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#include <stdio.h>
unsigned int reverse_bits(unsigned int value)
{
    unsigned int answer;
    unsigned int i;
    answer = 0;
   
    for(i=1;i!=0;i<<=1){ //´ËÑ­»·¿ÉÒÔºöÂÔ»úÆ÷µÄ²îÒì¡£64λºÍ32λ½Ô¿ÉÓã¬ÔöÇ¿´Ë´úÂëµÄ¿ÉÒÆÖ²ÐÔ
        answer <<=1;
        if(value & 1)
            answer |= 1;
        value >>=1;
    }
    return answer;
}
int main(void)
{
    unsigned int get_answer=reverse_bits(13);
    int i=31;
    char t;
    while(i)
    {
        t ='0'+ ((get_answer >> i) & 1);
        printf("%c",t);
        i--;
    }
}
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Linux 2.6 kernelÖеÄset_bit²Ù×÷£º
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static inline void set_bit(int nr, volatile unsigned long *addr)
{
    int *a = (int *)addr;
    int mask;
    //unsigned long flags;
    a += nr >> 5; 
    mask = 1 << (nr & 0x1f);
    //local_irq_save_hw(flags);
    *a |= mask;
    //local_irq_restore_hw(flags);
}