/* * 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 copyrighted work: * * - MIT LICENSE * - https://github.com/greensky00/skiplist * 2017-2024 Jung-Sang Ahn * - https://github.com/paulross/skiplist * Copyright (c) 2017-2023 Paul Ross * - gist skiplist.c * - khash.h * - async_nif.h */ #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: * * - Skiplists: a probabilistic alternative to balanced trees. * https://www.cl.cam.ac.uk/teaching/2005/Algorithms/skiplists.pdf * 1990 William Pugh published: */ /* * Skiplist declarations. */ #ifndef SKIPLIST_MAX_HEIGHT #define SKIPLIST_MAX_HEIGHT 1 #endif #define SKIPLIST_ENTRY(type) \ struct __skiplist_entry { \ struct __skiplist_idx { \ struct type *prev, **next; \ size_t cap, len; \ } sle; \ } /* * Skip List access methods. */ #define SKIP_FIRST(head) ((head)->slh_head) #define SKIP_LAST(head) ((head)->slh_tail) #define SKIP_NEXT(elm, field) ((elm)->field.sle.next[0]) #define SKIP_PREV(elm, field) ((elm)->field.sle.prev) #define SKIP_EMPTY(head) ((head)->length == 0) /* * Skip List functions. */ #define SKIP_COMPARATOR(list, type, fn) \ int __skip_cmp_##type(struct list *head, struct type *a, struct type *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 \ } #define SKIPLIST_DECL(decl, prefix, field, free_node_blk, update_node_blk, snap_node_blk, array_type, into_array_blk) \ \ /* Skiplist node type */ \ typedef struct decl##_node decl##_node_t; \ \ /* Skiplist type */ \ typedef struct decl { \ size_t level, length, max; \ int (*cmp)(struct decl *, decl##_node_t *, decl##_node_t *, void *); \ void *aux; \ decl##_node_t *slh_head; \ decl##_node_t *slh_tail; \ } decl##_t; \ \ typedef struct decl##_snap { \ decl##_t list; \ decl##_node_t **nodes; \ } decl##_snap_t; \ \ struct __##decl##_path { \ size_t cap; \ size_t len; \ struct decl##_node **nodes; \ }; \ \ /* -- __skip_key_compare_ \ * \ * This function takes four arguments: \ * - a reference to the Skiplist \ * - 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 == slist->slh_head || b == slist->slh_tail) \ return -1; \ if (a == slist->slh_tail || b == slist->slh_head) \ return 1; \ return slist->cmp(slist, a, b, aux); \ } \ \ /* -- __skip_toss_ \ * A "coin toss" function that is critical to the proper operation of the \ * Skiplist. 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_alloc_node_ */ \ 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_idx) * slist->max; \ n = (decl##_node_t *)calloc(1, sizeof(decl##_node_t) + sle_arr_sz); \ if (n == NULL) \ return ENOMEM; \ n->field.sle.cap = slist->max; \ n->field.sle.len = 0; \ n->field.sle.next = (decl##_node_t **)((uintptr_t)n + sizeof(decl##_node_t)); \ *node = n; \ return 0; \ } \ \ /* -- skip_init_ \ * \ */ \ 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->level = 0; \ slist->length = 0; \ slist->max = (size_t)(max < 0 ? -max : max); \ slist->max = SKIPLIST_MAX_HEIGHT == 1 ? slist->max : SKIPLIST_MAX_HEIGHT; \ if (SKIPLIST_MAX_HEIGHT > 1 && slist->max > SKIPLIST_MAX_HEIGHT) \ return -1; \ slist->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.len = slist->max; \ for (i = 0; i < slist->max; i++) \ slist->slh_head->field.sle.next[i] = slist->slh_tail; \ slist->slh_head->field.sle.prev = NULL; \ \ slist->slh_tail->field.sle.len = slist->max; \ for (i = 0; i < slist->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_ */ \ void prefix##skip_free_node_##decl(decl##_node_t *node) \ { \ free_node_blk; \ free(node); \ } \ \ /* -- skip_size_ */ \ int prefix##skip_size_##decl(decl##_t *slist) \ { \ return slist->length; \ } \ \ /* -- skip_empty_ */ \ int prefix##skip_empty_##decl(decl##_t *slist) \ { \ return slist->length == 0; \ } \ \ /* -- skip_head_ */ \ decl##_node_t *prefix##skip_head_##decl(decl##_t *slist) \ { \ return slist->slh_head->field.sle.next[0]; \ } \ \ /* -- skip_tail_ */ \ decl##_node_t *prefix##skip_tail_##decl(decl##_t *slist) \ { \ return slist->slh_tail->field.sle.prev; \ } \ \ /* -- __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->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->level; \ do { \ while (elm && __skip_key_compare_##decl(slist, elm->field.sle.next[i], n, slist->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->aux) == 0) { \ path[0] = elm; \ } \ return len; \ } \ \ /* -- __skip_insert_ */ \ static int __skip_insert_##decl(decl##_t *slist, decl##_node_t *n, int flags) \ { \ static decl##_node_t apath[SKIPLIST_MAX_HEIGHT + 1]; \ size_t i, len, level; \ decl##_node_t *node, **path = (decl##_node_t **)&apath; \ \ if (slist == NULL || n == NULL) \ return ENOENT; \ \ /* Allocate a buffer */ \ if (SKIPLIST_MAX_HEIGHT == 1) { \ path = malloc(sizeof(decl##_node_t *) * slist->max + 1); \ if (path == NULL) \ return ENOMEM; \ } \ \ len = __skip_locate_##decl(slist, n, path); \ node = path[0]; \ if (len > 0) { \ if ((node != NULL) && (flags == 0)) { \ /* Don't insert, duplicate flag not set. */ \ return -1; \ } \ level = __skip_toss_##decl(slist->max - 1); \ n->field.sle.len = level + 1; \ for (i = 0; i <= level; i++) { \ if (i <= slist->level) { \ n->field.sle.next[i] = path[i + 1]->field.sle.next[i]; \ path[i + 1]->field.sle.next[i] = n; \ } else { \ n->field.sle.next[i] = slist->slh_tail; \ } \ } \ n->field.sle.prev = path[1]; \ if (n->field.sle.next[0] == slist->slh_tail) { \ slist->slh_tail->field.sle.prev = n; \ } \ if (level > slist->level) { \ slist->level = level; \ slist->slh_head->entries.sle.len = slist->level; \ slist->slh_tail->entries.sle.len = slist->level; \ } \ slist->length++; \ \ if (SKIPLIST_MAX_HEIGHT == 1) \ free(path); \ } \ return 0; \ } \ \ /* -- skip_insert_ */ \ int prefix##skip_insert_##decl(decl##_t *slist, decl##_node_t *n) \ { \ return __skip_insert_##decl(slist, n, 0); \ } \ \ /* -- skip_insert_dup_ */ \ int prefix##skip_insert_dup_##decl(decl##_t *slist, decl##_node_t *n) \ { \ return __skip_insert_##decl(slist, n, 1); \ } \ \ /* -- skip_find_ \ * Find a node that matches another node. This differs from the locate() \ * API in that it does not return the path to the node, only the match. \ * This avoids an alloc/free for the path. \ */ \ decl##_node_t *prefix##skip_find_##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->level; \ \ do { \ while (elm && __skip_key_compare_##decl(slist, elm->field.sle.next[i], n, slist->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->aux) == 0) { \ return elm; \ } \ return NULL; \ } \ \ /* -- skip_find_gte \ * Return the matching node or the next greater node after that. \ */ \ decl##_node_t *prefix##skip_find_gte_##decl(decl##_t *slist, decl##_node_t *n) \ { \ int cmp; \ unsigned int i; \ decl##_node_t *elm = slist->slh_head; \ \ if (slist == NULL || n == NULL) \ return NULL; \ \ i = slist->level; \ \ do { \ while (elm && __skip_key_compare_##decl(slist, elm->field.sle.next[i], n, slist->aux) < 0) \ elm = elm->field.sle.next[i]; \ } while (i--); \ do { \ elm = elm->field.sle.next[0]; \ cmp = __skip_key_compare_##decl(slist, elm, n, slist->aux); \ } while (cmp < 0); \ return elm; \ } \ \ /* -- skip_find_lte \ * Return the matching node or the last one before it. \ */ \ decl##_node_t *prefix##skip_find_lte_##decl(decl##_t *slist, decl##_node_t *n) \ { \ int cmp; \ unsigned int i; \ decl##_node_t *elm = slist->slh_head; \ \ if (slist == NULL || n == NULL) \ return NULL; \ \ i = slist->level; \ \ do { \ while (elm && __skip_key_compare_##decl(slist, elm->field.sle.next[i], n, slist->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->aux) == 0) { \ return elm; \ } else { \ do { \ elm = elm->field.sle.prev; \ cmp = __skip_key_compare_##decl(slist, elm, n, slist->aux); \ } while (cmp > 0); \ } \ return elm; \ } \ \ /* -- 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) \ { \ decl##_node_t *node; \ \ if (slist == NULL || new == NULL) \ return -1; \ \ node = prefix##skip_find_##decl(slist, new); \ if (node) { \ update_node_blk; \ return 0; \ } \ return -1; \ } \ \ /* -- skip_remove_ */ \ int prefix##skip_remove_##decl(decl##_t *slist, decl##_node_t *n) \ { \ static decl##_node_t apath[SKIPLIST_MAX_HEIGHT + 1]; \ size_t i, len, level; \ decl##_node_t *node, **path = (decl##_node_t **)&apath; \ \ if (slist == NULL || n == NULL) \ return -1; \ if (slist->length == 0) \ return 0; \ \ /* Allocate a buffer */ \ if (SKIPLIST_MAX_HEIGHT == 1) { \ path = malloc(sizeof(decl##_node_t *) * slist->max + 1); \ if (path == NULL) \ return ENOMEM; \ } \ \ len = __skip_locate_##decl(slist, n, path); \ node = path[0]; \ if (node) { \ node->field.sle.next[0]->field.sle.prev = node->field.sle.prev; \ for (i = 1; i <= len; i++) { \ if (path[i]->field.sle.next[i - 1] != node) \ break; \ path[i]->field.sle.next[i - 1] = node->field.sle.next[i - 1]; \ if (path[i]->field.sle.next[i - 1] == slist->slh_tail) { \ level = path[i]->field.sle.len; \ path[i]->field.sle.len = level - 1; \ } \ } \ if (SKIPLIST_MAX_HEIGHT == 1) \ free(path); \ free_node_blk; \ \ /* Find all levels in the first element in the list that point \ at the tail and shrink the level. */ \ i = 0; \ node = slist->slh_head; \ while (node->field.sle.next[i] != slist->slh_tail && i++ < slist->level) \ ; \ slist->level = i; \ slist->slh_head->field.sle.len = i; \ slist->slh_tail->field.sle.len = i; \ slist->length--; \ } \ return 0; \ } \ \ /* -- skip_next_node_ */ \ 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_ */ \ 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_destroy_ */ \ int prefix##skip_destroy_##decl(decl##_t *slist) \ { \ decl##_node_t *node, *next; \ \ if (slist == NULL) \ return 0; \ if (prefix##skip_size_##decl(slist) == 0) \ return 0; \ 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); \ \ free(slist->slh_head); \ free(slist->slh_tail); \ return 0; \ } \ \ /* -- skip_snapshot_ \ * A snapshot is a read-only view of a Skiplist at a point in \ * time. Once taken, a snapshot must be restored or disposed. \ * Any number of snapshots can be created. \ * \ * NOTE: There are many fancy algorithms for this, for now \ * this implementation will simply create a copy of the nodes. \ */ \ decl##_snap_t *prefix##skip_snapshot_##decl(decl##_t *slist) \ { \ size_t i; \ decl##_snap_t *snap; \ decl##_node_t *node, *new; \ \ if (slist == NULL) \ return 0; \ if (prefix##skip_size_##decl(slist) == 0) \ return 0; \ \ snap = (decl##_snap_t *)calloc(1, sizeof(decl##_snap_t) + (slist->length * sizeof(decl##_node_t))); \ if (snap == NULL) \ return NULL; \ \ snap->list.level = slist->level; \ snap->list.length = slist->length; \ snap->list.max = slist->max; \ snap->nodes = (decl##_node_t **)(snap + sizeof(decl##_snap_t)); \ \ node = prefix##skip_head_##decl(slist); \ i = 0; \ do { \ new = (decl##_node_t *)snap->nodes + (i * sizeof(decl##_node_t)); \ snap_node_blk; \ node = prefix##skip_next_node_##decl(slist, node); \ } while (++i < slist->length); \ return snap; \ } \ \ /* -- skip_restore_snapshot_ */ \ decl##_t *prefix##skip_restore_snapshot_##decl(decl##_snap_t *snap, int (*cmp)(decl##_t * head, decl##_node_t * a, decl##_node_t * b, void *aux)) \ { \ int rc; \ size_t i; \ decl##_t *slist; \ decl##_node_t *node, *new; \ \ if (snap == NULL || cmp == NULL) \ return 0; \ slist = (decl##_t *)calloc(1, sizeof(decl##_t)); \ if (slist == NULL) \ return NULL; \ \ slist->cmp = cmp; \ slist->level = snap->list.level; \ slist->length = snap->list.length; \ slist->max = snap->list.max; \ 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.len = slist->max; \ for (i = 0; i < slist->max; i++) \ slist->slh_head->field.sle.next[i] = slist->slh_tail; \ slist->slh_head->field.sle.prev = NULL; \ \ slist->slh_tail->field.sle.len = slist->max; \ for (i = 0; i < slist->max; i++) \ slist->slh_tail->field.sle.next[i] = NULL; \ slist->slh_tail->field.sle.prev = slist->slh_head; \ \ i = 0; \ do { \ rc = prefix##skip_alloc_node_##decl(slist, &new); \ node = (decl##_node_t *)snap->nodes + (i * sizeof(decl##_node_t)); \ snap_node_blk; \ __skip_insert_##decl(slist, new, 1); \ } while (++i < slist->length); \ return 0; \ fail:; \ if (slist->slh_head) \ free(slist->slh_head); \ if (slist->slh_tail) \ free(slist->slh_tail); \ return NULL; \ } \ \ /* -- skip_dispose_snapshot_ */ \ int prefix##skip_dispose_snapshot_##decl(decl##_snap_t *snap) \ { \ size_t i; \ decl##_node_t *node = snap->nodes[0]; \ \ i = 0; \ do { \ node = (decl##_node_t *)snap->nodes[i]; \ free_node_blk; \ } while (++i < snap->list.length); \ free(snap); \ return 0; \ } \ \ /* -- skip_to_array_ */ \ int prefix##skip_to_array_##decl(decl##_t *slist) \ { \ ((void)slist); /* TODO array_type into_array_blk */ \ return 0; \ } \ \ /* -- skip_from_array_ */ \ int prefix##skip_from_array_##decl(decl##_t *slist) \ { \ ((void)slist); /* TODO */ \ return 0; \ } \ \ /* -- __skip_integrity_check_ */ \ static int __skip_integrity_check_##decl(decl##_t *slist) \ { \ ((void)slist); /* TODO */ \ return 0; \ } #define SKIPLIST_GETTERS(decl, prefix, ktype, vtype, qblk, rblk) \ vtype prefix##skip_get_##decl(decl##_t *slist, ktype key) \ { \ decl##_node_t *node, query; \ \ qblk; \ node = prefix##skip_find_##decl(slist, &query); \ if (node) { \ rblk; \ } \ return (vtype)0; \ } \ vtype prefix##skip_gte_##decl(decl##_t *slist, ktype key) \ { \ decl##_node_t *node, query; \ \ qblk; \ node = prefix##skip_find_gte_##decl(slist, &query); \ if (node != slist->slh_tail) { \ rblk; \ } \ return (vtype)0; \ } \ vtype prefix##skip_lte_##decl(decl##_t *slist, ktype key) \ { \ decl##_node_t *node, query; \ \ qblk; \ node = prefix##skip_find_lte_##decl(slist, &query); \ if (node != slist->slh_head) { \ rblk; \ } \ return (vtype)0; \ } #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 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 level, height = node->field.sle.len; \ decl##_node_t *next; \ \ fprintf(os, "\"node%zu %p\"", nsg, (void *)node); \ fprintf(os, " [label = \""); \ level = height; \ while (level--) { \ fprintf(os, " { | %p } |", level, level, (void *)node->field.sle.next[level]); \ } \ if (fn) { \ fn(node, buf); \ fprintf(os, " %s\"\n", buf); \ } else { \ fprintf(os, " ?