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// SPDX-License-Identifier: MIT
pragma solidity >0.5.0 <0.8.0;
/* Library Imports */
import { Lib_BytesUtils } from "./Lib_BytesUtils.sol";
import { Lib_RLPReader } from "./Lib_RLPReader.sol";
import { Lib_RLPWriter } from "./Lib_RLPWriter.sol";
import "hardhat/console.sol";
/**
* @title Lib_MerkleTrie
*/
library Lib_MerkleTrie {
/*******************
* Data Structures *
*******************/
enum NodeType {
BranchNode,
ExtensionNode,
LeafNode
}
struct TrieNode {
bytes encoded;
Lib_RLPReader.RLPItem[] decoded;
}
/**********************
* Contract Constants *
**********************/
// TREE_RADIX determines the number of elements per branch node.
uint256 constant TREE_RADIX = 16;
// Branch nodes have TREE_RADIX elements plus an additional `value` slot.
uint256 constant BRANCH_NODE_LENGTH = TREE_RADIX + 1;
// Leaf nodes and extension nodes always have two elements, a `path` and a `value`.
uint256 constant LEAF_OR_EXTENSION_NODE_LENGTH = 2;
// Prefixes are prepended to the `path` within a leaf or extension node and
// allow us to differentiate between the two node types. `ODD` or `EVEN` is
// determined by the number of nibbles within the unprefixed `path`. If the
// number of nibbles if even, we need to insert an extra padding nibble so
// the resulting prefixed `path` has an even number of nibbles.
uint8 constant PREFIX_EXTENSION_EVEN = 0;
uint8 constant PREFIX_EXTENSION_ODD = 1;
uint8 constant PREFIX_LEAF_EVEN = 2;
uint8 constant PREFIX_LEAF_ODD = 3;
// Just a utility constant. RLP represents `NULL` as 0x80.
bytes1 constant RLP_NULL = bytes1(0x80);
bytes constant RLP_NULL_BYTES = hex'80';
bytes32 constant internal KECCAK256_RLP_NULL_BYTES = keccak256(RLP_NULL_BYTES);
/**********************
* Internal Functions *
**********************/
/**
* @notice Updates a Merkle trie and returns a new root hash.
* @param _key Key of the node to update, as a hex string.
* @param _value Value of the node to update, as a hex string.
* @param trie Merkle trie
* @param _root Known root of the Merkle trie. Used to verify that the
* included proof is correctly constructed.
* @return _updatedRoot Root hash of the newly constructed trie.
*/
function update(
bytes memory _key,
bytes memory _value,
mapping(bytes32 => bytes) storage trie,
bytes32 _root
)
internal
returns (
bytes32 _updatedRoot
)
{
// Special case when inserting the very first node.
if (_root == KECCAK256_RLP_NULL_BYTES) {
return getSingleNodeRootHash(_key, _value, trie);
}
(TrieNode[] memory proof, uint256 pathLength, bytes memory keyRemainder, ) = _walkNodePath(trie, _key, _root);
TrieNode[] memory newPath = _getNewPath(proof, pathLength, _key, keyRemainder, _value);
return _getUpdatedTrieRoot(newPath, _key, trie);
}
function getRawNode(bytes memory encoded) private pure returns (TrieNode memory) {
return TrieNode({
encoded: encoded,
decoded: Lib_RLPReader.readList(encoded)
});
}
function getTrieNode(mapping(bytes32 => bytes) storage trie, bytes32 nodeId) private view returns (TrieNode memory) {
bytes memory encoded = trie[nodeId];
require(keccak256(encoded) == nodeId, "bad hash in trie lookup");
return getRawNode(encoded);
}
/**
* @notice Retrieves the value associated with a given key.
* @param _key Key to search for, as hex bytes.
* @param trie Merkle trie
* @param _root Known root of the Merkle trie.
* @return _exists Whether or not the key exists.
* @return _value Value of the key if it exists.
*/
function get(
bytes memory _key,
mapping(bytes32 => bytes) storage trie,
bytes32 _root
)
internal
view
returns (
bool _exists,
bytes memory _value
)
{
(TrieNode[] memory proof, uint256 pathLength, bytes memory keyRemainder, bool isFinalNode) = _walkNodePath(trie, _key, _root);
bool exists = keyRemainder.length == 0;
require(
exists || isFinalNode,
"Provided proof is invalid."
