MQTT: take C part away from python code for readability.
authorEdouard Tisserant <edouard@beremiz.fr>
Mon, 22 Jul 2024 16:09:12 +0200
changeset 3995 84a668564748
parent 3994 c399fe412dbd
child 3996 4eb23bb4bc2f
MQTT: take C part away from python code for readability.

C lines change a bit because of unnecessary escaping for '\'.
mqtt/mqtt_client_gen.py
mqtt/mqtt_template.c
--- a/mqtt/mqtt_client_gen.py	Mon Jul 22 12:12:33 2024 +0200
+++ b/mqtt/mqtt_client_gen.py	Mon Jul 22 16:09:12 2024 +0200
@@ -9,6 +9,8 @@
 import wx
 import wx.dataview as dv
 
+import util.paths as paths
+
 # from perfect_hash import generate_code, IntSaltHash
 
 MQTT_IEC_types = dict(
@@ -299,363 +301,10 @@
                     writer.writerow([direction] + row)
 
     def GenerateC(self, path, locstr, config):
-        template = """/* code generated by beremiz MQTT extension */
-
-#include <stdint.h>
-#include <unistd.h>
-#include <pthread.h>
-#include <string.h>
-#include <stdio.h>
-
-#include "MQTTClient.h"
-#include "MQTTClientPersistence.h"
-
-#define _Log(level, ...)                                                                          \\
-    {{                                                                                            \\
-        char mstr[256];                                                                           \\
-        snprintf(mstr, 255, __VA_ARGS__);                                                         \\
-        LogMessage(level, mstr, strlen(mstr));                                                    \\
-        printf(__VA_ARGS__);                                                                      \\
-        fflush(stdout);                                                                           \\
-    }}
-
-#define LogInfo(...) _Log(LOG_INFO, __VA_ARGS__);
-#define LogError(...) _Log(LOG_CRITICAL, __VA_ARGS__);
-#define LogWarning(...) _Log(LOG_WARNING, __VA_ARGS__);
-
-void trace_callback(enum MQTTCLIENT_TRACE_LEVELS level, char* message)
-{{
-    LogInfo("Paho MQTT Trace : %d, %s\\n", level, message);
-}}
-
-#define CHANGED 1
-#define UNCHANGED 0
-
-#define DECL_VAR(iec_type, C_type, c_loc_name)                                                     \\
-static C_type PLC_##c_loc_name##_buf = 0;                                                          \\
-static C_type MQTT_##c_loc_name##_buf = 0;                                                         \\
-static int MQTT_##c_loc_name##_state = UNCHANGED;  /* systematically published at init */          \\
-C_type *c_loc_name = &PLC_##c_loc_name##_buf;
-
-{decl}
-
-static MQTTClient client;
-#ifdef USE_MQTT_5
-static MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer5;
-#else
-static MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
-#endif
-
-/* condition to quit publish thread */
-static int MQTT_stop_thread = 0;
-
-/* condition to wakeup publish thread */
-static int MQTT_any_pub_var_changed = 0;
-
-/* mutex to keep PLC data consistent, and protect MQTT_any_pub_var_changed */
-static pthread_mutex_t MQTT_mutex;
-
-/* wakeup publish thread when PLC changed published variable */
-static pthread_cond_t MQTT_new_data = PTHREAD_COND_INITIALIZER;
-
-/* publish thread */
-static pthread_t publishThread;
-
-#define INIT_TOPIC(topic, iec_type, c_loc_name)                                                    \\
-{{#topic, &MQTT_##c_loc_name##_buf, &MQTT_##c_loc_name##_state, iec_type##_ENUM}},
-
-static struct {{
-    const char *topic; //null terminated topic string
-    void *mqtt_pdata; // pointer to data from/for MQTT stack
-    int *mqtt_pchanged; // pointer to changed flag
-    __IEC_types_enum vartype;
-}} topics [] = {{
-{topics}
-}};
-
-static int _connect_mqtt(void)
-{{
-    int rc;
-
-#ifdef USE_MQTT_5
-    MQTTProperties props = MQTTProperties_initializer;
-    MQTTProperties willProps = MQTTProperties_initializer;
-    MQTTResponse response = MQTTResponse_initializer;
-
-    response = MQTTClient_connect5(client, &conn_opts, &props, &willProps);
-    rc = response.reasonCode;
-    MQTTResponse_free(response);
-#else
-    rc = MQTTClient_connect(client, &conn_opts);
-#endif
-
-    return rc;
-}}
-
-void __cleanup_{locstr}(void)
