mpmc-queue: add MPMC queue header

[model-checker-benchmarks.git] / mpmc-queue / mpmc-queue.h

diff --git a/mpmc-queue/mpmc-queue.h b/mpmc-queue/mpmc-queue.h
new file mode 100644 (file)
index 0000000..2fe5ad1
--- /dev/null
+++ b/mpmc-queue/mpmc-queue.h
@@ -0,0 +1,87 @@
+template <typename t_element, size_t t_size>
+struct mpmc_boundq_1_alt
+{
+private:
+
+       // elements should generally be cache-line-size padded :
+       nonatomic<t_element>  m_array[t_size];
+
+       // rdwr counts the reads & writes that have started
+       atomic<unsigned int>    m_rdwr;
+       // "read" and "written" count the number completed
+       atomic<unsigned int>    m_read;
+       atomic<unsigned int>    m_written;
+
+public:
+
+       mpmc_boundq_1_alt() : m_rdwr(0), m_read(0), m_written(0)
+       {
+       }
+
+       //-----------------------------------------------------
+
+       nonatomic<t_element> * read_fetch() {
+               unsigned int rdwr = m_rdwr($).load(mo_acquire);
+               unsigned int rd,wr;
+               for(;;) {
+                       rd = (rdwr>>16) & 0xFFFF;
+                       wr = rdwr & 0xFFFF;
+
+                       if ( wr == rd ) // empty
+                               return false;
+
+                       if ( m_rdwr($).compare_exchange_weak(rdwr,rdwr+(1<<16),mo_acq_rel) )
+                               break;
+               }
+
+               // (*1)
+               rl::backoff bo;
+               while ( (m_written($).load(mo_acquire) & 0xFFFF) != wr ) {
+                       bo.yield($);
+               }
+
+               nonatomic<t_element> * p = & ( m_array[ rd % t_size ] );
+
+               return p;
+       }
+
+       void read_consume() {
+               m_read($).fetch_add(1,mo_release);
+       }
+
+       //-----------------------------------------------------
+
+       nonatomic<t_element> * write_prepare() {
+               unsigned int rdwr = m_rdwr($).load(mo_acquire);
+               unsigned int rd,wr;
+               for(;;) {
+                       rd = (rdwr>>16) & 0xFFFF;
+                       wr = rdwr & 0xFFFF;
+
+                       if ( wr == ((rd + t_size)&0xFFFF) ) // full
+                               return NULL;
+
+                       if ( m_rdwr($).compare_exchange_weak(rdwr,(rd<<16) | ((wr+1)&0xFFFF),mo_acq_rel) )
+                               break;
+               }
+
+               // (*1)
+               rl::backoff bo;
+               while ( (m_read($).load(mo_acquire) & 0xFFFF) != rd ) {
+                       bo.yield($);
+               }
+
+               nonatomic<t_element> * p = & ( m_array[ wr % t_size ] );
+
+               return p;
+       }
+
+       void write_publish()
+       {
+               m_written($).fetch_add(1,mo_release);
+       }
+
+       //-----------------------------------------------------
+
+
+};