STL源码剖析 [简单应用总结二]

容器：

//see <a target=_blank href="http://www.cplusplus.com/reference/stl/">http://www.cplusplus.com/reference/stl/</a>// 演示STL容器#include <assert.h>#include <vector>#include <iostream>#include <iterator>#include <list>#include <ext/slist>#include <deque>#include <set>#include <map>#include <ext/hash_set>#include <ext/hash_map>#include <stack>#include <queue>//用于排序的函数对象struct ltstr{bool operator()(const char* s1, const char* s2) const{return strcmp(s1, s2) < 0;}};//用于哈希查找的函数对象struct eqstr{bool operator()(const char* s1, const char* s2) const{return strcmp(s1, s2) == 0;}};//哈希查找void lookup(const __gnu_cxx::hash_set<const char*, __gnu_cxx::hash<const char*>, eqstr>& Set,    const char* word){__gnu_cxx::hash_set<const char*, __gnu_cxx::hash<const char*>, eqstr>::const_iterator it= Set.find(word);std::cout << word << ": "<< (it != Set.end() ? "present" : "not present")<< std::endl;}//哈希查找void lookup(const __gnu_cxx::hash_multiset<const char*, __gnu_cxx::hash<const char*>, eqstr>& Set,    const char* word){int n_found = Set.count(word);std::cout << word << ": "<< n_found << " "<< (n_found == 1 ? "instance" : "instances")<< std::endl;}// 使用typedef简化容器的类型名typedef __gnu_cxx::hash_multimap<const char*, int, __gnu_cxx::hash<const char*>, eqstr> map_type;//哈希查找void lookup(const map_type& Map, const char* str){std::cout << str << ": ";std::pair<map_type::const_iterator, map_type::const_iterator> p =Map.equal_range(str);for (map_type::const_iterator i = p.first; i != p.second; ++i)std::cout << (*i).second << " ";std::cout << std::endl;}int main(int argc, const char *argv[]){{//vector<T, Alloc>//支持随机元素访问的动态数组（序列）std::vector<int> V;V.insert(V.begin(), 3);assert(V.size() == 1 && V.capacity() >= 1 && V[0] == 3);//扩大vector的容量到指定值，除非已经超过指定值std::cout << "size:" << V.size() << ",capacity:" << V.capacity() << std::endl;V.reserve(3);std::cout << "size:" << V.size() << ",capacity:" << V.capacity() << std::endl;//用构造函数复制vector，容量会自动压缩 std::vector<int> temp(V.begin(), V.end());std::cout << "Use vector's ctor copy:" << std::endl;std::cout << "size:" << temp.size() << ",capacity:" << temp.capacity() << std::endl;//用swap把序列转移到新的vector，容量不会改变，//而且原来的vector会被修改（交换了内容）std::vector<int> temp_swap;temp_swap.swap(V);std::cout << "Use vector's swap:" << std::endl;std::cout << "temp_swap's size:" << temp_swap.size() << ",capacity:" << temp_swap.capacity() << std::endl;std::cout << "V's size:" << V.size() << ",capacity:" << V.capacity() << std::endl;//把序列复制到vector，通常用于输入流//用法类似std::copystd::cout << "Please input double array (NaN is EOF):" << std::endl;std::istream_iterator<double> first(std::cin);std::istream_iterator<double> eof;std::vector<double> buf(first, eof);std::cout << "input double numbers are:" << std::endl;std::copy(buf.begin(), buf.end(), std::ostream_iterator<double>(std::cout, "\n"));std::cout << std::flush;}{//list<T, Alloc>//双向链表std::list<int> L;L.push_back(0);L.push_front(1);L.insert(++L.begin(), 2);std::cout << "list:" << std::endl;std::copy(L.begin(), L.end(), std::ostream_iterator<int>(std::cout, " "));std::cout << std::endl;//排序L.sort();std::cout << "sorted list:" << std::endl;std::copy(L.begin(), L.end(), std::ostream_iterator<int>(std::cout, " "));std::cout << std::endl;//合并std::list<int> L2;L2.push_back(3);L2.push_back(2);L2.push_back(1);L.merge(L2);std::cout << "merged list:" << std::endl;std::copy(L.begin(), L.end(), std::ostream_iterator<int>(std::cout, " "));std::cout << std::endl;//颠倒次序L.reverse();std::cout << "reversed list:" << std::endl;std::copy(L.begin(), L.end(), std::ostream_iterator<int>(std::cout, " "));std::cout << std::endl;}{//slist<T, Alloc>//单向链表//从begin()插入__gnu_cxx::slist<int> L;L.push_front(0);L.push_front(1);L.insert_after(L.begin(), 2);std::cout << "slist, insert to begin:" << std::endl;std::copy(L.begin(), L.end(),   std::ostream_iterator<int>(std::cout, " "));std::cout << std::endl;//从end()插入__gnu_cxx::slist<int>::iterator back = L.previous(L.end());back = L.insert_after(back, 3); back = L.insert_after(back, 4);back = L.insert_after(back, 5);std::cout << "slist, insert to end:" << std::endl;std::copy(L.begin(), L.end(),   std::ostream_iterator<int>(std::cout, " "));std::cout << std::endl;}{//deque<T, Alloc>//双端队列，类似vector，//支持随机访问和双端插入，//但不支持capacity()和reserve()std::deque<int> Q;Q.push_back(3);Q.push_front(1);Q.insert(Q.begin() + 1, 2);Q[2] = 0;std::cout << "deque:" << std::endl;std::copy(Q.begin(), Q.end(), std::ostream_iterator<int>(std::cout, " "));std::cout << std::endl;}{//set<Key, Compare, Alloc>//集合，不重复的序列，可执行交、并、差集const int N = 6;const char* a[N] = {"isomer", "ephemeral", "prosaic",   "nugatory", "artichoke", "serif"};const char* b[N] = {"flat", "this", "artichoke",  "frigate", "prosaic", "isomer"};std::set<const char*, ltstr> A(a, a + N);std::set<const char*, ltstr> B(b, b + N);std::set<const char*, ltstr> C;std::cout << "Set A: ";std::copy(A.begin(), A.end(), std::ostream_iterator<const char*>(std::cout, " "));std::cout << std::endl;std::cout << "Set B: ";std::copy(B.begin(), B.end(), std::ostream_iterator<const char*>(std::cout, " "));   std::cout << std::endl;std::cout << "Union: ";std::set_union(A.begin(), A.end(), B.begin(), B.end(),std::ostream_iterator<const char*>(std::cout, " "),ltstr());   std::cout << std::endl;std::cout << "Intersection: ";std::set_intersection(A.begin(), A.end(), B.begin(), B.end(),std::ostream_iterator<const char*>(std::cout, " "),ltstr());    std::cout << std::endl;std::set_difference(A.begin(), A.end(), B.begin(), B.end(),std::inserter(C, C.begin()),ltstr());std::cout << "Set C (difference of A and B): ";std::copy(C.begin(), C.end(), std::ostream_iterator<const char*>(std::cout, " "));std::cout << std::endl;}{//map<Key, Data, Compare, Alloc>//关联数组，映射表，键不可重复std::map<const char*, int, ltstr> months;months["january"] = 31;months["february"] = 28;months["march"] = 31;months["april"] = 30;months["may"] = 31;months["june"] = 30;months["july"] = 31;months["august"] = 31;months["september"] = 30;months["october"] = 31;months["november"] = 30;months["december"] = 31;std::cout << "june -> " << months["june"] << std::endl;std::map<const char*, int, ltstr>::iterator cur  = months.find("june");std::map<const char*, int, ltstr>::iterator prev = cur;std::map<const char*, int, ltstr>::iterator next = cur;    ++next;--prev;std::cout << "Previous (in alphabetical order) is " << (*prev).first << std::endl;std::cout << "Next (in alphabetical order) is " << (*next).first << std::endl;//另一种插入键值对的方法（可以判断是否插入成功）std::map<const char*, int, ltstr> M;std::pair<std::map<const char*, int>::iterator, bool> p = M.insert(std::make_pair("A", 17));//第二返回值表示插入是否成功if(p.second)std::cout << "insert pair is " << p.first->first << ", " << p.first->second << std::endl;//<< "pair:" << "," << p.second }{//multiset<Key, Compare, Alloc>//允许元素重复的集合const int N = 10;int a[N] = {4, 1, 1, 1, 1, 1, 0, 5, 1, 0};int b[N] = {4, 4, 2, 4, 2, 4, 0, 1, 5, 5};std::multiset<int> A(a, a + N);std::multiset<int> B(b, b + N);std::multiset<int> C;std::cout << "Set A: ";std::copy(A.begin(), A.end(), std::ostream_iterator<int>(std::cout, " "));std::cout << std::endl;std::cout << "Set B: ";std::copy(B.begin(), B.end(), std::ostream_iterator<int>(std::cout, " "));   std::cout << std::endl;std::cout << "Union: ";std::set_union(A.begin(), A.end(), B.begin(), B.end(),std::ostream_iterator<int>(std::cout, " "));std::cout << std::endl;std::cout << "Intersection: ";std::set_intersection(A.begin(), A.end(), B.begin(), B.end(),std::ostream_iterator<int>(std::cout, " "));std::cout << std::endl;  std::set_difference(A.begin(), A.end(), B.begin(), B.end(),std::inserter(C, C.begin()));std::cout << "Set C (difference of A and B): ";std::copy(C.begin(), C.end(), std::ostream_iterator<int>(std::cout, " "));std::cout << std::endl;}{//multimap<Key, Data, Compare, Alloc>//键允许重复的关联数组std::multimap<const char*, int, ltstr> m;m.insert(std::pair<const char* const, int>("a", 1));m.insert(std::pair<const char* const, int>("c", 2));m.insert(std::pair<const char* const, int>("b", 3));m.insert(std::pair<const char* const, int>("b", 4));m.insert(std::pair<const char* const, int>("a", 5));m.insert(std::pair<const char* const, int>("b", 6));std::cout << "Number of elements with key a: " << m.count("a") << std::endl;std::cout << "Number of elements with key b: " << m.count("b") << std::endl;std::cout << "Number of elements with key c: " << m.count("c") << std::endl;std::cout << "Elements in m: " << std::endl;for (std::multimap<const char*, int, ltstr>::iterator it = m.begin(); it != m.end(); ++it)std::cout << "  [" << (*it).first << ", " << (*it).second << "]" << std::endl;}{//hash_set<Key, HashFcn, EqualKey, Alloc>//支持哈希查找的集合，不允许元素重复__gnu_cxx::hash_set<const char*, __gnu_cxx::hash<const char*>, eqstr> Set;Set.insert("kiwi");Set.insert("plum");Set.insert("apple");Set.insert("mango");Set.insert("apricot");Set.insert("banana");lookup(Set, "mango");lookup(Set, "apple");lookup(Set, "durian");}{//hash_map<Key, Data, HashFcn, EqualKey, Alloc>//支持哈希查找的关联数组，不允许键重复__gnu_cxx::hash_map<const char*, int, __gnu_cxx::hash<const char*>, eqstr> months;months["january"] = 31;months["february"] = 28;months["march"] = 31;months["april"] = 30;months["may"] = 31;months["june"] = 30;months["july"] = 31;months["august"] = 31;months["september"] = 30;months["october"] = 31;months["november"] = 30;months["december"] = 31;std::cout << "september -> " << months["september"] << std::endl;std::cout << "april     -> " << months["april"] << std::endl;std::cout << "june      -> " << months["june"] << std::endl;std::cout << "november  -> " << months["november"] << std::endl;}{//hash_multiset<Key, HashFcn, EqualKey, Alloc>//支持哈希查找的集合，允许元素重复__gnu_cxx::hash_multiset<const