First public commit.

lenser/coco3/cartridge.py

@@ -0,0 +1,29 @@
+"""Build a CoCo 3 Program Pak cartridge ROM (.ccc): GIME viewer + 15360-byte image.
+
+The CoCo 3 autostarts the cartridge at $C000.  Layout: viewer code, then the
+linear GIME image, padded to a 16KB ROM."""
+from __future__ import annotations
+
+from . import viewer
+
+CART_BASE = 0xC000
+CART_SIZE = 0x4000             # 16 KB
+
+
+def build_rom(data: bytes, cres: int, inks, border: int) -> bytes:
+    if len(data) != viewer.IMG_LEN:
+        raise ValueError(f"unexpected image length {len(data)}")
+    kw = dict(cres=cres, inks=inks, border=border)
+    code = viewer.build(0, **kw)                  # pass 1: measure code length
+    data_src = CART_BASE + len(code)
+    code = viewer.build(data_src, **kw)           # pass 2: real data address
+    rom = code + bytes(data)
+    if len(rom) > 0x3F00:                         # keep clear of the $FF00 I/O page
+        raise ValueError("viewer + image exceed the cartridge ROM window")
+    return rom + bytes(CART_SIZE - len(rom))
+
+
+def write_ccc(rom: bytes, path: str) -> str:
+    with open(path, "wb") as f:
+        f.write(rom)
+    return path