diff --git a/src/io_types.h b/src/io_types.h
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+/*******************************************************************************
+ * This file is part of SWIFT.
+ * Coypright (c) 2012 Matthieu Schaller (matthieu.schaller@durham.ac.uk).
+ * 
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ * 
+ ******************************************************************************/
+
+#include <hdf5.h>
+
+/**
+ * @brief Error macro
+ *
+ */
+#define error(s) { fprintf( stderr , "%s:%s():%i: %s\n" , __FILE__ , __FUNCTION__ , __LINE__ , s ); abort(); }
+
+/**
+ * @brief The different types of data used in the GADGET IC files.
+ *
+ * (This is admittedly a poor substitute to C++ templates...)
+ */
+enum DATA_TYPE{INT, LONG, LONGLONG, UINT, ULONG, ULONGLONG, FLOAT, DOUBLE};
+
+/**
+ * @brief The two sorts of data present in the GADGET IC files: compulsory to start a run or optional.
+ *
+ */
+enum DATA_IMPORTANCE{COMPULSORY=1, OPTIONAL=0};
+
+/**
+ * @brief Converts a C data type to the HDF5 equivalent. 
+ *
+ * This function is a trivial wrapper around the HDF5 types but allows
+ * to change the exact storage types matching the code types in a transparent way.
+ */
+static hid_t hdf5Type(enum DATA_TYPE type)
+{
+  switch(type)
+    {
+    case INT: return H5T_NATIVE_INT;
+    case UINT: return H5T_NATIVE_UINT;
+    case LONG: return H5T_NATIVE_LONG;
+    case ULONG: return H5T_NATIVE_ULONG;
+    case LONGLONG: return H5T_NATIVE_LLONG;
+    case ULONGLONG: return H5T_NATIVE_ULLONG;
+    case FLOAT: return H5T_NATIVE_FLOAT;
+    case DOUBLE: return H5T_NATIVE_DOUBLE;
+    default: error("Unknown type");
+    }
+}
+
+/**
+ * @brief Returns the memory size of the data type
+ */
+static size_t sizeOfType(enum DATA_TYPE type)
+{
+  switch(type)
+    {
+    case INT: return sizeof(int);
+    case UINT: return sizeof(unsigned int);
+    case LONG: return sizeof(long);
+    case ULONG: return sizeof(unsigned long);
+    case LONGLONG: return sizeof(long long);
+    case ULONGLONG: return sizeof(unsigned long long);
+    case FLOAT: return sizeof(float);
+    case DOUBLE: return sizeof(double);
+    default: error("Unknown type");
+    }
+}
+
+