/*
 * Copyright (C) 2001-2019 Jacek Sieka, arnetheduck on gmail point com
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

#pragma once

#include "CriticalSection.h"
#include "debug.h"

namespace dcpp {

#ifndef _DEBUG
struct FastAllocBase {
    static FastCriticalSection cs;
};

/**
 * Fast new/delete replacements for constant sized objects, that also give nice
 * reference locality...
 */
template<class T>
struct FastAlloc : public FastAllocBase {
    // Custom new & delete that (hopefully) use the node allocator
    static void* operator new(size_t s) {
        if(s != sizeof(T))
            return ::operator new(s);
        return allocate();
    }

    // Avoid hiding placement new that's needed by the stl containers...
    static void* operator new(size_t, void* m) {
        return m;
    }
    // ...and the warning about missing placement delete...
    static void operator delete(void*, void*) {
        // ? We didn't allocate so...
    }

    static void operator delete(void* m, size_t s) {
        if (s != sizeof(T)) {
            ::operator delete(m);
        } else if(m != NULL) {
            deallocate((uint8_t*)m);
        }
    }
protected:
    ~FastAlloc() { }

private:

    static void* allocate() {
        FastLock l(cs);
        if(freeList == NULL) {
            grow();
        }
        void* tmp = freeList;
        freeList = *((void**)freeList);
        return tmp;
    }

    static void deallocate(void* p) {
        FastLock l(cs);
        *(void**)p = freeList;
        freeList = p;
    }

    static void* freeList;

    static void grow() {
        dcassert(sizeof(T) >= sizeof(void*));
        // We want to grow by approximately 128kb at a time...
        size_t items = ((128*1024 + sizeof(T) - 1)/sizeof(T));
        freeList = new uint8_t[sizeof(T)*items];
        uint8_t* tmp = (uint8_t*)freeList;
        for(size_t i = 0; i < items - 1; i++) {
            *(void**)tmp = tmp + sizeof(T);
            tmp += sizeof(T);
        }
        *(void**)tmp = NULL;
    }
};
template<class T> void* FastAlloc<T>::freeList = NULL;
#else
template<class T> struct FastAlloc { };
#endif

} // namespace dcpp
