implement binary patching for multimystery (for now no gui/cli support)

Patch.py

@@ -0,0 +1,54 @@
+import bsdiff4
+import yaml
+import os
+import lzma
+
+import Utils
+
+base_rom_bytes = None
+
+
+def get_base_rom_bytes() -> bytes:
+    global base_rom_bytes
+    if not base_rom_bytes:
+        with open("host.yaml") as f:
+            options = Utils.parse_yaml(f.read())
+        file_name = options["general_options"]["rom_file"]
+        base_rom_bytes = load_bytes(file_name)
+    return base_rom_bytes
+
+
+def generate_patch(rom: bytes, metadata=None) -> bytes:
+    if metadata is None:
+        metadata = {}
+    patch = bsdiff4.diff(get_base_rom_bytes(), rom)
+    patch = yaml.dump({"meta": metadata,
+                       "patch": patch})
+    return patch.encode()
+
+
+def create_patch_file(rom_file_to_patch: str, server: str = "") -> str:
+    bytes = generate_patch(load_bytes(rom_file_to_patch),
+                           {
+                               "server": server})  # allow immediate connection to server in multiworld. Empty string otherwise
+    target = os.path.splitext(rom_file_to_patch)[0] + ".bbp"
+    write_lzma(bytes, target)
+    return target
+
+
+def create_rom_file(patch_file) -> dict:
+    data = Utils.parse_yaml(lzma.decompress(load_bytes(patch_file)).decode("utf-8-sig"))
+    patched_data = bsdiff4.patch(get_base_rom_bytes(), data["patch"])
+    with open(os.path.splitext(patch_file)[0] + ".sfc", "wb") as f:
+        f.write(patched_data)
+    return data["meta"]
+
+
+def load_bytes(path: str):
+    with open(path, "rb") as f:
+        return f.read()
+
+
+def write_lzma(data: bytes, path: str):
+    with lzma.LZMAFile(path, 'wb') as f:
+        f.write(data)