Re: [libcvd-members] libcvd cvd/Linux/dvbuffer3.h cvd_src/Linux/dvbu...

[Edward Rosten]

On Mon, 14 Jul 2008, Georg Klein wrote:

> The rationale behind this is that libDC1394v2 is a nice API. It's much more 
> sane to use that v1, and it also supports the new linux firewire stack 
> (juju); this combo ships out of the box with e.g. newish fedora 
> distributions. I'm also told that libdc1394v2 works in MacOS, and might work 
> in Win32 soon.

Sounds good.

> Since the old DVBuffer includes the v1 headers in it, it's not easy to 
> retrofit without code breakage, hence the new class. This one abstracts the 
> libdc1394 headers away.


> Unfortunately I still don't understand how autotools work, so none of this 
> gets built! Can anyone (Ed!) help out with this? If libdc1394 version 2 is

I don't have it installed, so  can't write the specific checks. I can give 
whatever help is needed.

> installed, it should build dvbuffer3_dc1394v2.cc; otherwise, if v1 is 
> installed and dvbuffer gets built, dvbuffer3_dv1394v1.cc should be compiled 
> (but not ever both.)

Sure:

You need a "check for library" command like this:

CHECK_FOR_LIBRARY(png, [
        AC_CHECK_HEADERS(png.h, [], [a=1])
        AC_CHECK_LIB(png, png_init_io, [], [a=1])
])


The last two arguments are "action if true" and "action if false". The 
action if false is to sert a to 1. If a=1 when CHECK_FOR_LIBRARY finishes, 
then it assumes that the test has failed. Basically, you need to choose a 
header to chech for, and a symbol in the .so to check for. In the latter 
case, you can choose "main", since this will simply check if you *can* 
link against the .so/


In this case there will be two checks, checking for v2, and for v1: 
Something like:

CHECK_FOR_LIBRARY(libdc1394v2, ... )
CHECK_FOR_LIBRARY(libdc1394v1, ... )


Then, you need to dig in to the dependency resolution list, which will 
determine what gets built, starting on line 841.

On the line 875:

#General OS specific bits
cvd_src/Linux/dvbuffer                                                  
dvbuffer END


This has the object file (minus the .o), along with the dependencies. The 
new one would look something like this:

cvd_src/Linux/dvbuffer3_dc1394v2     libdc1394v2
cvd_src/Linux/dvbuffer3_dc1394v1     libdc1394v1 END

The uppermost option satisfying the dependencies will be compiled. So this 
would use v2 if available, and v1 otherwise.

-Ed