diff options
Diffstat (limited to 'Lib/dbm/__init__.py')
| -rw-r--r-- | Lib/dbm/__init__.py | 189 |
1 files changed, 0 insertions, 189 deletions
diff --git a/Lib/dbm/__init__.py b/Lib/dbm/__init__.py deleted file mode 100644 index f65da52..0000000 --- a/Lib/dbm/__init__.py +++ /dev/null @@ -1,189 +0,0 @@ -"""Generic interface to all dbm clones. - -Use - - import dbm - d = dbm.open(file, 'w', 0o666) - -The returned object is a dbm.gnu, dbm.ndbm or dbm.dumb object, dependent on the -type of database being opened (determined by the whichdb function) in the case -of an existing dbm. If the dbm does not exist and the create or new flag ('c' -or 'n') was specified, the dbm type will be determined by the availability of -the modules (tested in the above order). - -It has the following interface (key and data are strings): - - d[key] = data # store data at key (may override data at - # existing key) - data = d[key] # retrieve data at key (raise KeyError if no - # such key) - del d[key] # delete data stored at key (raises KeyError - # if no such key) - flag = key in d # true if the key exists - list = d.keys() # return a list of all existing keys (slow!) - -Future versions may change the order in which implementations are -tested for existence, and add interfaces to other dbm-like -implementations. -""" - -__all__ = ['open', 'whichdb', 'error'] - -import io -import os -import struct -import sys - - -class error(Exception): - pass - -_names = ['dbm.gnu', 'dbm.ndbm', 'dbm.dumb'] -_defaultmod = None -_modules = {} - -error = (error, OSError) - -try: - from dbm import ndbm -except ImportError: - ndbm = None - - -def open(file, flag='r', mode=0o666): - """Open or create database at path given by *file*. - - Optional argument *flag* can be 'r' (default) for read-only access, 'w' - for read-write access of an existing database, 'c' for read-write access - to a new or existing database, and 'n' for read-write access to a new - database. - - Note: 'r' and 'w' fail if the database doesn't exist; 'c' creates it - only if it doesn't exist; and 'n' always creates a new database. - """ - global _defaultmod - if _defaultmod is None: - for name in _names: - try: - mod = __import__(name, fromlist=['open']) - except ImportError: - continue - if not _defaultmod: - _defaultmod = mod - _modules[name] = mod - if not _defaultmod: - raise ImportError("no dbm clone found; tried %s" % _names) - - # guess the type of an existing database, if not creating a new one - result = whichdb(file) if 'n' not in flag else None - if result is None: - # db doesn't exist or 'n' flag was specified to create a new db - if 'c' in flag or 'n' in flag: - # file doesn't exist and the new flag was used so use default type - mod = _defaultmod - else: - raise error[0]("db file doesn't exist; " - "use 'c' or 'n' flag to create a new db") - elif result == "": - # db type cannot be determined - raise error[0]("db type could not be determined") - elif result not in _modules: - raise error[0]("db type is {0}, but the module is not " - "available".format(result)) - else: - mod = _modules[result] - return mod.open(file, flag, mode) - - -def whichdb(filename): - """Guess which db package to use to open a db file. - - Return values: - - - None if the database file can't be read; - - empty string if the file can be read but can't be recognized - - the name of the dbm submodule (e.g. "ndbm" or "gnu") if recognized. - - Importing the given module may still fail, and opening the - database using that module may still fail. - """ - - # Check for ndbm first -- this has a .pag and a .dir file - try: - f = io.open(filename + ".pag", "rb") - f.close() - f = io.open(filename + ".dir", "rb") - f.close() - return "dbm.ndbm" - except OSError: - # some dbm emulations based on Berkeley DB generate a .db file - # some do not, but they should be caught by the bsd checks - try: - f = io.open(filename + ".db", "rb") - f.close() - # guarantee we can actually open the file using dbm - # kind of overkill, but since we are dealing with emulations - # it seems like a prudent step - if ndbm is not None: - d = ndbm.open(filename) - d.close() - return "dbm.ndbm" - except OSError: - pass - - # Check for dumbdbm next -- this has a .dir and a .dat file - try: - # First check for presence of files - os.stat(filename + ".dat") - size = os.stat(filename + ".dir").st_size - # dumbdbm files with no keys are empty - if size == 0: - return "dbm.dumb" - f = io.open(filename + ".dir", "rb") - try: - if f.read(1) in (b"'", b'"'): - return "dbm.dumb" - finally: - f.close() - except OSError: - pass - - # See if the file exists, return None if not - try: - f = io.open(filename, "rb") - except OSError: - return None - - with f: - # Read the start of the file -- the magic number - s16 = f.read(16) - s = s16[0:4] - - # Return "" if not at least 4 bytes - if len(s) != 4: - return "" - - # Convert to 4-byte int in native byte order -- return "" if impossible - try: - (magic,) = struct.unpack("=l", s) - except struct.error: - return "" - - # Check for GNU dbm - if magic in (0x13579ace, 0x13579acd, 0x13579acf): - return "dbm.gnu" - - # Later versions of Berkeley db hash file have a 12-byte pad in - # front of the file type - try: - (magic,) = struct.unpack("=l", s16[-4:]) - except struct.error: - return "" - - # Unknown - return "" - - -if __name__ == "__main__": - for filename in sys.argv[1:]: - print(whichdb(filename) or "UNKNOWN", filename) |