examples

Toy examples in single C files.
git clone git://henryandlizzy.uk/examples
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dsp.c (2066B)

      1 #include <stdio.h>
      2 #include <stdlib.h>
      3 #include <errno.h>
      4 
      5 void die(char const* msg)
      6 {
      7 	if (errno)
      8 		perror(msg);
      9 	else
     10 		fprintf(stderr, "%s: Unknown failure\n", msg);
     11 	exit(EXIT_FAILURE);
     12 }
     13 
     14 void usage(int err)
     15 {
     16 	fputs("lol", err ? stderr : stdout);
     17 	exit(err);
     18 }
     19 
     20 static unsigned in_len, out_len;
     21 static float *in_kernel, *out_kernel;
     22 static float *in_history, *out_history;
     23 
     24 void do_history(unsigned len, float* history, float new)
     25 {
     26 	for (unsigned i = len - 1; i; --i)
     27 		history[i] = history[i-1];
     28 	history[0] = new;
     29 }
     30 
     31 float dsp(float in)
     32 {
     33 	float out = in;
     34 	if (in_len)
     35 	{
     36 		out *= in_kernel[0];
     37 		for (unsigned i = 1; i < in_len; ++i)
     38 			out += in_kernel[i] * in_history[i-1];
     39 
     40 		do_history(in_len, in_history, in);
     41 	}
     42 
     43 	if (out_len)
     44 	{
     45 		for (unsigned i = 0; i < out_len; ++i)
     46 			out += out_kernel[i] * out_history[i];
     47 
     48 		do_history(out_len, out_history, out);
     49 	}
     50 	return out;
     51 }
     52 
     53 float* fmalloc_or_die(unsigned n)
     54 {
     55 	if (!n)
     56 		return NULL;
     57 
     58 	float* p = malloc(n * sizeof(float));
     59 	if (!p)
     60 		die("malloc");
     61 
     62 	for (unsigned i = 0; i < n; ++i)
     63 		p[i] = 0;
     64 	return p;
     65 }
     66 
     67 void graph(float signal, float out)
     68 {
     69 	unsigned unseen = 7;
     70 	for (int i = -20; unseen && i < 100; ++i)
     71 	{
     72 		unsigned seen = 0;
     73 		if (!i)
     74 			seen |= 1;
     75 		if (unseen & 4)
     76 			if (i >= signal)
     77 				seen |= 4;
     78 		if (unseen & 2)
     79 			if (i >= out)
     80 				seen |= 2;
     81 
     82 		switch(seen)
     83 		{
     84 		case 1:
     85 			putchar('|');
     86 			break;
     87 		case 2:
     88 			putchar('-');
     89 			break;
     90 		case 3:
     91 		case 6:
     92 		case 7:
     93 			putchar('+');
     94 			break;
     95 		case 4:
     96 		case 5:
     97 			putchar('.');
     98 			break;
     99 
    100 		default:
    101 			putchar(' ');
    102 		}
    103 
    104 		unseen &= ~seen;
    105 	}
    106 	putchar('\n');
    107 }
    108 
    109 int main()
    110 {
    111 	in_len = 2;
    112 	out_len = 2;
    113 	in_history = fmalloc_or_die(in_len);
    114 	in_kernel = fmalloc_or_die(in_len);
    115 	out_history = fmalloc_or_die(out_len);
    116 	out_kernel = fmalloc_or_die(out_len);
    117 
    118 	in_kernel[0] = .4f;
    119 	in_kernel[1] = -.2f;
    120 	out_kernel[0] = 1.55f;
    121 	out_kernel[1] = -.75f;
    122 
    123 	float signal;
    124 	float out;
    125 	for (int i = 0; i < 50; ++i)
    126 	{
    127 		signal = i > 2 ? 50 : 0;
    128 
    129 		out = dsp(signal);
    130 		graph(signal, out);
    131 	}
    132 	printf("%.0f = %.0f\n", signal, out);
    133 }