c++类对象练习

#include <iostream>
#include <cstring>

using namespace std;

class mystring
{
    char* buf;
public:
    mystring(); //构造函数
    mystring(const char* str); //构造函数
    void show(); //输出函数
    void setmystr(const mystring str); //设置函数
    const char* getmystr() const; //获取函数
    void append(const mystring str); //追加函数
    int isEqual(const mystring str); // 比较函数
    ~mystring(); //析构函数
};

mystring::mystring()
{
    buf = (char*)calloc(1,1);
}

mystring::mystring(const char * str)
{
    int len = strlen(str);
    buf = (char*)calloc(1,len+1);
    strcpy(buf , str);
}

void mystring::show()
{
    cout << buf << endl;
}

void mystring::setmystr(const mystring str)
{
    free(this->buf);
    int len = strlen(str.buf);
    this->buf = (char*)calloc(1 , len+1);
    strcpy(this->buf , str.buf);
}

const char* mystring::getmystr() const
{
    return buf;
}

//追加函数
void mystring::append(const mystring str)
{
    int len1 = strlen(this->buf);
    char* temp = (char*)calloc(1,len1+1);
    strcpy(temp , this->buf);
    free(this->buf);

    int len2 = strlen(str.buf);
    this->buf = (char*)calloc(1,len1+len2+1);
    strcat(this->buf , temp);
    strcat(this->buf , str.buf);
}

//比较函数
int mystring::isEqual(const mystring str)
{
    if(strcmp(buf , str.buf) > 0)
    {
        return 1;
    }
    else if(strcmp(buf , str.buf) < 0)
    {
        return -1;
    }
    else
        return 0;
    /*
    int i = 0;
    while(this->buf[i] != '\0' || str.buf[i] != '\0')
    {
        if(this->buf[i] < str.buf[i] || this->buf[i] == '\0')
        {
            return -1;
        }
        else if(this->buf[i] > str.buf[i] || str.buf[i] == '\0')
        {
            return 1;
        }

        i++;

    }
    return 0;
    */
}

//析构函数
mystring::~mystring()
{
    free(buf);
    buf = NULL;
}

int main()
{
    mystring str = "hello world";
    mystring ptr;
    str.show();
    ptr.setmystr("hello kitty");
    cout << ptr.getmystr() << endl;

    ptr.append(str);
    ptr.show();
    str.show();

    int res = ptr.isEqual(str);
    if(res < 0)
    {
        cout << "ptr < str" <<endl;
    }
    else if(res > 0)
    {
        cout << "ptr > str" <<endl;
    }
    else
    {
        cout << "ptr = str" <<endl;
    }
    return 0;
}

#include <iostream>
#include <cstdio>
#include <cstring>

using namespace std;

class myfile
{

    FILE * fp;
public:
    myfile();
    FILE * myfopen(const char * pathname , const char * mode);
    size_t mywrite(const void * buf , size_t size , size_t num);
size_t myread(void * buf , size_t size , size_t num);
    ~myfile();
};

myfile::myfile()
{
    fp = NULL;
}

FILE * myfile::myfopen(const char *pathname, const char *mode)
{
    fp = fopen(pathname,mode);
    if(fp == NULL)
    {
        return NULL;
    }
    return fp;
}

size_t myfile::mywrite(const void *buf, size_t size, size_t num)
{
    size_t res = fwrite(buf , size , num , this->fp);
cout << "wres = " << res << endl;
    if(res == 0 || res < num)
    {
        return 0;
    }
    return 1;
}

size_t myfile::myread(void * buf, size_t size, size_t num)
{
size_t res = fread(buf , size , num , this->fp);
cout << "res = " << res << endl;
if(res == 0 || res < num)
{
return 0;
}
return 1;
}

myfile::~myfile()
{
fclose(fp);
}

int main()
{
    myfile fp;
    fp.myfopen("./test1.txt" , "w");
    while(1)
{
char buf[64] = {0};
   cout << "请输入：" << endl;
    cin >> buf;
if(strcmp(buf , "quit") == 0)
{break;}
    fp.mywrite(buf , 1 , sizeof(buf));
}
fp.~myfile();

fp.myfopen("./test1.txt" , "r");
while(1)
{
cout << "111" << endl;
char rbuf[64] = {0};
size_t res = fp.myread(rbuf , 1 ,sizeof(rbuf));
cout << res << endl;
if(res == 0)
{break;}
cout << "rbuf = " << rbuf << endl;
}
    return 0;
}

原文地址：https://blog.csdn.net/m0_71556251/article/details/143864822

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