/* * Copyright (c) 2024 * Gregory Burd . All rights reserved. * * ISC License Permission to use, copy, modify, and/or distribute this software * for any purpose with or without fee is hereby granted, provided that the * above copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR * PERFORMANCE OF THIS SOFTWARE. * * I'd like to thank others for thoughtfully licensing their work, the * community of software engineers succeeds when we work together. * * Portions of this code are derived from other copyrighted works: * * - MIT License * - https://github.com/greensky00/skiplist * 2017-2024 Jung-Sang Ahn * - https://github.com/paulross/skiplist * Copyright (c) 2017-2023 Paul Ross * - https://github.com/JP-Ellis/rust-skiplist * Copyright (c) 2015 Joshua Ellis * - Public Domain * - https://gist.github.com/zhpengg/2873424 * Zhipeng Li */ #ifndef _SKIPLIST_H_ #define _SKIPLIST_H_ /* * This file defines a skiplist data structure. * * A skiplist is a way of storing sorted elements in such a way that they can be * accessed, inserted and removed, all in O(log(n)) on average. * * Conceptually, a skiplist is arranged as follows: * * ----------> [2] --------------------------------------------------> [9] ----------> * ----------> [2] ------------------------------------[7] ----------> [9] ----------> * ----------> [2] ----------> [4] ------------------> [7] ----------> [9] --> [10] -> * --> [1] --> [2] --> [3] --> [4] --> [5] --> [6] --> [7] --> [8] --> [9] --> [10] -> * * Each node contains at the very least a link to the next element in the list * (corresponding to the lowest level in the above diagram), but it can randomly * contain more links which skip further down the list (the towers in the above * diagram). This allows for the algorithm to move down the list faster than * having to visit every element. * * Conceptually, the skiplist can be thought of as a stack of linked lists. At * the very bottom is the full linked list with every element, and each layer * above corresponds to a linked list containing a random subset of the elements * from the layer immediately below it. The probability distribution that * determines this random subset can be customized, but typically a layer will * contain half the nodes from the layer below. * * This implementation maintains a doubly-linked list at the bottom layer to * support efficient iteration in either direction. There is also a guard * node at the tail rather than simply pointing to NULL. * * <-> [1] <-> [2] <-> [3] <-> [4] <-> [5] <-> [6] <-> [7] <-> * * Safety: * * The ordered skiplist relies on a well-behaved comparison * function. Specifically, given some ordering function f(a, b), it must satisfy * the following properties: * * 1) Be well defined: f(a, b) should always return the same value * 2) Be anti-symmetric: f(a, b) == Greater if and only if f(b, a) == Less, and * f(a, b) == Equal == f(b, a). * 3) Be transitive: If f(a, b) == Greater and f(b, c) == Greater then f(a, c) * == Greater. * * Failure to satisfy these properties can result in unexpected behavior at * best, and at worst will cause a segfault, null deref, or some other bad * behavior. * * References for this implementation include, but are not limited to: * * - Skip lists: a probabilistic alternative to balanced trees * @article{10.1145/78973.78977, * author = {Pugh, William}, * title = {Skip lists: a probabilistic alternative to balanced trees}, * year = {1990}, issue_date = {June 1990}, * publisher = {Association for Computing Machinery}, * address = {New York, NY, USA}, * volume = {33}, number = {6}, issn = {0001-0782}, * url = {https://doi.org/10.1145/78973.78977}, * doi = {10.1145/78973.78977}, * journal = {Commun. ACM}, month = {jun}, pages = {668-676}, numpages = {9}, * keywords = {trees, searching, data structures}, * download = {https://www.cl.cam.ac.uk/teaching/2005/Algorithms/skiplists.pdf} * } * * - Tutorial: The Ubiquitous Skiplist, its Variants, and Applications in Modern Big Data Systems * @article{Vadrevu2023TutorialTU, * title={Tutorial: The Ubiquitous Skiplist, its Variants, and Applications in Modern Big Data Systems}, * author={Venkata Sai Pavan Kumar Vadrevu and Lu Xing and Walid G. Aref}, * journal={ArXiv}, * year={2023}, * volume={abs/2304.09983}, * url={https://api.semanticscholar.org/CorpusID:258236678}, * download={https://arxiv.org/pdf/2304.09983.pdf} * } * * - The Splay-List: A Distribution-Adaptive Concurrent Skip-List * @misc{aksenov2020splaylist, * title={The Splay-List: A Distribution-Adaptive Concurrent Skip-List}, * author={Vitaly Aksenov and Dan Alistarh and Alexandra Drozdova and Amirkeivan Mohtashami}, * year={2020}, * eprint={2008.01009}, * archivePrefix={arXiv}, * primaryClass={cs.DC}, * download={https://arxiv.org/pdf/2008.01009.pdf} * } * * - JellyFish: A Fast Skip List with MVCC}, * @article{Yeon2020JellyFishAF, * title={JellyFish: A Fast Skip List with MVCC}, * author={Jeseong Yeon and Leeju Kim and Youil Han and Hyeon Gyu Lee and Eunji Lee and Bryan Suk Joon Kim}, * journal={Proceedings of the 21st International Middleware Conference}, * year={2020}, * url={https://api.semanticscholar.org/CorpusID:228086012} * } */ /* * Skip List declarations. */ #ifndef SKIPLIST_MAX_HEIGHT #define SKIPLIST_MAX_HEIGHT 1 #endif #if defined(SKIPLIST_DEBUG) #ifndef SKIP_DEBUGF #define SKIP_DEBUGF #if defined(DEBUG) && DEBUG > 0 #define __skip_debugf(...) \ do { \ fprintf(stderr, "%s:%d:%s(): ", __FILE__, __LINE__, __func__); \ fprintf(stderr, __VA_ARGS__); \ } while (0) #else #define __skip_debugf(fmt, args...) ((void)0) #endif #endif #endif /* * A Skip List contains elements, a portion of which is used to manage those * elements while the rest is defined by the use case for this declaration. The * house keeping portion is the SKIPLIST_ENTRY below. It maintains the array of * forward pointers to nodes and has a height (a zero-based count of levels, so * a height of `0` means one (1) level and a height of `4` means five (5) * levels). */ #define SKIPLIST_ENTRY(type) \ struct __skiplist_##decl_entry { \ struct type *sle_prev, **sle_next; \ size_t sle_height, sle_gen; \ } /* * Skip List node comparison function. This macro builds a function used when * comparing two nodes for equality. A portion of this function, `fn_blk`, is * the code you supply to compare two nodes as a block (starts with `{`, your * code, then `}`) that should compare the node referenced by `a` to the node * `b` as follows: * * When: * *a < *b : return -1 * *a == *b : return 0 * *a > *b : return 1 * * As stated earlier, the ordered skiplist relies on a well-behaved comparison * function. Specifically, given some ordering function f(a, b), it must satisfy * the following properties: * * 1) Be well defined: f(a, b) should always return the same value * 2) Be anti-symmetric: f(a, b) == Greater if and only if f(b, a) == Less, and * f(a, b) == Equal == f(b, a). * 3) Be transitive: If f(a, b) == Greater and f(b, c) == Greater then f(a, c) * == Greater. * * Failure to satisfy these properties can result in unexpected behavior at * best, and at worst will cause a segfault, null deref, or some other bad * behavior. * * Example for nodes with keys that are signed integeters (`int`): * { * (void)list; * (void)aux; * if (a->key < b->key) * return -1; * if (a->key > b->key) * return 1; * return 0; * } * * Note that the comparison function can also make use of the reference to the * list as well as a reference to a variable `aux` that you can point to * anything else required to perform your comparison. The auxiliary pointer * is unused for other purposes. You could even use it a pointer to a function * that chooses the proper comparison function for the two nodes in question. * * Example where the value of `decl` below is `ex`: * { * // Cast `aux` to a function that returns a function that properly compares * // `a` and `b`, for example if they were objects or different structs. * (skip_ex_cmp_t *(fn)(ex_node_t *, ex_node_t *)) = * (skip_ex_cmp_t *()(ex_node_t *, ex_node_t *))aux; * * // Use the `fn` pointed to by `aux` to get the comparison function. * skip_ex_cmp_t *cmp = fn(a, b); * * // Now call that function and return the proper result. * return cmp(list, a, b, aux); * } */ #define SKIP_COMPARATOR(list, decl, fn_blk) \ int __skip_cmp_##decl(struct list *head, struct decl *a, struct decl *b, void *aux) \ { \ if (a == b) \ return 0; \ if (a == (head)->slh_head || b == (head)->slh_tail) \ return -1; \ if (a == (head)->slh_tail || b == (head)->slh_head) \ return 1; \ fn_blk \ } #define SKIPLIST_FOREACH_H2T(decl, prefix, list, elm, iter) \ for (iter = 0, (elm) = prefix##skip_head_##decl(list); (elm) != NULL; iter++, (elm) = prefix##skip_next_node_##decl(list, elm)) /* Iterate from tail to head over the nodes. */ #define SKIPLIST_FOREACH_T2H(decl, prefix, list, elm, iter) \ for (iter = prefix##skip_size_##decl(list), (elm) = prefix##skip_tailf_##decl(list); (elm) != NULL; \ iter--, (elm) = prefix##skip_prev_node_##decl(list, elm)) #define __SKIP_ENTRIES_T2B(field, elm) for (size_t lvl = elm->field.sle_height; lvl != (size_t)-1; lvl--) #define __SKIP_ENTRIES_T2B_FROM(field, elm, off) for (size_t lvl = off; lvl != (size_t)-1; lvl--) #define __SKIP_IS_LAST_ENTRY_T2B() if (lvl == 0) #define __SKIP_ENTRIES_B2T(field, elm) for (size_t lvl = 0; lvl < elm->field.sle_height + 1; lvl++) #define __SKIP_ENTRIES_B2T_FROM(field, elm, off) for (size_t lvl = off; lvl < elm->field.sle_height + 1; lvl++) #define __SKIP_IS_LAST_ENTRY_B2T() if (lvl + 1 == elm->field.sle_height) /* * Skip List declarations and access methods. */ #define SKIPLIST_DECL(decl, prefix, field, free_node_blk, update_node_blk, archive_node_blk, sizeof_entry_blk) \ \ /* Skip List node type */ \ typedef struct decl##_node decl##_node_t; \ \ /* Skip List structure and type */ \ typedef struct decl { \ size_t slh_level, slh_length, slh_max, slh_gen; \ int (*slh_cmp)(struct decl *, decl##_node_t *, decl##_node_t *, void *); \ void *slh_aux; \ decl##_node_t *slh_head; \ decl##_node_t *slh_tail; \ struct { \ decl##_node_t *head; \ decl##_node_t *tail; \ size_t gen; \ } slh_snap; \ } decl##_t; \ \ /* Skip List comparison function type */ \ typedef int (*skip_##decl##_cmp_t)(decl##_t *, decl##_node_t *, decl##_node_t *, void *); \ \ /* Used when positioning a cursor within a Skip List. */ \ typedef enum { SKIP_EQ = 0, SKIP_LTE = -1, SKIP_LT = -2, SKIP_GTE = 1, SKIP_GT = 2 } skip_pos_##decl_t; \ \ /** \ * -- __skip_key_compare_ \ * \ * This function takes four arguments: \ * - a reference to the Skip List \ * - the two nodes to compare, `a` and `b` \ * - `aux` an additional auxiliary argument \ * and returns: \ * a < b : return -1 \ * a == b : return 0 \ * a > b : return 1 \ */ \ static int __skip_key_compare_##decl(decl##_t *slist, decl##_node_t *a, decl##_node_t *b, void *aux) \ { \ if (a == b) \ return 0; \ if (a == NULL) \ return -1; \ if (b == NULL) \ return 1; \ if (a == slist->slh_head || b == slist->slh_tail) \ return -1; \ if (a == slist->slh_tail || b == slist->slh_head) \ return 1; \ return slist->slh_cmp(slist, a, b, aux); \ } \ \ /** \ * -- __skip_toss_ \ * \ * A "coin toss" function that is critical to the proper operation of the \ * Skip List. For example, when `max = 6` this function returns 0 with \ * probability 0.5, 1 with 0.25, 2 with 0.125, etc. until 6 with 0.5^7. \ */ \ static int __skip_toss_##decl(size_t max) \ { \ size_t level = 0; \ double probability = 0.5; \ \ double random_value = (double)rand() / RAND_MAX; /* NOLINT(*-msc50-cpp) */ \ while (random_value < probability && level < max) { \ level++; \ probability *= 0.5; \ } \ return level; \ } \ \ /** \ * -- __skip_gen_ \ * \ * Returns the current generation for snapshot purposes. \ */ \ static inline size_t __skip_gen_##decl(decl##_t *slist) \ { \ return slist->slh_snap.gen; \ } \ \ /** \ * -- __skip_incr_gen_ \ * \ * Returns the current generation for snapshot purposes. \ */ \ static inline size_t __skip_incr_gen_##decl(decl##_t *slist) \ { \ return ++slist->slh_snap.gen; \ } \ \ /** \ * -- skip_alloc_node_ \ * \ * Allocates a new node on the heap and sets default values. \ */ \ int prefix##skip_alloc_node_##decl(decl##_t *slist, decl##_node_t **node) \ { \ decl##_node_t *n; \ /* Calculate the size of the struct sle within decl##_node_t, multiply \ by array size. (16/24 bytes on 32/64 bit systems) */ \ size_t sle_arr_sz = sizeof(struct __skiplist_##decl_entry) * slist->slh_max; \ n = (decl##_node_t *)calloc(1, sizeof(decl##_node_t) + sle_arr_sz); \ if (n == NULL) \ return ENOMEM; \ n->field.sle_height = 0; \ n->field.sle_next = (decl##_node_t **)((uintptr_t)n + sizeof(decl##_node_t)); \ *node = n; \ return 0; \ } \ \ /** \ * -- skip_init_ \ * \ * Initializes a Skip List to the deafault values, this must be called \ * before using the list. \ */ \ int prefix##skip_init_##decl(decl##_t *slist, int max, int (*cmp)(struct decl *, decl##_node_t *, decl##_node_t *, void *)) \ { \ int rc = 0; \ size_t i; \ \ slist->slh_length = 0; \ slist->slh_max = (size_t)(max < 0 ? -max : max); \ slist->slh_max = SKIPLIST_MAX_HEIGHT == 1 ? slist->slh_max : SKIPLIST_MAX_HEIGHT; \ if (SKIPLIST_MAX_HEIGHT > 1 && slist->slh_max > SKIPLIST_MAX_HEIGHT) \ return -1; \ slist->slh_cmp = cmp; \ rc = prefix##skip_alloc_node_##decl(slist, &slist->slh_head); \ if (rc) \ goto fail; \ rc = prefix##skip_alloc_node_##decl(slist, &slist->slh_tail); \ if (rc) \ goto fail; \ \ slist->slh_head->field.sle_height = 0; \ for (i = 0; i < slist->slh_max; i++) \ slist->slh_head->field.sle_next[i] = slist->slh_tail; \ slist->slh_head->field.sle_prev = NULL; \ \ slist->slh_tail->field.sle_height = slist->slh_max - 1; \ for (i = 0; i < slist->slh_max; i++) \ slist->slh_tail->field.sle_next[i] = NULL; \ slist->slh_tail->field.sle_prev = slist->slh_head; \ \ /* NOTE: Here's a testing aid, simply set `max` to a negative number to \ * seed the PRNG in a predictable way and have reproducible random numbers. \ */ \ if (max < 0) \ srand(-max); \ else \ srand(((unsigned int)time(NULL) ^ getpid())); \ fail:; \ return rc; \ } \ \ /** \ * -- skip_free_node_ \ * \ * Properly releases heap memory allocated for use as a node. \ * This function invokes the `free_node_blk` within which you \ * should release any heap objects or other resources held by \ * this node in the list. \ */ \ void prefix##skip_free_node_##decl(decl##_node_t *node) \ { \ free_node_blk; \ free(node); \ } \ \ /** \ * -- skip_size_ \ * \ * Returns the current size (length, count) of elements in the list. \ */ \ int prefix##skip_size_##decl(decl##_t *slist) \ { \ return slist->slh_length; \ } \ \ /** \ * -- skip_is_empty_ \ * \ * Returns non-zero when the list is empty. \ */ \ int prefix##skip_is_empty_##decl(decl##_t *slist) \ { \ return slist->slh_length == 0; \ } \ \ /** \ * -- skip_head_ \ * \ * Returns the node containing the first (smallest) element in the \ * list which can be used to traverse the list. \ */ \ decl##_node_t *prefix##skip_head_##decl(decl##_t *slist) \ { \ return slist->slh_head->field.sle_next[0] == slist->slh_tail ? NULL : slist->slh_head->field.sle_next[0]; \ } \ \ /** \ * -- skip_tail_ \ * \ * Returns the node containing the last (largest) element in the \ * list which can be used to traverse the list. \ */ \ decl##_node_t *prefix##skip_tail_##decl(decl##_t *slist) \ { \ return slist->slh_tail->field.sle_prev == slist->slh_head->field.sle_next[0] ? NULL : slist->slh_tail->field.sle_prev; \ } \ \ /** \ * -- skip_next_node_ \ * \ * A node reference can be thought of as a cursor. This moves the cursor \ * to the next node in the list or returns NULL if the next is the tail. \ */ \ decl##_node_t *prefix##skip_next_node_##decl(decl##_t *slist, decl##_node_t *n) \ { \ if (slist == NULL || n == NULL) \ return NULL; \ if (n->field.sle_next[0] == slist->slh_tail) \ return NULL; \ return n->field.sle_next[0]; \ } \ \ /** \ * -- skip_prev_node_ \ * \ * A node reference can be thought of as a cursor. This moves the cursor \ * to the previous node in the list or returns NULL if the previous node \ * is the head. \ */ \ decl##_node_t *prefix##skip_prev_node_##decl(decl##_t *slist, decl##_node_t *n) \ { \ if (slist == NULL || n == NULL) \ return NULL; \ if (n->field.sle_prev == slist->slh_head) \ return NULL; \ return n->field.sle_prev; \ } \ \ /** \ * -- skip_empty_ \ * \ * Release all nodes and their associated heap objects, but not the list \ * itself. The list is still valid, only empty. \ */ \ void prefix##skip_empty_##decl(decl##_t *slist) \ { \ decl##_node_t *node, *next; \ \ if (slist == NULL) \ return; \ if (prefix##skip_is_empty_##decl(slist)) \ return; \ node = prefix##skip_head_##decl(slist); \ do { \ next = prefix##skip_next_node_##decl(slist, node); \ prefix##skip_free_node_##decl(node); \ node = next; \ } while (node != NULL); \ \ while (node) { \ next = node->field.sle_next[0]; \ if (next->field.sle_prev) \ free_node_blk; \ free(node); \ } \ return; \ } \ \ /** \ * -- skip_to_array_ \ * \ * Returns a heap allocated array of nodes in the order they exist. \ * This isn't maintained by the list, if you add/remove nodes it is \ * no longer accurate. At [-1] is the length of the array. \ * NOTE: Caller must deallocate. \ */ \ decl##_node_t **prefix##skip_to_array_##decl(decl##_t *slist) \ { \ size_t nth, len = prefix##skip_size_##decl(slist); \ decl##_node_t *node, **nodes = NULL; \ nodes = (decl##_node_t **)calloc(sizeof(decl##_node_t *), len + 1); \ if (nodes != NULL) { \ nodes[0] = (decl##_node_t *)(uintptr_t)len; \ nodes++; \ SKIPLIST_FOREACH_H2T(decl, prefix, slist, node, nth) \ { \ nodes[nth] = node; \ } \ } \ return nodes; \ } \ \ /** \ * -- __skip_locate_ \ * \ * Locates a node that matches another node updating `path` and then \ * returning the length of that path + 1 to the node and the matching \ * node in path[0], or NULL at path[0] where there wasn't a match. \ * sizeof(path) should be `slist->slh_max + 1` \ */ \ static size_t __skip_locate_##decl(decl##_t *slist, decl##_node_t *n, decl##_node_t **path) \ { \ unsigned int i; \ size_t len = 0; \ decl##_node_t *elm = slist->slh_head; \ \ if (slist == NULL || n == NULL) \ return 0; \ \ /* Find the node that matches `node` or NULL. */ \ i = slist->slh_head->field.sle_height; \ do { \ while (elm != slist->slh_tail && elm->field.sle_next[i] && __skip_key_compare_##decl(slist, elm->field.sle_next[i], n, slist->slh_aux) < 0) \ elm = elm->field.sle_next[i]; \ path[i + 1] = elm; \ len++; \ } while (i--); \ elm = elm->field.sle_next[0]; \ if (__skip_key_compare_##decl(slist, elm, n, slist->slh_aux) == 0) { \ path[0] = elm; \ } \ return len; \ } \ \ /** \ * -- __skip_insert_ \ * \ * Inserts the node `new` into the list `slist`, when `flags` is non-zero \ * duplicate keys are allowed. Duplicates are grouped together by key but \ * are otherwise unordered. \ */ \ static int __skip_insert_##decl(decl##_t *slist, decl##_node_t *new, int flags) \ { \ int rc = 0; \ static decl##_node_t apath[SKIPLIST_MAX_HEIGHT + 1]; \ size_t i, len, loc = 0, cur_height, new_height; \ decl##_node_t *node, **path = (decl##_node_t **)&apath; \ \ if (slist == NULL || new == NULL) \ return ENOENT; \ \ /* Allocate a buffer, or use a static one. */ \ if (SKIPLIST_MAX_HEIGHT == 1) { \ path = malloc(sizeof(decl##_node_t *) * slist->slh_max + 1); \ if (path == NULL) \ return ENOMEM; \ } \ memset(path, 0, sizeof(decl##_node_t *) * slist->slh_max + 1); \ \ /* Find a `path` to `new` in the list and a match (`path[0]`) if it exists. */ \ len = __skip_locate_##decl(slist, new, path); \ node = path[0]; \ if (len > 0) { \ if ((node != NULL) && (flags == 0)) { \ /* Don't insert, duplicate if flag not set. */ \ return -1; \ } \ /* Coin toss to determine level of this new node [0, max) */ \ cur_height = slist->slh_head->field.sle_height; \ new_height = __skip_toss_##decl(slist->slh_max); \ new->field.sle_height = new_height; \ /* Trim the path to at most the new height for the new node. */ \ if (new_height > cur_height) { \ for (i = cur_height + 1; i <= new_height; i++) { \ path[i + 1] = slist->slh_tail; \ } \ } \ /* Ensure all next[] point to tail. */ \ __SKIP_ENTRIES_B2T(field, new) \ { \ new->field.sle_next[lvl] = slist->slh_tail; \ } \ /* Adjust all forward pointers for each element in the path. */ \ for (i = 0; i <= new_height; i++) { \ /* The tail's next[i] is always NULL, we don't want that in the \ next[i] for our new node. Also, don't set the tail's next[i] \ because it is always NULL. */ \ if (path[i + 1] != slist->slh_tail) { \ new->field.sle_next[i] = path[i + 1]->field.sle_next[i]; \ path[i + 1]->field.sle_next[i] = new; \ loc = path[i + 1] == slist->slh_head ? i : loc; \ } else { \ new->field.sle_next[i] = slist->slh_tail; \ } \ } \ /* Ensure all slh_head->next[] above loc point to tail. */ \ if (path[1] == slist->slh_head) { \ __SKIP_ENTRIES_B2T_FROM(field, slist->slh_head, loc + 1) \ { \ slist->slh_head->field.sle_next[lvl] = slist->slh_tail; \ } \ } \ /* Adujust the previous pointers in the nodes. */ \ new->field.sle_prev = path[1]; \ new->field.sle_next[0]->field.sle_prev = new; \ /* Account for insert at tail. */ \ if (new->field.sle_next[0] == slist->slh_tail) { \ slist->slh_tail->field.sle_prev = new; \ } \ /* Adjust the head/tail boundary node heights if necessary. */ \ if (new_height > cur_height) { \ slist->slh_head->field.sle_height = new_height; \ slist->slh_tail->field.sle_height = new_height; \ } \ /* Record this node's generation for snapshots. */ \ new->field.sle_gen = __skip_gen_##decl(slist); \ /* Increase our list length (aka. size, count, etc.) by one. */ \ slist->slh_length++; \ \ if (SKIPLIST_MAX_HEIGHT == 1) \ free(path); \ } \ return rc; \ } \ \ /** \ * -- skip_insert_ \ * \ * Insert into the list `slist` the node `n`. \ */ \ int prefix##skip_insert_##decl(decl##_t *slist, decl##_node_t *n) \ { \ return __skip_insert_##decl(slist, n, 0); \ } \ \ /** \ * -- skip_insert_dup_ \ * \ * Inserts into `slist` the node `n` even if that node's key already \ * exists in the list. \ */ \ int prefix##skip_insert_dup_##decl(decl##_t *slist, decl##_node_t *n) \ { \ return __skip_insert_##decl(slist, n, 1); \ } \ \ /** \ * -- skip_position_eq_ \ * \ * Find a node that matches the node `n`. This differs from the locate() \ * API in that it does not return the path to the node, only the match. \ * \ * NOTE: This differs from _locate() in that it avoids an alloc/free \ * for the path when SKIPLIST_MAX_HEIGHT == 1. \ */ \ decl##_node_t *prefix##skip_position_eq_##decl(decl##_t *slist, decl##_node_t *n) \ { \ unsigned int i; \ decl##_node_t *elm = slist->slh_head; \ \ if (slist == NULL || n == NULL) \ return NULL; \ \ i = slist->slh_head->field.sle_height; \ \ do { \ while (elm != slist->slh_tail && elm->field.sle_next[i] && __skip_key_compare_##decl(slist, elm->field.sle_next[i], n, slist->slh_aux) < 0) \ elm = elm->field.sle_next[i]; \ } while (i--); \ elm = elm->field.sle_next[0]; \ if (__skip_key_compare_##decl(slist, elm, n, slist->slh_aux) == 0) { \ return elm; \ } \ return NULL; \ } \ \ /** \ * -- skip_position_gte \ * \ * Position and return a cursor at the first node that is equal to \ * or greater than the provided node `n`, otherwise if the largest \ * key is less than the key in `n` return NULL. \ * \ * NOTE: This differs from _locate() in that it avoids an alloc/free \ * for the path when SKIPLIST_MAX_HEIGHT == 1. \ */ \ decl##_node_t *prefix##skip_position_gte_##decl(decl##_t *slist, decl##_node_t *query) \ { \ int cmp; \ unsigned int i; \ decl##_node_t *elm = slist->slh_head; \ \ if (slist == NULL || query == NULL) \ return NULL; \ \ i = slist->slh_head->field.sle_height; \ \ do { \ while (elm != slist->slh_tail && elm->field.sle_next[i] && __skip_key_compare_##decl(slist, elm->field.sle_next[i], query, slist->slh_aux) < 0) \ elm = elm->field.sle_next[i]; \ } while (i--); \ do { \ elm = elm->field.sle_next[0]; \ cmp = __skip_key_compare_##decl(slist, elm, query, slist->slh_aux); \ } while (cmp < 0); \ return elm; \ } \ \ /** \ * -- skip_position_gt_ \ * \ * Position and return a cursor at the first node that is greater than \ * the provided node `n`. If the largestkey is less than the key in `n` \ * return NULL. \ * \ * NOTE: This differs from _locate() in that it avoids an alloc/free \ * for the path when SKIPLIST_MAX_HEIGHT == 1. \ */ \ decl##_node_t *prefix##skip_position_gt_##decl(decl##_t *slist, decl##_node_t *query) \ { \ int cmp; \ unsigned int i; \ decl##_node_t *elm = slist->slh_head; \ \ if (slist == NULL || query == NULL) \ return NULL; \ \ i = slist->slh_head->field.sle_height; \ \ do { \ while (elm != slist->slh_tail && elm->field.sle_next[i] && __skip_key_compare_##decl(slist, elm->field.sle_next[i], query, slist->slh_aux) < 0) \ elm = elm->field.sle_next[i]; \ } while (i--); \ do { \ elm = elm->field.sle_next[0]; \ cmp = __skip_key_compare_##decl(slist, elm, query, slist->slh_aux); \ } while (cmp <= 0); \ return elm; \ } \ \ /** \ * -- skip_position_lte \ * \ * Position and return a cursor at the last node that is less than \ * or equal to node `n`. \ * Return NULL if nothing is less than or equal. \ * \ * NOTE: This differs from _locate() in that it avoids an alloc/free \ * for the path when SKIPLIST_MAX_HEIGHT == 1. \ */ \ decl##_node_t *prefix##skip_position_lte_##decl(decl##_t *slist, decl##_node_t *query) \ { \ int cmp; \ unsigned int i; \ decl##_node_t *elm = slist->slh_head; \ \ if (slist == NULL || query == NULL) \ return NULL; \ \ i = slist->slh_head->field.sle_height; \ \ do { \ while (elm != slist->slh_tail && elm->field.sle_next[i] && __skip_key_compare_##decl(slist, elm->field.sle_next[i], query, slist->slh_aux) < 0) \ elm = elm->field.sle_next[i]; \ } while (i--); \ elm = elm->field.sle_next[0]; \ if (__skip_key_compare_##decl(slist, elm, query, slist->slh_aux) == 0) { \ return elm; \ } else { \ do { \ elm = elm->field.sle_prev; \ cmp = __skip_key_compare_##decl(slist, elm, query, slist->slh_aux); \ } while (cmp >= 0); \ } \ return elm; \ } \ \ /** \ * -- skip_position_lt_ \ * \ * Position and return a cursor at the last node that is less than \ * to the node `n`. Return NULL if nothing is less than or equal. \ * \ * NOTE: This differs from _locate() in that it avoids an alloc/free \ * for the path when SKIPLIST_MAX_HEIGHT == 1. \ */ \ decl##_node_t *prefix##skip_position_lt_##decl(decl##_t *slist, decl##_node_t *query) \ { \ int cmp; \ unsigned int i; \ decl##_node_t *elm = slist->slh_head; \ \ if (slist == NULL || query == NULL) \ return NULL; \ \ i = slist->slh_head->field.sle_height; \ \ do { \ while (elm != slist->slh_tail && elm->field.sle_next[i] && __skip_key_compare_##decl(slist, elm->field.sle_next[i], query, slist->slh_aux) < 0) \ elm = elm->field.sle_next[i]; \ } while (i--); \ elm = elm->field.sle_next[0]; \ do { \ elm = elm->field.sle_prev; \ cmp = __skip_key_compare_##decl(slist, elm, query, slist->slh_aux); \ } while (cmp >= 0); \ return elm; \ } \ \ /** \ * -- skip_position_ \ * \ * Position a cursor relative to `n`. \ * \ * NOTE: This differs from _locate() in that it avoids an alloc/free \ * for the path when SKIPLIST_MAX_HEIGHT == 1. \ */ \ decl##_node_t *prefix##skip_position_##decl(decl##_t *slist, skip_pos_##decl_t op, decl##_node_t *query) \ { \ decl##_node_t *node; \ \ switch (op) { \ case (SKIP_LT): \ node = prefix##skip_position_lt_##decl(slist, query); \ break; \ case (SKIP_LTE): \ node = prefix##skip_position_lte_##decl(slist, query); \ break; \ case (SKIP_GTE): \ node = prefix##skip_position_gte_##decl(slist, query); \ break; \ case (SKIP_GT): \ node = prefix##skip_position_gt_##decl(slist, query); \ break; \ default: \ case (SKIP_EQ): \ node = prefix##skip_position_eq_##decl(slist, query); \ break; \ } \ return node; \ } \ \ /** \ * -- skip_update_ \ * \ * Locates a node in the list that equals the `new` node and then \ * uses the `update_node_blk` to update the contents. \ * \ * WARNING: Do not update the portion of the node used for ordering \ * (e.g. `key`) unless you really know what you're doing. \ */ \ int prefix##skip_update_##decl(decl##_t *slist, decl##_node_t *new) \ { \ static decl##_node_t apath[SKIPLIST_MAX_HEIGHT + 1]; \ int rc = 0; \ decl##_node_t *node, **path = (decl##_node_t **)&apath; \ \ if (slist == NULL) \ return -1; \ \ /* Allocate a buffer, or use a static one. */ \ if (SKIPLIST_MAX_HEIGHT == 1) { \ path = malloc(sizeof(decl##_node_t *) * slist->slh_max + 1); \ if (path == NULL) \ return ENOMEM; \ } \ memset(path, 0, sizeof(decl##_node_t *) * slist->slh_max + 1); \ \ __skip_locate_##decl(slist, new, path); \ node = path[0]; \ \ if (SKIPLIST_MAX_HEIGHT == 1) \ free(path); \ \ if (node) { \ decl##_node_t *src = node, *dest = new; \ update_node_blk; \ node->field.sle_gen = __skip_gen_##decl(slist); \ return rc; \ } \ return -1; \ } \ \ /** \ * -- skip_remove_node_ \ * \ * Removes the node `n` from the `slist` if present. \ */ \ int prefix##skip_remove_node_##decl(decl##_t *slist, decl##_node_t *n) \ { \ size_t i, len, height; \ static decl##_node_t apath[SKIPLIST_MAX_HEIGHT + 1]; \ decl##_node_t *node, **path = (decl##_node_t **)&apath; \ \ if (slist == NULL || n == NULL) \ return -1; \ if (slist->slh_length == 0) \ return 0; \ \ /* Allocate a buffer */ \ if (SKIPLIST_MAX_HEIGHT == 1) { \ path = malloc(sizeof(decl##_node_t *) * slist->slh_max + 1); \ if (path == NULL) \ return ENOMEM; \ } \ memset(path, 0, sizeof(decl##_node_t *) * slist->slh_max + 1); \ \ /* Attempt to locate the node in the list. */ \ len = __skip_locate_##decl(slist, n, path); \ node = path[0]; \ if (node) { \ /* We found it, set the next->prev to the node->prev keeping in mind \ that the next node might be the tail). */ \ node->field.sle_next[0]->field.sle_prev = node->field.sle_prev; \ /* Walk the path, stop when the next node is not the one we're \ removing. At each step along our walk... */ \ for (i = 0; i < len; i++) { \ if (path[i + 1]->field.sle_next[i] != node) \ break; \ /* ... adjust the next pointer at that level. */ \ path[i + 1]->field.sle_next[i] = node->field.sle_next[i]; \ /* Adjust the height so we're only pointing at the tail once at \ the top so we don't waste steps later when searching. */ \ if (path[i + 1]->field.sle_next[i] == slist->slh_tail) { \ height = path[i + 1]->field.sle_height; \ path[i + 1]->field.sle_height = height - 1; \ } \ } \ /* Account for delete at tail. */ \ if (node->field.sle_next[0] == slist->slh_tail) { \ slist->slh_tail->field.sle_prev = n->field.sle_prev; \ } \ \ if (SKIPLIST_MAX_HEIGHT == 1) \ free(path); \ \ free_node_blk; \ \ /* Reduce the height of the header. */ \ i = 0; \ while (slist->slh_head->field.sle_next[i] != slist->slh_tail && i < slist->slh_head->field.sle_height) \ i++; \ slist->slh_head->field.sle_height = i; \ slist->slh_tail->field.sle_height = i; \ \ slist->slh_length--; \ } \ return 0; \ } \ \ /** \ * -- skip_destroy_ \ * \ * Release all nodes and their associated heap objects. The list reference \ * is no longer valid after this call. To make it valid again call _init(). \ */ \ void prefix##skip_destroy_##decl(decl##_t *slist) \ { \ if (slist == NULL) \ return; \ \ prefix##skip_empty_##decl(slist); \ \ free(slist->slh_head); \ free(slist->slh_tail); \ return; \ } \ \ /** \ * -- skip_snap_head_ \ * \ * Returns the node containing the first (smallest) element in the \ * snapshot which can be used to traverse the list. \ */ \ decl##_node_t *prefix##skip_snap_head_##decl(decl##_t *slist) \ { \ return slist->slh_snap.head->field.sle_next[0] == slist->slh_snap.tail ? NULL : slist->slh_snap.head->field.sle_next[0]; \ } \ \ /** \ * -- skip_snap_tail_ \ * \ * Returns the node containing the last (largest) element in the \ * snapshot which can be used to traverse the list. \ */ \ decl##_node_t *prefix##skip_snap_tail_##decl(decl##_t *slist) \ { \ return slist->slh_snap.tail->field.sle_prev == slist->slh_snap.head->field.sle_next[0] ? NULL : slist->slh_snap.tail->field.sle_prev; \ } \ \ /** \ * -- skip_release_snapshot_ \ * \ * ALGORITHM: \ * A snapshot starts with a copy of the head and the tail of the list. \ * Those can be free'd here as our last step. We record a generation, which \ * is a monatomically growing unsigned int, at the time of the snapshot, \ * nodes inserted or mutated have there generation updated. To find the \ * nodes in the list that are only referenced by the snapshot we can perform \ * a "mergesort" like traversal of both the snapshot and the live list. For \ * each node, if the keys match and the nodes are not equal (same address in \ * memory) and we've reached a node greater than the snap node then we can \ * free the node in the snap. Duplicates