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
*/
1 #ifndef __MY_VECTOR_H
2 #define __MY_VECTOR_H
3 #include<cstddef>
4 #include "construct.h"
5 template<class T>
6 class My_vector
7 {
8 public:
9 typedef T value_type;
10 typedef value_type* pointer;
11 typedef value_type* iterator;
12 typedef value_type& reference;
13 typedef const value_type* const_pointer;
14 typedef const value_type* const_iterator;
15 typedef const value_type& const_reference;
16 typedef size_t size_type;
17 protected:
18 void __allocate_and_fill(size_type n, const T& value) //分配空间，并填充初始值
19 {
20 iterator result = (iterator)malloc(n*sizeof(T));
21 if(0 != result)
22 {
23 //申请内存成功，在得到的内存上创建对象！
24 start = result;
25 end_of_storage = start + n;
26 finish = end_of_storage;
27 while(n--)
28 {
29 construct(result,value); //在内存上，一个个的进行构造对象
30 ++result;
31 }
32 }
33 else
34 {
35 cout << "内存不足，程序终止！" << endl;
36 exit(0);
37 }
38 }
39 iterator __allocate_and_copy(iterator first,iterator last,size_type n) //分配空间，并复制值到空间中
40 {
41 iterator result = (iterator)malloc(n*sizeof(T));
42 iterator _start = result;
43 if( 0 != result)
44 {
45 while(n--)
46 {
47 construct(result,*first);
48 ++result;
49 ++first;
50 }
51 cout << endl;
52 }
53 else
54 {
55 cout << "内存不足，程序终止！" << endl;
56 exit(0);
57 }
58 return _start;
59 }
60 //将first到last迭代器之间[first,last)的元素拷贝到_start开始的内存中
61 iterator __copy(iterator first,iterator last,iterator _start)
62 {
63 while(first < last)
64 {
65 *_start++ = *first++;
66 }
67 return _start;
68 }
69 public:
70 //返回首元素指针
71 iterator begin() { return start; }
72 const iterator begin() const { return start;}
73 //返回尾元素下一个位置的指针
74 iterator end() { return finish; }
75 const iterator end() const { return finish;}
76 //容器的大小
77 size_type size() const { return (size_type)(end() - begin()); }
78 //容器的实际大小
79 size_type capacity() const { return (size_type)(end_of_storage - begin()); }
80 //判断容器是否为空
81 bool empty() { return begin() == end(); }
82 //typedef ptrdiff_t difference_type;
83 //默认构造函数
84 My_vector():start(0),finish(0),end_of_storage(0){ cout << "默认构造函数，不分配空间" << endl;}
85 //构造函数重载 C c(n,t):
86 My_vector(size_type n, const T& value) { __allocate_and_fill(n, value);}
87 My_vector(int n, const T& value) { __allocate_and_fill(n, value); }
88 My_vector(long n, const T& value) { __allocate_and_fill(n, value); }
89 //构造函数重载 C c(n):
90 My_vector(size_type n) { __allocate_and_fill(n, T()); }
91 My_vector(int n) { __allocate_and_fill(n, T()); }
92 My_vector(long n) { __allocate_and_fill(n, T()); }
93 //构造函数重载 C c2(c1)
94 My_vector(const My_vector<T>& mv)
95 {
96 start = __allocate_and_copy(mv.begin(), mv.end(),mv.end() - mv.begin());
97 finish = start + (mv.end() - mv.begin());
98 end_of_storage = finish;
99 }
100 //构造函数重载 C c2(b,e)
101 My_vector(const iterator& b,const iterator& e)
102 {
103 start = __allocate_and_copy(b,e,size_type(e - b + 1));
104 finish = start + (e - b + 1);
105 end_of_storage = finish;
106 }
107 //元素操作
108 //删除最后一个元素
109 void pop_back()
110 {
111 if(!empty())
112 {
113 --finish;
114 destroy(finish);
115 }
116 }
117 //删除指定位置上的元素,返回指向删除元素的迭代器
118 iterator erase(iterator position)
119 {
120 if(position > begin() && position < end())
121 {
122 __copy(position + 1,finish,position);
123 }
124 --finish;
125 destroy(finish);
126 return position;
127 }
128 //重载erase,根据迭代器范围删除
129 iterator erase(iterator first,iterator last)
130 {
131 iterator i = __copy(last,finish,first);
132 destroy(i,finish);
133 finish -= (last - first);
134 return first;
135 }
136 //清除全部元素
137 void clear()
138 {
139 erase(begin(),end());
140 }
141 //在vector 容器后面增加一个元素
142 void push_back(const T& value)
143 {
144 if(finish != end_of_storage) //如果还有备用空间
145 {
146 construct(finish,value);
147 ++finish;
148 }
149 else
150 {
151 //重新申请空间
152 const size_type old_size = size();
153 const size_type new_size = (old_size == 0)?1:2*old_size;
154 iterator new_start = (iterator)malloc(new_size * sizeof(T));
155 iterator new_finish = new_start;
156 //内存的分配要有原子性，即:要么全部成功，要么全部失败。
157 try{
158 //1.将原内容拷贝到新的vector
159 //2.为新的元素设定初值x
160 //3.调整new_finish
161 for(iterator it = begin();it < end(); ++it)
162 {
163 //cout << "it:" << *it << " ";
164 construct(new_finish++,*it);
165 }
166 construct(new_finish,value);
167 ++new_finish;
168 }
169 catch(...)
