Initializing a large data structure to be accessed strictly within a shared C library

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Dear R-devel members,

The question:  Is it possible to initialize and later free a large data
structure strictly within a shared C library, to be used by a function in
the C library that I'll call from R--without ever having to pass data to
and from R? This is analogous to C++ object initialization/use/destruction,
but if possible I'd like to stay in C.
Yes, if you use malloc or Calloc you'll get memory that you can manage 
yourself.  See Writing R Extensions, section 6.1.2.

Duncan Murdoch
The context: I'm implementing a particle swarm optimization of a
60-dimension nonlinear transform, where the transform is defined in a
half-gigabyte dataset. By carefully initializing a C struct I can trim a
large amount of work from the PSO iteration stage. This is, of course,
straight forward if I implement the whole thing in a self-contained C
program--however, I'd like R to handle the optimization routines, and my
shared library to implement the value function.

So: what do folks think?

Cheers,

James

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Thanks Duncan, you've unclogged my thinking. For anybody interested,
see below a sketch of the solution.

Cheers,

James

--START SKETCH OF SOLUTION--

#include <R.h>
#include <Rinternals.h>

static typedef struct {
    int nrow, ncol;
    double *data;
} _myparticle_data_struct;
static _myparticle_data_struct myparticle_data;

void myparticle_init() {
    // Before we begin, call this from .Call() to Ralloc() memory and load the
    // data into to myparticle_data.data
}

void myparticle_free() {
    // When we're done with the PSO, .Call() to Free() the data
}

void myparticle_eval(double *value, double *x) {
    // .Call() to evaluate the value *value given vector x[]
}

--END SKETCH OF SOLUTION--