how to make nasty code less nasty (obtaining sqlite db handle)

21 years ago by Derrell.Lipman@UnwiredUniverse.com — view source — reply

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I've written an extension which needs to accept a Resource which is an SQLite
database handle, and call a C function which will be using that db handle to
issue queries. What I've done works, but is kinda nasty because there doesn't
appear to be a clean way to obtain that database handle nor, from what I can
tell, determine the resource type to expect. Is there a nicer way of doing
this?

PHP_FUNCTION(my_PHP_function)
{
int id;
int dataLen;
int resourceType;
char * pData;
zval * zdb;
void * hDB;
void ** phDB;

/* Ensure we got the correct number of parameters */
if (ZEND_NUM_ARGS() != 2)
{
    WRONG_PARAM_COUNT;
}

/* Retrieve the parameters */
if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC,
                          "rs",
                          &zdb, &pData, &dataLen) == FAILURE)
{
    return;
}

/*
 * Voodoo to retrieve the sqlite database handle from the resource.
 * How do I validate that resourceType is reasonable?
 */
id = zdb->value.lval;
if ((phDB = zend_list_find(id, &resourceType)) == NULL)
{
    return;
}

/*
 * This is nasty too.  We "know" that the first field in the private
 * structure is the database handle.  Just extract it.
 */
hDB = *phDB;

RETURN_STRING(my_C_function(hDB, pData), TRUE);

}

Thanks,

Derrell

21 years ago by Wez Furlong — view source — reply

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There is no official way to do this kind of thing between arbitrary extensions.
When extensions that are written to share this information, they
typically export an XXX_API function that you can link against to
fetch the data.

What you've done works, so that's fine, although there is a risk of
crashing if someone passes the wrong type of resource in. If you're
thinking of distributing your extension, we could add a more official
API for you to use, although that doesn't exist in older versions of
the extension, etc. etc.

Some time back, I proposed a framework (and even a patch IIRC) that
allowed this kind of thing at run-time; despite "we the extension
developers" liking the idea, there was some negative feedback from
andi/zeev so it never went further. Search the php-dev archives for
my name and "interfaces" for more on that if you're interesting in
this seeing light in PHP 5.2.

--Wez.

On Thu, 03 Feb 2005 17:03:45 -0500, Derrell.Lipman@unwireduniverse.com
Derrell.Lipman@unwireduniverse.com wrote:

I've written an extension which needs to accept a Resource which is an SQLite
database handle, and call a C function which will be using that db handle to
issue queries. What I've done works, but is kinda nasty because there doesn't
appear to be a clean way to obtain that database handle nor, from what I can
tell, determine the resource type to expect. Is there a nicer way of doing
this?

PHP_FUNCTION(my_PHP_function)
{
int id;
int dataLen;
int resourceType;
char * pData;
zval * zdb;
void * hDB;
void ** phDB;
/* Ensure we got the correct number of parameters */
if (ZEND_NUM_ARGS() != 2)
{
    WRONG_PARAM_COUNT;
}

/* Retrieve the parameters */
if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC,
                          "rs",
                          &zdb, &pData, &dataLen) == FAILURE)
{
    return;
}

/*
 * Voodoo to retrieve the sqlite database handle from the resource.
 * How do I validate that resourceType is reasonable?
 */
id = zdb->value.lval;
if ((phDB = zend_list_find(id, &resourceType)) == NULL)
{
    return;
}

/*
 * This is nasty too.  We "know" that the first field in the private
 * structure is the database handle.  Just extract it.
 */
hDB = *phDB;

RETURN_STRING(my_C_function(hDB, pData), TRUE);
}

Thanks,

Derrell

21 years ago by Derrell.Lipman@UnwiredUniverse.com — view source — reply

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Wez Furlong kingwez@gmail.com writes:

There is no official way to do this kind of thing between arbitrary
extensions. When extensions that are written to share this information,
they typically export an XXX_API function that you can link against to fetch
the data.

What you've done works, so that's fine, although there is a risk of
crashing if someone passes the wrong type of resource in. If you're
thinking of distributing your extension, we could add a more official
API for you to use, although that doesn't exist in older versions of
the extension, etc. etc.

Thanks, Wez. My extension will likely never be used other than with
locally-written code. My biggest concern is making use of the incestual
knowledge of the private php_sqlite_db structure and that the database handle
is the first field in it. That structure may change in the future.

My use of this is as a function used in a query -- sqlite_create_function() is
used to allow a call to a php function which passes the database handle to the
extension function. Prior to today, my extension had its own private database
handle that it initialized on the MINIT function, but I was causing a deadlock
by calling this function from within a query in PHP which called the extension
which tried to issue additional queries using my private database handle in
the extension. Passing in the php-derived handle is the only way of
eliminating that deadlock.

I wonder whether I'm really alone in wanting access to a database handle for
extensions. It would seem appropriate to provide access to the C-level
database handle given a PHP resources. That would eliminate the need to base
an extenion on insestual knowledge of the database-specific extension.

Thanks again,

Derrell

21 years ago by Andrei Zmievski — view source — reply

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Some time back, I proposed a framework (and even a patch IIRC) that
allowed this kind of thing at run-time; despite "we the extension
developers" liking the idea, there was some negative feedback from
andi/zeev so it never went further. Search the php-dev archives for
my name and "interfaces" for more on that if you're interesting in
this seeing light in PHP 5.2.

I'd definitely be interested in seeing the extension dependency
framework in 5.2.

Andrei

21 years ago by Rasmus Lerdorf — view source — reply

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Andrei Zmievski wrote:

Some time back, I proposed a framework (and even a patch IIRC) that
allowed this kind of thing at run-time; despite "we the extension
developers" liking the idea, there was some negative feedback from
andi/zeev so it never went further. Search the php-dev archives for
my name and "interfaces" for more on that if you're interesting in
this seeing light in PHP 5.2.

I'd definitely be interested in seeing the extension dependency
framework in 5.2.

We need it for the ext/libxml mess, for example.

-Rasmus

21 years ago by Wez Furlong — view source — reply

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The extension deps framework (that orders the initialization done in
internal_functions.c) is already in HEAD; I was talking about the
extension "interfaces" idea I proposed a fairly long time ago now
(long enough that I can't remember how long ago). I remember you
showing interest in that at that time.

--Wez.

I'd definitely be interested in seeing the extension dependency
framework in 5.2.

Andrei

21 years ago by l0t3k — view source — reply

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i found this

http://www.zend.com/lists/php-dev/200204/msg01083.html

"Wez Furlong" kingwez@gmail.com wrote in message
news:4e89b42605020413515e6448e6@mail.gmail.com...

The extension deps framework (that orders the initialization done in
internal_functions.c) is already in HEAD; I was talking about the
extension "interfaces" idea I proposed a fairly long time ago now
(long enough that I can't remember how long ago). I remember you
showing interest in that at that time.

--Wez.

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