From 9b63e94f825cee3d2dc4ca0b8156102cc84bb4c5 Mon Sep 17 00:00:00 2001
From: Magnus Lundborg <lundborg.magnus@gmail.com>
Date: Wed, 4 Dec 2013 09:21:47 +0100
Subject: Do not require pointer to NULL.


diff --git a/include/tng_io.h b/include/tng_io.h
index 7be9c12..7ae8967 100644
--- a/include/tng_io.h
+++ b/include/tng_io.h
@@ -4668,7 +4668,8 @@ tng_function_status DECLSPECDLLEXPORT tng_util_frame_current_compression_get
  * data for next_frame.
  * @param data_block_ids_in_next_frame is set to an array (of length
  * n_data_blocks_in_next_frame) that lists the data block IDs with data for
- * next_frame. The array is created by this function allocated.
+ * next_frame. It must be pointing at NULL or previously allocated memory.
+ * Memory for the array is allocated by this function.
  * The memory must be freed by the client afterwards or
  * there will be a memory leak.
  * @pre \code tng_data != 0 \endcode The trajectory container (tng_data)
@@ -4677,7 +4678,7 @@ tng_function_status DECLSPECDLLEXPORT tng_util_frame_current_compression_get
  * be NULL.
  * @pre \code n_data_blocks_in_next_frame != 0 \endcode The pointer to
  * n_data_blocks_in_next_frame must not be NULL.
- * @pre \code *data_block_ids_in_next_frame == 0 \endcode The pointer to the
+ * @pre \code *data_block_ids_in_next_frame != 0 \endcode The pointer to the
  * list of data block IDs must not be NULL.
  * @pre \code n_requested_data_block_ids == 0 || requested_data_block_ids != 0 \endcode
  * If the number of requested data blocks != 0 then the array of data block IDs must not be NULL.
diff --git a/src/lib/tng_io.c b/src/lib/tng_io.c
index 908f471..6bbc1c5 100644
--- a/src/lib/tng_io.c
+++ b/src/lib/tng_io.c
@@ -17955,12 +17955,23 @@ tng_function_status DECLSPECDLLEXPORT tng_util_trajectory_next_frame_present_dat
     TNG_ASSERT(tng_data, "TNG library: Trajectory container not properly setup.");
     TNG_ASSERT(next_frame, "TNG library: The pointer to the next frame must not be NULL.");
     TNG_ASSERT(n_data_blocks_in_next_frame, "TNG library: The pointer to n_data_blocks_in_next_frame must not be NULL.");
-    TNG_ASSERT(*data_block_ids_in_next_frame == 0, "TNG library: The pointer to the list of data block IDs must be NULL.");
+    TNG_ASSERT(data_block_ids_in_next_frame, "TNG library: The pointer to the list of data block IDs must not be NULL.");
 
     if(n_requested_data_block_ids)
     {
         TNG_ASSERT(requested_data_block_ids, "TNG library: If the number of requested data blocks is > 0 then the array of data block IDs must not be NULL.");
-        *data_block_ids_in_next_frame = malloc(sizeof(int64_t) * n_requested_data_block_ids);
+        size = sizeof(int64_t) * n_requested_data_block_ids;
+        temp = realloc(*data_block_ids_in_next_frame, size);
+        if(!temp)
+        {
+            printf("TNG library: Cannot allocate memory (%"PRId64" bytes). %s: %d\n",
+                    sizeof(int64_t) * (*n_data_blocks_in_next_frame),
+                    __FILE__, __LINE__);
+            free(*data_block_ids_in_next_frame);
+            *data_block_ids_in_next_frame = 0;
+            return(TNG_CRITICAL);
+        }
+        *data_block_ids_in_next_frame = temp;
     }
 
     frame_set = &tng_data->current_trajectory_frame_set;
-- 
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