);
bytes memory value = exists ? _getNodeValue(proof[pathLength - 1]) : bytes('');
return (
exists,
value
);
}
/**
* Computes the root hash for a trie with a single node.
* @param _key Key for the single node.
* @param _value Value for the single node.
* @return _updatedRoot Hash of the trie.
*/
function getSingleNodeRootHash(
bytes memory _key,
bytes memory _value,
mapping(bytes32 => bytes) storage trie
)
internal
returns (
bytes32 _updatedRoot
)
{
bytes memory dat = _makeLeafNode(
Lib_BytesUtils.toNibbles(_key),
_value).encoded;
bytes32 ret = keccak256(dat);
trie[ret] = dat;
return ret;
}
/*********************
* Private Functions *
*********************/
/**
* @notice Walks through a proof using a provided key.
* @param trie Merkle trie
* @param _key Key to use for the walk.
* @param _root Known root of the trie.
* @return _proof The proof
* @return _pathLength Length of the final path
* @return _keyRemainder Portion of the key remaining after the walk.
* @return _isFinalNode Whether or not we've hit a dead end.
*/
function _walkNodePath(
mapping(bytes32 => bytes) storage trie,
bytes memory _key,
bytes32 _root
)
private
view
returns (
TrieNode[] memory _proof,
uint256 _pathLength,
bytes memory _keyRemainder,
bool _isFinalNode
)
{
// TODO: this is max length
_proof = new TrieNode[](16);
uint256 pathLength = 0;
bytes memory key = Lib_BytesUtils.toNibbles(_key);
bytes32 currentNodeID = _root;
uint256 currentNodeLength = 32;
uint256 currentKeyIndex = 0;
uint256 currentKeyIncrement = 0;
TrieNode memory currentNode;
// Proof is top-down, so we start at the first element (root).
while (true) {
if (currentNodeID == bytes32(RLP_NULL)) {
break;
}
if (currentNodeLength >= 32) {
currentNode = getTrieNode(trie, currentNodeID);
} else {
currentNode = getRawNode(Lib_BytesUtils.slice(abi.encodePacked(currentNodeID), 0, currentNodeLength));
}
_proof[pathLength] = currentNode;
currentKeyIndex += currentKeyIncrement;
// Keep track of the proof elements we actually need.
// It's expensive to resize arrays, so this simply reduces gas costs.
pathLength += 1;
if (currentKeyIndex == 0) {
// First proof element is always the root node.
require(
keccak256(currentNode.encoded) == currentNodeID,
"Invalid root hash"
);
} else if (currentNode.encoded.length >= 32) {
// Nodes 32 bytes or larger are hashed inside branch nodes.
require(
keccak256(currentNode.encoded) == currentNodeID,
"Invalid large internal hash"
);
} else {
// Nodes smaller than 31 bytes aren't hashed.
require(
Lib_BytesUtils.toBytes32(currentNode.encoded) == currentNodeID,
"Invalid internal node hash"
);
}
if (currentNode.decoded.length == BRANCH_NODE_LENGTH) {
if (currentKeyIndex == key.length) {
// We've hit the end of the key, meaning the value should be within this branch node.
break;
} else {
// We're not at the end of the key yet.
// Figure out what the next node ID should be and continue.
uint8 branchKey = uint8(key[currentKeyIndex]);
Lib_RLPReader.RLPItem memory nextNode = currentNode.decoded[branchKey];
(currentNodeID, currentNodeLength) = _getNodeID(nextNode);
currentKeyIncrement = 1;
continue;
}
} else if (currentNode.decoded.length == LEAF_OR_EXTENSION_NODE_LENGTH) {
bytes memory path = _getNodePath(currentNode);
uint8 prefix = uint8(path[0]);
uint8 offset = 2 - prefix % 2;
bytes memory pathRemainder = Lib_BytesUtils.slice(path, offset);
bytes memory keyRemainder = Lib_BytesUtils.slice(key, currentKeyIndex);
uint256 sharedNibbleLength = _getSharedNibbleLength(pathRemainder, keyRemainder);
if (prefix == PREFIX_LEAF_EVEN || prefix == PREFIX_LEAF_ODD) {
if (
pathRemainder.length == sharedNibbleLength &&
keyRemainder.length == sharedNibbleLength
) {
// The key within this leaf matches our key exactly.
