Lib/test/test_bufio.py

   1 from test_support import verify, TestFailed, TESTFN
   2
   3 # Simple test to ensure that optimizations in fileobject.c deliver
   4 # the expected results.  For best testing, run this under a debug-build
   5 # Python too (to exercise asserts in the C code).
   6
   7 # Repeat string 'pattern' as often as needed to reach total length
   8 # 'length'.  Then call try_one with that string, a string one larger
   9 # than that, and a string one smaller than that.  The main driver
  10 # feeds this all small sizes and various powers of 2, so we exercise
  11 # all likely stdio buffer sizes, and "off by one" errors on both
  12 # sides.
  13 def drive_one(pattern, length):
  14     q, r = divmod(length, len(pattern))
  15     teststring = pattern * q + pattern[:r]
  16     verify(len(teststring) == length)
  17     try_one(teststring)
  18     try_one(teststring + "x")
  19     try_one(teststring[:-1])
  20
  21 # Write s + "\n" + s to file, then open it and ensure that successive
  22 # .readline()s deliver what we wrote.
  23 def try_one(s):
  24     # Since C doesn't guarantee we can write/read arbitrary bytes in text
  25     # files, use binary mode.
  26     f = open(TESTFN, "wb")
  27     # write once with \n and once without
  28     f.write(s)
  29     f.write("\n")
  30     f.write(s)
  31     f.close()
  32     f = open(TESTFN, "rb")
  33     line = f.readline()
  34     if line != s + "\n":
  35         raise TestFailed("Expected %r got %r" % (s + "\n", line))
  36     line = f.readline()
  37     if line != s:
  38         raise TestFailed("Expected %r got %r" % (s, line))
  39     line = f.readline()
  40     if line:
  41         raise TestFailed("Expected EOF but got %r" % line)
  42     f.close()
  43
  44 # A pattern with prime length, to avoid simple relationships with
  45 # stdio buffer sizes.
  46 primepat = "1234567890\00\01\02\03\04\05\06"
  47
  48 nullpat = "\0" * 1000
  49
  50 try:
  51     for size in range(1, 257) + [512, 1000, 1024, 2048, 4096, 8192, 10000,
  52                       16384, 32768, 65536, 1000000]:
  53         drive_one(primepat, size)
  54         drive_one(nullpat, size)
  55 finally:
  56     try:
  57         import os
  58         os.unlink(TESTFN)
  59     except:
  60         pass