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3423
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1 # port of StringIO.py using arrays
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2 # ArrayIO.py
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3 # jjk 02/28/96 001 direct mod of StringIO, test suite checks out
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4 # jjk 02/28/96 002 inherit from StringIO, test suite checks out
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5 # jjk 02/28/96 003 add __xx__() functions
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6 #
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7 # class ArrayIO implements file-like objects that read/write a
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8 # string buffer (a.k.a. "memory files").
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9 #
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10 # all methods that interface with ArrayIO pass strings. Internally, however,
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11 # ArrayIO uses an array object.
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12 #
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13 # the interface is the same as StringIO.py
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14 # also handles len(a), a[i], a[i]='x', a[i:j], a[i:j] = aString
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15 #
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16
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17 import string
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18 import array
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19 import StringIO
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20
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21 class ArrayIO(StringIO.StringIO):
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22 # jjk 02/28/96
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23 def __init__(self, buf = ''):
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24 #jjk 02/28/96
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25 self.buf = array.array('c', buf)
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26 self.pos = 0
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27 self.closed = 0
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28 def __len__(self):
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29 #jjk 02/28/96
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30 return len(self.buf)
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31 def __getitem__(self, key):
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32 #jjk 02/28/96
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33 return self.buf[key]
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34 def __setitem__(self, key, item):
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35 #jjk 02/28/96
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36 self.buf[key] = item
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37 def __getslice__(self, i, j):
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38 #jjk 02/28/96
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39 return self.buf[i:j].tostring()
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40 def __setslice__(self, i, j, aString):
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41 #jjk 02/28/96
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42 self.buf[i:j] = array.array('c', aString)
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43 def read(self, n = 0):
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44 #jjk 02/28/96
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45 r = StringIO.StringIO.read(self, n)
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46 return (r.tostring())
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47 def _findCharacter(self, char, start):
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48 #probably very slow
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49 #jjk 02/28/96
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50 for i in range(max(start, 0), len(self.buf)):
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51 if (self.buf[i] == char):
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52 return(i)
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53 return(-1)
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54 def readline(self):
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55 #jjk 02/28/96
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56 i = self._findCharacter('\n', self.pos)
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57 if i < 0:
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58 newpos = len(self.buf)
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59 else:
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60 newpos = i+1
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61 r = self.buf[self.pos:newpos].tostring()
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62 self.pos = newpos
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63 return r
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64 def write(self, s):
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65 #jjk 02/28/96
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66 if not s: return
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67 if self.pos > len(self.buf):
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68 self.buf.fromstring('\0'*(self.pos - len(self.buf)))
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69 newpos = self.pos + len(s)
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70 self.buf[self.pos:newpos] = array.array('c', s)
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71 self.pos = newpos
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72 def getvalue(self):
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73 #jjk 02/28/96
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74 return self.buf.tostring()
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75
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76
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77 # A little test suite
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78 # identical to test suite in StringIO.py , except for "f = ArrayIO()"
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79 # too bad I couldn't inherit this :-)
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80
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81 def test():
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82 import sys
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83 if sys.argv[1:]:
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84 file = sys.argv[1]
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85 else:
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86 file = '/etc/passwd'
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87 lines = open(file, 'r').readlines()
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88 text = open(file, 'r').read()
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89 f = ArrayIO()
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90 for line in lines[:-2]:
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91 f.write(line)
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92 f.writelines(lines[-2:])
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93 if f.getvalue() != text:
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94 raise RuntimeError, 'write failed'
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95 length = f.tell()
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96 print 'File length =', length
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97 f.seek(len(lines[0]))
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98 f.write(lines[1])
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99 f.seek(0)
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100 print 'First line =', `f.readline()`
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101 here = f.tell()
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102 line = f.readline()
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103 print 'Second line =', `line`
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104 f.seek(-len(line), 1)
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105 line2 = f.read(len(line))
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106 if line != line2:
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107 raise RuntimeError, 'bad result after seek back'
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108 f.seek(len(line2), 1)
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109 list = f.readlines()
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110 line = list[-1]
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111 f.seek(f.tell() - len(line))
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112 line2 = f.read()
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113 if line != line2:
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114 raise RuntimeError, 'bad result after seek back from EOF'
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115 print 'Read', len(list), 'more lines'
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116 print 'File length =', f.tell()
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117 if f.tell() != length:
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118 raise RuntimeError, 'bad length'
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119 f.close()
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120
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121 if __name__ == '__main__':
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122 test()
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