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365 lines
12 KiB
365 lines
12 KiB
3 years ago
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"""The optional bytecode cache system. This is useful if you have very
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complex template situations and the compilation of all those templates
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slows down your application too much.
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Situations where this is useful are often forking web applications that
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are initialized on the first request.
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"""
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import errno
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import fnmatch
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import marshal
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import os
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import pickle
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import stat
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import sys
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import tempfile
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import typing as t
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from hashlib import sha1
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from io import BytesIO
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from types import CodeType
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if t.TYPE_CHECKING:
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import typing_extensions as te
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from .environment import Environment
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class _MemcachedClient(te.Protocol):
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def get(self, key: str) -> bytes:
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...
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def set(self, key: str, value: bytes, timeout: t.Optional[int] = None) -> None:
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...
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bc_version = 5
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# Magic bytes to identify Jinja bytecode cache files. Contains the
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# Python major and minor version to avoid loading incompatible bytecode
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# if a project upgrades its Python version.
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bc_magic = (
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b"j2"
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+ pickle.dumps(bc_version, 2)
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+ pickle.dumps((sys.version_info[0] << 24) | sys.version_info[1], 2)
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)
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class Bucket:
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"""Buckets are used to store the bytecode for one template. It's created
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and initialized by the bytecode cache and passed to the loading functions.
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The buckets get an internal checksum from the cache assigned and use this
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to automatically reject outdated cache material. Individual bytecode
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cache subclasses don't have to care about cache invalidation.
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"""
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def __init__(self, environment: "Environment", key: str, checksum: str) -> None:
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self.environment = environment
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self.key = key
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self.checksum = checksum
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self.reset()
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def reset(self) -> None:
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"""Resets the bucket (unloads the bytecode)."""
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self.code: t.Optional[CodeType] = None
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def load_bytecode(self, f: t.BinaryIO) -> None:
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"""Loads bytecode from a file or file like object."""
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# make sure the magic header is correct
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magic = f.read(len(bc_magic))
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if magic != bc_magic:
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self.reset()
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return
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# the source code of the file changed, we need to reload
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checksum = pickle.load(f)
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if self.checksum != checksum:
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self.reset()
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return
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# if marshal_load fails then we need to reload
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try:
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self.code = marshal.load(f)
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except (EOFError, ValueError, TypeError):
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self.reset()
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return
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def write_bytecode(self, f: t.BinaryIO) -> None:
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"""Dump the bytecode into the file or file like object passed."""
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if self.code is None:
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raise TypeError("can't write empty bucket")
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f.write(bc_magic)
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pickle.dump(self.checksum, f, 2)
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marshal.dump(self.code, f)
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def bytecode_from_string(self, string: bytes) -> None:
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"""Load bytecode from bytes."""
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self.load_bytecode(BytesIO(string))
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def bytecode_to_string(self) -> bytes:
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"""Return the bytecode as bytes."""
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out = BytesIO()
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self.write_bytecode(out)
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return out.getvalue()
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class BytecodeCache:
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"""To implement your own bytecode cache you have to subclass this class
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and override :meth:`load_bytecode` and :meth:`dump_bytecode`. Both of
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these methods are passed a :class:`~jinja2.bccache.Bucket`.
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A very basic bytecode cache that saves the bytecode on the file system::
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from os import path
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class MyCache(BytecodeCache):
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def __init__(self, directory):
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self.directory = directory
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def load_bytecode(self, bucket):
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filename = path.join(self.directory, bucket.key)
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if path.exists(filename):
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with open(filename, 'rb') as f:
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bucket.load_bytecode(f)
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def dump_bytecode(self, bucket):
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filename = path.join(self.directory, bucket.key)
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with open(filename, 'wb') as f:
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bucket.write_bytecode(f)
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A more advanced version of a filesystem based bytecode cache is part of
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Jinja.
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"""
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def load_bytecode(self, bucket: Bucket) -> None:
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"""Subclasses have to override this method to load bytecode into a
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bucket. If they are not able to find code in the cache for the
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bucket, it must not do anything.
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"""
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raise NotImplementedError()
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def dump_bytecode(self, bucket: Bucket) -> None:
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"""Subclasses have to override this method to write the bytecode
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from a bucket back to the cache. If it unable to do so it must not
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fail silently but raise an exception.
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"""
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raise NotImplementedError()
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def clear(self) -> None:
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"""Clears the cache. This method is not used by Jinja but should be
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implemented to allow applications to clear the bytecode cache used
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by a particular environment.
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"""
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def get_cache_key(
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self, name: str, filename: t.Optional[t.Union[str]] = None
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) -> str:
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"""Returns the unique hash key for this template name."""
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hash = sha1(name.encode("utf-8"))
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if filename is not None:
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hash.update(f"|{filename}".encode())
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return hash.hexdigest()
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def get_source_checksum(self, source: str) -> str:
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"""Returns a checksum for the source."""
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return sha1(source.encode("utf-8")).hexdigest()
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def get_bucket(
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self,
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environment: "Environment",
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name: str,
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filename: t.Optional[str],
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source: str,
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) -> Bucket:
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"""Return a cache bucket for the given template. All arguments are
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mandatory but filename may be `None`.
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"""
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key = self.get_cache_key(name, filename)
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checksum = self.get_source_checksum(source)
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bucket = Bucket(environment, key, checksum)
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self.load_bytecode(bucket)
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return bucket
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def set_bucket(self, bucket: Bucket) -> None:
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"""Put the bucket into the cache."""
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self.dump_bytecode(bucket)
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class FileSystemBytecodeCache(BytecodeCache):
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"""A bytecode cache that stores bytecode on the filesystem. It accepts
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two arguments: The directory where the cache items are stored and a
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pattern string that is used to build the filename.
