Commit 700aea92 authored by Rusty Russell's avatar Rusty Russell

avl: new module

parent 3d10865d
#include <string.h>
#include "config.h"
/**
* avl - Key-value dictionary based on AVL trees
*
* A simple, well-tested implementation of AVL trees for mapping
* unique keys to values. This implementation supports insertion,
* removal, lookup, and traversal.
*
* An AVL tree is a self-balancing binary tree that performs
* insertion, removal, and lookup in O(log n) time per operation.
*
* Example:
* #include <ccan/avl/avl.h>
*
* #include <stdio.h>
* #include <stdlib.h>
* #include <string.h>
*
* struct tally {
* long count;
* };
* #define new_tally() calloc(1, sizeof(struct tally))
*
* static void chomp(char *str)
* {
* char *end = strchr(str, 0);
* if (end > str && end[-1] == '\n')
* end[-1] = 0;
* }
*
* int main(void)
* {
* AVL *avl = avl_new((AvlCompare) strcmp);
* AvlIter i;
* struct tally *tally;
* char line[256];
*
* while (fgets(line, sizeof(line), stdin))
* {
* chomp(line);
*
* tally = avl_lookup(avl, line);
* if (tally == NULL)
* avl_insert(avl, strdup(line), tally = new_tally());
*
* tally->count++;
* }
*
* avl_foreach(i, avl) {
* char *line = i.key;
* struct tally *tally = i.value;
*
* printf("% 5ld: %s\n", tally->count, line);
*
* free(line);
* free(tally);
* }
*
* avl_free(avl);
*
* return 0;
* }
*
* Licence: ISC
* Author: Joey Adams <joeyadams3.14159@gmail.com>
*/
int main(int argc, char *argv[])
{
/* Expect exactly one argument */
if (argc != 2)
return 1;
if (strcmp(argv[1], "depends") == 0) {
/* Nothing */
return 0;
}
return 1;
}
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/*
* Copyright (c) 2010 Joseph Adams <joeyadams3.14159@gmail.com>
*
* 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.
*/
#ifndef CCAN_AVL_H
#define CCAN_AVL_H
#include <stdbool.h>
#include <stddef.h>
typedef struct AVL AVL;
typedef struct AvlNode AvlNode;
typedef struct AvlIter AvlIter;
typedef int (*AvlCompare)(const void *, const void *);
AVL *avl_new(AvlCompare compare);
/* Create a new AVL tree sorted with the given comparison function. */
void avl_free(AVL *avl);
/* Free an AVL tree. */
void *avl_lookup(const AVL *avl, const void *key);
/* O(log n). Lookup a value at a key. Return NULL if the key is not present. */
#define avl_member(avl, key) (!!avl_lookup_node(avl, key))
/* O(log n). See if a key is present. */
size_t avl_count(const AVL *avl);
/* O(1). Return the number of elements in the tree. */
bool avl_insert(AVL *avl, const void *key, const void *value);
/*
* O(log n). Insert a key/value pair, or replace it if already present.
*
* Return false if the insertion replaced an existing key/value.
*/
bool avl_remove(AVL *avl, const void *key);
/*
* O(log n). Remove a key/value pair (if present).
*
* Return true if it was removed.
*/
bool avl_check_invariants(AVL *avl);
/* For testing purposes. This function will always return true :-) */
/************************* Traversal *************************/
#define avl_foreach(iter, avl) avl_traverse(iter, avl, FORWARD)
/*
* O(n). Traverse an AVL tree in order.
*
* Example:
*
* AvlIter i;
*
* avl_foreach(i, avl)
* printf("%s -> %s\n", i.key, i.value);
*/
#define avl_foreach_reverse(iter, avl) avl_traverse(iter, avl, BACKWARD)
/* O(n). Traverse an AVL tree in reverse order. */
typedef enum AvlDirection {FORWARD = 0, BACKWARD = 1} AvlDirection;
struct AvlIter {
void *key;
void *value;
AvlNode *node;
/* private */
AvlNode *stack[100];
int stack_index;
AvlDirection direction;
};
void avl_iter_begin(AvlIter *iter, AVL *avl, AvlDirection dir);
void avl_iter_next(AvlIter *iter);
#define avl_traverse(iter, avl, direction) \
for (avl_iter_begin(&(iter), avl, direction); \
(iter).node != NULL; \
avl_iter_next(&iter))
/***************** Internal data structures ******************/
struct AVL {
AvlCompare compare;
AvlNode *root;
size_t count;
};
struct AvlNode {
const void *key;
const void *value;
AvlNode *lr[2];
int balance; /* -1, 0, or 1 */
};
AvlNode *avl_lookup_node(const AVL *avl, const void *key);
/* O(log n). Lookup an AVL node by key. Return NULL if not present. */
#endif
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