Question

In Python, create a program with 2 classes that do the following.

HashCreate class, this class will accept a directory and hash each file in the directory and store the results in a dictionary. The dictionary will contain the hash value and file name.

HashVerify, the second class will accept the dictionary as input and save that in an instance attribute. This class must also contain a method for lookups that require a file path as input. The lookup method will hash the file and lookup in the dictionary to see if the hash exists. If the hash exists, the lookup method will return true and a file name associated with it.

Answer 1

Hi,

As it's not mentioned as to which hashing algorithm needs to be used, I have used md5 for hashing.

I am posting here the screen shot of the source code followed by the actual source code and test run output which confirms that the code is working fine.

Source code:

import hashlib, os
from os import listdir, getcwd
from os.path import isfile, join, normpath

#dictionary to store the hash value and file name
HashDict = {}

class HashCreate:
   def __init__(self, directory=""):
       if not directory:   #checking if the directory is empty
           print("directory name is empty!")
           return
       if not os.path.exists (directory):   #checking if the directory exists
           print("Can't find directory: " + directory)
           return

       current_path = normpath(directory) #normalising the path
       #obtaining list of files in the directory
       filenames = [f for f in listdir(current_path) if isfile(join(current_path, f))]

       global HashDict
       #creating the hash of each file and updating hash and file name in global hash dictionary
       for filename in filenames:
           filepath = join(current_path, filename)
           HashDict[self.md5(filepath)] = filename

   # method to create md5 hash
   def md5(self, fname):
       hash_md5 = hashlib.md5()
       with open(fname, "rb") as f:
           for chunk in iter(lambda: f.read(2 ** 20), b""):
               hash_md5.update(chunk)
       return hash_md5.hexdigest()

class HashVerify:
   def __init__(self, hashDict = {}):
       #taking hashdict and storing in instance attribute of HashVerify
       self.HashDict = hashDict

   #method to lookup the hash of the file specified by the file path and return as mentioned in the question
   def lookup(self, filepath = ""):
       if not filepath:   #checking if filepath is empty
           print("file path is empty!")
           return False, ""
       if not os.path.exists(filepath):   #checking if filepath exists
           print("Can't find directory: " + filepath)
           return False, ""
       fileHash = self.md5(filepath)   #calculating md5 hash of the file

       if fileHash in self.HashDict:   #checking if the hash exists in the hash dict
           return True, self.HashDict[fileHash]   #returning True and file name as hash exists
       else:
           return False, ""   #returning False and empty file name as hash doesn't exist
          
   def md5(self, fname):
       hash_md5 = hashlib.md5()
       with open(fname, "rb") as f:
           for chunk in iter(lambda: f.read(2 ** 20), b""):
               hash_md5.update(chunk)
       return hash_md5.hexdigest()

#Testing the two classes
#Please replace the directory name with a directory in your local computer
H1 = HashCreate("/Users/skotak455/Documents/TestPrograms/single_LL")
print("HashDict: ")
print(HashDict)
H2 = HashVerify(HashDict)

#Please replace the filepath with a file in your local computer
verified, file = H2.lookup("/Users/skotak455/Documents/TestPrograms/single_LL/a.out")
if verified:
   print("File is verified, file name: " + file)
else:
   print("Can't lookup the file path")

Test run output:

Thank you!!