char*, __gnu_cxx::hash<const char*>, eqstr> Set;Set.insert("mango");Set.insert("kiwi");Set.insert("apple");Set.insert("kiwi");Set.insert("mango");Set.insert("mango");Set.insert("apricot");Set.insert("banana");Set.insert("mango");lookup(Set, "mango");lookup(Set, "apple");lookup(Set, "durian");}{//hash_multimap<Key, Data, HashFcn, EqualKey, Alloc>//支持哈希查找的集合，允许键重复map_type M;M.insert(map_type::value_type("H", 1));M.insert(map_type::value_type("H", 2));M.insert(map_type::value_type("C", 12));M.insert(map_type::value_type("C", 13));M.insert(map_type::value_type("O", 16));M.insert(map_type::value_type("O", 17));M.insert(map_type::value_type("O", 18));M.insert(map_type::value_type("I", 127));lookup(M, "I");lookup(M, "O");lookup(M, "Rn");}{//stack<T, Sequence>//堆栈，后进先出std::stack<int> S;S.push(8);S.push(7);S.push(4);assert(S.size() == 3);assert(S.top() == 4);S.pop();assert(S.top() == 7);S.pop();assert(S.top() == 8);S.pop();assert(S.empty());}{//queue<T, Sequence>//队列，先进先出std::queue<int> Q;Q.push(8);Q.push(7);Q.push(6);Q.push(2);assert(Q.size() == 4);assert(Q.back() == 2);assert(Q.front() == 8);Q.pop();assert(Q.front() == 7);Q.pop();assert(Q.front() == 6);Q.pop();assert(Q.front() == 2);Q.pop();assert(Q.empty());}{//priority_queue<T, Sequence, Compare>//优先队列，最先弹出的是队列中的最大值std::priority_queue<int> Q;Q.push(1);Q.push(4);Q.push(2);Q.push(8);Q.push(5);Q.push(7);assert(Q.size() == 6);assert(Q.top() == 8);Q.pop();assert(Q.top() == 7);Q.pop();assert(Q.top() == 5);Q.pop();assert(Q.top() == 4);Q.pop();assert(Q.top() == 2);Q.pop();assert(Q.top() == 1);Q.pop();assert(Q.empty());//让队列中最小元素的先出列//其中，模板的第二参数表示它的底层实现是std::vector<int>std::priority_queue< int, std::vector<int>, std::greater<int> > Q2;Q2.push(4);Q2.push(2);assert(Q2.top() == 2);Q2.pop();assert(Q2.top() == 4);}//标准C++允许main不返回，但标准C要求必须返回return 0;}

自定义分配器：

// 19.4.2 一个用户定义分配器//演示标准库分配器allocator接口的简单实现#include <cstddef>#include <vector>#include <iostream>#include <iterator>//class Pool定义一个简单接口的小内存块内存池//这个内存池一次只能分配恒定大小的小内存块（由构造函数参数指定）class Pool {private://用于分配和释放内存的链表//比Chunk的粒度小，多个Link分割一个Chunk//分配前Link的next域用于计算下一个分配位置//分配后Link只是void*内存块的头部struct Link{Link *next;};// 底层内存分配区的分区块// 一个Pool内有多个依次链接的Chunk//每个Chunk被多个Link分割成更小的内存块//（但所有Link的排列次序不一定依照其所在Chunk块的排列次序），//但因为内存是连续的，所以在增量分配和全体释放时速度会较快struct Chunk{//让一个Chunk不超过8K且略小于8Kenum { SIZE = 8 * 1024 - 16 }; unsigned char mem[SIZE];Chunk *next; //next应该不会超过16个字节};//多个Chunk前后组成一个链表（好像一个栈）Chunk *chunks; //每次alloc()返回的内存块最大大小，//但不能比sizeof(Link)小，也不能比Chunk::SIZE大const unsigned int esize;//当前空闲Chunk块内的空闲Link头部Link *head; //禁用默认的复制构造函数和复制赋值，//所以这里不需要定义方法体private:Pool(Pool& sz);void operator=(Pool&);private:void grow();public:Pool(unsigned int n);//指定每次alloc()返回的内存块大小~Pool();void* alloc(); //不需要指定内存块大小（在构造函数中指定）void free(void* b);};//从head链表的头部取出一个Link//如果空闲Chunk块用完，需要分配新的Chunk块，//然后用Link链表分割这个新的空闲Chunk块。