string类实现-优快云博客

本文介绍了一个简单的自定义String类的实现过程，包括构造函数、赋值运算符重载、字符串比较等功能。通过C++代码展示了如何管理和操作字符串内存。

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#include <string.h>

class string
{
public:
string();
string(const char *s);
string(const string& s);
~string();

// 赋值运算符
const string & operator =(const char *s);
const string & operator =(const string &s);

// 比较字符串是否相等
bool operator == (const char *s) const;
bool operator == (const string &s) const;

// 比较字符串大小
bool operator < (const char *s) const;
bool operator < (const string &s) const;
bool operator > (const char *s) const;
bool operator > (const string &s) const;

// 字符串长度
int length() const { return m_length; }

// 转化到字符指针
const char * data() const { return m_data; }

// 清空字符串
void clear();

private:
int m_length;
char *m_data;
};

string::string()
: m_length(0)
{
m_data = new char[1];
m_data[0] = '\0';
}

string::string(const char *s)
{
m_length = strlen(s);
m_data = new char[m_length+1];
memcpy(m_data, s, m_length+1);
}

string::string(const string &s)
{
m_length = s.length();
m_data = new char[m_length+1];
memcpy(m_data, s.data(), m_length+1);
}

string::~string()
{
clear();
}

void string::clear()
{
m_length = 0;
if (m_data)
delete [] m_data;
m_data = NULL;
}

const string & string::operator =(const char *s)
{
clear();
m_length = strlen(s);
m_data = new char[m_length+1];
memcpy(m_data, s, m_length+1);
return *this;
}

const string & string::operator =(const string &s)
{
clear();
m_length = s.length();
m_data = new char[m_length+1];
memcpy(m_data, s.data(), m_length+1);
return *this;
}

bool string::operator == (const char *s) const
{
return strcmp(m_data, s) == 0;
}

bool string::operator == (const string &s) const
{
return m_length == s.length() && strcmp(m_data, s.data()) == 0;
}

bool string::operator < (const char *s) const
{
return strcmp(m_data, s) < 0;
}

bool string::operator < (const string &s) const
{
return strcmp(m_data, s.data()) < 0;
}

bool string::operator > (const char *s) const
{
return strcmp(m_data, s) < 0;
}

bool string::operator > (const string &s) const
{
return strcmp(m_data, s.data()) < 0;
}