minix代码中conv2()函数的作用

conv2()函数根据机器类型交换大小端数据。

PUBLIC unsigned conv2(norm, w)
int norm;   /* TRUE if no swap, FALSE for byte swap */
int w;    /* promotion of 16-bit word to be swapped */
{
/* Possibly swap a 16-bit word between 8086 and 68000 byte order. */
  if (norm) return( (unsigned) w & 0xFFFF);
  return( ((w&BYTE) << 8) | ( (w>>8) & BYTE));
}

另有conv4()函数，有类似功能，定义为

 21360    _PROTOTYPE( unsigned conv2, (int norm, int w)                           );
 21361    _PROTOTYPE( long conv4, (int norm, long x)                              );

有宏定义，标示需不需要交换

 21056    #define BYTE_SWAP          0    /* tells conv2/conv4 to swap bytes */

 

conv2参考自http://blog.csdn.net/xiaojialin/article/details/6543913