--On Thursday, January 15, 2009 02:00:09 PM -0500 Steven Jenkins
<[email protected]> wrote:
I would like to expose RPC code<->name mappings so that other programs
within OpenAFS can avoid hard-coding the mappings, as well as be able
to export them to the users (who might find them useful in debugging
network traces, for example, where their particular tool does not know
what a particular opcode corresponds to). From a user-level, it would
work as follows:
$ translate_rpc -name PR_INewEntry
500
It would accomplish this by extending rxgen to pul the procedure
identifier and opcode from the specification file: e.g., given the
following hunks of code:
"package" <Package_ident>
...
<Procedure description option>:
["proc"] [<Procedure_ident>] [<ServerStub_ident>]
<Argument list> ["split" | "multi"]
["=" <Opcode_ident>] ";"
would produce new tables which would automatically go into the .h file
for that specification file: e.g.,
<Package_ident>_name[<Opcode_ident>] = <Procedure_ident>
and
<Package_ident>_opcode[<Procedure_ident> = <Opcode_ident>
Sorry, this is about as clear as mud, perhaps because the above isn't valid
C and certainly isn't a declaration, and perhaps because all the extraneous
"_ident" is confusing me. You sound like you're proposing creating a pair
of arrays to be used as lookup tables, but this has a couple of problems:
1) Translation of opcodes to names could be done by an array lookup, but it
shouldn't be, because the required array will generally be quite large and
very sparse. Instead, you should emit a _function_ which uses the same
logic as the ExecuteRequest function already emitted by rxgen, and which
handles large gaps in the opcode space in a reasonably efficient way.
2) Translation of names to opcode cannot be done by an array lookup,
because this is C, not awk or python, and strings cannot be used as array
indices. Again, I recommend actually emitting a function which does the
required translation. This won't be like anything currently in OpenAFS,
but shouldn't be too hard to construct. I recommend looking at using gperf
to generate a perfect hash table for each set of procedures.
It should be possible to get rxgen to produce these functions for any
interface, and preferably in a separate file from any of its other outputs,
so that they may be collected together into a library that has no other
dependencies. I would also very much like to see a mode in which rxgen
emits a simple table of opcode numbers and procedure names, one per line.
This would be useful in constructing a standalone lookup tool that reads
one table per RPC interface (similar to something I've already done for
com_err tables), and may also be of use to the registrars in constructing
some of the procedure number tables we currently don't have.
-- Jeff
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