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191 lines
5.2 KiB
191 lines
5.2 KiB
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"""
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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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