1 files changed, 76 insertions, 0 deletions
diff --git a/dogwhistle.c b/dogwhistle.c
new file mode 100644
index 0000000..2d48b82
--- /dev/null
+++ b/dogwhistle.c
@@ -0,0 +1,76 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+#include <alsa/asoundlib.h>
+#include <math.h>
+
+/* TODO add support for 12, 14, 18 and 20, 22 kHz in addition to 16 kHz as well as custom frequencies */
+/* TODO add support for selecting output device and backend */
+/* TODO add support for selecting volume */
+/* TODO add support for pausing and exiting */
+
+#define UTYPE   uint32_t
+#define SMIN    INT32_MIN
+#define SMAX    INT32_MAX
+#define FORMAT  SND_PCM_FORMAT_U32
+
+#define SAMPLE_RATE  52000   /* Hz */
+#define LATENCY      100000  /* µs */
+
+USAGE("");
+
+
+int
+main(int argc, char *argv[])
+{
+	UTYPE *buffer;
+	snd_pcm_uframes_t i, buflen = SAMPLE_RATE;
+	snd_pcm_sframes_t n;
+	snd_pcm_t *sound_handle = NULL;
+	unsigned long int freq = 16000;
+	double volume = (double)0.1f, imul, omul;
+	int r;
+
+	NOFLAGS(argc);
+
+	/* Set up audio */
+	r = snd_pcm_open(&sound_handle, "default", SND_PCM_STREAM_PLAYBACK, 0);
+	if (r < 0)
+		eprintf("snd_pcm_open: %s\n", snd_strerror(r));
+	if (!sound_handle)
+		eprintf("snd_pcm_open:");
+
+	/* Configure audio */
+	r = snd_pcm_set_params(sound_handle, FORMAT, SND_PCM_ACCESS_RW_INTERLEAVED, 1 /* channels */,
+	                       SAMPLE_RATE, 1 /* allow resampling? */, LATENCY);
+	if (r < 0)
+		eprintf("snd_pcm_set_params: %s\n", snd_strerror(r));
+
+	/* Generate tone */
+	buffer = emallocn((size_t)buflen, sizeof(*buffer), 0);
+	omul = volume * SMAX * 2;
+	imul = 2 * (double)freq / (double)SAMPLE_RATE;
+#ifdef __GNUC__
+# pragma GCC diagnostic push
+# pragma GCC diagnostic ignored "-Wunsuffixed-float-constants"
+#endif
+	imul *= M_PI;
+#ifdef __GNUC__
+# pragma GCC diagnostic pop
+#endif
+	for (i = 0; i < buflen; i++)
+		buffer[i] = (UTYPE)(sin(imul * (double)i) * omul - SMIN);
+
+	/* Play tone */
+	for (;;) {
+		n = snd_pcm_writei(sound_handle, buffer, buflen);
+		if (n < 0)
+			n = snd_pcm_recover(sound_handle, (int)n, 0 /* do not print error reason? */);
+		if (n < 0)
+			eprintf("snd_pcm_writei: %s\n", snd_strerror((int)n));
+		if (n > 0 && (snd_pcm_uframes_t)n < buflen)
+			eprintf("short write from snd_pcm_writei\n");
+	}
+
+	snd_pcm_close(sound_handle);
+	return 0;
+}