1 files changed, 44 insertions, 31 deletions

diff --git a/src/credit_flow.erl b/src/credit_flow.erl
index 9ffaf247..106179fd 100644
--- a/src/credit_flow.erl
+++ b/src/credit_flow.erl
@@ -52,6 +52,22 @@
 
 %%----------------------------------------------------------------------------
 
+%% process dict update macro - eliminates the performance-hurting
+%% closure creation a HOF would introduce
+-define(UPDATE(Key, Default, Var, Expr),
+        begin
+            %% We deliberately allow Var to escape from the case here
+            %% to be used in Expr. Any temporary var we introduced
+            %% would also escape, and might conflict.
+            case get(Key) of
+                undefined -> Var = Default;
+                Var       -> ok
+            end,
+            put(Key, Expr)
+        end).
+
+%%----------------------------------------------------------------------------
+
 %% There are two "flows" here; of messages and of credit, going in
 %% opposite directions. The variable names "From" and "To" refer to
 %% the flow of credit, but the function names refer to the flow of
@@ -66,29 +82,33 @@
 send(From) -> send(From, ?DEFAULT_CREDIT).
 
 send(From, {InitialCredit, _MoreCreditAfter}) ->
-    update({credit_from, From}, InitialCredit,
-           fun (1) -> block(From),
-                      0;
-               (C) -> C - 1
-           end).
+    ?UPDATE({credit_from, From}, InitialCredit, C,
+            if C == 1 -> block(From),
+                         0;
+               true   -> C - 1
+            end).
 
 ack(To) -> ack(To, ?DEFAULT_CREDIT).
 
 ack(To, {_InitialCredit, MoreCreditAfter}) ->
-    update({credit_to, To}, MoreCreditAfter,
-           fun (1) -> grant(To, MoreCreditAfter),
-                      MoreCreditAfter;
-               (C) -> C - 1
-           end).
+    ?UPDATE({credit_to, To}, MoreCreditAfter, C,
+            if C == 1 -> grant(To, MoreCreditAfter),
+                         MoreCreditAfter;
+               true   -> C - 1
+            end).
 
 handle_bump_msg({From, MoreCredit}) ->
-    update({credit_from, From}, 0,
-           fun (C) when C =< 0 andalso C + MoreCredit > 0 -> unblock(From),
-                                                             C + MoreCredit;
-               (C)                                        -> C + MoreCredit
-           end).
-
-blocked() -> get(credit_blocked, []) =/= [].
+    ?UPDATE({credit_from, From}, 0, C,
+            if C =< 0 andalso C + MoreCredit > 0 -> unblock(From),
+                                                    C + MoreCredit;
+               true                              -> C + MoreCredit
+            end).
+
+blocked() -> case get(credit_blocked) of
+                 undefined -> false;
+                 []        -> false;
+                 _         -> true
+             end.
 
 peer_down(Peer) ->
     %% In theory we could also remove it from credit_deferred here, but it
@@ -105,24 +125,17 @@ grant(To, Quantity) ->
     Msg = {bump_credit, {self(), Quantity}},
     case blocked() of
         false -> To ! Msg;
-        true  -> update(credit_deferred, [],
-                        fun (Deferred) -> [{To, Msg} | Deferred] end)
+        true  -> ?UPDATE(credit_deferred, [], Deferred, [{To, Msg} | Deferred])
     end.
 
-block(From) -> update(credit_blocked, [], fun (Blocks) -> [From | Blocks] end).
+block(From) -> ?UPDATE(credit_blocked, [], Blocks, [From | Blocks]).
 
 unblock(From) ->
-    update(credit_blocked, [], fun (Blocks) -> Blocks -- [From] end),
+    ?UPDATE(credit_blocked, [], Blocks, Blocks -- [From]),
     case blocked() of
-        false -> [To ! Msg || {To, Msg} <- get(credit_deferred, [])],
-                 erase(credit_deferred);
+        false -> case erase(credit_deferred) of
+                     undefined -> ok;
+                     Credits   -> [To ! Msg || {To, Msg} <- Credits]
+                 end;
         true  -> ok
     end.
-
-get(Key, Default) ->
-    case get(Key) of
-        undefined -> Default;
-        Value     -> Value
-    end.
-
-update(Key, Default, Fun) -> put(Key, Fun(get(Key, Default))), ok.