Lib/test/test_mmap.py

   1 from test_support import verify, TESTFN
   2 import mmap
   3 import os, re
   4
   5 PAGESIZE = mmap.PAGESIZE
   6
   7 def test_both():
   8     "Test mmap module on Unix systems and Windows"
   9
  10     # Create a file to be mmap'ed.
  11     if os.path.exists(TESTFN):
  12         os.unlink(TESTFN)
  13     f = open(TESTFN, 'w+')
  14
  15     try:    # unlink TESTFN no matter what
  16         # Write 2 pages worth of data to the file
  17         f.write('\0'* PAGESIZE)
  18         f.write('foo')
  19         f.write('\0'* (PAGESIZE-3) )
  20
  21         m = mmap.mmap(f.fileno(), 2 * PAGESIZE)
  22         f.close()
  23
  24         # Simple sanity checks
  25
  26         print type(m)  # SF bug 128713:  segfaulted on Linux
  27         print '  Position of foo:', m.find('foo') / float(PAGESIZE), 'pages'
  28         verify(m.find('foo') == PAGESIZE)
  29
  30         print '  Length of file:', len(m) / float(PAGESIZE), 'pages'
  31         verify(len(m) == 2*PAGESIZE)
  32
  33         print '  Contents of byte 0:', repr(m[0])
  34         verify(m[0] == '\0')
  35         print '  Contents of first 3 bytes:', repr(m[0:3])
  36         verify(m[0:3] == '\0\0\0')
  37
  38         # Modify the file's content
  39         print "\n  Modifying file's content..."
  40         m[0] = '3'
  41         m[PAGESIZE +3: PAGESIZE +3+3] = 'bar'
  42
  43         # Check that the modification worked
  44         print '  Contents of byte 0:', repr(m[0])
  45         verify(m[0] == '3')
  46         print '  Contents of first 3 bytes:', repr(m[0:3])
  47         verify(m[0:3] == '3\0\0')
  48         print '  Contents of second page:',  repr(m[PAGESIZE-1 : PAGESIZE + 7])
  49         verify(m[PAGESIZE-1 : PAGESIZE + 7] == '\0foobar\0')
  50
  51         m.flush()
  52
  53         # Test doing a regular expression match in an mmap'ed file
  54         match = re.search('[A-Za-z]+', m)
  55         if match is None:
  56             print '  ERROR: regex match on mmap failed!'
  57         else:
  58             start, end = match.span(0)
  59             length = end - start
  60
  61             print '  Regex match on mmap (page start, length of match):',
  62             print start / float(PAGESIZE), length
  63
  64             verify(start == PAGESIZE)
  65             verify(end == PAGESIZE + 6)
  66
  67         # test seeking around (try to overflow the seek implementation)
  68         m.seek(0,0)
  69         print '  Seek to zeroth byte'
  70         verify(m.tell() == 0)
  71         m.seek(42,1)
  72         print '  Seek to 42nd byte'
  73         verify(m.tell() == 42)
  74         m.seek(0,2)
  75         print '  Seek to last byte'
  76         verify(m.tell() == len(m))
  77
  78         print '  Try to seek to negative position...'
  79         try:
  80             m.seek(-1)
  81         except ValueError:
  82             pass
  83         else:
  84             verify(0, 'expected a ValueError but did not get it')
  85
  86         print '  Try to seek beyond end of mmap...'
  87         try:
  88             m.seek(1,2)
  89         except ValueError:
  90             pass
  91         else:
  92             verify(0, 'expected a ValueError but did not get it')
  93
  94         print '  Try to seek to negative position...'
  95         try:
  96             m.seek(-len(m)-1,2)
  97         except ValueError:
  98             pass
  99         else:
 100             verify(0, 'expected a ValueError but did not get it')
 101
 102         # Try resizing map
 103         print '  Attempting resize()'
 104         try:
 105             m.resize( 512 )
 106         except SystemError:
 107             # resize() not supported
 108             # No messages are printed, since the output of this test suite
 109             # would then be different across platforms.
 110             pass
 111         else:
 112             # resize() is supported
 113             verify(len(m) == 512,
 114                     "len(m) is %d, but expecting 512" % (len(m),) )
 115             # Check that we can no longer seek beyond the new size.
 116             try:
 117                 m.seek(513,0)
 118             except ValueError:
 119                 pass
 120             else:
 121                 verify(0, 'Could seek beyond the new size')
 122
 123         m.close()
 124
 125     finally:
 126         try:
 127             f.close()
 128         except OSError:
 129             pass
 130         try:
 131             os.unlink(TESTFN)
 132         except OSError:
 133             pass
 134
 135     print ' Test passed'
 136
 137 test_both()