scripts: Added parity.py for quick parity calculation

This is probably overkill, but who really wants to be calculating parity
by hand...

scripts/parity.py

@@ -0,0 +1,86 @@
+#!/usr/bin/env python3
+
+import io
+import os
+import struct
+import sys
+import functools as ft
+import operator as op
+
+
+def openio(path, mode='r', buffering=-1):
+    # allow '-' for stdin/stdout
+    if path == '-':
+        if 'r' in mode:
+            return os.fdopen(os.dup(sys.stdin.fileno()), mode, buffering)
+        else:
+            return os.fdopen(os.dup(sys.stdout.fileno()), mode, buffering)
+    else:
+        return open(path, mode, buffering)
+
+def popc(x):
+    return bin(x).count('1')
+
+def parity(x):
+    return popc(x) & 1
+
+
+def main(paths, **args):
+    # interpret as sequence of hex bytes
+    if args.get('hex'):
+        print('%01x' % parity(ft.reduce(
+            op.xor,
+            bytes(int(path, 16) for path in paths),
+            0)))
+
+    # interpret as strings
+    elif args.get('string'):
+        for path in paths:
+            print('%01x' % parity(ft.reduce(
+                op.xor,
+                path.encode('utf8'),
+                0)))
+
+    # default to interpreting as paths
+    else:
+        if not paths:
+            paths = [None]
+
+        for path in paths:
+            with openio(path or '-', 'rb') as f:
+                # calculate parity
+                xor = 0
+                while True:
+                    block = f.read(io.DEFAULT_BUFFER_SIZE)
+                    if not block:
+                        break
+
+                    xor = ft.reduce(op.xor, block, xor)
+
+                # print what we found
+                if path is not None:
+                    print('%01x  %s' % (parity(xor), path))
+                else:
+                    print('%01x' % parity(xor))
+
+if __name__ == "__main__":
+    import argparse
+    import sys
+    parser = argparse.ArgumentParser(
+        description="Calculates parity.",
+        allow_abbrev=False)
+    parser.add_argument(
+        'paths',
+        nargs='*',
+        help="Paths to read. Reads stdin by default.")
+    parser.add_argument(
+        '-x', '--hex',
+        action='store_true',
+        help="Interpret as a sequence of hex bytes.")
+    parser.add_argument(
+        '-s', '--string',
+        action='store_true',
+        help="Interpret as strings.")
+    sys.exit(main(**{k: v
+        for k, v in vars(parser.parse_intermixed_args()).items()
+        if v is not None}))