#209 Set Log callback. Add Paho C logging to Rust logs

src/async_client.rs

@@ -70,7 +70,7 @@ use std::{
     ptr, slice, str,
     sync::{
         atomic::{AtomicU32, Ordering},
-        Arc, Mutex,
+        Arc, Mutex, Once,
     },
     time::Duration,
 };
@@ -135,6 +135,9 @@ struct CallbackContext {
     on_message_arrived: Option<Box<MessageArrivedCallback>>,
 }
 
+// Runs code to initialize the underlying C library
+static C_LIB_INIT: Once = Once::new();
+
 impl AsyncClient {
     /// Creates a new MQTT client which can connect to an MQTT broker.
     ///
@@ -146,6 +149,18 @@ impl AsyncClient {
     where
         T: Into<CreateOptions>,
     {
+        // Do any initialization of the C lib
+        C_LIB_INIT.call_once(|| {
+            if let Some(lvl) = crate::paho_c_trace_level() {
+                debug!("Setting Paho C log level to {}", lvl);
+                unsafe {
+                    ffi::MQTTAsync_setTraceCallback(Some(Self::on_trace));
+                    ffi::MQTTAsync_setTraceLevel(lvl);
+                }
+            }
+        });
+
+        // Create the client
         let mut opts = opts.into();
         debug!("Create options: {:?}", opts);
 
@@ -230,6 +245,41 @@ impl AsyncClient {
         self.inner.handle
     }
 
+    // Low-level callback from the C library for log/trace messages.
+    // We send the
+    unsafe extern "C" fn on_trace(lvl: ffi::MQTTASYNC_TRACE_LEVELS, msg: *mut c_char) {
+        if msg.is_null() {
+            return;
+        }
+
+        let cmsg = CStr::from_ptr(msg);
+        let msg = match cmsg.to_str() {
+            Ok(s) => s,
+            Err(_) => return,
+        };
+
+        let lvl = match lvl {
+            ffi::MQTTASYNC_TRACE_LEVELS_MQTTASYNC_TRACE_FATAL |
+            ffi::MQTTASYNC_TRACE_LEVELS_MQTTASYNC_TRACE_SEVERE =>
+                log::Level::Error,
+
+            ffi::MQTTASYNC_TRACE_LEVELS_MQTTASYNC_TRACE_ERROR =>
+                log::Level::Warn,
+
+            ffi::MQTTASYNC_TRACE_LEVELS_MQTTASYNC_TRACE_PROTOCOL =>
+                log::Level::Info,
+
+            ffi::MQTTASYNC_TRACE_LEVELS_MQTTASYNC_TRACE_MINIMUM |
+            ffi::MQTTASYNC_TRACE_LEVELS_MQTTASYNC_TRACE_MEDIUM =>
+                log::Level::Debug,
+
+            ffi::MQTTASYNC_TRACE_LEVELS_MQTTASYNC_TRACE_MAXIMUM | _ =>
+                log::Level::Trace,
+        };
+
+        log!(target: "paho_mqtt_c", lvl, "{}", msg);
+    }
+
     // Low-level callback from the C library when the client is connected.
     // We just pass the call on to the handler registered with the client, if any.
     unsafe extern "C" fn on_connected(context: *mut c_void, _cause: *mut c_char) {

src/lib.rs

@@ -145,6 +145,68 @@ pub fn from_c_bool(on: c_int) -> bool {
     on != 0
 }
 
+/// The log target (module) for the Paho C trace logs
+const PAHO_C_LOG_TARGET: &str = "paho_mqtt_c";
+
+/// Converts a Paho C trace level into a Rust log level.
+pub fn from_c_trace_level(level: ffi::MQTTASYNC_TRACE_LEVELS) -> log::Level {
+    match level {
+        ffi::MQTTASYNC_TRACE_LEVELS_MQTTASYNC_TRACE_FATAL |
+        ffi::MQTTASYNC_TRACE_LEVELS_MQTTASYNC_TRACE_SEVERE =>
+            log::Level::Error,
+
+        ffi::MQTTASYNC_TRACE_LEVELS_MQTTASYNC_TRACE_ERROR =>
+            log::Level::Warn,
+
+        ffi::MQTTASYNC_TRACE_LEVELS_MQTTASYNC_TRACE_PROTOCOL =>
+            log::Level::Info,
+
+        ffi::MQTTASYNC_TRACE_LEVELS_MQTTASYNC_TRACE_MINIMUM |
+        ffi::MQTTASYNC_TRACE_LEVELS_MQTTASYNC_TRACE_MEDIUM =>
+            log::Level::Debug,
+
+        ffi::MQTTASYNC_TRACE_LEVELS_MQTTASYNC_TRACE_MAXIMUM | _ =>
+            log::Level::Trace,
+    }
+}
+
+/// Converts a Rust log level filer into a Paho C trace level.
+/// This gives the most verbose C trace level for the log level.
+pub fn log_into_c_trace_level(level: log::LevelFilter) -> Option<ffi::MQTTASYNC_TRACE_LEVELS> {
+    use log::LevelFilter::*;
+    match level {
+        Off => None,
+        Error => Some(ffi::MQTTASYNC_TRACE_LEVELS_MQTTASYNC_TRACE_SEVERE),
+        Warn => Some(ffi::MQTTASYNC_TRACE_LEVELS_MQTTASYNC_TRACE_ERROR),
+        Info => Some(ffi::MQTTASYNC_TRACE_LEVELS_MQTTASYNC_TRACE_PROTOCOL),
+        Debug => Some(ffi::MQTTASYNC_TRACE_LEVELS_MQTTASYNC_TRACE_MEDIUM),
+        Trace => Some(ffi::MQTTASYNC_TRACE_LEVELS_MQTTASYNC_TRACE_MAXIMUM),
+    }
+}
+
+/// Gets the trace level, if any, to set the Paho C library
+pub fn paho_c_trace_level() -> Option<ffi::MQTTASYNC_TRACE_LEVELS> {
+    use log::Level::*;
+    if log_enabled!(target: PAHO_C_LOG_TARGET, Trace) {
+        Some(ffi::MQTTASYNC_TRACE_LEVELS_MQTTASYNC_TRACE_MAXIMUM)
+    }
+    else if log_enabled!(target: PAHO_C_LOG_TARGET, Debug) {
+        Some(ffi::MQTTASYNC_TRACE_LEVELS_MQTTASYNC_TRACE_MEDIUM)
+    }
+    else if log_enabled!(target: PAHO_C_LOG_TARGET, Info) {
+        Some(ffi::MQTTASYNC_TRACE_LEVELS_MQTTASYNC_TRACE_PROTOCOL)
+    }
+    else if log_enabled!(target: PAHO_C_LOG_TARGET, Warn) {
+        Some(ffi::MQTTASYNC_TRACE_LEVELS_MQTTASYNC_TRACE_ERROR)
+    }
+    else if log_enabled!(target: PAHO_C_LOG_TARGET, Error) {
+        Some(ffi::MQTTASYNC_TRACE_LEVELS_MQTTASYNC_TRACE_SEVERE)
+    }
+    else {
+        None
+    }
+}
+
 /////////////////////////////////////////////////////////////////////////////
 //                              Unit Tests
 /////////////////////////////////////////////////////////////////////////////