inline void* Pool::alloc(){if (head == 0){grow();}Link *p = head;head = p->next;std::cout << "Pool::alloc():  p == " << p << ", head == " << head << std::endl;return p;}//把要释放的b放回head链表的头部inline void Pool::free(void* b){Link* p = static_cast<Link*>(b);p->next = head;std::cout << "Pool::free(): p == " << p << ", head == " << head << std::endl;head = p;}Pool::Pool(unsigned int sz): esize(sz < sizeof(Link) ? sizeof(Link) : sz){head = 0;chunks = 0;}Pool::~Pool(){Chunk *n = chunks;while (n){Chunk *p = n;n = n->next;delete p;}}//增量分配内存//虽然Link*所在的小内存块是连续的，//但alloc的分配次序不一定是连续的//（因为free()可能放回旧的内存块）void Pool::grow(){Chunk *n = new Chunk();n->next = chunks;chunks = n;std::cout << "Pool::grow(): esize == " << esize << std::endl;const int nelem = Chunk::SIZE / esize;unsigned char *start = n->mem;unsigned char *last = &start[(nelem - 1) * esize];for (unsigned char *p = start; p < last; p += esize){reinterpret_cast<Link*>(p)->next = reinterpret_cast<Link*>(p + esize);}reinterpret_cast<Link*>(last)->next = 0; //见alloc()的if (head == 0)head = reinterpret_cast<Link*>(start);}//template Pool_alloc把class Pool适配到C++标准库的分配器接口//不完整，因为有些接口没有实现，而有些接口只实现部分功能template<class T>class Pool_alloc{private:static Pool mem; //全局，以提高效率public:typedef T value_type;typedef size_t size_type;typedef ptrdiff_t difference_type;typedef T *pointer;typedef const T *const_pointer;typedef T &reference;typedef const T&const_reference;Pool_alloc();T* allocate(size_type n, void*);void deallocate(pointer p, size_type n);};//构造静态的mem域//因为Pool只能分配固定大小的小内存块，//而且Pool_alloc没有实现rebind方法//所以这里指定每次分配的连续内存区都必须是sizeof(T) * 128，//虽然造成浪费，但确保分配的内存是连续的。//没有超过Chunk块的8K上限，所以是安全的。template <class T> Pool Pool_alloc<T>::mem(sizeof(T) * 128);template <class T> Pool_alloc<T>::Pool_alloc(){}template<class T>T* Pool_alloc<T>::allocate(size_type n, void* = 0){if (n <= 128){void *p = mem.alloc();std::cout << "allocate : " << n << ", " << p << std::endl;return static_cast<T*>(p);} else {//TODO:std::cout << "allocate : " << n << std::endl;throw "allocate error"; //出错}}template<class T>void Pool_alloc<T>::deallocate(pointer p, size_type n){if (n <= 128){std::cout << "deallocate : " << n << ", " << p << std::endl;mem.free(p);return;} else {//TODO:std::cout << "deallocate : " << n << std::endl;throw "deallocate error"; //出错}}int main(int argc, const char *argv[]){{std::vector<int> V1;V1.push_back(1);V1.push_back(2);V1.push_back(3);V1.push_back(4);std::cout << "V1:"<< std::endl;std::copy(V1.begin(), V1.end(),std::ostream_iterator<int>(std::cout, " "));std::cout << std::endl;}{std::cout << "==================="<< std::endl;try{std::vector< int, Pool_alloc<int> > V2;std::cout << "V2.push_back(1);" << std::endl;V2.push_back(1);std::cout << "V2.push_back(2);" << std::endl;V2.push_back(2);std::cout << "V2.push_back(3);" << std::endl;V2.push_back(3);V2.push_back(4);std::cout << "V2:"<< std::endl;std::copy(V2.begin(), V2.end(),std::ostream_iterator<int>(std::cout, " "));std::cout << std::endl;}catch (const char *&str){std::cout << str << std::endl;}}return 0;}/**运行结果：V1:1 2 3 4===================V2.push_back(1);Pool::grow(): esize == 512Pool::alloc():  p == 0x3e4d68, head == 0x3e4f68allocate : 1, 0x3e4d68V2.push_back(2);Pool::alloc():  p == 0x3e4f68, head == 0x3e5168allocate : 2, 0x3e4f68deallocate : 1, 0x3e4d68Pool::free(): p == 0x3e4d68, head == 0x3e5168V2.push_back(3);Pool::alloc():  p == 0x3e4d68, head == 0x3e5168allocate : 4, 0x3e4d68deallocate : 2, 0x3e4f68Pool::free(): p == 0x3e4f68, head == 0x3e5168V2:1 2 3 4deallocate : 4, 0x3e4d68Pool::free(): p == 0x3e4d68, head == 0x3e4f68*/