From 26c62832420553f6f82ec3daeef6df08326fc922 Mon Sep 17 00:00:00 2001
From: XANTRONIX Development
Date: Tue, 18 Jan 2022 13:17:45 -0500
Subject: It compiles! Beep! Beep!

---
 src/Makefile |   4 +-
 src/mixer.c  | 206 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 208 insertions(+), 2 deletions(-)
 create mode 100644 src/mixer.c

(limited to 'src')

diff --git a/src/Makefile b/src/Makefile
index 3046c70..d638619 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -7,9 +7,9 @@ CC		 = $(CROSS)cc
 CFLAGS		+= -I$(INCLUDE_PATH)
 LDFLAGS		+=
 
-HEADERS		= audio.h riff.h
+HEADERS		= audio.h mixer.h riff.h
 
-OBJS		= audio.o riff.o
+OBJS		= audio.o mixer.o riff.o
 
 VERSION_MAJOR	= 0
 VERSION_MINOR	= 0.1
diff --git a/src/mixer.c b/src/mixer.c
new file mode 100644
index 0000000..da822bf
--- /dev/null
+++ b/src/mixer.c
@@ -0,0 +1,206 @@
+#include <stdlib.h>
+#include <string.h>
+#include <stdint.h>
+#include <math.h>
+#include <errno.h>
+
+#include <xas/audio.h>
+#include <xas/mixer.h>
+
+static void mixer_apply_int16_t_mono(int16_t *dest,
+                                     int16_t *src,
+                                     size_t count,
+                                     float bias_l,
+                                     float bias_r) {
+    size_t i;
+
+    for (i=0; i<count; i++) {
+        dest[i] += src[i];
+    }
+}
+
+static void mixer_apply_int16_t_stereo(int16_t *dest,
+                                       int16_t *src,
+                                       size_t count,
+                                       float bias_l,
+                                       float bias_r) {
+    size_t i;
+
+    for (i=0; i<2*count; i+=2) {
+        dest[i]   += (int16_t)roundf(src[i]   * bias_l);
+        dest[i+1] += (int16_t)roundf(src[i+1] * bias_r);
+    }
+}
+
+static ssize_t mixer_fill(xas_mixer *mixer,
+                          void *samples,
+                          size_t count,
+                          xas_audio_stream *output) {
+    ssize_t ret = 0;
+
+    xas_mixer_input *input = mixer->inputs;
+
+    void (*mixer_apply)(int16_t *,
+                        int16_t *,
+                        size_t,
+                        float,
+                        float) = (output->channels == 2)?
+        mixer_apply_int16_t_stereo:
+        mixer_apply_int16_t_mono;
+
+    memset(mixer->buf,
+           '\0',
+           output->sample_size * output->channels * output->buffer_size);
+
+    while (input) {
+        xas_mixer_input *next = input->next;
+
+        ssize_t readlen;
+
+        if ((readlen = xas_audio_stream_read(input->stream,
+                                               mixer->buf,
+                                               count)) < 0) {
+            goto error_audio_read_stream;
+        }
+
+        mixer_apply((int16_t *)mixer->buf,
+                    (int16_t *)(input + 1),
+                    readlen,
+                    input->bias_l,
+                    input->bias_r);
+
+        if (ret < readlen) {
+            ret = readlen;
+        }
+
+        input = next;
+    }
+
+    return ret;
+
+error_audio_read_stream:
+    return -1;
+}
+
+xas_mixer *xas_mixer_new(size_t sample_size,
+                             size_t sample_rate,
+                             size_t channels,
+                             size_t buffer_size) {
+    xas_mixer *mixer;
+
+    if ((mixer = malloc(sizeof(*mixer))) == NULL) {
+        goto error_malloc_mixer;
+    }
+
+    if ((mixer->buf = malloc(sample_size * channels * buffer_size)) == NULL) {
+        goto error_malloc_buf;
+    }
+
+    if ((mixer->output = xas_audio_stream_new_source((xas_audio_fill)mixer_fill,
+                                                       NULL,
+                                                       mixer,
+                                                       sample_size,
+                                                       sample_rate,
+                                                       channels,
+                                                       buffer_size)) == NULL) {
+        goto error_audio_stream_new_source;
+    }
+
+    mixer->inputs      = NULL;
+    mixer->last        = NULL;
+    mixer->buffer_size = buffer_size;
+
+    return mixer;
+
+error_audio_stream_new_source:
+    free(mixer->buf);
+
+error_malloc_buf:
+    free(mixer);
+
+error_malloc_mixer:
+    return NULL;
+}
+
+void xas_mixer_destroy(xas_mixer *mixer) {
+    xas_mixer_input *input = mixer->inputs;
+
+    while (input) {
+        xas_mixer_input *next = input;
+
+        free(input);
+
+        input = next;
+    }
+
+    xas_audio_stream_destroy(mixer->output);
+
+    free(mixer);
+}
+
+static inline void input_set_pan(xas_mixer_input *input, float pan) {
+    float angle,
+          term,
+          cosf_angle,
+          sinf_angle;
+
+    if (pan < -1.0 || pan > 1.0) {
+        return;
+    }
+
+    angle      = pan * (M_PI / 2.0f);
+    term       = sqrtf(2.0f) / 2.0f;
+    cosf_angle = cosf(angle);
+    sinf_angle = sinf(angle);
+
+    input->bias_l = term * (cosf_angle + sinf_angle);
+    input->bias_r = term * (cosf_angle - sinf_angle);
+}
+
+xas_mixer_input *xas_mixer_input_add(xas_mixer *mixer,
+                                         xas_audio_stream *stream,
+                                         float gain,
+                                         float pan) {
+    xas_mixer_input *input;
+
+    if (stream->sample_size != mixer->output->sample_size
+     || stream->sample_rate != mixer->output->sample_rate
+     || stream->channels    != mixer->output->channels
+     || stream->buffer_size != mixer->buffer_size) {
+        errno = EINVAL;
+
+        goto error_invalid_stream;
+    }
+
+    if ((input = malloc(sizeof(*input))) == NULL) {
+        goto error_malloc_input;
+    }
+
+    input->stream = stream;
+    input->gain   = gain;
+
+    input_set_pan(input, pan);
+
+    if (mixer->inputs == NULL) {
+        mixer->inputs = input;
+        mixer->last   = NULL;
+    }
+
+    return input;
+
+error_malloc_input:
+error_invalid_stream:
+    return NULL;
+}
+
+void xas_mixer_input_set_gain(xas_mixer_input *input, float gain) {
+    if (gain < 0.0 || gain > 1.0) {
+        return;
+    }
+
+    input->gain = gain;
+}
+
+void xas_mixer_input_set_pan(xas_mixer_input *input, float pan) {
+    return input_set_pan(input, pan);
+}
-- 
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