Source code for SCons.dblite

# MIT License
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# Copyright The SCons Foundation
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"""
dblite.py module contributed by Ralf W. Grosse-Kunstleve.
Extended for Unicode by Steven Knight.
"""

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):
    """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: """ Squirrel away references to the functions in various modules that we'll use when our __del__() method calls our sync() method during shutdown. We might get destroyed when Python is in the midst of tearing down the different modules we import in an essentially arbitrary order, and some of the various modules's global attributes may already be wiped out from under us. See the discussion at: http://mail.python.org/pipermail/python-bugs-list/2003-March/016877.html """ _open = open _pickle_dump = staticmethod(pickle.dump) _pickle_protocol = PICKLE_PROTOCOL try: _os_chown = os.chown except AttributeError: _os_chown = None _os_replace = os.replace _os_chmod = os.chmod _shutil_copyfile = shutil.copyfile _time_time = time.time def __init__(self, file_base_name, flag, mode): assert flag in (None, "r", "w", "c", "n") if flag is None: flag = "r" 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 (os.geteuid() == 0 or os.getuid() == 0): # 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 self._open(self._file_name, "wb", self._mode): pass # just make sure it exists else: try: f = self._open(self._file_name, "rb") except IOError as e: if self._flag != "c": raise e with self._open(self._file_name, "wb", self._mode): pass # just make sure it exists else: p = f.read() f.close() if len(p) > 0: try: self._dict = pickle.loads(p, encoding='bytes') except (pickle.UnpicklingError, EOFError, KeyError): # Note how we catch KeyErrors too here, which might happen # when we don't have cPickle available (default pickle # throws it). if IGNORE_CORRUPT_DBFILES: corruption_warning(self._file_name) else: raise
[docs] def close(self): if self._needs_sync: self.sync()
def __del__(self): self.close()
[docs] def sync(self): self._check_writable() with self._open(self._tmp_name, "wb", self._mode) 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, self._file_name + "_" + str(int(self._time_time())) )
[docs] def _check_writable(self): if self._flag == "r": raise IOError("Read-only database: %s" % 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("key `%s' must be a string but is %s" % (key, type(key))) if not isinstance(value, bytes): raise TypeError("value `%s' must be a bytes but is %s" % (value, type(value))) self._dict[key] = value self._needs_sync = True
[docs] def keys(self): return list(self._dict.keys())
def __contains__(self, key): return key in self._dict def __iter__(self): return iter(self._dict) def __len__(self): return len(self._dict)
[docs]def open(file, flag=None, mode=0o666): 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", "r") assert len(db) == 2, len(db) assert db["foo"] == b"bar" assert db["bar"] == b"foo" try: db.sync() except IOError 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 a bytes but is <class 'list'>", str(e) else: raise RuntimeError("TypeError exception expected") db = open("tmp", "r") assert len(db) == 3, len(db) db = open("tmp", "n") assert len(db) == 0, len(db) dblite._open("tmp.dblite", "w") db = open("tmp", "r") dblite._open("tmp.dblite", "w").write("x") try: db = open("tmp", "r") except pickle.UnpicklingError: pass else: raise RuntimeError("pickle exception expected.") global IGNORE_CORRUPT_DBFILES IGNORE_CORRUPT_DBFILES = True db = open("tmp", "r") assert len(db) == 0, len(db) os.unlink("tmp.dblite") try: db = open("tmp", "w") except IOError 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() # Local Variables: # tab-width:4 # indent-tabs-mode:nil # End: # vim: set expandtab tabstop=4 shiftwidth=4: