重载new[]和delete[]示例

其实，new和delete运算符是可以重载的。一个类允许它有自己的new和delete运算符。当一个类和内存打交道时，采用这种方法来处理其中的细节，可以获得较高的效益，避免了使用全局new和delete运算符带来的额外开销。因为全局堆操作是调用操作系统函数来分配和释放内存，这样的效率是很低的，特别是档程序要频繁地分配和释放大量的小内存块的时候。

#include <iostream>#include <cstring>#include <cstddef>#include <new>const int maxNames = 5;class Names{char name[25];static char Names::pool[];static short int Names::inUse[maxNames];public:Names(char* s = 0) {if (s) std::strncpy(name, s, sizeof(name));}void* operator new[](size_t size) throw(std::bad_alloc);void operator delete[](void*) throw();void display() const {std::cout << name << std::endl;}};char Names::pool[maxNames * sizeof(Names)];short int Names::inUse[maxNames];void* Names::operator new[](size_t size) throw(std::bad_alloc){int elements = size / sizeof(Names);for (int p = 0; p < maxNames; p++){if (!inUse[p]){int i;for (i = 0; i < elements && p+i < maxNames; i++)if (inUse[p+i])break;if (i == elements && p+i < maxNames){for (i = 0; i < elements; i++)inUse[p+i] = elements;return pool + (p * sizeof(Names));}}}throw std::bad_alloc();}void Names::operator delete[](void* b) throw(){if (b != 0){int p = ((char*)b - pool) / sizeof(Names);int elements = inUse[p];for (int i = 0; i < elements; i ++)inUse[p + i] = 0;}}int main(){Names* np = new Names[maxNames-1];int i;for (i = 0; i < maxNames; i++){std::cout << std::endl << "Enter name # " << i + 1 << ": ";char name[25];std::cin >> name;*(np + i) = name;}for (i = 0; i < maxNames; i++){(np + i)->display();}delete [] np;return 0;}