First public commit.

lenser/diskimage.py

@@ -0,0 +1,104 @@
+"""Build .d64/.d71/.d81 Commodore disk images with VICE's `c1541`.
+
+We shell out to `c1541` rather than re-implementing CBM-DOS: it is battle-tested
+and handles BAM/directory layout for all three formats correctly.
+"""
+
+from __future__ import annotations
+
+import os
+import shutil
+import subprocess
+import tempfile
+
+FORMATS = {
+    "d64": ("d64", 174848),   # 35 tracks, 664 blocks free
+    "d71": ("d71", 349696),   # double sided
+    "d81": ("d81", 819200),   # 3.5" 800K
+}
+
+# Per-format usable data budget (blocks * 254), conservative.
+BLOCKS_FREE = {"d64": 664, "d71": 1328, "d81": 3160}
+
+
+class DiskError(RuntimeError):
+    pass
+
+
+def have_c1541() -> bool:
+    return shutil.which("c1541") is not None
+
+
+def petscii_name(text: str, maxlen: int = 16) -> str:
+    """Sanitise a host string into a legal CBM filename.
+
+    Letters are forced to lower case: c1541 maps lower-case ASCII into the
+    standard PETSCII letter range ($41-$5A), which renders as clean letters in a
+    C64 directory listing, whereas upper-case ASCII lands in the shifted range
+    that displays oddly.
+    """
+    out = []
+    for ch in text.lower():
+        if ch.isalnum() or ch in " -+.":
+            out.append(ch)
+    name = "".join(out).strip() or "8bitlenser"
+    return name[:maxlen]
+
+
+def fmt_from_path(path: str, override: str | None) -> str:
+    if override:
+        if override not in FORMATS:
+            raise DiskError(f"unknown disk format: {override}")
+        return override
+    ext = os.path.splitext(path)[1].lower().lstrip(".")
+    return ext if ext in FORMATS else "d64"
+
+
+def build_disk(path: str, disk_format: str, disk_name: str, disk_id: str,
+               files: list[tuple[str, bytes]]) -> str:
+    """Create ``path`` of ``disk_format`` containing ``files`` (cbm_name, prg_bytes).
+
+    The first file in the list lands first in the directory, so ``LOAD"*",8,1``
+    loads it -- make that the viewer.
+    """
+    if not have_c1541():
+        raise DiskError(
+            "VICE's 'c1541' tool was not found on PATH.\n"
+            "Install it with:  sudo apt install vice   (Debian/Ubuntu)\n"
+            "or build from https://vice-emu.sourceforge.io/")
+
+    total = sum(len(b) for _, b in files)
+    budget = BLOCKS_FREE[disk_format] * 254
+    if total > budget:
+        raise DiskError(
+            f"data ({total} bytes) exceeds {disk_format} capacity (~{budget} bytes); "
+            f"use a larger disk format")
+
+    vtype = FORMATS[disk_format][0]
+    name = petscii_name(disk_name)
+    did = petscii_name(disk_id, 2) or "01"
+    path = os.path.abspath(path)
+    if os.path.exists(path):
+        os.remove(path)
+
+    with tempfile.TemporaryDirectory() as td:
+        cmd = ["c1541", "-format", f"{name},{did}", vtype, path]
+        for i, (cbm, data) in enumerate(files):
+            host = os.path.join(td, f"f{i}.prg")
+            with open(host, "wb") as f:
+                f.write(data)
+            cmd += ["-write", host, petscii_name(cbm)]
+        proc = subprocess.run(cmd, capture_output=True, text=True,
+                              errors="replace")
+        # c1541 prints a harmless "OPENCBM ... libopencbm.so" warning; only fail
+        # if the image was not actually produced.
+        if not os.path.exists(path):
+            raise DiskError(f"c1541 failed:\n{proc.stdout}{proc.stderr}")
+    return path
+
+
+def directory(path: str) -> str:
+    """Return the disk directory listing (for verification)."""
+    proc = subprocess.run(["c1541", "-attach", path, "-dir"],
+                          capture_output=True, text=True, errors="replace")
+    return proc.stdout