// Increment the key index to reflect that we have no remainder.
currentKeyIndex += sharedNibbleLength;
}
// We've hit a leaf node, so our next node should be NULL.
currentNodeID = bytes32(RLP_NULL);
break;
} else if (prefix == PREFIX_EXTENSION_EVEN || prefix == PREFIX_EXTENSION_ODD) {
if (sharedNibbleLength != pathRemainder.length) {
// Our extension node is not identical to the remainder.
// We've hit the end of this path
// updates will need to modify this extension.
currentNodeID = bytes32(RLP_NULL);
break;
} else {
// Our extension shares some nibbles.
// Carry on to the next node.
(currentNodeID, currentNodeLength) = _getNodeID(currentNode.decoded[1]);
currentKeyIncrement = sharedNibbleLength;
continue;
}
} else {
revert("Received a node with an unknown prefix");
}
} else {
revert("Received an unparseable node.");
}
}
// If our node ID is NULL, then we're at a dead end.
bool isFinalNode = currentNodeID == bytes32(RLP_NULL);
return (_proof, pathLength, Lib_BytesUtils.slice(key, currentKeyIndex), isFinalNode);
}
/**
* @notice Creates new nodes to support a k/v pair insertion into a given Merkle trie path.
* @param _path Path to the node nearest the k/v pair.
* @param _pathLength Length of the path. Necessary because the provided path may include
* additional nodes (e.g., it comes directly from a proof) and we can't resize in-memory
* arrays without costly duplication.
* @param _key Full original key.
* @param _keyRemainder Portion of the initial key that must be inserted into the trie.
* @param _value Value to insert at the given key.
* @return _newPath A new path with the inserted k/v pair and extra supporting nodes.
*/
function _getNewPath(
TrieNode[] memory _path,
uint256 _pathLength,
bytes memory _key,
bytes memory _keyRemainder,
bytes memory _value
)
private
returns (
TrieNode[] memory _newPath
)
{
bytes memory keyRemainder = _keyRemainder;
// Most of our logic depends on the status of the last node in the path.
TrieNode memory lastNode = _path[_pathLength - 1];
NodeType lastNodeType = _getNodeType(lastNode);
// Create an array for newly created nodes.
// We need up to three new nodes, depending on the contents of the last node.
// Since array resizing is expensive, we'll keep track of the size manually.
// We're using an explicit `totalNewNodes += 1` after insertions for clarity.
TrieNode[] memory newNodes = new TrieNode[](3);
uint256 totalNewNodes = 0;
// solhint-disable-next-line max-line-length
// Reference: https://github.com/ethereumjs/merkle-patricia-tree/blob/c0a10395aab37d42c175a47114ebfcbd7efcf059/src/baseTrie.ts#L294-L313
// TODO: do we need this?
bool matchLeaf = false;
if (lastNodeType == NodeType.LeafNode) {
uint256 l = 0;
if (_pathLength > 0) {
for (uint256 i = 0; i < _pathLength - 1; i++) {
if (_getNodeType(_path[i]) == NodeType.BranchNode) {
l++;
} else {
l += _getNodeKey(_path[i]).length;
}
}
}
if (
_getSharedNibbleLength(
_getNodeKey(lastNode),
Lib_BytesUtils.slice(Lib_BytesUtils.toNibbles(_key), l)
) == _getNodeKey(lastNode).length
&& keyRemainder.length == 0
) {
matchLeaf = true;
}
}
if (matchLeaf) {
// We've found a leaf node with the given key.
// Simply need to update the value of the node to match.
newNodes[totalNewNodes] = _makeLeafNode(_getNodeKey(lastNode), _value);
totalNewNodes += 1;
} else if (lastNodeType == NodeType.BranchNode) {
if (keyRemainder.length == 0) {
// We've found a branch node with the given key.
// Simply need to update the value of the node to match.
newNodes[totalNewNodes] = _editBranchValue(lastNode, _value);
totalNewNodes += 1;
} else {
// We've found a branch node, but it doesn't contain our key.
// Reinsert the old branch for now.
newNodes[totalNewNodes] = lastNode;
totalNewNodes += 1;
// Create a new leaf node, slicing our remainder since the first byte points
// to our branch node.
newNodes[totalNewNodes] = _makeLeafNode(Lib_BytesUtils.slice(keyRemainder, 1), _value);
totalNewNodes += 1;
}
} else {
// Our last node is either an extension node or a leaf node with a different key.
bytes memory lastNodeKey = _getNodeKey(lastNode);
uint256 sharedNibbleLength = _getSharedNibbleLength(lastNodeKey, keyRemainder);
if (sharedNibbleLength != 0) {
// We've got some shared nibbles between the last node and our key remainder.
