Jamoma API  0.6.0.a19
LockFreeFIFO.h
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41 #include <Carbon/Carbon.h>
42 
43 
44 template <class ITEM>
45 class LockFreeFIFOWithFree
46 {
47  LockFreeFIFOWithFree(); // private, unimplemented.
48 public:
49  LockFreeFIFOWithFree(UInt32 inMaxSize)
50  : mReadIndex(0), mWriteIndex(0), mFreeIndex(0)
51  {
52  //assert(IsPowerOfTwo(inMaxSize));
53  mItems = new ITEM[inMaxSize];
54  mMask = inMaxSize - 1;
55  }
56 
57  ~LockFreeFIFOWithFree()
58  {
59  delete [] mItems;
60  }
61 
62 
63  void Reset()
64  {
65  FreeItems();
66  mReadIndex = 0;
67  mWriteIndex = 0;
68  mFreeIndex = 0;
69  }
70 
71  ITEM* WriteItem()
72  {
73  //printf("WriteItem %d %d\n", mReadIndex, mWriteIndex);
74  FreeItems(); // free items on the write thread.
75  UInt32 nextWriteIndex = (mWriteIndex + 1) & mMask;
76  if (nextWriteIndex == mFreeIndex) return NULL;
77  return &mItems[mWriteIndex];
78  }
79 
80  ITEM* ReadItem()
81  {
82  //printf("ReadItem %d %d\n", mReadIndex, mWriteIndex);
83  if (mReadIndex == mWriteIndex) return NULL;
84  return &mItems[mReadIndex];
85  }
86 
87  // the CompareAndSwap will always succeed. We use CompareAndSwap because it calls the PowerPC sync instruction,
88  // plus any processor bug workarounds for various CPUs.
89  void AdvanceWritePtr() { CompareAndSwap(mWriteIndex, (mWriteIndex + 1) & mMask, (UInt32*)&mWriteIndex); }
90  void AdvanceReadPtr() { CompareAndSwap(mReadIndex, (mReadIndex + 1) & mMask, (UInt32*)&mReadIndex); }
91 
92 private:
93  ITEM* FreeItem()
94  {
95  if (mFreeIndex == mReadIndex) return NULL;
96  return &mItems[mFreeIndex];
97  }
98  void AdvanceFreePtr() { CompareAndSwap(mFreeIndex, (mFreeIndex + 1) & mMask, (UInt32*)&mFreeIndex); }
99 
100  void FreeItems()
101  {
102  ITEM* item;
103  while ((item = FreeItem()) != NULL)
104  {
105  item->Free();
106  AdvanceFreePtr();
107  }
108  }
109 
110  volatile UInt32 mReadIndex, mWriteIndex, mFreeIndex;
111  UInt32 mMask;
112  ITEM *mItems;
113 };
114 
115 
116 
117 // Same as above but no free.
118 
119 template <class ITEM>
120 class LockFreeFIFO
121 {
122  LockFreeFIFO(); // private, unimplemented.
123 public:
124  LockFreeFIFO(UInt32 inMaxSize)
125  : mReadIndex(0), mWriteIndex(0)
126  {
127  //assert(IsPowerOfTwo(inMaxSize));
128  mItems = new ITEM[inMaxSize];
129  mMask = inMaxSize - 1;
130  }
131 
132  ~LockFreeFIFO()
133  {
134  delete [] mItems;
135  }
136 
137  void Reset()
138  {
139  mReadIndex = 0;
140  mWriteIndex = 0;
141  }
142 
143  ITEM* WriteItem()
144  {
145  UInt32 nextWriteIndex = (mWriteIndex + 1) & mMask;
146  if (nextWriteIndex == mReadIndex) return NULL;
147  return &mItems[mWriteIndex];
148  }
149 
150  ITEM* ReadItem()
151  {
152  if (mReadIndex == mWriteIndex) return NULL;
153  return &mItems[mReadIndex];
154  }
155 
156  // the CompareAndSwap will always succeed. We use CompareAndSwap because it calls the PowerPC sync instruction,
157  // plus any processor bug workarounds for various CPUs.
158  void AdvanceWritePtr() { CompareAndSwap(mWriteIndex, (mWriteIndex + 1) & mMask, (UInt32*)&mWriteIndex); }
159  void AdvanceReadPtr() { CompareAndSwap(mReadIndex, (mReadIndex + 1) & mMask, (UInt32*)&mReadIndex); }
160 
161 private:
162 
163  volatile UInt32 mReadIndex, mWriteIndex;
164  UInt32 mMask;
165  ITEM *mItems;
166 };
167