1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
|
#! /usr/bin/env python
"""
Dan Bernstein's CDB implemented in Python
see http://cr.yp.to/cdb.html
"""
from __future__ import generators
import os
import struct
import mmap
def uint32_unpack(buf):
return struct.unpack('<L', buf)[0]
def uint32_pack(n):
return struct.pack('<L', n)
CDB_HASHSTART = 5381
def cdb_hash(buf):
h = CDB_HASHSTART
for c in buf:
h = (h + (h << 5)) & 0xffffffffL
h ^= ord(c)
return h
class Cdb(object):
def __init__(self, fp):
self.fp = fp
fd = fp.fileno()
self.size = os.fstat(fd).st_size
self.map = mmap.mmap(fd, self.size, access=mmap.ACCESS_READ)
self.eod = uint32_unpack(self.map[:4])
self.findstart()
self.loop = 0 # number of hash slots searched under this key
# initialized if loop is nonzero
self.khash = 0
self.hpos = 0
self.hslots = 0
# initialized if findnext() returns 1
self.dpos = 0
self.dlen = 0
def close(self):
self.map.close()
def __iter__(self, fn=None):
len = 2048
while len < self.eod:
klen, vlen = struct.unpack("<LL", self.map[len:len+8])
len += 8
key = self.map[len:len+klen]
len += klen
val = self.map[len:len+vlen]
len += vlen
if fn:
yield fn(key, val)
else:
yield (key, val)
def iteritems(self):
return self.__iter__()
def iterkeys(self):
return self.__iter__(lambda k,v: k)
def itervalues(self):
return self.__iter__(lambda k,v: v)
def items(self):
ret = []
for i in self.iteritems():
ret.append(i)
return ret
def keys(self):
ret = []
for i in self.iterkeys():
ret.append(i)
return ret
def values(self):
ret = []
for i in self.itervalues():
ret.append(i)
return ret
def findstart(self):
self.loop = 0
def read(self, n, pos):
# XXX add code for platforms without mmap
return self.map[pos:pos+n]
def match(self, key, pos):
if key == self.read(len(key), pos):
return 1
else:
return 0
def findnext(self, key):
if not self.loop:
u = cdb_hash(key)
buf = self.read(8, u << 3 & 2047)
self.hslots = uint32_unpack(buf[4:])
if not self.hslots:
raise KeyError
self.hpos = uint32_unpack(buf[:4])
self.khash = u
u >>= 8
u %= self.hslots
u <<= 3
self.kpos = self.hpos + u
while self.loop < self.hslots:
buf = self.read(8, self.kpos)
pos = uint32_unpack(buf[4:])
if not pos:
raise KeyError
self.loop += 1
self.kpos += 8
if self.kpos == self.hpos + (self.hslots << 3):
self.kpos = self.hpos
u = uint32_unpack(buf[:4])
if u == self.khash:
buf = self.read(8, pos)
u = uint32_unpack(buf[:4])
if u == len(key):
if self.match(key, pos + 8):
dlen = uint32_unpack(buf[4:])
dpos = pos + 8 + len(key)
return self.read(dlen, dpos)
raise KeyError
def __getitem__(self, key):
self.findstart()
return self.findnext(key)
def get(self, key, default=None):
self.findstart()
try:
return self.findnext(key)
except KeyError:
return default
def cdb_dump(infile):
"""dump a database in djb's cdbdump format"""
db = Cdb(infile)
for key,value in db.iteritems():
print "+%d,%d:%s->%s" % (len(key), len(value), key, value)
print
def cdb_make(outfile, items):
pos = 2048
tables = {} # { h & 255 : [(h, p)] }
# write keys and data
outfile.seek(pos)
for key, value in items:
outfile.write(uint32_pack(len(key)) + uint32_pack(len(value)))
h = cdb_hash(key)
outfile.write(key)
outfile.write(value)
tables.setdefault(h & 255, []).append((h, pos))
pos += 8 + len(key) + len(value)
final = ''
# write hash tables
for i in range(256):
entries = tables.get(i, [])
nslots = 2*len(entries)
final += uint32_pack(pos) + uint32_pack(nslots)
null = (0, 0)
table = [null] * nslots
for h, p in entries:
n = (h >> 8) % nslots
while table[n] is not null:
n = (n + 1) % nslots
table[n] = (h, p)
for h, p in table:
outfile.write(uint32_pack(h) + uint32_pack(p))
pos += 8
# write header (pointers to tables and their lengths)
outfile.flush()
outfile.seek(0)
outfile.write(final)
class CdbMake(object):
def __init__(self, outfile):
self.pos = 2048
self.outfile = outfile
self.outfile.seek(self.pos)
self.tables = {}
def add(self, key, value):
outfile = self.outfile
outfile.write(uint32_pack(len(key)) + uint32_pack(len(value)))
h = cdb_hash(key)
outfile.write(key)
outfile.write(value)
self.tables.setdefault(h & 255, []).append((h, self.pos))
self.pos += 8 + len(key) + len(value)
def finish(self):
final = ''
tables = self.tables
pos = self.pos
outfile = self.outfile
# write hash tables
for i in range(256):
entries = tables.get(i, [])
nslots = 2*len(entries)
final += uint32_pack(pos) + uint32_pack(nslots)
null = (0, 0)
table = [null] * nslots
for h, p in entries:
n = (h >> 8) % nslots
while table[n] is not null:
n = (n + 1) % nslots
table[n] = (h, p)
for h, p in table:
outfile.write(uint32_pack(h) + uint32_pack(p))
pos += 8
# write header (pointers to tables and their lengths)
outfile.flush()
outfile.seek(0)
outfile.write(final)
def test():
#db = Cdb(open("t"))
#print db['one']
#print db['two']
#print db['foo']
#print db['us']
#print db.get('ec')
#print db.get('notthere')
db = open('test.cdb', 'wb')
cdb_make(db,
[('one', 'Hello'),
('two', 'Goodbye'),
('foo', 'Bar'),
('us', 'United States'),
])
db.close()
db = Cdb(open("test.cdb", 'rb'))
print db['one']
print db['two']
print db['foo']
print db['us']
print db.get('ec')
print db.get('notthere')
if __name__ == '__main__':
test()
|
