Vito Sansevero
981639740b
Marker keys are data, not paths: only a single <slug>-<hex> folder name is ever joined onto the thumbnail folder; anything else is dropped and logged. Every preview write and delete passes one ownership check (below a key folder, lexically and resolved, no link, junction or reparse point on the way); make_parent refuses anything else and writes nothing while the folder lacks this install's marker (an unmounted mount point). Clear never descends into a junction. The configured location is in force before any request (unchecked folder mode is unavailable), and a startup check that fails leaves it invalid, never the sources. Older listings that run on the event loop no longer touch the store in folder mode. A leftover under another case of thumbnails/ on a case-insensitive disk is refused too.
672 lines
23 KiB
Python
672 lines
23 KiB
Python
"""Where previews live on disk (#320): the one resolver.
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Every mapping between an image source (a "root"), one of its media files and
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that file's preview on disk goes through this module. URL text stays in
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``thumbnail_settings`` (``thumbnail_rel``: ``thumbnails/<rel>_thumb<ext>``,
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the shape the serve route, ``inspection-state.mjs`` and ``admin.js`` share);
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this module answers where such a preview is on disk.
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The store of a source is where its previews live. With the default location
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(mode ``source``, "Inside each source") it is ``<source>/thumbnails``, exactly
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the folder every caller joined by hand before, so nothing moves.
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Writes and the switch: every preview writer takes ``write_guard`` when it
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starts (it records the location's ``generation``); the final rename runs
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under ``write_lock`` and only when the generation is unchanged and no hold
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applies (``thumbnail_encode.replace_unless_held``). Changing the location
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bumps the generation under the same lock, so no write that began before can
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land in the old store afterwards. Nothing reads or commits config while
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``write_lock`` is held. The hold check runs under it too, so hold checks take
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no lock (the job registry's ``running()`` is a lock-free snapshot) and
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``bump_generation`` is never called with a registry or config lock held.
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All functions are blocking: call them off the event loop.
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"""
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import errno
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import logging
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import os
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import threading
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import time
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from contextlib import contextmanager
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from dataclasses import dataclass, replace
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from pathlib import Path
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from . import preview_location, thumbnail_settings
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try:
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from ...utils.media_folders import PREVIEW_FOLDER
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except ImportError: # tests import the package top-level
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from utils.media_folders import PREVIEW_FOLDER
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logger = logging.getLogger("prompt_manager.thumbnails")
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SOURCE_MODE = preview_location.SOURCE_MODE
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FOLDER_MODE = preview_location.FOLDER_MODE
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# The probe checks the folder this often, and a check (or a store call)
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# taking longer than the budget marks it unreachable.
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PROBE_INTERVAL = 5.0
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IO_BUDGET = 2.0
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PROBE_THREAD = "pm-preview-probe"
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@dataclass(frozen=True)
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class Location:
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"""One snapshot of the thumbnail location (take one per request or job)."""
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mode: str = SOURCE_MODE
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path: str | None = None
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available: bool = True
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problem: str | None = None
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generation: int = 0
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write_lock = threading.Lock()
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_generation = 0
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# The runtime location: the parsed setting, availability and the marker keys
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# last read. Swapped as a whole; readers take one snapshot.
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_state_lock = threading.Lock()
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_parsed = preview_location.ParsedLocation()
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_available = True
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_problem = None
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_keys = {}
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_key_cache = {}
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_clock = time.monotonic
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def current():
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"""The thumbnail location now."""
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with _state_lock:
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parsed, available, problem, generation_now = (
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_parsed,
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_available,
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_problem,
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_generation,
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)
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if parsed.mode == SOURCE_MODE:
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return Location(generation=generation_now)
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return Location(FOLDER_MODE, parsed.path, available, problem, generation_now)
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def setting():
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"""The parsed setting in use (``preview_location.ParsedLocation``)."""
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return _parsed
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def generation():
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return _generation
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def bump_generation():
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"""Invalidate every write that started before (under ``write_lock``)."""
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global _generation
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with write_lock:
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_generation += 1
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return _generation
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def _canonical(path):
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"""Resolved and case-folded, so paths compare on every OS."""
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return Path(os.path.normcase(os.path.realpath(str(path))))
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def _within(path, folder):
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return _canonical(path).is_relative_to(_canonical(folder))
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# ── the setting and availability ─────────────────────────────────────
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def configure(value, *, context=None, check=True):
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"""Use the ``thumbnails.location`` *value* (config.json) from now on.
