samples/legacy/cpp_synchronization/nanokernel/src/main.cpp

/*
 * Copyright (c) 2015-2016 Wind River Systems, Inc.
 *
 * SPDX-License-Identifier: Apache-2.0
 */

/**
 * @file C++ Synchronization demo.  Uses basic C++ functionality.
 */

#include <stdio.h>

/**
 * @class semaphore the basic pure virtual semaphore class
 */
class semaphore {
public:
	virtual int wait(void) = 0;
	virtual int wait(int timeout) = 0;
	virtual void give(void) = 0;
};

/* specify delay between greetings (in ms); compute equivalent in ticks */

#define SLEEPTIME  500
#define SLEEPTICKS (SLEEPTIME * sys_clock_ticks_per_sec / 1000)

/*
 * Nanokernel version of C++ synchronization demo has a task and a fiber that
 * utilize semaphores and timers to take turns printing a greeting message at
 * a controlled rate.
 */

#include <nanokernel.h>
#include <arch/cpu.h>

#define STACKSIZE 2000

char __stack fiber_stack[STACKSIZE];

/*
 * @class nano_semaphore
 * @brief nano semaphore
 *
 * Class derives from the pure virtual semaphore class and
 * implements it's methods for the nanokernel semaphore
 */
class nano_semaphore: public semaphore {
protected:
	struct nano_sem _sema_internal;
public:
	nano_semaphore();
	virtual ~nano_semaphore() {}
	virtual int wait(void);
	virtual int wait(int timeout);
	virtual void give(void);
};

/*
 * @brief nano_semaphore basic constructor
 */
nano_semaphore::nano_semaphore()
{
	printf("Create semaphore %p\n", this);
	nano_sem_init(&_sema_internal);
}

/*
 * @brief wait for a semaphore
 *
 * Test a semaphore to see if it has been signaled.  If the signal
 * count is greater than zero, it is decremented.
 *
 * @return 1 when semaphore is available
 */
int nano_semaphore::wait(void)
{
	nano_sem_take(&_sema_internal, TICKS_UNLIMITED);
	return 1;
}

/*
 * @brief wait for a semaphore within a specified timeout
 *
 * Test a semaphore to see if it has been signaled.  If the signal
 * count is greater than zero, it is decremented. The function
 * waits for timeout specified
 *
 * @param timeout the specified timeout in ticks
 *
 * @return 1 if semaphore is available, 0 if timed out
 */
int nano_semaphore::wait(int timeout)
{
	return nano_sem_take(&_sema_internal, timeout);
}

/**
 *
 * @brief Signal a semaphore
 *
 * This routine signals the specified semaphore.
 *
 * @return N/A
 */
void nano_semaphore::give(void)
{
	nano_sem_give(&_sema_internal);
}

/* task and fiber synchronization semaphores */
nano_semaphore nano_sem_fiber;
nano_semaphore nano_sem_task;

void fiber_entry(void)
{
	struct nano_timer timer;
	uint32_t data[2] = {0, 0};

	nano_timer_init(&timer, data);

	while (1) {
		/* wait for task to let us have a turn */
		nano_sem_fiber.wait();

		/* say "hello" */
		printf("%s: Hello World!\n", __FUNCTION__);

		/* wait a while, then let task have a turn */
		nano_fiber_timer_start(&timer, SLEEPTICKS);
		nano_fiber_timer_test(&timer, TICKS_UNLIMITED);
		nano_sem_task.give();
	}
}

void main(void)
{
	struct nano_timer timer;
	uint32_t data[2] = {0, 0};

	task_fiber_start(&fiber_stack[0], STACKSIZE,
			(nano_fiber_entry_t) fiber_entry, 0, 0, 7, 0);

	nano_timer_init(&timer, data);

	while (1) {
		/* say "hello" */
		printf("%s: Hello World!\n", __FUNCTION__);

		/* wait a while, then let fiber have a turn */
		nano_task_timer_start(&timer, SLEEPTICKS);
		nano_task_timer_test(&timer, TICKS_UNLIMITED);
		nano_sem_fiber.give();

		/* now wait for fiber to let us have a turn */
		nano_sem_task.wait();
	}
}