Split the audio functionality and added repeat

The mechanics of the ALSA audio layer have been separated out into
a new file (with a view to making it more portable). Eventually I
will add SDL2 audio or OSS audio to make the code more portable.
In addition, I added a -r (repeat) option so it will repeat the
string.

Author: dtynan

Makefile

@@ -34,9 +34,18 @@
 # ABSTRACT
 # The build system for libmorse.a.
 #
-CFLAGS= -Wall -O
+LIBTOOL=ar
+#CFLAGS= -Wall -O -DSDL2
+CFLAGS= -Wall -O -DALSA
 
-SRCS=	init.c morse.c audio.c params.c
+#SND_SRC=sdl2.c
+#SND_INC=`sdl2-config --cflags`
+#SND_LIB=`sdl2-config --libs`
+SND_SRC=alsa.c
+SND_INC=
+SND_LIB=-lasound
+
+SRCS=	init.c morse.c audio.c params.c $(SND_SRC)
 OBJS=	$(SRCS:.c=.o)
 LIB=	libmorse.a
 
@@ -56,6 +65,9 @@ $(LIB):	$(OBJS)
 	$(AR) r $@ $?
 
 morse_play: main.o $(LIB)
-	$(CC) -o morse_play main.o -L. -lmorse -lasound -lm
+	$(CC) -o morse_play main.o -L. -lmorse $(SND_LIB) -lm
+
+sdl2.o:	sdl2.c
+	$(CC) $(CFLAGS) $(SND_INC) -c -o $@ sdl2.c
 
 $(OBJS): libmorse.h

alsa.c

@@ -0,0 +1,138 @@
+/*
+ * Copyright (c) 2022, Kalopa Robotics Limited.  All rights
+ * reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above
+ *    copyright notice, this list of conditions and the following
+ *    disclaimer in the documentation and/or other materials provided
+ *    with the distribution.
+ *
+ * 3. Neither the name of the copyright holder nor the names of its
+ *    contributors may be used to endorse or promote products derived
+ *    from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT
+ * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
+ * SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
+ * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * ABSTRACT
+ * This code handles the actual operation of creating a tone (or silence)
+ * for morse output. It relies heavily on the ALSA sound library for the
+ * dirty work of getting audio out.
+ */
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <math.h>
+
+#include "libmorse.h"
+
+#ifdef ALSA
+#include <alsa/asoundlib.h>
+
+static char		*device = "default";
+
+/*
+ * Initialise the ALSA library.
+ */
+void
+sound_open(struct morse *mp)
+{
+	int err;
+	snd_pcm_t *handle = NULL;
+
+	if ((err = snd_pcm_open(&handle, device, SND_PCM_STREAM_PLAYBACK, 0)) < 0) {
+		fprintf(stderr, "libmorse init: snd_pcm_open: %s\n", snd_strerror(err));
+		exit(1);
+	}
+	mp->audio = (void *)handle;
+}
+
+/*
+ * Just before we begin audio out, we need to set up some bits and pieces
+ * like the audio buffer and some of the offsets. Recompute the parameters
+ * for good measure, too.
+ */
+void
+sound_commence(struct morse *mp)
+{
+	int err;
+	snd_pcm_t *handle = (snd_pcm_t *)mp->audio;
+
+	if ((err = snd_pcm_set_params(handle,
+				SND_PCM_FORMAT_S16_LE,
+				SND_PCM_ACCESS_RW_INTERLEAVED,
+				1,
+				mp->sample_rate,
+				1,
+				500000)) < 0) {
+		fprintf(stderr, "libmorse: snd_pcm_set_params: %s\n", snd_strerror(err));
+		exit(1);
+	}
+}
+
+/*
+ * Output a 16-bit audio sample. It is buffered locally and then written
+ * whenever the buffer is full. We also track a time stamp so we know how
+ * much audio has been written.
+ */
+void
+sound_out(struct morse *mp, int value)
+{
+	snd_pcm_t *handle = (snd_pcm_t *)mp->audio;
+
+	mp->buffer[mp->offset++] = value;
+	if (mp->offset >= AUDIO_BUFFER_SIZE) {
+		snd_pcm_writei(handle, mp->buffer, AUDIO_BUFFER_SIZE);
+		mp->offset = 0;
+	}
+	mp->time_stamp++;
+}
+
+/*
+ * Called prior to close. This ensure that any buffered audio is written and
+ * we wait until the audio has actually been sent. Don't bother with this
+ * code if you just want to exit or close down the library.
+ */
+void
+sound_drain(struct morse *mp)
+{
+	int err;
+	snd_pcm_t *handle = (snd_pcm_t *)mp->audio;
+
+	if (mp->offset > 0)
+		snd_pcm_writei(handle, mp->buffer, mp->offset);
+	if ((err = snd_pcm_drain(handle)) < 0)
+		fprintf(stderr, "libmorse drain: snd_pcm_drain: %s\n", snd_strerror(err));
+}
+
+/*
+ * Close the library. Doesn't do much except release the ALSA audio channel.
+ */
+void
+sound_close(struct morse *mp)
+{
+	snd_pcm_t *handle = (snd_pcm_t *)mp->audio;
+
+	snd_pcm_close(handle);
+}
+#endif
+#ifdef SDL
+#include <SDL_audio.h>
+#endif

