import cgi
from io import BytesIO


def check(content):
    data = """---123
Content-Disposition: form-data; name="upload"; filename="fake.txt"
Content-Type: text/plain

%s
---123--
""" % content
    environ = {
        'CONTENT_LENGTH':   str(len(data)),
        'CONTENT_TYPE':     'multipart/form-data; boundary=-123',
        'REQUEST_METHOD':   'POST',
    }
    # assert gen_result(data, environ) == {'upload': content.encode('latin1')}
    fake_stdin = BytesIO(data.encode('ascii'))
    fake_stdin.seek(0)
    form = cgi.FieldStorage(fp=fake_stdin, environ=environ, encoding='ascii')
    return form


def main():
    maxline = 1 << 16
    check('x' * 512)            # OK
    check('x' * 1010)           # ResourceWarning
    check('x' * (maxline - 1))  # ResourceWarning


if __name__ == '__main__':
    main()