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+/*
+Copyright (c) 2018-2018, Troy D. Hanson   http://troydhanson.github.com/uthash/
+All rights reserved.
+
+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.
+
+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.
+*/
+
+#ifndef UTSTACK_H
+#define UTSTACK_H
+
+#define UTSTACK_VERSION 2.1.0
+
+/*
+ * This file contains macros to manipulate a singly-linked list as a stack.
+ *
+ * To use utstack, your structure must have a "next" pointer.
+ *
+ * ----------------.EXAMPLE -------------------------
+ * struct item {
+ *      int id;
+ *      struct item *next;
+ * }
+ *
+ * struct item *stack = NULL:
+ *
+ * int main() {
+ *      int count;
+ *      struct item *tmp;
+ *      struct item *item = malloc(sizeof *item);
+ *      item->id = 42;
+ *      STACK_COUNT(stack, tmp, count); assert(count == 0);
+ *      STACK_PUSH(stack, item);
+ *      STACK_COUNT(stack, tmp, count); assert(count == 1);
+ *      STACK_POP(stack, item);
+ *      free(item);
+ *      STACK_COUNT(stack, tmp, count); assert(count == 0);
+ * }
+ * --------------------------------------------------
+ */
+
+#define STACK_TOP(head) (head)
+
+#define STACK_EMPTY(head) (!(head))
+
+#define STACK_PUSH(head,add)                                         \
+    STACK_PUSH2(head,add,next)
+
+#define STACK_PUSH2(head,add,next)                                   \
+do {                                                                 \
+  (add)->next = (head);                                              \
+  (head) = (add);                                                    \
+} while (0)
+
+#define STACK_POP(head,result)                                       \
+    STACK_POP2(head,result,next)
+
+#define STACK_POP2(head,result,next)                                 \
+do {                                                                 \
+  (result) = (head);                                                 \
+  (head) = (head)->next;                                             \
+} while (0)
+
+#define STACK_COUNT(head,el,counter)                                 \
+    STACK_COUNT2(head,el,counter,next)                               \
+
+#define STACK_COUNT2(head,el,counter,next)                           \
+do {                                                                 \
+  (counter) = 0;                                                     \
+  for ((el) = (head); el; (el) = (el)->next) { ++(counter); }        \
+} while (0)
+
+#endif /* UTSTACK_H */