examples

commit f357d93a8859b6ff598392d2fe138550df92e5c6
parent 76401de43d3ec54c3a4f9635f1da340611496782
Author: Henry Wilson <henry@henryandlizzy.uk>
Date:   Fri, 10 Dec 2021 14:41:28 +0000

Add DSP processing kernel example

Diffstat:
A
src/dsp.c
 | 
133
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

1 file changed, 133 insertions(+), 0 deletions(-)
diff --git a/src/dsp.c b/src/dsp.c
@@ -0,0 +1,133 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+
+void die(char const* msg)
+{
+	if (errno)
+		perror(msg);
+	else
+		fprintf(stderr, "%s: Unknown failure\n", msg);
+	exit(EXIT_FAILURE);
+}
+
+void usage(int err)
+{
+	fputs("lol", err ? stderr : stdout);
+	exit(err);
+}
+
+static unsigned in_len, out_len;
+static float *in_kernel, *out_kernel;
+static float *in_history, *out_history;
+
+void do_history(unsigned len, float* history, float new)
+{
+	for (unsigned i = len - 1; i; --i)
+		history[i] = history[i-1];
+	history[0] = new;
+}
+
+float dsp(float in)
+{
+	float out = in;
+	if (in_len)
+	{
+		out *= in_kernel[0];
+		for (unsigned i = 1; i < in_len; ++i)
+			out += in_kernel[i] * in_history[i-1];
+
+		do_history(in_len, in_history, in);
+	}
+
+	if (out_len)
+	{
+		for (unsigned i = 0; i < out_len; ++i)
+			out += out_kernel[i] * out_history[i];
+
+		do_history(out_len, out_history, out);
+	}
+	return out;
+}
+
+float* fmalloc_or_die(unsigned n)
+{
+	if (!n)
+		return NULL;
+
+	float* p = malloc(n * sizeof(float));
+	if (!p)
+		die("malloc");
+
+	for (int i = 0; i < n; ++i)
+		p[i] = 0;
+	return p;
+}
+
+void graph(float signal, float out)
+{
+	unsigned unseen = 7;
+	for (int i = -20; unseen && i < 100; ++i)
+	{
+		unsigned seen = 0;
+		if (!i)
+			seen |= 1;
+		if (unseen & 4)
+			if (i >= signal)
+				seen |= 4;
+		if (unseen & 2)
+			if (i >= out)
+				seen |= 2;
+
+		switch(seen)
+		{
+		case 1:
+			putchar('|');
+			break;
+		case 2:
+			putchar('-');
+			break;
+		case 3:
+		case 6:
+		case 7:
+			putchar('+');
+			break;
+		case 4:
+		case 5:
+			putchar('.');
+			break;
+
+		default:
+			putchar(' ');
+		}
+
+		unseen &= ~seen;
+	}
+	putchar('\n');
+}
+
+int main(int argc, char const* argv[])
+{
+	in_len = 2;
+	out_len = 2;
+	in_history = fmalloc_or_die(in_len);
+	in_kernel = fmalloc_or_die(in_len);
+	out_history = fmalloc_or_die(out_len);
+	out_kernel = fmalloc_or_die(out_len);
+
+	in_kernel[0] = .4f;
+	in_kernel[1] = -.2f;
+	out_kernel[0] = 1.55f;
+	out_kernel[1] = -.75f;
+
+	float signal;
+	float out;
+	for (int i = 0; i < 50; ++i)
+	{
+		signal = i > 2 ? 50 : 0;
+
+		out = dsp(signal);
+		graph(signal, out);
+	}
+	printf("%.0f = %.0f\n", signal, out);
+}