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|
(PWL-ALG
(NAME "pwl")
(ARGUMENTS ("time_type" "t0") ("rate_type" "sr") ("LVAL" "lis"))
(SUPPORT-FUNCTIONS "
/* IMPLEMENTATION NOTE:
* The lis argument is a list of alternating sample numbers and values
* which are taken in pairs, with an implicit (0, 0) starting point. The
* last point is a sample number only, the value being implicitly 0.
* The bpt_ptr points to the next sample number in the list.
* The incr is set to the increment per sample, and lvl is the next
* sample value.
*
* The list is assumed to be well-formed, so it should be checked by
* the caller (users should not call this directly).
*/
/* compute_lvl -- setup the susp with level, advance bpt_ptr */
/*
* returns true if it is time to terminate
*
* Note: compute_lvl gets called in the outer loop to skip over
* a breakpoint pair before starting the compute_incr loop, which
* searches for a breakpoint that is some number of samples in the
* future. This code is not embedded in compute_incr because it is
* NOT called from the initialization, where it would be wrong to
* skip over the first breakpoint.
*/
boolean compute_lvl(pwl_susp_type susp)
{
if (!cdr(susp->bpt_ptr)) return true;
susp->lvl = getflonum(car(cdr(susp->bpt_ptr)));
susp->bpt_ptr = cdr(cdr(susp->bpt_ptr));
return !susp->bpt_ptr;
}
/* compute_incr -- setup the susp with level and increment */
/*
* returns true if it is time to terminate
*/
boolean compute_incr(pwl_susp_type susp, long *n, long cur)
{
double target;
while (*n == 0) {
*n = getfixnum(car(susp->bpt_ptr)) - cur;
/* if there is a 2nd element of the pair, get the target */
if (cdr(susp->bpt_ptr))
target = getflonum(car(cdr(susp->bpt_ptr)));
else target = 0.0;
if (*n > 0) susp->incr = (target - susp->lvl) / *n;
else if (compute_lvl(susp)) return true;
}
return false;
}
")
(SAMPLE-RATE "sr")
(STATE
("LVAL" "bpt_ptr" "lis")
("double" "incr" "0.0")
("double" "lvl" "0.0;
{ long temp = 0; compute_incr(susp, &temp, 0); }"))
(OUTER-LOOP "
if (susp->bpt_ptr == NULL) {
out: togo = 0; /* indicate termination */
break; /* we're done */
}
{ long cur = susp->susp.current + cnt;
long nn = getfixnum(car(susp->bpt_ptr)) - cur;
if (nn == 0) {
if (compute_lvl(susp) || compute_incr(susp, &nn, cur)) goto out;
}
togo = MIN(nn, togo);
}
")
(INNER-LOOP "output = (sample_type) lvl; lvl += incr;")
(MAINTAIN ("lvl" "susp->lvl += susp->incr * togo"))
(CONSTANT "incr")
(TERMINATE COMPUTED)
)
|
