Method _fs_supports_holes

Lib/test/test_tarfile.py:1294–1313

()

    @staticmethod
    def _fs_supports_holes():
        # Return True if the platform knows the st_blocks stat attribute and
        # uses st_blocks units of 512 bytes, and if the filesystem is able to
        # store holes of 4 KiB in files.
        #
        # The function returns False if page size is larger than 4 KiB.
        # For example, ppc64 uses pages of 64 KiB.
        if sys.platform.startswith(("linux", "android")):
            # Linux evidentially has 512 byte st_blocks units.
            name = os.path.join(TEMPDIR, "sparse-test")
            with open(name, "wb") as fobj:
                # Seek to "punch a hole" of 4 KiB
                fobj.seek(4096)
                fobj.write(b'x' * 4096)
                fobj.truncate()
            s = os.stat(name)
            os_helper.unlink(name)
            return (s.st_blocks * 512 < s.st_size)
        else:
            return False


class PaxReadTest(LongnameTest, ReadTest, unittest.TestCase):