From 83561839071c7e4015170459f9c542d262a08743 Mon Sep 17 00:00:00 2001
From: George Oikonomou <george@contiki-ng.org>
Date: Mon, 4 Dec 2017 17:13:28 +0000
Subject: [PATCH] Add stack library

This commit adds a stack library as a wrapper around the list library
---
 os/lib/stack.h | 143 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 143 insertions(+)
 create mode 100644 os/lib/stack.h

diff --git a/os/lib/stack.h b/os/lib/stack.h
new file mode 100644
index 000000000..8d56e46ef
--- /dev/null
+++ b/os/lib/stack.h
@@ -0,0 +1,143 @@
+/*
+ * Copyright (c) 2017, George Oikonomou - http://www.spd.gr
+ * Copyright (c) 2017, James Pope
+ * All rights reserved.
+ *
+ * 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.
+ * 3. Neither the name of the copyright holder 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
+ * COPYRIGHT HOLDER 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.
+ */
+/*---------------------------------------------------------------------------*/
+/**
+ * \addtogroup data
+ * @{
+ *
+ * \defgroup stack-data-structure Stack library
+ *
+ * This library provides functions for the creation and manipulation of
+ * stacks. The library is implemented as a wrapper around the list library.
+ *
+ * A stack is declared using the STACK macro. Stack elements must be
+ * allocated by the calling code and must be of a C struct datatype. In this
+ * struct, the first field must be a pointer called \e next. This field will
+ * be used by the library to maintain the stack. Application code must not
+ * modify this field directly.
+ * @{
+ */
+/*---------------------------------------------------------------------------*/
+#ifndef STACK_H_
+#define STACK_H_
+/*---------------------------------------------------------------------------*/
+#include "contiki.h"
+#include "lib/list.h"
+
+#include <stdbool.h>
+/*---------------------------------------------------------------------------*/
+/**
+ * \brief The stack data type
+ */
+typedef list_t stack_t;
+/*---------------------------------------------------------------------------*/
+/**
+ * \brief Define a stack.
+ *
+ * This macro defines a stack.
+ *
+ * The datatype for elements must be a C struct. The struct's first member must
+ * be a pointer called \e next. This is used internally by the library to
+ * maintain data structure integrity and must not be modified directly by
+ * application code.
+ *
+ * \param name The name of the stack.
+ */
+#define STACK(name) LIST(name)
+/*---------------------------------------------------------------------------*/
+struct stack {
+  struct stack *next;
+};
+/*---------------------------------------------------------------------------*/
+/**
+ * \brief Initialise a stack
+ * \param stack The stack
+ */
+static inline void
+stack_init(stack_t stack)
+{
+  list_init(stack);
+}
+/*---------------------------------------------------------------------------*/
+/**
+ * \brief Adds an element to the top of the stack
+ * \param stack The stack
+ * \param element A pointer to the element to be added
+ */
+static inline void
+stack_push(stack_t stack, void *element)
+{
+  list_push(stack, element);
+}
+/*---------------------------------------------------------------------------*/
+/**
+ * \brief Removes the top element from the stack
+ * \param stack The stack
+ * \return A pointer to the element popped
+ *
+ * If this function returns NULL if the stack was empty (stack underflow)
+ */
+static inline void *
+stack_pop(stack_t stack)
+{
+  return list_pop(stack);
+}
+/*---------------------------------------------------------------------------*/
+/**
+ * \brief Returns the top element of the stack, without popping it
+ * \param stack The stack
+ * \return A pointer to the element at the top of the stack
+ */
+static inline void *
+stack_peek(stack_t stack)
+{
+  return list_head(stack);
+}
+/*---------------------------------------------------------------------------*/
+/**
+ * \brief Check if a stack is empty
+ * \param stack The stack
+ * \retval true The stack is empty
+ * \retval false The stack has at least one element
+ */
+static inline bool
+stack_is_empty(stack_t stack)
+{
+  return *stack == NULL ? true : false;
+}
+/*---------------------------------------------------------------------------*/
+#endif /* STACK_H_ */
+/*---------------------------------------------------------------------------*/
+/**
+ * @}
+ * @}
+ */