diff --git a/os/lib/circular-list.c b/os/lib/circular-list.c new file mode 100644 index 000000000..2c04d8418 --- /dev/null +++ b/os/lib/circular-list.c @@ -0,0 +1,157 @@ +/* + * 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 circular-singly-linked-list + * @{ + * + * \file + * Implementation of circular singly linked lists + */ +/*---------------------------------------------------------------------------*/ +#include "contiki.h" +#include "lib/circular-list.h" + +#include +#include +#include +/*---------------------------------------------------------------------------*/ +struct cl { + struct cl *next; +}; +/*---------------------------------------------------------------------------*/ +void +circular_list_init(circular_list_t cl) +{ + *cl = NULL; +} +/*---------------------------------------------------------------------------*/ +void * +circular_list_head(circular_list_t cl) +{ + return *cl; +} +/*---------------------------------------------------------------------------*/ +void * +circular_list_tail(circular_list_t cl) +{ + struct cl *this; + + if(*cl == NULL) { + return NULL; + } + + for(this = *cl; this->next != *cl; this = this->next); + + return this; +} +/*---------------------------------------------------------------------------*/ +void +circular_list_remove(circular_list_t cl, void *element) +{ + struct cl *this, *previous; + + if(*cl == NULL) { + return; + } + + /* + * We start traversing from the second element. + * The head will be visited last. We always update the list's head after + * removal, just in case we have just removed the head. + */ + previous = *cl; + this = previous->next; + + do { + if(this == element) { + previous->next = this->next; + *cl = this->next == this ? NULL : previous; + return; + } + previous = this; + this = this->next; + } while(this != ((struct cl *)*cl)->next); +} +/*---------------------------------------------------------------------------*/ +void +circular_list_add(circular_list_t cl, void *element) +{ + struct cl *head; + + if(element == NULL) { + return; + } + + /* Don't add twice */ + circular_list_remove(cl, element); + + head = *cl; + + if(head == NULL) { + /* If the list was empty, we update the new element to point to itself */ + ((struct cl *)element)->next = element; + } else { + /* If the list exists, we add the new element between the current head and + * the previously second element. */ + ((struct cl *)element)->next = head->next; + head->next = element; + } + + /* In all cases, the new element becomes the list's new head */ + *cl = element; +} +/*---------------------------------------------------------------------------*/ +unsigned long +circular_list_length(circular_list_t cl) +{ + unsigned long len = 1; + struct cl *this; + + if(circular_list_is_empty(cl)) { + return 0; + } + + for(this = *cl; this->next != *cl; this = this->next) { + len++; + } + + return len; +} +/*---------------------------------------------------------------------------*/ +bool +circular_list_is_empty(circular_list_t cl) +{ + return *cl == NULL ? true : false; +} +/*---------------------------------------------------------------------------*/ +/** @} */ diff --git a/os/lib/circular-list.h b/os/lib/circular-list.h new file mode 100644 index 000000000..2edcaf808 --- /dev/null +++ b/os/lib/circular-list.h @@ -0,0 +1,155 @@ +/* + * 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 circular-singly-linked-list Circular, singly-linked list + * + * This library provides functions for the creation and manipulation of + * circular, singly-linked lists. + * + * A circular, singly-linked list is declared using the CIRCULAR_LIST macro. + * 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 list. Application + * code must not modify this field directly. + * + * Functions that modify the list (add / remove) will, in the general case, + * update the list's head and item order. If you call one of these functions + * as part of a list traversal, it is advised to stop / restart traversing + * after the respective function returns. + * @{ + */ +/*---------------------------------------------------------------------------*/ +#ifndef CIRCULAR_LIST_H_ +#define CIRCULAR_LIST_H_ +/*---------------------------------------------------------------------------*/ +#include "contiki.h" + +#include +#include +#include +/*---------------------------------------------------------------------------*/ +/** + * \brief Define a circular, singly-linked list. + * + * This macro defines a circular, singly-linked list. + * + * 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 circular, singly-linked list. + */ +#define CIRCULAR_LIST(name) \ + static void *name##_circular_list = NULL; \ + static circular_list_t name = (circular_list_t)&name##_circular_list +/*---------------------------------------------------------------------------*/ +/** + * \brief The circular, singly-linked list datatype + */ +typedef void **circular_list_t; +/*---------------------------------------------------------------------------*/ +/** + * \brief Initialise a circular, singly-linked list. + * \param cl The circular, singly-linked list. + */ +void circular_list_init(circular_list_t cl); + +/** + * \brief Return the tail of a circular, singly-linked list. + * \param cl The circular, singly-linked list. + * \return A pointer to the list's head, or NULL if the list is empty + */ +void *circular_list_head(circular_list_t cl); + +/** + * \brief Return the tail of a circular, singly-linked list. + * \param cl The circular, singly-linked list. + * \return A pointer to the list's tail, or NULL if the list is empty + */ +void *circular_list_tail(circular_list_t cl); + +/** + * \brief Add an element to a circular, singly-linked list. + * \param cl The circular, singly-linked list. + * \param element A pointer to the element to be added. + * + * The caller should make no assumptions as to the position in the list of the + * new element. + * + * After this function returns, the list's head is not guaranteed to be the + * same as it was before the addition. + * + * Calling this function will update the list's head and item order. If you + * call this function as part of a list traversal, it is advised to stop + * traversing after this function returns. + */ +void circular_list_add(circular_list_t cl, void *element); + +/** + * \brief Remove an element from a circular, singly-linked list. + * \param cl The circular, singly-linked list. + * \param element A pointer to the element to be removed. + * + * After this function returns, the list's head is not guaranteed to be the + * same as it was before the addition. + * + * Calling this function will update the list's head and item order. If you + * call this function as part of a list traversal, it is advised to stop + * traversing after this function returns. + */ +void circular_list_remove(circular_list_t cl, void *element); + +/** + * \brief Get the length of a circular, singly-linked list. + * \param cl The circular, singly-linked list. + * \return The number of elements in the list + */ +unsigned long circular_list_length(circular_list_t cl); + +/** + * \brief Determine whether a circular, singly-linked list is empty. + * \param cl The circular, singly-linked list. + * \retval true The list is empty + * \retval false The list is not empty + */ +bool circular_list_is_empty(circular_list_t cl); +/*---------------------------------------------------------------------------*/ +#endif /* CIRCULAR_LIST_H_ */ +/*---------------------------------------------------------------------------*/ +/** + * @} + * @} + */