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a1e93e8dfc
At this point, the problem appears particular to the OS/2 EMX port of gdbm (which is at v1.7.3) - this combination produces a .pag file but no .dir file. A more sophisticated patch which checks magic numbers when dbm.library indicates that dbm is linked to gdbm, and there is no .dir file, is still attached to the above patch entry for reconsideration after 2.3 is released. This checkin applies a workaround specific to the known failure case.
112 lines
3.1 KiB
Python
112 lines
3.1 KiB
Python
"""Guess which db package to use to open a db file."""
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import os
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import struct
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import sys
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try:
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import dbm
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_dbmerror = dbm.error
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except ImportError:
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dbm = None
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# just some sort of valid exception which might be raised in the
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# dbm test
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_dbmerror = IOError
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def whichdb(filename):
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"""Guess which db package to use to open a db file.
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Return values:
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- None if the database file can't be read;
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- empty string if the file can be read but can't be recognized
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- the module name (e.g. "dbm" or "gdbm") if recognized.
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Importing the given module may still fail, and opening the
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database using that module may still fail.
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"""
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# Check for dbm first -- this has a .pag and a .dir file
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try:
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f = open(filename + os.extsep + "pag", "rb")
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f.close()
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# dbm linked with gdbm on OS/2 doesn't have .dir file
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if not (dbm.library == "GNU gdbm" and sys.platform == "os2emx"):
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f = open(filename + os.extsep + "dir", "rb")
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f.close()
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return "dbm"
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except IOError:
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# some dbm emulations based on Berkeley DB generate a .db file
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# some do not, but they should be caught by the dbhash checks
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try:
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f = open(filename + os.extsep + "db", "rb")
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f.close()
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# guarantee we can actually open the file using dbm
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# kind of overkill, but since we are dealing with emulations
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# it seems like a prudent step
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if dbm is not None:
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d = dbm.open(filename)
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d.close()
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return "dbm"
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except (IOError, _dbmerror):
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pass
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# Check for dumbdbm next -- this has a .dir and and a .dat file
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try:
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# First check for presence of files
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os.stat(filename + os.extsep + "dat")
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size = os.stat(filename + os.extsep + "dir").st_size
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# dumbdbm files with no keys are empty
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if size == 0:
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return "dumbdbm"
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f = open(filename + os.extsep + "dir", "rb")
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try:
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if f.read(1) in ["'", '"']:
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return "dumbdbm"
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finally:
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f.close()
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except (OSError, IOError):
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pass
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# See if the file exists, return None if not
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try:
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f = open(filename, "rb")
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except IOError:
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return None
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# Read the start of the file -- the magic number
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s16 = f.read(16)
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f.close()
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s = s16[0:4]
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# Return "" if not at least 4 bytes
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if len(s) != 4:
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return ""
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# Convert to 4-byte int in native byte order -- return "" if impossible
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try:
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(magic,) = struct.unpack("=l", s)
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except struct.error:
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return ""
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# Check for GNU dbm
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if magic == 0x13579ace:
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return "gdbm"
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# Check for old Berkeley db hash file format v2
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if magic in (0x00061561, 0x61150600):
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return "bsddb185"
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# Later versions of Berkeley db hash file have a 12-byte pad in
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# front of the file type
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try:
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(magic,) = struct.unpack("=l", s16[-4:])
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except struct.error:
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return ""
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# Check for BSD hash
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if magic in (0x00061561, 0x61150600):
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return "dbhash"
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# Unknown
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return ""
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