complicate this a bit. \ */ \ void prefix##skip_release_snapshot_##decl(decl##_t *slist) \ { \ int cmp; \ size_t nth, cnt = 0; \ decl##_node_t *sn, *ln, *node, *next; \ \ if (slist == NULL) \ return; \ \ sn = prefix##skip_snap_head_##decl(slist); \ SKIPLIST_FOREACH_H2T(decl, prefix, slist, ln, nth) \ { \ goto top_of_loop; \ sn_forward_only:; \ sn = sn->field.sle_next[0]; \ if (sn == slist->slh_snap.tail) \ break; \ top_of_loop:; \ /* When a node is referenced by both, keep going. */ \ if (ln == sn) \ goto both_sn_and_ln_forward; \ \ cmp = slist->slh_cmp(slist, sn, ln, slist->slh_aux); \ /* When the `sn` > the `ln`, move forward `ln` only. */ \ if (cmp > 0) \ goto ln_forward_only; \ /* When the `sn` < the `ln`, move both forward. */ \ if (cmp < 0) { \ sn = sn->field.sle_next[0]; \ if (sn == slist->slh_snap.tail) \ break; \ goto sn_forward_only; \ } \ /* When nodes match but have different addresses... */ \ if (cmp == 0) { \ /* ... we could have: \ a) a duplicate, or \ b) a copied a node, but not it's value, because it was \ adjacent to some mutated node (it was in the `path[]` \ during an insert, update, or delete), or \ c) ...? \ */ \ cnt++; \ } \ /* ln forward only */ \ goto ln_forward_only; \ \ ln_forward_only:; \ continue; \ both_sn_and_ln_forward:; \ sn = sn->field.sle_next[0]; \ if (sn == slist->slh_snap.tail) \ break; \ } \ /* If `sn` isn't at tail then there are a few more nodes to release. */ \ while (sn != slist->slh_snap.tail) { \ node = sn; \ free_node_blk; \ next = sn->field.sle_next[0]; \ free(sn); \ sn = next; \ } \ } \ \ /** \ * -- __skip_preserve_node_ \ * \ * Preserve given node in the slh_pres list. \ */ \ static int __skip_preserve_node_##decl(decl##_t *slist, const decl##_node_t *src, decl##_node_t **preserved) \ { \ int rc = 0; \ decl##_node_t *dest; \ \ if (slist == NULL || src == NULL) \ return 0; \ \ /* (a) alloc */ \ rc = prefix##skip_alloc_node_##decl(slist, &dest); \ if (rc) \ return rc; \ \ /* (b) shallow copy */ \ memcpy(dest, src, sizeof(decl##_node_t)); \ \ if (!(src == slist->slh_head || src == slist->slh_tail)) { \ /* (d) deep copy */ \ archive_node_blk; \ if (rc) { \ prefix##skip_free_node_##decl(dest); \ return rc; \ } \ } \ \ *preserved = dest; \ \ return rc; \ } \ \ /** \ * -- skip_restore_snapshot_ TODO/WIP \ * \ * Restores the Skiplist to the snapshot. \ */ \ decl##_t *prefix##skip_restore_snapshot_##decl(decl##_t *slist) \ { \ ((void)slist); \ return NULL; \ } \ \ /** \ * -- skip_snapshot_ \ * \ * A snapshot is a read-only view of a Skip List at a point in time. Once \ * taken, a snapshot must be restored or released. Any number of snapshots \ * can be created. \ */ \ size_t prefix##skip_snapshot_##decl(decl##_t *slist) \ { \ int rc; \ decl##_node_t *head, *tail; \ \ if (slist == NULL) \ return 0; \ /* (a) preserve the head node */ \ rc = __skip_preserve_node_##decl(slist, slist->slh_head, &head); \ if (rc > 0) \ return rc; \ /* (b) preserve the tail node */ \ rc = __skip_preserve_node_##decl(slist, slist->slh_tail, &tail); \ if (rc > 0) { \ prefix##skip_free_node_##decl(head); \ return rc; \ } \ /* (c) update any references in the new head's next[] array to point to \ the new tail; update the prev field in the new tail to the new head \ for similar reasons. */ \ __SKIP_ENTRIES_B2T(field, head) \ { \ if (head->field.sle_next[lvl] == slist->slh_tail) \ head->field.sle_next[lvl] = tail; \ } \ if (tail->field.sle_prev == slist->slh_head) \ tail->field.sle_prev = head; \ /* (d) release previous snapshot, assign the new one */ \ if (slist->slh_snap.head != NULL) \ prefix##skip_release_snapshot_##decl(slist); \ slist->slh_snap.head = head; \ slist->slh_snap.tail = tail; \ slist->slh_snap.gen = __skip_incr_gen_##decl(slist); \ return slist->slh_gen; \ } #define SKIPLIST_INTEGRITY_CHECK(decl, prefix, field) \ /** \ * -- __skip_integrity_failure_ \ */ \ static void __attribute__((format(printf, 1, 2))) __skip_integrity_failure_##decl(const char *fmt, ...) \ { \ va_list args; \ __skip_debugf(fmt, args); \ } \ \ /** \ * -- __skip_integrity_check_ \ */ \ static int __skip_integrity_check_##decl(decl##_t *slist, int flags) \ { \ size_t n = 0; \ unsigned long nth, n_err = 0; \ decl##_node_t *node, *prev, *next; \ struct __skiplist_##decl_entry *this; \ \ if (slist == NULL) { \ __skip_integrity_failure_##decl("slist was NULL, nothing to check\n"); \ n_err++; \ return n_err; \ } \ \ /* Check the Skiplist header (slh) */ \ \ if (slist->slh_head == NULL) { \ __skip_integrity_failure_##decl("skiplist slh_head is NULL\n"); \ n_err++; \ return n_err; \ } \ \ if (slist->slh_tail == NULL) { \ __skip_integrity_failure_##decl("skiplist slh_tail is NULL\n"); \ n_err++; \ return n_err; \ } \ \ if (slist->slh_cmp == NULL) { \ __skip_integrity_failure_##decl("skiplist comparison function (cmp) is NULL\n"); \ n_err++; \ return n_err; \ } \ \ if (slist->slh_max < 1) { \ __skip_integrity_failure_##decl("skiplist max level must be 1 at minimum\n"); \ n_err++; \ if (flags) \ return n_err; \ } \ \ if (slist->slh_level >= slist->slh_max) { \ /* level is 0-based, max of 12 means level cannot be > 11 */ \ __skip_integrity_failure_##decl("skiplist level %lu in header was >= max %lu\n", slist->slh_level, slist->slh_max); \ n_err++; \ if (flags) \ return n_err; \ } \ \ if (SKIPLIST_MAX_HEIGHT < 1) { \ __skip_integrity_failure_##decl("SKIPLIST_MAX_HEIGHT cannot be less than 1\n"); \ n_err++; \ if (flags) \ return n_err; \ } \ \ if (SKIPLIST_MAX_HEIGHT > 1 && slist->slh_max > SKIPLIST_MAX_HEIGHT) { \ __skip_integrity_failure_##decl("slist->slh_max %lu cannot be greater than SKIPLIST_MAX_HEIGHT %lu\n", slist->slh_max, \ (size_t)SKIPLIST_MAX_HEIGHT); \ n_err++; \ if (flags) \ return n_err; \ } \ \ node = slist->slh_head; \ __SKIP_ENTRIES_B2T(field, node) \ { \ if (node->field.sle_next[lvl] == NULL) { \ __skip_integrity_failure_##decl("the head's %lu next node should not be NULL\n", lvl); \ n_err++; \ if (flags) \ return n_err; \ } \ n = lvl; \ if (node->field.sle_next[lvl] == slist->slh_tail) \ break; \ } \ n++; \ __SKIP_ENTRIES_B2T_FROM(field, node, n) \ { \ if (node->field.sle_next[lvl] == NULL) { \ __skip_integrity_failure_##decl("the head's %lu next node should not be NULL\n", lvl); \ n_err++; \ if (flags) \ return n_err; \ } \ if (node->field.sle_next[lvl] != slist->slh_tail) { \ __skip_integrity_failure_##decl("after internal nodes, the head's %lu next node should always be the tail\n", lvl); \ n_err++; \ if (flags) \ return n_err; \ } \ } \ \ if (slist->slh_length > 0 && slist->slh_tail->field.sle_prev == slist->slh_head) { \ __skip_integrity_failure_##decl("slist->slh_length is 0, but tail->prev == head, not an internal node\n"); \ n_err++; \ if (flags) \ return n_err; \ } \ \ /* Validate the head node */ \ \ /* Validate the tail node */ \ \ /* Validate each node */ \ SKIPLIST_FOREACH_H2T(decl, prefix, slist, node, nth) \ { \ this = &node->field; \ \ if (this->sle_height >= slist->slh_max) { \ __skip_integrity_failure_##decl("the %luth node's [%p] height %lu is >= max %lu\n", nth, (void *)node, this->sle_height, slist->slh_max); \ n_err++; \ if (flags) \ return n_err; \ } \ \ if (this->sle_next == NULL) { \ __skip_integrity_failure_##decl("the %luth node's [%p] next field should never NULL\n", nth, (void *)node); \ n_err++; \ if (flags) \ return n_err; \ } \ \ if (this->sle_prev == NULL) { \ __skip_integrity_failure_##decl("the %luth node [%p] prev field should never NULL\n", nth, (void *)node); \ n_err++; \ if (flags) \ return n_err; \ } \ \ __SKIP_ENTRIES_B2T(field, node) \ { \ if (this->sle_next[lvl] == NULL) { \ __skip_integrity_failure_##decl("the %luth node's next[%lu] should not be NULL\n", nth, lvl); \ n_err++; \ if (flags) \ return n_err; \ } \ n = lvl; \ if (this->sle_next[lvl] == slist->slh_tail) \ break; \ } \ n++; \ __SKIP_ENTRIES_B2T_FROM(field, node, n) \ { \ if (this->sle_next[lvl] == NULL) { \ __skip_integrity_failure_##decl("after the %lunth the %luth node's next[%lu] should not be NULL\n", n, nth, lvl); \ n_err++; \ if (flags) \ return n_err; \ } else if (this->sle_next[lvl] != slist->slh_tail) { \ __skip_integrity_failure_##decl("after the %lunth the %luth node's next[%lu] should point to the tail\n", n, nth, lvl); \ n_err++; \ if (flags) \ return n_err; \ } \ } \ \ decl##_node_t *a = (decl##_node_t *)(uintptr_t)this->sle_next; \ decl##_node_t *b = (decl##_node_t *)(intptr_t)((uintptr_t)node + sizeof(decl##_node_t)); \ if (a != b) { \ __skip_integrity_failure_##decl("the %luth node's [%p] next field isn't at the proper offset relative to the node\n", nth, (void *)node); \ n_err++; \ if (flags) \ return n_err; \ } \ \ next = this->sle_next[0]; \ prev = this->sle_prev; \ if (__skip_key_compare_##decl(slist, node, node, slist->slh_aux) != 0) { \ __skip_integrity_failure_##decl("the %luth node [%p] is not equal to itself\n", nth, (void *)node); \ n_err++; \ if (flags) \ return n_err; \ } \ \ if (__skip_key_compare_##decl(slist, node, prev, slist->slh_aux) < 0) { \ __skip_integrity_failure_##decl("the %luth node [%p] is not greater than the prev node [%p]\n", nth, (void *)node, (void *)prev); \ n_err++; \ if (flags) \ return n_err; \ } \ \ if (__skip_key_compare_##decl(slist, node, next, slist->slh_aux) > 0) { \ __skip_integrity_failure_##decl("the %luth node [%p] is not less than the next node [%p]\n", nth, (void *)node, (void *)next); \ n_err++; \ if (flags) \ return n_err; \ } \ \ if (__skip_key_compare_##decl(slist, prev, node, slist->slh_aux) > 0) { \ __skip_integrity_failure_##decl("the prev node [%p] is not less than the %luth node [%p]\n", (void *)prev, nth, (void *)node); \ n_err++; \ if (flags) \ return n_err; \ } \ \ if (__skip_key_compare_##decl(slist, next, node, slist->slh_aux) < 0) { \ __skip_integrity_failure_##decl("the next node [%p] is not greater than the %luth node [%p]\n", (void *)next, nth, (void *)node); \ n_err++; \ if (flags) \ return n_err; \ } \ } \ \ if (slist->slh_length != nth) { \ __skip_integrity_failure_slex("slist->slh_length (%lu) doesn't match the count (%lu) of nodes between the head and tail\n", slist->slh_length, \ nth); \ n_err++; \ if (flags) \ return n_err; \ } \ \ return 0; \ } #define SKIPLIST_KV_ACCESS(decl, prefix, key, ktype, value, vtype, qblk, rblk) \ /** \ * skip_get_ -- \ * \ * Get the value for the given key. In the presence of duplicate keys this \ * returns the value from the first duplicate. \ */ \ vtype prefix##skip_get_##decl(decl##_t *slist, ktype key) \ { \ decl##_node_t *node, query; \ \ qblk; \ node = prefix##skip_position_eq_##decl(slist, &query); \ if (node) { \ rblk; \ } \ return (vtype)0; \ } \ \ /** \ * skip_contains_ -- \ * \ * Returns true if there is at least one match for the `key` in the list. \ */ \ int prefix##skip_contains_##decl(decl##_t *slist, ktype key) \ { \ decl##_node_t *node, query; \ \ qblk; \ node = prefix##skip_position_eq_##decl(slist, &query); \ if (node) \ return 1; \ return 0; \ } \ \ /** \ * skip_pos_ -- \ * \ * Position a "cursor" (get a "node") from the list that satisfies the \ * condition (`op`) or return NULL if the condition cannot be satisfied. \ * The condition is a skip_pos_##decl_t enum type: \ * \ * SKIP_GT -> greater than \ * SKIP_GTE -> greater than or equal to \ * SKIP_EQ -> equal to \ * SKIP_LTE -> less than or equal to \ * SKIP_LT -> less than \ * \ */ \ decl##_node_t *prefix##skip_pos_##decl(decl##_t *slist, skip_pos_##decl_t op, ktype key) \ { \ decl##_node_t *node, query; \ \ qblk; \ node = prefix##skip_position_##decl(slist, op, &query); \ if (node != slist->slh_head && node != slist->slh_tail) \ return node; \ return NULL; \ } \ \ /** \ * skip_put_ -- \ * \ * Inserts `key` into the list within a node that contains `value`. \ */ \ int prefix##skip_put_##decl(decl##_t *slist, ktype key, vtype value) \ { \ int rc; \ decl##_node_t *node; \ rc = prefix##skip_alloc_node_##decl(slist, &node); \ if (rc) \ return rc; \ node->key = key; \ node->value = value; \ rc = prefix##skip_insert_##decl(slist, node); \ if (rc) \ prefix##skip_free_node_##decl(node); \ return rc; \ } \ \ /** \ * skip_dup_ -- \ * \ * Inserts `key` into the list allowing for duplicates within a node that \ * contains `value`. \ */ \ int prefix##skip_dup_##decl(decl##_t *slist, ktype key, vtype value) \ { \ int rc; \ decl##_node_t *node; \ rc = prefix##skip_alloc_node_##decl(slist, &node); \ if (rc) \ return rc; \ node->key = key; \ node->value = value; \ rc = prefix##skip_insert_dup_##decl(slist, node); \ if (rc) \ prefix##skip_free_node_##decl(node); \ return rc; \ } \ \ /** \ * skip_set_ -- \ * \ * Updates in-place the node to contain the new `value`. In the presence of \ * duplicate keys in the list, the first key's value will be updated. \ */ \ int prefix##skip_set_##decl(decl##_t *slist, ktype key, vtype value) \ { \ decl##_node_t node; \ node.key = key; \ node.value = value; \ return prefix##skip_update_##decl(slist, &node); \ } \ \ /** \ * skip_del_ -- \ * \ * Removes the node from the list with a matching `key`. In the presence of \ * duplicate keys in the list, this will remove the first