55 lines
1.9 KiB
Python
Executable File
55 lines
1.9 KiB
Python
Executable File
#!/usr/bin/python3
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import sys
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import hashlib
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import os
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import numpy as np
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import math
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import argparse
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def even_select(N, M):
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if M > N/2:
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cut = np.zeros(N, dtype=int)
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q, r = divmod(N, N-M)
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indices = [q*i + min(i, r) for i in range(N-M)]
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cut[indices] = True
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else:
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cut = np.ones(N, dtype=int)
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q, r = divmod(N, M)
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indices = [q*i + min(i, r) for i in range(M)]
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cut[indices] = False
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return cut
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def get_offsets(blocksize, blockcount,blocks_to_hash):
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selection = even_select(blockcount,blocks_to_hash)
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for i in range(0,blockcount):
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if selection[i] == 0:
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offset = int(blocksize*i)
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yield offset
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def get_hash(file,hashalgo,spread):
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h=hashlib.new(hashalgo)
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filesize = os.path.getsize(file.name)
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blocksize = h.block_size*65535
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blockcount = math.ceil(filesize/blocksize)
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blocks_to_hash = math.ceil(blockcount*spread/100)
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if filesize>blocksize:
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for of in get_offsets(blocksize,blockcount,blocks_to_hash):
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infile.seek(of)
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h.update(file.read(blocksize))
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else:
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h.update(file.read(blocksize))
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result="{};{};{};{};{}".format(h.hexdigest(),spread,filesize,hashalgo,file.name)
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return result
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parser = argparse.ArgumentParser(description='Sparsly hash large files. Only a given percentage of the file is actualy hashed.')
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parser.add_argument('-p',metavar='N', action="store",dest="spread",type=int, nargs='?',default=10,help='percentage of file to hash. 0 < N < 100 (default=10)')
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parser.add_argument('-c', action="store",dest="hashalgo",nargs='?',default="md5",help='select an hashalgorithm (default=md5)')
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parser.add_argument('file', type=argparse.FileType('rb'), nargs='+')
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args = parser.parse_args()
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hashalgo = args.hashalgo
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spread = args.spread
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for infile in args.file:
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hashvalue = get_hash(infile,hashalgo,spread)
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print(hashvalue)
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