当memcpy遇到大小端问题

来源：互联网发布：足球数据分析大师编辑：程序博客网时间：2024/05/21 07:57

经常看到memcpy的源码都是针对char型做处理，当遇到short int 和char同时作为参数时，就得不到想要的结果，都是大小端惹的祸。

#include <stdio.h>#include <string.h>#include <assert.h>void *first_memcpy(void *dest,void *src, unsigned int count){assert((dest!=NULL)&&(src!=NULL));int i=0,k=0;if(dest==src)return src;char* d=(char*)dest;char* s=(char*)src;while(count--> 0){*d++=*s++;}return dest;}void *second_memcpy(void *dest,void *src, unsigned int count){assert((dest!=NULL)&&(src!=NULL));int i=0,k=0;if(dest==src)return src;unsigned short* d=(unsigned short*)dest;char* s=(char*)src;while(count--> 0){d[i]=(s[k]<<8)|s[k+1];i+=1;k+=2;}return dest;}void main(){        int i;        unsigned short des[24]={0};        unsigned char src[13]={0x12, 0x34, 0x56, 0x78};        memcpy(des,src,4);                printf("1 memcpy:\n");        for(i=0;i<4;i++)        {                printf("%04x,",des[i]);        }         printf("\n");                  first_memcpy(des,src,4);                printf("1 first_memcpy:\n");        for(i=0;i<4;i++)        {                printf("%04x,",des[i]);        }         printf("\n");                 second_memcpy(des,src,4);        printf("1 second_memcpy:\n");        for(i=0;i<4;i++)        {                printf("%04x,",des[i]);        }         printf("\n");}

执行结果:

1 memcpy:
3412,7856,0000,0000,
1 first_memcpy:
3412,7856,0000,0000,
1 second_memcpy:
1234,5678,0000,0000,

最后一种情况才是我们想要的！

阅读全文

0 0