看到今天，终于自己动手写了一个自己的vector，我这个版本的vector只有vector主要的一些操作，包括原版vector的所有构造函数，begin(),end(),size(),capacity(),empty(),erase(),clear(),pop_back,push_back(),重载了[],==,!=操作符等.其中有个比较重要的insert()，我暂时没写。其实和push_back差不多，只不过考虑的条件更多，代码更复杂，逻辑并不难。废话不多说，现将我的vector代码贴出来：
/*
自己动手实现vector，不用alloc配置器，就用一般的 malloc/free
*/
#ifndef __MY_VECTOR_H
#define __MY_VECTOR_H
#include<cstddef>
#include "construct.h"
template<class T>
class My_vector
{
public:
typedef T value_type;
typedef value_type* pointer;
typedef value_type* iterator;
typedef value_type& reference;
typedef const value_type* const_pointer;
typedef const value_type* const_iterator;
typedef const value_type& const_reference;
typedef size_t size_type;
protected:
void __allocate_and_fill(size_type n, const T& value) //分配空间，并填充初始值
{
iterator result = (iterator)malloc(n*sizeof(T));
if( != result)
{
//申请内存成功，在得到的内存上创建对象！
start = result;
end_of_storage = start + n;
finish = end_of_storage;
while(n--)
{
construct(result,value); //在内存上，一个个的进行构造对象
++result;
}
}
else
{
cout << "内存不足，程序终止！" << endl;
exit();
}
}
iterator __allocate_and_copy(iterator first,iterator last,size_type n) //分配空间，并复制值到空间中
{
iterator result = (iterator)malloc(n*sizeof(T));
iterator _start = result;
if( != result)
{
while(n--)
{
construct(result,*first);
++result;
++first;
}
cout << endl;
}
else
{
cout << "内存不足，程序终止！" << endl;
exit();
}
return _start;
}
//将first到last迭代器之间[first,last)的元素拷贝到_start开始的内存中
iterator __copy(iterator first,iterator last,iterator _start)
{
while(first < last)
{
*_start++ = *first++;
}
return _start;
}
public:
//返回首元素指针
iterator begin() { return start; }
const iterator begin() const { return start;}
//返回尾元素下一个位置的指针
iterator end() { return finish; }
const iterator end() const { return finish;}
//容器的大小
size_type size() const { return (size_type)(end() - begin()); }
//容器的实际大小
size_type capacity() const { return (size_type)(end_of_storage - begin()); }
//判断容器是否为空
bool empty() { return begin() == end(); }
//typedef ptrdiff_t difference_type;
//默认构造函数
My_vector():start(),finish(),end_of_storage(){ cout << "默认构造函数，不分配空间" << endl;}
//构造函数重载 C c(n,t):
My_vector(size_type n, const T& value) { __allocate_and_fill(n, value);}
My_vector(int n, const T& value) { __allocate_and_fill(n, value); }
My_vector(long n, const T& value) { __allocate_and_fill(n, value); }
//构造函数重载 C c(n):
My_vector(size_type n) { __allocate_and_fill(n, T()); }
My_vector(int n) { __allocate_and_fill(n, T()); }
My_vector(long n) { __allocate_and_fill(n, T()); }
//构造函数重载 C c2(c1)
My_vector(const My_vector<T>& mv)
{
start = __allocate_and_copy(mv.begin(), mv.end(),mv.end() - mv.begin());
finish = start + (mv.end() - mv.begin());
end_of_storage = finish;
}
//构造函数重载 C c2(b,e)
My_vector(const iterator& b,const iterator& e)
{
start = __allocate_and_copy(b,e,size_type(e - b + ));
finish = start + (e - b + );
end_of_storage = finish;
}
//元素操作
//删除最后一个元素
void pop_back()
{
if(!empty())
{
--finish;
destroy(finish);
}
}
//删除指定位置上的元素,返回指向删除元素的迭代器
iterator erase(iterator position)
{
if(position > begin() && position < end())
{
__copy(position + ,finish,position);
}
--finish;
destroy(finish);
return position;
}
//重载erase,根据迭代器范围删除
iterator erase(iterator first,iterator last)
{
iterator i = __copy(last,finish,first);
destroy(i,finish);
finish -= (last - first);
return first;
}
//清除全部元素
void clear()
{
erase(begin(),end());
}
//在vector 容器后面增加一个元素
void push_back(const T& value)
{
if(finish != end_of_storage) //如果还有备用空间
{
construct(finish,value);
++finish;
}
else
{
//重新申请空间
const size_type old_size = size();
const size_type new_size = (old_size == )?:*old_size;
iterator new_start = (iterator)malloc(new_size * sizeof(T));
iterator new_finish = new_start;
//内存的分配要有原子性，即:要么全部成功，要么全部失败。
try{
//1.将原内容拷贝到新的vector
//2.为新的元素设定初值x
//3.调整new_finish
for(iterator it = begin();it < end(); ++it)
{
//cout << "it:" << *it << " ";
construct(new_finish++,*it);
}
construct(new_finish,value);
++new_finish;
}
catch(...)
