def get(self, block=True, timeout=None):
"""
Remove and return an item from the queue. If *block* is ``True`` and
*timeout* is ``None`` (the default), block if necessary until an item
is available. If *timeout* is a positive number, it blocks at most
*timeout* seconds and raises the :class:`queue.Empty` exception if no
item was available within that time. Otherwise (block is ``False``),
return an item if one is immediately available, else raise the
:class:`queue.Empty` exception (*timeout* is ignored in that case).
"""
if not block:
timeout = 0.0
elif timeout is None:
timeout = float('inf')
buffer = ffi.new('char[]', self._max_msg_size)
size = ffi.new('size_t *', self._max_msg_size)
priority = ffi.new('unsigned int *')
res = lib.posixmq_get(self._queue_id, buffer, size, priority, timeout)
if res == lib.POSIXMQ_E_TIMEOUT:
raise queue.Empty
elif res != lib.POSIXMQ_OK:
raise QueueError(res)
data_size = size[0]
data = ffi.buffer(buffer[0:data_size])[:]
return pickle.loads(data)
def unlink(name):
"""
Remove a message queue *name*.
"""
q_name = ffi.new('char[]', name.encode('utf-8'))
res = lib.posixmq_unlink(q_name)
if res != lib.POSIXMQ_OK:
raise QueueError(res)
def __init__(self, name, maxsize=10, maxmsgsize=1024):
"""
Constructor for message queue. *name* is an unique identifier of the
queue, must starts with ``/``. *maxsize* is an integer that sets
the upperbound limit on the number of items that can be placed in
the queue (maximum value depends on system limit). *maxmsgsize*
is a maximum size of the message in bytes (maximum value depends
on hard system limit).
"""
queue_name = ffi.new('char[]', name.encode('utf-8'))
queue_id = ffi.new('int *')
res = lib.posixmq_open(queue_name, queue_id, maxmsgsize, maxsize)
if res != lib.POSIXMQ_OK:
raise QueueError(res)
self._queue_id = queue_id[0]
self._name = name
self._maxsize = maxsize
self._max_msg_size = maxmsgsize
def qattr(self):
"""
Return attributes of the message queue as a :class:`dict`:
``{'size': 5, 'max_size': 10, 'max_msgbytes': 1024}``.
"""
attr = ffi.new('struct mq_attr *')
res = lib.posixmq_get_attr(self._queue_id, attr)
if res != lib.POSIXMQ_OK:
raise QueueError(res)
return {
'size': attr.mq_curmsgs,
'max_size': attr.mq_maxmsg,
'max_msgbytes': attr.mq_msgsize,
}
