Alternate scale factor

Also had failed unit test - there was an issue with bit-flipping the position not being safely caught

src/leveled_penciller.erl

@@ -200,9 +200,14 @@
 
 -include_lib("eunit/include/eunit.hrl").
 
--define(LEVEL_SCALEFACTOR, [{0, 0}, {1, 8}, {2, 64}, {3, 512},
+-define(LEVEL_SCALEFACTOR, 
-                            {4, 4096}, {5, 32768}, {6, 262144},
+            [{0, 0}, {1, 4}, {2, 16}, {3, 64}, {4, 512}, 
-                            {7, infinity}]).
+                {5, 4096}, {6, 32768}, {7, infinity}]).
+            % As an alternative to going up by a factor of 8 at each level, 
+            % increase by a factor of 4 at young levels - to make early  
+            % compaction jobs shorter.  A trillion keys is still supported
+            % before hitting the infinite level.  At > 10 trillion keys
+            % behaviour may become increasingly difficult to predict.
 -define(MAX_LEVELS, 8).
 -define(MAX_WORK_WAIT, 300).
 -define(MANIFEST_FP, "ledger_manifest").

src/leveled_sst.erl

@@ -1518,8 +1518,11 @@ crc_check_slot(FullBin) ->
     <<CRC32PBL:32/integer, 
         PosBL:32/integer, 
         CRC32H:32/integer,
-        Header:PosBL/binary, 
+        Rest/binary>> = FullBin,
-        Blocks/binary>> = FullBin,
+    PosBL0 = min(PosBL, byte_size(FullBin) - 4), 
+        % If the position has been bit-flipped to beyond the maximum paossible
+        % length, use the maximum possible length
+    <<Header:PosBL0/binary, Blocks/binary>> = Rest,
     case {hmac(Header), hmac(PosBL)} of 
         {CRC32H, CRC32PBL} ->
             {Header, Blocks};