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If no directory is specified a default cache directory is selected. On
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Windows the user's temp directory is used, on UNIX systems a directory
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is created for the user in the system temp directory.
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The pattern can be used to have multiple separate caches operate on the
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same directory. The default pattern is ``'__jinja2_%s.cache'``. ``%s``
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is replaced with the cache key.
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>>> bcc = FileSystemBytecodeCache('/tmp/jinja_cache', '%s.cache')
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This bytecode cache supports clearing of the cache using the clear method.
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"""
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def __init__(
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self, directory: t.Optional[str] = None, pattern: str = "__jinja2_%s.cache"
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) -> None:
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if directory is None:
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directory = self._get_default_cache_dir()
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self.directory = directory
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self.pattern = pattern
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def _get_default_cache_dir(self) -> str:
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def _unsafe_dir() -> "te.NoReturn":
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raise RuntimeError(
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"Cannot determine safe temp directory. You "
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"need to explicitly provide one."
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)
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tmpdir = tempfile.gettempdir()
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# On windows the temporary directory is used specific unless
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# explicitly forced otherwise. We can just use that.
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if os.name == "nt":
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return tmpdir
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if not hasattr(os, "getuid"):
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_unsafe_dir()
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dirname = f"_jinja2-cache-{os.getuid()}"
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actual_dir = os.path.join(tmpdir, dirname)
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try:
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os.mkdir(actual_dir, stat.S_IRWXU)
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except OSError as e:
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if e.errno != errno.EEXIST:
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raise
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try:
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os.chmod(actual_dir, stat.S_IRWXU)
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actual_dir_stat = os.lstat(actual_dir)
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if (
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actual_dir_stat.st_uid != os.getuid()
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or not stat.S_ISDIR(actual_dir_stat.st_mode)
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or stat.S_IMODE(actual_dir_stat.st_mode) != stat.S_IRWXU
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):
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_unsafe_dir()
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except OSError as e:
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if e.errno != errno.EEXIST:
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raise
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actual_dir_stat = os.lstat(actual_dir)
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if (
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actual_dir_stat.st_uid != os.getuid()
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or not stat.S_ISDIR(actual_dir_stat.st_mode)
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or stat.S_IMODE(actual_dir_stat.st_mode) != stat.S_IRWXU
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):
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_unsafe_dir()
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return actual_dir
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def _get_cache_filename(self, bucket: Bucket) -> str:
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return os.path.join(self.directory, self.pattern % (bucket.key,))
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def load_bytecode(self, bucket: Bucket) -> None:
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filename = self._get_cache_filename(bucket)
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if os.path.exists(filename):
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with open(filename, "rb") as f:
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bucket.load_bytecode(f)
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def dump_bytecode(self, bucket: Bucket) -> None:
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with open(self._get_cache_filename(bucket), "wb") as f:
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bucket.write_bytecode(f)
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def clear(self) -> None:
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# imported lazily here because google app-engine doesn't support
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# write access on the file system and the function does not exist
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# normally.
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from os import remove
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files = fnmatch.filter(os.listdir(self.directory), self.pattern % ("*",))
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for filename in files:
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try:
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remove(os.path.join(self.directory, filename))
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except OSError:
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pass
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class MemcachedBytecodeCache(BytecodeCache):
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"""This class implements a bytecode cache that uses a memcache cache for
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storing the information. It does not enforce a specific memcache library
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(tummy's memcache or cmemcache) but will accept any class that provides
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the minimal interface required.
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Libraries compatible with this class:
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- `cachelib <https://github.com/pallets/cachelib>`_
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- `python-memcached <https://pypi.org/project/python-memcached/>`_
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(Unfortunately the django cache interface is not compatible because it
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does not support storing binary data, only text. You can however pass
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the underlying cache client to the bytecode cache which is available
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as `django.core.cache.cache._client`.)
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The minimal interface for the client passed to the constructor is this:
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.. class:: MinimalClientInterface
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.. method:: set(key, value[, timeout])
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Stores the bytecode in the cache. `value` is a string and
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`timeout` the timeout of the key. If timeout is not provided
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a default timeout or no timeout should be assumed, if it's
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provided it's an integer with the number of seconds the cache
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item should exist.
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.. method:: get(key)
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Returns the value for the cache key. If the item does not
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exist in the cache the return value must be `None`.
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The other arguments to the constructor are the prefix for all keys that
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is added before the actual cache key and the timeout for the bytecode in
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the cache system. We recommend a high (or no) timeout.
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This bytecode cache does not support clearing of used items in the cache.
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The clear method is a no-operation function.
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.. versionadded:: 2.7
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Added support for ignoring memcache errors through the
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`ignore_memcache_errors` parameter.
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"""
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def __init__(
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self,
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client: "_MemcachedClient",
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prefix: str = "jinja2/bytecode/",
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timeout: t.Optional[int] = None,
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ignore_memcache_errors: bool = True,
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):
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self.client = client
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self.prefix = prefix
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self.timeout = timeout
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self.ignore_memcache_errors = ignore_memcache_errors
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def load_bytecode(self, bucket: Bucket) -> None:
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try:
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code = self.client.get(self.prefix + bucket.key)
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except Exception:
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if not self.ignore_memcache_errors:
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raise
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else:
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bucket.bytecode_from_string(code)
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def dump_bytecode(self, bucket: Bucket) -> None:
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key = self.prefix + bucket.key
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value = bucket.bytecode_to_string()
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try:
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if self.timeout is not None:
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self.client.set(key, value, self.timeout)
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else:
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self.client.set(key, value)
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except Exception:
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if not self.ignore_memcache_errors:
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raise
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