Staging
v0.5.1
v0.5.1
https://github.com/python/cpython
Tip revision: 74f4bd53e03ded8408bcc2de67cf0f5a4ac5b1a1 authored by Barry Warsaw on 23 February 2012, 15:59:38 UTC
Bump some more copyright years (as per PEP 101), since this is the first
Bump some more copyright years (as per PEP 101), since this is the first
Tip revision: 74f4bd5
whichdb.py
# !/usr/bin/env python
"""Guess which db package to use to open a db file."""
import os
import struct
import sys
try:
import dbm
_dbmerror = dbm.error
except ImportError:
dbm = None
# just some sort of valid exception which might be raised in the
# dbm test
_dbmerror = IOError
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 module name (e.g. "dbm" or "gdbm") if recognized.
Importing the given module may still fail, and opening the
database using that module may still fail.
"""
# Check for dbm first -- this has a .pag and a .dir file
try:
f = open(filename + os.extsep + "pag", "rb")
f.close()
# dbm linked with gdbm on OS/2 doesn't have .dir file
if not (dbm.library == "GNU gdbm" and sys.platform == "os2emx"):
f = open(filename + os.extsep + "dir", "rb")
f.close()
return "dbm"
except IOError:
# some dbm emulations based on Berkeley DB generate a .db file
# some do not, but they should be caught by the dbhash checks
try:
f = open(filename + os.extsep + "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 dbm is not None:
d = dbm.open(filename)
d.close()
return "dbm"
except (IOError, _dbmerror):
pass
# Check for dumbdbm next -- this has a .dir and a .dat file
try:
# First check for presence of files
os.stat(filename + os.extsep + "dat")
size = os.stat(filename + os.extsep + "dir").st_size
# dumbdbm files with no keys are empty
if size == 0:
return "dumbdbm"
f = open(filename + os.extsep + "dir", "rb")
try:
if f.read(1) in ("'", '"'):
return "dumbdbm"
finally:
f.close()
except (OSError, IOError):
pass
# See if the file exists, return None if not
try:
f = open(filename, "rb")
except IOError:
return None
# Read the start of the file -- the magic number
s16 = f.read(16)
f.close()
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 == 0x13579ace:
return "gdbm"
# Check for old Berkeley db hash file format v2
if magic in (0x00061561, 0x61150600):
return "bsddb185"
# 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 ""
# Check for BSD hash
if magic in (0x00061561, 0x61150600):
return "dbhash"
# Unknown
return ""
if __name__ == "__main__":
for filename in sys.argv[1:]:
print whichdb(filename) or "UNKNOWN", filename