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 //#define LOG_NDEBUG 0
18 #define LOG_TAG "audio_utils_fifo"
19
20 #include <stdlib.h>
21 #include <string.h>
22 #include "fifo.h"
23 #include "roundup.h"
24 #include "atomic.h"
25 //#include <cutils/log.h>
26 #define ALOG_ASSERT(exp)
27
audio_utils_fifo_init(struct audio_utils_fifo * fifo,size_t frameCount,size_t frameSize,void * buffer)28 void audio_utils_fifo_init(struct audio_utils_fifo *fifo, size_t frameCount, size_t frameSize,
29 void *buffer)
30 {
31 // We would need a 64-bit roundup to support larger frameCount.
32 ALOG_ASSERT(fifo != NULL && frameCount > 0 && frameSize > 0 && buffer != NULL);
33 fifo->mFrameCount = frameCount;
34 fifo->mFrameCountP2 = roundup(frameCount);
35 fifo->mFudgeFactor = fifo->mFrameCountP2 - fifo->mFrameCount;
36 fifo->mFrameSize = frameSize;
37 fifo->mBuffer = buffer;
38 fifo->mFront = 0;
39 fifo->mRear = 0;
40 }
41
audio_utils_fifo_deinit(struct audio_utils_fifo * fifo __unused)42 void audio_utils_fifo_deinit(struct audio_utils_fifo *fifo __unused)
43 {
44 }
45
46 // Return a new index as the sum of an old index (either mFront or mRear) and a specified increment.
audio_utils_fifo_sum(struct audio_utils_fifo * fifo,int32_t index,uint32_t increment)47 static inline int32_t audio_utils_fifo_sum(struct audio_utils_fifo *fifo, int32_t index,
48 uint32_t increment)
49 {
50 if (fifo->mFudgeFactor) {
51 uint32_t mask = fifo->mFrameCountP2 - 1;
52 ALOG_ASSERT((index & mask) < fifo->mFrameCount);
53 ALOG_ASSERT(/*0 <= increment &&*/ increment <= fifo->mFrameCountP2);
54 if ((index & mask) + increment >= fifo->mFrameCount) {
55 increment += fifo->mFudgeFactor;
56 }
57 index += increment;
58 ALOG_ASSERT((index & mask) < fifo->mFrameCount);
59 return index;
60 } else {
61 return index + increment;
62 }
63 }
64
65 // Return the difference between two indices: rear - front, where 0 <= difference <= mFrameCount.
audio_utils_fifo_diff(struct audio_utils_fifo * fifo,int32_t rear,int32_t front)66 static inline size_t audio_utils_fifo_diff(struct audio_utils_fifo *fifo, int32_t rear,
67 int32_t front)
68 {
69 int32_t diff = rear - front;
70 if (fifo->mFudgeFactor) {
71 uint32_t mask = ~(fifo->mFrameCountP2 - 1);
72 int32_t genDiff = (rear & mask) - (front & mask);
73 if (genDiff != 0) {
74 ALOG_ASSERT(genDiff == (int32_t) fifo->mFrameCountP2);
75 diff -= fifo->mFudgeFactor;
76 }
77 }
78 // FIFO should not be overfull
79 ALOG_ASSERT(0 <= diff && diff <= (int32_t) fifo->mFrameCount);
80 return (size_t) diff;
81 }
82
audio_utils_fifo_write(struct audio_utils_fifo * fifo,const void * buffer,size_t count)83 ssize_t audio_utils_fifo_write(struct audio_utils_fifo *fifo, const void *buffer, size_t count)
84 {
85 int32_t front = android_atomic_acquire_load(&fifo->mFront);
86 int32_t rear = fifo->mRear;
87 size_t availToWrite = fifo->mFrameCount - audio_utils_fifo_diff(fifo, rear, front);
88 if (availToWrite > count) {
89 availToWrite = count;
90 }
91 rear &= fifo->mFrameCountP2 - 1;
92 size_t part1 = fifo->mFrameCount - rear;
93 if (part1 > availToWrite) {
94 part1 = availToWrite;
95 }
96 if (part1 > 0) {
97 memcpy((char *) fifo->mBuffer + (rear * fifo->mFrameSize), buffer,
98 part1 * fifo->mFrameSize);
99 size_t part2 = availToWrite - part1;
100 if (part2 > 0) {
101 memcpy(fifo->mBuffer, (char *) buffer + (part1 * fifo->mFrameSize),
102 part2 * fifo->mFrameSize);
103 }
104 android_atomic_release_store(audio_utils_fifo_sum(fifo, fifo->mRear, availToWrite),
105 &fifo->mRear);
106 }
107 return availToWrite;
108 }
109
audio_utils_fifo_read(struct audio_utils_fifo * fifo,void * buffer,size_t count)110 ssize_t audio_utils_fifo_read(struct audio_utils_fifo *fifo, void *buffer, size_t count)
111 {
112 int32_t rear = android_atomic_acquire_load(&fifo->mRear);
113 int32_t front = fifo->mFront;
114 size_t availToRead = audio_utils_fifo_diff(fifo, rear, front);
115 if (availToRead > count) {
116 availToRead = count;
117 }
118 front &= fifo->mFrameCountP2 - 1;
119 size_t part1 = fifo->mFrameCount - front;
120 if (part1 > availToRead) {
121 part1 = availToRead;
122 }
123 if (part1 > 0) {
124 memcpy(buffer, (char *) fifo->mBuffer + (front * fifo->mFrameSize),
125 part1 * fifo->mFrameSize);
126 size_t part2 = availToRead - part1;
127 if (part2 > 0) {
128 memcpy((char *) buffer + (part1 * fifo->mFrameSize), fifo->mBuffer,
129 part2 * fifo->mFrameSize);
130 }
131 android_atomic_release_store(audio_utils_fifo_sum(fifo, fifo->mFront, availToRead),
132 &fifo->mFront);
133 }
134 return availToRead;
135 }
136