WIP: intermediate refactoring

src/machi_projection_store.erl

@@ -267,18 +267,38 @@ do_proj_write(private=ProjType, #projection_v1{epoch_number=Epoch}=Proj, S) ->
     case S#state.max_public_epochid of
         {PublicEpoch, _} when PublicEpoch =< Epoch ->
             do_proj_write2(ProjType, Proj, S);
-        {PublicEpoch, _} ->
+        {_PublicEpoch, _} ->
             {{error, bad_arg}, S}
     end.
 
-do_proj_write2(ProjType, #projection_v1{epoch_number=Epoch}=Proj, S) ->
+do_proj_write2(ProjType, #projection_v1{epoch_csum=CSum}=Proj, S) ->
+    case (machi_projection:update_checksum(Proj))#projection_v1.epoch_csum of
+        CSum2 when CSum2 == CSum ->
+            do_proj_write3(ProjType, Proj, S);
+        _Else ->
+            io:format(user, "Oops ~s epoch ~w csum ~W expected ~W\n", [S#state.public_dir, Proj#projection_v1.epoch_number, _Else, 6, CSum, 6]),
+            {{error, bad_arg}, S}
+    end.
+
+do_proj_write3(ProjType, #projection_v1{epoch_number=Epoch,
+                                        epoch_csum=CSum}=Proj, S) ->
     %% TODO: We probably ought to check the projection checksum for sanity, eh?
     Dir = pick_path(ProjType, S),
     Path = filename:join(Dir, epoch2name(Epoch)),
-    case file:read_file_info(Path) of
-        {ok, _FI} ->
+    case file:read_file(Path) of
+        {ok, _Bin} when ProjType == public ->
+            {{error, written}, S};
+        {ok, Bin} when ProjType == private ->
+            #projection_v1{epoch_number=CurEpoch,
+                           epoch_csum=CurCSum} = _CurProj = binary_to_term(Bin),
             {{error, written}, S};
         {error, enoent} ->
+            do_proj_write4(ProjType, Proj, Path, Epoch, S);
+        {error, Else} ->
+            {{error, Else}, S}
+    end.
+
+do_proj_write4(ProjType, Proj, Path, Epoch, S) ->
     {ok, FH} = file:open(Path, [write, raw, binary]),
     ok = file:write(FH, term_to_binary(Proj)),
     ok = file:sync(FH),
@@ -312,10 +332,7 @@ do_proj_write2(ProjType, #projection_v1{epoch_number=Epoch}=Proj, S) ->
               true ->
                    S
            end,
-            {ok, NewS};
-        {error, Else} ->
-            {{error, Else}, S}
-    end.
+    {ok, NewS}.
 
 update_wedge_state(PidSpec, Boolean, {0,_}=EpochId) ->
     %% Epoch #0 is a special case: no projection has been written yet.

test/machi_projection_store_test.erl

@@ -41,6 +41,9 @@ smoke_test() ->
         ok = ?PS:write(a_pstore, public, P1),
         {error, written} = ?PS:write(a_pstore, public, P1),
 
+        Pbad = P1#projection_v1{epoch_number=99238}, % break checksum
+        {error, bad_arg} = ?PS:write(a_pstore, public, Pbad),
+
         ok = ?PS:write(a_pstore, private, P1),
         {error, written} = ?PS:write(a_pstore, private, P1),
         P1b = P1#projection_v1{dbg2=[version_b]},