如何在C ++中合并内存分配器

Question

I am working on a lock free data structure, and I have been examining the code at libcds , but I can not seem to figure out how to incorporate there memory allocator into my class file.

template<class KEY, class VALUE>
class DataStruc{
public:

I have never used custom memory allocators before, and I am having trouble figuring out how to approach incorporating it.

Answer 1

You just need to implement operator new() for your class. Your implementation should get memory from an instance of the allocator.

In the header file for your class, you'll need to declare the allocation/deallocation operators:

public:
    void * operator new(size_t size);
    void * operator delete(void * obj, size_t size);
    void * operator new[](size_t size);
    void * operator delete[](void * obj, size_t size);

Then you need to implement them. Somewhere you need to instantiate an allocator; maybe just make it a static in the file where you implement these operators. Then, just looking at the API docs on that web site, you'd do something like the below. I put in the asserts because I can't see how to pass the object size to that allocator; that effectively means that YourClass better not serve as a parent to other classes.

static cds::details::Allocator<YourClass> allocator;

void * YourClass::operator new(size_t size) { 
    assert size == sizeof(YourClass);
    return allocator.New();
}

void * YourClass::operator new[](size_t size) { 
    return allocator.NewArray(size/sizeof(YourClass));
}

void YourClass::operator delete(void * object, size_t size) { 
    return allocator.Delete(object);
}

void YourClass::operator delete[](void * object, size_t size) { 
    return allocator.DeleteArray(object, size/sizeof(YourClass));
}

I'm not too happy with the asserts and divisions, but it's late and I'm tired. Maybe somebody else knows a more elegant way to make these APIs match up a bit better. But this'd work.

Answer 2

Read this post on some insight how to implement a custom memory allocation system: http://www.stevestreeting.com/2008/06/28/memory-man/

His post is in reference to the custom memory allocation system implemented in the open source Ogre3D graphics library. You can download its source code and see how it is done there at http://www.ogre3d.org/download/source