c 语言位操作

今天在看《Unix 环境高级编程》时对信号集的操作(P254),这个在对寄存器或者标志位做位操作时很有借鉴意义。

 #BIT_WIDTH    32
 #define BITBAD( bit ) ( (bit)<=0 || (bit) >= BIT_WIDTH  )
 
 // set one bit in the flag 
 bit_set( long flag,  int bit )
 {
     if( BITBAD(bit) )     
             oops(" bit is not correct"," ");
     *flag |= 1<<( bit - 1 );
 }
 
//delete one bit in the flag
 bit_del( long flag,  int bit ) 
{
    if( BITBAD(bit) )
             oops(" bit is not correct"," ");
     *flag &= ~( 1<<( bit - 1 ) );
 }
 
//test one bit int flag
bit_test( long flag,  int bit )
{
     if( BITBAD(bit) )
             oops(" bit is not correct"," ");
      return( (*flag & ( 1<<( bit-1) ) ) != 0 );
 }