Initial revision
diff --git a/Lib/dumbdbm.py b/Lib/dumbdbm.py
new file mode 100644
index 0000000..f0be061
--- /dev/null
+++ b/Lib/dumbdbm.py
@@ -0,0 +1,143 @@
+"""A dumb and slow but simple dbm clone.
+
+For database spam, spam.dir contains the index (a text file),
+spam.bak *may* contain a backup of the index (also a text file),
+while spam.dat contains the data (a binary file).
+
+XXX TO DO:
+
+- seems to contain a bug when updating...
+
+- reclaim free space (currently, space once occupied by deleted or expanded
+items is never reused)
+
+- support concurrent access (currently, if two processes take turns making
+updates, they can mess up the index)
+
+- support efficient access to large databases (currently, the whole index
+is read when the database is opened, and some updates rewrite the whole index)
+
+- support opening for read-only (flag = 'm')
+
+"""
+
+_os = __import__('os')
+import __builtin__
+
+_open = __builtin__.open
+
+_BLOCKSIZE = 512
+
+class _Database:
+
+ def __init__(self, file):
+ self._dirfile = file + '.dir'
+ self._datfile = file + '.dat'
+ self._bakfile = file + '.bak'
+ # Mod by Jack: create data file if needed
+ try:
+ f = _open(self._datfile, 'r')
+ except IOError:
+ f = _open(self._datfile, 'w')
+ f.close()
+ self._update()
+
+ def _update(self):
+ self._index = {}
+ try:
+ f = _open(self._dirfile)
+ except IOError:
+ pass
+ else:
+ while 1:
+ line = f.readline()
+ if not line: break
+ key, (pos, siz) = eval(line)
+ self._index[key] = (pos, siz)
+ f.close()
+
+ def _commit(self):
+ try: _os.unlink(self._bakfile)
+ except _os.error: pass
+ try: _os.rename(self._dirfile, self._bakfile)
+ except _os.error: pass
+ f = _open(self._dirfile, 'w')
+ for key, (pos, siz) in self._index.items():
+ f.write("%s, (%s, %s)\n" % (`key`, `pos`, `siz`))
+ f.close()
+
+ def __getitem__(self, key):
+ pos, siz = self._index[key] # may raise KeyError
+ f = _open(self._datfile, 'rb')
+ f.seek(pos)
+ dat = f.read(siz)
+ f.close()
+ return dat
+
+ def _addval(self, val):
+ f = _open(self._datfile, 'rb+')
+ f.seek(0, 2)
+ pos = f.tell()
+## Does not work under MW compiler
+## pos = ((pos + _BLOCKSIZE - 1) / _BLOCKSIZE) * _BLOCKSIZE
+## f.seek(pos)
+ npos = ((pos + _BLOCKSIZE - 1) / _BLOCKSIZE) * _BLOCKSIZE
+ f.write('\0'*(npos-pos))
+ pos = npos
+
+ f.write(val)
+ f.close()
+ return (pos, len(val))
+
+ def _setval(self, pos, val):
+ f = _open(self._datfile, 'rb+')
+ f.seek(pos)
+ f.write(val)
+ f.close()
+ return pos, (val)
+
+ def _addkey(self, key, (pos, siz)):
+ self._index[key] = (pos, siz)
+ f = _open(self._dirfile, 'a')
+ f.write("%s, (%s, %s)\n" % (`key`, `pos`, `siz`))
+ f.close()
+
+ def __setitem__(self, key, val):
+ if not type(key) == type('') == type(val):
+ raise TypeError, "keys and values must be strings"
+ if not self._index.has_key(key):
+ (pos, siz) = self._addval(val)
+ self._addkey(key, (pos, siz))
+ else:
+ pos, siz = self._index[key]
+ oldblocks = (siz + _BLOCKSIZE - 1) / _BLOCKSIZE
+ newblocks = (len(val) + _BLOCKSIZE - 1) / _BLOCKSIZE
+ if newblocks <= oldblocks:
+ pos, siz = self._setval(pos, val)
+ self._index[key] = pos, siz
+ else:
+ pos, siz = self._addval(val)
+ self._index[key] = pos, siz
+ self._addkey(key, (pos, siz))
+
+ def __delitem__(self, key):
+ del self._index[key]
+ self._commit()
+
+ def keys(self):
+ return self._index.keys()
+
+ def has_key(self, key):
+ return self._index.has_key(key)
+
+ def __len__(self):
+ return len(self._index)
+
+ def close(self):
+ self._index = None
+ self._datfile = self._dirfile = self._bakfile = None
+
+
+def open(file, flag = None, mode = None):
+ # flag, mode arguments are currently ignored
+ return _Database(file)