audio.c

@@ -41,28 +41,8 @@
 #include <stdlib.h>
 #include <math.h>
 
-#include <alsa/asoundlib.h>
-
 #include "libmorse.h"
 
-/*
- * Output a 16-bit audio sample. It is buffered locally and then written
- * whenever the buffer is full. We also track a time stamp so we know how
- * much audio has been written.
- */
-static void
-_audio_out(struct morse *mp, int value)
-{
-	snd_pcm_t *handle = (snd_pcm_t *)mp->audio;
-
-	mp->buffer[mp->offset++] = value;
-	if (mp->offset >= AUDIO_BUFFER_SIZE) {
-		snd_pcm_writei(handle, mp->buffer, AUDIO_BUFFER_SIZE);
-		mp->offset = 0;
-	}
-	mp->time_stamp++;
-}
-
 /*
  * Generate a sinusoidal tone at the desired frequency. We use a small curve
  * at the end of the wave form to avoid clicks. The maths here might not be
@@ -85,7 +65,7 @@ morse_audio_tone(struct morse *mp, int len)
 		} else
 			value = (double )mp->word;
 		theta = (2.0 * M_PI * (double )i * (double )mp->tone_frequency / mp->sample_rate);
-		_audio_out(mp, (int )(value * sin(theta) + 0.5));
+		sound_out(mp, (int )(value * sin(theta) + 0.5));
 	}
 }
 
@@ -97,7 +77,7 @@ void
 morse_audio_silence(struct morse *mp)
 {
 	while (mp->sym_delay > 0) {
-		_audio_out(mp, 0);
+		sound_out(mp, 0);
 		mp->sym_delay--;
 	}
 }

init.c

@@ -38,21 +38,15 @@
 #include <unistd.h>
 #include <stdlib.h>
 
-#include <alsa/asoundlib.h>
-
 #include "libmorse.h"
 
-static char		*device = "default";
-
 /*
  * Initialize the Morse Code library. Called with the desired words per
  * minute (an integer in the range of 5 <= wpm <= 60).
  */
 struct morse *
 morse_init(int wpm)
 {
-	int err;
-	snd_pcm_t *handle;
 	struct morse *mp;
 
 	/*
@@ -68,42 +62,6 @@ morse_init(int wpm)
 	mp->sample_rate = 44100;
 	mp->tone_frequency = 800.0;
 	morse_calc_params(mp);
-	/*
-	 * Now initialize the audio output.
-	 */
-	if ((err = snd_pcm_open(&handle, device, SND_PCM_STREAM_PLAYBACK, 0)) < 0) {
-		fprintf(stderr, "libmorse init: snd_pcm_open: %s\n", snd_strerror(err));
-		exit(1);
-	}
-	mp->audio = (void *)handle;
+	sound_open(mp);
 	return(mp);
 }
-
-/*
- * Called prior to close. This ensure that any buffered audio is written and
- * we wait until the audio has actually been sent. Don't bother with this
- * code if you just want to exit or close down the library.
- */
-void
-morse_drain(struct morse *mp)
-{
-	int err;
-	snd_pcm_t *handle = (snd_pcm_t *)mp->audio;
-
-	morse_audio_silence(mp);
-	if (mp->offset > 0)
-		snd_pcm_writei(handle, mp->buffer, mp->offset);
-	if ((err = snd_pcm_drain(handle)) < 0)
-		fprintf(stderr, "libmorse drain: snd_pcm_drain: %s\n", snd_strerror(err));
-}
-
-/*
- * Close the library. Doesn't do much except release the ALSA audio channel.
- */
-void
-morse_close(struct morse *mp)
-{
-	snd_pcm_t *handle = (snd_pcm_t *)mp->audio;
-
-	snd_pcm_close(handle);
-}

