Lib/test/test_bufio.py

   1 import unittest
   2 from test import test_support as support
   3
   4 import io # C implementation.
   5 import _pyio as pyio # Python implementation.
   6
   7 # Simple test to ensure that optimizations in the IO library deliver the
   8 # expected results.  For best testing, run this under a debug-build Python too
   9 # (to exercise asserts in the C code).
  10
  11 lengths = list(range(1, 257)) + [512, 1000, 1024, 2048, 4096, 8192, 10000,
  12                                  16384, 32768, 65536, 1000000]
  13
  14 class BufferSizeTest(unittest.TestCase):
  15     def try_one(self, s):
  16         # Write s + "\n" + s to file, then open it and ensure that successive
  17         # .readline()s deliver what we wrote.
  18
  19         # Ensure we can open TESTFN for writing.
  20         support.unlink(support.TESTFN)
  21
  22         # Since C doesn't guarantee we can write/read arbitrary bytes in text
  23         # files, use binary mode.
  24         f = self.open(support.TESTFN, "wb")
  25         try:
  26             # write once with \n and once without
  27             f.write(s)
  28             f.write(b"\n")
  29             f.write(s)
  30             f.close()
  31             f = open(support.TESTFN, "rb")
  32             line = f.readline()
  33             self.assertEqual(line, s + b"\n")
  34             line = f.readline()
  35             self.assertEqual(line, s)
  36             line = f.readline()
  37             self.assertTrue(not line) # Must be at EOF
  38             f.close()
  39         finally:
  40             support.unlink(support.TESTFN)
  41
  42     def drive_one(self, pattern):
  43         for length in lengths:
  44             # Repeat string 'pattern' as often as needed to reach total length
  45             # 'length'.  Then call try_one with that string, a string one larger
  46             # than that, and a string one smaller than that.  Try this with all
  47             # small sizes and various powers of 2, so we exercise all likely
  48             # stdio buffer sizes, and "off by one" errors on both sides.
  49             q, r = divmod(length, len(pattern))
  50             teststring = pattern * q + pattern[:r]
  51             self.assertEqual(len(teststring), length)
  52             self.try_one(teststring)
  53             self.try_one(teststring + b"x")
  54             self.try_one(teststring[:-1])
  55
  56     def test_primepat(self):
  57         # A pattern with prime length, to avoid simple relationships with
  58         # stdio buffer sizes.
  59         self.drive_one(b"1234567890\00\01\02\03\04\05\06")
  60
  61     def test_nullpat(self):
  62         self.drive_one(bytes(1000))
  63
  64
  65 class CBufferSizeTest(BufferSizeTest):
  66     open = io.open
  67
  68 class PyBufferSizeTest(BufferSizeTest):
  69     open = staticmethod(pyio.open)
  70
  71 class BuiltinBufferSizeTest(BufferSizeTest):
  72     open = open
  73
  74
  75 def test_main():
  76     support.run_unittest(CBufferSizeTest, PyBufferSizeTest, BuiltinBufferSizeTest)
  77
  78 if __name__ == "__main__":
  79     test_main()