Vector的实现__2018.06.14

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本文介绍了一个自定义的Vector容器类实现，包括基本操作如push_back、pop_back、resize等，以及迭代器的设计与实现。此外，还展示了如何利用NgxMemPool进行内存管理。

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代码：Vector0.h

#ifndef VECTOR0_H
#define VECTOR0_H
#include "Ngx_pool.h"
#include <iostream>
using namespace std;

template<typename T>
class myallocater
{
public:
	//construct构造  destroy析构
	//allocate开辟内存 deallocate释放内存
	myallocater() :count(0) {}
	void construct(void *ptr, const T &val)
	{
		new (ptr)T(val);
	}
	void destroy(T *ptr)
	{
		ptr->~T();
	}
	//开辟内存
	void* allocate(u_int size)
	{
		if (0 == count)
		{
			p.ngx_create_pool(4096);
			++count;
		}
		return p.ngx_palloc(size);
	}
	//释放内存
	void deallocate(void *ptr)
	{
		count = 0;
		p.ngx_destroy_pool();
	}
private:
	NgxMemPool p;
	int count;
};
template<typename T,typename Allocator=myallocater<T>>
class Vector
{
public:
	typedef T value_type;
	//template<typename T>
	//默认构造的vector，底层没分配过内存
	Vector() :mpVec(NULL), mSize(0), mCur(0) {}
	Vector(int size, const T &val = T())
		:mSize(size), mCur(0)
	{
		mpVec = (T*)_allocator.allocate(mSize*sizeof(T));
		for (int i = 0; < msize; ++i)
		{
			_allocator.construct(mpVec + i, val);
		}
	}
	//拷贝构造
	Vector(const Vector<T> &src)
	{
		if (0 == src.mSize)
		{
			mpVec = (T*)_allocator.allocate(1 * sizeof(T));
			mSize = 1;
			mCur = 0;
		}
		else
		{
			T *p = (T*)_allocator.allocate(src.mSize * sizeof(T));
			for (int i = 0; i < src.mCur; ++i)
			{
				_allocator.construct(p + i, src.mpVec[i]);
			}
			for (int i = 0; i < mCur; ++i)
			{
				_allocator.destroy(&mpVec[i]);
			}
			mSize = src.mSize;
			mCur = src.mCur;
			mpVec = p;
		}
	}
	//operator=
	Vector<T>& operator=(const Vector<T> &src)
	{
		if (this == &src)
			throw "error";
		for (int i = 0; i < mCur; ++i)
		{
			_allocator.destroy(&mpVec[i]);
		}
		mpVec = (T*)_allocator.allocate(src.mSize * sizeof(T));
		for (int i = 0; i < src.mCur; ++i)
		{
			_allocator.construct(mpVec + i, src.mpVec[i]);
		}
		mSize = src.mSize;
		mCur = src.mCur;
	}
	T& operator[](int index)
	{
		if (empty())
			throw "error";
		return mpVec[index];
	}
	~Vector()
	{
		if (!empty())
		{
			for (int i = 0; i < mCur; ++i)
			{
				_allocator.destroy(&mpVec[i]);
			}
			_allocator.deallocate(mpVec);
		}
	}

	//末尾添加元素
	void push_back(const T &val)
	{
		if (full())
			reSize();
		_allocator.construct(mpVec + mCur++, val);
	}
	//末尾删除
	void pop_back()
	{
		_allocator.destroy(&mpVec[--mCur]);
	}



	T front()const { return mpVec[0]; }
	T back()const { return mpVec[mCur - 1]; }
	int size()const { return mCur; }
	bool full()const { return mCur == mSize; }
	bool empty()const { return 0 == mSize; }

