Update first trajectory frame set (if needed) when writing frame set

Conflicts:

	src/lib/tng_io.c

1 files changed, 6 insertions, 1 deletions

diff --git a/src/lib/tng_io.c b/src/lib/tng_io.c
index eeba683..e6f2956 100644
--- a/src/lib/tng_io.c
+++ b/src/lib/tng_io.c
@@ -7981,7 +7981,6 @@ tng_function_status tng_frame_set_write(tng_trajectory_t tng_data,
     &tng_data->current_trajectory_frame_set;
     
     tng_function_status stat;
-    
 
     tng_data->current_trajectory_frame_set_output_file_pos =
     tng_data->last_trajectory_frame_set_output_file_pos = 
@@ -7992,6 +7991,12 @@ tng_function_status tng_frame_set_write(tng_trajectory_t tng_data,
         return(TNG_FAILURE);
     }
 
+    if(tng_data->first_trajectory_frame_set_output_file_pos == -1)
+    {
+        tng_data->first_trajectory_frame_set_output_file_pos =
+        tng_data->current_trajectory_frame_set_output_file_pos;
+    }
+
     tng_block_init(&block);
 
     if(tng_frame_set_block_write(tng_data, block, hash_mode) != TNG_SUCCESS)