Use pointer to existing array instead of array copy.

src/stream_cdf_o.c

@@ -1220,14 +1220,18 @@ cdf_def_zaxis_hybrid_cf(stream_t *streamptr, int type, int *ncvaridp, int zaxisI
   int nvdimID = CDI_UNDEFID;
 
   double *buffer = (double *) malloc(4 * dimlen * sizeof(double));
-  double *levels = buffer;
   double *lbounds = buffer + 2 * dimlen;
   double *ubounds = buffer + 3 * dimlen;
+  double *restrict levels;
 
-  if (zaxisInqLevels(zaxisID, NULL))
-    zaxisInqLevels(zaxisID, levels);
+  bool hasLevels = zaxisInqLevels(zaxisID, NULL) != 0;
+  if (hasLevels)
+    levels = (double *) zaxisInqLevelsPtr(zaxisID);
   else
-    for (size_t i = 0; i < dimlen; ++i) levels[i] = i + 1;
+    {
+      levels = (double *) Malloc(sizeof(*levels) * dimlen);
+      for (size_t i = 0; i < dimlen; ++i) levels[i] = (double) (i + 1);
+    }
 
   if (zaxisInqLbounds(zaxisID, NULL) && zaxisInqUbounds(zaxisID, NULL))
     {
@@ -1281,6 +1285,7 @@ cdf_def_zaxis_hybrid_cf(stream_t *streamptr, int type, int *ncvaridp, int zaxisI
   streamptr->ncmode = 2;
 
   cdf_put_var_double(fileID, ncvarid, levels);
+  if (!hasLevels) Free(levels);
 
   if (p0varid != CDI_UNDEFID) cdf_put_var_double(fileID, p0varid, &p0value);