open watcom学习记要之——字节序交换,另一帖回复满了

int swap32_1(int i)
{
return ((i&0xff000000)>>24)|((i&0xff0000)>>8)|((i&0xff00)<<8)|((i&0xff)<<24);
}

int swap(int x)
{
int out,i;
char *p_in=(char*)&x,*p_out=(char*)&out;
while (i<sizeof(int))
p_out[i++]=p_in[sizeof(int)-1-i];/*赋值运算先算右面，所以要把i++放在左面*/
return out;
}

int bswap(int x)
{
  int ret;
  /*psrc指向x首字节,pdst指向ret之后*/
  char *psrc=(char*)&x,*pdst=(char*)(&ret+1);
  while(pdst>(char*)&ret)
    *--pdst=*psrc++;
  return ret;
}

main()
{
int a=0x12345678;
printf("a=%x\n",a);
a=swap32_1(a);
printf("swap32_1--->%x\n",a);
a=0x12345678;
a=swap(a);
printf("swap--->%x\n",a);
a=0x12345678;
a=bswap(a);
printf("bswap--->%x",a);
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int v;
int bitrev1(const int b) {
    register int n;

    n=b;
    n=((n>> 1)&0x55555555)|((n<< 1)&0xaaaaaaaa);
    n=((n>> 2)&0x33333333)|((n<< 2)&0xcccccccc);
    n=((n>> 4)&0x0f0f0f0f)|((n<< 4)&0xf0f0f0f0);
    n=((n>> 8)&0x00ff00ff)|((n<< 8)&0xff00ff00);
    n=((n>>16)&0x0000ffff)|((n<<16)&0xffff0000);
    return n;
}
int bitrev2(const int b) {
    __asm {
        push ebx
        push ecx
        mov ebx,b
        mov ecx,32
    nextbit:
        rcl ebx,1
        rcr eax,1
        loop nextbit
        pop ecx
        pop ebx
    }
}
int bitrev3(const int b) {
    char bs[33],bs1[33],*ep;

    itoa(b,bs1,2);
    sprintf(bs,"%032s",bs1);
    strrev(bs);
    return strtol(bs,&ep,2);
}
void main() {
    v=0x12345678;//0001 0010 0011 0100 0101 0110 0111 1000
    printf("%08x\n",bitrev1(v));
    printf("%08x\n",bitrev2(v));
    printf("%08x\n",bitrev3(v));
}
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