From 9c7d3117f422a7deb3e42d666ed9e2308438eaca Mon Sep 17 00:00:00 2001 From: Mattias Andrée Date: Tue, 22 Apr 2014 05:19:09 +0200 Subject: linked list implementation MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Signed-off-by: Mattias Andrée --- src/libmdsserver/linked-list.c | 396 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 396 insertions(+) create mode 100644 src/libmdsserver/linked-list.c (limited to 'src/libmdsserver/linked-list.c') diff --git a/src/libmdsserver/linked-list.c b/src/libmdsserver/linked-list.c new file mode 100644 index 0000000..b8cb35b --- /dev/null +++ b/src/libmdsserver/linked-list.c @@ -0,0 +1,396 @@ +/** + * mds — A micro-display server + * Copyright © 2014 Mattias Andrée (maandree@member.fsf.org) + * + * This program is free software: you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation, either version 3 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program. If not, see . + */ +#include "linked-list.h" + +#include + + +/** + * The default initial capacity + */ +#ifndef LINKED_LIST_DEFAULT_INITIAL_CAPACITY +#define LINKED_LIST_DEFAULT_INITIAL_CAPACITY 128 +#endif + + +/** + * Computes the nearest, but higher, power of two, + * but only if the current value is not a power of two + * + * @param value The value to be rounded up to a power of two + * @return The nearest, but not smaller, power of two + */ +static size_t to_power_of_two(size_t value) +{ + value -= 1; + value |= value >> 1; + value |= value >> 2; + value |= value >> 4; + value |= value >> 8; + value |= value >> 16; +#if __WORDSIZE == 64 + value |= value >> 32; +#endif + return value + 1; +} + + +/** + * Create a linked list + * + * @param this Memory slot in which to store the new linked list + * @param capacity The minimum initial capacity of the linked list, 0 for default + * @return Non-zero on error, `errno` will have been set accordingly + */ +int linked_list_create(linked_list_t* this, size_t capacity) +{ + /* Use default capacity of zero is specified. */ + if (capacity == 0) + capacity = LINKED_LIST_DEFAULT_INITIAL_CAPACITY; + + /* Initialise the linked list. */ + capacity = to_power_of_two(capacity); + this->capacity = capacity; + this->edge = 0; + this->end = 1; + this->reuse_head = 0; + this->reusable = NULL; + this->values = NULL; + this->next = NULL; + this->previous = NULL; + if ((this->reusable = malloc(capacity * sizeof(ssize_t))) == NULL) + return -1; + if ((this->values = malloc(capacity * sizeof(size_t))) == NULL) + return -1; + if ((this->next = malloc(capacity * sizeof(ssize_t))) == NULL) + return -1; + if ((this->previous = malloc(capacity * sizeof(ssize_t))) == NULL) + return -1; + this->values[this->edge] = 0; + this->next[this->edge] = this->edge; + this->previous[this->edge] = this->edge; + + return 0; +} + + +/** + * Release all resources in a linked list, should + * be done even if `linked_list_create` fails + * + * @param this The linked list + */ +void linked_list_destroy(linked_list_t* this) +{ + if (this->reusable != NULL) free(this->reusable); + if (this->values != NULL) free(this->values); + if (this->next != NULL) free(this->next); + if (this->previous != NULL) free(this->previous); + + this->reusable = NULL; + this->values = NULL; + this->next = NULL; + this->previous = NULL; +} + + +/** + * Clone a linked list + * + * @param this The linked list to clone + * @param out Memory slot in which to store the new linked list + * @return Non-zero on error, `errno` will have been set accordingly + */ +int linked_list_clone(linked_list_t* this, linked_list_t* out) +{ + size_t n = this->capacity * sizeof(ssize_t); + size_t* new_values; + ssize_t* new_next; + ssize_t* new_previous; + ssize_t* new_reusable; + + out->values = NULL; + out->next = NULL; + out->previous = NULL; + out->reusable = NULL; + + if ((new_values = malloc(n)) == NULL) + return -1; + if ((new_next = malloc(n)) == NULL) + { + free(new_values); + return -1; + } + if ((new_previous = malloc(n)) == NULL) + { + free(new_values); + free(new_previous); + return -1; + } + if ((new_reusable = malloc(n)) == NULL) + { + free(new_values); + free(new_previous); + free(new_reusable); + return -1; + } + + out->values = new_values; + out->next = new_next; + out->previous = new_previous; + out->reusable = new_reusable; + + out->capacity = this->capacity; + out->end = this->end; + out->reuse_head = this->reuse_head; + out->edge = this->edge; + + memcpy(out->values, this->values, n); + memcpy(out->next, this->next, n); + memcpy(out->previous, this->previous, n); + memcpy(out->reusable, this->reusable, n); + + return 0; +} + + +/** + * Pack the list so that there are no reusable + * positions, and reduce the capacity to the + * smallest capacity that can be used. Not that + * values (nodes) returned by the list's methods + * will become invalid. Additionally (to reduce + * the complexity) the list will be defragment + * so that the nodes' indices are continuous. + * This method has linear time complexity and + * linear memory complexity. + * + * @param this The list + * @return Non-zero on error, `errno` will have been set accordingly + */ +int linked_list_pack(linked_list_t* this) +{ + size_t size = this->end - this->reuse_head; + size_t cap = to_power_of_two(size); + ssize_t head = 0; + size_t i = 0; + ssize_t node; + size_t* vals; + + vals = malloc(cap * sizeof(size_t)); + if (vals == NULL) + return -1; + while (((size_t)head != this->end) && (this->next[head] == LINKED_LIST_UNUSED)) + head++; + if ((size_t)head != this->end) + for (node = head; (node != head) || (i == 0); i++) + { + vals[i] = this->values[node]; + node = this->next[node]; + } + + if (cap != this->capacity) + { + ssize_t* new_next; + ssize_t* new_previous; + ssize_t* new_reusable; + + new_next = malloc(cap * sizeof(ssize_t)); + if (new_next == NULL) + { + free(vals); + return -1; + } + new_previous = malloc(cap * sizeof(ssize_t)); + if (new_previous == NULL) + { + free(vals); + free(new_next); + return -1; + } + new_reusable = malloc(cap * sizeof(ssize_t)); + if (new_reusable == NULL) + { + free(vals); + free(new_next); + free(new_previous); + return -1; + } + + free(this->next); + free(this->previous); + free(this->reusable); + + this->next = new_next; + this->previous = new_previous; + this->reusable = new_reusable; + } + + for (i = 0; i < size; i++) + this->next[i] = (ssize_t)(i + 1); + this->next[size - 1] = 0; + + for (i = 1; i < size; i++) + this->previous[i] = (ssize_t)(i - 1); + this->previous[0] = (ssize_t)(size - 1); + + this->values = vals; + this->end = size; + this->reuse_head = 0; + + return 0; +} + + +/** + * Gets the next free position, and grow the + * arrays if necessary. This methods has constant + * amortised time complexity. + * + * @param this The list + * @return The next free position + */ +static ssize_t linked_list_get_next(linked_list_t* this) +{ + if (this->reuse_head > 0) + return this->reusable[--(this->reuse_head)]; + if (this->end == this->capacity) + { + this->capacity <<= 1; + this->values = realloc(this->values, this->capacity * sizeof(size_t)); + if (this->values == NULL) + return LINKED_LIST_UNUSED; + this->next = realloc(this->next, this->capacity * sizeof(ssize_t)); + if (this->next == NULL) + return LINKED_LIST_UNUSED; + this->previous = realloc(this->previous, this->capacity * sizeof(ssize_t)); + if (this->previous == NULL) + return LINKED_LIST_UNUSED; + this->reusable = realloc(this->reusable, this->capacity * sizeof(ssize_t)); + if (this->reusable == NULL) + return LINKED_LIST_UNUSED; + } + return (ssize_t)(this->end++); +} + + +/** + * Mark a position as unused + * + * @param this The list + * @param node The position + * @return The position + */ +static ssize_t linked_list_unuse(linked_list_t* this, ssize_t node) +{ + if (node < 0) + return node; + this->reusable[this->reuse_head++] = node; + this->next[node] = LINKED_LIST_UNUSED; + this->previous[node] = LINKED_LIST_UNUSED; + return node; +} + + +/** + * Insert a value after a specified, reference, node + * + * @param this The list + * @param value The value to insert + * @param predecessor The reference node + * @return The node that has been created and inserted, + * `LINKED_LIST_UNUSED` on error, `errno` will be set accordingly + */ +ssize_t linked_list_insert_after(linked_list_t* this, size_t value, ssize_t predecessor) +{ + ssize_t node = linked_list_get_next(this); + this->values[node] = value; + this->next[node] = this->next[predecessor]; + this->next[predecessor] = node; + this->previous[node] = predecessor; + this->previous[this->next[node]] = node; + return node; +} + + +/** + * Remove the node after a specified, reference, node + * + * @param this The list + * @param predecessor The reference node + * @return The node that has been removed + */ +ssize_t linked_list_remove_after(linked_list_t* this, ssize_t predecessor) +{ + ssize_t node = this->next[predecessor]; + this->next[predecessor] = this->next[node]; + this->previous[this->next[node]] = predecessor; + return linked_list_unuse(this, node); +} + + +/** + * Insert a value before a specified, reference, node + * + * @param this The list + * @param value The value to insert + * @param successor The reference node + * @return The node that has been created and inserted, + * `LINKED_LIST_UNUSED` on error, `errno` will be set accordingly + */ +ssize_t linked_list_insert_before(linked_list_t* this, size_t value, ssize_t successor) +{ + ssize_t node = linked_list_get_next(this); + this->values[node] = value; + this->previous[node] = this->next[successor]; + this->previous[successor] = node; + this->next[node] = successor; + this->next[this->previous[node]] = node; + return node; +} + + +/** + * Remove the node before a specified, reference, node + * + * @param this The list + * @param successor The reference node + * @return The node that has been removed + */ +ssize_t linked_list_remove_before(linked_list_t* this, ssize_t successor) +{ + ssize_t node = this->previous[successor]; + this->previous[successor] = this->previous[node]; + this->next[this->previous[node]] = successor; + return linked_list_unuse(this, node); +} + + +/** + * Remove the node from the list + * + * @param this The list + * @param node The node to remove + */ +void linked_list_remove(linked_list_t* this, ssize_t node) +{ + this->next[this->previous[node]] = this->next[node]; + this->previous[this->next[node]] = this->previous[node]; + linked_list_unuse(this, node); +} + -- cgit v1.2.3-70-g09d2