little endian -> big endian

#include <stdio.h>

 

void change(int * n) //general way

{
 char *p = (char *)n;
 char t;
 t = p[0], p[0] = p[3], p[3] = t;
 t = p[1], p[1] = p[2], p[2] = t;
}

 

void change(int *n)
{
 printf("%d\n", (*n << 24));                    

 //   0100 0000 0000 0000 0000 0000 0000 0000 (0x04000000)

 printf("%d\n", ((*n << 8) & 0xff0000));      

//    0000 0010 0000 0011 0000 0100 0000 0000 (0x02030400)

// & 0000 0000 1111 1111 0000 0000 0000 0000 (0x00ff0000) 

//    0000 0000  0000 0011 0000 0000 0000 0000 (0x00030000)

 

 printf("%d\n", ((*n >> 8) & 0xff00) );        

//    0000 0000 0000 0001 0000 0010 0000 0011    (0x00010203)

// & 0000 0000 0000 0000 1111 1111 0000 0000    (0x0000ff00)

//    0000 0000 0000 0000 0000 0010 0000 0000    (0x00000200)

 printf("%d\n", (*n >> 24));                    

//    0000 0000 0000 0000 0000 0000 0000 0001    (0x00000001)

 *n = (*n << 24) | ((*n << 8) & 0x00ff0000) | ((*n >> 8) & 0x0000ff00) | (*n >> 24);
}

 

main()
{
 int xData = 0x01020304;
 char *ptr = (char*)&xData;

 printf("x = %d%d%d%d\n", ptr[0], ptr[1], ptr[2], ptr[3]);
 change1(&xData);
 printf("x = %d%d%d%d\n", ptr[0], ptr[1], ptr[2], ptr[3]);
}