1 2 """ 3 File-like objects that read from or write to a bsddb record. 4 5 This implements (nearly) all stdio methods. 6 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) 18 19 Notes: 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 27 From: 28 Itamar Shtull-Trauring <itamar (at] maxnm.com> 29 """ 30 31 import errno 32 import string 33 34 class 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 147 148 def _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() 187 188 if __name__ == '__main__': 189 _test() 190 """ 191
