Re: [PATCH v8 0/8] MR1628: ntdll: Implement Low Fragmentation Heap.

[Jinoh Kang (＠iamahuman)]

Jinoh Kang (@iamahuman) commented about dlls/ntdll/heap.c:
> +struct bin
> +{
> - /* counters for LFH activation */
> - LONG count_alloc;
> - LONG count_freed;
> - LONG enabled;
> -
> - /* list of groups with free blocks */
> - SLIST_HEADER groups;
> -
> - /* array of affinity reserved groups, interleaved with other bins to keep
> -
> * all pointers of the same affinity and different bin grouped together,
> -
> * and pointers of the same bin and different affinity away from each other,
> -
> * hopefully in separate cache lines.
> -
> */
> - struct group *(*affinity_group)[BLOCK_SIZE_BIN_COUNT];

I think relying on pointer arithmetic for the stride is quite tricky to understand. Also, I couldn't find any precedent in the Wine code base.

How about using the following helper function instead?

```c
static inline struct affinity_group **affinity_group_slot( struct bin *bin, ULONG affinity )
{
    /* see the struct field comment for details. */
    return bin->affinity_groups_base + affinity * BLOCK_SIZE_BIN_COUNT;
}
```

Example usage:

```c
    InterlockedExchangePointer( (void *)affinity_group_slot( bin, affinity ), NULL )
```

Feel free to choose another name or return type you like.