// We'll need to insert an extension node that covers these shared nibbles.
bytes memory nextNodeKey = Lib_BytesUtils.slice(lastNodeKey, 0, sharedNibbleLength);
newNodes[totalNewNodes] = _makeExtensionNode(nextNodeKey, _getNodeHash(_value));
totalNewNodes += 1;
// Cut down the keys since we've just covered these shared nibbles.
lastNodeKey = Lib_BytesUtils.slice(lastNodeKey, sharedNibbleLength);
keyRemainder = Lib_BytesUtils.slice(keyRemainder, sharedNibbleLength);
}
// Create an empty branch to fill in.
TrieNode memory newBranch = _makeEmptyBranchNode();
if (lastNodeKey.length == 0) {
// Key remainder was larger than the key for our last node.
// The value within our last node is therefore going to be shifted into
// a branch value slot.
newBranch = _editBranchValue(newBranch, _getNodeValue(lastNode));
} else {
// Last node key was larger than the key remainder.
// We're going to modify some index of our branch.
uint8 branchKey = uint8(lastNodeKey[0]);
// Move on to the next nibble.
lastNodeKey = Lib_BytesUtils.slice(lastNodeKey, 1);
if (lastNodeType == NodeType.LeafNode) {
// We're dealing with a leaf node.
// We'll modify the key and insert the old leaf node into the branch index.
TrieNode memory modifiedLastNode = _makeLeafNode(lastNodeKey, _getNodeValue(lastNode));
newBranch = _editBranchIndex(newBranch, branchKey, _getNodeHash(modifiedLastNode.encoded));
} else if (lastNodeKey.length != 0) {
// We're dealing with a shrinking extension node.
// We need to modify the node to decrease the size of the key.
TrieNode memory modifiedLastNode = _makeExtensionNode(lastNodeKey, _getNodeValue(lastNode));
newBranch = _editBranchIndex(newBranch, branchKey, _getNodeHash(modifiedLastNode.encoded));
} else {
// We're dealing with an unnecessary extension node.
// We're going to delete the node entirely.
// Simply insert its current value into the branch index.
console.log(lastNode.decoded.length);
newBranch = _editBranchIndex(newBranch, branchKey, _getNodeValue(lastNode));
}
}
if (keyRemainder.length == 0) {
// We've got nothing left in the key remainder.
// Simply insert the value into the branch value slot.
newBranch = _editBranchValue(newBranch, _value);
// Push the branch into the list of new nodes.
newNodes[totalNewNodes] = newBranch;
totalNewNodes += 1;
} else {
// We've got some key remainder to work with.
// We'll be inserting a leaf node into the trie.
// First, move on to the next nibble.
keyRemainder = Lib_BytesUtils.slice(keyRemainder, 1);
// Push the branch into the list of new nodes.
newNodes[totalNewNodes] = newBranch;
totalNewNodes += 1;
// Push a new leaf node for our k/v pair.
newNodes[totalNewNodes] = _makeLeafNode(keyRemainder, _value);
totalNewNodes += 1;
}
}
// Finally, join the old path with our newly created nodes.
// Since we're overwriting the last node in the path, we use `_pathLength - 1`.
return _joinNodeArrays(_path, _pathLength - 1, newNodes, totalNewNodes);
}
/**
* @notice Computes the trie root from a given path.
* @param _nodes Path to some k/v pair.
* @param _key Key for the k/v pair.
* @return _updatedRoot Root hash for the updated trie.
*/
function _getUpdatedTrieRoot(
TrieNode[] memory _nodes,
bytes memory _key,
mapping(bytes32 => bytes) storage trie
)
private
returns (
bytes32 _updatedRoot
)
{
bytes memory key = Lib_BytesUtils.toNibbles(_key);
// Some variables to keep track of during iteration.
TrieNode memory currentNode;
NodeType currentNodeType;
bytes memory previousNodeHash;
// Run through the path backwards to rebuild our root hash.
for (uint256 i = _nodes.length; i > 0; i--) {
// Pick out the current node.
currentNode = _nodes[i - 1];
currentNodeType = _getNodeType(currentNode);
if (currentNodeType == NodeType.LeafNode) {
// Leaf nodes are already correctly encoded.
