Re: [pdf-devel] FS module, file readable/writeable

[Aleksander Morgado]

>>    And BTW, we should probably have an additional function for multiple
>>    checks, like a wrapper for the access() function.
>>
>>    Then the pdf_fsys_item_p, pdf_fsys_item_is_readable_p and
>>    pdf_fsys_item_is_writable_p functions could even be macros calling
>>    pdf_fsys_item_access.
>>
>> That modification would involve to change the filesystem
>> implementation interface. Not all filesystems will have an access-like
>> functionality in a native way.
>>
>> As a matter of convenience we could provide a pdf_fsys_item_access
>> function
>> that would internally use the pdf_fsys_item_* functions.
>>
> We basically have this already with pdf_fsys_get_item_props. My
> intention is to just have pdf_fsys_item_{writable/readable}_p call that
> function in the disk implementation.

That's not the good way to do it.

Checking if the file is readable or writable does not mean it has the
read access bit or the write access bit. The filesystem could be mounted
read-only, so those bits are not useful.

The proper way would be to call access() function to check if the file
is readable or writable. That function takes into account both the
partition access permissions and the file access permissions.

> 
> For pdf_fsys_get_item_p I went the route of just trying to open the
> file. Though I could just make it call pdf_fsys_get_item_props as well.
> 

Again, you can't only try to read the file to know if the file exists.
What if you don't have read access but you have write access? You can
call again access() function with the F_OK flag for that.

-Aleksander