Add '24hour-delta' timestamp option

When enabled this option will timestamp new lines with the time elapsed
since the line before.

This is a very useful feature to identify which events takes the most
time.

src/misc.c

@@ -35,17 +35,17 @@
 char *current_time(void)
 {
     static char time_string[TIME_STRING_SIZE_MAX];
-    static struct timeval tv_start;
+    static struct timeval tv, tv_now, tv_start, tv_previous;
     static bool first = true;
     struct tm *tm;
-    struct timeval tv;
     size_t len;
 
-    gettimeofday(&tv, NULL);
+    // Get current time value
+    gettimeofday(&tv_now, NULL);
 
     if (first)
     {
-        tv_start = tv;
+        tv_start = tv_now;
         first = false;
     }
 
@@ -55,19 +55,26 @@ char *current_time(void)
         case TIMESTAMP_NONE:
         case TIMESTAMP_24HOUR:
             // "hh:mm:ss.sss" (24 hour format)
-            tm = localtime(&tv.tv_sec);
+            tm = localtime(&tv_now.tv_sec);
             len = strftime(time_string, sizeof(time_string), "%H:%M:%S", tm);
             break;
         case TIMESTAMP_24HOUR_START:
             // "hh:mm:ss.sss" (24 hour format relative to start time)
-            timersub(&tv, &tv_start, &tv);
+            timersub(&tv_now, &tv_start, &tv);
+            tv.tv_sec -= 3600; // Why is this needed??
+            tm = localtime(&tv.tv_sec);
+            len = strftime(time_string, sizeof(time_string), "%H:%M:%S", tm);
+            break;
+        case TIMESTAMP_24HOUR_DELTA:
+            // "hh:mm:ss.sss" (24 hour format relative to previous time stamp)
+            timersub(&tv_now, &tv_previous, &tv);
             tv.tv_sec -= 3600; // Why is this needed??
             tm = localtime(&tv.tv_sec);
             len = strftime(time_string, sizeof(time_string), "%H:%M:%S", tm);
             break;
         case TIMESTAMP_ISO8601:
             // "YYYY-MM-DDThh:mm:ss.sss" (ISO-8601)
-            tm = localtime(&tv.tv_sec);
+            tm = localtime(&tv_now.tv_sec);
             len = strftime(time_string, sizeof(time_string), "%Y-%m-%dT%H:%M:%S", tm);
             break;
         default:
@@ -80,6 +87,9 @@ char *current_time(void)
         len = snprintf(time_string + len, TIME_STRING_SIZE_MAX - len, ".%03ld", (long)tv.tv_usec / 1000);
     }
 
+    // Save previous time value for next run
+    tv_previous = tv_now;
+
     return (len < TIME_STRING_SIZE_MAX) ? time_string : NULL;
 }
 

src/options.c

@@ -117,6 +117,10 @@ const char* timestamp_token(enum timestamp_t timestamp)
             return "24hour-start";
             break;
 
+        case TIMESTAMP_24HOUR_DELTA:
+            return "24hour-delta";
+            break;
+
         case TIMESTAMP_ISO8601:
             return "iso8601";
             break;
@@ -133,10 +137,22 @@ enum timestamp_t timestamp_option_parse(const char *arg)
     
     if (arg != NULL)
     {
-        if (strcmp(arg, "24hour-start") == 0)
+        if (strcmp(arg, "none") == 0)
+        {
+            return TIMESTAMP_NONE;
+        }
+        else if (strcmp(arg, "24hour") == 0)
+        {
+            return TIMESTAMP_24HOUR;
+        }
+        else if (strcmp(arg, "24hour-start") == 0)
         {
             return TIMESTAMP_24HOUR_START;
         }
+        else if (strcmp(arg, "24hour-delta") == 0)
+        {
+            return TIMESTAMP_24HOUR_DELTA;
+        }
         else if (strcmp(arg, "iso8601") == 0)
         {
             return TIMESTAMP_ISO8601;

src/options.h

@@ -31,6 +31,7 @@ enum timestamp_t
     TIMESTAMP_NONE,
     TIMESTAMP_24HOUR,
     TIMESTAMP_24HOUR_START,
+    TIMESTAMP_24HOUR_DELTA,
     TIMESTAMP_ISO8601,
     TIMESTAMP_END,
 };

src/tty.c

@@ -355,6 +355,9 @@ void handle_command_sequence(char input_char, char previous_char, char *output_c
                     case TIMESTAMP_24HOUR_START:
                         tio_printf("Switched to 24hour-start timestamp mode");
                         break;
+                    case TIMESTAMP_24HOUR_DELTA:
+                        tio_printf("Switched to 24hour-delta timestamp mode");
+                        break;
                     case TIMESTAMP_ISO8601:
                         tio_printf("Switched to iso8601 timestamp mode");
                         break;