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diff --git a/LoopbackApp/app/src/main/cpp/audio_utils/fifo.h b/LoopbackApp/app/src/main/cpp/audio_utils/fifo.h
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+/*
+ * Copyright (C) 2015 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.
+ */
+
+#ifndef ANDROID_AUDIO_FIFO_H
+#define ANDROID_AUDIO_FIFO_H
+
+#include <stdlib.h>
+
+// FIXME use atomic_int_least32_t and new atomic operations instead of legacy Android ones
+// #include <stdatomic.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// Single writer, single reader non-blocking FIFO.
+// Writer and reader must be in same process.
+
+// No user-serviceable parts within.
+struct audio_utils_fifo {
+    // These fields are const after initialization
+    size_t     mFrameCount;   // max number of significant frames to be stored in the FIFO > 0
+    size_t     mFrameCountP2; // roundup(mFrameCount)
+    size_t     mFudgeFactor;  // mFrameCountP2 - mFrameCount, the number of "wasted" frames after
+                              // the end of mBuffer.  Only the indices are wasted, not any memory.
+    size_t     mFrameSize;    // size of each frame in bytes
+    void      *mBuffer;       // pointer to caller-allocated buffer of size mFrameCount frames
+
+    volatile int32_t mFront; // frame index of first frame slot available to read, or read index
+    volatile int32_t mRear;  // frame index of next frame slot available to write, or write index
+};
+
+// Initialize a FIFO object.
+// Input parameters:
+//  fifo        Pointer to the FIFO object.
+//  frameCount  Max number of significant frames to be stored in the FIFO > 0.
+//              If writes and reads always use the same count, and that count is a divisor of
+//              frameCount, then the writes and reads will never do a partial transfer.
+//  frameSize   Size of each frame in bytes.
+//  buffer      Pointer to a caller-allocated buffer of frameCount frames.
+void audio_utils_fifo_init(struct audio_utils_fifo *fifo, size_t frameCount, size_t frameSize,
+        void *buffer);
+
+// De-initialize a FIFO object.
+// Input parameters:
+//  fifo        Pointer to the FIFO object.
+void audio_utils_fifo_deinit(struct audio_utils_fifo *fifo);
+
+// Write to FIFO.
+// Input parameters:
+//  fifo        Pointer to the FIFO object.
+//  buffer      Pointer to source buffer containing 'count' frames of data.
+// Returns actual number of frames written <= count.
+// The actual transfer count may be zero if the FIFO is full,
+// or partial if the FIFO was almost full.
+// A negative return value indicates an error.  Currently there are no errors defined.
+ssize_t audio_utils_fifo_write(struct audio_utils_fifo *fifo, const void *buffer, size_t count);
+
+// Read from FIFO.
+// Input parameters:
+//  fifo        Pointer to the FIFO object.
+//  buffer      Pointer to destination buffer to be filled with up to 'count' frames of data.
+// Returns actual number of frames read <= count.
+// The actual transfer count may be zero if the FIFO is empty,
+// or partial if the FIFO was almost empty.
+// A negative return value indicates an error.  Currently there are no errors defined.
+ssize_t audio_utils_fifo_read(struct audio_utils_fifo *fifo, void *buffer, size_t count);
+
+size_t audio_utils_fifo_availToRead(struct audio_utils_fifo *fifo);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif  // !ANDROID_AUDIO_FIFO_H