1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
|
/* SPDX-License-Identifier: GPL-2.0-or-later */
/* SPDX-FileCopyrightText: 2013 Free Software Foundation, Inc. */
/* Usage: parec --channels=1 --rate=48000 --format=s16le | ./spkmodem-recv */
/* Forked from coreboot's version, at util/spkmodem_recv/ in coreboot.git,
* revision 5c2b5fcf2f9c9259938fd03cfa3ea06b36a007f0 as of 3 January 2022.
* This version is heavily modified, re-written based on OpenBSD Kernel Source
* File Style Guide (KNF); this change is Copyright 2023,2026 Leah Rowe. */
#define _POSIX_SOURCE
#ifdef __OpenBSD__
#include <sys/param.h>
#endif
#include <errno.h>
#include <stdio.h>
#include <stdarg.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
static int set_ascii_bit(void);
static void handle_audio(void), decode_pulse(void), print_char(void),
print_stats(void);
static void err(int nvm_errval, const char *msg, ...);
static const char * getnvmprogname(void);
static void set_err_if_unset(int x);
int getopt(int, char * const *, const char *);
extern char *optarg;
extern int optind, opterr, optopt;
#if defined(__OpenBSD__) && defined(OpenBSD)
#if OpenBSD >= 509
#ifndef HAVE_PLEDGE
#define HAVE_PLEDGE 1
#endif
#endif
#endif
#define SAMPLES_PER_FRAME 240
#define MAX_SAMPLES (2 * SAMPLES_PER_FRAME)
#define FREQ_SEP_MIN 5
#define FREQ_SEP_MAX 15
#define FREQ_DATA_MIN 15
#define FREQ_DATA_THRESHOLD 25
#define FREQ_DATA_MAX 60
#define THRESHOLD 500
#define reset_char() ascii = 0, ascii_bit = 7
signed short frame[MAX_SAMPLES], pulse[MAX_SAMPLES];
int ringpos, debug, freq_data, freq_separator, sample_count, ascii_bit = 7;
char ascii = 0;
static const char *argv0;
int
main(int argc, char *argv[])
{
int c = 0;
argv0 = argv[0];
#ifdef HAVE_PLEDGE
#if HAVE_PLEDGE > 0
if (pledge("stdio", NULL) == -1)
err(errno, "pledge");
#endif
#endif
while (c != -1) {
c = getopt(argc, argv, "d");
if (c == 'd')
debug = 1;
else if (c != -1)
err(EINVAL, "Invalid argument");
}
setvbuf(stdout, NULL, _IONBF, 0);
while (1)
handle_audio();
return EXIT_SUCCESS;
}
static void
handle_audio(void)
{
int sample;
if (sample_count > (3 * SAMPLES_PER_FRAME))
sample_count = reset_char();
if ((freq_separator <= FREQ_SEP_MIN) || (freq_separator >= FREQ_SEP_MAX)
|| (freq_data <= FREQ_DATA_MIN) || (freq_data >= FREQ_DATA_MAX)) {
decode_pulse();
return;
}
if (set_ascii_bit() < 0)
print_char();
sample_count = 0;
for (sample = 0; sample < SAMPLES_PER_FRAME; sample++)
decode_pulse();
}
static void
decode_pulse(void)
{
size_t n;
int next_ringpos = (ringpos + SAMPLES_PER_FRAME) % MAX_SAMPLES;
freq_data -= pulse[ringpos];
freq_data += pulse[next_ringpos];
freq_separator -= pulse[next_ringpos];
n = fread(frame + ringpos, 1, sizeof(frame[0]), stdin);
if (n != sizeof(frame[0])) {
if (feof(stdin))
exit(EXIT_SUCCESS);
if (ferror(stdin))
err(errno, "Could not read from frame.");
}
pulse[ringpos] = (abs(frame[ringpos]) > THRESHOLD) ? 1 : 0;
freq_separator += pulse[ringpos++];
ringpos %= MAX_SAMPLES;
++sample_count;
}
static int
set_ascii_bit(void)
{
if (debug)
print_stats();
if (freq_data < FREQ_DATA_THRESHOLD)
ascii |= (1 << ascii_bit);
--ascii_bit;
return ascii_bit;
}
static void
print_stats(void)
{
long stdin_pos;
if ((stdin_pos = ftell(stdin)) == -1)
err(errno, "ftell stdin");
printf ("%d %d %d @%ld\n", freq_data, freq_separator,
FREQ_DATA_THRESHOLD, stdin_pos - sizeof(frame));
}
static void
print_char(void)
{
if (debug)
printf("<%c, %x>", ascii, ascii);
else
printf("%c", ascii);
reset_char();
}
static void
err(int nvm_errval, const char *msg, ...)
{
va_list args;
fprintf(stderr, "%s: ", getnvmprogname());
va_start(args, msg);
vfprintf(stderr, msg, args);
va_end(args);
set_err_if_unset(nvm_errval);
fprintf(stderr, ": %s", strerror(errno));
fprintf(stderr, "\n");
exit(EXIT_FAILURE);
}
static const char *
getnvmprogname(void)
{
const char *p;
if (argv0 == NULL || *argv0 == '\0')
return "";
p = strrchr(argv0, '/');
if (p)
return p + 1;
else
return argv0;
}
static void
set_err_if_unset(int x)
{
if (errno)
return;
if (x > 0)
errno = x;
else
errno = ECANCELED;
}
|