duplicate. \ */ \ int prefix##skip_del_##decl(decl##_t *slist, ktype key) \ { \ decl##_node_t node; \ node.key = key; \ return prefix##skip_remove_node_##decl(slist, &node); \ } #define SKIPLIST_DECL_DOT(decl, prefix, field) \ \ /* A type for a function that writes into a char[2048] buffer \ * a description of the value within the node. */ \ typedef void (*skip_sprintf_node_##decl##_t)(decl##_node_t *, char *); \ \ /* -- __skip_dot_node_ \ * Writes out a fragment of a DOT file representing a node. \ */ \ static size_t __skip_dot_width_##decl(decl##_t *slist, decl##_node_t *from, decl##_node_t *to) \ { \ size_t w = 1; \ decl##_node_t *n = to; \ \ if (from == NULL || to == NULL) \ return 0; \ \ while (n->field.sle_prev != from) { \ w++; \ n = prefix##skip_prev_node_##decl(slist, n); \ } \ \ return w; \ } \ \ static inline void __skip_dot_write_node_##decl(FILE *os, size_t nsg, decl##_node_t *node) \ { \ if (node) \ fprintf(os, "\"node%lu %p\"", nsg, (void *)node); \ else \ fprintf(os, "\"node%lu NULL\"", nsg); \ } \ \ /* -- __skip_dot_node_ \ * Writes out a fragment of a DOT file representing a node. \ */ \ static void __skip_dot_node_##decl(FILE *os, decl##_t *slist, decl##_node_t *node, size_t nsg, skip_sprintf_node_##decl##_t fn) \ { \ char buf[2048]; \ size_t width; \ decl##_node_t *next; \ \ __skip_dot_write_node_##decl(os, nsg, node); \ fprintf(os, " [label = \""); \ fflush(os); \ __SKIP_ENTRIES_T2B(field, node) \ { \ next = (node->field.sle_next[lvl] == slist->slh_tail) ? NULL : node->field.sle_next[lvl]; \ width = __skip_dot_width_##decl(slist, node, next ? next : slist->slh_tail); \ fprintf(os, " { %lu | ", lvl, width, lvl); \ if (next) \ fprintf(os, "%p } |", (void *)next); \ else \ fprintf(os, "0x0 } |"); \ fflush(os); \ } \ if (fn) { \ fn(node, buf); \ fprintf(os, " \u219F %lu \u226B %s \"\n", node->field.sle_height + 1, buf); \ } else { \ fprintf(os, " \u219F %lu \"\n", node->field.sle_height); \ } \ fprintf(os, "shape = \"record\"\n"); \ fprintf(os, "];\n"); \ fflush(os); \ \ /* Now edges */ \ __SKIP_ENTRIES_B2T(field, node) \ { \ next = (node->field.sle_next[lvl] == slist->slh_tail) ? NULL : node->field.sle_next[lvl]; \ __skip_dot_write_node_##decl(os, nsg, node); \ fprintf(os, ":f%lu -> ", lvl); \ __skip_dot_write_node_##decl(os, nsg, next); \ fprintf(os, ":w%lu [];\n", lvl); \ fflush(os); \ } \ } \ \ /* -- _skip_dot_finish_ \ * Finalize the DOT file of the internal representation. \ */ \ void prefix##skip_dot_end_##decl(FILE *os, size_t nsg) \ { \ size_t i; \ if (nsg > 0) { \ /* Link the nodes together with an invisible node. \ * node0 [shape=record, label = " | | | | \ * | | | | | ", style=invis, width=0.01]; \ */ \ fprintf(os, "node0 [shape=record, label = \""); \ for (i = 0; i < nsg; ++i) { \ fprintf(os, " | ", i); \ } \ fprintf(os, "\", style=invis, width=0.01];\n"); \ \ /* Now connect nodes with invisible edges \ * \ * node0:f0 -> HeadNode [style=invis]; \ * node0:f1 -> HeadNode1 [style=invis]; \ */ \ for (i = 0; i < nsg; ++i) { \ fprintf(os, "node0:f%lu -> HeadNode%lu [style=invis];\n", i, i); \ } \ nsg = 0; \ } \ fprintf(os, "}\n"); \ } \ \ /* -- skip_dot_ \ * Create a DOT file of the internal representation of the \ * Skip List on the provided file descriptor (default: STDOUT). \ * \ * To view the output: \ * $ dot -Tps filename.dot -o outfile.ps \ * You can change the output format by varying the value after -T and \ * choosing an appropriate filename extension after -o. \ * See: https://graphviz.org/docs/outputs/ for the format options. \ * \ * https://en.wikipedia.org/wiki/DOT_(graph_description_language) \ */ \ int prefix##skip_dot_##decl(FILE *os, decl##_t *slist, size_t nsg, char *msg, skip_sprintf_node_##decl##_t fn) \ { \ int letitgo = 0; \ size_t width, i; \ decl##_node_t *node, *next; \ \ if (slist == NULL || fn == NULL) \ return nsg; \ if (__skip_integrity_check_##decl(slist, 1) != 0) { \ perror("Skiplist failed integrity checks, impossible to diagram."); \ return -1; \ } \ if (nsg == 0) { \ fprintf(os, "digraph Skiplist {\n"); \ fprintf(os, "label = \"Skiplist.\"\n"); \ fprintf(os, "graph [rankdir = \"LR\"];\n"); \ fprintf(os, "node [fontsize = \"12\" shape = \"ellipse\"];\n"); \ fprintf(os, "edge [];\n\n"); \ } \ fprintf(os, "subgraph cluster%lu {\n", nsg); \ fprintf(os, "style=dashed\n"); \ fprintf(os, "label=\"Skiplist iteration %lu", nsg); \ if (msg) \ fprintf(os, ", %s", msg); \ fprintf(os, "\"\n\n"); \ fprintf(os, "\"HeadNode%lu\" [\n", nsg); \ fprintf(os, "label = \""); \ \ if (slist->slh_head->field.sle_height || slist->slh_head->field.sle_next[0] != slist->slh_tail) \ letitgo = 1; \ \ /* Write out the fields */ \ node = slist->slh_head; \ if (letitgo) { \ __SKIP_ENTRIES_T2B(field, node) \ { \ next = (node->field.sle_next[lvl] == slist->slh_tail) ? NULL : node->field.sle_next[lvl]; \ width = __skip_dot_width_##decl(slist, node, next ? next : slist->slh_tail); \ fprintf(os, "{ %lu | ", width, lvl); \ if (next) \ fprintf(os, "%p }", (void *)next); \ else \ fprintf(os, "0x0 }"); \ __SKIP_IS_LAST_ENTRY_T2B() continue; \ fprintf(os, " | "); \ } \ } else { \ fprintf(os, "Empty HeadNode"); \ } \ fprintf(os, "\"\n"); \ fprintf(os, "shape = \"record\"\n"); \ fprintf(os, "];\n"); \ fflush(os); \ \ /* Edges for head node */ \ node = slist->slh_head; \ if (letitgo) { \ node = slist->slh_head; \ __SKIP_ENTRIES_B2T(field, node) \ { \ next = (node->field.sle_next[lvl] == slist->slh_tail) ? NULL : node->field.sle_next[lvl]; \ fprintf(os, "\"HeadNode%lu\":f%lu -> ", nsg, lvl); \ __skip_dot_write_node_##decl(os, nsg, next); \ fprintf(os, ":w%lu [];\n", lvl); \ } \ fprintf(os, "\n"); \ } \ fflush(os); \ \ /* Now all nodes via level 0, if non-empty */ \ node = slist->slh_head; \ if (letitgo) { \ SKIPLIST_FOREACH_H2T(decl, prefix, slist, next, i) \ { \ ((void)i); \ __skip_dot_node_##decl(os, slist, next, nsg, fn); \ fflush(os); \ } \ fprintf(os, "\n"); \ } \ fflush(os); \ \ /* The tail, sentinal node */ \ if (letitgo) { \ __skip_dot_write_node_##decl(os, nsg, NULL); \ fprintf(os, " [label = \""); \ node = slist->slh_tail; \ size_t th = slist->slh_head->field.sle_height; \ for (size_t lvl = th; lvl != (size_t)-1; lvl--) { \ next = (node->field.sle_next[lvl] == slist->slh_tail) ? NULL : node->field.sle_next[lvl]; \ fprintf(os, " 0x0", lvl); \ __SKIP_IS_LAST_ENTRY_T2B() continue; \ fprintf(os, " | "); \ } \ fprintf(os, "\" shape = \"record\"];\n"); \ } \ \ /* End: "subgraph cluster0 {" */ \ fprintf(os, "}\n\n"); \ nsg += 1; \ fflush(os); \ \ return nsg; \ } #endif /* _SKIPLIST_H_ */