Handout

kernel/object/bbuffer.h

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+// vim: set noet ts=4 sw=4:
+
+/*! \file
+ *  \brief Contains a \ref BBuffer "bounded buffer"
+ */
+
+#pragma once
+#include "../types.h"
+
+/*! \brief The class BBuffer implements a bounded buffer, that is a circular
+ *  buffer with a fixed capacity.
+ *
+ *  \tparam T the type of data to be stored
+ *  \tparam CAP the buffers capacity (must be greater than 1)
+ */
+template <typename T, unsigned CAP>
+class BBuffer {
+	static_assert(CAP > 1, "BBuffer of size 1 is unsupported.");
+	// Prevent copies and assignments
+	BBuffer(const BBuffer&) = delete;
+	BBuffer& operator=(const BBuffer&) = delete;
+
+   private:
+	T data[CAP] = {};
+	volatile unsigned in = 0;
+	volatile unsigned out = 0;
+
+   public:
+	/*! \brief Constructor that initialized an empty buffer.
+	 */
+	constexpr BBuffer() {}
+
+	/*! \brief Add an element to the buffer.
+	 *  \param val The element to be added.
+	 *  \return `false` if the buffer is full and no element can be added;
+	 * `true` otherwise.
+	 */
+	bool produce(T val) {
+		unsigned nextin = (in + 1) % CAP;
+		if (nextin != out) {
+			data[in] = val;
+			in = nextin;
+			return true;
+		}
+		return false;
+	}
+
+	/*! \brief Remove an element from the buffer.
+	 * \param val Output parameter that receives the next element. If there is
+	 *            (currently) no next element, `val` will not be modified.
+	 * \return `false` if the buffer was empty; `true` if the buffer was
+	 *          not empty and an element was written to val.
+	 */
+	bool consume(T& val) {
+		if (in != out) {
+			val = data[out];
+			out = (out + 1) % CAP;
+			return true;
+		}
+		return false;
+	}
+};