libmorse.h

@@ -78,9 +78,15 @@ struct morse	*morse_init(int);
 void			morse_send_char(struct morse *, int);
 void			morse_send_word(struct morse *, char *);
 void			morse_send_string(struct morse *, char *);
-void			morse_drain(struct morse *);
-void			morse_close(struct morse *);
 double			morse_timestamp(struct morse *);
 void			morse_calc_params(struct morse *);
 void			morse_audio_tone(struct morse *, int);
 void			morse_audio_silence(struct morse *);
+/*
+ * Platform-specific soundcard functions.
+ */
+void			sound_open(struct morse *);
+void			sound_commence(struct morse *);
+void			sound_out(struct morse *, int);
+void			sound_drain(struct morse *);
+void			sound_close(struct morse *);

main.c

@@ -59,14 +59,15 @@ void	usage();
 int
 main(int argc, char *argv[])
 {
-	int i, len, wpm, ampl, fw;
+	int i, len, wpm, ampl, fw, repeat;
 	char *str;
 	struct morse *mp;
 
 	wpm = 18;
 	opterr = fw = 0;
+	repeat = 1;
 	ampl = -1;
-	while ((i = getopt(argc, argv, "a:f:s:")) != EOF) {
+	while ((i = getopt(argc, argv, "a:f:s:r:")) != EOF) {
 		switch (i) {
 		case 'a':
 			if ((ampl = atoi(optarg)) < 0 || ampl > 100) {
@@ -91,6 +92,13 @@ main(int argc, char *argv[])
 			}
 			break;
 
+		case 'r':
+			if ((repeat = atoi(optarg)) < 1 || repeat > 100) {
+				fprintf(stderr, "Repeat count should be between 1 and 100.\n");
+				usage();
+			}
+			break;
+
 		default:
 			usage();
 			break;
@@ -117,10 +125,13 @@ main(int argc, char *argv[])
 		strcat(str, " ");
 		strcat(str, argv[optind]);
 	}
-	morse_send_string(mp, str);
-	morse_drain(mp);
+	for (i = 0; i < repeat; i++) {
+		morse_send_string(mp, str);
+		morse_audio_silence(mp);
+	}
+	sound_drain(mp);
 	printf("Total time: %.2f seconds.\n", morse_timestamp(mp));
-	morse_close(mp);
+	sound_close(mp);
 	exit(0);
 }
 

params.c

@@ -40,8 +40,6 @@
 #include <unistd.h>
 #include <stdlib.h>
 
-#include <alsa/asoundlib.h>
-
 #include "libmorse.h"
 
 #define MIN(a, b)	((a) < (b) ? (a) : (b))
@@ -120,22 +118,10 @@ morse_calc_params(struct morse *mp)
 void
 _morse_commence(struct morse *mp)
 {
-	int err;
-	snd_pcm_t *handle = (snd_pcm_t *)mp->audio;
-
 	morse_calc_params(mp);
 	mp->sym_delay = 0;
 	mp->time_stamp = 0;
-	if ((err = snd_pcm_set_params(handle,
-				SND_PCM_FORMAT_S16_LE,
-				SND_PCM_ACCESS_RW_INTERLEAVED,
-				1,
-				mp->sample_rate,
-				1,
-				500000)) < 0) {
-		fprintf(stderr, "libmorse: snd_pcm_set_params: %s\n", snd_strerror(err));
-		exit(1);
-	}
+	sound_commence(mp);
 	mp->buffer = (unsigned short *)malloc(AUDIO_BUFFER_SIZE * sizeof(unsigned short));
 	if (mp->buffer == NULL) {
 		perror("libmorse: malloc");