Add the number of chemistry elements to the snapshot headers

src/chemistry/EAGLE/chemistry_io.h

@@ -283,6 +283,8 @@ INLINE static int chemistry_write_bparticles(const struct bpart* bparts,
 INLINE static void chemistry_write_flavour(hid_t h_grp) {
 
   io_write_attribute_s(h_grp, "Chemistry Model", "EAGLE");
+  io_write_attribute_d(h_grp, "Chemistry element count",
+                       chemistry_element_count);
   for (int elem = 0; elem < chemistry_element_count; ++elem) {
     char buffer[20];
     sprintf(buffer, "Element %d", elem);

src/chemistry/GEAR/chemistry_io.h

@@ -116,6 +116,8 @@ INLINE static int chemistry_write_bparticles(const struct bpart* bparts,
 INLINE static void chemistry_write_flavour(hid_t h_grp) {
 
   io_write_attribute_s(h_grp, "Chemistry Model", "GEAR");
+  io_write_attribute_d(h_grp, "Chemistry element count",
+                       GEAR_CHEMISTRY_ELEMENT_COUNT);
 }
 #endif
 

src/chemistry/none/chemistry_io.h

@@ -98,6 +98,7 @@ INLINE static int chemistry_write_bparticles(const struct bpart* bparts,
 INLINE static void chemistry_write_flavour(hid_t h_grp) {
 
   io_write_attribute_s(h_grp, "Chemistry Model", "None");
+  io_write_attribute_d(h_grp, "Chemistry element count", 0);
 }
 #endif