Add 'patch' support to bytesig entry

This allows us to define patches in line with the rest of the
configuration, ensuring that they don't go out of sync with the
corresponding validation byte pattern.

src/smgdc/types.py

@@ -4,9 +4,23 @@ import ast
 import re
 
 
+class ByteSequence:
+    """
+    A fixed sequence of space-separated hex bytes.
+    """
+
+    data: bytes
+
+    def __init__(self, pattern: str):
+        self.data = bytes(int(x, 16) for x in filter(None, pattern.split()))
+
+    def __str__(self):
+        return "".join(rf"\x{b:02X}" for b in list(self.data))
+
+
 class ByteSignature:
     """
-    A sequence of hex bytes to be searched.
+    A sequence of hex bytes to be searched.  The sequence may include wildcards.
     """
 
     pattern: list[str]

src/smgdc/validate.py

@@ -19,7 +19,7 @@ import msgspec
 
 from . import vtable as vt_helpers
 from .angr.vtable_disamb import VtableDisambiguator
-from .types import ByteSignature, Code, IntLiteral
+from .types import ByteSequence, ByteSignature, Code, IntLiteral
 
 KEY_AS_IS = string.Template("${name}")
 
@@ -223,6 +223,10 @@ class ByteSigEntry(LocationEntry, tag="bytesig", kw_only=True):
     # value to be inserted into gameconf after asserting that the given location matches
     contents: ByteSignature
 
+    # support for Source Scramble-style memory patches to ensure synchronization
+    patch: ByteSequence | None = None
+    preserve: ByteSequence | None = None
+
     # most bytesigs are expected to be unique; escape hatch for those that are just typecasted
     allow_multiple: bool = False
 
@@ -232,6 +236,11 @@ class ByteSigEntry(LocationEntry, tag="bytesig", kw_only=True):
             KEY_SUFFIX("OFFSET"): self.offset_fmt.format_value(self.offset),
         }
 
+        if self.patch:
+            outputs[KEY_SUFFIX("PATCH")] = str(self.patch)
+            if self.preserve:
+                outputs[KEY_SUFFIX("PRESERVE")] = str(self.preserve)
+
         if self.symbol or self.bytescan:
             address = self.calculate_phys_address(bin)
             data = bin.read(address, self.contents.length)
@@ -288,5 +297,7 @@ def read_config(config: configparser.ConfigParser) -> GameConfDict:
         {s: config[s] for s in config.sections()},
         type=GameConfDict,
         strict=False,
-        dec_hook=convert_types(ByteSignature, Code, IntLiteral, struct.Struct, pathlib.Path),
+        dec_hook=convert_types(
+            ByteSequence, ByteSignature, Code, IntLiteral, struct.Struct, pathlib.Path
+        ),
     )