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authorVito Caputo <vcaputo@pengaru.com>2020-02-03 00:29:09 -0800
committerVito Caputo <vcaputo@pengaru.com>2020-02-03 00:37:50 -0800
commitba74a824658f7f59add288d28006ff48bf46b963 (patch)
treede09e33f3487a20319863bdae964f4ad5c3b5666 /src/libs/sig
parentf07b311173e1231f6c0c85a47d6068de7aa00761 (diff)
libs/sig: introduce a signal generator abstraction
This adds a small framework of sorts for creating and composing signal generators. Two generators are implemented at this time; sig_ops_sin and sig_ops_mult sig_ops_sin accepts a hz variable and will produce a sine wave of that frequency. sig_ops_mult accepts two sig_t generators and multiplies their outputs Callers may construct their own sig_ops_t ops structs and supply them to sig_new(), but it's expected that libs/sig will grow a collection of commonly used generators which can then be used by simply passing their sig_ops_$foo to sig_new(). See the test code at the bottom of libs/sig/sig.c for some contrived sample usage. Note by composing multiple sig_ops_sin generators with a sig_ops_mult generator, one can already easily construct a synth-like LFO generator. Some obvious todos are to add triangle/sawtooth/square wave generators. More compositional generators may be interesting as well, like additive and subtractive for example. Those will need to implement clipping, as it's expected that the generators *always* stay within unity (0-1). No modules use this yet, but I expect to wire this up to rtv for driving knobs.
Diffstat (limited to 'src/libs/sig')
-rw-r--r--src/libs/sig/Makefile.am3
-rw-r--r--src/libs/sig/ops_mult.c58
-rw-r--r--src/libs/sig/ops_sin.c49
-rw-r--r--src/libs/sig/sig.c100
-rw-r--r--src/libs/sig/sig.h30
5 files changed, 240 insertions, 0 deletions
diff --git a/src/libs/sig/Makefile.am b/src/libs/sig/Makefile.am
new file mode 100644
index 0000000..4787b5a
--- /dev/null
+++ b/src/libs/sig/Makefile.am
@@ -0,0 +1,3 @@
+noinst_LIBRARIES = libsig.a
+libsig_a_SOURCES = ops_mult.c ops_sin.c sig.c sig.h
+libsig_a_CPPFLAGS = -I@top_srcdir@/src
diff --git a/src/libs/sig/ops_mult.c b/src/libs/sig/ops_mult.c
new file mode 100644
index 0000000..7133e25
--- /dev/null
+++ b/src/libs/sig/ops_mult.c
@@ -0,0 +1,58 @@
+#include <assert.h>
+
+#include "sig.h"
+
+
+typedef struct ops_mult_ctxt_t {
+ sig_t *a, *b;
+} ops_mult_ctxt_t;
+
+
+static size_t ops_mult_size(va_list ap)
+{
+ return sizeof(ops_mult_ctxt_t);
+}
+
+
+/* supply two sig_t's to be multiplied, this sig_t takes
+ * ownership of them so they'll be freed by the multiplier
+ * on destroy when that sig_t is freed.
+ */
+static void ops_mult_init(void *context, va_list ap)
+{
+ ops_mult_ctxt_t *ctxt = context;
+
+ assert(ctxt);
+
+ ctxt->a = va_arg(ap, sig_t *);
+ ctxt->b = va_arg(ap, sig_t *);
+}
+
+
+static float ops_mult_output(void *context, unsigned ticks_ms)
+{
+ ops_mult_ctxt_t *ctxt = context;
+
+ assert(ctxt);
+
+ return sig_output(ctxt->a, ticks_ms) * sig_output(ctxt->b, ticks_ms);
+}
+
+
+static void ops_mult_destroy(void *context)
+{
+ ops_mult_ctxt_t *ctxt = context;
+
+ assert(ctxt);
+
+ sig_free(ctxt->a);
+ sig_free(ctxt->b);
+}
+
+
+sig_ops_t sig_ops_mult = {
+ .size = ops_mult_size,
+ .init = ops_mult_init,
+ .destroy = ops_mult_destroy,
+ .output = ops_mult_output,
+};
diff --git a/src/libs/sig/ops_sin.c b/src/libs/sig/ops_sin.c
new file mode 100644
index 0000000..b228b49
--- /dev/null
+++ b/src/libs/sig/ops_sin.c
@@ -0,0 +1,49 @@
+#include <assert.h>
+#include <math.h>
+
+#include "sig.h"
+
+
+typedef struct ops_sin_ctxt_t {
+ float 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, double);
+ assert(ctxt->hz >= .0001f);
+}
+
+
+static float ops_sin_output(void *context, unsigned ticks_ms)
+{
+ ops_sin_ctxt_t *ctxt = context;
+ float rads_per_ms, rads;
+ unsigned ms_per_cycle;
+
+ assert(ctxt);
+
+ ms_per_cycle = ctxt->hz * 1000.f;
+ rads_per_ms = (M_PI * 2.f) * ctxt->hz * .001f;
+ rads = (float)(ticks_ms % ms_per_cycle) * rads_per_ms;
+
+ return sinf(rads);
+}
+
+
+sig_ops_t sig_ops_sin = {
+ .size = ops_sin_size,
+ .init = ops_sin_init,
+ .output = ops_sin_output,
+};
diff --git a/src/libs/sig/sig.c b/src/libs/sig/sig.c
new file mode 100644
index 0000000..e3d5a7c
--- /dev/null
+++ b/src/libs/sig/sig.c
@@ -0,0 +1,100 @@
+#include <assert.h>
+#include <stdarg.h>
+#include <stdlib.h>
+
+#include "sig.h"
+
+
+typedef struct sig_t {
+ const sig_ops_t *ops;
+ void *ctxt[];
+} sig_t;
+
+
+/* return a new signal generator of ops type, configured according to va_list */
+sig_t * sig_new(const sig_ops_t *ops, ...)
