MPT: Add support for "short" nodes

test/state/mpt.cpp

@@ -151,7 +151,7 @@ class MPTNode
 
     void insert(const Path& path, bytes&& value);
 
-    [[nodiscard]] hash256 hash() const;
+    [[nodiscard]] bytes encode() const;
 };
 
 void MPTNode::insert(const Path& path, bytes&& value)  // NOLINT(misc-no-recursion)
@@ -219,46 +219,49 @@ void MPTNode::insert(const Path& path, bytes&& value)  // NOLINT(misc-no-recursi
     }
 }
 
-hash256 MPTNode::hash() const  // NOLINT(misc-no-recursion)
+/// Encodes a node and optionally hashes the encoded bytes
+/// if their length exceeds the specified threshold.
+static bytes encode_child(const MPTNode& child) noexcept  // NOLINT(misc-no-recursion)
 {
+    if (auto e = child.encode(); e.size() < 32)
+        return e;  // "short" node
+    else
+        return rlp::encode(keccak256(e));
+}
+
+bytes MPTNode::encode() const  // NOLINT(misc-no-recursion)
+{
+    bytes encoded;
     switch (m_kind)
     {
     case Kind::leaf:
     {
-        return keccak256(rlp::encode_tuple(m_path.encode(false), m_value));
+        encoded = rlp::encode(m_path.encode(false)) + rlp::encode(m_value);
+        break;
     }
     case Kind::branch:
     {
         assert(m_path.length == 0);
+        static constexpr uint8_t empty = 0x80;  // encoded empty child
 
-        // Temporary storage for children hashes.
-        // The `bytes` type could be used instead, but this way dynamic allocation is avoided.
-        hash256 children_hashes[num_children];
-
-        // Views of children hash bytes.
-        // Additional always empty item is hash list terminator
-        // (required by the spec, although not needed for uniqueness).
-        bytes_view children_hash_bytes[num_children + 1];
-
-        for (size_t i = 0; i < num_children; ++i)
+        for (const auto& child : m_children)
         {
-            if (m_children[i])
-            {
-                children_hashes[i] = m_children[i]->hash();
-                children_hash_bytes[i] = children_hashes[i];
-            }
+            if (child)
+                encoded += encode_child(*child);
+            else
+                encoded += empty;
         }
-
-        return keccak256(rlp::encode(children_hash_bytes));
+        encoded += empty;  // end indicator
+        break;
     }
     case Kind::ext:
     {
-        return keccak256(rlp::encode_tuple(m_path.encode(true), m_children[0]->hash()));
+        encoded = rlp::encode(m_path.encode(true)) + encode_child(*m_children[0]);
+        break;
     }
     }
 
-    assert(false);
-    return {};
+    return rlp::internal::wrap_list(encoded);
 }
 
 
@@ -277,7 +280,7 @@ void MPT::insert(bytes_view key, bytes&& value)
 {
     if (m_root == nullptr)
         return emptyMPTHash;
-    return m_root->hash();
+    return keccak256(m_root->encode());
 }
 
 }  // namespace evmone::state

test/unittests/state_mpt_test.cpp

@@ -164,6 +164,9 @@ TEST(state_mpt, trie_topologies)
         const char* hash_hex;
     };
 
+    // The test cases are cross-checked with go-ethereum implementation.
+    // https://github.com/ethereum/go-ethereum/blob/7dea9c10cdb42e8c9f71b8b324cbe9222ab105cf/trie/stacktrie_test.go#L35
+
     // clang-format off
     const std::vector<KVH> tests[] = {
         { // {0:0, 7:0, f:0}
@@ -303,6 +306,38 @@ TEST(state_mpt, trie_topologies)
             {"123e", "x___________________________2", "0d230561e398c579e09a9f7b69ceaf7d3970f5a436fdb28b68b7a37c5bdd6b80"},
             {"13aa", "x___________________________3", "ff0dc70ce2e5db90ee42a4c2ad12139596b890e90eb4e16526ab38fa465b35cf"},
         },
+        { // branch node with short values
+            {"01", "a", "b48605025f5f4b129d40a420e721aa7d504487f015fce85b96e52126365ef7dc"},
+            {"80", "b", "2dc6b680daf74db067cb7aeaad73265ded93d96fce190fcbf64f498d475672ab"},
+            {"ee", "c", "017dc705a54ac5328dd263fa1bae68d655310fb3e3f7b7bc57e9a43ddf99c4bf"},
+            {"ff", "d", "bd5a3584d271d459bd4eb95247b2fc88656b3671b60c1125ffe7bc0b689470d0"},
+        },
+        { // ext node with short branch node, then becoming long
+            {"a0", "a", "a83e028cb1e4365935661a9fd36a5c65c30b9ab416eaa877424146ca2a69d088"},
+            {"a1", "b", "f586a4639b07b01798ca65e05c253b75d51135ebfbf6f8d6e87c0435089e65f0"},
+            {"a2", "c", "63e297c295c008e09a8d531e18d57f270b6bc403e23179b915429db948cd62e3"},
+            {"a3", "d", "94a7b721535578e9381f1f4e4b6ec29f8bdc5f0458a30320684c562f5d47b4b5"},
+            {"a4", "e", "4b7e66d1c81965cdbe8fab8295ef56bc57fefdc5733d4782d2f8baf630f083c6"},
+            {"a5", "f", "2997e7b502198ce1783b5277faacf52b25844fb55a99b63e88bdbbafac573106"},
+            {"a6", "g", "bee629dd27a40772b2e1a67ec6db270d26acdf8d3b674dfae27866ad6ae1f48b"},
+        },
+        { // branch node with short values, then long ones
+            {"a001", "v1", "b9cc982d995392b51e6787f1915f0b88efd4ad8b30f138da0a3e2242f2323e35"},
+            {"b002", "v2", "a7b474bc77ef5097096fa0ee6298fdae8928c0bc3724e7311cd0fa9ed1942fc7"},
+            {"c003", "v___________________________3", "dceb5bb7c92b0e348df988a8d9fc36b101397e38ebd405df55ba6ee5f14a264a"},
+            {"d004", "v___________________________4", "36e60ecb86b9626165e1c6543c42ecbe4d83bca58e8e1124746961511fce362a"},
+        },
+        { // ext node to branch node with short values, then long ones
+            {"8002", "v1", "3258fcb3e9e7d7234ecd3b8d4743999e4ab3a21592565e0a5ca64c141e8620d9"},
+            {"8004", "v2", "b6cb95b7024a83c17624a3c9bed09b4b5e8ed426f49f54b8ad13c39028b1e75a"},
+            {"8008", "v___________________________3", "c769d82963abe6f0900bf69754738eeb2f84559777cfa87a44f54e1aab417871"},
+            {"800d", "v___________________________4", "1cad1fdaab1a6fa95d7b780fd680030e423eb76669971368ba04797a8d9cdfc9"},
+        },
+        { // ext node with a child of size 31 (Y) and branch node with a child of size 31 (X)
+            {"000001", "ZZZZZZZZZ", "cef154b87c03c563408520ff9b26923c360cbc3ddb590c079bedeeb25a8c9c77"},
+            {"000002", "Y", "2130735e600f612f6e657a32bd7be64ddcaec6512c5694844b19de713922895d"},
+            {"000003", "XXXXXXXXXXXXXXXXXXXXXXXXXXXX", "962c0fffdeef7612a4f7bff1950d67e3e81c878e48b9ae45b3b374253b050bd8"},
+        },
     };
     // clang-format on