	//内存以2倍方式增长
	void reSize()
	{
		if (empty())
		{
			mpVec = (T*)_allocator.allocate(1 * sizeof(T));
			mSize = 1;
			mCur = 0;
		}
		else
		{
			T *p = (T*)_allocator.allocate(mSize * 2 * sizeof(T));
			for (int i = 0; i < mCur; ++i)
			{
				_allocator.construct(p + i, mpVec[i]);
			}
			for (int i = 0; i<mCur; ++i)
			{
				_allocator.destroy(&mpVec[i]);
			}
			mSize *= 2;
			mpVec = p;
		}
	}
	//定义当前容器的迭代器类型
	class iterator
	{
	public:
		typedef T value_type;
		iterator(T *ptr = NULL) :p(ptr) {}
		bool operator!=(const iterator &it)const { return p != it.p; }
		bool operator==(const T &val)const { return *p == val; }
		void operator=(const iterator &src) { return *p == *src.p; }
		void operator++() { ++p; }
		void operator--(int) { --p; }
		T& operator*() { return *p; }
		iterator operator+(const int size)const { return iterator(p + size); }
		iterator operator-(const int size)const { return iterator(p - size); }
		bool operator<(const iterator &src)const { return p < src.p; }
		bool operator>(const iterator &src)const { return p > src.p; }
		int operator-(const iterator &src)const { return p - src.p; }
		T& operator[](const int index) { return p[index]; }
	private:
		T *p;
	};
	iterator begin()const { return iterator(mpVec); }
	iterator end()const { return iterator(mpVec + mCur); }

	/*
	C++17次课作业：完成下面的三个接口
	在it迭代器的位置，插入val元素
	it位置合法：it在【first，last】范围
	特殊情况：容器已经满了，插入要先扩容
	it位置不合法: 插入失败，抛异常
	*/
	void insert(iterator &it, const T &val)
	{
		if (it < begin() || it > end())
			throw "error";
		if (this->full())
			this->reSize();
		*it = val;
	}
	/*
	删除的容器，按值删除，按迭代器删除
	*/
	void erase(const T &val)
	{
		iterator it = this->begin();
		for (; it != this->end(); ++it)
		{
			if (*it == val)
			{
				iterator tmp(it + 1);
				for (; tmp != end(); ++tmp)
					*(tmp - 1) = *tmp;
				_allocator.destroy(mpVec + mCur - 1);
			}
		}
		--mCur;
	}
	void erase(const iterator &it)
	{
		if (it < begin() || it > end())
			throw "error";
		iterator tmp(it + 1);
		for (; tmp != end(); ++tmp)
			*(tmp - 1) = *tmp;
		_allocator.destroy(mpVec + mCur - 1);
		--mCur;
	}
private:
	T *mpVec;
	int mSize;
	int mCur;
	Allocator _allocator;
};

main.cpp

#include "Ngx_pool.h"
#include "Vector0.h"
#include <iostream>
#include <vld.h>
#include <Windows.h>
#include <time.h>
using namespace std;
template<typename Container>
void showContainer(Container &con)
{
	Container::iterator it = con.begin();
	for (; it != con.end(); ++it)
	{
		cout << *it << " ";
	}
	cout << endl;
}
int main1()
{
	Vector<int> MyIntVector;
	for (int i = 0; i < 10; ++i)
	{
		MyIntVector.push_back(i);
	}
	showContainer(MyIntVector);
	return 0;
}
int main(int argc, char* argv[])
{
	Vector<int> vec1, vec2;

	srand(time(0));
	for (int i = 0; i < 10; ++i)
	{
		vec1.push_back(rand() % 100);
		vec2.push_back(rand() % 100);
	}
	//默认从小到大排序   vector<int>::iterator  list<int>::iteartor
	//showContainer(vec1);

	/*vec1.insert(vec1.begin(),99);

	vec1.erase(vec1.begin());
	showContainer(vec1);*/

	//由小到大
	//mysort(vec1.begin(), vec1.end(),smallpfunc<int>);
	cout << "vec1:";
	showContainer(vec1);
	cout << "vec2:";
	showContainer(vec2);

	//Vector<int>::iterator it = myfind(vec1.begin(),vec1.end(),20);

	


	/*
	需要一种通用的方式，来遍历任何的容器   operator[]做不到的
	通用： 怎么通用？是使用方式通用呢？还是所有容器共用一个迭代器呢？
	数组operator[]
	链表
	二维数组
	哈希表
	红黑树

