Python code coverage for Lib/dbm/init.py

#	count	content
1	n/a	"""Generic interface to all dbm clones.
2	n/a
3	n/a	Use
4	n/a
5	n/a	import dbm
6	n/a	d = dbm.open(file, 'w', 0o666)
7	n/a
8	n/a	The returned object is a dbm.gnu, dbm.ndbm or dbm.dumb object, dependent on the
9	n/a	type of database being opened (determined by the whichdb function) in the case
10	n/a	of an existing dbm. If the dbm does not exist and the create or new flag ('c'
11	n/a	or 'n') was specified, the dbm type will be determined by the availability of
12	n/a	the modules (tested in the above order).
13	n/a
14	n/a	It has the following interface (key and data are strings):
15	n/a
16	n/a	d[key] = data # store data at key (may override data at
17	n/a	# existing key)
18	n/a	data = d[key] # retrieve data at key (raise KeyError if no
19	n/a	# such key)
20	n/a	del d[key] # delete data stored at key (raises KeyError
21	n/a	# if no such key)
22	n/a	flag = key in d # true if the key exists
23	n/a	list = d.keys() # return a list of all existing keys (slow!)
24	n/a
25	n/a	Future versions may change the order in which implementations are
26	n/a	tested for existence, and add interfaces to other dbm-like
27	n/a	implementations.
28	n/a	"""
29	n/a
30	n/a	__all__ = ['open', 'whichdb', 'error']
31	n/a
32	n/a	import io
33	n/a	import os
34	n/a	import struct
35	n/a	import sys
36	n/a
37	n/a
38	n/a	class error(Exception):
39	n/a	pass
40	n/a
41	n/a	_names = ['dbm.gnu', 'dbm.ndbm', 'dbm.dumb']
42	n/a	_defaultmod = None
43	n/a	_modules = {}
44	n/a
45	n/a	error = (error, OSError)
46	n/a
47	n/a	try:
48	n/a	from dbm import ndbm
49	n/a	except ImportError:
50	n/a	ndbm = None
51	n/a
52	n/a
53	n/a	def open(file, flag='r', mode=0o666):
54	n/a	"""Open or create database at path given by file.
55	n/a
56	n/a	Optional argument flag can be 'r' (default) for read-only access, 'w'
57	n/a	for read-write access of an existing database, 'c' for read-write access
58	n/a	to a new or existing database, and 'n' for read-write access to a new
59	n/a	database.
60	n/a
61	n/a	Note: 'r' and 'w' fail if the database doesn't exist; 'c' creates it
62	n/a	only if it doesn't exist; and 'n' always creates a new database.
63	n/a	"""
64	n/a	global _defaultmod
65	n/a	if _defaultmod is None:
66	n/a	for name in _names:
67	n/a	try:
68	n/a	mod = __import__(name, fromlist=['open'])
69	n/a	except ImportError:
70	n/a	continue
71	n/a	if not _defaultmod:
72	n/a	_defaultmod = mod
73	n/a	_modules[name] = mod
74	n/a	if not _defaultmod:
75	n/a	raise ImportError("no dbm clone found; tried %s" % _names)
76	n/a
77	n/a	# guess the type of an existing database, if not creating a new one
78	n/a	result = whichdb(file) if 'n' not in flag else None
79	n/a	if result is None:
80	n/a	# db doesn't exist or 'n' flag was specified to create a new db
81	n/a	if 'c' in flag or 'n' in flag:
82	n/a	# file doesn't exist and the new flag was used so use default type
83	n/a	mod = _defaultmod
84	n/a	else:
85	n/a	raise error[0]("need 'c' or 'n' flag to open new db")
86	n/a	elif result == "":
87	n/a	# db type cannot be determined
88	n/a	raise error[0]("db type could not be determined")
89	n/a	elif result not in _modules:
90	n/a	raise error[0]("db type is {0}, but the module is not "
91	n/a	"available".format(result))
92	n/a	else:
93	n/a	mod = _modules[result]
94	n/a	return mod.open(file, flag, mode)
95	n/a
96	n/a
97	n/a	def whichdb(filename):
98	n/a	"""Guess which db package to use to open a db file.
99	n/a
100	n/a	Return values:
101	n/a
102	n/a	- None if the database file can't be read;
103	n/a	- empty string if the file can be read but can't be recognized
104	n/a	- the name of the dbm submodule (e.g. "ndbm" or "gnu") if recognized.
105	n/a
106	n/a	Importing the given module may still fail, and opening the
107	n/a	database using that module may still fail.
108	n/a	"""
109	n/a
110	n/a	# Check for ndbm first -- this has a .pag and a .dir file
111	n/a	try:
112	n/a	f = io.open(filename + ".pag", "rb")
113	n/a	f.close()
114	n/a	f = io.open(filename + ".dir", "rb")
115	n/a	f.close()
116	n/a	return "dbm.ndbm"
117	n/a	except OSError:
118	n/a	# some dbm emulations based on Berkeley DB generate a .db file
119	n/a	# some do not, but they should be caught by the bsd checks
120	n/a	try:
121	n/a	f = io.open(filename + ".db", "rb")
122	n/a	f.close()
123	n/a	# guarantee we can actually open the file using dbm
124	n/a	# kind of overkill, but since we are dealing with emulations
125	n/a	# it seems like a prudent step
126	n/a	if ndbm is not None:
127	n/a	d = ndbm.open(filename)
128	n/a	d.close()
129	n/a	return "dbm.ndbm"
130	n/a	except OSError:
131	n/a	pass
132	n/a
133	n/a	# Check for dumbdbm next -- this has a .dir and a .dat file
134	n/a	try:
135	n/a	# First check for presence of files
136	n/a	os.stat(filename + ".dat")
137	n/a	size = os.stat(filename + ".dir").st_size
138	n/a	# dumbdbm files with no keys are empty
139	n/a	if size == 0:
140	n/a	return "dbm.dumb"
141	n/a	f = io.open(filename + ".dir", "rb")
142	n/a	try:
143	n/a	if f.read(1) in (b"'", b'"'):
144	n/a	return "dbm.dumb"
145	n/a	finally:
146	n/a	f.close()
147	n/a	except OSError:
148	n/a	pass
149	n/a
150	n/a	# See if the file exists, return None if not
151	n/a	try:
152	n/a	f = io.open(filename, "rb")
153	n/a	except OSError:
154	n/a	return None
155	n/a
156	n/a	with f:
157	n/a	# Read the start of the file -- the magic number
158	n/a	s16 = f.read(16)
159	n/a	s = s16[0:4]
160	n/a
161	n/a	# Return "" if not at least 4 bytes
162	n/a	if len(s) != 4:
163	n/a	return ""
164	n/a
165	n/a	# Convert to 4-byte int in native byte order -- return "" if impossible
166	n/a	try:
167	n/a	(magic,) = struct.unpack("=l", s)
168	n/a	except struct.error:
169	n/a	return ""
170	n/a
171	n/a	# Check for GNU dbm
172	n/a	if magic in (0x13579ace, 0x13579acd, 0x13579acf):
173	n/a	return "dbm.gnu"
174	n/a
175	n/a	# Later versions of Berkeley db hash file have a 12-byte pad in
176	n/a	# front of the file type
177	n/a	try:
178	n/a	(magic,) = struct.unpack("=l", s16[-4:])
179	n/a	except struct.error:
180	n/a	return ""
181	n/a
182	n/a	# Unknown
183	n/a	return ""
184	n/a
185	n/a
186	n/a	if __name__ == "__main__":
187	n/a	for filename in sys.argv[1:]:
188	n/a	print(whichdb(filename) or "UNKNOWN", filename)

Python code coverage for Lib/dbm/__init__.py

Python code coverage for Lib/dbm/init.py