Merge pull request #31 from NIC619/bintrie_update

Bintrie update on key-being-prefix-of-another-key problem

README.md

@@ -115,6 +115,11 @@ True
 False
 ```
 
+## BinaryTrie
+- Note: One drawback of Binary Trie is that **one key can not be the prefix of another key**. For example,
+if you already set the value `value1` with key `key1`, you can not set another value with key `key` or `key11`
+and the like.
+
 ### BinaryTrie branch and witness helper functions
 
 ```python

tests/test_bin_trie.py

@@ -13,7 +13,7 @@
     BLANK_HASH,
 )
 from trie.exceptions import (
-    LeafNodeOverrideError,
+    NodeOverrideError,
 )
 
 
@@ -67,7 +67,7 @@ def test_bin_trie_delete_subtrie(kv1, kv2, key_to_be_deleted, will_delete, will_
         assert trie.root_hash == BLANK_HASH
     else:
         if will_rasie_error:
-            with pytest.raises(LeafNodeOverrideError):
+            with pytest.raises(NodeOverrideError):
                 trie.delete_subtrie(key_to_be_deleted)
         else:
             root_hash_before_delete = trie.root_hash
@@ -94,7 +94,7 @@ def test_bin_trie_invalid_key(invalide_key, if_error):
 
     assert trie.get(invalide_key) is None
     if if_error:
-        with pytest.raises(LeafNodeOverrideError):
+        with pytest.raises(NodeOverrideError):
             trie.delete(invalide_key)
     else:
         previous_root_hash = trie.root_hash

trie/binary.py

@@ -15,7 +15,7 @@
     validate_is_bin_node,
 )
 from trie.exceptions import (
-    LeafNodeOverrideError,
+    NodeOverrideError,
 )
 
 from trie.utils.sha3 import (
@@ -116,9 +116,9 @@ def _set(self, node_hash, keypath, value, if_delete_subtrie=False):
         if nodetype == LEAF_TYPE:
             # Keypath must match, there should be no remaining keypath
             if keypath:
-                raise LeafNodeOverrideError(
-                    "Existing kv pair is being effaced because"
-                    " it's key is the prefix of the new key")
+                raise NodeOverrideError(
+                    "Fail to set the value because the prefix of it's key"
+                    " is the same as existing key")
             if if_delete_subtrie:
                 return BLANK_HASH
             return self._hash_and_save(encode_leaf_node(value)) if value else BLANK_HASH
@@ -211,6 +211,10 @@ def _set_kv_node(
             # Case 2: keypath prefixes mismatch in the middle, so we need to break
             # the keypath in half. We are in case (3), (4), (7), (8)
             else:
+                if len(keypath[common_prefix_len + 1:]) == 0:
+                    raise NodeOverrideError(
+                        "Fail to set the value because it's key"
+                        " is the prefix of other existing key")
                 valnode = self._hash_and_save(
                     encode_kv_node(
                         keypath[common_prefix_len + 1:],
@@ -256,6 +260,10 @@ def _set_branch_node(
             if_delete_subtrie=False):
         # Which child node to update? Depends on first bit in keypath
         if keypath[:1] == BYTE_0:
+            if len(keypath[1:]) == 0:
+                raise NodeOverrideError(
+                    "Fail to set the value because it's key"
+                    " is the prefix of other existing key")
             new_left_child = self._set(left_child, keypath[1:], value, if_delete_subtrie)
             new_right_child = right_child
         else:

trie/exceptions.py

@@ -14,7 +14,7 @@ class BadTrieProof(Exception):
     pass
 
 
-class LeafNodeOverrideError(Exception):
+class NodeOverrideError(Exception):
     pass