From e6b41982824632cefec9615b008e8d21aba807ca Mon Sep 17 00:00:00 2001
From: Dan Petrisko <petrisko@cs.washington.edu>
Date: Mon, 16 Jan 2023 05:00:47 -0800
Subject: [PATCH] Adding SPSC queue

---
 .../bsg_manycore_spsc_queue.hpp               | 100 ++++++++++++++++++
 1 file changed, 100 insertions(+)
 create mode 100644 software/bsg_manycore_lib/bsg_manycore_spsc_queue.hpp

diff --git a/software/bsg_manycore_lib/bsg_manycore_spsc_queue.hpp b/software/bsg_manycore_lib/bsg_manycore_spsc_queue.hpp
new file mode 100644
index 000000000..632b807f6
--- /dev/null
+++ b/software/bsg_manycore_lib/bsg_manycore_spsc_queue.hpp
@@ -0,0 +1,100 @@
+
+#ifndef _BSG_MANYCORE_SPSC_QUEUE_HPP
+#define _BSG_MANYCORE_SPSC_QUEUE_HPP
+
+#include <bsg_manycore_atomic.h>
+
+template <typename T, int S>
+class bsg_manycore_spsc_queue_recv {
+private:
+    volatile T *buffer;
+    volatile int *count;
+    int rptr;
+
+public:
+    bsg_manycore_spsc_queue_recv(T *buffer, int *count) 
+        : buffer(buffer), count(count), rptr(0) { };
+
+    bool is_empty(void)
+    {
+        return *count == 0;
+    }
+
+    bool try_recv(T *data)
+    {
+        if (is_empty())
+        {
+            return false;
+        }
+
+        *data = buffer[rptr];
+        // Probably faster than modulo, but should see if compiler
+        //   optimizes...
+        if (++rptr == S)
+        {
+            rptr = 0;
+        }
+        bsg_fence();
+        bsg_amoadd(count, -1);
+
+        return true;
+    }
+
+    // TODO: Add timeout?
+    T recv(void)
+    {
+        T data;
+        while (1)
+        {
+            if (try_recv(&data)) break;
+        }
+
+        return data;
+    }
+};
+
+template <typename T, int S>
+class bsg_manycore_spsc_queue_send {
+private:
+    volatile T *buffer;
+    volatile int *count;
+    int wptr;
+
+public:
+    bsg_manycore_spsc_queue_send(T *buffer, int *count) 
+        : buffer(buffer), count(count), wptr(0) { };
+
+    bool is_full(void)
+    {
+        return (*count == S);
+    }
+
+    bool try_send(T data)
+    {
+        if (is_full()) return false;
+
+        buffer[wptr] = data;
+        // Probably faster than modulo, but should see if compiler
+        //   optimizes...
+        if (++wptr == S)
+        {
+            wptr = 0;
+        }
+        bsg_fence();
+        bsg_amoadd(count, 1);
+
+        return true;
+    }
+
+    // TODO: Add timeout?
+    void send(T data)
+    {
+        while (1)
+        {
+            if (try_send(data)) break;
+        }
+    }
+};
+
+#endif
+