From 4ebf7c893d3c6320531b9129608c814a3f80d169 Mon Sep 17 00:00:00 2001
From: John Tramm <john.tramm@gmail.com>
Date: Thu, 23 Jan 2020 18:29:51 +0000
Subject: [PATCH] initial commit of sharedarray object.

---
 include/openmc/shared_array.h | 93 +++++++++++++++++++++++++++++++++++
 1 file changed, 93 insertions(+)
 create mode 100644 include/openmc/shared_array.h

diff --git a/include/openmc/shared_array.h b/include/openmc/shared_array.h
new file mode 100644
index 0000000000..d0deafec6e
--- /dev/null
+++ b/include/openmc/shared_array.h
@@ -0,0 +1,93 @@
+#ifndef OPENMC_SHARED_ARRAY_H
+#define OPENMC_SHARED_ARRAY_H
+
+//! \file shared_array.h
+//! \brief Shared array data structure
+
+namespace openmc {
+
+//==============================================================================
+// Class declarations
+//==============================================================================
+
+template <typename T> 
+class SharedArray { 
+
+private: 
+  //==========================================================================
+  // Data members
+  std::unique_ptr<T[]> data_;
+  int64_t size_;
+  int64_t capacity_;
+
+public: 
+  //==========================================================================
+  // Constructors
+  
+  SharedArray()
+  {
+    capacity_ = 0;
+    size_ = 0;
+  }
+  
+  SharedArray(int64_t capacity) : capacity_(capacity)
+  {
+    data_ = std::make_unique<T[]>(capacity);
+    size_ = 0;
+  }
+  
+  //==========================================================================
+  // Methods and Accessors
+  
+  T& operator[](int64_t i) {return data_[i];}
+
+  void reserve(int64_t capacity)
+  {
+    data_ = std::make_unique<T[]>(capacity);
+    capacity_ = capacity;
+  }
+
+  //! Increases the size of the SharedArray by one and returns an index to the
+  //! last element of the array.
+  int64_t append()
+  {
+    // Atomically capture the index we want to write to
+    int64_t idx;
+    #pragma omp atomic capture
+    idx = size_++;
+
+    // Check that we haven't written off the end of the array
+    if (idx >= capacity_) {
+      #pragma omp atomic write
+      size_ = capacity_;
+      return -1;
+    }
+
+    return idx;
+  }
+
+  void clear()
+  {
+    data_.reset();
+    size_ = 0;
+    capacity_ = 0;
+  }
+
+  int64_t size()
+  {
+    int size;
+    #pragma omp atomic read
+    size = size_;
+    return size;
+  }
+
+  int64_t capacity()
+  {
+    return capacity_;
+  }
+
+}; 
+
+} // namespace openmc
+
+#endif // OPENMC_SHARED_ARRAY_H