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#include <assert.h>
#include <math.h>
#include "sig.h"
typedef struct ops_sin_ctxt_t {
sig_t *hz;
} ops_sin_ctxt_t;
static size_t ops_sin_size(va_list ap)
{
return sizeof(ops_sin_ctxt_t);
}
static void ops_sin_init(void *context, va_list ap)
{
ops_sin_ctxt_t *ctxt = context;
assert(ctxt);
ctxt->hz = va_arg(ap, sig_t *);
}
static void ops_sin_destroy(void *context)
{
ops_sin_ctxt_t *ctxt = context;
assert(ctxt);
sig_free(ctxt->hz);
}
static float output_sin(float rads)
{
return sinf(rads) * .5f + .5f;
}
static float output_sqr(float rads)
{
if (sinf(rads) < 0.f)
return 0.f;
return 1.f;
}
static float output_tri(float rads)
{
/* This approximation comes from:
* https://calculushowto.com/triangle-wave-function/
*/
return M_2_PI * asinf(fabsf(sinf(M_PI * rads)));
}
static float output(void *context, unsigned ticks_ms, float (*output_fn)(float rads))
{
ops_sin_ctxt_t *ctxt = context;
float rads_per_ms, rads, hz;
assert(ctxt);
assert(ctxt->hz);
hz = sig_output(ctxt->hz, ticks_ms);
if (hz < .001f)
return 0.f;
/* TODO FIXME: wrap ticks_ms into the current cycle
* so rads can be as small as possible for precision reasons.
* I had some code here which attempted it but the results were
* clearly broken, so it's removed for now. As ticks_ms grows,
* the precision here will suffer.
*/
rads_per_ms = (M_PI * 2.f) * hz * .001f;
rads = (float)ticks_ms * rads_per_ms;
return output_fn(rads);
}
static float ops_sin_output(void *context, unsigned ticks_ms)
{
return output(context, ticks_ms, output_sin);
}
static float ops_sqr_output(void *context, unsigned ticks_ms)
{
return output(context, ticks_ms, output_sqr);
}
static float ops_tri_output(void *context, unsigned ticks_ms)
{
return output(context, ticks_ms, output_tri);
}
sig_ops_t sig_ops_sin = {
.size = ops_sin_size,
.init = ops_sin_init,
.destroy = ops_sin_destroy,
.output = ops_sin_output,
};
sig_ops_t sig_ops_sqr = {
.size = ops_sin_size,
.init = ops_sin_init,
.destroy = ops_sin_destroy,
.output = ops_sqr_output,
};
sig_ops_t sig_ops_tri = {
.size = ops_sin_size,
.init = ops_sin_init,
.destroy = ops_sin_destroy,
.output = ops_tri_output,
};
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