use built-in int.from_bytes on python3 for bytes→int conversion

Author: tomato42

tlslite/utils/compat.py

@@ -80,6 +80,8 @@ def remove_whitespace(text):
         """Removes all whitespace from passed in string"""
         return re.sub(r"\s+", "", text, flags=re.UNICODE)
 
+    bytes_to_int = int.from_bytes
+
 else:
     # Python 2.6 requires strings instead of bytearrays in a couple places,
     # so we define this function so it does the conversion if needed.
@@ -147,6 +149,16 @@ def time_stamp():
         """Returns system time as a float"""
         return time.clock()
 
+    def bytes_to_int(val, byteorder):
+        """Convert bytes to an int."""
+        if not val:
+            return 0
+        if byteorder == "big":
+            return int(b2a_hex(val), 16)
+        if byteorder == "little":
+            return int(b2a_hex(val[::-1]), 16)
+        raise ValueError("Only 'big' and 'little' endian supported")
+
 try:
     # Fedora and Red Hat Enterprise Linux versions have small curves removed
     getattr(ecdsa, 'NIST192p')

tlslite/utils/cryptomath.py

@@ -15,7 +15,7 @@
 import binascii
 import sys
 
-from .compat import compat26Str, compatHMAC, compatLong, b2a_hex
+from .compat import compat26Str, compatHMAC, compatLong, bytes_to_int
 from .codec import Writer
 
 from . import tlshashlib as hashlib
@@ -204,18 +204,8 @@ def bytesToNumber(b, endian="big"):
 
     By default assumes big-endian encoding of the number.
     """
-    # if string is empty, consider it to be representation of zero
-    # while it may be a bit unorthodox, it is the inverse of numberToByteArray
-    # with default parameters
-    if not b:
-        return 0
+    return bytes_to_int(b, endian)
 
-    if endian == "big":
-        return int(b2a_hex(b), 16)
-    elif endian == "little":
-        return int(b2a_hex(b[::-1]), 16)
-    else:
-        raise ValueError("Only 'big' and 'little' endian supported")
 
 def numberToByteArray(n, howManyBytes=None, endian="big"):
     """