Intial commit

h8536/rom.py

@@ -0,0 +1,42 @@
+from __future__ import annotations
+
+from .formatting import h16
+
+
+class DecodeError(Exception):
+    pass
+
+
+class Rom:
+    def __init__(self, data: bytes, base: int = 0) -> None:
+        self.data = data
+        self.base = base
+
+    @property
+    def end(self) -> int:
+        return self.base + len(self.data)
+
+    def offset(self, address: int) -> int:
+        return address - self.base
+
+    def contains(self, address: int, size: int = 1) -> bool:
+        off = self.offset(address)
+        return 0 <= off and off + size <= len(self.data)
+
+    def u8(self, address: int) -> int:
+        if not self.contains(address):
+            raise DecodeError(f"address out of ROM: {h16(address)}")
+        return self.data[self.offset(address)]
+
+    def u16(self, address: int) -> int:
+        if not self.contains(address, 2):
+            raise DecodeError(f"word out of ROM: {h16(address)}")
+        off = self.offset(address)
+        return (self.data[off] << 8) | self.data[off + 1]
+
+    def slice(self, address: int, size: int) -> bytes:
+        if not self.contains(address, size):
+            raise DecodeError(f"range out of ROM: {h16(address)}+{size}")
+        off = self.offset(address)
+        return self.data[off : off + size]
+