-{{
-    int rc;
-
-    /* stop publish thread */
-    MQTT_stop_thread = 1;
-    if (pthread_mutex_trylock(&MQTT_mutex) == 0){{
-        /* unblock publish thread so that it can stop normally */
-        pthread_cond_signal(&MQTT_new_data);
-        pthread_mutex_unlock(&MQTT_mutex);
-    }}
-    pthread_join(publishThread, NULL);
-
-#ifdef USE_MQTT_5
-    if (rc = MQTTClient_disconnect5(client, 5000, MQTTREASONCODE_SUCCESS, NULL) != MQTTCLIENT_SUCCESS)
-#else
-    if (rc = MQTTClient_disconnect(client, 5000) != MQTTCLIENT_SUCCESS)
-#endif
-    {{
-        LogError("MQTT Failed to disconnect, return code %d\\n", rc);
-    }}
-    MQTTClient_destroy(&client);
-}}
-
-void connectionLost(void* context, char* reason)
-{{
-    int rc;
-    LogWarning("ConnectionLost, reconnecting\\n");
-    // rc = _connect_mqtt();
-
-    // if (rc != MQTTCLIENT_SUCCESS) {{
-    //     LogError("MQTT reconnect Failed, waiting 5 seconds, return code %d\\n", rc);
-    //     /* wait if error */
-    //     sleep(5);
-    // }}
-}}
-
-int messageArrived(void *context, char *topicName, int topicLen, MQTTClient_message *message)
-{{
-    int low = 0;
-    int size = sizeof(topics) / sizeof(topics[0]);
-    int high = size - 1;
-    int mid;
-
-    // bisect topic among subscribed topics
-    while (low <= high) {{
-        int res;
-        mid = low + (high - low) / 2;
-        res = strncmp(topics[mid].topic, topicName, topicLen);
-
-        // Check if key is present at mid
-        if (res == 0)
-            goto found;
-
-        // If key greater, ignore left half
-        if (res < 0)
-            low = mid + 1;
-
-        // If key is smaller, ignore right half
-        else
-            high = mid - 1;
-    }}
-    // If we reach here, then the element was not present
-    LogWarning("MQTT unknown topic: %s", topicName);
-    goto exit;
-
-found:
-    if(__get_type_enum_size(topics[mid].vartype) == message->payloadlen){{
-        memcpy(topics[mid].mqtt_pdata, (char*)message->payload, message->payloadlen);
-        *topics[mid].mqtt_pchanged = 1;
-    }} else {{
-        LogWarning("MQTT wrong payload size for topic: %s. Should be %d, but got %d.", 
-            topicName, __get_type_enum_size(topics[mid].vartype), message->payloadlen);
-    }}
-exit:
-    MQTTClient_freeMessage(&message);
-    MQTTClient_free(topicName);
-    return 1;
-}}
-
-#define INIT_NoAuth()                                                                             \\
-    LogInfo("MQTT Init no auth\\n");
-
-#define INIT_x509(PrivateKey, Certificate)                                                        \\
-    LogInfo("MQTT Init x509 %s,%s\\n", PrivateKey, Certificate);
-    /* TODO */
-
-#define INIT_UserPassword(User, Password)                                                         \\
-    LogInfo("MQTT Init UserPassword %s,%s\\n", User, Password);                                   \\
-    conn_opts.username = User;                                                                    \\
-    conn_opts.password = Password;
-
-#ifdef USE_MQTT_5
-#define _SUBSCRIBE(Topic, QoS)                                                                    \\
-        MQTTResponse response = MQTTClient_subscribe5(client, #Topic, QoS, NULL, NULL);           \\
-        /* when using MQTT5 responce code is 1 for some reason even if no error */                \\
-        rc = response.reasonCode == 1 ? MQTTCLIENT_SUCCESS : response.reasonCode;                 \\
-        MQTTResponse_free(response);
-#else
-#define _SUBSCRIBE(Topic, QoS)                                                                    \\
-        rc = MQTTClient_subscribe(client, #Topic, QoS);
-#endif
-
-#define INIT_SUBSCRIPTION(Topic, QoS)                                                             \\
-    {{                                                                                            \\
-        int rc;                                                                                   \\
-        _SUBSCRIBE(Topic, QoS)                                                                  \\
-        if (rc != MQTTCLIENT_SUCCESS)                                                             \\
