ethereum.homestead.trie
State Trie ^^^^^^^^^^
.. contents:: Table of Contents :backlinks: none :local:
Introduction
The state trie is the structure responsible for storing
.fork_types.Account
objects.
EMPTY_TRIE_ROOT
59 | EMPTY_TRIE_ROOT = Root( |
---|---|
60 | hex_to_bytes( |
61 | "56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421" |
62 | ) |
63 | ) |
Node
65 | Node = Account | Bytes | Transaction | Receipt | Uint | U256 | None |
---|
K
66 | K = TypeVar("K", bound=Bytes) |
---|
V
67 | V = TypeVar( |
---|---|
68 | "V", |
69 | Optional[Account], |
70 | Optional[Bytes], |
71 | Bytes, |
72 | Optional[Transaction], |
73 | Optional[Receipt], |
74 | Uint, |
75 | U256, |
76 | ) |
LeafNode
Leaf node in the Merkle Trie
79 | @slotted_freezable |
---|
80 | @dataclass |
---|
class LeafNode:
rest_of_key
84 | rest_of_key: Bytes |
---|
value
85 | value: Extended |
---|
ExtensionNode
Extension node in the Merkle Trie
88 | @slotted_freezable |
---|
89 | @dataclass |
---|
class ExtensionNode:
key_segment
93 | key_segment: Bytes |
---|
subnode
94 | subnode: Extended |
---|
BranchSubnodes
97 | BranchSubnodes = Tuple[ |
---|---|
98 | Extended, |
99 | Extended, |
100 | Extended, |
101 | Extended, |
102 | Extended, |
103 | Extended, |
104 | Extended, |
105 | Extended, |
106 | Extended, |
107 | Extended, |
108 | Extended, |
109 | Extended, |
110 | Extended, |
111 | Extended, |
112 | Extended, |
113 | Extended, |
114 | ] |
BranchNode
Branch node in the Merkle Trie
117 | @slotted_freezable |
---|
118 | @dataclass |
---|
class BranchNode:
subnodes
122 | subnodes: BranchSubnodes |
---|
value
123 | value: Extended |
---|
InternalNode
126 | InternalNode = LeafNode | ExtensionNode | BranchNode |
---|
encode_internal_node
Encodes a Merkle Trie node into its RLP form. The RLP will then be
serialized into a Bytes
and hashed unless it is less that 32 bytes
when serialized.
This function also accepts None
, representing the absence of a node,
which is encoded to b""
.
Parameters
node : Optional[InternalNode] The node to encode.
Returns
encoded : rlp.RLP
The node encoded as RLP.
def encode_internal_node(node: Optional[InternalNode]) -> Extended:
130 | """ |
---|---|
131 | Encodes a Merkle Trie node into its RLP form. The RLP will then be |
132 | serialized into a `Bytes` and hashed unless it is less that 32 bytes |
133 | when serialized. |
134 |
|
135 | This function also accepts `None`, representing the absence of a node, |
136 | which is encoded to `b""`. |
137 |
|
138 | Parameters |
139 | ---------- |
140 | node : Optional[InternalNode] |
141 | The node to encode. |
142 |
|
143 | Returns |
144 | ------- |
145 | encoded : `rlp.RLP` |
146 | The node encoded as RLP. |
147 | """ |
148 | unencoded: Extended |
149 | if node is None: |
150 | unencoded = b"" |
151 | elif isinstance(node, LeafNode): |
152 | unencoded = ( |
153 | nibble_list_to_compact(node.rest_of_key, True), |
154 | node.value, |
155 | ) |
156 | elif isinstance(node, ExtensionNode): |
157 | unencoded = ( |
158 | nibble_list_to_compact(node.key_segment, False), |
159 | node.subnode, |
160 | ) |
161 | elif isinstance(node, BranchNode): |
162 | unencoded = list(node.subnodes) + [node.value] |
163 | else: |
164 | raise AssertionError(f"Invalid internal node type {type(node)}!") |
165 | |
166 | encoded = rlp.encode(unencoded) |
167 | if len(encoded) < 32: |
168 | return unencoded |
169 | else: |
170 | return keccak256(encoded) |
encode_node
Encode a Node for storage in the Merkle Trie.
