自定义内存管理器 [英] Custom Memory Manager

问题描述

我想实现一个自定义内存管理器，我想知道是否有一个更好的方法来实现这个函数，当我被问到void指针算术，几个人认为，如果我在C ++中有一个void *一些是非常错误的。

I am trying to implement a custom memory manager and I am wondering if there is a better way to implement this function, as when I am asked about void pointer arithmetic, several people thought that if I had a void* in C++, something was very wrong.

// allocates a page of memory.
void ObjectAllocator::allocatePage()
{    
    //if(OAStats_.PagesInUse_ >= Config_.MaxPages_)
        //throw exception

    void* buffer = ::operator new(OAStats_.PageSize_); // allocate memory, no constructor call.

    // =============== Setup the PageList_ ===============
    GenericObject* pNewNode = ::new(buffer) GenericObject();    // Construct GenericObject for the pagelist.
    pNewNode->Next = PageList_->Next;                            // pNewNode points to wherever PageList_ pointed to.
    PageList_->Next = pNewNode;                                    // PageList_ points to pNewNode
    pNewNode = NULL;                                            // dont need this handle anymore
    buffer = static_cast<char*>(buffer) + sizeof(GenericObject);    // move pointer to point after the generic object.

    // =============== Setup the FreeList_ ===============
    for(int i=0;i<Config_.ObjectsPerPage_;++i)
    {
        static GenericObject* pPreviousNode = NULL;            // static variable to hold the previous node
        pNewNode = ::new(buffer) GenericObject();            // Construct GenericObject for the freelist.
        pNewNode->Next = pPreviousNode;
        pPreviousNode = pNewNode;
        buffer = static_cast<char*>(buffer) + OAStats_.ObjectSize_;    // move pointer by ObjectSize.
        ++OAStats_.FreeObjects_;
    }
    FreeList_->Next = pNewNode;

    ++OAStats_.PagesInUse_;
    ++OAStats_.Allocations_;
}

推荐答案

内存用于存储字符串（8位ANSI），所以将一个指向该缓冲区的指针声明为char并对其进行操作是有意义的。

If you need a block of memory for for storing a string (8-bit ANSI), it makes sense to declare a pointer to that buffer as char and operate on it.

需要一个blob的内存块，它没有固有的类型，所以你正确地选择void *来表示这个blob。

In your case, you need a block of memory that is a 'blob', it has no inherent type, so you correctly chose void* to represent that blob.

现在你需要增加指针由一些对象的大小。你不能对一个void指针执行算术的明显的原因，所以你做什么？投射它。没有什么可耻的。

Now you need to increment that pointer by the size of some object. You cannot perform arithmetic on a void pointer for obvious reasons, so what do you do? Cast it. There is no shame in that.

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