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.
Signed-off-by: Alex Bennée <alex.ben...@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <phi...@linaro.org>
Message-Id: <20221111145529.4020801-3-alex.ben...@linaro.org>
diff --git a/tests/avocado/avocado_qemu/__init__.py
b/tests/avocado/avocado_qemu/__init__.py
index 910f3ba1ea..7469a06804 100644
--- a/tests/avocado/avocado_qemu/__init__.py
+++ b/tests/avocado/avocado_qemu/__init__.py
@@ -131,6 +131,59 @@ def pick_default_qemu_bin(bin_prefix='qemu-system-',
arch=None):
return path
return None
+def _peek_ahead(console, min_match, success_as_str):
+ """
+ peek ahead in the console stream keeping an eye out for the
+ success message. Because we are partially peeking into the data
+ stream we do everything as bytes to avoid partial UTF decode
+ issues.
+
+ Returns some message to process or None, indicating the normal
+ readline should occur.
+ """
+ console_logger = logging.getLogger('console')
+ success_message = bytes(success_as_str, 'utf-8')
+ peek_len = 0
+ retries = 0
+
+ while True:
+ old_peek_len = peek_len
+ peek_ahead = console.peek(min_match)
+ peek_len = len(peek_ahead)
+
+ # if we get stuck too long lets just fallback to readline
+ if peek_len <= old_peek_len:
+ time.sleep(0.001 * retries)
+ retries += 1
+ if retries > 20:
+ return None
+ else:
+ retries = 0
+
+ # 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((b'\n', b'\r')):
+ 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
+
+ # we should never get here
+ return None
+
def _console_interaction(test, success_message, failure_message,
send_string, keep_sending=False, vm=None):
@@ -139,17 +192,52 @@ 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
