byteorder.h

Go to the documentation of this file.

#ifndef BYTEORDER_H
#define BYTEORDER_H

#include <sys/types.h>

inline int get_byte_order()
{                // 1 if little endian
        return (*(u_int32_t*)"a   ") & 0x00000001;
}

#define SWAP_ITERATE \
                                        byte1 = buffer1[i]; \
                                byte2 = buffer2[i]; \
                                buffer1[i] = byte2; \
                                buffer2[i] = byte1; \
                                        i += 2;
                                                                                                 
#define SWAP_24BIT_ITERATE \
                                        byte1 = buffer1[i]; \
                                byte2 = buffer2[i]; \
                                byte3 = buffer3[i]; \
                                buffer1[i] = byte3; \
                                buffer2[i] = byte2; \
                                buffer3[i] = byte1; \
                                i += 3;

#define SWAP_32BIT_ITERATE \
                                        byte1 = buffer1[i]; \
                                byte2 = buffer2[i]; \
                                byte3 = buffer3[i]; \
                                byte4 = buffer4[i]; \
                                buffer1[i] = byte4; \
                                buffer2[i] = byte1; \
                                buffer3[i] = byte2; \
                                buffer4[i] = byte3; \
                                i += 4;

inline int swap_bytes(int wordsize, unsigned char *buffer, long len)
{
        register unsigned char byte1, byte2, byte3, byte4;
        register unsigned char *buffer1 = buffer;
        register unsigned char *buffer2 = buffer + 1;
        register unsigned char *buffer3 = buffer + 2;
        register unsigned char *buffer4 = buffer + 3;

        register long i = 0, j = 0, k = 0;

//printf("swap bytes\n");

        switch(wordsize)
        {
                case 1:
                        return 0;
                        break;
                
                case 2:
                        len -= 8;
                        while(i < len){
                        SWAP_ITERATE
                        SWAP_ITERATE
                        SWAP_ITERATE
                        SWAP_ITERATE
                        }

                        len += 8;
                        while(i < len){
                        SWAP_ITERATE
                        }
                        return 0;
                        break;

                case 3:
                        len -= 12;
                        while(i < len){
                        SWAP_24BIT_ITERATE
                        SWAP_24BIT_ITERATE
                        SWAP_24BIT_ITERATE
                        SWAP_24BIT_ITERATE
                        }

                        len += 12;
                        while(i < len){
                        SWAP_24BIT_ITERATE
                        }
                        return 0;
                        break;

                case 4:
                        len -= 16;
                        while(i < len)
                        {
                                SWAP_32BIT_ITERATE
                                SWAP_32BIT_ITERATE
                                SWAP_32BIT_ITERATE
                                SWAP_32BIT_ITERATE
                        }

                        len += 16;
                        while(i < len)
                        {
                                SWAP_32BIT_ITERATE
                        }
                        return 0;
                        break;
        }
        return 1;
}

#endif

---