Lib/test/test_largefile.py

   1 #!python
   2
   3 #----------------------------------------------------------------------
   4 # test largefile support on system where this makes sense
   5 #
   6 #----------------------------------------------------------------------
   7
   8 from test import test_support
   9 import os, struct, stat, sys
  10
  11 try:
  12     import signal
  13     # The default handler for SIGXFSZ is to abort the process.
  14     # By ignoring it, system calls exceeding the file size resource
  15     # limit will raise IOError instead of crashing the interpreter.
  16     oldhandler = signal.signal(signal.SIGXFSZ, signal.SIG_IGN)
  17 except (ImportError, AttributeError):
  18     pass
  19
  20
  21 # create >2GB file (2GB = 2147483648 bytes)
  22 size = 2500000000L
  23 name = test_support.TESTFN
  24
  25
  26 # On Windows this test comsumes large resources; It takes a long time to build
  27 # the >2GB file and takes >2GB of disk space therefore the resource must be
  28 # enabled to run this test.  If not, nothing after this line stanza will be
  29 # executed.
  30 if sys.platform[:3] == 'win':
  31     test_support.requires(
  32         'largefile',
  33         'test requires %s bytes and a long time to run' % str(size))
  34 else:
  35     # Only run if the current filesystem supports large files.
  36     # (Skip this test on Windows, since we now always support large files.)
  37     f = open(test_support.TESTFN, 'wb')
  38     try:
  39         # 2**31 == 2147483648
  40         f.seek(2147483649L)
  41         # Seeking is not enough of a test: you must write and flush, too!
  42         f.write("x")
  43         f.flush()
  44     except (IOError, OverflowError):
  45         f.close()
  46         os.unlink(test_support.TESTFN)
  47         raise test_support.TestSkipped, \
  48               "filesystem does not have largefile support"
  49     else:
  50         f.close()
  51
  52
  53 def expect(got_this, expect_this):
  54     if test_support.verbose:
  55         print '%r =?= %r ...' % (got_this, expect_this),
  56     if got_this != expect_this:
  57         if test_support.verbose:
  58             print 'no'
  59         raise test_support.TestFailed, 'got %r, but expected %r' %\
  60               (got_this, expect_this)
  61     else:
  62         if test_support.verbose:
  63             print 'yes'
  64
  65
  66 # test that each file function works as expected for a large (i.e. >2GB, do
  67 # we have to check >4GB) files
  68
  69 if test_support.verbose:
  70     print 'create large file via seek (may be sparse file) ...'
  71 f = open(name, 'wb')
  72 f.write('z')
  73 f.seek(0)
  74 f.seek(size)
  75 f.write('a')
  76 f.flush()
  77 if test_support.verbose:
  78     print 'check file size with os.fstat'
  79 expect(os.fstat(f.fileno())[stat.ST_SIZE], size+1)
  80 f.close()
  81 if test_support.verbose:
  82     print 'check file size with os.stat'
  83 expect(os.stat(name)[stat.ST_SIZE], size+1)
  84
  85 if test_support.verbose:
  86     print 'play around with seek() and read() with the built largefile'
  87 f = open(name, 'rb')
  88 expect(f.tell(), 0)
  89 expect(f.read(1), 'z')
  90 expect(f.tell(), 1)
  91 f.seek(0)
  92 expect(f.tell(), 0)
  93 f.seek(0, 0)
  94 expect(f.tell(), 0)
  95 f.seek(42)
  96 expect(f.tell(), 42)
  97 f.seek(42, 0)
  98 expect(f.tell(), 42)
  99 f.seek(42, 1)
 100 expect(f.tell(), 84)
 101 f.seek(0, 1)
 102 expect(f.tell(), 84)
 103 f.seek(0, 2) # seek from the end
 104 expect(f.tell(), size + 1 + 0)
 105 f.seek(-10, 2)
 106 expect(f.tell(), size + 1 - 10)
 107 f.seek(-size-1, 2)
 108 expect(f.tell(), 0)
 109 f.seek(size)
 110 expect(f.tell(), size)
 111 expect(f.read(1), 'a') # the 'a' that was written at the end of the file above
 112 f.seek(-size-1, 1)
 113 expect(f.read(1), 'z')
 114 expect(f.tell(), 1)
 115 f.close()
 116
 117 if test_support.verbose:
 118     print 'play around with os.lseek() with the built largefile'
 119 f = open(name, 'rb')
 120 expect(os.lseek(f.fileno(), 0, 0), 0)
 121 expect(os.lseek(f.fileno(), 42, 0), 42)
 122 expect(os.lseek(f.fileno(), 42, 1), 84)
 123 expect(os.lseek(f.fileno(), 0, 1), 84)
 124 expect(os.lseek(f.fileno(), 0, 2), size+1+0)
 125 expect(os.lseek(f.fileno(), -10, 2), size+1-10)
 126 expect(os.lseek(f.fileno(), -size-1, 2), 0)
 127 expect(os.lseek(f.fileno(), size, 0), size)
 128 expect(f.read(1), 'a') # the 'a' that was written at the end of the file above
 129 f.close()
 130
 131 if hasattr(f, 'truncate'):
 132     if test_support.verbose:
 133         print 'try truncate'
 134     f = open(name, 'r+b')
 135     f.seek(0, 2)
 136     expect(f.tell(), size+1)    # else we've lost track of the true size
 137     # Cut it back via seek + truncate with no argument.
 138     newsize = size - 10
 139     f.seek(newsize)
 140     f.truncate()
 141     expect(f.tell(), newsize)   # else pointer moved
 142     f.seek(0, 2)
 143     expect(f.tell(), newsize)   # else wasn't truncated
 144     # Ensure that truncate(smaller than true size) shrinks the file.
 145     newsize -= 1
 146     f.seek(42)
 147     f.truncate(newsize)
 148     expect(f.tell(), 42)        # else pointer moved
 149     f.seek(0, 2)
 150     expect(f.tell(), newsize)   # else wasn't truncated
 151
 152     # XXX truncate(larger than true size) is ill-defined across platforms
 153
 154     # cut it waaaaay back
 155     f.seek(0)
 156     f.truncate(1)
 157     expect(f.tell(), 0)         # else pointer moved
 158     expect(len(f.read()), 1)    # else wasn't truncated
 159
 160     f.close()
 161
 162 os.unlink(name)