# MIT License
#
# Copyright The SCons Foundation
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be included
# in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
# KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
# WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
"""
dblite.py module contributed by Ralf W. Grosse-Kunstleve.
Extended for Unicode by Steven Knight.
This is a very simple-minded "database" used for saved signature
information, with an interface modeled on the Python dbm database
interface module.
"""
import io
import os
import pickle
import shutil
import time
from SCons.compat import PICKLE_PROTOCOL
KEEP_ALL_FILES = False
IGNORE_CORRUPT_DBFILES = False
def corruption_warning(filename) -> None:
"""Local warning for corrupt db.
Used for self-tests. SCons overwrites this with a
different warning function in SConsign.py.
"""
print("Warning: Discarding corrupt database:", filename)
DBLITE_SUFFIX = ".dblite"
TMP_SUFFIX = ".tmp"
[docs]
class _Dblite:
"""Lightweight signature database class.
Behaves like a dict when in memory, loads from a pickled disk
file on open and writes back out to it on close.
Open the database file using a path derived from *file_base_name*.
The optional *flag* argument can be:
+---------+---------------------------------------------------+
| Value | Meaning |
+=========+===================================================+
| ``'r'`` | Open existing database for reading only (default) |
+---------+---------------------------------------------------+
| ``'w'`` | Open existing database for reading and writing |
+---------+---------------------------------------------------+
| ``'c'`` | Open database for reading and writing, creating |
| | it if it doesn't exist |
+---------+---------------------------------------------------+
| ``'n'`` | Always create a new, empty database, open for |
| | reading and writing |
+---------+---------------------------------------------------+
The optional *mode* argument is the POSIX mode of the file, used only
when the database has to be created. It defaults to octal ``0o666``.
"""
# Because open() is defined at module level, overwriting builtin open
# in the scope of this module, we use io.open to avoid ambiguity.
_open = staticmethod(io.open)
# we need to squirrel away references to functions from various modules
# that we'll use when sync() is called: this may happen at Python
# teardown time (we call it from our __del__), and the global module
# references themselves may already have been rebound to None.
_pickle_dump = staticmethod(pickle.dump)
_pickle_protocol = PICKLE_PROTOCOL
try:
_os_chown = staticmethod(os.chown)
except AttributeError:
_os_chown = None
_os_replace = staticmethod(os.replace)
_os_chmod = staticmethod(os.chmod)
_shutil_copyfile = staticmethod(shutil.copyfile)
_time_time = staticmethod(time.time)
def __init__(self, file_base_name, flag='r', mode=0o666) -> None:
assert flag in ("r", "w", "c", "n")
base, ext = os.path.splitext(file_base_name)
if ext == DBLITE_SUFFIX:
# There's already a suffix on the file name, don't add one.
self._file_name = file_base_name
self._tmp_name = base + TMP_SUFFIX
else:
self._file_name = file_base_name + DBLITE_SUFFIX
self._tmp_name = file_base_name + TMP_SUFFIX
self._flag = flag
self._mode = mode
self._dict = {}
self._needs_sync = False
if self._os_chown is not None and 0 in (os.geteuid(), os.getegid()):
# running as root; chown back to current owner/group when done
try:
statinfo = os.stat(self._file_name)
self._chown_to = statinfo.st_uid
self._chgrp_to = statinfo.st_gid
except OSError:
# db file doesn't exist yet.
# Check os.environ for SUDO_UID, use if set
self._chown_to = int(os.environ.get('SUDO_UID', -1))
self._chgrp_to = int(os.environ.get('SUDO_GID', -1))
else:
self._chown_to = -1 # don't chown
self._chgrp_to = -1 # don't chgrp
if self._flag == "n":
with io.open(self._file_name, "wb", opener=self.opener):
return # just make sure it exists
else:
# We only need the disk file to slurp in the data. Updates are
# handled on close, db is mainained only in memory until then.
try:
with io.open(self._file_name, "rb") as f:
p = f.read()
except OSError as e:
# an error for file not to exist, unless flag is create
if self._flag != "c":
raise e
with io.open(self._file_name, "wb", opener=self.opener):
return # just make sure it exists
if len(p) > 0:
try:
self._dict = pickle.loads(p, encoding='bytes')
except (
pickle.UnpicklingError,
# Python3 docs:
# Note that other exceptions may also be raised during
# unpickling, including (but not necessarily limited to)
# AttributeError, EOFError, ImportError, and IndexError.
AttributeError,
EOFError,
ImportError,
IndexError,
):
if IGNORE_CORRUPT_DBFILES:
corruption_warning(self._file_name)
else:
raise
[docs]
def opener(self, path, flags):
"""Database open helper when creation may be needed.