-        {{                                                                                        \\
-            LogError("MQTT client failed to subscribe to '%s', return code %d\\n", #Topic, rc);   \\
-        }}                                                                                        \\
-    }}
-
-
-#ifdef USE_MQTT_5
-#define _PUBLISH(Topic, QoS, C_type, c_loc_name, Retained)                                        \\
-        MQTTResponse response = MQTTClient_publish5(client, #Topic, sizeof(C_type),               \\
-            &MQTT_##c_loc_name##_buf, QoS, Retained, NULL, NULL);                                  \\
-        rc = response.reasonCode;                                                                 \\
-        MQTTResponse_free(response);
-#else
-#define _PUBLISH(Topic, QoS, C_type, c_loc_name, Retained)                                        \\
-        rc = MQTTClient_publish(client, #Topic, sizeof(C_type),                                   \\
-            &PLC_##c_loc_name##_buf, QoS, Retained, NULL);
-#endif
-
-#define INIT_PUBLICATION(Topic, QoS, C_type, c_loc_name, Retained)                                \\
-    {{                                                                                            \\
-        int rc;                                                                                   \\
-        _PUBLISH(Topic, QoS, C_type, c_loc_name, Retained)                                        \\
-        if (rc != MQTTCLIENT_SUCCESS)                                                             \\
-        {{                                                                                        \\
-            LogError("MQTT client failed to init publication of '%s', return code %d\\n", #Topic, rc);\\
-            /* TODO update status variable accordingly */                                         \\
-        }}                                                                                        \\
-    }}
-
-#define PUBLISH_CHANGE(Topic, QoS, C_type, c_loc_name, Retained)                                  \\
-    if(MQTT_##c_loc_name##_state == CHANGED)                                                      \\
-    {{                                                                                            \\
-        int rc;                                                                                   \\
-        _PUBLISH(Topic, QoS, C_type, c_loc_name, Retained)                                        \\
-        if (rc != MQTTCLIENT_SUCCESS)                                                             \\
-        {{                                                                                        \\
-            LogError("MQTT client failed to publish '%s', return code %d\\n", #Topic, rc);        \\
-            /* TODO update status variable accordingly */                                         \\
-        }} else {{                                                                                \\
-            MQTT_##c_loc_name##_state = UNCHANGED;                                                \\
-        }}                                                                                        \\
-    }}
-
-static void *__publish_thread(void *_unused) {{
-    int rc = 0;
-    while((rc = pthread_mutex_lock(&MQTT_mutex)) == 0 && !MQTT_stop_thread){{
-        pthread_cond_wait(&MQTT_new_data, &MQTT_mutex);
-        if(MQTT_any_pub_var_changed && MQTTClient_isConnected(client)){{
-
-            /* publish changes, and reset variable's state to UNCHANGED */
-{publish_changes}
-            MQTT_any_pub_var_changed = 0;
-        }}
-
-        pthread_mutex_unlock(&MQTT_mutex);
-
-        if(MQTT_stop_thread) break;
-    }}
-
-    if(!MQTT_stop_thread){{
-        /* if thread exits outside of normal shutdown, report error*/
-        LogError("MQTT client thread exited unexpectedly, return code %d\\n", rc);
-    }}
-}}
-    
-int __init_{locstr}(int argc,char **argv)
-{{
-    char *uri = "{uri}";
-    char *clientID = "{clientID}";
-    int rc;
-
-    MQTTClient_createOptions createOpts = MQTTClient_createOptions_initializer;
