C++String模拟实现
实际上string没什么可讲，主要是对string函数的运用与理解，与其写库函数如何用，不如直接去看c++库函数来得好。
以下是自己实现string功能函数。但没对string库中的全部函数进行实现，而是实现主要使用的。
.cpp内是用来测试函数功能是否正确。
.h内是用来实现string
.CPP
#include"String.h"
int main()
{
moxuan::string s1;
cout << s1.c_str() << endl;
moxuan::string s2("abcd");
cout << s2.c_str() << endl;
//s1 = s2;
cout << s1.c_str() << endl;
cout << s2.c_str() << endl;
s2.push_back('a');
s2.append("11223344");
cout << s2.c_str() << endl;
//s1.push_back('a');
s1.append("aabbccdd");
cout << s1.c_str() << endl;
s1.resize(10, 'a');
cout << s1.c_str() << endl;
s2.resize(20, 'v');
cout << s2.c_str() << endl;
s1 += 'a';
s1.push_back('a');
cout << s1.c_str() << endl;
s2 += "99887766";
cout << s2.c_str() << endl;
moxuan::string::iterator it = s2.begin();
while(it!=s2.end())
{
cout << *it;
*it++;
}
cout << endl;
moxuan::string::const_iterator cit = s2.begin();
while (cit != s2.end())
{
cout << *cit;
*cit++;
}
cout << endl;
s2.inster(100, 'a');
for (auto ch:s2)
{
cout << ch;
}
cout << endl;
s2.inster(0, 'p');
s2.inster(24, 'G');
for (auto ch : s2)
{
cout << ch;
}
cout << endl;
s2.inster(100, "ooooooo");
s2.inster(0, "kkkkkk");
s2.inster(12, "yyyyyyy");
for (auto ch : s2)
{
cout << ch;
}
cout << endl;
s2.erase(0, 5);
for (auto ch : s2)
{
cout << ch;
}
cout << endl;
cout << s2 << endl;
moxuan::string s3;
cin >> s3;
cout << s3;
return 0;
}.h
#define CRT_SECURE_NO_WARNINGS
#pragma once
#include
#include
#include
using namespace std;
namespace moxuan
{
class string
{
public:
typedef char* iterator;
typedef const char* const_iterator;
iterator& begin()
{
return _str;
}
iterator end()
{
return _str + _size;
}
const_iterator begin()const
{
return _str;
}
const_iterator end()const
{
return _str + _size;
}
//s("abc")
string(const char* s = "")
:_size(strlen(s))
, _capacity(_size)
{
_str = new char[_capacity + 1];
strcpy(_str, s);
}
//s(s1)
string(const string& s)
:_size(s._size)
, _capacity(s._capacity)
{
_str = new char[_capacity + 1];
strcpy(_str, s._str);
}
//s=s1
string& operator=(const string& s)
{
if (this != &s)
{
_size = s._size;
_capacity = s._capacity;
char* tmp = new char[_capacity + 1];
delete[]_str;
strcpy(tmp, s._str);
_str = tmp;
}
return *this;
}
~string()
{
if (_str)
{
delete[]_str;
_str = nullptr;
_size = _capacity = 0;
}
}
const char* c_str() const
{
return _str;
}
char& operator[](size_t n)
{
assert(n <= _capacity);
return _str[n];
}
size_t size()const
{
return _size;
}
size_t capacity()const
{
return _capacity;
}
string& operator+=(const char ch)
{
push_back(ch);
return *this;
}
string& operator+=(const char* s)
{
append(s);
return *this;
}
//扩容
void reserve(size_t n)
{
if (n > _capacity)
{
char* tmp = new char[n+1];
strcpy(tmp, _str);
delete[]_str;
_str = tmp;
_capacity = n;
}
}
void push_back(const char ch)
{
if (_size == _capacity)
{
reserve(_capacity == 0 ? 4 : _capacity * 2 + 1);
}
_str[_size] = ch;
_str[++_size] = '\0';
}
void append(const char* s)
{
size_t len = _size + strlen(s);
if (len > _capacity)
{
reserve(len);
}
strcpy(_str+_size, s);
_size = len;
}
void resize(size_t n, const char ch)
{
if (n < _size)
{
_size = n;
_str[n] = '\0';
}
else
{
if (n > _capacity)
{
reserve(_capacity * 2);
}
for (size_t i = _size; i = _size)
{
_str[_size] = ch;
}
else
{
size_t end = _size+1;
while (pos < end)
{
_str[end] = _str[end-1];
--end;
}
_str[pos] = ch;
}
++_size;
_str[_size] = '\0';
return *this;
}
string& inster(size_t pos,const char* str)
{
size_t len = strlen(str);
if (_size + len > _capacity)
{
reserve(_size + strlen(str));
}
if (pos >= _size)
{
this->append(str);
}
else
{
size_t end = _size + len+1;
while (pos < end)
{
_str[end] = _str[end-len];
--end;
}
strncpy(_str+pos,str,len);
_size += len;
++_size;
_str[_size] = '\0';
}
return *this;
}
void erase(size_t pos, size_t len=npos)
{
assert(pos < _size);
if (pos == npos || pos + len > _size)
{
_str[pos] = '\0';
_size = pos;
}
else
{
size_t end = pos + len;
while (end <= _size)
{
_str[end - len] = _str[end];
++end;
}
_size -= len;
_str[_size] = '\0';
}
}
size_t find(char ch,size_t pos = 0)
{
for (; pos <= _size; pos++)
{
if (_str[pos] == ch)
{
return pos;
}
}
}
size_t find(char* str, size_t pos = 0)
{
const char* p = strstr(_str + pos, str);
if (p == nullptr)
{
return npos;
}
else
{
return p - _str;
}
}
private:
char* _str;
size_t _size;
size_t _capacity;
const static size_t npos;
};
const size_t string::npos = -1;
ostream& operator<<(ostream& out,const string& s)
{
for (auto ch : s)
{
out << ch;
}
return out;
}
istream& operator>>(istream& in, string& s)
{
//这里创建数组为了防止单一的实现，重复调用。通过提取放入数组，结束再赋值。提高效率
char ch;
ch = in.get();
char buff[128] = { '\0' };
size_t i = 0;
while (ch != ' ' && ch != '\n')
{
buff[i++] = ch;
if (i == 127)
{
s += buff;
memset(buff, '\0', 128);
i = 0;
}
ch = in.get();
}
s += buff;
return in;
}
bool operator<(const string& s1, const string& s2)
{
return strcmp(s1.c_str(), s2.c_str()) < 0;
}
bool operator==(const string& s1, const string& s2)
{
return strcmp(s1.c_str(), s2.c_str()) == 0;
}
bool operator<=(const string& s1, const string& s2)
{
return s1 < s2 || s1 == s2;
}
bool operator>(const string& s1, const string& s2)
{
return strcmp(s1.c_str(), s2.c_str()) > 0;
}
bool operator>=(const string& s1, const string& s2)
{
return s1 > s2 || s1 == s2;
}
bool operator!=(const string& s1, const string& s2)
{
return !(s1 == s2);
}
};