Refine the queue code

2 files changed, 25 insertions, 6 deletions

diff --git a/lib/ssl/src/ssl_connection.erl b/lib/ssl/src/ssl_connection.erl
index af9f0cbf3a..b3b1dc18dc 100644
--- a/lib/ssl/src/ssl_connection.erl
+++ b/lib/ssl/src/ssl_connection.erl
@@ -673,7 +673,18 @@ read_application_dist_data(DHandle, Front0, BufferSize, Rear0, Bin0) ->
 iovec_from_front(0, Front, Rear, Acc) ->
     {lists:reverse(Acc),Front,Rear};
 iovec_from_front(Size, [], Rear, Acc) ->
-    iovec_from_front(Size, lists:reverse(Rear), [], Acc);
+    case Rear of
+        %% Avoid lists:reverse/1 for simple cases.
+        %% Case clause for [] to avoid infinite loop.
+        [_] ->
+            iovec_from_front(Size, Rear, [], Acc);
+        [Bin2,Bin1] ->
+            iovec_from_front(Size, [Bin1,Bin2], [], Acc);
+        [Bin3,Bin2,Bin1] ->
+            iovec_from_front(Size, [Bin1,Bin2,Bin3], [], Acc);
+        [_,_,_|_] = Rear ->
+            iovec_from_front(Size, lists:reverse(Rear), [], Acc)
+    end;
 iovec_from_front(Size, [Bin|Front], Rear, Acc) ->
     case Bin of
         <<Last:Size/binary>> -> % Just enough
diff --git a/lib/ssl/src/tls_record.erl b/lib/ssl/src/tls_record.erl
index afbf95948d..20598ea702 100644
--- a/lib/ssl/src/tls_record.erl
+++ b/lib/ssl/src/tls_record.erl
@@ -495,11 +495,19 @@ binary_from_front(SplitSize, {Front,Size,Rear}) when SplitSize =< Size ->
     binary_from_front(SplitSize, Front, Size, Rear, []).
 %%
 %% SplitSize > 0 and there is at least SplitSize bytes buffered in Front and Rear
-binary_from_front(SplitSize, [], Size, [_] = Rear, Acc) ->
-    %% Optimize a simple case - avoid lists:reverse/1
-    binary_from_front(SplitSize, Rear, Size, [], Acc);
-binary_from_front(SplitSize, [], Size, [_|_] = Rear, Acc) ->
-    binary_from_front(SplitSize, lists:reverse(Rear), Size, [], Acc);
+binary_from_front(SplitSize, [], Size, Rear, Acc) ->
+    case Rear of
+        %% Avoid lists:reverse/1 for simple cases.
+        %% Case clause for [] to avoid infinite loop.
+        [_] ->
+            binary_from_front(SplitSize, Rear, Size, [], Acc);
+        [Bin2,Bin1] ->
+            binary_from_front(SplitSize, [Bin1,Bin2], Size, [], Acc);
+        [Bin3,Bin2,Bin1] ->
+            binary_from_front(SplitSize, [Bin1,Bin2,Bin3], Size, [], Acc);
+        [_,_,_|_] ->
+            binary_from_front(SplitSize, lists:reverse(Rear), Size, [], Acc)
+    end;
 binary_from_front(SplitSize, [Bin|Front], Size, Rear, []) ->
     %% Optimize the frequent case when the accumulator is empty
     BinSize = byte_size(Bin),