Send a message to a message queue
#include <mqueue.h> #include <time.h> int mq_timedsend( mqd_t mqdes, const char * msg_ptr, size_t msg_len, unsigned int msg_prio, const struct timespec * abs_timeout );
- The descriptor of the message queue you want to put the message into, returned by mq_open().
- A pointer to the message data.
- The size of the buffer, in bytes.
- The priority of the message, in the range from 0 to (MQ_PRIO_MAX-1).
- A pointer to a timespec structure that specifies the absolute time (not the relative time to the current time) to wait before the function stops trying to receive messages.
- For the traditional implementation, libc
Use the -l c option to qcc to link against this library. This library is usually included automatically.
- For the alternate implementation using asynchronous messages,
Use the -l mq option to qcc to link against this library.
The mq_timedsend() function puts a message of size msg_len and pointed to by msg_ptr into the queue indicated by mqdes. The new message has a priority of msg_prio.
|Neutrino supports two implementations of message queues: a traditional implementation, and an alternate one that uses asynchronous messages. For more information, see the entry for mq and mqueue in the Utilities Reference.|
The queue maintained is in priority order, and in FIFO order within the same priority.
If the number of elements on the specified queue is equal to its mq_maxmsg, and O_NONBLOCK (in oflag of mq_open()) hasn't been set, the call to mq_timedsend() blocks. It becomes unblocked when there's room on the queue to send the given message. If more than one mq_timedsend() is blocked on a given queue, and space becomes available in that queue to send, then the mq_timedsend() with the highest priority message is unblocked.
In the traditional (mqueue) implementation, calling write() with mqdes is analogous to calling mq_timedsend() with a msg_prio of 0.
-1 if an error occurred (errno is set). Any other value indicates success.
- The O_NONBLOCK flag was set when opening the queue, and the specified queue is full.
- The mqdes argument doesn't represent a valid message queue descriptor, or mqdes isn't opened for writing.
- The call was interrupted by a signal.
- One of the following is true:
- The msg_len is negative.
- The msg_prio is greater than (MQ_PRIO_MAX-1).
- The msg_prio is less than 0.
- The MQ_PRIO_RESTRICT flag is set in the mq_attr member of mqdes, and msg_prio is greater than the priority of the calling process.
- The msg_len argument is greater than the msgsize associated with the specified queue.
- The timeout value was exceeded.
See the example for mq_timedreceive().
mq, mqueue in the Utilities Reference