-
-#ifdef USE_MQTT_5
-    conn_opts.MQTTVersion = MQTTVERSION_5;
-    conn_opts.cleanstart = 1;
-
-    createOpts.MQTTVersion = MQTTVERSION_5;
-#else
-    conn_opts.cleansession = 1;
-#endif
-
-    MQTTClient_setTraceCallback(trace_callback);
-    MQTTClient_setTraceLevel(MQTTCLIENT_TRACE_ERROR);
-
-
-    rc = MQTTClient_createWithOptions(
-        &client, uri, clientID, MQTTCLIENT_PERSISTENCE_NONE, NULL, &createOpts);
-    if (rc != MQTTCLIENT_SUCCESS)
-    {{
-        LogError("MQTT Failed to create client, return code %d\\n", rc);
-        return rc;
-    }}
-
-    rc = MQTTClient_setCallbacks(client, NULL, connectionLost, messageArrived, NULL);
-    if (rc != MQTTCLIENT_SUCCESS)
-    {{
-        LogError("MQTT Failed to set callbacks, return code %d\\n", rc);
-        return rc;
-    }}
-
-    rc = _connect_mqtt();
-
-    if (rc != MQTTCLIENT_SUCCESS) {{
-        LogError("MQTT Connect Failed, return code %d\\n", rc);
-        return rc;
-    }}
-
-{init}
-
-    /* TODO start publish thread */
-    rc = pthread_create(&publishThread, NULL, &__publish_thread, NULL);
-
-    return 0;
-}}
-
-#define READ_VALUE(c_loc_name, C_type) \\
-    if(MQTT_##c_loc_name##_state == CHANGED){{ \\
-        /* TODO care about endianess */ \\
-        PLC_##c_loc_name##_buf = MQTT_##c_loc_name##_buf; \\
-        MQTT_##c_loc_name##_state = UNCHANGED; \\
-    }}
-
-void __retrieve_{locstr}(void)
-{{
-    if (pthread_mutex_trylock(&MQTT_mutex) == 0){{
-{retrieve}
-        pthread_mutex_unlock(&MQTT_mutex);
-    }}
-}}
-
-#define WRITE_VALUE(c_loc_name, C_type) \\
-    /* TODO care about endianess */ \\
-    if(MQTT_##c_loc_name##_buf != PLC_##c_loc_name##_buf){{ \\
-        MQTT_##c_loc_name##_buf = PLC_##c_loc_name##_buf; \\
-        MQTT_##c_loc_name##_state = CHANGED; \\
-        MQTT_any_pub_var_changed = 1; \\
-    }}
-
-void __publish_{locstr}(void)
-{{
-    if (pthread_mutex_trylock(&MQTT_mutex) == 0){{
-        MQTT_any_pub_var_changed = 0;
-        /* copy PLC_* variables to MQTT_*, and mark those who changed */
-{publish}
-        /* if any change detcted, unblock publish thread */
-        if(MQTT_any_pub_var_changed){{
-            pthread_cond_signal(&MQTT_new_data);
-        }}
-        pthread_mutex_unlock(&MQTT_mutex);
-    }} else {{
-        /* TODO if couldn't lock mutex set status variable accordingly */ 
-    }}
-}}
-
-"""
+        c_template_filepath = paths.AbsNeighbourFile(__file__, "mqtt_template.c")
+        c_template_file = open(c_template_filepath , 'rb')
+        c_template = c_template_file.read()
+        c_template_file.close()
 
         formatdict = dict(
             locstr          = locstr,
@@ -716,7 +365,7 @@
             formatdict["retrieve"] += """
         READ_VALUE({c_loc_name}, {C_type})""".format(**locals())
 
-        Ccode = template.format(**formatdict)
+        Ccode = c_template.format(**formatdict)
 
         return Ccode
 
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mqtt/mqtt_template.c	Mon Jul 22 16:09:12 2024 +0200
@@ -0,0 +1,343 @@
+/* code generated by beremiz MQTT extension */
+
+#include <stdint.h>
+#include <unistd.h>
+#include <pthread.h>
+#include <string.h>
+#include <stdio.h>
+
+#include "MQTTClient.h"
+#include "MQTTClientPersistence.h"
+
+#define _Log(level, ...)                                                                          \
+    {{                                                                                            \
+        /* char mstr[256];                          */                                                 \
+        /* snprintf(mstr, 255, __VA_ARGS__);        */                                                 \
+        /* LogMessage(level, mstr, strlen(mstr));   */                                                 \
+        printf(__VA_ARGS__);                                                                      \
+        fflush(stdout);                                                                           \
+    }}
+
+#define LogInfo(...) _Log(LOG_INFO, __VA_ARGS__);
+#define LogError(...) _Log(LOG_CRITICAL, __VA_ARGS__);
+#define LogWarning(...) _Log(LOG_WARNING, __VA_ARGS__);
+