170 {
171 //如果失败了
172 destroy(new_start,new_finish);
173 //删除申请到的内存
174 free(new_start);
175 new_start = finish = NULL;
176 throw; //抛出异常
177 }
178
179 //析构并释放原vector
180 destroy(begin(),end());
181 //删除内存
182 free(start);
183 //调整迭代器，指向新的vector
184 start = new_start;
185 finish = new_finish;
186 end_of_storage = new_start + new_size;
187 }
188 }
189 //insert--这个好多代码，不想写
190 void insert(iterator position,size_type n,const T& value)
191 {
192 }
193 void insert(iterator position,const T& value)
194 {
195 insert(position,1,value);
196 }
197 //重载操作符
198 reference operator[](size_type n){ return *(begin() + n); }
199 const_reference operator[](size_type n) const{ return *(begin() + n); }
200 bool operator==(const My_vector& mv)
201 {
202 if(mv.size() != size())
203 return false;
204 for(iterator it = mv.begin();it < mv.end(); ++it)
205 {
206 if(*it != *(begin() + (it - mv.begin())))
207 break;
208 }
209 if(it == mv.end())
210 return true;
211 else
212 return false;
213 }
214 bool operator!=(const My_vector& mv)
215 {
216 return !(operator==(mv));
217 }
218 private:
219 iterator start;
220 iterator finish;
221 iterator end_of_storage;
222 };
223 #endif
其中包含的 "construct.h" 文件代码如下：
1 template <class T>
2 inline void destroy(T* pointer) {
3 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
4 }
5
6 template <class T1, class T2>
7 inline void construct(T1* p, const T2& value) {
8 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。
9 }
10
11 template <class ForwardIterator> //destroy的泛化版，接受两个迭代器为参数
12 inline void destroy(ForwardIterator first, ForwardIterator last) {
13 for ( ; first < last; ++first)
14 destroy(&*first);
15 }
16
17
18 inline void destroy(char*, char*) {} //针对 char * 的特化版
19 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：
1 #include<iostream>
2
3 using namespace std;
4
5 int main()
6 {
7 My_vector<int>::iterator it;
8
9 //默认构造函数
10 My_vector<int> mvec;
11 cout << mvec.begin() << " " << mvec.end() << endl;
12 cout << "size=" << mvec.size() << endl;
13 cout << "capacity=" << mvec.capacity() << endl;
14 for(it = mvec.begin();it < mvec.end(); ++it)
15 {
16 cout << *it << " ";
17 }
18 cout << endl;
19 //根据元素个数和一个初始值的构造函数
20 My_vector<int> mvecnt(2,9);
21 cout << mvecnt.begin() << " " << mvecnt.end() - 1 << endl;
22 cout << "size=" << mvecnt.size() << endl;
23 cout << "capacity=" << mvecnt.capacity() << endl;
24 for(it = mvecnt.begin();it < mvecnt.end(); ++it)
25 {
26 cout << *it << " ";
27 }
28 cout << endl;
29
30 My_vector<int> mvecnt1(2,9);
31 cout << mvecnt1.begin() << " " << mvecnt1.end() - 1 << endl;
32 cout << "size=" << mvecnt1.size() << endl;
33 cout << "capacity=" << mvecnt1.capacity() << endl;
34 for(it = mvecnt1.begin();it < mvecnt1.end(); ++it)
35 {
36 cout << *it << " ";
37 }
38 cout << endl;
39 mvecnt1.pop_back();
40 cout << "size=" << mvecnt1.size() << endl;
41 //测试 != 和 ==
42 if(mvecnt != mvecnt1)
43 cout << "mvecnt != mvecnt1" << endl;
44 else if(mvecnt == mvecnt1)
45 cout << "mvecnt == mvecnt1" << endl;
46 //根据元素个数的构造函数
