Per-class allocator 1

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#include <iostream>#include <cstddef>using namespace std;//ref. C++Primer 3/e.p.765//1.malloc效率//2.cookie管理//per-class allocatorclass Screen {public:Screen(int x): i(x) {}int get() {return i;}void* operator new(size_t);void operator delete(void*, size_t);private://这种设计会引发多好用一个next的疑虑Screen* next;static Screen* freeStore;static const int screenChunk;private:int i;};Screen* Screen::freeStore = 0;const int Screen::screenChunk = 24;void* Screen::operator new(size_t size) {Screen *p;if(!freeStore) {//linked list是空的，所以申请一大块size_t chunk = screenChunk * size;freeStore = p = reinterpret_cast<Screen*>(new char[chunk]);//将一大块，当做linked list串起来for(; p != &freeStore[screenChunk-1]; ++p) {p->next = p + 1;}p->next = 0;}p = freeStore;freeStore = freeStore->next;return p;}void Screen::operator delete(void* p, size_t size) {//将deleted object插回到 free list前端(static_cast<Screen*>(p))->next = freeStore;freeStore = static_cast<Screen*>(p);}int main() {cout << "sizeof(Screen)" << sizeof(Screen) << endl;size_t const N = 100;Screen* p[N];for(int i=0; i<N; ++i) {p[i] = new Screen(i);}for(int i=0; i<10; ++i) {cout << p[i] << endl;}for(int i=0; i<N; ++i) {delete p[i];p[i] = NULL;}return 0;}

使用member operator/delete的结果，不一定地址间隔差别8，但是结果差别8更好的显示没有cookie

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