Guido van Rossum | 8d12a1b | 1996-07-30 16:30:15 +0000 | [diff] [blame] | 1 | """Guess which db package to use to open a db file.""" |
| 2 | |
Guido van Rossum | d74fb6b | 2001-03-02 06:43:49 +0000 | [diff] [blame] | 3 | import os |
| 4 | |
| 5 | if os.sep==".": |
| 6 | endsep = "/" |
| 7 | else: |
| 8 | endsep = "." |
Tim Peters | 30edd23 | 2001-03-16 08:29:48 +0000 | [diff] [blame] | 9 | |
Guido van Rossum | 8d12a1b | 1996-07-30 16:30:15 +0000 | [diff] [blame] | 10 | def whichdb(filename): |
| 11 | """Guess which db package to use to open a db file. |
| 12 | |
| 13 | Return values: |
| 14 | |
| 15 | - None if the database file can't be read; |
| 16 | - empty string if the file can be read but can't be recognized |
| 17 | - the module name (e.g. "dbm" or "gdbm") if recognized. |
| 18 | |
| 19 | Importing the given module may still fail, and opening the |
| 20 | database using that module may still fail. |
| 21 | """ |
| 22 | |
Skip Montanaro | 58eadba | 2001-03-01 04:13:51 +0000 | [diff] [blame] | 23 | import struct |
| 24 | |
Guido van Rossum | 8d12a1b | 1996-07-30 16:30:15 +0000 | [diff] [blame] | 25 | # Check for dbm first -- this has a .pag and a .dir file |
| 26 | try: |
Guido van Rossum | d74fb6b | 2001-03-02 06:43:49 +0000 | [diff] [blame] | 27 | f = open(filename + endsep + "pag", "rb") |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 28 | f.close() |
Guido van Rossum | d74fb6b | 2001-03-02 06:43:49 +0000 | [diff] [blame] | 29 | f = open(filename + endsep + "dir", "rb") |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 30 | f.close() |
| 31 | return "dbm" |
Guido van Rossum | 8d12a1b | 1996-07-30 16:30:15 +0000 | [diff] [blame] | 32 | except IOError: |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 33 | pass |
Guido van Rossum | 8d12a1b | 1996-07-30 16:30:15 +0000 | [diff] [blame] | 34 | |
Moshe Zadka | 7a4409c | 2000-07-29 05:31:40 +0000 | [diff] [blame] | 35 | # Check for dumbdbm next -- this has a .dir and and a .dat file |
Thomas Wouters | 3027b15 | 2000-08-04 08:46:59 +0000 | [diff] [blame] | 36 | try: |
Guido van Rossum | d74fb6b | 2001-03-02 06:43:49 +0000 | [diff] [blame] | 37 | f = open(filename + endsep + "dat", "rb") |
Moshe Zadka | 7a4409c | 2000-07-29 05:31:40 +0000 | [diff] [blame] | 38 | f.close() |
Guido van Rossum | d74fb6b | 2001-03-02 06:43:49 +0000 | [diff] [blame] | 39 | f = open(filename + endsep + "dir", "rb") |
Moshe Zadka | 7a4409c | 2000-07-29 05:31:40 +0000 | [diff] [blame] | 40 | try: |
| 41 | if f.read(1) in ["'", '"']: |
| 42 | return "dumbdbm" |
| 43 | finally: |
| 44 | f.close() |
| 45 | except IOError: |
| 46 | pass |
| 47 | |
Guido van Rossum | 8d12a1b | 1996-07-30 16:30:15 +0000 | [diff] [blame] | 48 | # See if the file exists, return None if not |
| 49 | try: |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 50 | f = open(filename, "rb") |
Guido van Rossum | 8d12a1b | 1996-07-30 16:30:15 +0000 | [diff] [blame] | 51 | except IOError: |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 52 | return None |
Guido van Rossum | 8d12a1b | 1996-07-30 16:30:15 +0000 | [diff] [blame] | 53 | |
Guido van Rossum | cf09a39 | 1999-06-08 13:13:16 +0000 | [diff] [blame] | 54 | # Read the start of the file -- the magic number |
| 55 | s16 = f.read(16) |
Guido van Rossum | 8d12a1b | 1996-07-30 16:30:15 +0000 | [diff] [blame] | 56 | f.close() |
Guido van Rossum | cf09a39 | 1999-06-08 13:13:16 +0000 | [diff] [blame] | 57 | s = s16[0:4] |
Guido van Rossum | 8d12a1b | 1996-07-30 16:30:15 +0000 | [diff] [blame] | 58 | |
| 59 | # Return "" if not at least 4 bytes |
| 60 | if len(s) != 4: |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 61 | return "" |
Guido van Rossum | 8d12a1b | 1996-07-30 16:30:15 +0000 | [diff] [blame] | 62 | |
| 63 | # Convert to 4-byte int in native byte order -- return "" if impossible |
| 64 | try: |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 65 | (magic,) = struct.unpack("=l", s) |
Guido van Rossum | 8d12a1b | 1996-07-30 16:30:15 +0000 | [diff] [blame] | 66 | except struct.error: |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 67 | return "" |
Guido van Rossum | 8d12a1b | 1996-07-30 16:30:15 +0000 | [diff] [blame] | 68 | |
| 69 | # Check for GNU dbm |
| 70 | if magic == 0x13579ace: |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 71 | return "gdbm" |
Guido van Rossum | 8d12a1b | 1996-07-30 16:30:15 +0000 | [diff] [blame] | 72 | |
| 73 | # Check for BSD hash |
Guido van Rossum | b86ba12 | 1998-04-28 15:41:03 +0000 | [diff] [blame] | 74 | if magic in (0x00061561, 0x61150600): |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 75 | return "dbhash" |
Guido van Rossum | 8d12a1b | 1996-07-30 16:30:15 +0000 | [diff] [blame] | 76 | |
Guido van Rossum | cf09a39 | 1999-06-08 13:13:16 +0000 | [diff] [blame] | 77 | # BSD hash v2 has a 12-byte NULL pad in front of the file type |
| 78 | try: |
Fred Drake | 13a2c27 | 2000-02-10 17:17:14 +0000 | [diff] [blame] | 79 | (magic,) = struct.unpack("=l", s16[-4:]) |
Guido van Rossum | cf09a39 | 1999-06-08 13:13:16 +0000 | [diff] [blame] | 80 | except struct.error: |
| 81 | return "" |
| 82 | |
| 83 | # Check for BSD hash |
| 84 | if magic in (0x00061561, 0x61150600): |
| 85 | return "dbhash" |
| 86 | |
Guido van Rossum | 8d12a1b | 1996-07-30 16:30:15 +0000 | [diff] [blame] | 87 | # Unknown |
| 88 | return "" |