strlen strcopy strcat memcpy strcmp的实现（都是数据的拷贝比较等）

#define err_num 144


int str_cmp(char* des,const char* src)
{
int len_des = strlen(des);
int len_src = strlen(src);


if (len_src > len_des)
{
return 1;
}else if (len_des > len_src)
{
return -1;


}else if (len_des == len_src)
{
while (*src != '\0')
{
if (*src++ != *des++)
{
return err_num;
}
}
return 0;
}
}


void str_cat(char* src,char* des)
{
int len = strlen(des);
des += len;
while (*src != '\0')
{
*des++ = *src++;
}
}


int str_len(const char* str)
{
int i = 0;
while (*str++ != '\0')
{
i++;
}
return i;
}


char *get_mem(char*p,int size)
{
p = (char*)malloc(size);
memset(p,0,size);
return p;
}




void str_cpy(char*des,const char* src)
{
while (*src != '\0')
{
*des++ = *src++;
}
}


void mem_cpy(void *des,const void* src,int size)
{
char *t2 = (char*)src;


char* t1 = (char*)des;


for(int i= 0;i<size;i++)
{
*t1++ = *t2++;
}


}