aio: Change mraa_aio_read to use int and return -1

This commit changes also the _replace function and adds exceptions to the C++
API for errors in AIO read

Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>

api/mraa/aio.h

@@ -59,19 +59,20 @@ typedef struct _aio* mraa_aio_context;
 mraa_aio_context mraa_aio_init(unsigned int pin);
 
 /**
- * Read the input voltage. By default mraa will shift
- * the raw value up or down to a 10 bit value.
+ * Read the input voltage. By default mraa will shift the raw value up or down
+ * to a 10 bit value.
  *
  * @param dev The AIO context
- * @returns The current input voltage.
+ * @returns The current input voltage or -1 for error
  */
-unsigned int mraa_aio_read(mraa_aio_context dev);
+int mraa_aio_read(mraa_aio_context dev);
 
 /**
  * Read the input voltage and return it as a normalized float (0.0f-1.0f).
  *
  * @param dev The AIO context
- * @returns The current input voltage as a normalized float (0.0f-1.0f)
+ * @returns The current input voltage as a normalized float (0.0f-1.0f), error
+ * will be signaled by -1.0f
  */
 float mraa_aio_read_float(mraa_aio_context dev);
 

api/mraa/aio.hpp

@@ -65,22 +65,32 @@ class Aio
      * Read a value from the AIO pin. By default mraa will shift
      * the raw value up or down to a 10 bit value.
      *
+     * @throws std::invalid_argument in case of error
      * @returns The current input voltage. By default, a 10bit value
      */
-    int
+    unsigned int
     read()
     {
-        return mraa_aio_read(m_aio);
+        int x = mraa_aio_read(m_aio);
+	if (x == -1) {
+            throw std::invalid_argument("Unknown error in Aio::read()");
+        }
+        return (unsigned int) x;
     }
     /**
      * Read a value from the AIO pin and return it as a normalized float.
      *
+     * @throws std::invalid_argument in case of error
      * @returns The current input voltage as a normalized float (0.0f-1.0f)
      */
     float
     readFloat()
     {
-        return mraa_aio_read_float(m_aio);
+        float x = mraa_aio_read_float(m_aio);
+	if (x == -1.0f) {
+            throw std::invalid_argument("Unknown error in Aio::readFloat()");
+        }
+        return x;
     }
     /**
      * Set the bit value which mraa will shift the raw reading

include/mraa_adv_func.h

@@ -75,7 +75,7 @@ typedef struct {
     mraa_result_t (*i2c_stop_replace) (mraa_i2c_context dev);
 
     mraa_result_t (*aio_init_internal_replace) (mraa_aio_context dev, int pin);
-    mraa_result_t (*aio_read_replace) (mraa_aio_context dev);
+    int (*aio_read_replace) (mraa_aio_context dev);
     mraa_result_t (*aio_get_valid_fp) (mraa_aio_context dev);
     mraa_result_t (*aio_init_pre) (unsigned int aio);
     mraa_result_t (*aio_init_post) (mraa_aio_context dev);

src/aio/aio.c

@@ -152,7 +152,7 @@ mraa_aio_init(unsigned int aio)
     return dev;
 }
 
-unsigned int
+int
 mraa_aio_read(mraa_aio_context dev)
 {
     if (IS_FUNC_DEFINED(dev, aio_read_replace)) {
@@ -165,7 +165,7 @@ mraa_aio_read(mraa_aio_context dev)
     if (dev->adc_in_fp == -1) {
         if (aio_get_valid_fp(dev) != MRAA_SUCCESS) {
             syslog(LOG_ERR, "aio: Failed to get to the device");
-            return 0;
+            return -1;
         }
     }
 
@@ -182,8 +182,10 @@ mraa_aio_read(mraa_aio_context dev)
     unsigned int analog_value = (unsigned int) strtoul(buffer, &end, 10);
     if (end == &buffer[0]) {
         syslog(LOG_ERR, "aio: Value is not a decimal number");
+        return -1;
     } else if (errno != 0) {
         syslog(LOG_ERR, "aio: Errno was set");
+        return -1;
     }
 
     if (dev->value_bit != raw_bits) {
@@ -205,7 +207,7 @@ mraa_aio_read_float(mraa_aio_context dev)
 {
     if (dev == NULL) {
         syslog(LOG_ERR, "aio: Device not valid");
-        return 0.0;
+        return -1.0;
     }
 
     float max_analog_value = (1 << dev->value_bit) - 1;

src/firmata/firmata_mraa.c

@@ -340,12 +340,12 @@ mraa_firmata_i2c_stop(mraa_i2c_context dev)
     return MRAA_SUCCESS;
 }
 
-static unsigned int
+static int
 mraa_firmata_aio_read(mraa_aio_context dev)
 {
     // careful, whilst you need to enable '0' for A0 you then need to read 14
     // in t_firmata because well that makes sense doesn't it...
-    return (unsigned int) firmata_dev->pins[dev->channel].value;
+    return (int) firmata_dev->pins[dev->channel].value;
 }
 
 static mraa_result_t