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diff --git a/src/ipa/raspberrypi/controller/histogram.h b/src/ipa/raspberrypi/controller/histogram.h
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+++ b/src/ipa/raspberrypi/controller/histogram.h
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+/* SPDX-License-Identifier: BSD-2-Clause */
+/*
+ * Copyright (C) 2019, Raspberry Pi (Trading) Limited
+ *
+ * histogram.h - histogram calculation interface
+ */
+#pragma once
+
+#include <stdint.h>
+#include <vector>
+#include <cassert>
+
+/*
+ * A simple histogram class, for use in particular to find "quantiles" and
+ * averages between "quantiles".
+ */
+
+namespace RPiController {
+
+class Histogram
+{
+public:
+	template<typename T> Histogram(T *histogram, int num)
+	{
+		assert(num);
+		cumulative_.reserve(num + 1);
+		cumulative_.push_back(0);
+		for (int i = 0; i < num; i++)
+			cumulative_.push_back(cumulative_.back() +
+					      histogram[i]);
+	}
+	uint32_t bins() const { return cumulative_.size() - 1; }
+	uint64_t total() const { return cumulative_[cumulative_.size() - 1]; }
+	/* Cumulative frequency up to a (fractional) point in a bin. */
+	uint64_t cumulativeFreq(double bin) const;
+	/*
+	 * Return the (fractional) bin of the point q (0 <= q <= 1) through the
+	 * histogram. Optionally provide limits to help.
+	 */
+	double quantile(double q, int first = -1, int last = -1) const;
+	/* Return the average histogram bin value between the two quantiles. */
+	double interQuantileMean(double qLo, double qHi) const;
+
+private:
+	std::vector<uint64_t> cumulative_;
+};
+
+} /* namespace RPiController */