Added function tng_util_prepare_append_after_frame()

2 files changed, 40 insertions, 0 deletions

diff --git a/include/tng_io.h b/include/tng_io.h
index 292700f..7ecbcaa 100644
--- a/include/tng_io.h
+++ b/include/tng_io.h
@@ -4712,6 +4712,20 @@ tng_function_status DECLSPECDLLEXPORT tng_util_trajectory_next_frame_present_dat
                  int64_t *n_data_blocks_in_next_frame,
                  int64_t **data_block_ids_in_next_frame);
 
+/** @brief Finds the frame set of the specified frame in order to prepare for writing
+ * after it.
+ * @param tng_data is the trajectory to use.
+ * @param prev_frame is the frame after which to start appending.
+ * @pre \code tng_data != 0 \endcode The trajectory container (tng_data)
+ * must be initialised before using it.
+ * @pre \code prev_frame >= 0 \endcode The previous frame must not be negative.
+ * @return TNG_SUCCESS (0) if successful, TNG_FAILURE (1) if a minor error
+ * has occured (such as not finding the requested frame) or TNG_CRITICAL (2)
+ * if a major error has occured.
+ */
+tng_function_status DECLSPECDLLEXPORT tng_util_prepare_append_after_frame
+                (tng_trajectory_t tng_data,
+                 const int64_t prev_frame);
 
 /** @} */ /* end of group2 */
 
diff --git a/src/lib/tng_io.c b/src/lib/tng_io.c
index 57744e8..33d58ba 100644
--- a/src/lib/tng_io.c
+++ b/src/lib/tng_io.c
@@ -18306,3 +18306,29 @@ tng_function_status DECLSPECDLLEXPORT tng_util_trajectory_next_frame_present_dat
 
     return(TNG_SUCCESS);
 }
+
+tng_function_status DECLSPECDLLEXPORT tng_util_prepare_append_after_frame
+                (tng_trajectory_t tng_data,
+                 const int64_t prev_frame)
+{
+    tng_function_status stat;
+    FILE *temp = tng_data->input_file;
+
+    TNG_ASSERT(tng_data, "TNG library: Trajectory container not properly setup.");
+    TNG_ASSERT(prev_frame >= 0, "TNG library: The previous frame must not be negative.");
+
+    tng_data->input_file = tng_data->output_file;
+
+    stat = tng_frame_set_of_frame_find(tng_data, prev_frame);
+    if(stat != TNG_SUCCESS)
+    {
+        return(stat);
+    }
+
+    tng_data->current_trajectory_frame_set_output_file_pos =
+    tng_data->current_trajectory_frame_set_input_file_pos;
+
+    tng_data->input_file = temp;
+
+    return(TNG_SUCCESS);
+}