Currently mostly an unimplemented stub.
def encode_node(node: Node, storage_root: Optional[Bytes]) -> Bytes:
174 | """ |
---|---|
175 | Encode a Node for storage in the Merkle Trie. |
176 |
|
177 | Currently mostly an unimplemented stub. |
178 | """ |
179 | if isinstance(node, Account): |
180 | assert storage_root is not None |
181 | return encode_account(node, storage_root) |
182 | elif isinstance(node, (Transaction, Receipt, U256)): |
183 | return rlp.encode(node) |
184 | elif isinstance(node, Bytes): |
185 | return node |
186 | else: |
187 | return previous_trie.encode_node(node, storage_root) |
Trie
The Merkle Trie.
190 | @dataclass |
---|
class Trie:
secured
196 | secured: bool |
---|
default
197 | default: V |
---|
_data
198 | _data: Dict[K, V] = field(default_factory=dict) |
---|
copy_trie
Create a copy of trie
. Since only frozen objects may be stored in tries,
the contents are reused.
Parameters
trie: Trie
Trie to copy.
Returns
new_trie : Trie[K, V]
A copy of the trie.
def copy_trie(trie: Trie[K, V]) -> Trie[K, V]:
202 | """ |
---|---|
203 | Create a copy of `trie`. Since only frozen objects may be stored in tries, |
204 | the contents are reused. |
205 |
|
206 | Parameters |
207 | ---------- |
208 | trie: `Trie` |
209 | Trie to copy. |
210 |
|
211 | Returns |
212 | ------- |
213 | new_trie : `Trie[K, V]` |
214 | A copy of the trie. |
215 | """ |
216 | return Trie(trie.secured, trie.default, copy.copy(trie._data)) |
trie_set
Stores an item in a Merkle Trie.
This method deletes the key if value == trie.default
, because the Merkle
Trie represents the default value by omitting it from the trie.
Parameters
trie: Trie
Trie to store in.
key : Bytes
Key to lookup.
value : V
Node to insert at key
.
def trie_set(trie: Trie[K, V], key: K, value: V) -> None:
220 | """ |
---|---|
221 | Stores an item in a Merkle Trie. |
222 |
|
223 | This method deletes the key if `value == trie.default`, because the Merkle |
224 | Trie represents the default value by omitting it from the trie. |
225 |
|
226 | Parameters |
227 | ---------- |
228 | trie: `Trie` |
229 | Trie to store in. |
230 | key : `Bytes` |
231 | Key to lookup. |
232 | value : `V` |
233 | Node to insert at `key`. |
234 | """ |
235 | if value == trie.default: |
236 | if key in trie._data: |
237 | del trie._data[key] |
238 | else: |
239 | trie._data[key] = value |
trie_get
Gets an item from the Merkle Trie.
This method returns trie.default
if the key is missing.
Parameters
trie: Trie to lookup in. key : Key to lookup.
Returns
node : V
Node at key
in the trie.
def trie_get(trie: Trie[K, V], key: K) -> V:
243 | """ |
---|---|
244 | Gets an item from the Merkle Trie. |
245 |
|
246 | This method returns `trie.default` if the key is missing. |
247 |
|
248 | Parameters |
249 | ---------- |
250 | trie: |
251 | Trie to lookup in. |
252 | key : |
253 | Key to lookup. |
254 |
|
255 | Returns |
256 | ------- |
257 | node : `V` |
258 | Node at `key` in the trie. |
259 | """ |
260 | return trie._data.get(key, trie.default) |
common_prefix_length
Find the longest common prefix of two sequences.
def common_prefix_length(a: Sequence, b: Sequence) -> int:
264 | """ |
---|---|
265 | Find the longest common prefix of two sequences. |
266 | """ |
267 | for i in range(len(a)): |
268 | if i >= len(b) or a[i] != b[i]: |
269 | return i |
270 | return len(a) |
nibble_list_to_compact
Compresses nibble-list into a standard byte array with a flag.
A nibble-list is a list of byte values no greater than 15
. The flag is
encoded in high nibble of the highest byte. The flag nibble can be broken
down into two two-bit flags.
Highest nibble::
+---+---+----------+--------+
| _ | _ | is_leaf | parity |
+---+---+----------+--------+
3 2 1 0
The lowest bit of the nibble encodes the parity of the length of the
remaining nibbles -- 0
when even and 1
when odd. The second lowest bit
is used to distinguish leaf and extension nodes. The other two bits are not
used.
Parameters
x : Array of nibbles. is_leaf : True if this is part of a leaf node, or false if it is an extension node.