	迭代器和容器是一一对应的，所以在设计上，把迭代器这个类，设计成容器类型的嵌套类性
	*/
	/*
	1.需要在容器里面定义嵌套类性  iterator
	2.给容器提供begin方法     iterator begin();  把容器第0号位元素的迭代器返回回去
	3.给容器提供end方法       iterator end();    把容器末尾元素后继位置的迭代器返回回去
	4.给迭代器提供operator!=
	5.给迭代器提供operator++()
	6.给迭代器提供operator*()
	*/
	/*Vector<int>::iterator it = vec1.begin();
	for (; it != vec1.end(); ++it)
	{
	cout << *it << " ";
	}
	cout << endl;*/

	return 0;
}

Ngx_pool.h

#ifndef NGX_POOL_H
#define NGX_POOL_H
typedef unsigned char u_char;
typedef unsigned int u_int;
typedef struct ngx_pool_s ngx_pool_t;
typedef struct ngx_pool_large_s ngx_pool_large_t;
const int MAX = 4096;

const int NGX_ALIGNMENT = sizeof(unsigned long);
#define ngx_align_ptr(p, a)\
	(u_char *) (((unsigned int) (p) + ((unsigned int) a - 1)) & ~((unsigned int) a - 1))


typedef struct
{
	u_char		*last;
	u_char		*end;
	ngx_pool_t	*next;
	u_int		failed;
}ngx_pool_data_t;

struct ngx_pool_s
{
	ngx_pool_data_t		d;
	ngx_pool_t			*current;//指向当前内存的指针。
	ngx_pool_large_t	*large;
};
struct ngx_pool_large_s
{
	ngx_pool_large_t	*next;
	void				*alloc;
};
class NgxMemPool
{
public:
	//创建ngx内存池
	void ngx_create_pool(u_int size);
	//销毁ngx内存池
	void ngx_destroy_pool();
	//重置内存池
	void ngx_reset_pool();
	//开辟内存，对齐
	void* ngx_palloc(u_int size);
	//开辟内存，不对齐
	void* ngx_pnalloc(u_int size);
	//把内存归还给内存池
	bool ngx_pfree(void *p);

	//开辟小块内存
	void *ngx_palloc_small(u_int size, int align);
	//开辟新的小块
	void *ngx_palloc_block(u_int size);
	//开辟大块内存
	void *ngx_palloc_large(u_int size);
private:
	ngx_pool_t *_pool;
};
#endif

Ngx_pool.cpp

#include "Ngx_pool.h"
#include "Vector0.h"
#include <iostream>
#include <vld.h>
#include <Windows.h>
#include <time.h>

using namespace std;
//创建ngx内存池
void NgxMemPool::ngx_create_pool(u_int size)
{
	_pool = (ngx_pool_t*)malloc(size);
	if (NULL == _pool)
	{
		return;
	}
	_pool->d.last = (u_char*)_pool + sizeof(ngx_pool_t);
	_pool->d.end = (u_char*)_pool + size;
	_pool->d.next = NULL;
	_pool->d.failed = 0;
	_pool->current = _pool;//当前指针位置
	_pool->large = NULL;
}
//销毁ngx内存池
void NgxMemPool::ngx_destroy_pool()
{
	//先释放large指向外部开辟的大内存
	ngx_pool_large_t	*pLarge;
	for (pLarge = _pool->large; pLarge != NULL; pLarge = pLarge->next)
	{
		if (pLarge->alloc)
		{
			free(pLarge->alloc);
			pLarge->next = NULL;
		}
	}
	ngx_pool_t			*p;
	ngx_pool_t			*n;

	for (p = _pool, n = _pool->d.next;; p = n)
	{
		free(p);
		p = NULL;
		if (NULL == n)
		{
			break;
		}
	}

