Queue

Message Queuing is a common means of data exchange between threads in an operating system.

1. Queue API

2. os_queue.c code

#include "mxos.h"
#define os_queue_log(M, ...) custom_log("OS", M, ##__VA_ARGS__)

static mxos_queue_t os_queue = NULL;
typedef struct _msg
{
    int value;
} msg_t;

void receiver_thread( mxos_thread_arg_t arg )
{
    UNUSED_PARAMETER( arg );

    OSStatus err;
    msg_t received = { 0 };

    while ( 1 )
    {
        /*Wait until queue has data*/
        err = mxos_rtos_pop_from_queue( &os_queue, &received, mxos_WAIT_FOREVER );
        require_noerr( err, exit );

        os_queue_log( "Received data from queue:value = %d",received.value );
    }

    exit:
    if ( err != kNoErr )
        os_queue_log( "Receiver exit with err: %d", err );

    mxos_rtos_delete_thread( NULL );
}

void sender_thread( mxos_thread_arg_t arg )
{
    UNUSED_PARAMETER( arg );
    OSStatus err = kNoErr;

    msg_t my_message = { 0 };

    while ( 1 )
    {
        my_message.value++;
        mxos_rtos_push_to_queue( &os_queue, &my_message, mxos_WAIT_FOREVER );
        require_noerr( err, exit );

        os_queue_log( "send data to queue" );
        mxos_thread_sleep( 1 );
    }

    exit:
    if ( err != kNoErr )
        os_queue_log( "Sender exit with err: %d", err );

    mxos_rtos_delete_thread( NULL );
}

int application_start( void )
{
    OSStatus err = kNoErr;

    err = mxos_rtos_init_queue( &os_queue, "queue", sizeof(msg_t), 3 );
    require_noerr( err, exit );

    err = mxos_rtos_create_thread( NULL, mxos_APPLICATION_PRIORITY, "receiver", receiver_thread, 0x500, 0 );
    require_noerr( err, exit );

    err = mxos_rtos_create_thread( NULL, mxos_APPLICATION_PRIORITY, "sender", sender_thread, 0x500, 0 );
    require_noerr( err, exit );

    exit:
    if ( err != kNoErr )
        os_queue_log( "Thread exit with err: %d", err );

    mxos_rtos_delete_thread( NULL );

    return err;
}

♦ Achieve:

• The system creates two threads, one thread sends data to the message queue, one thread receives data from the message queue, and prints the data information.
• The data sent by the sending thread is incremented by 1 each time, and each thread sleeps for 1 second.

♦  Main function code annotations:

1) Invoke the mxos API to initialize a message queue: err = mxos_rtos_init_queue( &os_queue, “queue”, sizeof(msg_t), 3 );

2) Call the mxos API to write data to the message queue:

mxos_rtos_push_to_queue( &os_queue, &my_message, mxos_WAIT_FOREVER );

3) Call the mxos API to read data from the message queue：

err = mxos_rtos_pop_from_queue( &os_queue, &received, mxos_WAIT_FOREVER );

4)Call the mxos API to destroy an RTOS timer: mxos_deinit_timer( &timer_handle );