62 lines
2.3 KiB
Python
62 lines
2.3 KiB
Python
"""Assemble the C16 TED viewer with `xa` and build the loadable PRG.
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The PRG loads at the C16 BASIC start ($1001): a BASIC stub (`10 SYS4128`)
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followed by the 7501 viewer (at $1020), the two colour matrices ($1800 / $1C00)
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and the bitmap ($2000). MAME's quickload runs it, the stub SYSes the viewer.
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"""
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from __future__ import annotations
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import os
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import shutil
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import subprocess
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import tempfile
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VIEWER_DIR = os.path.dirname(os.path.abspath(__file__))
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BASIC_START = 0x1001
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ML_ORG = 0x1020
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ATTR_ORG = 0x1800 # luminance matrix (video matrix base)
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CH_ORG = 0x1C00 # hue matrix (video base | $400)
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BITMAP_ORG = 0x2000
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# BASIC: 10 SYS4128 ($1020 = 4128) -- bytes as they sit from $1001
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_STUB = bytes([0x0B, 0x10, 0x0A, 0x00, 0x9E,
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0x34, 0x31, 0x32, 0x38, 0x00, 0x00, 0x00])
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class AssemblerError(RuntimeError):
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pass
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def have_xa() -> bool:
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return shutil.which("xa") is not None
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def _assemble() -> bytes:
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if not have_xa():
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raise AssemblerError("The 'xa' (xa65) assembler was not found on PATH.\n"
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"Install it with: sudo apt install xa65")
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proc = subprocess.run(["xa", "-o", "/dev/stdout", "viewer.s"],
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capture_output=True, cwd=VIEWER_DIR)
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if proc.returncode != 0:
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raise AssemblerError(f"xa failed:\n{proc.stderr.decode()}")
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return proc.stdout
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def build_prg(payload: bytes) -> bytes:
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"""payload = bitmap(8000) + attr(1000) + ch(1000); returns the loadable PRG."""
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bitmap, attr, ch = payload[:8000], payload[8000:9000], payload[9000:10000]
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code = _assemble()
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mem = bytearray()
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mem += _STUB # $1001..
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mem += b"\x00" * (ML_ORG - BASIC_START - len(mem))
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mem += code # $1020..
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if len(mem) > ATTR_ORG - BASIC_START:
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raise AssemblerError("viewer code overruns the $1800 matrix area")
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mem += b"\x00" * (ATTR_ORG - BASIC_START - len(mem))
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mem += attr # $1800..
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mem += b"\x00" * (CH_ORG - BASIC_START - len(mem))
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mem += ch # $1C00..
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mem += b"\x00" * (BITMAP_ORG - BASIC_START - len(mem))
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mem += bitmap # $2000..
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return bytes([BASIC_START & 0xFF, BASIC_START >> 8]) + bytes(mem)
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