+{
+ static const sig_ops_t null_ops;
+ size_t ctxt_size = 0;
+ sig_t *sig;
+ va_list ap;
+
+ if (!ops)
+ ops = &null_ops;
+
+ va_start(ap, ops);
+ if (ops->size)
+ ctxt_size = ops->size(ap);
+ va_end(ap);
+
+ sig = calloc(1, sizeof(sig_t) + ctxt_size);
+ if (!sig)
+ return NULL;
+
+ va_start(ap, ops);
+ if (ops->init)
+ ops->init(&sig->ctxt, ap);
+ va_end(ap);
+
+ sig->ops = ops;
+
+ return sig;
+}
+
+
+/* free a signal generator, always returns NULL */
+sig_t * sig_free(sig_t *sig)
+{
+ if (sig) {
+ if (sig->ops->destroy)
+ sig->ops->destroy(&sig->ctxt);
+
+ free(sig);
+ }
+
+ return NULL;
+}
+
+
+/* produce the value for time ticks_ms from the supplied signal generator,
+ * the returned value should always be kept in the range 0-1.
+ */
+float sig_output(sig_t *sig, unsigned ticks_ms)
+{
+ assert(sig);
+ assert(sig->ops);
+
+ if (sig->ops->output)
+ return sig->ops->output(sig->ctxt, ticks_ms);
+
+ return 0;
+}
+
+
+#ifdef TESTING
+
+#include <stdio.h>
+
+int main(int argc, char *argv[])
+{
+ sig_t *sig;
+
+ sig = sig_new(NULL);
+ printf("null output=%f\n", sig_output(sig, 0));
+ sig = sig_free(sig);
+
+ sig = sig_new(&sig_ops_sin, 2.f);
+ for (unsigned i = 0; i < 1000; i++)
+ printf("sin 2hz output %i=%f\n", i, sig_output(sig, i));
+ sig = sig_free(sig);
+
+ sig = sig_new(&sig_ops_mult,
+ sig_new(&sig_ops_sin, 1.f), /* LFO @ 1hz */
+ sig_new(&sig_ops_sin, 100.f) /* oscillator @ 100hz */
+ );
+ for (unsigned i = 0; i < 1000; i++)
+ printf("sin 100hz * 1hz output %i=%f\n", i, sig_output(sig, i));
+ sig = sig_free(sig);
+}
+
+#endif
diff --git a/src/libs/sig/sig.h b/src/libs/sig/sig.h
new file mode 100644
index 0000000..cd22d4d
--- /dev/null
+++ b/src/libs/sig/sig.h
@@ -0,0 +1,30 @@
+#ifndef _SIG_H
+#define _SIG_H
+
+#include <stdarg.h>
+#include <stddef.h>
+
+typedef struct sig_t sig_t;
+
+typedef struct sig_ops_t {
+ size_t (*size)(va_list ap); /* return size of space needed for context for given ap */
+ void (*init)(void *context, va_list ap); /* initialize context w/given ap */
+ void (*destroy)(void *context); /* destroy initialized context */
+ float (*output)(void *context, unsigned ticks_ms); /* output a value 0-1 from context appropriate @ time ticks_ms */
+} sig_ops_t;
+
+sig_t * sig_new(const sig_ops_t *ops, ...);
+sig_t * sig_free(sig_t *sig);
+float sig_output(sig_t *sig, unsigned ticks_ms);
+
+extern sig_ops_t sig_ops_sin;
+
+/* TODO:
+extern sig_ops_t sig_ops_tri;
+extern sig_ops_t sig_ops_saw;
+extern sig_ops_t sig_ops_sqr;
+*/
+
+extern sig_ops_t sig_ops_mult;
+
+#endif
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