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145 lines
4.6 KiB
145 lines
4.6 KiB
"""Constructs a tree-like object containing the metadata for a given path, and caches said metadata."""
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import logging
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import mimetypes
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import os
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import uuid
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from typing import Dict, Optional, Union, List, Tuple, Any, cast
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import jstyleson
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from .utils import guess_mime
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# setup mimetypes with some extra ones
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mimetypes.init()
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mimetypes.add_type("text/html", "thtml")
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mimetypes.add_type("text/html", "cont")
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logger = logging.getLogger(__name__)
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class MetaCacheMiss(Exception):
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"""Raised on cache miss."""
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class MetaCache:
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"""This class provides an in-memory cache for metadata tree."""
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def __init__(self, max_age: float = 200.0):
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"""Initialize the cache.
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Arguments:
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max_age (int): the number of seconds to age-out cache items
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"""
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self._max_age = max_age
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self._cache: Dict[str, Tuple[float, Any]] = {}
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def get(self, key: str, new_time_stamp: float) -> Any:
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"""Get an item from the cache.
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Arguments:
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key (str): the cache key to retieve
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new_time_stamp (int): The time to use to compare the stored time with
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Returns:
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:obj:misc: The previously stored value.
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Raises:
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MetaCacheMiss: on missing key, or on aged out
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"""
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if key not in self._cache:
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raise MetaCacheMiss("no item for key {}".format(key))
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if self._cache[key][0] + self._max_age <= new_time_stamp:
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return self._cache[key][1]
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raise MetaCacheMiss("cache expired for key {}".format(key))
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def put(self, key: str, value: Union[Dict, List, int, str, object], time_stamp: float) -> None:
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"""Put an item into the cache.
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Arguments:
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key (str): the key to store the cache item under
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value (:obj:misc): the value to store
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time_stamp (float): the time stamp to store the item under
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"""
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self._cache[key] = (time_stamp, value)
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class MetaTree:
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"""This provides an interface to loading and caching tree metadata for a given directory tree."""
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def __init__(self, root: str, default_metadata: Optional[Dict] = None):
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"""Initialize the metadata tree object.
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Arguments:
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root (str): The path to the root of the file tree to operate on.
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default_metadata (dict, optional): The default metadata to apply to the tree
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"""
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self._cache = MetaCache()
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if default_metadata is None:
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default_metadata = {}
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self._default_metadata = default_metadata
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if root[-1] != "/":
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root += "/"
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self._root = root
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def get_metadata(self, rel_path: str) -> Dict:
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"""Retrieve the metadata for a given path
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The general procedure is to iterate the tree, at each level
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m load .meta (JSON formatted dictionary) for that level, and
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then finally load the path.meta, and merge these dictionaries
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in descendant order.
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Arguments:
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rel_path (str): The path to retrieve the metadata for (relative to root)
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Returns:
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dict: A dictionary of metadata for that path tree.
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"""
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metablob = dict(self._default_metadata)
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# iterate path components from root to target path
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comps = [self._root] + rel_path.split("/")
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fullpath = ""
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for pth in comps:
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fullpath = os.path.join(fullpath, pth)
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st = os.stat(fullpath)
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cachekey = fullpath + ".meta"
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meta = cast(Dict, {})
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try:
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st_meta = os.stat(cachekey)
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meta = self._cache.get(cachekey, st_meta.st_mtime)
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except FileNotFoundError:
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st_meta = None # type: ignore
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except MetaCacheMiss:
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meta = {}
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if not meta and st_meta:
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meta = jstyleson.load(open(cachekey, "r"))
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self._cache.put(cachekey, meta, st_meta.st_mtime)
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metablob.update(meta)
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# return final dict
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metablob["dir"], metablob["file_name"] = os.path.split(rel_path)
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metablob["file_path"] = rel_path
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metablob["uuid"] = uuid.uuid3(
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uuid.NAMESPACE_OID, metablob["uuid-oid-root"] + os.path.join(self._root, rel_path)
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)
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metablob["os-path"], _ = os.path.split(fullpath)
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metablob["guessed-type"] = guess_mime(os.path.join(self._root, rel_path))
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if "mime-type" not in metablob:
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metablob["mime-type"] = metablob["guessed-type"]
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metablob["stat"] = {}
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for stk in ("st_mtime", "st_ctime", "st_atime", "st_mode", "st_size", "st_ino"):
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metablob["stat"][stk.replace("st_", "")] = getattr(st, stk)
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return metablob
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