Returns
compressed : bytearray
Compact byte array.
def nibble_list_to_compact(x: Bytes, is_leaf: bool) -> Bytes:
274 | """ |
---|---|
275 | Compresses nibble-list into a standard byte array with a flag. |
276 |
|
277 | A nibble-list is a list of byte values no greater than `15`. The flag is |
278 | encoded in high nibble of the highest byte. The flag nibble can be broken |
279 | down into two two-bit flags. |
280 |
|
281 | Highest nibble:: |
282 |
|
283 | +---+---+----------+--------+ |
284 | | _ | _ | is_leaf | parity | |
285 | +---+---+----------+--------+ |
286 | 3 2 1 0 |
287 |
|
288 |
|
289 | The lowest bit of the nibble encodes the parity of the length of the |
290 | remaining nibbles -- `0` when even and `1` when odd. The second lowest bit |
291 | is used to distinguish leaf and extension nodes. The other two bits are not |
292 | used. |
293 |
|
294 | Parameters |
295 | ---------- |
296 | x : |
297 | Array of nibbles. |
298 | is_leaf : |
299 | True if this is part of a leaf node, or false if it is an extension |
300 | node. |
301 |
|
302 | Returns |
303 | ------- |
304 | compressed : `bytearray` |
305 | Compact byte array. |
306 | """ |
307 | compact = bytearray() |
308 | |
309 | if len(x) % 2 == 0: # ie even length |
310 | compact.append(16 * (2 * is_leaf)) |
311 | for i in range(0, len(x), 2): |
312 | compact.append(16 * x[i] + x[i + 1]) |
313 | else: |
314 | compact.append(16 * ((2 * is_leaf) + 1) + x[0]) |
315 | for i in range(1, len(x), 2): |
316 | compact.append(16 * x[i] + x[i + 1]) |
317 | |
318 | return Bytes(compact) |
bytes_to_nibble_list
Converts a Bytes
into to a sequence of nibbles (bytes with value < 16).
Parameters
bytes_:
The Bytes
to convert.
Returns
nibble_list : Bytes
The Bytes
in nibble-list format.
def bytes_to_nibble_list(bytes_: Bytes) -> Bytes:
322 | """ |
---|---|
323 | Converts a `Bytes` into to a sequence of nibbles (bytes with value < 16). |
324 |
|
325 | Parameters |
326 | ---------- |
327 | bytes_: |
328 | The `Bytes` to convert. |
329 |
|
330 | Returns |
331 | ------- |
332 | nibble_list : `Bytes` |
333 | The `Bytes` in nibble-list format. |
334 | """ |
335 | nibble_list = bytearray(2 * len(bytes_)) |
336 | for byte_index, byte in enumerate(bytes_): |
337 | nibble_list[byte_index * 2] = (byte & 0xF0) >> 4 |
338 | nibble_list[byte_index * 2 + 1] = byte & 0x0F |
339 | return Bytes(nibble_list) |
_prepare_trie
Prepares the trie for root calculation. Removes values that are empty,
hashes the keys (if secured == True
) and encodes all the nodes.
Parameters
trie :
The Trie
to prepare.
get_storage_root :
Function to get the storage root of an account. Needed to encode
Account
objects.
Returns
out : Mapping[ethereum.base_types.Bytes, Node]
Object with keys mapped to nibble-byte form.
def _prepare_trie(trie: Trie[K, V], get_storage_root: Optional[Callable[[Address], Root]]) -> Mapping[Bytes, Bytes]:
346 | """ |
---|---|
347 | Prepares the trie for root calculation. Removes values that are empty, |
348 | hashes the keys (if `secured == True`) and encodes all the nodes. |
349 |
|
350 | Parameters |
351 | ---------- |
352 | trie : |
353 | The `Trie` to prepare. |
354 | get_storage_root : |
355 | Function to get the storage root of an account. Needed to encode |
356 | `Account` objects. |
357 |
|
358 | Returns |
359 | ------- |
360 | out : `Mapping[ethereum.base_types.Bytes, Node]` |
361 | Object with keys mapped to nibble-byte form. |
362 | """ |
363 | mapped: MutableMapping[Bytes, Bytes] = {} |
364 | |
365 | for preimage, value in trie._data.items(): |
366 | if isinstance(value, Account): |
367 | assert get_storage_root is not None |
368 | address = Address(preimage) |
369 | encoded_value = encode_node(value, get_storage_root(address)) |
370 | else: |
371 | encoded_value = encode_node(value) |
372 | if encoded_value == b"": |
373 | raise AssertionError |
374 | key: Bytes |
375 | if trie.secured: |
376 | # "secure" tries hash keys once before construction |
377 | key = keccak256(preimage) |
378 | else: |
379 | key = preimage |
380 | mapped[bytes_to_nibble_list(key)] = encoded_value |
381 | |
382 | return mapped |
root
Computes the root of a modified merkle patricia trie (MPT).
