open watcom学习记录之——字节序交换,另一帖回复满了

C/C++ code

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);}

C/C++ code

#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));}//1e6a2c48//1e6a2c48//1e6a2c48