169 lines
5.0 KiB
C++
169 lines
5.0 KiB
C++
/*
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File: LockFreeFIFO.h
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Abstract: Part of CoreAudio Utility Classes
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Version: 1.1
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Disclaimer: IMPORTANT: This Apple software is supplied to you by Apple
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Inc. ("Apple") in consideration of your agreement to the following
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terms, and your use, installation, modification or redistribution of
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this Apple software constitutes acceptance of these terms. If you do
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not agree with these terms, please do not use, install, modify or
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redistribute this Apple software.
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In consideration of your agreement to abide by the following terms, and
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subject to these terms, Apple grants you a personal, non-exclusive
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license, under Apple's copyrights in this original Apple software (the
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"Apple Software"), to use, reproduce, modify and redistribute the Apple
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Software, with or without modifications, in source and/or binary forms;
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provided that if you redistribute the Apple Software in its entirety and
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without modifications, you must retain this notice and the following
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text and disclaimers in all such redistributions of the Apple Software.
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Neither the name, trademarks, service marks or logos of Apple Inc. may
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be used to endorse or promote products derived from the Apple Software
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without specific prior written permission from Apple. Except as
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expressly stated in this notice, no other rights or licenses, express or
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implied, are granted by Apple herein, including but not limited to any
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patent rights that may be infringed by your derivative works or by other
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works in which the Apple Software may be incorporated.
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The Apple Software is provided by Apple on an "AS IS" basis. APPLE
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MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION
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THE IMPLIED WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS
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FOR A PARTICULAR PURPOSE, REGARDING THE APPLE SOFTWARE OR ITS USE AND
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OPERATION ALONE OR IN COMBINATION WITH YOUR PRODUCTS.
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IN NO EVENT SHALL APPLE BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL
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OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) ARISING IN ANY WAY OUT OF THE USE, REPRODUCTION,
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MODIFICATION AND/OR DISTRIBUTION OF THE APPLE SOFTWARE, HOWEVER CAUSED
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AND WHETHER UNDER THEORY OF CONTRACT, TORT (INCLUDING NEGLIGENCE),
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STRICT LIABILITY OR OTHERWISE, EVEN IF APPLE HAS BEEN ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE.
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Copyright (C) 2014 Apple Inc. All Rights Reserved.
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*/
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#include <libkern/OSAtomic.h>
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template <class ITEM>
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class LockFreeFIFOWithFree
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{
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LockFreeFIFOWithFree(); // private, unimplemented.
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public:
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LockFreeFIFOWithFree(UInt32 inMaxSize)
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: mReadIndex(0), mWriteIndex(0), mFreeIndex(0)
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{
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//assert(IsPowerOfTwo(inMaxSize));
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mItems = new ITEM[inMaxSize];
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mMask = inMaxSize - 1;
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}
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~LockFreeFIFOWithFree()
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{
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delete [] mItems;
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}
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void Reset()
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{
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FreeItems();
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mReadIndex = 0;
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mWriteIndex = 0;
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mFreeIndex = 0;
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}
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ITEM* WriteItem()
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{
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//printf("WriteItem %d %d\n", mReadIndex, mWriteIndex);
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FreeItems(); // free items on the write thread.
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int32_t nextWriteIndex = (mWriteIndex + 1) & mMask;
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if (nextWriteIndex == mFreeIndex) return NULL;
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return &mItems[mWriteIndex];
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}
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ITEM* ReadItem()
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{
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//printf("ReadItem %d %d\n", mReadIndex, mWriteIndex);
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if (mReadIndex == mWriteIndex) return NULL;
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return &mItems[mReadIndex];
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}
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void AdvanceWritePtr() { OSAtomicCompareAndSwap32(mWriteIndex, (mWriteIndex + 1) & mMask, &mWriteIndex); }
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void AdvanceReadPtr() { OSAtomicCompareAndSwap32(mReadIndex, (mReadIndex + 1) & mMask, &mReadIndex); }
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private:
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ITEM* FreeItem()
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{
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if (mFreeIndex == mReadIndex) return NULL;
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return &mItems[mFreeIndex];
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}
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void AdvanceFreePtr() { OSAtomicCompareAndSwap32(mFreeIndex, (mFreeIndex + 1) & mMask, &mFreeIndex); }
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void FreeItems()
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{
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ITEM* item;
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while ((item = FreeItem()) != NULL)
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{
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item->Free();
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AdvanceFreePtr();
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}
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}
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volatile int32_t mReadIndex, mWriteIndex, mFreeIndex;
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int32_t mMask;
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ITEM *mItems;
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};
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// Same as above but no free.
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template <class ITEM>
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class LockFreeFIFO
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{
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LockFreeFIFO(); // private, unimplemented.
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public:
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LockFreeFIFO(UInt32 inMaxSize)
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: mReadIndex(0), mWriteIndex(0)
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{
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//assert(IsPowerOfTwo(inMaxSize));
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mItems = new ITEM[inMaxSize];
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mMask = inMaxSize - 1;
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}
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~LockFreeFIFO()
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{
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delete [] mItems;
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}
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void Reset()
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{
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mReadIndex = 0;
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mWriteIndex = 0;
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}
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ITEM* WriteItem()
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{
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int32_t nextWriteIndex = (mWriteIndex + 1) & mMask;
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if (nextWriteIndex == mReadIndex) return NULL;
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return &mItems[mWriteIndex];
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}
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ITEM* ReadItem()
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{
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if (mReadIndex == mWriteIndex) return NULL;
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return &mItems[mReadIndex];
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}
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// the CompareAndSwap will always succeed. We use CompareAndSwap because it calls the PowerPC sync instruction,
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// plus any processor bug workarounds for various CPUs.
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void AdvanceWritePtr() { OSAtomicCompareAndSwap32(mWriteIndex, (mWriteIndex + 1) & mMask, &mWriteIndex); }
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void AdvanceReadPtr() { OSAtomicCompareAndSwap32(mReadIndex, (mReadIndex + 1) & mMask, &mReadIndex); }
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private:
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volatile int32_t mReadIndex, mWriteIndex;
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int32_t mMask;
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ITEM *mItems;
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};
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