{
//如果失败了
destroy(new_start,new_finish);
//删除申请到的内存
free(new_start);
new_start = new_finish = NULL;
throw; //抛出异常
} //析构并释放原vector
destroy(begin(),end());
//删除内存
free(start);
//调整迭代器，指向新的vector
start = new_start;
finish = new_finish;
end_of_storage = new_start + new_size;
}
}
//insert--这个好多代码，不想写
void insert(iterator position,size_type n,const T& value)
{
}
void insert(iterator position,const T& value)
{
insert(position,,value);
}
//重载操作符
reference operator[](size_type n){ return *(begin() + n); }
const_reference operator[](size_type n) const{ return *(begin() + n); }
bool operator==(const My_vector& mv)
{
if(mv.size() != size())
return false;
for(iterator it = mv.begin();it < mv.end(); ++it)
{
if(*it != *(begin() + (it - mv.begin())))
break;
}
if(it == mv.end())
return true;
else
return false;
}
bool operator!=(const My_vector& mv)
{
return !(operator==(mv));
}
private:
iterator start;
iterator finish;
iterator end_of_storage;
};
#endif
其中包含的 "construct.h" 文件代码如下：
template <class T>
inline void destroy(T* pointer) {
pointer->~T(); //只是做了一层包装，将指针所指的对象析构---通过直接调用类的析构函数
} template <class T1, class T2>
inline void construct(T1* p, const T2& value) {
new (p) T1(value); //用placement new在 p 所指的对象上创建一个对象，value是初始化对象的值。
} template <class ForwardIterator> //destroy的泛化版，接受两个迭代器为参数
inline void destroy(ForwardIterator first, ForwardIterator last) {
for ( ; first < last; ++first)
destroy(&*first);
} inline void destroy(char*, char*) {} //针对 char * 的特化版
inline void destroy(wchar_t*, wchar_t*) {} //针对 wchar_t*的特化版
现将测试My_vector的代码也贴出来：
#include<iostream> using namespace std; int main()
{
My_vector<int>::iterator it; //默认构造函数
My_vector<int> mvec;
cout << mvec.begin() << " " << mvec.end() << endl;
cout << "size=" << mvec.size() << endl;
cout << "capacity=" << mvec.capacity() << endl;
for(it = mvec.begin();it < mvec.end(); ++it)
{
cout << *it << " ";
}
cout << endl;
//根据元素个数和一个初始值的构造函数
My_vector<int> mvecnt(,);
cout << mvecnt.begin() << " " << mvecnt.end() - << endl;
cout << "size=" << mvecnt.size() << endl;
cout << "capacity=" << mvecnt.capacity() << endl;
for(it = mvecnt.begin();it < mvecnt.end(); ++it)
{
cout << *it << " ";
}
cout << endl; My_vector<int> mvecnt1(,);
cout << mvecnt1.begin() << " " << mvecnt1.end() - << endl;
cout << "size=" << mvecnt1.size() << endl;
cout << "capacity=" << mvecnt1.capacity() << endl;
for(it = mvecnt1.begin();it < mvecnt1.end(); ++it)
{
cout << *it << " ";
}
cout << endl;
mvecnt1.pop_back();
cout << "size=" << mvecnt1.size() << endl;
//测试 != 和 ==
if(mvecnt != mvecnt1)
cout << "mvecnt != mvecnt1" << endl;
else if(mvecnt == mvecnt1)
cout << "mvecnt == mvecnt1" << endl;
