1 /*
2 * Copyright (C) 2012 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_TAG "MonoPipe"
18 //#define LOG_NDEBUG 0
19
20 #include <cutils/atomic.h>
21 #include <cutils/compiler.h>
22 #include <utils/Log.h>
23 #include <utils/Trace.h>
24 #include "MonoPipe.h"
25 #include "roundup.h"
26
27 namespace android {
28
MonoPipe(size_t reqFrames,NBAIO_Format format,bool writeCanBlock)29 MonoPipe::MonoPipe(size_t reqFrames, NBAIO_Format format, bool writeCanBlock) :
30 NBAIO_Sink(format),
31 mReqFrames(reqFrames),
32 mMaxFrames(roundup(reqFrames)),
33 mBuffer(malloc(mMaxFrames * Format_frameSize(format))),
34 mFront(0),
35 mRear(0),
36 mWriteTsValid(false),
37 // mWriteTs
38 mSetpoint((reqFrames * 11) / 16),
39 mWriteCanBlock(writeCanBlock)
40 {
41 }
42
~MonoPipe()43 MonoPipe::~MonoPipe()
44 {
45 free(mBuffer);
46 }
47
availableToWrite() const48 ssize_t MonoPipe::availableToWrite() const
49 {
50 if (CC_UNLIKELY(!mNegotiated)) {
51 return NEGOTIATE;
52 }
53 // uses mMaxFrames not mReqFrames, so allows "over-filling" the pipe beyond requested limit
54 ssize_t ret = mMaxFrames - (mRear - android_atomic_acquire_load(&mFront));
55 ALOG_ASSERT((0 <= ret) && (ret <= mMaxFrames));
56 return ret;
57 }
58
write(const void * buffer,size_t count)59 ssize_t MonoPipe::write(const void *buffer, size_t count)
60 {
61 if (CC_UNLIKELY(!mNegotiated)) {
62 return NEGOTIATE;
63 }
64 size_t totalFramesWritten = 0;
65 while (count > 0) {
66 // can't return a negative value, as we already checked for !mNegotiated
67 size_t avail = availableToWrite();
68 size_t written = avail;
69 if (CC_LIKELY(written > count)) {
70 written = count;
71 }
72 size_t rear = mRear & (mMaxFrames - 1);
73 size_t part1 = mMaxFrames - rear;
74 if (part1 > written) {
75 part1 = written;
76 }
77 if (CC_LIKELY(part1 > 0)) {
78 memcpy((char *) mBuffer + (rear << mBitShift), buffer, part1 << mBitShift);
79 if (CC_UNLIKELY(rear + part1 == mMaxFrames)) {
80 size_t part2 = written - part1;
81 if (CC_LIKELY(part2 > 0)) {
82 memcpy(mBuffer, (char *) buffer + (part1 << mBitShift), part2 << mBitShift);
83 }
84 }
85 android_atomic_release_store(written + mRear, &mRear);
86 totalFramesWritten += written;
87 }
88 if (!mWriteCanBlock) {
89 break;
90 }
91 count -= written;
92 buffer = (char *) buffer + (written << mBitShift);
93 // Simulate blocking I/O by sleeping at different rates, depending on a throttle.
94 // The throttle tries to keep the mean pipe depth near the setpoint, with a slight jitter.
95 uint32_t ns;
96 if (written > 0) {
97 size_t filled = (mMaxFrames - avail) + written;
98 // FIXME cache these values to avoid re-computation
99 if (filled <= mSetpoint / 2) {
100 // pipe is (nearly) empty, fill quickly
101 ns = written * ( 500000000 / Format_sampleRate(mFormat));
102 } else if (filled <= (mSetpoint * 3) / 4) {
103 // pipe is below setpoint, fill at slightly faster rate
104 ns = written * ( 750000000 / Format_sampleRate(mFormat));
105 } else if (filled <= (mSetpoint * 5) / 4) {
106 // pipe is at setpoint, fill at nominal rate
107 ns = written * (1000000000 / Format_sampleRate(mFormat));
108 } else if (filled <= (mSetpoint * 3) / 2) {
109 // pipe is above setpoint, fill at slightly slower rate
110 ns = written * (1150000000 / Format_sampleRate(mFormat));
111 } else if (filled <= (mSetpoint * 7) / 4) {
112 // pipe is overflowing, fill slowly
113 ns = written * (1350000000 / Format_sampleRate(mFormat));
114 } else {
115 // pipe is severely overflowing
116 ns = written * (1750000000 / Format_sampleRate(mFormat));
117 }
118 } else {
119 ns = count * (1350000000 / Format_sampleRate(mFormat));
120 }
121 if (ns > 999999999) {
122 ns = 999999999;
123 }
124 struct timespec nowTs;
125 bool nowTsValid = !clock_gettime(CLOCK_MONOTONIC, &nowTs);
126 // deduct the elapsed time since previous write() completed
127 if (nowTsValid && mWriteTsValid) {
128 time_t sec = nowTs.tv_sec - mWriteTs.tv_sec;
129 long nsec = nowTs.tv_nsec - mWriteTs.tv_nsec;
130 if (nsec < 0) {
131 --sec;
132 nsec += 1000000000;
133 }
134 if (sec == 0) {
135 if ((long) ns > nsec) {
136 ns -= nsec;
137 } else {
138 ns = 0;
139 }
140 }
141 }
142 if (ns > 0) {
143 const struct timespec req = {0, ns};
144 nanosleep(&req, NULL);
145 }
146 // record the time that this write() completed
147 if (nowTsValid) {
148 mWriteTs = nowTs;
149 if ((mWriteTs.tv_nsec += ns) >= 1000000000) {
150 mWriteTs.tv_nsec -= 1000000000;
151 ++mWriteTs.tv_sec;
152 }
153 }
154 mWriteTsValid = nowTsValid;
155 }
156 mFramesWritten += totalFramesWritten;
157 return totalFramesWritten;
158 }
159
setAvgFrames(size_t setpoint)160 void MonoPipe::setAvgFrames(size_t setpoint)
161 {
162 mSetpoint = setpoint;
163 }
164
165 } // namespace android
166