api: Add explicit close methods to classes

This is needed for bindings to languages which perform implicit and lazy
object cleanups. The explicit close methods allow to release resources
when they are no longer required, permitting deterministic reuse. One
example is node-red-node-intel-gpio which will use the new calls on node
closing.

Fixes #1044.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

api/mraa/aio.hpp

@@ -75,8 +75,19 @@ class Aio
      * Aio destructor
      */
     ~Aio()
+    {
+        if (m_aio != NULL) {
+            mraa_aio_close(m_aio);
+        }
+    }
+    /**
+     * Closes AIO explicitly, prior to implicit closing on object destruction
+     */
+    void
+    close()
     {
         mraa_aio_close(m_aio);
+        m_aio = NULL;
     }
     /**
      * Read a value from the AIO pin. By default mraa will shift

api/mraa/gpio.hpp

@@ -143,8 +143,19 @@ class Gpio
      * the owner
      */
     ~Gpio()
+    {
+        if (m_gpio != NULL) {
+            mraa_gpio_close(m_gpio);
+        }
+    }
+    /**
+     * Closes Gpio explicitly, prior to implicit closing on object destruction
+     */
+    void
+    close()
     {
         mraa_gpio_close(m_gpio);
+        m_gpio = NULL;
     }
     /**
      * Set the edge mode for ISR

api/mraa/i2c.hpp

@@ -83,8 +83,20 @@ class I2c
      * slaves.
      */
     ~I2c()
+    {
+        if (m_i2c != NULL) {
+            mraa_i2c_stop(m_i2c);
+        }
+    }
+
+    /**
+     * Closes I2c explicitly, prior to implicit closing on object destruction
+     */
+    void
+    close()
     {
         mraa_i2c_stop(m_i2c);
+        m_i2c = NULL;
     }
 
     /**

api/mraa/iio.hpp

@@ -131,9 +131,20 @@ class Iio
      */
     ~Iio()
     {
-        mraa_iio_close(m_iio);
+        if (m_iio != NULL) {
+            mraa_iio_close(m_iio);
+        }
     }
 
+    /**
+     * Closes Iio explicitly, prior to implicit closing on object destruction
+     */
+    void
+    close()
+    {
+        mraa_iio_close(m_iio);
+        m_iio = NULL;
+    }
 
     /**
      * Get device name

api/mraa/led.hpp

@@ -89,8 +89,20 @@ class Led
      * LED object destructor
      */
     ~Led()
+    {
+        if (m_led != NULL) {
+            mraa_led_close(m_led);
+        }
+    }
+
+    /*
+     * Closes LED explicitly, prior to implicit closing on object destruction
+     */
+    void
+    close()
     {
         mraa_led_close(m_led);
+        m_led = NULL;
     }
 
     /**

api/mraa/pwm.hpp

@@ -86,8 +86,19 @@ class Pwm
      * Pwm destructor
      */
     ~Pwm()
+    {
+        if (m_pwm != NULL) {
+            mraa_pwm_close(m_pwm);
+        }
+    }
+    /*
+     * Closes Pwm explicitly, prior to implicit closing on object destruction
+     */
+    void
+    close()
     {
         mraa_pwm_close(m_pwm);
+        m_pwm = NULL;
     }
     /**
      * Set the output duty-cycle percentage, as a float

api/mraa/spi.hpp

@@ -105,8 +105,20 @@ class Spi
      * Closes spi bus
      */
     ~Spi()
+    {
+        if (m_spi != NULL) {
+            mraa_spi_stop(m_spi);
+        }
+    }
+
+    /**
+     * Closes Spi explicitly, prior to implicit closing on object destruction
+     */
+    void
+    close()
     {
         mraa_spi_stop(m_spi);
+        m_spi = NULL;
     }
 
     /**

api/mraa/uart.hpp

@@ -95,8 +95,20 @@ class Uart
      * Uart destructor
      */
     ~Uart()
+    {
+        if (m_uart != NULL) {
+            mraa_uart_stop(m_uart);
+        }
+    }
+
+    /*
+     * Closes Uart explicitly, prior to implicit closing on object destruction
+     */
+    void
+    close()
     {
         mraa_uart_stop(m_uart);
+        m_uart = NULL;
     }
 
     /**

api/mraa/uart_ow.hpp

@@ -95,8 +95,20 @@ class UartOW
      * Uart destructor
      */
     ~UartOW()
+    {
+        if (m_uart != NULL) {
+            mraa_uart_ow_stop(m_uart);
+        }
+    }
+
+    /*
+     * Closes UartOW explicitly, prior to implicit closing on object destruction
+     */
+    void
+    close()
     {
         mraa_uart_ow_stop(m_uart);
+        m_uart = NULL;
     }
 
     /**