtOpt, EI);
+parse_ft_options([{extended_info,L} | Rest], FtOpt0, false) ->
+    FtOpt1 = parse_ft_info_options(FtOpt0, L),
+    parse_ft_options(Rest, FtOpt1, true);
+parse_ft_options([Other | _], _, _) ->
+    throw({unknown_option, Other});
+parse_ft_options(Malformed, _, _) ->
     throw({malformed_option, Malformed}).
 
 parse_ft_info_options(FtOpt,[]) ->
-    {ok,FtOpt};
+    FtOpt;
 parse_ft_info_options(FtOpt,[object_count | T]) ->
     parse_ft_info_options(FtOpt#filetab_options{object_count = true}, T);
 parse_ft_info_options(FtOpt,[md5sum | T]) ->
diff --git a/lib/stdlib/test/ets_SUITE.erl b/lib/stdlib/test/ets_SUITE.erl
index 8dc8b2c291..7eadc4ab02 100644
--- a/lib/stdlib/test/ets_SUITE.erl
+++ b/lib/stdlib/test/ets_SUITE.erl
@@ -3969,12 +3969,22 @@ tab2file(doc) -> ["Check the ets:tab2file function on an empty "
 		  "ets table."];
 tab2file(suite) -> [];
 tab2file(Config) when is_list(Config) ->
+    ?line FName = filename:join([?config(priv_dir, Config),"tab2file_case"]),
+    tab2file_do(FName, []),
+    tab2file_do(FName, [{sync,true}]),
+    tab2file_do(FName, [{sync,false}]),
+    {'EXIT',{{badmatch,{error,_}},_}} = (catch tab2file_do(FName, [{sync,yes}])),
+    {'EXIT',{{badmatch,{error,_}},_}} = (catch tab2file_do(FName, [sync])),
+    ok.
+
+tab2file_do(FName, Opts) ->
     %% Write an empty ets table to a file, read back and check properties.
     ?line Tab = ets_new(ets_SUITE_foo_tab, [named_table, set, private,
 					    {keypos, 2}]),
-    ?line FName = filename:join([?config(priv_dir, Config),"tab2file_case"]),
-    ?line ok = ets:tab2file(Tab, FName),
-    ?line true = ets:delete(Tab),
+    catch file:delete(FName),
+    Res = ets:tab2file(Tab, FName, Opts),
+    true = ets:delete(Tab),
+    ok = Res,
     %
     ?line EtsMem = etsmem(),
     ?line {ok, Tab2} = ets:file2tab(FName),
@@ -3984,6 +3994,7 @@ tab2file(Config) when is_list(Config) ->
     ?line set = ets:info(Tab2, type),
     ?line true = ets:delete(Tab2),
     ?line verify_etsmem(EtsMem).
+
     
 tab2file2(doc) -> ["Check the ets:tab2file function on a ",
 		   "filled set/bag type ets table."];