+void trace_callback(enum MQTTCLIENT_TRACE_LEVELS level, char* message)
+{{
+    LogInfo("Paho MQTT Trace : %d, %s\n", level, message);
+}}
+
+#define CHANGED 1
+#define UNCHANGED 0
+
+#define DECL_VAR(iec_type, C_type, c_loc_name)                                                     \
+static C_type PLC_##c_loc_name##_buf = 0;                                                          \
+static C_type MQTT_##c_loc_name##_buf = 0;                                                         \
+static int MQTT_##c_loc_name##_state = UNCHANGED;  /* systematically published at init */          \
+C_type *c_loc_name = &PLC_##c_loc_name##_buf;
+
+{decl}
+
+static MQTTClient client;
+#ifdef USE_MQTT_5
+static MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer5;
+#else
+static MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
+#endif
+
+/* condition to quit publish thread */
+static int MQTT_stop_thread = 0;
+
+/* condition to wakeup publish thread */
+static int MQTT_any_pub_var_changed = 0;
+
+/* mutex to keep PLC data consistent, and protect MQTT_any_pub_var_changed */
+static pthread_mutex_t MQTT_mutex;
+
+/* wakeup publish thread when PLC changed published variable */
+static pthread_cond_t MQTT_new_data = PTHREAD_COND_INITIALIZER;
+
+/* publish thread */
+static pthread_t publishThread;
+
+#define INIT_TOPIC(topic, iec_type, c_loc_name)                                                    \
+{{#topic, &MQTT_##c_loc_name##_buf, &MQTT_##c_loc_name##_state, iec_type##_ENUM}},
+
+static struct {{
+    const char *topic; //null terminated topic string
+    void *mqtt_pdata; // pointer to data from/for MQTT stack
+    int *mqtt_pchanged; // pointer to changed flag
+    __IEC_types_enum vartype;
+}} topics [] = {{
+{topics}
+}};
+
+static int _connect_mqtt(void)
+{{
+    int rc;
+
+#ifdef USE_MQTT_5
+    MQTTProperties props = MQTTProperties_initializer;
+    MQTTProperties willProps = MQTTProperties_initializer;
+    MQTTResponse response = MQTTResponse_initializer;
+
+    response = MQTTClient_connect5(client, &conn_opts, &props, &willProps);
+    rc = response.reasonCode;
+    MQTTResponse_free(response);
+#else
+    rc = MQTTClient_connect(client, &conn_opts);
+#endif
+
+    return rc;
+}}
+
+void __cleanup_{locstr}(void)
+{{
+    int rc;
+
+    /* stop publish thread */
+    MQTT_stop_thread = 1;
+    if (pthread_mutex_trylock(&MQTT_mutex) == 0){{
+        /* unblock publish thread so that it can stop normally */
+        pthread_cond_signal(&MQTT_new_data);
+        pthread_mutex_unlock(&MQTT_mutex);
+    }}
+    pthread_join(publishThread, NULL);
+
+#ifdef USE_MQTT_5
+    if (rc = MQTTClient_disconnect5(client, 5000, MQTTREASONCODE_SUCCESS, NULL) != MQTTCLIENT_SUCCESS)
+#else
+    if (rc = MQTTClient_disconnect(client, 5000) != MQTTCLIENT_SUCCESS)
+#endif
+    {{
+        LogError("MQTT Failed to disconnect, return code %d\n", rc);
+    }}
+    MQTTClient_destroy(&client);
+}}
+
+int messageArrived(void *context, char *topicName, int topicLen, MQTTClient_message *message)
+{{
+    int low = 0;
+    int size = sizeof(topics) / sizeof(topics[0]);
+    int high = size - 1;
+    int mid;
+
+    // bisect topic among subscribed topics
+    while (low <= high) {{
+        int res;
+        mid = low + (high - low) / 2;
+        res = strncmp(topics[mid].topic, topicName, topicLen);
+
+        // Check if key is present at mid
+        if (res == 0)
+            goto found;
+
+        // If key greater, ignore left half
+        if (res < 0)
+            low = mid + 1;
+
+        // If key is smaller, ignore right half
+        else
+            high = mid - 1;
+    }}
+    // If we reach here, then the element was not present
+    LogWarning("MQTT unknown topic: %s", topicName);
+    goto exit;
+
+found:
+    if(__get_type_enum_size(topics[mid].vartype) == message->payloadlen){{
+        memcpy(topics[mid].mqtt_pdata, (char*)message->payload, message->payloadlen);
+        *topics[mid].mqtt_pchanged = 1;
+    }} else {{
+        LogWarning("MQTT wrong payload size for topic: %s. Should be %d, but got %d.", 
+            topicName, __get_type_enum_size(topics[mid].vartype), message->payloadlen);
+    }}
+exit:
+    MQTTClient_freeMessage(&message);
+    MQTTClient_free(topicName);
+    return 1;
+}}
+
+#define INIT_NoAuth()                                                                             \
+    LogInfo("MQTT Init no auth\n");
+
+#define INIT_x509(PrivateKey, Certificate)                                                        \
+    LogInfo("MQTT Init x509 %s,%s\n", PrivateKey, Certificate);
+    /* TODO */
+
+#define INIT_UserPassword(User, Password)                                                         \
+    LogInfo("MQTT Init UserPassword %s,%s\n", User, Password);                                   \
+    conn_opts.username = User;                                                                    \
+    conn_opts.password = Password;
+
+#ifdef USE_MQTT_5
+#define _SUBSCRIBE(Topic, QoS)                                                                    \
+        MQTTResponse response = MQTTClient_subscribe5(client, #Topic, QoS, NULL, NULL);           \
+        /* when using MQTT5 responce code is 1 for some reason even if no error */                \
+        rc = response.reasonCode == 1 ? MQTTCLIENT_SUCCESS : response.reasonCode;                 \
+        MQTTResponse_free(response);
+#else
+#define _SUBSCRIBE(Topic, QoS)                                                                    \
+        rc = MQTTClient_subscribe(client, #Topic, QoS);
+#endif
+
+#define INIT_SUBSCRIPTION(Topic, QoS)                                                             \
+    {{                                                                                            \
+        int rc;                                                                                   \
+        _SUBSCRIBE(Topic, QoS)                                                                  \
+        if (rc != MQTTCLIENT_SUCCESS)                                                             \
+        {{                                                                                        \
+            LogError("MQTT client failed to subscribe to '%s', return code %d\n", #Topic, rc);   \
+        }}                                                                                        \
+    }}
+
+
+#ifdef USE_MQTT_5
+#define _PUBLISH(Topic, QoS, C_type, c_loc_name, Retained)                                        \
+        MQTTResponse response = MQTTClient_publish5(client, #Topic, sizeof(C_type),               \
+            &MQTT_##c_loc_name##_buf, QoS, Retained, NULL, NULL);                                  \
+        rc = response.reasonCode;                                                                 \
+        MQTTResponse_free(response);
+#else
+#define _PUBLISH(Topic, QoS, C_type, c_loc_name, Retained)                                        \
+        rc = MQTTClient_publish(client, #Topic, sizeof(C_type),                                   \
+            &PLC_##c_loc_name##_buf, QoS, Retained, NULL);
+#endif
+
+#define INIT_PUBLICATION(Topic, QoS, C_type, c_loc_name, Retained)                                \
+    {{                                                                                            \
+        int rc;                                                                                   \
+        _PUBLISH(Topic, QoS, C_type, c_loc_name, Retained)                                        \
+        if (rc != MQTTCLIENT_SUCCESS)                                                             \
+        {{                                                                                        \
+            LogError("MQTT client failed to init publication of '%s', return code %d\n", #Topic, rc);\
+            /* TODO update status variable accordingly */                                         \
+        }}                                                                                        \
+    }}
+
+#define PUBLISH_CHANGE(Topic, QoS, C_type, c_loc_name, Retained)                                  \
+    if(MQTT_##c_loc_name##_state == CHANGED)                                                      \
+    {{                                                                                            \