// Shift the key over to account for the nodes key.
bytes memory nodeKey = _getNodeKey(currentNode);
key = Lib_BytesUtils.slice(key, 0, key.length - nodeKey.length);
} else if (currentNodeType == NodeType.ExtensionNode) {
// Shift the key over to account for the nodes key.
bytes memory nodeKey = _getNodeKey(currentNode);
key = Lib_BytesUtils.slice(key, 0, key.length - nodeKey.length);
// If this node is the last element in the path, it'll be correctly encoded
// and we can skip this part.
if (previousNodeHash.length > 0) {
// Re-encode the node based on the previous node.
currentNode = _editExtensionNodeValue(currentNode, previousNodeHash);
}
} else if (currentNodeType == NodeType.BranchNode) {
// If this node is the last element in the path, it'll be correctly encoded
// and we can skip this part.
if (previousNodeHash.length > 0) {
// Re-encode the node based on the previous node.
uint8 branchKey = uint8(key[key.length - 1]);
key = Lib_BytesUtils.slice(key, 0, key.length - 1);
currentNode = _editBranchIndex(currentNode, branchKey, previousNodeHash);
}
}
// Compute the node hash for the next iteration.
previousNodeHash = _getNodeHash(currentNode.encoded);
if (currentNode.encoded.length >= 32) {
trie[keccak256(currentNode.encoded)] = currentNode.encoded;
}
}
// Current node should be the root at this point.
// Simply return the hash of its encoding.
return keccak256(currentNode.encoded);
}
/**
* @notice Parses an RLP-encoded proof into something more useful.
* @param _proof RLP-encoded proof to parse.
* @return _parsed Proof parsed into easily accessible structs.
*/
function _parseProof(
bytes memory _proof
)
private
pure
returns (
TrieNode[] memory _parsed
)
{
Lib_RLPReader.RLPItem[] memory nodes = Lib_RLPReader.readList(_proof);
TrieNode[] memory proof = new TrieNode[](nodes.length);
for (uint256 i = 0; i < nodes.length; i++) {
bytes memory encoded = Lib_RLPReader.readBytes(nodes[i]);
proof[i] = TrieNode({
encoded: encoded,
decoded: Lib_RLPReader.readList(encoded)
});
}
return proof;
}
/**
* @notice Picks out the ID for a node. Node ID is referred to as the
* "hash" within the specification, but nodes < 32 bytes are not actually
* hashed.
* @param _node Node to pull an ID for.
* @return _nodeID ID for the node, depending on the size of its contents.
*/
function _getNodeID(
Lib_RLPReader.RLPItem memory _node
)
private
pure
returns (
bytes32 _nodeID,
uint length
)
{
bytes memory nodeID;
if (_node.length < 32) {
// Nodes smaller than 32 bytes are RLP encoded.
nodeID = Lib_RLPReader.readRawBytes(_node);
} else {
// Nodes 32 bytes or larger are hashed.
nodeID = Lib_RLPReader.readBytes(_node);
}
return (Lib_BytesUtils.toBytes32(nodeID), _node.length);
}
/**
* @notice Gets the path for a leaf or extension node.
* @param _node Node to get a path for.
* @return _path Node path, converted to an array of nibbles.
*/
function _getNodePath(
TrieNode memory _node
)
private
pure
returns (
bytes memory _path
)
{
return Lib_BytesUtils.toNibbles(Lib_RLPReader.readBytes(_node.decoded[0]));
}
/**
* @notice Gets the key for a leaf or extension node. Keys are essentially
* just paths without any prefix.
* @param _node Node to get a key for.
* @return _key Node key, converted to an array of nibbles.
*/
function _getNodeKey(
TrieNode memory _node
)
private
pure
returns (
bytes memory _key
)
{
return _removeHexPrefix(_getNodePath(_node));
}
/**
* @notice Gets the path for a node.
* @param _node Node to get a value for.
* @return _value Node value, as hex bytes.
*/
function _getNodeValue(
TrieNode memory _node
)
private
pure
returns (
bytes memory _value
)
{
return Lib_RLPReader.readBytes(_node.decoded[_node.decoded.length - 1]);
}
/**
* @notice Computes the node hash for an encoded node. Nodes < 32 bytes
* are not hashed, all others are keccak256 hashed.
