Lightweight message size

davidsherman — Fri, 11 Jul 2014 14:43:20 GMT

I'm trying to understand the message sizing in lightweight messages. I understand that it is in multiples of 32 bits. Let's say I'm trying to pass a structure as a message:

typedef struct

{

unsigned char byte1;

unsigned char *ptr1;

unsigned char byte2;

unsigned char *ptr2;

}messageStruct;

The sizeof() for this structure returns 16 bytes. So, if i create a message queue like this:

uint32_t msgQ[sizeof(LWMSGQ_STRUCT)/sizeof(uint32_t) + sizeof(messageStruct)/sizeof(uint32_t)]

I end up with an array of 20 uint32_t, or 80 bytes, which is what I would expect.

I then initialize the queue with:

_lwmsq_init(msgQ, 1, 4);

However, when I send this structure, with the LWMSGQ_SEND_BLOCK_ON_FULL, it doesn't block because apparently it's not full. As an experiment, I tried send a single uint32_t integer, but left the message size the same. Again, it did not block. Once I changed the message size to 1, it blocked. Although it only allows 1 message, apparently it's not "full" unless the size of the message is exact. How does one send a structure like this and have it block on full?

On a somewhat related note, if I send a message with the LWMSQ_SEND_BLOCK_ON_SEND flag, it does indeed block, but what unblocks the task? I was able to block one task, receive the structure message by the receiving task, but I could not send a structure back and unblock the requesting task.

Re: Lightweight message size

danielchen — Sun, 20 Jul 2014 07:24:49 GMT

Please refer to the macro in lwmsgq.h , task will be block when LWMSGQ_IS_FULL

/* Return whether the queue is full */

#define LWMSGQ_IS_FULL(q) \

(((LWMSGQ_STRUCT_PTR)(q))->CURRENT_SIZE >= ((LWMSGQ_STRUCT_PTR)(q))->MAX_SIZE)

Message queue is full if current_size >= max_size. max_size is the number of messages when you use _lwmsgq_init. Current_size will increase by 1 when enqueue and will decrease by 1 when dequeue.

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Lightweight message size

Re: Lightweight message size