byteorder.h

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/*
 * Author: Steven Ludtke, 04/10/2003 (sludtke@bcm.edu)
 * Copyright (c) 2000-2006 Baylor College of Medicine
 * 
 * This software is issued under a joint BSD/GNU license. You may use the
 * source code in this file under either license. However, note that the
 * complete EMAN2 and SPARX software packages have some GPL dependencies,
 * so you are responsible for compliance with the licenses of these packages
 * if you opt to use BSD licensing. The warranty disclaimer below holds
 * in either instance.
 * 
 * This complete copyright notice must be included in any revised version of the
 * source code. Additional authorship citations may be added, but existing
 * author citations must be preserved.
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 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 General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 * 
 * */
 
#ifndef eman__byteorder_h__
#define eman__byteorder_h__ 1
 
#include <cstddef>
 
namespace EMAN
{
        class ByteOrder
        {
        public:
                static bool is_host_big_endian();
 
                static bool is_float_big_endian(float small_number);
                
                
                template < class T > static bool is_data_big_endian(const T * small_num_addr)
                {
                        if (!small_num_addr) {
                                return false;
                        }
 
                        bool data_big_endian = false;
                        size_t typesize = sizeof(T);
                        char *d = (char *) small_num_addr;
 
                        if (is_host_big_endian()) {
                                data_big_endian = false;
                                for (size_t i = typesize / 2; i < typesize; i++)
                                        {
                                                if (d[i] != 0) {
                                                        data_big_endian = true;
                                                        break;
                                                }
                                        }
                        }
                        else {
                                data_big_endian = true;
                                for (size_t j = 0; j < typesize / 2; j++) {
                                        if (d[j] != 0) {
                                                data_big_endian = false;
                                                break;
                                        }
                                }
                        }
 
                        return data_big_endian;
                }
 
                template < class T > static void become_big_endian(T * data, size_t n = 1)
                {
                        if (!is_host_big_endian()) {
                                swap_bytes < T > (data, n);
                        }
                }
 
                template < class T > static void become_little_endian(T * data, size_t n = 1)
                {
                        if (is_host_big_endian()) {
                                swap_bytes < T > (data, n);
                        }
                }
 
                template < class T > static void swap_bytes(T * data, size_t n = 1)
                {
                        unsigned char s;
                        size_t p = sizeof(T);
                        char *d = (char *) data;
 
                        if (p > 1) {
                                for (size_t i = 0; i < n; i++, d += p) {
                                        for (size_t j = 0; j < p / 2; j++) {
                                                s = d[j];
                                                d[j] = d[p - 1 - j];
                                                d[p - 1 - j] = s;
                                        }
                                }
                        }
                }
 
        private:
                static bool is_host_endian_checked;
                static bool host_big_endian;
        };
 
}
 
#endif