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A folder location is validated against *context* (``startup`` rules: a
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problem other than an unreachable folder makes it ``invalid``), then
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checked once; the probe keeps checking it. Swapped under ``write_lock``
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with a generation bump, so no write that started before lands.
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"""
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global _parsed, _available, _problem, _generation
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parsed = preview_location.parse_location(value)
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problem = parsed.problem
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if parsed.mode == FOLDER_MODE and problem is None and context is not None:
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code = preview_location.location_problem(
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parsed.path, purpose="startup", context=context
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)
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if code == "location-unavailable":
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problem = "unreachable"
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elif code is not None:
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problem = "invalid"
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parsed = preview_location.ParsedLocation(
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mode=FOLDER_MODE,
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path=parsed.path,
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id=parsed.id,
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install=parsed.install,
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cleanup=parsed.cleanup,
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problem="invalid",
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)
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with write_lock:
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with _state_lock:
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_parsed = parsed
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_available = parsed.mode == SOURCE_MODE
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_problem = problem if parsed.mode == FOLDER_MODE else None
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_keys.clear()
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_key_cache.clear()
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_generation += 1
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if parsed.mode == FOLDER_MODE:
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if check and parsed.problem is None:
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refresh()
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_probe.start()
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else:
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_probe.stop()
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return current()
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def refresh():
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"""Check the folder now (bounded by IO_BUDGET); returns availability."""
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parsed = _parsed
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if parsed.mode != FOLDER_MODE or parsed.problem is not None:
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return parsed.mode == SOURCE_MODE
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try:
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available, problem, marker = _probe.check(parsed.path, parsed.id)
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except (OSError, TimeoutError, RuntimeError):
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available, problem, marker = False, "unreachable", None
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_set_state(parsed, available, problem, marker)
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return available
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def _set_keys(parsed, marker):
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"""Take the keys of a marker just written (availability unchanged)."""
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with _state_lock:
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if _parsed is not parsed:
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return
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keys = dict((marker or {}).get("keys") or {})
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if keys != _keys:
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_keys.clear()
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_keys.update(keys)
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_key_cache.clear()
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def mark_invalid():
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"""The setting cannot be used (a startup check that failed): folder
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mode stays in force, unavailable, so nothing is written anywhere."""
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global _parsed, _available, _problem
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with _state_lock:
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if _parsed.mode != FOLDER_MODE:
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_parsed = preview_location.ParsedLocation(
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mode=FOLDER_MODE, problem="invalid"
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)
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else:
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_parsed = replace(_parsed, problem="invalid")
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_available, _problem = False, "invalid"
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def _set_state(parsed, available, problem, marker):
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global _available, _problem
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with _state_lock:
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if _parsed is not parsed:
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return # the setting changed meanwhile
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_available, _problem = available, problem
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keys = dict((marker or {}).get("keys") or {})
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if keys != _keys:
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_keys.clear()
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_keys.update(keys)
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_key_cache.clear()
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def note_failure():
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"""A store call failed or stalled: unreachable until the probe finds the
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folder again (requests do no store I/O meanwhile)."""
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global _available, _problem
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if _parsed.mode != FOLDER_MODE:
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return
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with _state_lock:
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_available, _problem = False, "unreachable"
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_probe.wake()
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@contextmanager
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def store_io():
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"""Around a store call in folder mode: an I/O error (other than a file
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that is not there) or a call over IO_BUDGET marks the folder
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unreachable."""
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if _parsed.mode != FOLDER_MODE:
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yield
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return
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started = _clock()
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try:
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yield
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except OSError as error:
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if not isinstance(error, (FileNotFoundError, NotADirectoryError)):
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note_failure()
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raise
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finally:
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if _clock() - started > IO_BUDGET:
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note_failure()
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class _Probe:
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"""The background check of the thumbnail folder (one thread, one check
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at a time; a stuck check is left to finish on its own thread)."""
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def __init__(self):
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self._lock = threading.Lock()
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self._wake = threading.Event()
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self._stop = threading.Event()
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self._thread = None
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self._checking = None
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def check(self, path, expected_id):
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"""``folder_state`` within IO_BUDGET; raises TimeoutError. A check
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already running (the probe's, or a stuck one) is joined, never run
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twice at once."""
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with self._lock:
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pending = self._checking
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if pending is None or pending[0] != (path, expected_id):
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pending = self._start_check(path, expected_id)
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key, done, result = pending
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if not done.wait(IO_BUDGET):
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raise TimeoutError("the thumbnail folder did not answer in time")
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with self._lock:
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if self._checking is pending:
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self._checking = None
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if "error" in result:
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raise result["error"]
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return result["value"]
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def _start_check(self, path, expected_id):
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"""Start one check on its own thread (lock held)."""
