More on Object Oriented PHP extensions
In the last post, I mentioned that the libixp sources may have to be modified to work around callbacks, but Kris quickly pointed out that there’s a special aux element meant specifically for developers to put whatever they like into. The aux element is automatically passed to every callback function via the Ixp9Req struct:
struct Ixp9Req {
Ixp9Conn *conn;
Fid *fid;
Fid *newfid;
Ixp9Req *oldreq;
Fcall ifcall;
Fcall ofcall;
void *aux;
};
The aux element is created during the call to ixp_listen:
IxpConn *ixp_listen(IxpServer *s, int fd, void *aux, void (*read)(IxpConn *c), void (*close)(IxpConn *c));
Now how do we wrap this functionality in PHP land? The aux functionality must be passed on the 9P developers using PHP, while still being able to extract the zval that we need to invoke the appropriate callback. Thanks to the marshaller method, we can mangle struct values as much as we like before passing the values into their PHP counterparts. We simply create a struct to wrap both our callback values and the aux element from the user:
typedef struct _IxpAux {
IxpCallback *cb;
zval *aux;
int type;
} IxpAux;
In the marshaller, we simply extract the aux value out from the structure, convert it to a regular PHP-type and pass it along to the PHP-level function using Zend’s call_user_function_ex() method. That problem solved, onto the next! Creating objects of a class in a method of another class - the IxpCFid class has no constructor, but an object is returned by calls to an IxpClient object. More on that later!