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94 lines
3.7 KiB
94 lines
3.7 KiB
/*
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* Copyright (C) 2019 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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#include <android-base/unique_fd.h>
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#include <binder/MemoryBase.h>
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#include <binder/MemoryHeapBase.h>
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#include <system/audio.h>
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namespace android::soundpool {
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class SoundDecoder;
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/**
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* Sound is a resource used by SoundPool, referenced by soundID.
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*
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* After loading, it is effectively const so no locking required.
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* However, in order to guarantee that all the values have been
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* written properly and read properly, we use the mState as an atomic synchronization
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* point. So if getState() shows READY, then all the other getters may
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* be safely read.
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*
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* Technical details:
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* We access the mState atomic value through memory_order_seq_cst
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*
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* https://en.cppreference.com/w/cpp/atomic/memory_order
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*
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* which provides memory barriers. So if the last value written by the SoundDecoder
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* is mState, then the compiler ensures no other prior writes by SoundDecoder will be
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* reordered afterwards, and memory barrier is placed (as necessary) to ensure the
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* cache is visible to other processors.
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*
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* Likewise, if the first value read by SoundPool is mState,
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* the compiler ensures no reads for that thread will be reordered before mState is read,
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* and a memory barrier is placed (as necessary) to ensure that the cache is properly
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* updated with other processor's writes before reading.
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*
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* See https://developer.android.com/training/articles/smp for discussions about
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* the variant load-acquire, store-release semantics.
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*/
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class Sound {
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friend SoundDecoder; // calls doLoad().
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public:
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enum sound_state : int32_t { LOADING, READY, DECODE_ERROR };
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// A sound starts in the LOADING state and transitions only once
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// to either READY or DECODE_ERROR when doLoad() is called.
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Sound(int soundID, int fd, int64_t offset, int64_t length);
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~Sound();
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int32_t getSoundID() const { return mSoundID; }
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int32_t getChannelCount() const { return mChannelCount; }
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uint32_t getSampleRate() const { return mSampleRate; }
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audio_format_t getFormat() const { return mFormat; }
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audio_channel_mask_t getChannelMask() const { return mChannelMask; }
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size_t getSizeInBytes() const { return mSizeInBytes; }
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sound_state getState() const { return mState; }
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uint8_t* getData() const { return static_cast<uint8_t*>(mData->unsecurePointer()); }
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sp<IMemory> getIMemory() const { return mData; }
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private:
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status_t doLoad(); // only SoundDecoder accesses this.
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size_t mSizeInBytes = 0;
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const int32_t mSoundID;
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uint32_t mSampleRate = 0;
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std::atomic<sound_state> mState = LOADING; // used as synchronization point
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int32_t mChannelCount = 0;
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audio_format_t mFormat = AUDIO_FORMAT_INVALID;
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audio_channel_mask_t mChannelMask = AUDIO_CHANNEL_NONE;
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base::unique_fd mFd; // initialized in constructor, reset to -1 after loading
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const int64_t mOffset; // int64_t to match java long, see off64_t
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const int64_t mLength; // int64_t to match java long, see off64_t
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sp<IMemory> mData;
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sp<MemoryHeapBase> mHeap;
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};
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} // namespace android::soundpool
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