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result = {}
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done = threading.Event()
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def run():
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try:
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result["value"] = preview_location.folder_state(path, expected_id)
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except BaseException as error: # handed to the caller
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result["error"] = error
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finally:
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done.set()
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pending = ((path, expected_id), done, result)
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self._checking = pending
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threading.Thread(target=run, name=PROBE_THREAD + "-check", daemon=True).start()
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return pending
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def start(self):
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with self._lock:
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if self._thread is not None and self._thread.is_alive():
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return
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# Each thread has its own stop: a stopped one never resumes.
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stop = self._stop = threading.Event()
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thread = threading.Thread(
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target=self._run, args=(stop,), name=PROBE_THREAD, daemon=True
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)
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try:
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thread.start()
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except RuntimeError:
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return # refused at interpreter exit: no probe
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self._thread = thread
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def _run(self, stop):
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while not stop.is_set():
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self._wake.wait(PROBE_INTERVAL)
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self._wake.clear()
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if stop.is_set():
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return
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try:
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refresh()
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except Exception: # one failed check never stops the probe
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logger.debug("Thumbnail folder check failed", exc_info=True)
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def wake(self):
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self._wake.set()
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def stop(self, timeout=2.0):
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"""Stop the probe; True when its thread ended."""
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with self._lock:
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thread, self._thread = self._thread, None
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self._stop.set()
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self._wake.set()
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if thread is None or thread is threading.current_thread():
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return True
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thread.join(timeout)
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return not thread.is_alive()
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_probe = _Probe()
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def stop_probe(timeout=2.0):
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"""Stop the folder probe (the package teardown, tests)."""
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return _probe.stop(timeout)
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# ── stores ───────────────────────────────────────────────────────────
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def source_folder(root):
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"""``<source>/thumbnails``: the store in source mode, a leftover in
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folder mode."""
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return Path(root) / PREVIEW_FOLDER
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def store_container(root, location=None):
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"""The folder a store of *root* must stay inside: the source itself, or
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the thumbnail folder in folder mode."""
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location = location or current()
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if location.mode == FOLDER_MODE:
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return Path(location.path) if location.path else None
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return Path(root)
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def _identity(root):
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return os.path.normcase(os.path.realpath(str(root)))
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def _lookup_key(root):
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spelling = str(root)
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with _state_lock:
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if spelling in _key_cache:
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return _key_cache[spelling]
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keys = dict(_keys)
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key = preview_location.find_key(
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keys,
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spelling,
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_identity(root),
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preview_location.file_identity(root),
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)
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if key is not None:
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with _state_lock:
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_key_cache[spelling] = key
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return key
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def store_dir(root, location=None):
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"""The store of *root*: ``<source>/thumbnails``, or in folder mode
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``<folder>/<key>`` (None while the folder is unavailable or before the
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source has a key: a reader then finds no preview)."""
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location = location or current()
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if location.mode == SOURCE_MODE:
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return Path(root) / PREVIEW_FOLDER
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if not location.available or not location.path:
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return None
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key = _lookup_key(root)
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return None if key is None else _key_folder(location.path, key)
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def _key_folder(folder, key):
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"""``<folder>/<key>``, only for a key that is one folder name directly
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below the thumbnail folder (a marker is data, never a path)."""
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if not preview_location.valid_key(key):
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return None
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store = Path(folder) / key
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if store.parent != Path(folder) or store.name != key:
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return None
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return store
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def ensure_store(root, location=None, *, create=False):
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"""``store_dir`` for a writer: in folder mode a source without a key gets
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one (recorded in the marker); with *create* its key folder is made (never
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the thumbnail folder itself). None while the folder is unavailable."""
