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 and Mac OSX this test comsumes large resources; It takes
  27 # a long time to build the >2GB file and takes >2GB of disk space
  28 # therefore the resource must be enabled to run this test.  If not,
  29 # nothing after this line stanza will be executed.
  30 if sys.platform[:3] == 'win' or sys.platform == 'darwin':
  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 try:
  73     f.write('z')
  74     f.seek(0)
  75     f.seek(size)
  76     f.write('a')
  77     f.flush()
  78     if test_support.verbose:
  79         print 'check file size with os.fstat'
  80     expect(os.fstat(f.fileno())[stat.ST_SIZE], size+1)
  81 finally:
  82     f.close()
  83 if test_support.verbose:
  84     print 'check file size with os.stat'
  85 expect(os.stat(name)[stat.ST_SIZE], size+1)
  86
  87 if test_support.verbose:
  88     print 'play around with seek() and read() with the built largefile'
  89 f = open(name, 'rb')
  90 try:
  91     expect(f.tell(), 0)
  92     expect(f.read(1), 'z')
  93     expect(f.tell(), 1)
  94     f.seek(0)
  95     expect(f.tell(), 0)
  96     f.seek(0, 0)
  97     expect(f.tell(), 0)
  98     f.seek(42)
  99     expect(f.tell(), 42)
 100     f.seek(42, 0)
 101     expect(f.tell(), 42)
 102     f.seek(42, 1)
 103     expect(f.tell(), 84)
 104     f.seek(0, 1)
 105     expect(f.tell(), 84)
 106     f.seek(0, 2) # seek from the end
 107     expect(f.tell(), size + 1 + 0)
 108     f.seek(-10, 2)
 109     expect(f.tell(), size + 1 - 10)
 110     f.seek(-size-1, 2)
 111     expect(f.tell(), 0)
 112     f.seek(size)
 113     expect(f.tell(), size)
 114     expect(f.read(1), 'a') # the 'a' that was written at the end of file above
 115     f.seek(-size-1, 1)
 116     expect(f.read(1), 'z')
 117     expect(f.tell(), 1)
 118 finally:
 119     f.close()
 120
 121 if test_support.verbose:
 122     print 'play around with os.lseek() with the built largefile'
 123 f = open(name, 'rb')
 124 try:
 125     expect(os.lseek(f.fileno(), 0, 0), 0)
 126     expect(os.lseek(f.fileno(), 42, 0), 42)
 127     expect(os.lseek(f.fileno(), 42, 1), 84)
 128     expect(os.lseek(f.fileno(), 0, 1), 84)
 129     expect(os.lseek(f.fileno(), 0, 2), size+1+0)
 130     expect(os.lseek(f.fileno(), -10, 2), size+1-10)
 131     expect(os.lseek(f.fileno(), -size-1, 2), 0)
 132     expect(os.lseek(f.fileno(), size, 0), size)
 133     expect(f.read(1), 'a') # the 'a' that was written at the end of file above
 134 finally:
 135     f.close()
 136
 137 if hasattr(f, 'truncate'):
 138     if test_support.verbose:
 139         print 'try truncate'
 140     f = open(name, 'r+b')
 141     try:
 142         f.seek(0, 2)
 143         expect(f.tell(), size+1)    # else we've lost track of the true size
 144         # Cut it back via seek + truncate with no argument.
 145         newsize = size - 10
 146         f.seek(newsize)
 147         f.truncate()
 148         expect(f.tell(), newsize)   # else pointer moved
 149         f.seek(0, 2)
 150         expect(f.tell(), newsize)   # else wasn't truncated
 151         # Ensure that truncate(smaller than true size) shrinks the file.
 152         newsize -= 1
 153         f.seek(42)
 154         f.truncate(newsize)
 155         expect(f.tell(), 42)        # else pointer moved
 156         f.seek(0, 2)
 157         expect(f.tell(), newsize)   # else wasn't truncated
 158
 159         # XXX truncate(larger than true size) is ill-defined across platforms
 160
 161         # cut it waaaaay back
 162         f.seek(0)
 163         f.truncate(1)
 164         expect(f.tell(), 0)         # else pointer moved
 165         expect(len(f.read()), 1)    # else wasn't truncated
 166
 167     finally:
 168         f.close()
 169
 170 os.unlink(name)