On Tue, Nov 8, 2022 at 4:26 AM Alex Bennée <alex.ben...@linaro.org> wrote:
>
> This attempts to deal with the problem of login prompts not being
> guaranteed to be terminated with a newline. The solution to this is to
> peek at the incoming data looking to see if we see an up-coming match
> before we fall back to the old readline() logic. The reason to mostly
> rely on readline is because I am occasionally seeing the peek stalling
> despite data being there.
>
> This seems kinda hacky and gross so I'm open to alternative approaches
> and cleaner python code.
Hm, yeah. I'm not too sure. I guess if it works, it works -- I don't
have better suggestions for you here. I need to rewrite a good bit of
how machine.py works, and time will tell if we still need this kind of
workaround when I do. I guess if it doesn't hurt anything, go for it.
*shrug*
>
> Signed-off-by: Alex Bennée <alex.ben...@linaro.org>
> ---
> tests/avocado/avocado_qemu/__init__.py | 89 +++++++++++++++++++++++++-
> 1 file changed, 88 insertions(+), 1 deletion(-)
>
> diff --git a/tests/avocado/avocado_qemu/__init__.py
> b/tests/avocado/avocado_qemu/__init__.py
> index 910f3ba1ea..d6ff68e171 100644
> --- a/tests/avocado/avocado_qemu/__init__.py
> +++ b/tests/avocado/avocado_qemu/__init__.py
> @@ -131,6 +131,58 @@ def pick_default_qemu_bin(bin_prefix='qemu-system-',
> arch=None):
> return path
> return None
>
> +def _peek_ahead(console, min_match, success_message):
> + """
> + peek ahead in the console stream keeping an eye out for the
> + success message.
> +
> + Returns some message to process or None, indicating the normal
> + readline should occur.
> + """
> + console_logger = logging.getLogger('console')
> + peek_len = 0
> + retries = 0
> +
> + while True:
> + try:
> + old_peek_len = peek_len
> + peek_ahead = console.peek(min_match).decode()
> + peek_len = len(peek_ahead)
> +
> + # if we get stuck too long lets just fallback to readline
> + if peek_len <= old_peek_len:
> + retries += 1
> + if retries > 10:
> + return None
> +
> + # if we see a newline in the peek we can let safely bail
> + # and let the normal readline() deal with it
> + if peek_ahead.endswith(('\n', '\r', '\r\n')):
> + return None
> +
> + # if we haven't seen enough for the whole message but the
> + # first part matches lets just loop again
> + if len(peek_ahead) < min_match and \
> + success_message[:peek_len] in peek_ahead:
> + continue
> +
> + # if we see the whole success_message we are done, consume
> + # it and pass back so we can exit to the user
> + if success_message in peek_ahead:
> + return console.read(peek_len).decode()
> +
> + # of course if we've seen enough then this line probably
> + # doesn't contain what we are looking for, fallback
> + if peek_len > min_match:
> + return None
> +
> + except UnicodeDecodeError:
> + console_logger.log("error in decode of peek")
> + return None
> +
> + # we should never get here
> + return None
> +
>
> def _console_interaction(test, success_message, failure_message,
> send_string, keep_sending=False, vm=None):
> @@ -139,17 +191,52 @@ def _console_interaction(test, success_message,
> failure_message,
> vm = test.vm
> console = vm.console_socket.makefile(mode='rb', encoding='utf-8')
> console_logger = logging.getLogger('console')
> +
> + # Establish the minimum number of bytes we would need to
> + # potentially match against success_message
> + if success_message is not None:
> + min_match = len(success_message)
> + else:
> + min_match = 0
> +
> + console_logger.debug("looking for %d:(%s), sending %s (always=%s)",
> + min_match, success_message, send_string,
> keep_sending)
> +
> while True:
> + msg = None
> +
> + # First send our string, optionally repeating the send next
> + # cycle.
> if send_string:
> vm.console_socket.sendall(send_string.encode())
> if not keep_sending:
> send_string = None # send only once
> +
> + # If the console has no data to read we briefly
> + # sleep before continuing.
> + if not console.readable():
> + time.sleep(0.1)
> + continue
> +
> try:
> - msg = console.readline().decode().strip()
> +
> + # First we shall peek ahead for a potential match to cover
> waiting
> + # for lines without any newlines.
> + if min_match > 0:
> + msg = _peek_ahead(console, min_match, success_message)
> +
> + # otherwise we block here for a full line
> + if not msg:
> + msg = console.readline().decode().strip()
> +
> except UnicodeDecodeError:
> + console_logger.debug("skipped unicode error")
> msg = None
> +
> + # if nothing came out we continue and try again
> if not msg:
> continue
> +
> console_logger.debug(msg)
> if success_message is None or success_message in msg:
> break
> --
> 2.34.1
>
>