Parameters
trie :
Trie
to get the root of.
get_storage_root :
Function to get the storage root of an account. Needed to encode
Account
objects.
Returns
root : .fork_types.Root
MPT root of the underlying key-value pairs.
def root(trie: Trie[K, V], get_storage_root: Optional[Callable[[Address], Root]]) -> Root:
389 | """ |
---|---|
390 | Computes the root of a modified merkle patricia trie (MPT). |
391 |
|
392 | Parameters |
393 | ---------- |
394 | trie : |
395 | `Trie` to get the root of. |
396 | get_storage_root : |
397 | Function to get the storage root of an account. Needed to encode |
398 | `Account` objects. |
399 |
|
400 |
|
401 | Returns |
402 | ------- |
403 | root : `.fork_types.Root` |
404 | MPT root of the underlying key-value pairs. |
405 | """ |
406 | obj = _prepare_trie(trie, get_storage_root) |
407 | |
408 | root_node = encode_internal_node(patricialize(obj, Uint(0))) |
409 | if len(rlp.encode(root_node)) < 32: |
410 | return keccak256(rlp.encode(root_node)) |
411 | else: |
412 | assert isinstance(root_node, Bytes) |
413 | return Root(root_node) |
patricialize
Structural composition function.
Used to recursively patricialize and merkleize a dictionary. Includes memoization of the tree structure and hashes.
Parameters
obj : Underlying trie key-value pairs, with keys in nibble-list format. level : Current trie level.
Returns
node : ethereum.base_types.Bytes
Root node of obj
.
def patricialize(obj: Mapping[Bytes, Bytes], level: Uint) -> Optional[InternalNode]:
419 | """ |
---|---|
420 | Structural composition function. |
421 |
|
422 | Used to recursively patricialize and merkleize a dictionary. Includes |
423 | memoization of the tree structure and hashes. |
424 |
|
425 | Parameters |
426 | ---------- |
427 | obj : |
428 | Underlying trie key-value pairs, with keys in nibble-list format. |
429 | level : |
430 | Current trie level. |
431 |
|
432 | Returns |
433 | ------- |
434 | node : `ethereum.base_types.Bytes` |
435 | Root node of `obj`. |
436 | """ |
437 | if len(obj) == 0: |
438 | return None |
439 | |
440 | arbitrary_key = next(iter(obj)) |
441 | |
442 | # if leaf node |
443 | if len(obj) == 1: |
444 | leaf = LeafNode(arbitrary_key[level:], obj[arbitrary_key]) |
445 | return leaf |
446 | |
447 | # prepare for extension node check by finding max j such that all keys in |
448 | # obj have the same key[i:j] |
449 | substring = arbitrary_key[level:] |
450 | prefix_length = len(substring) |
451 | for key in obj: |
452 | prefix_length = min( |
453 | prefix_length, common_prefix_length(substring, key[level:]) |
454 | ) |
455 |
|
456 | # finished searching, found another key at the current level |
457 | if prefix_length == 0: |
458 | break |
459 | |
460 | # if extension node |
461 | if prefix_length > 0: |
462 | prefix = arbitrary_key[int(level) : int(level) + prefix_length] |
463 | return ExtensionNode( |
464 | prefix, |
465 | encode_internal_node( |
466 | patricialize(obj, level + Uint(prefix_length)) |
467 | ), |
468 | ) |
469 | |
470 | branches: List[MutableMapping[Bytes, Bytes]] = [] |
471 | for _ in range(16): |
472 | branches.append({}) |
473 | value = b"" |
474 | for key in obj: |
475 | if len(key) == level: |
476 | # shouldn't ever have an account or receipt in an internal node |
477 | if isinstance(obj[key], (Account, Receipt, Uint)): |
478 | raise AssertionError |
479 | value = obj[key] |
480 | else: |
481 | branches[key[level]][key] = obj[key] |
482 | |
483 | subnodes = tuple( |
484 | encode_internal_node(patricialize(branches[k], level + Uint(1))) |
485 | for k in range(16) |
486 | ) |
487 | return BranchNode( |
488 | cast(BranchSubnodes, assert_type(subnodes, Tuple[Extended, ...])), |
489 | value, |
490 | ) |