47 My_vector<int> mvecn(4);
48 cout << mvecn.begin() << " " << mvecn.end() - 1 << endl;
49 cout << "size=" << mvecn.size() << endl;
50 cout << "capacity=" << mvecn.capacity() << endl;
51 for(it = mvecn.begin();it < mvecn.end(); ++it)
52 {
53 cout << *it << " ";
54 }
55 cout << endl;
56 //复制构造函数
57 My_vector<int> mvecc(mvec);
58 cout << mvecc.begin() << " " << mvecc.end() - 1 << endl;
59 cout << "size=" << mvecc.size() << endl;
60 cout << "capacity=" << mvecc.capacity() << endl;
61 for(it = mvecc.begin();it < mvecc.end(); ++it)
62 {
63 cout << *it << " ";
64 }
65 cout << endl;
66 //根据两个迭代器构造函数
67 int arr[6] = {1,2,3,4,5,6};
68 My_vector<int> mvecbe(&arr[0],&arr[5]);
69 cout << mvecbe.begin() << " " << mvecbe.end() - 1 << endl;
70 cout << "size=" << mvecbe.size() << endl;
71 cout << "capacity=" << mvecbe.capacity() << endl;
72 for(it = mvecbe.begin();it < mvecbe.end(); ++it)
73 {
74 cout << *it << " ";
75 }
76 cout << endl;
77 //以上5个构造函数测试完毕
78 //测试 pop_back()
79 mvecbe.pop_back();
80 cout << "size=" << mvecbe.size() << endl;
81 cout << "capacity=" << mvecbe.capacity() << endl;
82 for(it = mvecbe.begin();it < mvecbe.end(); ++it)
83 {
84 cout << *it << " ";
85 }
86 cout << endl;
87 //测试 erase();
88 mvecbe.erase(mvecbe.begin() + 1,mvecbe.begin() + 3);
89 cout << "size=" << mvecbe.size() << endl;
90 cout << "capacity=" << mvecbe.capacity() << endl;
91 for(it = mvecbe.begin();it < mvecbe.end(); ++it)
92 {
93 cout << *it << " ";
94 }
95 cout << endl;
96 //测试clear()
97 mvecbe.clear();
98 cout << "size=" << mvecbe.size() << endl;
99 cout << "capacity=" << mvecbe.capacity() << endl;
100 for(it = mvecbe.begin();it < mvecbe.end(); ++it)
101 {
102 cout << *it << " ";
103 }
104 cout << endl;
105 cout << mvecbe[0] << endl;
106 //以下测试push_back()
107 mvec.push_back(7);
108 cout << mvec.begin() << " " << mvec.end() << endl;
109 cout << "size=" << mvec.size() << endl;
110 cout << "capacity=" << mvec.capacity() << endl;
111 for(it = mvec.begin();it < mvec.end(); ++it)
112 {
113 cout << *it << " ";
114 }
115 cout << endl;
116 mvec.push_back(3);
117 cout << "size=" << mvec.size() << endl;
118 cout << "capacity=" << mvec.capacity() << endl;
119 for(it = mvec.begin();it < mvec.end(); ++it)
120 {
121 cout << *it << " ";
122 }
123 cout << endl;
124 mvec.push_back(4);
125 cout << "size=" << mvec.size() << endl;
126 cout << "capacity=" << mvec.capacity() << endl;
127 for(it = mvec.begin();it < mvec.end(); ++it)
128 {
129 cout << *it << " ";
130 }
131 cout << endl;
132 mvec.push_back(9);
133 cout << "size=" << mvec.size() << endl;
134 cout << "capacity=" << mvec.capacity() << endl;
135 for(it = mvec.begin();it < mvec.end(); ++it)
136 {
137 cout << *it << " ";
138 }
139 cout << endl;
140 mvec.push_back(0);
141 cout << "size=" << mvec.size() << endl;
142 cout << "capacity=" << mvec.capacity() << endl;
143 for(it = mvec.begin();it < mvec.end(); ++it)
144 {
145 cout << *it << " ";
146 }
147 cout << endl;
148 return 0;
149 }
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！
时间： 2024-11-02 01:31:04