0001 0002 """ 0003 File-like objects that read from or write to a bsddb record. 0004 0005 This implements (nearly) all stdio methods. 0006 0007 f = DBRecIO(db, key, txn=None) 0008 f.close() # explicitly release resources held 0009 flag = f.isatty() # always false 0010 pos = f.tell() # get current position 0011 f.seek(pos) # set current position 0012 f.seek(pos, mode) # mode 0: absolute; 1: relative; 2: relative to EOF 0013 buf = f.read() # read until EOF 0014 buf = f.read(n) # read up to n bytes 0015 f.truncate([size]) # truncate file at to at most size (default: current pos) 0016 f.write(buf) # write at current position 0017 f.writelines(list) # for line in list: f.write(line) 0018 0019 Notes: 0020 - fileno() is left unimplemented so that code which uses it triggers 0021 an exception early. 0022 - There's a simple test set (see end of this file) - not yet updated 0023 for DBRecIO. 0024 - readline() is not implemented yet. 0025 0026 0027 From: 0028 Itamar Shtull-Trauring <itamar@maxnm.com> 0029 """ 0030 0031 import errno 0032 import string 0033 0034 class DBRecIO: 0035 def __init__(self, db, key, txn=None): 0036 self.db = db 0037 self.key = key 0038 self.txn = txn 0039 self.len = None 0040 self.pos = 0 0041 self.closed = 0 0042 self.softspace = 0 0043 0044 def close(self): 0045 if not self.closed: 0046 self.closed = 1 0047 del self.db, self.txn 0048 0049 def isatty(self): 0050 if self.closed: 0051 raise ValueError, "I/O operation on closed file" 0052 return 0 0053 0054 def seek(self, pos, mode = 0): 0055 if self.closed: 0056 raise ValueError, "I/O operation on closed file" 0057 if mode == 1: 0058 pos = pos + self.pos 0059 elif mode == 2: 0060 pos = pos + self.len 0061 self.pos = max(0, pos) 0062 0063 def tell(self): 0064 if self.closed: 0065 raise ValueError, "I/O operation on closed file" 0066 return self.pos 0067 0068 def read(self, n = -1): 0069 if self.closed: 0070 raise ValueError, "I/O operation on closed file" 0071 if n < 0: 0072 newpos = self.len 0073 else: 0074 newpos = min(self.pos+n, self.len) 0075 0076 dlen = newpos - self.pos 0077 0078 r = self.db.get(key, txn=self.txn, dlen=dlen, doff=self.pos) 0079 self.pos = newpos 0080 return r 0081 0082 __fixme = """ 0083 def readline(self, length=None): 0084 if self.closed: 0085 raise ValueError, "I/O operation on closed file" 0086 if self.buflist: 0087 self.buf = self.buf + string.joinfields(self.buflist, '') 0088 self.buflist = [] 0089 i = string.find(self.buf, '\n', self.pos) 0090 if i < 0: 0091 newpos = self.len 0092 else: 0093 newpos = i+1 0094 if length is not None: 0095 if self.pos + length < newpos: 0096 newpos = self.pos + length 0097 r = self.buf[self.pos:newpos] 0098 self.pos = newpos 0099 return r 0100 0101 def readlines(self, sizehint = 0): 0102 total = 0 0103 lines = [] 0104 line = self.readline() 0105 while line: 0106 lines.append(line) 0107 total += len(line) 0108 if 0 < sizehint <= total: 0109 break 0110 line = self.readline() 0111 return lines 0112 """ 0113 0114 def truncate(self, size=None): 0115 if self.closed: 0116 raise ValueError, "I/O operation on closed file" 0117 if size is None: 0118 size = self.pos 0119 elif size < 0: 0120 raise IOError(errno.EINVAL, 0121 "Negative size not allowed") 0122 elif size < self.pos: 0123 self.pos = size 0124 self.db.put(key, "", txn=self.txn, dlen=self.len-size, doff=size) 0125 0126 def write(self, s): 0127 if self.closed: 0128 raise ValueError, "I/O operation on closed file" 0129 if not s: return 0130 if self.pos > self.len: 0131 self.buflist.append('\0'*(self.pos - self.len)) 0132 self.len = self.pos 0133 newpos = self.pos + len(s) 0134 self.db.put(key, s, txn=self.txn, dlen=len(s), doff=self.pos) 0135 self.pos = newpos 0136 0137 def writelines(self, list): 0138 self.write(string.joinfields(list, '')) 0139 0140 def flush(self): 0141 if self.closed: 0142 raise ValueError, "I/O operation on closed file" 0143 0144 0145 """ 0146 # A little test suite 0147 0148 def _test(): 0149 import sys 0150 if sys.argv[1:]: 0151 file = sys.argv[1] 0152 else: 0153 file = '/etc/passwd' 0154 lines = open(file, 'r').readlines() 0155 text = open(file, 'r').read() 0156 f = StringIO() 0157 for line in lines[:-2]: 0158 f.write(line) 0159 f.writelines(lines[-2:]) 0160 if f.getvalue() != text: 0161 raise RuntimeError, 'write failed' 0162 length = f.tell() 0163 print 'File length =', length 0164 f.seek(len(lines[0])) 0165 f.write(lines[1]) 0166 f.seek(0) 0167 print 'First line =', repr(f.readline()) 0168 here = f.tell() 0169 line = f.readline() 0170 print 'Second line =', repr(line) 0171 f.seek(-len(line), 1) 0172 line2 = f.read(len(line)) 0173 if line != line2: 0174 raise RuntimeError, 'bad result after seek back' 0175 f.seek(len(line2), 1) 0176 list = f.readlines() 0177 line = list[-1] 0178 f.seek(f.tell() - len(line)) 0179 line2 = f.read() 0180 if line != line2: 0181 raise RuntimeError, 'bad result after seek back from EOF' 0182 print 'Read', len(list), 'more lines' 0183 print 'File length =', f.tell() 0184 if f.tell() != length: 0185 raise RuntimeError, 'bad length' 0186 f.close() 0187 0188 if __name__ == '__main__': 0189 _test() 0190 """ 0191
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