3
File-like objects that read from or write to a bsddb record.
5
This implements (nearly) all stdio methods.
7
f = DBRecIO(db, key, txn=None)
8
f.close() # explicitly release resources held
9
flag = f.isatty() # always false
10
pos = f.tell() # get current position
11
f.seek(pos) # set current position
12
f.seek(pos, mode) # mode 0: absolute; 1: relative; 2: relative to EOF
13
buf = f.read() # read until EOF
14
buf = f.read(n) # read up to n bytes
15
f.truncate([size]) # truncate file at to at most size (default: current pos)
16
f.write(buf) # write at current position
17
f.writelines(list) # for line in list: f.write(line)
20
- fileno() is left unimplemented so that code which uses it triggers
22
- There's a simple test set (see end of this file) - not yet updated
24
- readline() is not implemented yet.
28
Itamar Shtull-Trauring <itamar@maxnm.com>
35
def __init__(self, db, key, txn=None):
51
raise ValueError, "I/O operation on closed file"
54
def seek(self, pos, mode = 0):
56
raise ValueError, "I/O operation on closed file"
61
self.pos = max(0, pos)
65
raise ValueError, "I/O operation on closed file"
68
def read(self, n = -1):
70
raise ValueError, "I/O operation on closed file"
74
newpos = min(self.pos+n, self.len)
76
dlen = newpos - self.pos
78
r = self.db.get(self.key, txn=self.txn, dlen=dlen, doff=self.pos)
83
def readline(self, length=None):
85
raise ValueError, "I/O operation on closed file"
87
self.buf = self.buf + string.joinfields(self.buflist, '')
89
i = string.find(self.buf, '\n', self.pos)
94
if length is not None:
95
if self.pos + length < newpos:
96
newpos = self.pos + length
97
r = self.buf[self.pos:newpos]
101
def readlines(self, sizehint = 0):
104
line = self.readline()
108
if 0 < sizehint <= total:
110
line = self.readline()
114
def truncate(self, size=None):
116
raise ValueError, "I/O operation on closed file"
120
raise IOError(errno.EINVAL,
121
"Negative size not allowed")
122
elif size < self.pos:
124
self.db.put(self.key, "", txn=self.txn, dlen=self.len-size, doff=size)
128
raise ValueError, "I/O operation on closed file"
130
if self.pos > self.len:
131
self.buflist.append('\0'*(self.pos - self.len))
133
newpos = self.pos + len(s)
134
self.db.put(self.key, s, txn=self.txn, dlen=len(s), doff=self.pos)
137
def writelines(self, list):
138
self.write(string.joinfields(list, ''))
142
raise ValueError, "I/O operation on closed file"
146
# A little test suite
154
lines = open(file, 'r').readlines()
155
text = open(file, 'r').read()
157
for line in lines[:-2]:
159
f.writelines(lines[-2:])
160
if f.getvalue() != text:
161
raise RuntimeError, 'write failed'
163
print 'File length =', length
164
f.seek(len(lines[0]))
167
print 'First line =', repr(f.readline())
170
print 'Second line =', repr(line)
171
f.seek(-len(line), 1)
172
line2 = f.read(len(line))
174
raise RuntimeError, 'bad result after seek back'
175
f.seek(len(line2), 1)
178
f.seek(f.tell() - len(line))
181
raise RuntimeError, 'bad result after seek back from EOF'
182
print 'Read', len(list), 'more lines'
183
print 'File length =', f.tell()
184
if f.tell() != length:
185
raise RuntimeError, 'bad length'
188
if __name__ == '__main__':