+        int rc;                                                                                   \
+        _PUBLISH(Topic, QoS, C_type, c_loc_name, Retained)                                        \
+        if (rc != MQTTCLIENT_SUCCESS)                                                             \
+        {{                                                                                        \
+            LogError("MQTT client failed to publish '%s', return code %d\n", #Topic, rc);        \
+            /* TODO update status variable accordingly */                                         \
+        }} else {{                                                                                \
+            MQTT_##c_loc_name##_state = UNCHANGED;                                                \
+        }}                                                                                        \
+    }}
+
+static void *__publish_thread(void *_unused) {{
+    int rc = 0;
+    while((rc = pthread_mutex_lock(&MQTT_mutex)) == 0 && !MQTT_stop_thread){{
+        pthread_cond_wait(&MQTT_new_data, &MQTT_mutex);
+        if(MQTT_any_pub_var_changed && MQTTClient_isConnected(client)){{
+
+            /* publish changes, and reset variable's state to UNCHANGED */
+{publish_changes}
+            MQTT_any_pub_var_changed = 0;
+        }}
+
+        pthread_mutex_unlock(&MQTT_mutex);
+
+        if(MQTT_stop_thread) break;
+    }}
+
+    if(!MQTT_stop_thread){{
+        /* if thread exits outside of normal shutdown, report error*/
+        LogError("MQTT client thread exited unexpectedly, return code %d\n", rc);
+    }}
+}}
+    
+int __init_{locstr}(int argc,char **argv)
+{{
+    char *uri = "{uri}";
+    char *clientID = "{clientID}";
+    int rc;
+
+    MQTTClient_createOptions createOpts = MQTTClient_createOptions_initializer;
+
+#ifdef USE_MQTT_5
+    conn_opts.MQTTVersion = MQTTVERSION_5;
+    conn_opts.cleanstart = 1;
+
+    createOpts.MQTTVersion = MQTTVERSION_5;
+#else
+    conn_opts.cleansession = 1;
+#endif
+
+    MQTTClient_setTraceCallback(trace_callback);
+    MQTTClient_setTraceLevel(MQTTCLIENT_TRACE_ERROR);
+
+
+    rc = MQTTClient_createWithOptions(
+        &client, uri, clientID, MQTTCLIENT_PERSISTENCE_NONE, NULL, &createOpts);
+    if (rc != MQTTCLIENT_SUCCESS)
+    {{
+        LogError("MQTT Failed to create client, return code %d\n", rc);
+        return rc;
+    }}
+
+    rc = MQTTClient_setCallbacks(client, NULL, NULL, messageArrived, NULL);
+    if (rc != MQTTCLIENT_SUCCESS)
+    {{
+        LogError("MQTT Failed to set callbacks, return code %d\n", rc);
+        return rc;
+    }}
+
+    rc = _connect_mqtt();
+
+    if (rc != MQTTCLIENT_SUCCESS) {{
+        LogError("MQTT Connect Failed, return code %d\n", rc);
+        return rc;
+    }}
+
+{init}
+
+    /* TODO start publish thread */
+    rc = pthread_create(&publishThread, NULL, &__publish_thread, NULL);
+
+    return 0;
+}}
+
+#define READ_VALUE(c_loc_name, C_type) \
+    if(MQTT_##c_loc_name##_state == CHANGED){{ \
+        /* TODO care about endianess */ \
+        PLC_##c_loc_name##_buf = MQTT_##c_loc_name##_buf; \
+        MQTT_##c_loc_name##_state = UNCHANGED; \
+    }}
+
+void __retrieve_{locstr}(void)
+{{
+    if (pthread_mutex_trylock(&MQTT_mutex) == 0){{
+{retrieve}
+        pthread_mutex_unlock(&MQTT_mutex);
+    }}
+}}
+
+#define WRITE_VALUE(c_loc_name, C_type) \
+    /* TODO care about endianess */ \
+    if(MQTT_##c_loc_name##_buf != PLC_##c_loc_name##_buf){{ \
+        MQTT_##c_loc_name##_buf = PLC_##c_loc_name##_buf; \
+        MQTT_##c_loc_name##_state = CHANGED; \
+        MQTT_any_pub_var_changed = 1; \
+    }}
+
+void __publish_{locstr}(void)
+{{
+    if (pthread_mutex_trylock(&MQTT_mutex) == 0){{
+        MQTT_any_pub_var_changed = 0;
+        /* copy PLC_* variables to MQTT_*, and mark those who changed */
+{publish}
+        /* if any change detcted, unblock publish thread */
+        if(MQTT_any_pub_var_changed){{
+            pthread_cond_signal(&MQTT_new_data);
+        }}
+        pthread_mutex_unlock(&MQTT_mutex);
+    }} else {{
+        /* TODO if couldn't lock mutex set status variable accordingly */ 
+    }}
+}}
+