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location = location or current()
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store = store_dir(root, location)
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if location.mode == SOURCE_MODE or (store is None and not location.available):
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return store
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if store is None:
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store = _assign_key(root, location)
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if store is None:
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return None
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if create:
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try:
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with store_io():
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os.mkdir(store)
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except FileExistsError:
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pass
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except OSError:
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return None
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return store
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def _assign_key(root, location):
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parsed = _parsed
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if location.path != parsed.path:
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return None
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spelling = str(root)
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identity = _identity(root)
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dev_ino = preview_location.file_identity(root)
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assigned = {}
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def add(marker):
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if marker.get("id") != parsed.id:
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raise ValueError("another folder's marker") # marker-mismatch
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keys = marker["keys"]
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key = preview_location.find_key(keys, spelling, identity, dev_ino)
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if key is None:
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taken = {k: v.get("identity") for k, v in keys.items()}
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key = preview_location.source_key(spelling, identity, taken)
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keys[key] = {
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"path": spelling,
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"identity": identity,
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"dev_ino": dev_ino,
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"install": parsed.install,
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}
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assigned["key"] = key
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try:
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with write_lock, store_io():
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marker = preview_location.write_marker(location.path, add)
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except (OSError, ValueError):
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return None
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_set_keys(parsed, marker)
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return _key_folder(location.path, assigned["key"])
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def may_write(path, location=None):
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"""The one ownership check every preview write and delete passes.
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Source mode: True (the callers' own root rules apply, as before). Folder
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mode: *path* lies below a source key folder of the thumbnail folder,
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lexically and resolved, and no link, junction or reparse point sits
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anywhere from the key folder down to it (the file itself included).
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"""
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location = location or current()
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if location.mode == SOURCE_MODE:
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return True
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if not location.path:
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return False
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folder = Path(os.path.abspath(location.path))
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path = Path(os.path.abspath(path))
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try:
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relative = path.relative_to(folder)
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except ValueError:
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return False
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if len(relative.parts) < 2 or ".." in relative.parts:
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return False
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store = _key_folder(folder, relative.parts[0])
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if store is None or not _within(path, folder):
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return False
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try:
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return _no_link_below(store, path)
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except OSError:
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note_failure()
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return False
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def make_parent(dst, location=None):
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"""Make the folders a preview *dst* is written into. In folder mode only
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folders below the thumbnail folder are made, never the folder itself,
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and only while it holds this install's marker (an unplugged drive or an
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unmounted mount point raises FileNotFoundError); a *dst* that does not
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pass ``may_write`` raises PermissionError."""
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location = location or current()
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dst = Path(dst)
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if location.mode == SOURCE_MODE or not location.path:
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if location.mode != SOURCE_MODE:
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raise FileNotFoundError(errno.ENOENT, "thumbnail folder unavailable")
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dst.parent.mkdir(parents=True, exist_ok=True)
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return
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folder = Path(os.path.abspath(location.path))
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with store_io():
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if not location.available or not folder.is_dir():
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raise FileNotFoundError(errno.ENOENT, "thumbnail folder unavailable")
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marker = preview_location.read_marker(str(folder))
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if marker is None or marker.get("id") != _parsed.id:
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note_failure()
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raise FileNotFoundError(errno.ENOENT, "thumbnail folder unavailable")
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if not may_write(dst, location):
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raise PermissionError(errno.EACCES, "outside the thumbnail folder")
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current_folder = folder
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for part in Path(os.path.abspath(dst.parent)).relative_to(folder).parts:
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|
current_folder = current_folder / part
|
|
try:
|
|
os.mkdir(current_folder)
|
|
except FileExistsError:
|
|
pass
|
|
if preview_location.is_link_like(current_folder):
|
|
raise PermissionError(errno.EACCES, "a link in the thumbnail folder")
|
|
|
|
|
|
def store_is_link(store, location=None):
|
|
"""Whether a store folder is a link (a junction or reparse point too in
|
|
folder mode): it is skipped by sweeps and refused by clears."""
|
|
location = location or current()
|
|
if location.mode == SOURCE_MODE:
|
|
return Path(store).is_symlink()
|
|
return preview_location.is_link_like(store)
|
|
|
|
|
|
def given_store(root, store):
|
|
"""A caller's explicit store argument: the default spelling
|
|
(``<root>/thumbnails``) means the resolver's store; another folder (only
|
|
tests pass one) is used as given."""
|
|
store = Path(store)
|
|
if store == Path(root) / PREVIEW_FOLDER:
|
|
return store_dir(root)
|
|
return store
|
|
|
|
|
|
def preview_path(root, media_rel, ext=None, location=None, *, create=False):
|
|
"""Where the preview of *media_rel* (relative to *root*) is, or is to be
|
|
written (*create*: a writer, which gives a new source its key), in *ext*
|
|
(the extension written now when None)."""
