dlt_client_main_loop running in an infinite loop restricts graceful exit of DLT Client code (#284)

Issue:
------
dlt_client_main_loop currently uses an infinite loop ("while (1)"). This
creates problems when a DLT client is running in a thread as part of a larger
application. Graceful exit (for example: during object destruction) is not
possible because a thread is running dlt_client_main_loop in the background.

It is also not possible to exit the client, if we want it to fetch only a
pre-decided number of messages.

Solution:
---------
Allow user to define a callback function to check whether the next message
should be fetched.

dlt-test-client.c has a new option to fetch a pre-decided number of messages,
after which the client will exit.

Signed-off-by: Sreeharsha Ramanavarapu <sreeharsha.r@gmail.com>

3 files changed, 42 insertions, 2 deletions

diff --git a/include/dlt/dlt_client.h b/include/dlt/dlt_client.h
index f649b83..77f0cee 100644
--- a/include/dlt/dlt_client.h
+++ b/include/dlt/dlt_client.h
@@ -75,6 +75,7 @@
 
 #   include "dlt_types.h"
 #   include "dlt_common.h"
+#include <stdbool.h>
 
 typedef enum
 {
@@ -104,6 +105,7 @@ extern "C" {
 #   endif
 
 void dlt_client_register_message_callback(int (*registerd_callback)(DltMessage *message, void *data));
+void dlt_client_register_fetch_next_message_callback(bool (*registerd_callback)(void *data));
 
 /**
  * Initialising dlt client structure with a specific port
diff --git a/src/lib/dlt_client.c b/src/lib/dlt_client.c
index 0702f5f..b81d61b 100644
--- a/src/lib/dlt_client.c
+++ b/src/lib/dlt_client.c
@@ -97,12 +97,18 @@
 #include "dlt_client_cfg.h"
 
 static int (*message_callback_function)(DltMessage *message, void *data) = NULL;
+static bool (*fetch_next_message_callback_function)(void *data) = NULL;
 
 void dlt_client_register_message_callback(int (*registerd_callback)(DltMessage *message, void *data))
 {
     message_callback_function = registerd_callback;
 }
 
+void dlt_client_register_fetch_next_message_callback(bool (*registerd_callback)(void *data))
+{
+    fetch_next_message_callback_function = registerd_callback;
+}
+
 DltReturnValue dlt_client_init_port(DltClient *client, int port, int verbose)
 {
     if (verbose && (port != DLT_DAEMON_TCP_PORT))
@@ -397,7 +403,8 @@ DltReturnValue dlt_client_main_loop(DltClient *client, void *data, int verbose)
     if (dlt_message_init(&msg, verbose) == DLT_RETURN_ERROR)
         return DLT_RETURN_ERROR;
 
-    while (1) {
+    bool fetch_next_message = true;
+    while (fetch_next_message) {
         /* wait for data from socket or serial connection */
         ret = dlt_receiver_receive(&(client->receiver));
 
@@ -440,6 +447,8 @@ DltReturnValue dlt_client_main_loop(DltClient *client, void *data, int verbose)
             dlt_message_free(&msg, verbose);
             return DLT_RETURN_ERROR;
         }
+        if (fetch_next_message_callback_function)
+          fetch_next_message = (*fetch_next_message_callback_function)(data);
     }
 
     if (dlt_message_free(&msg, verbose) == DLT_RETURN_ERROR)
diff --git a/src/tests/dlt-test-client.c b/src/tests/dlt-test-client.c
index edac717..5273aa2 100644
--- a/src/tests/dlt-test-client.c
+++ b/src/tests/dlt-test-client.c
@@ -70,6 +70,8 @@
 #include <stdlib.h>     /* for atoi() */
 #include <string.h>     /* for strcmp() */
 #include <sys/uio.h>    /* for writev() */
+#include <stdbool.h>
+#include <limits.h>
 
 #include "dlt_client.h"
 #include "dlt_protocol.h"
@@ -84,6 +86,7 @@ static int g_testsFailed = 0;
 DltClient g_dltclient;
 /* Function prototypes */
 int dlt_testclient_message_callback(DltMessage *message, void *data);
+bool dlt_testclient_fetch_next_message_callback(void *data);
 
 typedef struct
 {
@@ -114,6 +117,7 @@ typedef struct
     int tests_failed;
 
     int sock;
+    int max_messages;
 } DltTestclientData;
 
 /**
@@ -140,6 +144,7 @@ void usage()
     printf("  -e ecuid      Set ECU ID (Default: ECU1)\n");
     printf("  -o filename   Output messages in new DLT file\n");
     printf("  -f filename   Enable filtering of messages\n");
+    printf("  -z max msgs   Print z DLT messages\n");
 }
 
 /**
@@ -165,6 +170,7 @@ int main(int argc, char *argv[])
     dltdata.ohandle = -1;
 
     dltdata.running_test = 0;
+    dltdata.max_messages = INT_MIN;
 
     for (i = 0; i < DLT_TESTCLIENT_NUM_TESTS; i++) {
         dltdata.test_counter_macro[i] = 0;
@@ -179,7 +185,7 @@ int main(int argc, char *argv[])
     /* Fetch command line arguments */
     opterr = 0;
 
-    while ((c = getopt (argc, argv, "vashyxmf:o:e:b:")) != -1)
+    while ((c = getopt (argc, argv, "vashyxmf:o:e:b:z:")) != -1)
         switch (c) {
         case 'v':
         {
@@ -236,6 +242,11 @@ int main(int argc, char *argv[])
             dltdata.bvalue = atoi(optarg);
             break;
         }
+        case 'z':
+        {
+            dltdata.max_messages = atoi(optarg);
+            break;
+        }
         case '?':
         {
             if ((optopt == 'o') || (optopt == 'f') || (optopt == 't'))
@@ -262,6 +273,9 @@ int main(int argc, char *argv[])
     /* Register callback to be called when message was received */
     dlt_client_register_message_callback(dlt_testclient_message_callback);
 
+    /* Register callback to be called if next message needs to be fetched */
+    dlt_client_register_fetch_next_message_callback(dlt_testclient_fetch_next_message_callback);
+
     /* Setup DLT Client structure */
     g_dltclient.mode = dltdata.yflag;
 
@@ -354,6 +368,21 @@ int main(int argc, char *argv[])
     return g_testsFailed == 0 ? 0 : 1;
 }
 
+bool dlt_testclient_fetch_next_message_callback(void *data)
+{
+  if (data == 0)
+    return true;
+
+  DltTestclientData *dltdata = (DltTestclientData *)data;
+  if (dltdata->max_messages > INT_MIN)
+  {
+    dltdata->max_messages--;
+    if (dltdata->max_messages <= 0)
+      return false;
+  }
+  return true;
+}
+
 int dlt_testclient_message_callback(DltMessage *message, void *data)
 {
     static char text[DLT_TESTCLIENT_TEXTBUFSIZE];