* @param _encoded Encoded node to hash.
* @return _hash Hash of the encoded node. Simply the input if < 32 bytes.
*/
function _getNodeHash(
bytes memory _encoded
)
private
pure
returns (
bytes memory _hash
)
{
if (_encoded.length < 32) {
return _encoded;
} else {
return abi.encodePacked(keccak256(_encoded));
}
}
/**
* @notice Determines the type for a given node.
* @param _node Node to determine a type for.
* @return _type Type of the node; BranchNode/ExtensionNode/LeafNode.
*/
function _getNodeType(
TrieNode memory _node
)
private
pure
returns (
NodeType _type
)
{
if (_node.decoded.length == BRANCH_NODE_LENGTH) {
return NodeType.BranchNode;
} else if (_node.decoded.length == LEAF_OR_EXTENSION_NODE_LENGTH) {
bytes memory path = _getNodePath(_node);
uint8 prefix = uint8(path[0]);
if (prefix == PREFIX_LEAF_EVEN || prefix == PREFIX_LEAF_ODD) {
return NodeType.LeafNode;
} else if (prefix == PREFIX_EXTENSION_EVEN || prefix == PREFIX_EXTENSION_ODD) {
return NodeType.ExtensionNode;
}
}
revert("Invalid node type");
}
/**
* @notice Utility; determines the number of nibbles shared between two
* nibble arrays.
* @param _a First nibble array.
* @param _b Second nibble array.
* @return _shared Number of shared nibbles.
*/
function _getSharedNibbleLength(
bytes memory _a,
bytes memory _b
)
private
pure
returns (
uint256 _shared
)
{
uint256 i = 0;
while (_a.length > i && _b.length > i && _a[i] == _b[i]) {
i++;
}
return i;
}
/**
* @notice Utility; converts an RLP-encoded node into our nice struct.
* @param _raw RLP-encoded node to convert.
* @return _node Node as a TrieNode struct.
*/
function _makeNode(
bytes[] memory _raw
)
private
pure
returns (
TrieNode memory _node
)
{
bytes memory encoded = Lib_RLPWriter.writeList(_raw);
return TrieNode({
encoded: encoded,
decoded: Lib_RLPReader.readList(encoded)
});
}
/**
* @notice Utility; converts an RLP-decoded node into our nice struct.
* @param _items RLP-decoded node to convert.
* @return _node Node as a TrieNode struct.
*/
function _makeNode(
Lib_RLPReader.RLPItem[] memory _items
)
private
pure
returns (
TrieNode memory _node
)
{
bytes[] memory raw = new bytes[](_items.length);
for (uint256 i = 0; i < _items.length; i++) {
raw[i] = Lib_RLPReader.readRawBytes(_items[i]);
}
return _makeNode(raw);
}
/**
* @notice Creates a new extension node.
* @param _key Key for the extension node, unprefixed.
* @param _value Value for the extension node.
* @return _node New extension node with the given k/v pair.
*/
function _makeExtensionNode(
bytes memory _key,
bytes memory _value
)
private
pure
returns (
TrieNode memory _node
)
{
bytes[] memory raw = new bytes[](2);
bytes memory key = _addHexPrefix(_key, false);
raw[0] = Lib_RLPWriter.writeBytes(Lib_BytesUtils.fromNibbles(key));
raw[1] = Lib_RLPWriter.writeBytes(_value);
return _makeNode(raw);
}
/**
* Creates a new extension node with the same key but a different value.
* @param _node Extension node to copy and modify.
* @param _value New value for the extension node.
* @return New node with the same key and different value.
*/
function _editExtensionNodeValue(
TrieNode memory _node,
bytes memory _value
)
private
pure
returns (
TrieNode memory
)
{
bytes[] memory raw = new bytes[](2);
bytes memory key = _addHexPrefix(_getNodeKey(_node), false);
raw[0] = Lib_RLPWriter.writeBytes(Lib_BytesUtils.fromNibbles(key));
if (_value.length < 32) {
raw[1] = _value;
} else {
raw[1] = Lib_RLPWriter.writeBytes(_value);
}
return _makeNode(raw);
}
/**
* @notice Creates a new leaf node.
* @dev This function is essentially identical to `_makeExtensionNode`.