|
|
if create:
|
|
store = ensure_store(root, location)
|
|
else:
|
|
store = store_dir(root, location)
|
|
if store is None:
|
|
return None
|
|
if ext is None:
|
|
from .thumbnail_encode import writer_settings
|
|
|
|
ext = writer_settings().extension
|
|
return store / (thumbnail_settings.preview_stem(media_rel) + ext)
|
|
|
|
|
|
def request_path(root, parts, location=None):
|
|
"""The disk path of the URL parts ``("thumbnails", ...)``, or None when
|
|
*parts* is not under an exact ``thumbnails`` first part or the store has
|
|
no place for it. The text is checked before (``is_preview_text``)."""
|
|
parts = tuple(parts)
|
|
if len(parts) < 2 or parts[0] != PREVIEW_FOLDER:
|
|
return None
|
|
store = store_dir(root, location)
|
|
if store is None:
|
|
return None
|
|
return store.joinpath(*parts[1:])
|
|
|
|
|
|
def _no_link_below(store, path):
|
|
"""No folder from *store* down to *path* (and *store* itself) is a link,
|
|
junction or reparse point (lexical walk, one lstat each)."""
|
|
store = Path(os.path.abspath(store))
|
|
path = Path(os.path.abspath(path))
|
|
try:
|
|
relative = path.relative_to(store)
|
|
except ValueError:
|
|
return False
|
|
current = store
|
|
for part in ("",) + relative.parts:
|
|
current = current / part if part else current
|
|
if preview_location.is_link_like(current):
|
|
return False
|
|
return True
|
|
|
|
|
|
def owns(root, path, location=None):
|
|
"""Whether *path* lies inside the store of *root*, resolved: the store
|
|
stays inside its container and no link takes *path* out of the store.
|
|
In folder mode no link, junction or reparse point may sit anywhere from
|
|
the store down to *path*."""
|
|
location = location or current()
|
|
store = store_dir(root, location)
|
|
if store is None:
|
|
return False
|
|
container = store_container(root, location)
|
|
if not (_within(store, container) and _within(path, store)):
|
|
return False
|
|
if location.mode == SOURCE_MODE:
|
|
return True
|
|
return may_write(path, location)
|
|
|
|
|
|
# ── preview text ─────────────────────────────────────────────────────
|
|
|
|
|
|
def is_preview_text(filepath):
|
|
"""URL text naming a preview: ``thumbnails/<...>/<name>_thumb<ext>``.
|
|
|
|
Text only, before any join: no backslash, drive or stream colon, and no
|
|
empty, ``.`` or ``..`` segment; ``thumbnails`` exactly as the first part
|
|
and nowhere else among the folders; the extension, in any case, one a
|
|
preview may carry (``X_thumb.JPG`` of an older release included).
|
|
"""
|
|
if not filepath or "\\" in filepath or ":" in filepath:
|
|
return False
|
|
parts = filepath.split("/")
|
|
if len(parts) < 2 or parts[0] != PREVIEW_FOLDER:
|
|
return False
|
|
if any(part in ("", ".", "..") for part in parts):
|
|
return False
|
|
if PREVIEW_FOLDER in parts[1:-1]:
|
|
return False
|
|
stem, extension = os.path.splitext(parts[-1])
|
|
return (
|
|
stem.endswith(thumbnail_settings.THUMB_SUFFIX)
|
|
and len(stem) > len(thumbnail_settings.THUMB_SUFFIX)
|
|
and extension.lower() in thumbnail_settings.THUMBNAIL_EXTENSIONS
|
|
)
|
|
|
|
|
|
# ── writes ───────────────────────────────────────────────────────────
|
|
|
|
|
|
class _WriteGuard:
|
|
"""``guard()`` for one preview write: true while the location has not
|
|
changed since the write started and *hold* (if any) allows it."""
|
|
|
|
__slots__ = ("generation", "_hold")
|
|
|
|
def __init__(self, hold=None):
|
|
self.generation = _generation
|
|
self._hold = hold
|
|
|
|
def __call__(self):
|
|
if self.generation != _generation:
|
|
return False
|
|
return self._hold is None or bool(self._hold())
|
|
|
|
|
|
def write_guard(hold=None):
|
|
"""Take when a preview write starts; hand to its final rename."""
|
|
if isinstance(hold, _WriteGuard):
|
|
return hold
|
|
return _WriteGuard(hold)
|
|
|
|
|
|
@contextmanager
|
|
def committed(guard=None):
|
|
"""Around a preview's final rename: holds ``write_lock`` and yields
|
|
whether the write may land (``guard()``, re-checked under the lock)."""
|
|
with write_lock:
|
|
yield guard is None or bool(guard())
|