}
//重置内存池
void NgxMemPool::ngx_reset_pool()
{
	ngx_pool_large_t	*pLarge;//指向内存池外开辟的大块内存
	ngx_pool_t			*p;//指向内存池的指针
	//先释放内存池外开辟的大块内存
	for (pLarge = _pool->large; pLarge != NULL; pLarge = pLarge->next)
	{
		if (pLarge->alloc)
		{
			free(pLarge->next);
			pLarge->alloc = NULL;
		}
	}
	//再重置内存池中的内存
	for (p = _pool; p; p = p->d.next)
	{
		p->d.last = (u_char*)p + sizeof(ngx_pool_t);
	}
	_pool->current = _pool;
}
//开辟内存，对齐
void* NgxMemPool::ngx_palloc(u_int size)
{
	if (size <= MAX)
	{
		return ngx_palloc_small(size,0);
	}
	return ngx_palloc_large(size);
}
//把内存归还给内存池
bool NgxMemPool::ngx_pfree(void *p)
{
	ngx_pool_large_t *pLarge;
	//只检查是否是大内存块，如果是大内存块则释放
	for (pLarge = _pool->large; pLarge; pLarge->next)
	{
		if (p == pLarge->alloc)
		{
			free(pLarge->alloc);
			pLarge->alloc = NULL;
			return true;
		}
	}
	return false;
}
//开辟小块内存
void*NgxMemPool::ngx_palloc_small(u_int size,int align)
{
	u_char		*m;
	ngx_pool_t	*p;
	p = _pool->current;
	do {
		m = p->d.last;
		if (align)
		{
			m = ngx_align_ptr(m,NGX_ALIGNMENT);
		}
		if ((u_int)(p->d.end - m) >= size)
		{
			p->d.last = m + size;
			return m;
		}
	} while (p);
	//开辟内存过大，内存池中没有合适的内存，则重新开辟指定大小的内存块
	return ngx_palloc_block(size);
}
//开辟新的小内存块
void *NgxMemPool::ngx_palloc_block(u_int size)
{
	u_int	psize;
	u_char	*m;
	ngx_pool_t	*pnew, *t;

	psize = (u_int)(_pool->d.end-(u_char*)_pool);
	m = (u_char*)malloc(psize);
	if (NULL == m)
		return NULL;

	pnew = (ngx_pool_t*)m;
	pnew->d.end = m + psize;
	pnew->d.next = NULL;
	pnew->d.failed = 0;

	/*将m指针移动数据头的大小位置*/
	m += sizeof(ngx_pool_data_t);
	/*进行内存对齐计算*/
	m = ngx_align_ptr(m, NGX_ALIGNMENT);
	/*设置新内存块的last，即申请使用size大小的内存*/
	pnew->d.last = m + size;

	/*对链表进行整理current指针要重新确认*/

	/*这里循环用来寻找最后一个节点 */
	for (t = _pool->current; t->d.next != NULL; t = t->d.next)
	{
		if (t->d.failed++ > 4)	//failed的值只在此处被修改
		{
			t->current = t->d.next;	//失败4次以上移动current指针  
		}
	}
	/*在循环中next可能会指向NULL 所以current也可能会被置NULL*/
	t->d.next = pnew;  //将这次分配的内存块pnew加入该内存池链表中

					   /*对current确认为NULL时则重新确认位置*/
	_pool->current = t->current ? t->current : pnew;

	return m;
}
//开辟大块内存
void *NgxMemPool::ngx_palloc_large(u_int size)
{
	void              *p;
	u_int         n = 0;
	ngx_pool_large_t  *large;

	// 直接在系统堆中分配一块空间  
	p = (void *)malloc(size);
	if (p == NULL)
	{
		return NULL;
	}

	// 查找到一个空的large区，如果有，则将刚才分配的空间交由它管理  
	for (large = _pool->large; large; large = large->next)
	{
		if (NULL == large->alloc)
		{
			large->alloc = p;
			return p;
		}
		if (n++ > 3)
		{
			break;
		}
	}
	//为了提高效率， 如果在三次内没有找到空的large结构体，则创建一个
	large = (ngx_pool_large_t*)ngx_palloc_small(size, 1);
	if (NULL == large)
	{
		free(p);
		return NULL;
	}
	large->alloc = p;
	large->next = _pool->large;
	_pool->large = large;
	return p;
}