arch: Use dataclass instead of namedtuple

Python's dataclass annotation gives us a nice way to cleanly and
concisely define our list of supported architectures similar to namedtuple.
Unlike namedtuple, though, dataclass gives us an actual class that is
significantly more feature rich and even allows us to add functionality.
In general, these are meant to be like const records of info about an
architecture, so we use frozen=True to enforce some const correctness.

There were some issues when involving other classes for the ActiveArch
feature (subclassing and composition both had their respective issues),
so I'm removing __ActiveArch__ and putting a set() method directly on
Arch.  This method will copy a given Arch into the self object.  This
technically breaks const correctness as this does modify the object, but
it is intended to only be used on a single sentinel Arch that represents
the active arch.  This arch is initialized with x86_64 by default.

Signed-off-by: dusoleil <howcansocksbereal@gmail.com>
Reviewed-by: Malfurious <m@lfurio.us>

1 files changed, 15 insertions, 13 deletions

diff --git a/sploit/arch.py b/sploit/arch.py
index e5de2ce..5575b05 100644
--- a/sploit/arch.py
+++ b/sploit/arch.py
@@ -1,4 +1,4 @@
-from collections import namedtuple as nt
+from dataclasses import dataclass
 
 def btoi(b, signed=False):
     return int.from_bytes(b, arch.endianness, signed=signed)
@@ -6,16 +6,18 @@ def btoi(b, signed=False):
 def itob(i, signed=False):
     return i.to_bytes(arch.wordsize, arch.endianness, signed=signed)
 
-Arch = nt("Arch", "wordsize  endianness  alignment  nopcode")
-x86      = Arch(          4,   'little',        16, b'\x90')
-x86_64   = Arch(          8,   'little',        16, b'\x90')
-ARM      = Arch(          4,   'little',         8, b'\xe1\xa0\x00\x00')
-THUMB    = Arch(          4,   'little',         8, b'\x46\xc0')
+@dataclass(frozen=True)
+class Arch:
+    wordsize: int
+    endianness: str
+    alignment: int
+    nopcode: bytes
+    def set(self,k):
+        self.__dict__.update(k.__dict__)
 
-class __ActiveArch__:
-    __arch = x86_64
-    def __getattr__(self,k):
-        return getattr(self.__arch,k)
-    def set(self,a):
-        self.__arch = a
-arch = __ActiveArch__()
+x86      = Arch( 4, 'little', 16, b'\x90')
+x86_64   = Arch( 8, 'little', 16, b'\x90')
+ARM      = Arch( 4, 'little',  8, b'\xe1\xa0\x00\x00')
+THUMB    = Arch( 4, 'little',  8, b'\x46\xc0')
+
+arch = Arch(**x86_64.__dict__)