Merge branch 'raimo/ssl/fix-zero-fragment-buffer-handling/ERIERL-379/OTP-15328' into maint

* raimo/ssl/fix-zero-fragment-buffer-handling/ERIERL-379/OTP-15328:
  Do not call dist_ctrl_put_data with empty binaries
  Refine the queue code
  Fix extracting 0 bytes from queue

1 files changed, 17 insertions, 6 deletions

diff --git a/lib/ssl/src/tls_record.erl b/lib/ssl/src/tls_record.erl
index a5c550a429..2aeab98929 100644
--- a/lib/ssl/src/tls_record.erl
+++ b/lib/ssl/src/tls_record.erl
@@ -514,16 +514,27 @@ validate_tls_record_length(Versions, {_,Size0,_} = Q0, SslOpts, Acc, Type, Versi
     end.
 
 
-binary_from_front(SplitSize, {Front,Size,Rear}) ->
+binary_from_front(0, Q) ->
+    {<<>>, Q};
+binary_from_front(SplitSize, {Front,Size,Rear}) when SplitSize =< Size ->
     binary_from_front(SplitSize, Front, Size, Rear, []).
 %%
-binary_from_front(SplitSize, [], Size, [_] = Rear, Acc) ->
-    %% Optimize a simple case
-    binary_from_front(SplitSize, Rear, Size, [], Acc);
+%% SplitSize > 0 and there is at least SplitSize bytes buffered in Front and Rear
 binary_from_front(SplitSize, [], Size, Rear, Acc) ->
-    binary_from_front(SplitSize, lists:reverse(Rear), Size, [], 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 a frequent case
+    %% Optimize the frequent case when the accumulator is empty
     BinSize = byte_size(Bin),
     if
         SplitSize < BinSize ->