ucx/avl.c

/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright 2015 Olaf Wintermann. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *
 *   2. Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include "avl.h"

#define ptrcast(ptr) ((void*)(ptr))

static void ucx_avl_connect(UcxAVLTree *tree,
        UcxAVLNode *node, UcxAVLNode *child, intptr_t nullkey) {
    if (child) {
        child->parent = node;
    }
    // if child is NULL, nullkey decides if left or right pointer is cleared
    if (tree->cmpfunc(
        ptrcast(child ? child->key : nullkey),
        ptrcast(node->key), tree->userdata) > 0) {
      node->right = child;
    } else {
      node->left = child;
    }
    size_t lh = node->left ? node->left->height : 0;
    size_t rh = node->right ? node->right->height : 0;
    node->height = 1 + (lh > rh ? lh : rh);
}

#define avlheight(node) ((node) ? (node)->height : 0)

static UcxAVLNode* avl_rotright(UcxAVLTree *tree, UcxAVLNode *l0) {
    UcxAVLNode *p = l0->parent;
    UcxAVLNode *l1 = l0->left;
    if (p) {
        ucx_avl_connect(tree, p, l1, 0);
    } else {
        l1->parent = NULL;
    }
    ucx_avl_connect(tree, l0, l1->right, l1->key);
    ucx_avl_connect(tree, l1, l0, 0);
    return l1;
}

static UcxAVLNode* avl_rotleft(UcxAVLTree *tree, UcxAVLNode *l0) {
    UcxAVLNode *p = l0->parent;
    UcxAVLNode *l1 = l0->right;
    if (p) {
        ucx_avl_connect(tree, p, l1, 0);
    } else {
        l1->parent = NULL;
    }
    ucx_avl_connect(tree, l0, l1->left, l1->key);
    ucx_avl_connect(tree, l1, l0, 0);
    return l1;
}

static void ucx_avl_balance(UcxAVLTree *tree, UcxAVLNode *n) {
    int lh = avlheight(n->left);
    int rh = avlheight(n->right);
    n->height = 1 + (lh > rh ? lh : rh);
    
    if (lh - rh == 2) {
      UcxAVLNode *c = n->left;
      if (avlheight(c->right) - avlheight(c->left) == 1) {
        avl_rotleft(tree, c);
      }
      n = avl_rotright(tree, n);
    } else if (rh - lh == 2) {  
      UcxAVLNode *c = n->right;
      if (avlheight(c->left) - avlheight(c->right) == 1) {
        avl_rotright(tree, c);
      }
      n = avl_rotleft(tree, n);
    }

    if (n->parent) {
      ucx_avl_balance(tree, n->parent);
    } else {
      tree->root = n;
    }
}

UcxAVLTree *ucx_avl_new(cmp_func cmpfunc) {
    return ucx_avl_new_a(cmpfunc, ucx_default_allocator());
}

UcxAVLTree *ucx_avl_new_a(cmp_func cmpfunc, UcxAllocator *allocator) {
    UcxAVLTree *tree = almalloc(allocator, sizeof(UcxAVLTree));
    if (tree) {
        tree->allocator = allocator;
        tree->cmpfunc = cmpfunc;
        tree->root = NULL;
        tree->userdata = NULL;
    }
    
    return tree;
}

static void ucx_avl_free_node(UcxAllocator *al, UcxAVLNode *node) {
    if (node) {
        ucx_avl_free_node(al, node->left);
        ucx_avl_free_node(al, node->right);
        alfree(al, node);
    }
}

void ucx_avl_free(UcxAVLTree *tree) {
    UcxAllocator *al = tree->allocator;
    ucx_avl_free_node(al, tree->root);
    alfree(al, tree);
}

void *ucx_avl_get(UcxAVLTree *tree, intptr_t key) {
    UcxAVLNode *n = tree->root;
    int cmpresult;
    while (n && (cmpresult = tree->cmpfunc(
            ptrcast(key), ptrcast(n->key), tree->userdata))) {
        n = cmpresult > 0 ? n->right : n->left;
    }
    return n ? n->value : NULL;
}

void* ucx_avl_put(UcxAVLTree *tree, intptr_t key, void *value) {
    if (tree->root) {
        UcxAVLNode *n = tree->root;
        int cmpresult;
        while ((cmpresult = tree->cmpfunc(
                ptrcast(key), ptrcast(n->key), tree->userdata))) {
            UcxAVLNode *m = cmpresult > 0 ? n->right : n->left;
            if (m) {
                n = m;
            } else {
                break;
            }
        }

        if (cmpresult) {
            UcxAVLNode *e = almalloc(tree->allocator, sizeof(UcxAVLNode));
            e->key = key; e->value = value; e->height = 1;
            e->parent = e->left = e->right = NULL;
            ucx_avl_connect(tree, n, e, 0);
            ucx_avl_balance(tree, n);
            return NULL;
        } else {
            void *prevval = n->value;
            n->value = value;
            return prevval;
        }
    } else {
        tree->root = almalloc(tree->allocator, sizeof(UcxAVLNode));
        tree->root->key = key; tree->root->value = value;
        tree->root->height = 1;
        tree->root->parent = tree->root->left = tree->root->right = NULL;
        return NULL;
    }
}

void* ucx_avl_remove(UcxAVLTree *tree, intptr_t key) {
    UcxAVLNode *n = tree->root;
    int cmpresult;
    while (n && (cmpresult = tree->cmpfunc(
            ptrcast(key), ptrcast(n->key), tree->userdata))) {
        n = cmpresult > 0 ? n->right : n->left;
    }
    if (n) {
        void *prevval = n->value;
        UcxAVLNode *p = n->parent;
        if (n->left && n->right) {
            UcxAVLNode *s = n->right;
            while (s->left) {
                s = s->left;
            }
            ucx_avl_connect(tree, s->parent, s->right, s->key);
            n->key = s->key; n->value = s->value;
            p = s->parent;
            alfree(tree->allocator, s);
        } else {
            if (p) {
                ucx_avl_connect(tree, p, n->right ? n->right:n->left, n->key);
            } else {
                tree->root = n->right ? n->right : n->left;
                if (tree->root) {
                    tree->root->parent = NULL;
                }
            }
            alfree(tree->allocator, n);
        }

        if (p) {
            ucx_avl_balance(tree, p);
        }
        return prevval;
    } else {
        return NULL;
    }
}

static size_t ucx_avl_countn(UcxAVLNode *node) {
    if (node) {
        return 1 + ucx_avl_countn(node->left) + ucx_avl_countn(node->right);
    } else {
        return 0;
    }
}

size_t ucx_avl_count(UcxAVLTree *tree) {
    return ucx_avl_countn(tree->root);
}