strcpy和memcpy用法(待完善测试用例)

#include<cstdio>
#include<cstring>
#include<cassert>

char *myStrcpy(char* dest, const char* src){
    if ((NULL == dest) || (NULL == src)){
        return NULL;
    }

    char *strDest = dest;
    const char *strSrc = src;
    while ((*dest++ = *strSrc++) != ‘\0‘);
    return strDest;    
}

void *myMemcpy(void *dest, const void *src, size_t size){
    if(NULL == dest || NULL == src){
        return NULL;
    }

    char *pDest = NULL;
    char *pSrc = NULL;

    if ((src < dest) && ((char*)src + size > (char*)dest)){
        pDest = (char *)dest + size - 1;
        pSrc = (char *)src + size - 1;
        while(size--){
            *pDest-- = *pSrc--;
        }
    }
    else{
        pSrc = (char *)src;
        pDest = (char *)dest;
        while (size--)
        {
            *pDest++ = *pSrc;
        }
    }
    
    return dest;
}


void testStrcpy();
void testMemcpy();

int main(){
    // testStrcpy();
    testMemcpy();

}

void testMemcpy(){
    char buf[100] = "abcdefghijklmn";
    myMemcpy(buf+2, buf, 4);
    printf("buf = %s\n", buf+2);

}

void testStrcpy(){
    char src[40];
    char dest[100];

    memset(dest, ‘\0‘, sizeof(dest));
    char *dest1 = myStrcpy(src, "this is test of  strcpy");
    printf("dest1 = %s\n" , dest1);
    myStrcpy(dest, src);
    printf("dest = %s\n" , dest);
}