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fixed issue with __buildTree arguments #4

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fixed issue with __buildTree arguments #4

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82 changes: 41 additions & 41 deletions merkleTree.py
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Original file line number Diff line number Diff line change
Expand Up @@ -12,15 +12,15 @@ def __init__(self, data):
self.data = data
self.left = None
self.right = None

#utility function to check if a given node has 2 children
def isFull(self):
return self.left and self.right

#utility function to print the contents of the node
def __str__(self):
return self.data

#utility function to check if a given node has 0 children (is a leaf node)
def isLeaf(self):
return ((self.left == None) and (self.right == None))
Expand All @@ -32,100 +32,100 @@ class merkleTree:
def __init__(self):
self.root = None
self._merkleRoot = ''
# private utility function to return a hash of an input string, using the sha256 algorithm

# private utility function to return a hash of an input string, using the sha256 algorithm
def __returnHash(self, x):
return (hashlib.sha256(x.encode()).hexdigest())

# function to generate a tree from a list. The list is expected to contain
# the list of transactions(as strings) we wish to seal in a block
# the list of transactions(as strings) we wish to seal in a block
def makeTreeFromArray(self, arr):

# all the elements of the list must be leaf nodes, hence total nodes in the tree
# is [2*(noOfLeafNodes) - 2]
def __noOfNodesReqd(arr):
x = len(arr)
return (2*x - 1)

# Private function to build tree with a list generated by a sequence corresponding to the
# number of nodes required for the tree.
# For e.g. if we have 4 transactions, i.e. 4 leafNodes, we will have a total of 7 nodes
# in the tree. Hence this function takes in a list that looks like [1,2,3,4,5,6,7] and
# in the tree. Hence this function takes in a list that looks like [1,2,3,4,5,6,7] and
# creates a binary tree by recursively inserting elements in inorder fasion.
def __buildTree(arr, root, i, n):
# Base case for recursion
if i < n:
temp = Node(str(arr[i]))
root = temp

# insert left child
root.left = __buildTree(arr, root.left,2 * i + 1, n)

# insert right child
root.right = __buildTree(arr, root.right,2 * i + 2, n)
def __buildTree(arr, root, i, n):

# Base case for recursion
if i < n:
temp = Node(str(arr[i]))
root = temp

# insert left child
root.left = __buildTree(arr, root.left,2 * i + 1, n)

# insert right child
root.right = __buildTree(arr, root.right,2 * i + 2, n)

return root

# This function adds our transactions (leaf Node data) to the Leaf Nodes in the tree
# hence now the tree looks like :
# ""
# /\
# "" ""
# /\ /\
# (txn1) (txn2) (txn3) (txn4)
# (txn1) (txn2) (txn3) (txn4)
def __addLeafData(arr, node):

if not node:
return

__addLeafData(arr, node.left)
if node.isLeaf():
node.data = self.__returnHash(arr.pop())
else:
node.data = ''
__addLeafData(arr, node.right)

# Driver function calls of the main function makeTreeFromArray
nodesReqd = __noOfNodesReqd(arr)
nodeArr = [num for num in range(1,nodesReqd+1)]
self.root = __buildTree(nodeArr)
self.root = __buildTree(nodeArr, self.root, 0, nodesReqd)
__addLeafData(arr,self.root)

# utility function to traverse the tree using inorder Traversal algorithm
# utility function to traverse the tree using inorder Traversal algorithm
def inorderTraversal(self, node):
if not node:
return

self.inorderTraversal(node.left)
print(node)
self.inorderTraversal(node.right)

# function to calculate merkle root of the tree. This is a recursive algorithm.
# Essentially, the data of parent node P, is the hash of concatenation of data of its two
# Essentially, the data of parent node P, is the hash of concatenation of data of its two
# child nodes, A and B. If H(x) is the hash function,
# P = H( H(A) + H(B) )
# If R is the root, then data of R is the merkle hash or merkle root.
# If R is the root, then data of R is the merkle hash or merkle root.
def calculateMerkleRoot(self):

def __merkleHash(node):
if node.isLeaf():
return node

left = __merkleHash(node.left).data
right = __merkleHash(node.right).data
node.data = self.__returnHash(left+right)
return node

merkleRoot = __merkleHash(self.root)
self._merkleRoot = merkleRoot.data
return self._merkleRoot

return self._merkleRoot

#utility function to get the merkle Root of that tree
def getMerkleRoot(self):
return self._merkleRoot

# utility function to verify if the transactions are intact with respect to this tree.
# say we know transaction list A is intact and original. We create a merkle Tree with that.
# Now we want to know whether the original list of transactions has been tampered with,
Expand All @@ -144,4 +144,4 @@ def verifyUtil(self, arr1):
else:
print("Transactions have been tampered")
return False