* Although we could route both to a single method with a flag, it's
* more gas efficient to keep them separate and duplicate the logic.
* @param _key Key for the leaf node, unprefixed.
* @param _value Value for the leaf node.
* @return _node New leaf node with the given k/v pair.
*/
function _makeLeafNode(
bytes memory _key,
bytes memory _value
)
private
pure
returns (
TrieNode memory _node
)
{
bytes[] memory raw = new bytes[](2);
bytes memory key = _addHexPrefix(_key, true);
raw[0] = Lib_RLPWriter.writeBytes(Lib_BytesUtils.fromNibbles(key));
raw[1] = Lib_RLPWriter.writeBytes(_value);
return _makeNode(raw);
}
/**
* @notice Creates an empty branch node.
* @return _node Empty branch node as a TrieNode struct.
*/
function _makeEmptyBranchNode()
private
pure
returns (
TrieNode memory _node
)
{
bytes[] memory raw = new bytes[](BRANCH_NODE_LENGTH);
for (uint256 i = 0; i < raw.length; i++) {
raw[i] = RLP_NULL_BYTES;
}
return _makeNode(raw);
}
/**
* @notice Modifies the value slot for a given branch.
* @param _branch Branch node to modify.
* @param _value Value to insert into the branch.
* @return _updatedNode Modified branch node.
*/
function _editBranchValue(
TrieNode memory _branch,
bytes memory _value
)
private
pure
returns (
TrieNode memory _updatedNode
)
{
bytes memory encoded = Lib_RLPWriter.writeBytes(_value);
_branch.decoded[_branch.decoded.length - 1] = Lib_RLPReader.toRLPItem(encoded);
return _makeNode(_branch.decoded);
}
/**
* @notice Modifies a slot at an index for a given branch.
* @param _branch Branch node to modify.
* @param _index Slot index to modify.
* @param _value Value to insert into the slot.
* @return _updatedNode Modified branch node.
*/
function _editBranchIndex(
TrieNode memory _branch,
uint8 _index,
bytes memory _value
)
private
pure
returns (
TrieNode memory _updatedNode
)
{
bytes memory encoded = _value.length < 32 ? _value : Lib_RLPWriter.writeBytes(_value);
_branch.decoded[_index] = Lib_RLPReader.toRLPItem(encoded);
return _makeNode(_branch.decoded);
}
/**
* @notice Utility; adds a prefix to a key.
* @param _key Key to prefix.
* @param _isLeaf Whether or not the key belongs to a leaf.
* @return _prefixedKey Prefixed key.
*/
function _addHexPrefix(
bytes memory _key,
bool _isLeaf
)
private
pure
returns (
bytes memory _prefixedKey
)
{
uint8 prefix = _isLeaf ? uint8(0x02) : uint8(0x00);
uint8 offset = uint8(_key.length % 2);
bytes memory prefixed = new bytes(2 - offset);
prefixed[0] = bytes1(prefix + offset);
return abi.encodePacked(prefixed, _key);
}
/**
* @notice Utility; removes a prefix from a path.
* @param _path Path to remove the prefix from.
* @return _unprefixedKey Unprefixed key.
*/
function _removeHexPrefix(
bytes memory _path
)
private
pure
returns (
bytes memory _unprefixedKey
)
{
if (uint8(_path[0]) % 2 == 0) {
return Lib_BytesUtils.slice(_path, 2);
} else {
return Lib_BytesUtils.slice(_path, 1);
}
}
/**
* @notice Utility; combines two node arrays. Array lengths are required
* because the actual lengths may be longer than the filled lengths.
* Array resizing is extremely costly and should be avoided.
* @param _a First array to join.
* @param _aLength Length of the first array.
* @param _b Second array to join.
* @param _bLength Length of the second array.
* @return _joined Combined node array.
*/
function _joinNodeArrays(
TrieNode[] memory _a,
uint256 _aLength,
TrieNode[] memory _b,
uint256 _bLength
)
private
pure
returns (
TrieNode[] memory _joined
)
{
TrieNode[] memory ret = new TrieNode[](_aLength + _bLength);
// Copy elements from the first array.
for (uint256 i = 0; i < _aLength; i++) {
ret[i] = _a[i];
}
// Copy elements from the second array.
for (uint256 i = 0; i < _bLength; i++) {
ret[i + _aLength] = _b[i];
}
return ret;
}
}
\ No newline at end of file
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