bit rotation

src/authur1.py

@@ -10,22 +10,75 @@ Since this (auth) hash did not have a name before, I gave it the name 'authur1'
 """
 import math
 import argparse
+from ctypes import c_uint32
 
-DEFINED_INITIAL = bytearray(bytes([0x52, 0x4f, 0x46, 0x4c]))
+# constants for authur1
+SHIFT_LENGTH = 17
+DEFINED_INITIAL = bytes([0x52, 0x4f, 0x46, 0x4c])
 
-def Q(input: bytearray) -> bytearray:
-    assert len(input) == 4 # needs to be 32 bit
+"""
+C implementation for bit rotating:
+see https://en.wikipedia.org/wiki/Circular_shift#Implementing_circular_shifts
 
+```c
+/*
+ * Shift operations in C are only defined for shift values which are
+ * not negative and smaller than sizeof(value) * CHAR_BIT.
+ * The mask, used with bitwise-and (&), prevents undefined behaviour
+ * when the shift count is 0 or >= the width of unsigned int.
+ */
 
-    return input
+#include <stdint.h>  // for uint32_t, to get 32-bit-wide rotates, regardless of the size of int.
+#include <limits.h>  // for CHAR_BIT
 
-def H(input: bytearray) -> bytearray:
+uint32_t rotl32 (uint32_t value, unsigned int count) {
+    const unsigned int mask = CHAR_BIT * sizeof(value) - 1;
+    count &= mask;
+    return (value << count) | (value >> (-count & mask));
+}
+
+uint32_t rotr32 (uint32_t value, unsigned int count) {
+    const unsigned int mask = CHAR_BIT * sizeof(value) - 1;
+    count &= mask;
+    return (value >> count) | (value << (-count & mask));
+}
+```
+"""
+
+"""
+The rotations are tested agains a c implementation and seem to work fine.
+"""
+# constant value defined in limits.h, it's 8 (bit) on my machine, on yours probably too.
+CHAR_BIT = 8
+# python is being a dynamic dumbass, do a 32 bit shift / 4 byte
+VALUE_SIZE = 4
+def rotl(value: int, count: int) -> int:
+    mask: int = CHAR_BIT * VALUE_SIZE - 1;
+    count &= mask;
+    return (value << count) | (value >> (-count & mask));
+
+def rotr(value: int, count: int) -> int:
+    mask: int = CHAR_BIT * VALUE_SIZE - 1;
+    count &= mask;
+    return (value >> count) | (value << (-count & mask));
+
+def Q(input: c_uint32) -> c_uint32:
+    output: c_uint32
+
+    output = input ^ (rot_r(input, SHIFT_LENGTH))
+
+    return output
+
+def H(input: bytes) -> bytes:
 
 
     return input
 
 def main():
-    pass
+    a: str = input()
+    ai = int(a)
+    print((ai))
+    print((rotr(ai,17)))
 
 if __name__ == "__main__":
     main()