1
2"""
3File-like objects that read from or write to a bsddb record.
4
5This implements (nearly) all stdio methods.
6
7f = DBRecIO(db, key, txn=None)
8f.close()           # explicitly release resources held
9flag = f.isatty()   # always false
10pos = f.tell()      # get current position
11f.seek(pos)         # set current position
12f.seek(pos, mode)   # mode 0: absolute; 1: relative; 2: relative to EOF
13buf = f.read()      # read until EOF
14buf = f.read(n)     # read up to n bytes
15f.truncate([size])  # truncate file at to at most size (default: current pos)
16f.write(buf)        # write at current position
17f.writelines(list)  # for line in list: f.write(line)
18
19Notes:
20- fileno() is left unimplemented so that code which uses it triggers
21  an exception early.
22- There's a simple test set (see end of this file) - not yet updated
23  for DBRecIO.
24- readline() is not implemented yet.
25
26
27From:
28    Itamar Shtull-Trauring <itamar@maxnm.com>
29"""
30
31import errno
32import string
33
34class DBRecIO:
35    def __init__(self, db, key, txn=None):
36        self.db = db
37        self.key = key
38        self.txn = txn
39        self.len = None
40        self.pos = 0
41        self.closed = 0
42        self.softspace = 0
43
44    def close(self):
45        if not self.closed:
46            self.closed = 1
47            del self.db, self.txn
48
49    def isatty(self):
50        if self.closed:
51            raise ValueError, "I/O operation on closed file"
52        return 0
53
54    def seek(self, pos, mode = 0):
55        if self.closed:
56            raise ValueError, "I/O operation on closed file"
57        if mode == 1:
58            pos = pos + self.pos
59        elif mode == 2:
60            pos = pos + self.len
61        self.pos = max(0, pos)
62
63    def tell(self):
64        if self.closed:
65            raise ValueError, "I/O operation on closed file"
66        return self.pos
67
68    def read(self, n = -1):
69        if self.closed:
70            raise ValueError, "I/O operation on closed file"
71        if n < 0:
72            newpos = self.len
73        else:
74            newpos = min(self.pos+n, self.len)
75
76        dlen = newpos - self.pos
77
78        r = self.db.get(self.key, txn=self.txn, dlen=dlen, doff=self.pos)
79        self.pos = newpos
80        return r
81
82    __fixme = """
83    def readline(self, length=None):
84        if self.closed:
85            raise ValueError, "I/O operation on closed file"
86        if self.buflist:
87            self.buf = self.buf + string.joinfields(self.buflist, '')
88            self.buflist = []
89        i = string.find(self.buf, '\n', self.pos)
90        if i < 0:
91            newpos = self.len
92        else:
93            newpos = i+1
94        if length is not None:
95            if self.pos + length < newpos:
96                newpos = self.pos + length
97        r = self.buf[self.pos:newpos]
98        self.pos = newpos
99        return r
100
101    def readlines(self, sizehint = 0):
102        total = 0
103        lines = []
104        line = self.readline()
105        while line:
106            lines.append(line)
107            total += len(line)
108            if 0 < sizehint <= total:
109                break
110            line = self.readline()
111        return lines
112    """
113
114    def truncate(self, size=None):
115        if self.closed:
116            raise ValueError, "I/O operation on closed file"
117        if size is None:
118            size = self.pos
119        elif size < 0:
120            raise IOError(errno.EINVAL,
121                                      "Negative size not allowed")
122        elif size < self.pos:
123            self.pos = size
124        self.db.put(self.key, "", txn=self.txn, dlen=self.len-size, doff=size)
125
126    def write(self, s):
127        if self.closed:
128            raise ValueError, "I/O operation on closed file"
129        if not s: return
130        if self.pos > self.len:
131            self.buflist.append('\0'*(self.pos - self.len))
132            self.len = self.pos
133        newpos = self.pos + len(s)
134        self.db.put(self.key, s, txn=self.txn, dlen=len(s), doff=self.pos)
135        self.pos = newpos
136
137    def writelines(self, list):
138        self.write(string.joinfields(list, ''))
139
140    def flush(self):
141        if self.closed:
142            raise ValueError, "I/O operation on closed file"
143
144
145"""
146# A little test suite
147
148def _test():
149    import sys
150    if sys.argv[1:]:
151        file = sys.argv[1]
152    else:
153        file = '/etc/passwd'
154    lines = open(file, 'r').readlines()
155    text = open(file, 'r').read()
156    f = StringIO()
157    for line in lines[:-2]:
158        f.write(line)
159    f.writelines(lines[-2:])
160    if f.getvalue() != text:
161        raise RuntimeError, 'write failed'
162    length = f.tell()
163    print 'File length =', length
164    f.seek(len(lines[0]))
165    f.write(lines[1])
166    f.seek(0)
167    print 'First line =', repr(f.readline())
168    here = f.tell()
169    line = f.readline()
170    print 'Second line =', repr(line)
171    f.seek(-len(line), 1)
172    line2 = f.read(len(line))
173    if line != line2:
174        raise RuntimeError, 'bad result after seek back'
175    f.seek(len(line2), 1)
176    list = f.readlines()
177    line = list[-1]
178    f.seek(f.tell() - len(line))
179    line2 = f.read()
180    if line != line2:
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'
186    f.close()
187
188if __name__ == '__main__':
189    _test()
190"""
191