53 lines
1.9 KiB
Python
53 lines
1.9 KiB
Python
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"""On-disk cache for the (FlatBook, BookLayout) pair a book open computes —
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extraction + row-layout for very large books (tens of thousands of blocks)
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can take several seconds each; reopening the same book at the same terminal
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width should be near-instant instead of paying that cost again every time.
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Not a correctness-critical cache: any miss (new book, different width, edited
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file) just falls back to recomputing from scratch, so a stale/corrupt cache
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entry is handled by overwriting it, never by crashing the reader.
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"""
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from __future__ import annotations
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import hashlib
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import pickle
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from pathlib import Path
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from platformdirs import user_cache_dir
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from .blocks import FlatBook
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from .layout import BookLayout
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_CACHE_DIR = Path(user_cache_dir("diora-tui", "diora")) / "layout_cache"
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def _cache_key(path: Path, width: int) -> str:
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stat = path.stat()
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raw = f"{path.resolve()}|{stat.st_size}|{stat.st_mtime_ns}|{width}"
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return hashlib.sha256(raw.encode()).hexdigest()[:32]
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def load(path: Path, width: int) -> tuple[FlatBook, BookLayout] | None:
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cache_file = _CACHE_DIR / f"{_cache_key(path, width)}.pickle"
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if not cache_file.exists():
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return None
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try:
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with cache_file.open("rb") as f:
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book, book_layout = pickle.load(f)
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if not isinstance(book, FlatBook) or not isinstance(book_layout, BookLayout):
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return None
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return book, book_layout
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except Exception:
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return None
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def save(path: Path, width: int, book: FlatBook, book_layout: BookLayout) -> None:
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_CACHE_DIR.mkdir(parents=True, exist_ok=True)
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cache_file = _CACHE_DIR / f"{_cache_key(path, width)}.pickle"
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try:
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with cache_file.open("wb") as f:
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pickle.dump((book, book_layout), f, protocol=pickle.HIGHEST_PROTOCOL)
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except Exception:
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pass # best-effort — a failed cache write shouldn't break reading
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