Add validation functionality to scatterhash

scatterhash.py

@@ -26,17 +26,18 @@ def get_offsets(blocksize, blockcount,blocks_to_hash):
             offset = int(blocksize*i)
             yield offset
 
-def get_hash(file,hashalgo,spread,maxsize):
+def get_hash(file,hashalgo,spread=-1,maxsize=-1,blocks_to_hash=-1):
     h=hashlib.new(hashalgo)
     filesize = os.path.getsize(file.name)
     blocksize = h.block_size*65535
     blockcount = math.ceil(filesize/blocksize)
+    if blocks_to_hash == -1 :
         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)
+            file.seek(of)
             h.update(file.read(blocksize))
     else:
         h.update(file.read(blocksize))
@@ -49,11 +50,36 @@ parser.add_argument('-p',metavar='N', action="store",dest="spread",type=int, nar
 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='+')
+parser.add_argument('-v', default=False, dest="validate", action='store_true', help='read output-file of previous run and validate hashes')
+parser.add_argument('-1', default=True, dest="mismatches", action='store_false', help='suppress mismatches')
+parser.add_argument('-0', default=True, dest="matches", action='store_false', help='suppress matches')
 args = parser.parse_args()
 
+if not args.validate:
     hashalgo = args.hashalgo
     spread = args.spread
     maxsize = args.size * 1024 * 1024
     for infile in args.file:
-    hashvalue = get_hash(infile,hashalgo,spread,maxsize)
-    print(hashvalue)
+        print(get_hash(infile,hashalgo,spread,maxsize))
+else:
+    print("validating")
+    for line in args.file[0]:
+        line=line.decode().strip()
+        hash, blocks_hashed, filesize, hashalgo, file = line.split(';')
+        blocks_hashed=int(blocks_hashed)
+        filesize=int(filesize)
+        if os.path.isfile(file):
+            if os.path.getsize(file) != filesize:
+                result="BAD_SIZE"
+            else:
+                rehash=get_hash(open(file,'rb'),hashalgo,blocks_to_hash=blocks_hashed)
+                if hash == rehash.split(";")[0]:
+                    result = "OK"
+                else:
+                    result = "BAD_HASH"
+        else:
+            result="FILE_NOT_FOUND"
+        if args.mismatches and not result == "OK":
+            print("{};{}".format(result,line))
+        elif args.matches and result == "OK":
+            print("{};{}".format(result,line))