Add peek to queue_spsc_atomic (ETLCPP#430)

kangbudz · Oct 1, 2021 · 71c8544 · 71c8544
1 parent 0754b33
commit 71c8544
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diff --git a/include/etl/queue_spsc_atomic.h b/include/etl/queue_spsc_atomic.h
@@ -365,6 +365,24 @@ namespace etl
     }
 #endif
 
+    //*************************************************************************
+    /// Peek the next value in the queue without removing it.
+    //*************************************************************************
+    bool peek(reference value)
+    {
+      size_type read_index = read.load(etl::memory_order_relaxed);
+
+      if (read_index == write.load(etl::memory_order_acquire))
+      {
+        // Queue is empty
+        return false;
+      }
+
+      value = p_buffer[read_index];
+
+      return true;
+    }
+
     //*************************************************************************
     /// Pop a value from the queue.
     //*************************************************************************

diff --git a/test/test_queue_spsc_atomic.cpp b/test/test_queue_spsc_atomic.cpp
@@ -271,6 +271,52 @@ namespace
       CHECK(!queue.pop());
     }
 
+    TEST(test_size_push_peek_pop)
+    {
+      etl::queue_spsc_atomic<int, 4> queue;
+
+      CHECK_EQUAL(0U, queue.size());
+
+      queue.push(1);
+      queue.push(2);
+      queue.push(3);
+      queue.push(4);
+      CHECK_EQUAL(4U, queue.size());
+
+      int i;
+
+      CHECK(queue.peek(i));
+      CHECK_EQUAL(1, i);
+      CHECK_EQUAL(4U, queue.size());
+
+      CHECK(queue.peek(i));
+      CHECK_EQUAL(1, i);
+      CHECK_EQUAL(4U, queue.size());
+
+      CHECK(queue.pop());
+      CHECK_EQUAL(3U, queue.size());
+
+      CHECK(queue.pop());
+      CHECK_EQUAL(2U, queue.size());
+
+      CHECK(queue.pop());
+      CHECK_EQUAL(1U, queue.size());
+
+      CHECK(queue.peek(i));
+      CHECK_EQUAL(4, i);
+      CHECK_EQUAL(1U, queue.size());
+
+      CHECK(queue.peek(i));
+      CHECK_EQUAL(4, i);
+      CHECK_EQUAL(1U, queue.size());
+
+      CHECK(queue.pop());
+      CHECK_EQUAL(0U, queue.size());
+
+      CHECK(!queue.peek(i));
+      CHECK(!queue.peek(i));
+    }
+
     //*************************************************************************
     TEST(test_multiple_emplace)
     {