Hi Thomas,
You are right. I also think a redesign of the cpp-wrapper would be the way to
go.
I was curiouse about the get_string() function and their behaviour of closing
the device after
retreiving the device-strings. So far I guess your points are a good way.
I'll take a look at some points but I suspect I won't be able to implement any
big stuff in the next
2 month (have a little crunch time at work). But I'll stay tuned on this.
Greets
pit
----- Original Nachricht ----
Von: Thomas Jarosch <thomas.jarosch@xxxxxxxxxxxxx>
An: libftdi@xxxxxxxxxxxxxxxxxxxxxxx
Datum: 05.02.2011 18:34
Betreff: Re: Bug in libftdipp Context::open()
> Hello pit,
>
> On 01/20/2011 01:27 PM, pitpompej@xxxxxxxx wrote:
> > I found a bug in the cpp-wrapper for the ftdi-lib that concerns nearly all
> open() functions of the Context-Class. All open-functions except the one
> with the usb_device parameter return with -1 (and error string "all fine")
> even if opening the device should be posssible (the ftdi-c version can open
> the same device). The reason for that behavior is, that they all use for the
> first connect to the device the correct ftdi-c-function concerning to the
> given parameters (open(vendor,pid) uses ftdi_usb_open(ftdi, vendor,
> product), open(description) uses ftdi_usb_open_string(ftdi,
> description.c_str()) and so on) but after the first connect they all use the
> ftdi_usb_get_strings function that needs as one parameter the usb_device.
> this has not been set before when using these special open-functions so it
> returns with an error and the open-function failes.
> > I have already implemented a fix in my sources by adding to further
> functions in the ftdi-c-lib that returns by reference the usb_device ande
> changed the concerning calls in the cpp-wrapper. That all works fine for me
> now.
> > But is a problem in the ftdi-cpp-wrapper worth a change in the
> ftdi-c-lib?
> > I will try to commit it if possible today, otherwise next week.
>
> Thanks for the report and your patch!
>
> Looking at the C++ wrapper three years later,
> I don't like the fact that I keeps an own "libusb_device *dev"
> pointer -and- a pointer to the ftdi_context.
>
> I think it can be improved without bloating the open()
> function of the C API. Something like this:
>
> - Remove the libusb_device pointer in the C++ wrapper
>
> - Provide a function in the C API to get the strings without
> closing the device. Thinking about it some more, the C API
> could do this by default, "wasting" some bytes for an
> already open device is a non-issue.
>
> - Kill the get_strings_and_reopen() function
>
> - Implement is_open() in the C API and kill the
> "open" flag, too.
>
> What do you think?
>
> Cheers,
> Thomas
>
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