First public commit.

lenser/ti99/cartridge.py

@@ -0,0 +1,92 @@
+"""Builds a TI-99/4A 8KB cartridge ROM (>6000-7FFF) holding the viewer + image
+data, and packages it as an RPK (the cartridge container MAME loads).
+
+ROM layout
+  >6000  standard cartridge header (>AA magic, pointer to the program list)
+  >6010  program-list entry -> appears on the TI menu, points at the viewer
+  ....   viewer machine code (TMS9900)
+  ....   image data (6144-byte pattern + 768-byte cell colours)
+  pad to 8192 bytes
+"""
+
+from __future__ import annotations
+
+import io
+import zipfile
+
+from . import viewer
+
+CART_BASE = 0x6000
+ROM_SIZE = 0x2000          # 8 KB
+PROG_LIST = 0x6010
+
+
+def _ascii(name: str, limit: int) -> bytes:
+    """TI menu names are uppercase ASCII; strip anything else."""
+    out = "".join(c for c in name.upper() if 32 <= ord(c) < 127)
+    return out[:limit].encode("ascii") or b"PHOTO"
+
+
+def _even(x: int) -> int:
+    return x + (x & 1)
+
+
+def build_rom(data: bytes, title: str = "PHOTO", display: str = "forever",
+              seconds: int = 0, video: str = "ntsc") -> bytes:
+    if len(data) != viewer.PATTERN_BYTES + viewer.NCELLS:
+        raise ValueError(f"unexpected data length {len(data)}")
+    name = _ascii(title, 16)
+
+    vk = dict(display=display, seconds=seconds, video=video)
+    entry = _even(PROG_LIST + 2 + 2 + 1 + len(name))   # code starts after the name
+    code = viewer.build(entry, 0, **vk)                 # pass 1: measure length
+    data_addr = _even(entry + len(code))
+    code = viewer.build(entry, data_addr, **vk)         # pass 2: real data address
+
+    if data_addr - CART_BASE + len(data) > ROM_SIZE:
+        raise ValueError("image + viewer exceed 8KB cartridge")
+
+    rom = bytearray(b"\x00" * ROM_SIZE)
+
+    def put(addr, payload):
+        off = addr - CART_BASE
+        rom[off:off + len(payload)] = payload
+
+    def putw(addr, word):
+        put(addr, bytes([(word >> 8) & 0xFF, word & 0xFF]))
+
+    # cartridge header
+    rom[0] = 0xAA          # valid
+    rom[1] = 0x01          # version
+    putw(0x6006, PROG_LIST)
+
+    # program-list entry (single item)
+    putw(PROG_LIST + 0, 0x0000)     # no next entry
+    putw(PROG_LIST + 2, entry)      # viewer entry point
+    rom[PROG_LIST + 4 - CART_BASE] = len(name)
+    put(PROG_LIST + 5, name)
+
+    put(entry, code)
+    put(data_addr, data)
+    return bytes(rom)
+
+
+def write_rpk(rom: bytes, path: str, title: str = "photo"):
+    """Write an MAME RPK (zip with a standard single-ROM layout)."""
+    binname = "viewer.bin"
+    layout = (
+        '<?xml version="1.0" encoding="utf-8"?>\n'
+        '<romset version="1.0">\n'
+        '  <resources>\n'
+        f'    <rom id="romimage" file="{binname}"/>\n'
+        '  </resources>\n'
+        '  <configuration>\n'
+        '    <pcb type="standard">\n'
+        '      <socket id="rom_socket" uses="romimage"/>\n'
+        '    </pcb>\n'
+        '  </configuration>\n'
+        '</romset>\n'
+    )
+    with zipfile.ZipFile(path, "w", zipfile.ZIP_DEFLATED) as z:
+        z.writestr(binname, rom)
+        z.writestr("layout.xml", layout)