Mercurial > cpython-lru_cache-weakref
annotate Lib/dumbdbm.py @ 4566:6403c94de50d legacy-trunk
Added safeguard against failure in __del__.
| author | Guido van Rossum <guido@python.org> |
|---|---|
| date | Wed, 27 Nov 1996 19:39:58 +0000 |
| parents | 985134375672 |
| children | cde9b2e64c00 |
| rev | line source |
|---|---|
| 2952 | 1 """A dumb and slow but simple dbm clone. |
| 2 | |
| 3 For database spam, spam.dir contains the index (a text file), | |
| 4 spam.bak *may* contain a backup of the index (also a text file), | |
| 5 while spam.dat contains the data (a binary file). | |
| 6 | |
| 7 XXX TO DO: | |
| 8 | |
| 9 - seems to contain a bug when updating... | |
| 10 | |
| 11 - reclaim free space (currently, space once occupied by deleted or expanded | |
| 12 items is never reused) | |
| 13 | |
| 14 - support concurrent access (currently, if two processes take turns making | |
| 15 updates, they can mess up the index) | |
| 16 | |
| 17 - support efficient access to large databases (currently, the whole index | |
| 18 is read when the database is opened, and some updates rewrite the whole index) | |
| 19 | |
| 20 - support opening for read-only (flag = 'm') | |
| 21 | |
| 22 """ | |
| 23 | |
| 24 _os = __import__('os') | |
| 25 import __builtin__ | |
| 26 | |
| 27 _open = __builtin__.open | |
| 28 | |
| 29 _BLOCKSIZE = 512 | |
| 30 | |
|
3631
985134375672
export error == IOError
Guido van Rossum <guido@python.org>
parents:
3358
diff
changeset
|
31 error = IOError # For anydbm |
|
985134375672
export error == IOError
Guido van Rossum <guido@python.org>
parents:
3358
diff
changeset
|
32 |
| 2952 | 33 class _Database: |
| 34 | |
| 35 def __init__(self, file): | |
| 36 self._dirfile = file + '.dir' | |
| 37 self._datfile = file + '.dat' | |
| 38 self._bakfile = file + '.bak' | |
| 39 # Mod by Jack: create data file if needed | |
| 40 try: | |
| 41 f = _open(self._datfile, 'r') | |
| 42 except IOError: | |
| 43 f = _open(self._datfile, 'w') | |
| 44 f.close() | |
| 45 self._update() | |
| 46 | |
| 47 def _update(self): | |
| 48 self._index = {} | |
| 49 try: | |
| 50 f = _open(self._dirfile) | |
| 51 except IOError: | |
| 52 pass | |
| 53 else: | |
| 54 while 1: | |
| 55 line = f.readline() | |
| 56 if not line: break | |
| 57 key, (pos, siz) = eval(line) | |
| 58 self._index[key] = (pos, siz) | |
| 59 f.close() | |
| 60 | |
| 61 def _commit(self): | |
| 62 try: _os.unlink(self._bakfile) | |
| 63 except _os.error: pass | |
| 64 try: _os.rename(self._dirfile, self._bakfile) | |
| 65 except _os.error: pass | |
| 66 f = _open(self._dirfile, 'w') | |
| 67 for key, (pos, siz) in self._index.items(): | |
| 68 f.write("%s, (%s, %s)\n" % (`key`, `pos`, `siz`)) | |
| 69 f.close() | |
| 70 | |
| 71 def __getitem__(self, key): | |
| 72 pos, siz = self._index[key] # may raise KeyError | |
| 73 f = _open(self._datfile, 'rb') | |
| 74 f.seek(pos) | |
| 75 dat = f.read(siz) | |
| 76 f.close() | |
| 77 return dat | |
| 78 | |
| 79 def _addval(self, val): | |
| 80 f = _open(self._datfile, 'rb+') | |
| 81 f.seek(0, 2) | |
| 82 pos = f.tell() | |
| 83 ## Does not work under MW compiler | |
| 84 ## pos = ((pos + _BLOCKSIZE - 1) / _BLOCKSIZE) * _BLOCKSIZE | |
| 85 ## f.seek(pos) | |
| 86 npos = ((pos + _BLOCKSIZE - 1) / _BLOCKSIZE) * _BLOCKSIZE | |
| 87 f.write('\0'*(npos-pos)) | |
| 88 pos = npos | |
| 89 | |
| 90 f.write(val) | |
| 91 f.close() | |
| 92 return (pos, len(val)) | |
| 93 | |
| 94 def _setval(self, pos, val): | |
| 95 f = _open(self._datfile, 'rb+') | |
| 96 f.seek(pos) | |
| 97 f.write(val) | |
| 98 f.close() | |
|
3358
21d89698329c
fix typo in _setval() return value
Guido van Rossum <guido@python.org>
parents:
2952
diff
changeset
|
99 return (pos, len(val)) |
| 2952 | 100 |
| 101 def _addkey(self, key, (pos, siz)): | |
| 102 self._index[key] = (pos, siz) | |
| 103 f = _open(self._dirfile, 'a') | |
| 104 f.write("%s, (%s, %s)\n" % (`key`, `pos`, `siz`)) | |
| 105 f.close() | |
| 106 | |
| 107 def __setitem__(self, key, val): | |
| 108 if not type(key) == type('') == type(val): | |
| 109 raise TypeError, "keys and values must be strings" | |
| 110 if not self._index.has_key(key): | |
| 111 (pos, siz) = self._addval(val) | |
| 112 self._addkey(key, (pos, siz)) | |
| 113 else: | |
| 114 pos, siz = self._index[key] | |
| 115 oldblocks = (siz + _BLOCKSIZE - 1) / _BLOCKSIZE | |
| 116 newblocks = (len(val) + _BLOCKSIZE - 1) / _BLOCKSIZE | |
| 117 if newblocks <= oldblocks: | |
| 118 pos, siz = self._setval(pos, val) | |
| 119 self._index[key] = pos, siz | |
| 120 else: | |
| 121 pos, siz = self._addval(val) | |
| 122 self._index[key] = pos, siz | |
| 123 self._addkey(key, (pos, siz)) | |
| 124 | |
| 125 def __delitem__(self, key): | |
| 126 del self._index[key] | |
| 127 self._commit() | |
| 128 | |
| 129 def keys(self): | |
| 130 return self._index.keys() | |
| 131 | |
| 132 def has_key(self, key): | |
| 133 return self._index.has_key(key) | |
| 134 | |
| 135 def __len__(self): | |
| 136 return len(self._index) | |
| 137 | |
| 138 def close(self): | |
| 139 self._index = None | |
| 140 self._datfile = self._dirfile = self._bakfile = None | |
| 141 | |
| 142 | |
| 143 def open(file, flag = None, mode = None): | |
| 144 # flag, mode arguments are currently ignored | |
| 145 return _Database(file) |