无锁(lock-free)队列的一个简单实现

作为 无锁的 ( lock-free ) 线程安全算法 的一个习作吧。思想、算法十分简单。

#ifdef WIN32inline void sleep( uint32 mil ){Sleep( mil );}inline bool CAS(void* pDest, uint32 cmp, uint32 xchg){return InterlockedCompareExchange(reinterpret_cast<PLONG>(pDest),static_cast<LONG>(xchg), static_cast<LONG>(cmp)) == static_cast<LONG>(cmp);}inline int32 SafeInc(int32* pVal){return static_cast<int32>(InterlockedIncrement(reinterpret_cast<PLONG>(pVal)));}inline int32 SafeDec(int32* pVal){return static_cast<int32>(InterlockedDecrement(reinterpret_cast<PLONG>(pVal)));}#endif//这儿告诉编译器按照8字节对齐#ifdef _MSC_VER#pragma pack(push, 8)#endif /* _MSC_VER */template< typename T, int max_size=1024 >class Quese{public:Quese(){memset( _buf, 0, sizeof(T*) * max_size );_begin=_end=0; _size=0;}void push( T* pVal ){if( pVal==0 ) return;int32 cur;bool loop=true;do{if ( _size == max_size ) {sleep( 1 ); // TODO: 扩展continue;}cur=safe_move( &_end );;loop=!CAS( _buf + cur , 0, (uint32)pVal );}while( loop );SafeInc( (int32*)&_size );}T * pop(){int32 cur;T *p;do{if ( _size==0 ) return NULL;cur=safe_move( &_begin );p= _buf[cur];}while( p==0 || !CAS( _buf + cur, (uint32)p, 0 ) );SafeDec( (int32*)&_size );return p;}public:uint32 safe_move( volatile uint32* p ){uint32 next;uint32 cmp;do{cmp=*p;next=cmp+1;if( next >= max_size ) next=0;}while( !CAS( (uint32*)p, cmp, next ) );return cmp;}T* _buf[max_size];volatile uint32 _begin;volatile uint32 _end;volatile int32 _size;}; 

这个队列的大小是固定的，很多情况下应该够用了。