C函数库中的memmove实现

/**copyright@nciaebupt 转载请注明出处*原型：void *memmove(void *dest, const void *src, size_t count);*用法：#include <string.h>*功能：由src所指内存区域复制count个字节到dest所指内存区域。*说明：src和dest所指内存区域可以重叠，但复制后src内容会被更改。函数返回指向dest的指针。*使用C函数库中的memmove**/#include <cstdio>#include <cstring>int main(int args,char ** argv){    char src[] = "memmove can be very useful......";    char dest[40] ={""};    memmove(src + 20,src + 15,11);    printf("%s\n",src);    getchar();    return 0;}/**copyright@nciaebupt 转载请注明出处*原型：void *memmove(void *dest, const void *src, size_t count);*用法：#include <string.h>*功能：由src所指内存区域复制count个字节到dest所指内存区域。*说明：src和dest所指内存区域可以重叠，但复制后src内容会被更改。函数返回指向dest的指针。*自己实现memmove**/#include <cstdio>#include <cstring>void * _memmove(void * dest, const void * src, size_t count){    void * ret = dest;    if((char *)dest <= (char *)src ||(char *)dest >= ((char *)src) + count)    {//如果数据区没有重合，则从低地址向高地址复制        while(count--)        {            *((char *)dest) = *((char *)src);            dest = (char *)dest + 1;            src = (char *)src + 1;        }    }    else//如果数据区有重合，则从高地址向低地址复制    {        dest = (char *)dest + count - 1;        src = (char *)src + count - 1;        while(count--)        {            *((char *)dest) = *((char *)src);            dest = (char *)dest - 1;            src = (char *)src -1;        }    }    return ret;}int main(int args,char ** argv){    char src[] = "memmove can be very useful......";    char dest[40] ={""};    _memmove(src + 20,src + 15,11);    printf("%s\n",src);    getchar();    return 0;}