Update scatterhash to honor a maxsize

scatterhash.py

@@ -26,29 +26,34 @@ def get_offsets(blocksize, blockcount,blocks_to_hash):
             offset = int(blocksize*i)
             yield offset
 
-def get_hash(file,hashalgo,spread):
+def get_hash(file,hashalgo,spread,maxsize):
     h=hashlib.new(hashalgo)
     filesize = os.path.getsize(file.name)
     blocksize = h.block_size*65535
     blockcount = math.ceil(filesize/blocksize)
     blocks_to_hash = math.ceil(blockcount*spread/100)
+    if (blocks_to_hash * blocksize) > maxsize:
+        blocks_to_hash = math.ceil(maxsize/blocksize)
     if filesize>blocksize:
         for of in get_offsets(blocksize,blockcount,blocks_to_hash):
             infile.seek(of)
             h.update(file.read(blocksize))
     else:
         h.update(file.read(blocksize))
-    result="{};{};{};{};{}".format(h.hexdigest(),spread,filesize,hashalgo,file.name)
+    result="{};{};{};{};{}".format(h.hexdigest(),blocks_to_hash,filesize,hashalgo,file.name)
     return result
 
 parser = argparse.ArgumentParser(description='Sparsly hash large files. Only a given percentage of the file is actualy hashed.')
+
 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)')
+parser.add_argument('-s',metavar='N', action="store",dest="size",type=int, nargs='?',default=10,help='maximum amount of data per file in MB')
 parser.add_argument('-c', action="store",dest="hashalgo",nargs='?',default="md5",help='select an hashalgorithm (default=md5)')
 parser.add_argument('file', type=argparse.FileType('rb'), nargs='+')
 args = parser.parse_args()
 
 hashalgo = args.hashalgo
 spread = args.spread
+maxsize = args.size * 1024 * 1024
 for infile in args.file:
-    hashvalue = get_hash(infile,hashalgo,spread)
+    hashvalue = get_hash(infile,hashalgo,spread,maxsize)
     print(hashvalue)