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diff --git a/util/timehist.h b/util/timehist.h
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+/*
+ * util/timehist.h - make histogram of time values.
+ *
+ * Copyright (c) 2007, NLnet Labs. All rights reserved.
+ *
+ * This software is open source.
+ * 
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 
+ * Redistributions of source code must retain the above copyright notice,
+ * this list of conditions and the following disclaimer.
+ * 
+ * Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ * 
+ * Neither the name of the NLNET LABS nor the names of its contributors may
+ * be used to endorse or promote products derived from this software without
+ * specific prior written permission.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/**
+ * \file
+ *
+ * This file contains functions to make a histogram of time values.
+ */
+
+#ifndef UTIL_TIMEHIST_H
+#define UTIL_TIMEHIST_H
+
+/** Number of buckets in a histogram */
+#define NUM_BUCKETS_HIST 40
+
+/**
+ * Bucket of time history information
+ */
+struct th_buck {
+	/** lower bound */
+	struct timeval lower;
+	/** upper bound */
+	struct timeval upper;
+	/** number of items */
+	size_t count;
+};
+
+/**
+ * Keep histogram of time values.
+ */
+struct timehist {
+	/** number of buckets */
+	size_t num;
+	/** bucket array */
+	struct th_buck* buckets;
+};
+
+/** 
+ * Setup a histogram, default
+ * @return histogram or NULL on malloc failure.
+ */
+struct timehist* timehist_setup(void);
+
+/**
+ * Delete histogram
+ * @param hist: to delete
+ */
+void timehist_delete(struct timehist* hist);
+
+/**
+ * Clear histogram
+ * @param hist: to clear all data from
+ */
+void timehist_clear(struct timehist* hist);
+
+/**
+ * Add time value to histogram.
+ * @param hist: histogram
+ * @param tv: time value
+ */
+void timehist_insert(struct timehist* hist, struct timeval* tv);
+
+/**
+ * Find time value for given quartile, such as 0.25, 0.50, 0.75.
+ * The looks up the value for the i-th element in the sorted list of time 
+ * values, as approximated using the histogram.
+ * @param hist: histogram. Interpolated information is used from it.
+ * @param q: quartile, 0.50 results in the median. Must be >0 and <1.
+ * @return: the time in seconds for that percentage.
+ */
+double timehist_quartile(struct timehist* hist, double q);
+
+/**
+ * Printout histogram
+ * @param hist: histogram
+ */
+void timehist_print(struct timehist* hist);
+
+/**
+ * Log histogram, print it to the logfile.
+ * @param hist: histogram
+ * @param name: the name of the value column
+ */
+void timehist_log(struct timehist* hist, const char* name);
+
+/**
+ * Export histogram to an array.
+ * @param hist: histogram
+ * @param array: the array to export to.
+ * @param sz: number of items in array.
+ */
+void timehist_export(struct timehist* hist, size_t* array, size_t sz);
+
+/**
+ * Import histogram from an array.
+ * @param hist: histogram
+ * @param array: the array to import from.
+ * @param sz: number of items in array.
+ */
+void timehist_import(struct timehist* hist, size_t* array, size_t sz);
+
+#endif /* UTIL_TIMEHIST_H */