completed chunk read and write

util.py

@@ -2,6 +2,7 @@ from secretsharing import PlaintextToHexSecretSharer
 import subprocess
 import json
 from Crypto.Cipher import AES
+from more_itertools import sliced
 
 # This function splits the secret and returns a list of shares
 def splitSecret(secret,threshold,splits):
@@ -28,9 +29,29 @@ def readUnitFromBlockchain(txid):
 	text = content['floData']
 	return text
 
-#TODO write data chunk to blockchain
-#TODO read data chunk from blockchain
+#write data chunk to blockchain
 def writeDatatoBlockchain(text):
-	splits = len(text)//350 + 1
-	#TODO create a sliced list of strings
-	#TODO for each string in the list create a transaction with txid of previous string
+	n_splits = len(text)//350 + 1				#number of splits to be created
+	splits = list(sliced(text, n_splits))		#create a sliced list of strings
+	tail = writeUnitToBlockchain(splits[n_splits]) 		#create a transaction which will act as a tail for the data
+	cursor = tail
+	if n_splits == 1:
+		return cursor							#if only single transaction was created then tail is the cursor
+
+	#for each string in the list create a transaction with txid of previous string
+	for i in range(n_splits-1,0):
+		splits[i] = 'next:'+cursor+splits[i]
+		cursor = writeUnitToBlockchain(splits[i])
+	return cursor
+
+#TODO read data chunk from blockchain
+def readDatafromBlockchain(cursor):
+	text = []
+	cursor_data = readUnitFromBlockchain(cursor)
+	text.append(cursor_data[:])
+	while(cursor_data[:5]=='next:'):
+		cursor = cursor_data[:]
+		cursor_data = readUnitFromBlockchain(cursor)
+		text.append(cursor_data[:])
+	text.join('')
+	return text