//根据元素个数的构造函数
My_vector<int> mvecn();
cout << mvecn.begin() << " " << mvecn.end() - << endl;
cout << "size=" << mvecn.size() << endl;
cout << "capacity=" << mvecn.capacity() << endl;
for(it = mvecn.begin();it < mvecn.end(); ++it)
{
cout << *it << " ";
}
cout << endl;
//复制构造函数
My_vector<int> mvecc(mvec);
cout << mvecc.begin() << " " << mvecc.end() - << endl;
cout << "size=" << mvecc.size() << endl;
cout << "capacity=" << mvecc.capacity() << endl;
for(it = mvecc.begin();it < mvecc.end(); ++it)
{
cout << *it << " ";
}
cout << endl;
//根据两个迭代器构造函数
int arr[] = {,,,,,};
My_vector<int> mvecbe(&arr[],&arr[]);
cout << mvecbe.begin() << " " << mvecbe.end() - << endl;
cout << "size=" << mvecbe.size() << endl;
cout << "capacity=" << mvecbe.capacity() << endl;
for(it = mvecbe.begin();it < mvecbe.end(); ++it)
{
cout << *it << " ";
}
cout << endl;
//以上5个构造函数测试完毕
//测试 pop_back()
mvecbe.pop_back();
cout << "size=" << mvecbe.size() << endl;
cout << "capacity=" << mvecbe.capacity() << endl;
for(it = mvecbe.begin();it < mvecbe.end(); ++it)
{
cout << *it << " ";
}
cout << endl;
//测试 erase();
mvecbe.erase(mvecbe.begin() + ,mvecbe.begin() + );
cout << "size=" << mvecbe.size() << endl;
cout << "capacity=" << mvecbe.capacity() << endl;
for(it = mvecbe.begin();it < mvecbe.end(); ++it)
{
cout << *it << " ";
}
cout << endl;
//测试clear()
mvecbe.clear();
cout << "size=" << mvecbe.size() << endl;
cout << "capacity=" << mvecbe.capacity() << endl;
for(it = mvecbe.begin();it < mvecbe.end(); ++it)
{
cout << *it << " ";
}
cout << endl;
cout << mvecbe[] << endl;
//以下测试push_back()
mvec.push_back();
cout << mvec.begin() << " " << mvec.end() << endl;
cout << "size=" << mvec.size() << endl;
cout << "capacity=" << mvec.capacity() << endl;
for(it = mvec.begin();it < mvec.end(); ++it)
{
cout << *it << " ";
}
cout << endl;
mvec.push_back();
cout << "size=" << mvec.size() << endl;
cout << "capacity=" << mvec.capacity() << endl;
for(it = mvec.begin();it < mvec.end(); ++it)
{
cout << *it << " ";
}
cout << endl;
mvec.push_back();
cout << "size=" << mvec.size() << endl;
cout << "capacity=" << mvec.capacity() << endl;
for(it = mvec.begin();it < mvec.end(); ++it)
{
cout << *it << " ";
}
cout << endl;
mvec.push_back();
cout << "size=" << mvec.size() << endl;
cout << "capacity=" << mvec.capacity() << endl;
for(it = mvec.begin();it < mvec.end(); ++it)
{
cout << *it << " ";
}
cout << endl;
mvec.push_back();
cout << "size=" << mvec.size() << endl;
cout << "capacity=" << mvec.capacity() << endl;
for(it = mvec.begin();it < mvec.end(); ++it)
{
cout << *it << " ";
}
cout << endl;
return ;
}
代码可能比较长，也比较乱。初始尝试写vector，以后会将vector的功能补全，并将其写成一个可以直接调用的头文件！