diff --git a/common/zmaxheap.h b/common/zmaxheap.h
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+/* Copyright (C) 2013-2016, The Regents of The University of Michigan.
+All rights reserved.
+This software was developed in the APRIL Robotics Lab under the
+direction of Edwin Olson, ebolson@umich.edu. This software may be
+available under alternative licensing terms; contact the address above.
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+1. Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+2. 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.
+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 COPYRIGHT OWNER 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.
+The views and conclusions contained in the software and documentation are those
+of the authors and should not be interpreted as representing official policies,
+either expressed or implied, of the Regents of The University of Michigan.
+*/
+
+#pragma once
+
+#include <stdio.h>
+
+typedef struct zmaxheap zmaxheap_t;
+
+typedef struct zmaxheap_iterator zmaxheap_iterator_t;
+struct zmaxheap_iterator {
+    zmaxheap_t *heap;
+    int in, out;
+};
+
+zmaxheap_t *zmaxheap_create(size_t el_sz);
+
+void zmaxheap_vmap(zmaxheap_t *heap, void (*f)());
+
+void zmaxheap_destroy(zmaxheap_t *heap);
+
+void zmaxheap_add(zmaxheap_t *heap, void *p, float v);
+
+int zmaxheap_size(zmaxheap_t *heap);
+
+// returns 0 if the heap is empty, so you can do
+// while (zmaxheap_remove_max(...)) { }
+int zmaxheap_remove_max(zmaxheap_t *heap, void *p, float *v);
+
+////////////////////////////////////////////
+// This is a peculiar iterator intended to support very specific (and
+// unusual) applications, and the heap is not necessarily in a valid
+// state until zmaxheap_iterator_finish is called.  Consequently, do
+// not call any other methods on the heap while iterating through.
+
+// you must provide your own storage for the iterator, and pass in a
+// pointer.
+void zmaxheap_iterator_init(zmaxheap_t *heap, zmaxheap_iterator_t *it);
+
+// Traverses the heap in top-down/left-right order. makes a copy of
+// the content into memory (p) that you provide.
+int zmaxheap_iterator_next(zmaxheap_iterator_t *it, void *p, float *v);
+
+// will set p to be a pointer to the heap's internal copy of the dfata.
+int zmaxheap_iterator_next_volatile(zmaxheap_iterator_t *it, void *p, float *v);
+
+// remove the current element.
+void zmaxheap_iterator_remove(zmaxheap_iterator_t *it);
+
+// call after all iterator operations are done. After calling this,
+// the iterator should no longer be used, but the heap methods can be.
+void zmaxheap_iterator_finish(zmaxheap_iterator_t *it);