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[PHP] Re: PHP extension writing

Hi Torsten!

On 24.09.2016 at 18:31, Torsten Rosenberger wrote:

> Am Samstag, den 24.09.2016, 17:46 +0200 schrieb Christoph M. Becker:
>> On 24.09.2016 at 16:29, Torsten Rosenberger wrote:
>>> PHP_FUNCTION(i2c_read_value)
>>> {
>>>     int arg_len;
>>>     unsigned char reg;
>>>     unsigned short res;
>>>     if(zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "s", &reg,
>>> &arg_len) == FAILURE){
>> That looks wrong.  `reg` should be declared as `char *`.
> i have seen “s”: string, expects char* and int.

Indeed[1].  But all output parameters of zend_parse_parameters() have to
passed as pointers (cf. `&arg_len`).
> but reg should be int it is a hex number for the i2c bus.

Then you should parse for "l", and handle out-of-range values by
throwing an error.  Otherwise the API is pretty fragile at best; for
instance, calling i2c_read_value('') might result in arbitrary behavior.

>> There might be a permission or working directory issue.
> you are right! apache2 was not able to access /dev/i2c-1 so I add the
> apache2 user to the i2c group but also had to change the acces mod to
> the file.
> now it works
> Thanks's a lot!

Fine.  You're welcome.

[1] <http://php.net/manual/en/internals2.funcs.php>

Christoph M. Becker

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