From fc91e00f0a533419695084ae08cc2217c5711a3b Mon Sep 17 00:00:00 2001
From: Hongwei Wang <hwwang@google.com>
Date: Tue, 10 Apr 2018 14:14:32 -0700
Subject: Simulates hardware gain control in audio driver

Change log
- audio_vbuffer in its own source and header files
- a pcm is shared via ext_pcm by multiple audio streams

Known issue
- Audio is distorted if multiple audio streams try to play
simultaneously. This is due to lack of proper audio mixing and will be
fixed in a future CL

Bug: 79496296
Test: manually

Change-Id: I14392e13ae49131a044efdda97ea23946287ad97
---
 emulator/audio/driver/audio_vbuffer.c | 137 ++++++++++++++++++++++++++++++++++
 1 file changed, 137 insertions(+)
 create mode 100644 emulator/audio/driver/audio_vbuffer.c

(limited to 'emulator/audio/driver/audio_vbuffer.c')

diff --git a/emulator/audio/driver/audio_vbuffer.c b/emulator/audio/driver/audio_vbuffer.c
new file mode 100644
index 0000000..79be545
--- /dev/null
+++ b/emulator/audio/driver/audio_vbuffer.c
@@ -0,0 +1,137 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_TAG "audio_hw_generic"
+
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <log/log.h>
+
+#include "audio_vbuffer.h"
+
+#define MIN(a, b) (((a) < (b)) ? (a) : (b))
+
+int audio_vbuffer_init(audio_vbuffer_t *audio_vbuffer, size_t frame_count,
+                       size_t frame_size) {
+  if (!audio_vbuffer) {
+    return -EINVAL;
+  }
+  audio_vbuffer->frame_size = frame_size;
+  audio_vbuffer->frame_count = frame_count;
+  size_t bytes = frame_count * frame_size;
+  audio_vbuffer->data = calloc(bytes, 1);
+  if (!audio_vbuffer->data) {
+    return -ENOMEM;
+  }
+  audio_vbuffer->head = 0;
+  audio_vbuffer->tail = 0;
+  audio_vbuffer->live = 0;
+  pthread_mutex_init(&audio_vbuffer->lock, (const pthread_mutexattr_t *)NULL);
+  return 0;
+}
+
+int audio_vbuffer_destroy(audio_vbuffer_t *audio_vbuffer) {
+  if (!audio_vbuffer) {
+    return -EINVAL;
+  }
+  free(audio_vbuffer->data);
+  pthread_mutex_destroy(&audio_vbuffer->lock);
+  return 0;
+}
+
+int audio_vbuffer_live(audio_vbuffer_t *audio_vbuffer) {
+  if (!audio_vbuffer) {
+    return -EINVAL;
+  }
+  pthread_mutex_lock(&audio_vbuffer->lock);
+  int live = audio_vbuffer->live;
+  pthread_mutex_unlock(&audio_vbuffer->lock);
+  return live;
+}
+
+int audio_vbuffer_dead(audio_vbuffer_t *audio_vbuffer) {
+  if (!audio_vbuffer) {
+    return -EINVAL;
+  }
+  pthread_mutex_lock(&audio_vbuffer->lock);
+  int dead = audio_vbuffer->frame_count - audio_vbuffer->live;
+  pthread_mutex_unlock(&audio_vbuffer->lock);
+  return dead;
+}
+
+size_t audio_vbuffer_write(audio_vbuffer_t *audio_vbuffer, const void *buffer,
+                           size_t frame_count) {
+  size_t frames_written = 0;
+  pthread_mutex_lock(&audio_vbuffer->lock);
+
+  while (frame_count != 0) {
+    int frames = 0;
+    if (audio_vbuffer->live == 0 || audio_vbuffer->head > audio_vbuffer->tail) {
+      frames =
+          MIN(frame_count, audio_vbuffer->frame_count - audio_vbuffer->head);
+    } else if (audio_vbuffer->head < audio_vbuffer->tail) {
+      frames = MIN(frame_count, audio_vbuffer->tail - (audio_vbuffer->head));
+    } else {
+      ALOGD("%s audio_vbuffer is full", __func__);
+      break;
+    }
+    memcpy(
+        &audio_vbuffer->data[audio_vbuffer->head * audio_vbuffer->frame_size],
+        &((uint8_t *)buffer)[frames_written * audio_vbuffer->frame_size],
+        frames * audio_vbuffer->frame_size);
+    audio_vbuffer->live += frames;
+    frames_written += frames;
+    frame_count -= frames;
+    audio_vbuffer->head =
+        (audio_vbuffer->head + frames) % audio_vbuffer->frame_count;
+  }
+
+  pthread_mutex_unlock(&audio_vbuffer->lock);
+  return frames_written;
+}
+
+size_t audio_vbuffer_read(audio_vbuffer_t *audio_vbuffer, void *buffer,
+                          size_t frame_count) {
+  size_t frames_read = 0;
+  pthread_mutex_lock(&audio_vbuffer->lock);
+
+  while (frame_count != 0) {
+    int frames = 0;
+    if (audio_vbuffer->live == audio_vbuffer->frame_count ||
+        audio_vbuffer->tail > audio_vbuffer->head) {
+      frames =
+          MIN(frame_count, audio_vbuffer->frame_count - audio_vbuffer->tail);
+    } else if (audio_vbuffer->tail < audio_vbuffer->head) {
+      frames = MIN(frame_count, audio_vbuffer->head - audio_vbuffer->tail);
+    } else {
+      break;
+    }
+    memcpy(
+        &((uint8_t *)buffer)[frames_read * audio_vbuffer->frame_size],
+        &audio_vbuffer->data[audio_vbuffer->tail * audio_vbuffer->frame_size],
+        frames * audio_vbuffer->frame_size);
+    audio_vbuffer->live -= frames;
+    frames_read += frames;
+    frame_count -= frames;
+    audio_vbuffer->tail =
+        (audio_vbuffer->tail + frames) % audio_vbuffer->frame_count;
+  }
+
+  pthread_mutex_unlock(&audio_vbuffer->lock);
+  return frames_read;
+}
-- 
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