Adding missing file

src/VTKWriter/byteswap_portable.hpp

+/*
+ * byteswap_portable.hpp
+ *
+ *  Created on: Feb 20, 2017
+ *      Author: i-bird
+ */
+
+#ifndef OPENFPM_IO_SRC_VTKWRITER_BYTESWAP_PORTABLE_HPP_
+#define OPENFPM_IO_SRC_VTKWRITER_BYTESWAP_PORTABLE_HPP_
+
+#include <climits>
+
+/*! \brief This function swap byte from little endian to big endian format
+ *
+ * \warning in the case of big-endian machine this function should do nothing.
+ *          Unfortunately this is not the case because I never had the bad luck
+ *          of getting one
+ *
+ * \param T value to convert
+ *
+ */
+template <typename T>
+T swap_endian_lt(T u)
+{
+    static_assert (CHAR_BIT == 8, "CHAR_BIT != 8");
+
+    union
+    {
+        T u;
+        unsigned char u8[sizeof(T)];
+    } source, dest;
+
+    source.u = u;
+
+    for (size_t k = 0; k < sizeof(T); k++)
+        dest.u8[k] = source.u8[sizeof(T) - k - 1];
+
+    return dest.u;
+}
+
+#endif /* OPENFPM_IO_SRC_VTKWRITER_BYTESWAP_PORTABLE_HPP_ */