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1 /*
2  * Copyright (C) 2015 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #ifndef ANDROID_AUDIO_FIFO_H
18 #define ANDROID_AUDIO_FIFO_H
19 
20 #include <stdlib.h>
21 
22 // FIXME use atomic_int_least32_t and new atomic operations instead of legacy Android ones
23 // #include <stdatomic.h>
24 
25 #ifdef __cplusplus
26 extern "C" {
27 #endif
28 
29 // Single writer, single reader non-blocking FIFO.
30 // Writer and reader must be in same process.
31 
32 // No user-serviceable parts within.
33 struct audio_utils_fifo {
34     // These fields are const after initialization
35     size_t     mFrameCount;   // max number of significant frames to be stored in the FIFO > 0
36     size_t     mFrameCountP2; // roundup(mFrameCount)
37     size_t     mFudgeFactor;  // mFrameCountP2 - mFrameCount, the number of "wasted" frames after
38                               // the end of mBuffer.  Only the indices are wasted, not any memory.
39     size_t     mFrameSize;    // size of each frame in bytes
40     void      *mBuffer;       // pointer to caller-allocated buffer of size mFrameCount frames
41 
42     volatile int32_t mFront; // frame index of first frame slot available to read, or read index
43     volatile int32_t mRear;  // frame index of next frame slot available to write, or write index
44 };
45 
46 // Initialize a FIFO object.
47 // Input parameters:
48 //  fifo        Pointer to the FIFO object.
49 //  frameCount  Max number of significant frames to be stored in the FIFO > 0.
50 //              If writes and reads always use the same count, and that count is a divisor of
51 //              frameCount, then the writes and reads will never do a partial transfer.
52 //  frameSize   Size of each frame in bytes.
53 //  buffer      Pointer to a caller-allocated buffer of frameCount frames.
54 void audio_utils_fifo_init(struct audio_utils_fifo *fifo, size_t frameCount, size_t frameSize,
55         void *buffer);
56 
57 // De-initialize a FIFO object.
58 // Input parameters:
59 //  fifo        Pointer to the FIFO object.
60 void audio_utils_fifo_deinit(struct audio_utils_fifo *fifo);
61 
62 // Write to FIFO.
63 // Input parameters:
64 //  fifo        Pointer to the FIFO object.
65 //  buffer      Pointer to source buffer containing 'count' frames of data.
66 // Returns actual number of frames written <= count.
67 // The actual transfer count may be zero if the FIFO is full,
68 // or partial if the FIFO was almost full.
69 // A negative return value indicates an error.  Currently there are no errors defined.
70 ssize_t audio_utils_fifo_write(struct audio_utils_fifo *fifo, const void *buffer, size_t count);
71 
72 // Read from FIFO.
73 // Input parameters:
74 //  fifo        Pointer to the FIFO object.
75 //  buffer      Pointer to destination buffer to be filled with up to 'count' frames of data.
76 // Returns actual number of frames read <= count.
77 // The actual transfer count may be zero if the FIFO is empty,
78 // or partial if the FIFO was almost empty.
79 // A negative return value indicates an error.  Currently there are no errors defined.
80 ssize_t audio_utils_fifo_read(struct audio_utils_fifo *fifo, void *buffer, size_t count);
81 
82 size_t audio_utils_fifo_availToRead(struct audio_utils_fifo *fifo);
83 
84 #ifdef __cplusplus
85 }
86 #endif
87 
88 #endif  // !ANDROID_AUDIO_FIFO_H
89