Using a Stream
The following example demonstrates the procedure for utilizing a stream to transfer data between two independent tasks.
#include <stdio.h> #include <stdlib.h> #include <stdarg.h> #include "OS_API.h" HANDLE StreamHandle; void Printf(char *Message, ...) { va_list ap; BOOL PrevLockState; /* Disable interrupts */ PrevLockState = arLock(); /* Print string on the console or send it via RS-232 */ va_start(ap, Message); vprintf(Message, ap); va_end(ap); /* Restore interrupts */ arRestore(PrevLockState); } static ERROR SenderTask(PVOID Arg) { char Buffer[48]; SIZE NumberOfBytes; int RandomNumber; /* Sleep for specified amount of time */ osSleep(((TIME) Arg) * 100 * AR_TICKS_PER_SECOND / 1000); /* Initialize random number generator */ srand((unsigned) arGetTickCount()); /* Fill whole buffer with bytes representing task ID */ stMemSet(Buffer, (UINT8) ('0' + ((char) Arg)), sizeof(Buffer)); /* Infinite loop */ while(1) { /* Get a square of random number in range from 0 to 20 */ RandomNumber = rand() % 21; RandomNumber *= RandomNumber; /* Number of bytes to send */ NumberOfBytes = (SIZE) (1 + (RandomNumber * (sizeof(Buffer) - 1)) / 400); /* Print received bytes */ Printf("Task %i sends %i bytes\n", (int) Arg, NumberOfBytes); /* Store bytes in the stream */ osWrite(StreamHandle, Buffer, NumberOfBytes, NULL); /* Sleep for one second */ osSleep(AR_TICKS_PER_SECOND); } } static ERROR ReceiverTask(PVOID Arg) { char Buffer[17]; /* Infinite loop */ while(1) { /* Read continously 16 bytes from the stream */ osRead(StreamHandle, Buffer, 16, NULL); /* Store string termination symbol */ Buffer[16] = '\0'; /* Print received bytes */ Printf("Task %i receives %s\n", (int) Arg, Buffer); } } int main(void) { /* Initialization */ arInit(); stInit(); osInit(); /* Create stram */ StreamHandle = osCreateStream(NULL, OS_IPC_PROTECT_MUTEX | OS_IPC_WAIT_IF_EMPTY | OS_IPC_WAIT_IF_FULL | OS_IPC_DIRECT_READ_WRITE, 32); /* Create sender tasks */ osCreateTask(SenderTask, (PVOID) 1, 0, 0, FALSE); osCreateTask(SenderTask, (PVOID) 2, 0, 0, FALSE); osCreateTask(SenderTask, (PVOID) 3, 0, 0, FALSE); /* Create receiver tasks */ osCreateTask(ReceiverTask, (PVOID) 4, 0, 0, FALSE); osCreateTask(ReceiverTask, (PVOID) 5, 0, 0, FALSE); /* Start the operating system */ osStart(); /* Deinitialization */ osDeinit(); arDeinit(); return 0; }
The example result on the console should look as follows:
Task 1 sends 12 bytes Task 2 sends 2 bytes Task 3 sends 2 bytes Task 4 receives 1111111111112233 Task 1 sends 8 bytes Task 2 sends 20 bytes Task 5 receives 1111111122222222 Task 3 sends 43 bytes Task 4 receives 2222222222223333 Task 5 receives 3333333333333333 Task 4 receives 3333333333333333 Task 1 sends 1 bytes Task 2 sends 6 bytes Task 3 sends 1 bytes Task 1 sends 34 bytes Task 5 receives 3333333122222231 Task 4 receives 1111111111111111 Task 5 receives 1111111111111111 Task 2 sends 43 bytes Task 4 receives 1222222222222222 Task 5 receives 2222222222222222 Task 3 sends 2 bytes Task 1 sends 27 bytes Task 4 receives 2222222222223311 Task 5 receives 1111111111111111 Task 2 sends 1 bytes Task 3 sends 43 bytes Task 4 receives 1111111112333333 Task 5 receives 3333333333333333 Task 4 receives 3333333333333333 Task 1 sends 10 bytes Task 2 sends 3 bytes Task 5 receives 3333311111111112 Task 3 sends 31 bytes Task 4 receives 2233333333333333 Task 5 receives 3333333333333333 Task 1 sends 5 bytes Task 2 sends 20 bytes Task 4 receives 3111112222222222
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