判别机器大小端，打印int的二进制

来源：互联网发布：linux tail f 编辑：程序博客网时间：2024/05/05 20:40

在学习c的位运算，有点作用的几个函数。

union int_per_byte_u{unsigned int value;unsigned char bs[4];};void print_per_byte(in int a){union int_per_byte_u b;int i;b.value = a;for( i=0; i<4; ++i ){printf("%d  ", b.bs[i]);}printf("\n");}int is_small_endian(){short i = 0x0001;return ((char *)&i)[0];//[0] is low byte, [1] is high byte.}int is_big_endian(){union int_per_byte_u b;b.value = 1;if( b.bs[0] )return(0);return(1);//[0] is low byte, [1] is high byte.}void print_binary_xx(in const char *a,in int bytes){const char *pos = a;int i,j;if( is_small_endian() ){for(i=bytes-1; i>=0; --i){for(j=7; j>=0; --j){printf("%d",( pos[i]&(1<<j)?1:0 ));}printf(" ");}}printf("\n");}double absolute(in double x){double tmp = x;*(((int *)&tmp)+1)&=0x7fffffff;return tmp;//0&1=0//to the high byte,highest zero is postive.}int align_down(in int a,in int size){return (a&~(size-1));}int align_up(in int a,in int size){//-b = ~(b-1);return ((a+size-1)&~(size-1));}

</pre><p><pre name="code" class="cpp">int main(){printf("lesson_1 hacker's book. size int %d \n", sizeof(int));printf("big endian:%d, small endian:%d \n",is_big_endian(), is_small_endian());printf("sizeof void",sizeof(void));//two ff is a byteint a=0x010204ff;print_binary_xx( (char *)&a, 4);//absolutedouble n = -1.2;print_binary_xx( (char *)&n, 8 );double abs = absolute( n );print_binary_xx( (char *)&abs, 8 );//up-down-alignint down = align_down( 63, 16);int up = align_up( 63, 16 );printf("down align:%d, up align:%d \n",down, up);return 0;}

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