remove 17th elem code from branch node parser/encoder

stateless/tree_from_witness.nim

@@ -24,7 +24,7 @@ proc initTreeBuilder*(input: openArray[byte], db: DB): TreeBuilder =
   result.input = memoryInput(input)
   result.db = db
   result.root = emptyRlpHash
-  
+
 func rootHash*(t: TreeBuilder): KeccakHash {.inline.} =
   t.root
 
@@ -72,7 +72,7 @@ proc toNodeKey(z: openArray[byte]): NodeKey =
     result.data = keccak(z).data
     result.usedBytes = 32
 
-proc branchNode(t: var TreeBuilder, depth: int, has16Elem: bool = true): NodeKey
+proc branchNode(t: var TreeBuilder, depth: int): NodeKey
 proc extensionNode(t: var TreeBuilder, depth: int): NodeKey
 proc accountNode(t: var TreeBuilder, depth: int): NodeKey
 proc accountStorageLeafNode(t: var TreeBuilder, depth: int): NodeKey
@@ -84,7 +84,6 @@ proc treeNode*(t: var TreeBuilder, depth: int = 0, accountMode = false): NodeKey
 
   case nodeType
   of BranchNodeType: result = t.branchNode(depth)
-  of Branch17NodeType: result = t.branchNode(depth, false)
   of ExtensionNodeType: result = t.extensionNode(depth)
   of AccountNodeType:
     if accountMode:
@@ -98,7 +97,7 @@ proc treeNode*(t: var TreeBuilder, depth: int = 0, accountMode = false): NodeKey
     result.data = keccak(result.data.toOpenArray(0, result.usedBytes-1)).data
     result.usedBytes = 32
 
-proc branchNode(t: var TreeBuilder, depth: int, has16Elem: bool): NodeKey =
+proc branchNode(t: var TreeBuilder, depth: int): NodeKey =
   assert(depth < 64)
   let mask = constructBranchMask(t.readByte, t.readByte)
 
@@ -117,21 +116,8 @@ proc branchNode(t: var TreeBuilder, depth: int, has16Elem: bool): NodeKey =
     else:
       r.append ""
 
-  template safePeek(t: var TreeBuilder): int =
-    if t.len == 0 or has16Elem:
-      -1
-    else:
-      t.peek().int
-
-  # add the 17th elem
-  let nodeType = t.safePeek()
-  if nodeType == AccountNodeType.int:
-    r.append accountNode(t, depth+1)
-  elif nodeType == HashNodeType.int:
-    r.append hashNode(t)
-  else:
-    # anything else is empty
-    r.append ""
+  # 17th elem should always empty
+  r.append ""
 
   result = toNodeKey(r.finish)
 
@@ -175,7 +161,6 @@ proc extensionNode(t: var TreeBuilder, depth: int): NodeKey =
 
   case nodeType
   of BranchNodeType: r.append t.branchNode(depth + nibblesLen)
-  of Branch17NodeType: r.append t.branchNode(depth + nibblesLen, false)
   of HashNodeType: r.append t.hashNode()
   else: raise newException(ValueError, "wrong type during parsing child of extension node")
 

stateless/witness_from_tree.nim

@@ -73,10 +73,9 @@ proc writeExtensionNode(wb: var WitnessBuilder, n: NibblesSeq, depth: int, node:
 
 proc writeBranchNode(wb: var WitnessBuilder, mask: uint, depth: int, node: openArray[byte]) =
   # write type
-  if mask.branchMaskBitIsSet(16):
-    wb.output.append(Branch17NodeType.byte)
-  else:
-    wb.output.append(BranchNodeType.byte)
+  # branch node 17th elem should always empty
+  doAssert mask.branchMaskBitIsSet(16) == false
+  wb.output.append(BranchNodeType.byte)
   # write branch mask
   wb.output.append(((mask shr 8) and 0xFF).byte)
   wb.output.append((mask and 0xFF).byte)
@@ -121,9 +120,8 @@ proc writeShortNode(wb: var WitnessBuilder, node: openArray[byte], depth: int) =
         let nextLookup = branch.getNode
         writeShortNode(wb, nextLookup, depth + 1)
 
-    var lastElem = nodeRlp.listElem(16)
-    if not lastElem.isEmpty:
-      writeAccountNode(wb, lastElem.toBytes, depth)
+    # 17th elem should always empty
+    doAssert branchMask.branchMaskBitIsSet(16) == false
   else:
     raise newException(CorruptedTrieDatabase, "Bad Short Node")
 
@@ -165,15 +163,8 @@ proc getBranchRecurseAux(wb: var WitnessBuilder, node: openArray[byte], path: Ni
           else:
             writeHashNode(wb, branch.expectHash)
 
-    # put 17th elem
-    var lastElem = nodeRlp.listElem(16)
-    if not lastElem.isEmpty:
-      if path.len == 0:
-        doAssert(false, "ACC NODE A?")
-        writeAccountNode(wb, lastElem.toBytes, depth)
-      else:
-        doAssert(false, "HASH NODE B?")
-        writeHashNode(wb, lastElem.expectHash)
+    # 17th elem should always empty
+    doAssert branchMask.branchMaskBitIsSet(16) == false
   else:
     raise newException(CorruptedTrieDatabase,
                        "HexaryTrie node with an unexpected number of children")

stateless/witness_types.nim

@@ -3,7 +3,6 @@ import nimcrypto/[keccak, hash], stew/bitops2
 type
   TrieNodeType* = enum
     BranchNodeType
-    Branch17NodeType
     ExtensionNodeType
     AccountNodeType
     HashNodeType