How to stack libtrivfs-based translators

Hello,

I have written a libtrivfs-based translator (the source code is
supplied in the attachment), however I have problems with stacking it
upon itself. I compile it using the following command:

gcc -Wall -g -ltrivfs -lfshelp mangle.c -o mangle -DDEBUG -DMANGLE

Then I stack it upon an untranslated node foo, which is a text file
containing the text: 'Hello'. I use the following command:

settrans -a foo mangle

If I now try to stack mangle upon foo again, using the command:

settrans -L foo mangle

I receive the following error message:

settrans: foo: not supported

I also tried settrans -aL foo mangle (not sure if this matters), but I
obtain the same result. When I try fsysopts on the translated node foo
in the following way:

fsysopts foo

I get a similar error:

fsysopts: foo: not supported

As you can see from mangle.c, I print a message in a log file
whenever any of libtrivfs callbacks is called. After the two
invocations of settrans, this file still contains the greeting message
only (i.e. "Log session started").

Could you please tell me what I am doing wrong?

scolobb

Hi,

Tue, Jul 15, 2008 at 06:10:02PM +0300, Sergiu Ivanov wrote:

I have written a libtrivfs-based translator (the source code is
supplied in the attachment), however I have problems with stacking it
upon itself.
[]
If I now try to stack mangle upon foo again, using the command:

settrans -L foo mangle

I receive the following error message:

settrans: foo: not supported

This requires certain RPCs in fs.defs (and probably fsys.defs) to be
implemented, most notably file_set_translator. A quick look at
file-set-translator.c from libtrivfs shows us that
trivfs_S_file_set_translator() is "implemented" as

{ return EPNTSUPP; }

i.e. it's not implemented at all.

In other words, libtrivfs doesn't seem to support setting further
translators on the translated node out of the box. (I think you could
implement it manually, though)

I must admit that this surprises me quite a bit. I wonder whether there
is any good reason for that

When I try fsysopts on the translated node foo in the following way:

fsysopts foo

I get a similar error:

fsysopts: foo: not supported

You need to implement the trivfs_append_args() callback -- see the hello
translator for a trivial example, or others like pfinet for more complex
ones.

-antrik-

Hi,

Wed, Jul 23, 2008 at 12:00:59PM +0300, Sergiu Ivanov wrote:

Could anybody suggest and idea how to implement this
trivfs_S_file_set_translator callback? I tried to find some clues in
trivfs.h and in hurd-cvs, but my attempts ended fruitless

Have you checked what libnetfs does? Probably you need to do more or
less the same

-antrik-