include/common/SC_FIFO.h

   1 /*
   2         SuperCollider real time audio synthesis system
   3     Copyright (c) 2002 James McCartney. All rights reserved.
   4         http://www.audiosynth.com
   5
   6     This program is free software; you can redistribute it and/or modify
   7     it under the terms of the GNU General Public License as published by
   8     the Free Software Foundation; either version 2 of the License, or
   9     (at your option) any later version.
  10
  11     This program is distributed in the hope that it will be useful,
  12     but WITHOUT ANY WARRANTY; without even the implied warranty of
  13     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14     GNU General Public License for more details.
  15
  16     You should have received a copy of the GNU General Public License
  17     along with this program; if not, write to the Free Software
  18     Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301  USA
  19 */
  20
  21 #ifndef SC_FIFO_H_INCLUDED
  22 #define SC_FIFO_H_INCLUDED
  23
  24 #ifdef __APPLE__
  25 # include <libkern/OSAtomic.h>
  26 #endif
  27
  28 #ifdef _WIN32
  29 # include <windows.h>
  30 #endif
  31
  32 template <class T, int N>
  33 class SC_FIFO
  34 {
  35 public:
  36         SC_FIFO()
  37                 : mMask(N - 1),
  38                   mReadHead(0),
  39                   mWriteHead(0)
  40         {}
  41
  42         void MakeEmpty() { mReadHead = mWriteHead; }
  43         bool IsEmpty() { return mReadHead == mWriteHead; }
  44         bool HasData() { return mReadHead != mWriteHead; }
  45
  46         bool Put(T data)
  47         {
  48                 long next = NextPos(mWriteHead);
  49                 if (next == mReadHead) return false; // fifo is full
  50                 mItems[next] = data;
  51 #ifdef __APPLE__
  52                 // we don't really need a compare and swap, but this happens to call
  53                 // the PowerPC memory barrier instruction lwsync.
  54                 OSAtomicCompareAndSwap32Barrier(mWriteHead, next, &mWriteHead);
  55 #elif defined(_WIN32)
  56                 InterlockedExchange(reinterpret_cast<volatile LONG*>(&mWriteHead),next);
  57 #else
  58                 mWriteHead = next;
  59 #endif
  60                 return true;
  61         }
  62
  63         T Get()
  64         {
  65                 //assert(HasData());
  66                 long next = NextPos(mReadHead);
  67                 T out = mItems[next];
  68 #ifdef __APPLE__
  69                 // we don't really need a compare and swap, but this happens to call
  70                 // the PowerPC memory barrier instruction lwsync.
  71                 OSAtomicCompareAndSwap32Barrier(mReadHead, next, &mReadHead);
  72 #elif  defined(_WIN32)
  73                 InterlockedExchange(reinterpret_cast<volatile LONG*>(&mReadHead),next);
  74 #else
  75                 mReadHead = next;
  76 #endif
  77                 return out;
  78         }
  79
  80         int Capacity() const { return N; }
  81
  82 private:
  83         int NextPos(int inPos) { return (inPos + 1) & mMask; }
  84
  85         long mMask;
  86
  87 #ifdef __APPLE__
  88         int32_t mReadHead, mWriteHead;
  89 #else
  90         volatile int mReadHead, mWriteHead;
  91 #endif
  92         T mItems[N];
  93 };
  94
  95 #endif // SC_FIFO_H_INCLUDED