int stepsize( struct Block *b, int cpos) {
    /* 
     * In the block b, what is the next character to check after cpos?
     */
    
    struct Peer *peer;
    struct Request *req;
    int step, i;
    int minstep = b->end - cpos;

    for (i=0; i< p->npeers; i++) {
        peer = b->pset.peer[i];
        for (j=0; j< peer->nreqs; j++) {
	    req = peer->req[j];
	    if ( cpos >= req->starts && cpos < req->end) {
		step = req->end - cpos;
		if (step < minstep) minstep = step;
	    } else if (cpos < req->start) {
		step = req->start - cpos;
		if (step > 0 && step < minstep) minstep = step;
	    }
	}
    }
    return minstep;
}