\"\n"); \ } \ fprintf(os, "shape = \"record\"\n"); \ fprintf(os, "];\n"); \ \ /* Now edges */ \ level = 0; \ for (level = 0; level < height; level++) { \ fprintf(os, "\"node%zu %p\"", nsg, (void *)node); \ fprintf(os, ":f%zu -> ", level); \ fprintf(os, "\"node%zu %p\"", nsg, (void *)node->field.sle.next[level]); \ fprintf(os, ":w%zu [];\n", level); \ } \ next = prefix##skip_next_node_##decl(slist, node); \ if (next) \ __skip_dot_node_##decl(os, slist, next, nsg, fn); \ } \ \ /* -- __skip_dot_finish_ \ * Finalize the DOT file of the internal representation. \ */ \ static void __skip_dot_finish_##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%zu -> HeadNode%zu [style=invis];\n", i, i); \ } \ nsg = 0; \ } \ fprintf(os, "}\n"); \ } \ \ /* -- skip_dot_start_ */ \ static int __skip_dot_start_##decl(FILE *os, decl##_t *slist, size_t nsg, skip_sprintf_node_##decl##_t fn) \ { \ size_t level; \ decl##_node_t *head, *tail; \ 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%zu {\n", nsg); \ fprintf(os, "style=dashed\n"); \ fprintf(os, "label=\"Skip list iteration %zu\"\n\n", nsg); \ fprintf(os, "\"HeadNode%zu\" [\n", nsg); \ fprintf(os, "label = \""); \ \ /* Write out the fields */ \ head = slist->slh_head; \ if (SKIP_EMPTY(slist)) \ fprintf(os, "Empty HeadNode"); \ else { \ level = head->field.sle.len - 1; \ do { \ decl##_node_t *node = head->field.sle.next[level]; \ fprintf(os, "{ %p }", level, (void *)node); \ if (level && head->field.sle.next[level] != slist->slh_tail) \ fprintf(os, " | "); \ } while (level-- && head->field.sle.next[level] != slist->slh_tail); \ } \ fprintf(os, "\"\n"); \ fprintf(os, "shape = \"record\"\n"); \ fprintf(os, "];\n"); \ \ /* Edges for head node */ \ decl##_node_t *node = slist->slh_head; \ for (level = 0; level < slist->slh_head->field.sle.len; level++) { \ if (node->field.sle.next[level] == slist->slh_tail) \ break; \ fprintf(os, "\"HeadNode%zu\":f%zu -> ", nsg, level); \ fprintf(os, "\"node%zu %p\"", nsg, (void *)node->field.sle.next[level]); \ fprintf(os, ":w%zu [];\n", level); \ } \ fprintf(os, "\n"); \ \ /* Now all nodes via level 0, if non-empty */ \ node = prefix##skip_head_##decl(slist); \ if (node) \ __skip_dot_node_##decl(os, slist, node, nsg, fn); \ fprintf(os, "\n"); \ \ /* The tail, sentinal node */ \ tail = slist->slh_tail; \ if (!SKIP_EMPTY(slist)) { \ fprintf(os, "\"node%zu %p\" [label = \"", nsg, (void *)slist->slh_tail); \ level = tail->field.sle.len - 1; \ do { \ fprintf(os, " %p", level, (void *)node->field.sle.prev); \ if (level && node->field.sle.prev != slist->slh_head) \ fprintf(os, " | "); \ } while (level-- && node->field.sle.prev != slist->slh_head); \ fprintf(os, "\" shape = \"record\"];\n"); \ } \ \ /* End: "subgraph cluster0 {" */ \ fprintf(os, "}\n\n"); \ nsg += 1; \ \ return nsg; \ } \ \ /* -- skip_dot_ \ * Create a DOT file of the internal representation of the \ * Skiplist 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, skip_sprintf_node_##decl##_t fn) \ { \ if (__skip_integrity_check_##decl(slist) != 0) { \ perror("Skiplist failed integrity checks, impossible to diagram."); \ return -1; \ } \ if (os == NULL) \ os = stdout; \ if (!os) { \ perror("Failed to open output file, unable to write DOT file."); \ return -1; \ } \ __skip_dot_start_##decl(os, slist, nsg, fn); \ __skip_dot_finish_##decl(os, nsg); \ return 0; \ } #endif /* _SKIPLIST_H_ */