mqtt: fix ignoring args

examples/mqtt_client.rs

@@ -272,7 +272,11 @@ fn main() -> ! {
             .poll(|_client, topic, message, _properties| match topic {
                 topic => {
                     info!("On '{:?}', received: {:?}", topic, message);
-                    context.run_with_mqtt(topic.as_bytes(), &mut buf);
+                    // Why is topic a string while message is a slice?
+                    context.run_with_mqtt(topic,
+                                            core::str::from_utf8(message).unwrap(),
+                                            &mut buf)
+                            .unwrap();
                 },
             }).is_ok();
         

src/translation.rs

@@ -2,27 +2,46 @@ use scpi::prelude::*;
 use scpi::Context;
 use scpi::error::Result;
 
-use arrayvec::{ArrayVec};
+use core::concat;
+
+use arrayvec::{ArrayVec, ArrayString};
 
 pub trait MqttScpiTranslator {
-    fn run_with_mqtt<FMT: Formatter>(&mut self, s: &[u8], response: &mut FMT) -> Result<()>;
+    // Convert an MQTT publish message into SCPI compatible command
+    // The argument part/ MQTT message must follow SCPI standard for parameter formatting
+    fn run_with_mqtt<FMT: Formatter>(&mut self, topic: &str, args: &str, response: &mut FMT) -> Result<()>;
 }
 
 impl<'a, T: Device> MqttScpiTranslator for Context<'a, T> {
-    fn run_with_mqtt<FMT>(&mut self, s: &[u8], response: &mut FMT) -> Result<()>
+    fn run_with_mqtt<FMT>(&mut self, topic: &str, args: &str, response: &mut FMT) -> Result<()>
     where
         FMT: Formatter,
     {
-        let mut array_vec = ArrayVec::<[u8; 1024]>::new();
-        for i in s.into_iter() {
-            if *i == b'/' {
-                array_vec.try_push(b'/')
+        // Create a fixed-size buffer to handle slice operation
+        let mut buffer = ArrayVec::<[u8; 1024]>::new();
+
+        // Copy MQTT topic, convert it into SCPI header format
+        for i in topic.chars() {
+            if i == '/' {
+                // The topic separator is colon(':') in SCPI, and slash('/') in MQTT
+                buffer.try_push(b':')
                             .map_err(|_| ErrorCode::OutOfMemory)?;
             } else {
-                array_vec.try_push(*i)
+                buffer.try_push(i as u8)
                             .map_err(|_| ErrorCode::OutOfMemory)?;
             }
         }
-        self.run(array_vec.as_slice(), response)
+
+        // Place a space bar between header and parameter
+        buffer.try_push(b' ')
+                .map_err(|_| ErrorCode::OutOfMemory)?;
+
+        // Copy the arguments into the buffer
+        for i in args.chars() {
+            buffer.try_push(i as u8)
+                    .map_err(|_| ErrorCode::OutOfMemory)?;
+        }
+
+        self.run(buffer.as_slice(), response)
     }
 }