Sorry for the formatting, I'm not sure why the newlines got removed since I
formatted this much more nicely, any reason why it happened? I could repost it
in a more readble format
> From: jb_j...@hotmail.com
> To: internals@lists.php.net
> Date: Thu, 16 Sep 2010 09:56:59 +0000
> Subject: [PHP-DEV] Understanding the benefits of handling Bucket data in
> PHP's HashTables
>
>
> Hey guys (and girls),
> I have been reading this list for sometimebut this is the first time I'm
> actually posting something.This might fit better in a C\C++ forum but I base
> my question on the notion that I confidence in my C skills and that there is
> an underlying cause for the choice of PHP developers to save Bucket data the
> way they do.If I am mistaken in posting this here please let me know.
> I came to ponder this when working with hash functions
> (zend_hash_find,zend_hash_add) and I saw that zend_hash_add (macro for
> _zend_hash_add_or_update) accepts pData as void * but is usually passed an
> address of a pointer like in:
> zend_class_entry *ce;zend_hash_add(CG(class_table),
> "class_name",class_length+1, &ce);
> pData is in turn memcpy'd into a Bucket's pData element which is also void *,
> passing the &ce suggests that what will get memcpy'd will be the contents of
> &ce which is in turn the address pointed to by ce, the address of a
> zend_class_entry struct, this suggests that the Bucket's pData element though
> marked as void * actually servs as a void ** (since it points to an adress
> which should be dereferenced as a pointer).
> I validated this by looking at zend_hash_find which accepts pData as void **,
> this time pData is to hold the address for the data retrieved by
> zend_hash_find, this time I noticed the function call to be :
> zend_class_entry **ce;zend_hash_find(CG(class_table), "class_name",
> class_length+1, (void **) &ce);
> and the data assigned to pData is :*pData = Bucket->pData;
> By my logic by setting *pData I am setting the data held at the address in
> pData itself which is &ce, this sets ce to point to an address of
> Bucket->pData which as I established earlier is used as a void **.
> I may be missing some basic understanding in pointers but I am pretty
> confident that this is not the case and thus I am asking is there a specific
> reason to use this sort of 'trickery' instead of of explicitly using void *,
> I fail to see the harm in Bucket->pData being a pointer to the data itself
> and the needed casts to be done instead of the current situtaiton where it
> points to another address.
> Thank you for any light you can shed on this.
>
