Current File : //lib/python3/dist-packages/twisted/persisted/dirdbm.py
# -*- test-case-name: twisted.test.test_dirdbm -*-
#
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.
"""
DBM-style interface to a directory.
Each key is stored as a single file. This is not expected to be very fast or
efficient, but it's good for easy debugging.
DirDBMs are *not* thread-safe, they should only be accessed by one thread at
a time.
No files should be placed in the working directory of a DirDBM save those
created by the DirDBM itself!
Maintainer: Itamar Shtull-Trauring
"""
import base64
import glob
import os
import pickle
from twisted.python.filepath import FilePath
try:
_open # type: ignore[has-type, used-before-def]
except NameError:
_open = open
class DirDBM:
"""
A directory with a DBM interface.
This class presents a hash-like interface to a directory of small,
flat files. It can only use strings as keys or values.
"""
def __init__(self, name):
"""
@type name: str
@param name: Base path to use for the directory storage.
"""
self.dname = os.path.abspath(name)
self._dnamePath = FilePath(name)
if not self._dnamePath.isdir():
self._dnamePath.createDirectory()
else:
# Run recovery, in case we crashed. we delete all files ending
# with ".new". Then we find all files who end with ".rpl". If a
# corresponding file exists without ".rpl", we assume the write
# failed and delete the ".rpl" file. If only a ".rpl" exist we
# assume the program crashed right after deleting the old entry
# but before renaming the replacement entry.
#
# NOTE: '.' is NOT in the base64 alphabet!
for f in glob.glob(self._dnamePath.child("*.new").path):
os.remove(f)
replacements = glob.glob(self._dnamePath.child("*.rpl").path)
for f in replacements:
old = f[:-4]
if os.path.exists(old):
os.remove(f)
else:
os.rename(f, old)
def _encode(self, k):
"""
Encode a key so it can be used as a filename.
"""
# NOTE: '_' is NOT in the base64 alphabet!
return base64.encodebytes(k).replace(b"\n", b"_").replace(b"/", b"-")
def _decode(self, k):
"""
Decode a filename to get the key.
"""
return base64.decodebytes(k.replace(b"_", b"\n").replace(b"-", b"/"))
def _readFile(self, path):
"""
Read in the contents of a file.
Override in subclasses to e.g. provide transparently encrypted dirdbm.
"""
with _open(path.path, "rb") as f:
s = f.read()
return s
def _writeFile(self, path, data):
"""
Write data to a file.
Override in subclasses to e.g. provide transparently encrypted dirdbm.
"""
with _open(path.path, "wb") as f:
f.write(data)
f.flush()
def __len__(self):
"""
@return: The number of key/value pairs in this Shelf
"""
return len(self._dnamePath.listdir())
def __setitem__(self, k, v):
"""
C{dirdbm[k] = v}
Create or modify a textfile in this directory
@type k: bytes
@param k: key to set
@type v: bytes
@param v: value to associate with C{k}
"""
if not type(k) == bytes:
raise TypeError("DirDBM key must be bytes")
if not type(v) == bytes:
raise TypeError("DirDBM value must be bytes")
k = self._encode(k)
# We create a new file with extension .new, write the data to it, and
# if the write succeeds delete the old file and rename the new one.
old = self._dnamePath.child(k)
if old.exists():
new = old.siblingExtension(".rpl") # Replacement entry
else:
new = old.siblingExtension(".new") # New entry
try:
self._writeFile(new, v)
except BaseException:
new.remove()
raise
else:
if old.exists():
old.remove()
new.moveTo(old)
def __getitem__(self, k):
"""
C{dirdbm[k]}
Get the contents of a file in this directory as a string.
@type k: bytes
@param k: key to lookup
@return: The value associated with C{k}
@raise KeyError: Raised when there is no such key
"""
if not type(k) == bytes:
raise TypeError("DirDBM key must be bytes")
path = self._dnamePath.child(self._encode(k))
try:
return self._readFile(path)
except OSError:
raise KeyError(k)
def __delitem__(self, k):
"""
C{del dirdbm[foo]}
Delete a file in this directory.
