#define __int8 char
typedef unsigned int guint32;

void func(char *datac, guint32 data_len)
{
int i;
int per;
char tmp;
unsigned __int8 *tar;
signed int per2;

per = (data_len - 136 + 3) >> 2;// div 4
tar = (unsigned __int8 *)(datac + 136); //&datac[136]
for ( i = 0; i < per; ++i )
{
if ( i & 1 ) //condition : odd number
{/* exchang data in tar and tar[i+per] */
tmp = tar;
tar = *(&tar + per); // = tar[i+per]
*(&tar + per) = tmp;
}
}

per2 = (signed int)(data_len - 136 - 3 * per);
for ( i = 0; i < per2; ++i )
{
if ( !(i & 1) )//condition : even number
{/* exchang data in tar[2 * per + i] and tar[3 * per + i] */
tmp = *(&tar[2 * per] + i);
*(&tar[2 * per] + i) = *(&tar[3 * per] + i);
*(&tar[3 * per] + i) = tmp;
}
}
}