initial commit

mem_edit/utils.py

@@ -0,0 +1,63 @@
+"""
+Utility functions and types:
+
+  Type definition for buffers:
+    ctypes_buffer_t
+  Custom exception type:
+    MemEditError
+
+  Search for a buffer inside another buffer:
+    search_buffer(needle_buffer, haystack_buffer)
+  Check if two buffers (ctypes objects) store equal values:
+    ctypes_equal(a, b)
+"""
+
+from typing import List
+import ctypes
+
+
+ctypes_buffer_t = ctypes._SimpleCData or ctypes.Array or ctypes.Structure or ctypes.Union
+
+
+class MemEditError(Exception):
+    pass
+
+
+def search_buffer(needle_buffer: ctypes_buffer_t, haystack_buffer: ctypes_buffer_t) -> List[int]:
+    """
+    Search for a buffer inside another buffer.
+
+    :param needle_buffer: Buffer to search for.
+    :param haystack_buffer: Buffer to search in.
+    :return: List of offsets where the needle_buffer was found.
+    """
+    found = []
+    read_type = type(needle_buffer)
+    for offset in range(0, len(haystack_buffer) - ctypes.sizeof(needle_buffer)):
+        v = read_type.from_buffer(haystack_buffer, offset)
+        if ctypes_equal(needle_buffer, v):
+            found.append(offset)
+    return found
+
+
+def ctypes_equal(a: ctypes_buffer_t, b: ctypes_buffer_t) -> bool:
+    """
+    Check if the values stored inside two ctypes buffers are equal.
+    """
+    if not type(a) == type(b):
+        return False
+    
+    if isinstance(a, ctypes.Array):
+        return a[:] == b[:]
+    elif isinstance(a, ctypes.Structure) or isinstance(a, ctypes.Union):
+        for attr_name, attr_type in a._fields_:
+            a_attr, b_attr = (getattr(x, attr_name) for x in (a, b))
+            if isinstance(a, ctypes_buffer_t):
+                if not ctypes_equal(a_attr, b_attr):
+                    return False
+            elif not a_attr == b_attr:
+                return False
+
+        return True
+    else:
+        return a.value == b.value