The high-level Python open() function cannot specify a file mode
for creation. Using this as the opener with the saved mode lets
us do that.
"""
return os.open(path, flags, mode=self._mode)
[docs]
def close(self) -> None:
if self._needs_sync:
self.sync()
def __del__(self) -> None:
self.close()
[docs]
def sync(self) -> None:
"""Flush the database to disk.
This routine *must* succeed, since the in-memory and on-disk
copies are out of sync as soon as we do anything that changes
the in-memory version. Thus, to be cautious, flush to a
temporary file and then move it over with some error handling.
"""
self._check_writable()
with self._open(self._tmp_name, "wb", opener=self.opener) as f:
self._pickle_dump(self._dict, f, self._pickle_protocol)
try:
self._os_replace(self._tmp_name, self._file_name)
except PermissionError:
# If we couldn't replace due to perms, try to change and retry.
# This is mainly for Windows - on POSIX the file permissions
# don't matter, the os.replace would have worked anyway.
# We're giving up if the retry fails, just let the Python
# exception abort us.
try:
self._os_chmod(self._file_name, 0o777)
except PermissionError:
pass
self._os_replace(self._tmp_name, self._file_name)
if (
self._os_chown is not None and self._chown_to > 0
): # don't chown to root or -1
try:
self._os_chown(self._file_name, self._chown_to, self._chgrp_to)
except OSError:
pass
self._needs_sync = False
if KEEP_ALL_FILES:
self._shutil_copyfile(
self._file_name, f"{self._file_name}_{int(self._time_time())}"
)
[docs]
def _check_writable(self):
if self._flag == "r":
raise OSError(f"Read-only database: {self._file_name}")
def __getitem__(self, key):
return self._dict[key]
def __setitem__(self, key, value):
self._check_writable()
if not isinstance(key, str):
raise TypeError(f"key `{key}' must be a string but is {type(key)}")
if not isinstance(value, bytes):
raise TypeError(f"value `{value}' must be bytes but is {type(value)}")
self._dict[key] = value
self._needs_sync = True
def __delitem__(self, key):
del self._dict[key]
[docs]
def keys(self):
return self._dict.keys()
[docs]
def items(self):
return self._dict.items()
[docs]
def values(self):
return self._dict.values()
__iter__ = keys
def __contains__(self, key) -> bool:
return key in self._dict
def __len__(self) -> int:
return len(self._dict)
[docs]
def open(file, flag="r", mode: int = 0o666): # pylint: disable=redefined-builtin
return _Dblite(file, flag, mode)
[docs]
def _exercise():
db = open("tmp", "n")
assert len(db) == 0
db["foo"] = b"bar"
assert db["foo"] == b"bar"
db.sync()
db = open("tmp", "c")
assert len(db) == 1, len(db)
assert db["foo"] == b"bar"
db["bar"] = b"foo"
assert db["bar"] == b"foo"
db.sync()
db = open("tmp")
assert len(db) == 2, len(db)
assert db["foo"] == b"bar"
assert db["bar"] == b"foo"
try:
db.sync()
except OSError as e:
assert str(e) == "Read-only database: tmp.dblite"
else:
raise RuntimeError("IOError expected.")
db = open("tmp", "w")
assert len(db) == 2, len(db)
db["ping"] = b"pong"
db.sync()
try:
db[(1, 2)] = "tuple"
except TypeError as e:
assert str(e) == "key `(1, 2)' must be a string but is <class 'tuple'>", str(e)
else:
raise RuntimeError("TypeError exception expected")
try:
db["list"] = [1, 2]
except TypeError as e:
assert str(e) == "value `[1, 2]' must be bytes but is <class 'list'>", str(e)
else:
raise RuntimeError("TypeError exception expected")
db = open("tmp")
assert len(db) == 3, len(db)
db = open("tmp", "n")
assert len(db) == 0, len(db)
_Dblite._open("tmp.dblite", "w")
db = open("tmp")
_Dblite._open("tmp.dblite", "w").write("x")
try:
db = open("tmp")
except pickle.UnpicklingError:
pass
else:
raise RuntimeError("pickle exception expected.")
global IGNORE_CORRUPT_DBFILES
IGNORE_CORRUPT_DBFILES = True
db = open("tmp")
assert len(db) == 0, len(db)
os.unlink("tmp.dblite")
try:
db = open("tmp", "w")
except OSError as e:
assert str(e) == "[Errno 2] No such file or directory: 'tmp.dblite'", str(e)
else:
raise RuntimeError("IOError expected.")
print("Completed _exercise()")
if __name__ == "__main__":
_exercise()
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