[0] Fix | Delete

"""

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File-like objects that read from or write to a bsddb record.

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This implements (nearly) all stdio methods.

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f = DBRecIO(db, key, txn=None)

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f.close() # explicitly release resources held

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flag = f.isatty() # always false

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pos = f.tell() # get current position

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f.seek(pos) # set current position

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f.seek(pos, mode) # mode 0: absolute; 1: relative; 2: relative to EOF

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buf = f.read() # read until EOF

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buf = f.read(n) # read up to n bytes

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f.truncate([size]) # truncate file at to at most size (default: current pos)

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f.write(buf) # write at current position

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f.writelines(list) # for line in list: f.write(line)

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Notes:

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- fileno() is left unimplemented so that code which uses it triggers

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an exception early.

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- There's a simple test set (see end of this file) - not yet updated

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for DBRecIO.

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- readline() is not implemented yet.

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From:

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Itamar Shtull-Trauring <itamar@maxnm.com>

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"""

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import errno

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import string

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class DBRecIO:

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def __init__(self, db, key, txn=None):

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self.db = db

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self.key = key

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self.txn = txn

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self.len = None

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self.pos = 0

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self.closed = 0

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self.softspace = 0

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def close(self):

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if not self.closed:

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self.closed = 1

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del self.db, self.txn

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def isatty(self):

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if self.closed:

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raise ValueError, "I/O operation on closed file"

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return 0

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def seek(self, pos, mode = 0):

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if self.closed:

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raise ValueError, "I/O operation on closed file"

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if mode == 1:

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pos = pos + self.pos

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elif mode == 2:

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pos = pos + self.len

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self.pos = max(0, pos)

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def tell(self):

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if self.closed:

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raise ValueError, "I/O operation on closed file"

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return self.pos

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def read(self, n = -1):

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if self.closed:

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raise ValueError, "I/O operation on closed file"

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if n < 0:

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newpos = self.len

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else:

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newpos = min(self.pos+n, self.len)

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dlen = newpos - self.pos

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r = self.db.get(self.key, txn=self.txn, dlen=dlen, doff=self.pos)

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self.pos = newpos

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return r

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__fixme = """

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def readline(self, length=None):

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if self.closed:

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raise ValueError, "I/O operation on closed file"

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if self.buflist:

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self.buf = self.buf + string.joinfields(self.buflist, '')

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self.buflist = []

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i = string.find(self.buf, '\n', self.pos)

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if i < 0:

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newpos = self.len

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else:

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newpos = i+1

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if length is not None:

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if self.pos + length < newpos:

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newpos = self.pos + length

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r = self.buf[self.pos:newpos]

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self.pos = newpos

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return r

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def readlines(self, sizehint = 0):

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total = 0

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lines = []

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line = self.readline()

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while line:

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lines.append(line)

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total += len(line)

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if 0 < sizehint <= total:

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break

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line = self.readline()

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return lines

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"""

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def truncate(self, size=None):

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if self.closed:

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raise ValueError, "I/O operation on closed file"

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if size is None:

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size = self.pos

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elif size < 0:

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raise IOError(errno.EINVAL,

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"Negative size not allowed")

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elif size < self.pos:

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self.pos = size

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self.db.put(self.key, "", txn=self.txn, dlen=self.len-size, doff=size)

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def write(self, s):

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if self.closed:

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raise ValueError, "I/O operation on closed file"

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if not s: return

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if self.pos > self.len:

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self.buflist.append('\0'*(self.pos - self.len))

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self.len = self.pos

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newpos = self.pos + len(s)

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self.db.put(self.key, s, txn=self.txn, dlen=len(s), doff=self.pos)

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self.pos = newpos

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def writelines(self, list):

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self.write(string.joinfields(list, ''))

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def flush(self):

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if self.closed:

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raise ValueError, "I/O operation on closed file"

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"""

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# A little test suite

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def _test():

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import sys

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if sys.argv[1:]:

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file = sys.argv[1]

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else:

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file = '/etc/passwd'

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lines = open(file, 'r').readlines()

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text = open(file, 'r').read()

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f = StringIO()

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for line in lines[:-2]:

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f.write(line)

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f.writelines(lines[-2:])

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if f.getvalue() != text:

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raise RuntimeError, 'write failed'

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length = f.tell()

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print 'File length =', length

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f.seek(len(lines[0]))

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f.write(lines[1])

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f.seek(0)

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print 'First line =', repr(f.readline())

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here = f.tell()

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line = f.readline()

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print 'Second line =', repr(line)

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f.seek(-len(line), 1)

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line2 = f.read(len(line))

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if line != line2:

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raise RuntimeError, 'bad result after seek back'

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f.seek(len(line2), 1)

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list = f.readlines()

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line = list[-1]

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f.seek(f.tell() - len(line))

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line2 = f.read()

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if line != line2:

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raise RuntimeError, 'bad result after seek back from EOF'

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print 'Read', len(list), 'more lines'

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print 'File length =', f.tell()

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if f.tell() != length:

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raise RuntimeError, 'bad length'

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f.close()

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if __name__ == '__main__':

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_test()

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"""

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