@type k: bytes
@param k: key to delete
@raise KeyError: Raised when there is no such key
"""
if not type(k) == bytes:
raise TypeError("DirDBM key must be bytes")
k = self._encode(k)
try:
self._dnamePath.child(k).remove()
except OSError:
raise KeyError(self._decode(k))
def keys(self):
"""
@return: a L{list} of filenames (keys).
"""
return list(map(self._decode, self._dnamePath.asBytesMode().listdir()))
def values(self):
"""
@return: a L{list} of file-contents (values).
"""
vals = []
keys = self.keys()
for key in keys:
vals.append(self[key])
return vals
def items(self):
"""
@return: a L{list} of 2-tuples containing key/value pairs.
"""
items = []
keys = self.keys()
for key in keys:
items.append((key, self[key]))
return items
def has_key(self, key):
"""
@type key: bytes
@param key: The key to test
@return: A true value if this dirdbm has the specified key, a false
value otherwise.
"""
if not type(key) == bytes:
raise TypeError("DirDBM key must be bytes")
key = self._encode(key)
return self._dnamePath.child(key).isfile()
def setdefault(self, key, value):
"""
@type key: bytes
@param key: The key to lookup
@param value: The value to associate with key if key is not already
associated with a value.
"""
if key not in self:
self[key] = value
return value
return self[key]
def get(self, key, default=None):
"""
@type key: bytes
@param key: The key to lookup
@param default: The value to return if the given key does not exist
@return: The value associated with C{key} or C{default} if not
L{DirDBM.has_key(key)}
"""
if key in self:
return self[key]
else:
return default
def __contains__(self, key):
"""
@see: L{DirDBM.has_key}
"""
return self.has_key(key)
def update(self, dict):
"""
Add all the key/value pairs in L{dict} to this dirdbm. Any conflicting
keys will be overwritten with the values from L{dict}.
@type dict: mapping
@param dict: A mapping of key/value pairs to add to this dirdbm.
"""
for key, val in dict.items():
self[key] = val
def copyTo(self, path):
"""
Copy the contents of this dirdbm to the dirdbm at C{path}.
@type path: L{str}
@param path: The path of the dirdbm to copy to. If a dirdbm
exists at the destination path, it is cleared first.
@rtype: C{DirDBM}
@return: The dirdbm this dirdbm was copied to.
"""
path = FilePath(path)
assert path != self._dnamePath
d = self.__class__(path.path)
d.clear()
for k in self.keys():
d[k] = self[k]
return d
def clear(self):
"""
Delete all key/value pairs in this dirdbm.
"""
for k in self.keys():
del self[k]
def close(self):
"""
Close this dbm: no-op, for dbm-style interface compliance.
"""
def getModificationTime(self, key):
"""
Returns modification time of an entry.
@return: Last modification date (seconds since epoch) of entry C{key}
@raise KeyError: Raised when there is no such key
"""
if not type(key) == bytes:
raise TypeError("DirDBM key must be bytes")
path = self._dnamePath.child(self._encode(key))
if path.isfile():
return path.getModificationTime()
else:
raise KeyError(key)
class Shelf(DirDBM):
"""
A directory with a DBM shelf interface.
This class presents a hash-like interface to a directory of small,
flat files. Keys must be strings, but values can be any given object.
"""
def __setitem__(self, k, v):
"""
C{shelf[foo] = bar}
Create or modify a textfile in this directory.
@type k: str
@param k: The key to set
@param v: The value to associate with C{key}
"""
v = pickle.dumps(v)
DirDBM.__setitem__(self, k, v)
def __getitem__(self, k):
"""
C{dirdbm[foo]}
Get and unpickle the contents of a file in this directory.
@type k: bytes
@param k: The key to lookup
@return: The value associated with the given key
@raise KeyError: Raised if the given key does not exist
"""
return pickle.loads(DirDBM.__getitem__(self, k))
def open(file, flag=None, mode=None):
"""
This is for 'anydbm' compatibility.
@param file: The parameter to pass to the DirDBM constructor.
@param flag: ignored
@param mode: ignored
"""
return DirDBM(file)
__all__ = ["open", "DirDBM", "Shelf"]
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