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Date: Mon, 26 Feb 2007 11:26:54 +0100
Message-ID: <C2F85D46E420FD4DB2065FE6901C6D0B410F19@EXCHANGE04.info.ratp>
In-Reply-To: <20070224031755.GA29737@melo.nevali.net>
Thread-Topic: [PHP-DEV] Simulating require_once within an extension
Thread-Index: AcdXxlDe+TLzLRVgRlG7VtB+xT3OngBx0G6w
To: "Mo McRoberts" <mo@nevali.net>,
	<internals@lists.php.net>
Subject: RE : [PHP-DEV] Simulating require_once within an extension
From: francois.laupretre@ratp.fr (=?iso-8859-1?Q?LAUPRETRE_Fran=E7ois_=28P=29?=)
References: <20070224031755.GA29737@melo.nevali.net>

Sorry, I can't help with your C extension but I can give you a solution =
I implemented in PHP=20
for the same needs. I did using two mechanisms :

	- A stream wrapper to allow require_once to reference a virtual path. =
Not required if you=20
require 'real' files. In PHK, I need it because I implement a virtual =
file system.

	- A 'tunneling' function like yours, used through an eval(). I agree it =
is not very=20
elegant but, unfortunately, there is no 'uplevel' feature in PHP (could =
be an interesting=20
addition, along with a who_called_me()). This function generally returns =
a=20
'require_once <stream-wrapped path>' string,  but as we eval()uate the =
result, it can return=20
any code, even a 'throw Exception', to be thrown from the calling scope.

If you want to see more about this example, download the PHK_Creator =
building kit from=20
http://www.tekwire.net/joomla/download/phk, and search for the =
'web_tunnel' function in=20
file PHK.php.

Regards

Fran=E7ois

> -----Original Message-----
> From: Mo McRoberts [mailto:mo@nevali.net]=20
> Sent: Saturday, February 24, 2007 4:18 AM
> To: internals@lists.php.net
> Subject: [PHP-DEV] Simulating require_once within an extension
>=20
>=20
> Hi list,
>=20
> Apologies if I'm sending this to the wrong list; I couldn't=20
> see another which was more appropriate on the PHP Mailing Lists page.
>=20
> I'm developing a PHP extension for which part of the=20
> functionality can be described in a nutshell as:
>=20
> * at request start-up time, build a map of identifiers to=20
> path-names, read
>   from a configuration file;
>  =20
> * whilst a user script is being processed, a function provided by the
>   extension can be called to add, remove or modify items in=20
> the mapping;
>  =20
> * a user script can call a function, passing it an identifier=20
> in the map,
>   and the extension should simulate require_once being called with the
>   corresponding pathname (with some transformation applied).
>  =20
> For example, if the configuration file specified that 'foo'=20
> mapped to /www/common/foo, calling the above function with a=20
> parameter of 'foo' might simulate=20
> require_once('/www/common/foo/script.php') (where the=20
> transformation applied in this case is appending 'script.php'=20
> to the given pathname). A prototype implementation written in=20
> PHP itself works well enough, but obviously there are scoping=20
> issues with such an implementation (i.e., any scripts=20
> included are included within the scope of the function, not the
> caller) which I want to avoid through the use of an extension.
>=20
> Obviously, much of this is pretty trivial and=20
> straightforward. My problem is the actual simulation of=20
> require_once itself. As it's a language intrinsic, there's no=20
> simply-exposed API for performing the same action. Digging=20
> through the PHP sources, I've come across=20
> zend_execute_scripts(), which seems to fit the bill, although=20
> there's no documentation and very few examples of it being=20
> used outside of the PHP engine itself.
>=20
> From skimming as many bits of the PHP sources that actually use
> zend_execute_scripts() that I could find, the code I've come=20
> up with isn't hugely dissimilar to this:
>=20
> static int
> do_required(const char *filename TSRMLS_DC)
> {
> 	int r;
> 	zend_file_handle zh;
> =09
> 	if(SUCCESS !=3D (r =3D zend_stream_open(filename, &zh TSRMLS_CC)))
> 	{
> 		return r;
> 	}
> 	if(NULL =3D=3D zh.opened_path)
>    	{
> 		zh.opened_path =3D estrdup(filename);
> 	}
> 	if(zend_hash_add_empty_element(&EG(included_files),=20
> 		zh.opened_path, strlen(zh.opened_path) + 1) =3D=3D SUCCESS)
> 	{
> 		r =3D zend_execute_scripts(ZEND_REQUIRE_ONCE=20
> TSRMLS_CC, NULL, 1, &zh);
> 	}
> 	zend_stream_close(TSRMLS_CC);
> 	return r;
> }
>=20
> Simple enough, right? Wrong.
>=20
> I'm hoping at this point that somebody who knows the Zend=20
> internals pretty well will immediately spot which things I'm=20
> not initialising, saving/restoring, or happen to be=20
> double-freeing at this point, because I'm at a loss. My=20
> symptoms are this:
>=20
> * If calls to this function are nested, and an inner call results in
>   zend_stream_open() failing, I get faults in=20
> zend_get_executed_lineno(),
>   suggesting corruption somewhere.
>  =20
> * If I save, reset and restore return_value_ptr_ptr, active_op_array,=20
>   opline_ptr before doing anything, things seem better, but=20
> the Warning
>   message reported when the file can't be opened gives the=20
> error location
>   as [no active file] on line 0, which is less than ideal.
>=20
> * If I only save/reset/restore around the call to=20
> zend_get_executed_lineno()
>   itself, things seem to work until I get as far as=20
> installing the extension
>   for my Apache 2.2 module build of PHP: at which point, as=20
> soon as there's
>   some nesting things start to go bad (errors reported or=20
> not). Removing the
>   final zend_stream_close() call stops Apache from dying, but=20
> I strongly
>   suspect that I'm just masking the problem rather than fixing it.
>  =20
> So, my questions are: what am I doing wrong, and is there a=20
> better way to accomplish the same thing? I considered=20
> evaluating a script instead of trying to simulate=20
> require_once itself, but that seemed incredibly kludgy.
>=20
> Any help appreciated.
>=20
> Thanks,
>=20
> Mo.
>=20
> --=20
> PHP Internals - PHP Runtime Development Mailing List
> To unsubscribe, visit: http://www.php.net/unsub.php
>=20
>=20