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/*
* AVL tree map for hashed items.
*
* Copyright © 2021-2025 Samuel Lidén Borell <samuel@kodafritt.se>
*
* SPDX-License-Identifier: EUPL-1.2+
*/
#include <assert.h>
#include <string.h>
#include "compiler.h"
#define RDZERO 0
#define RDMINUS 1
#define RDPLUS 2
int treenode_equals(const struct TreeNode *n, const char *s, size_t len)
{
if (n->length != len) return 0;
return !memcmp(n->name, s, len);
}
/**
* Compares the node a with the sought value b
* \return -1 if b is larger, 0 if equal, 1 if a is larger
*/
static int ncmp(const struct TreeNode *a,
HashCode bhash, size_t blen, const char *bname)
{
size_t alen;
/* Sort by hash first */
if (a->hashcode < bhash) return -1;
if (a->hashcode > bhash) return 1;
/* Sort by length second */
alen = a->length;
if (alen < blen) return -1;
if (alen > blen) return 1;
/* Sort by contents as a last resort */
return memcmp(a->name, bname, alen);
}
struct TreeNode *tree_search(const struct TreeNode *root,
HashCode h, size_t len, const char *name)
{
const struct TreeNode *n = root;
while (n) {
int cmp = ncmp(n, h, len, name);
if (cmp == 0) return (struct TreeNode *)n;
else if (cmp > 0) n = n->lower;
else n = n->higher;
}
return NULL;
}
struct TreeNode *tree_search_node(const struct TreeNode *root,
const struct TreeNode *n)
{
return tree_search(root, n->hashcode, n->length, n->name);
}
static struct TreeNode *rotate_left(struct TreeNode *n)
{
struct TreeNode *higher = n->higher;
n->higher = higher->lower;
higher->lower = n;
n->rankdelta = higher->rankdelta = RDZERO;
return higher;
}
static struct TreeNode *rotate_right(struct TreeNode *n)
{
struct TreeNode *lower = n->lower;
n->lower = lower->higher;
lower->higher = n;
n->rankdelta = lower->rankdelta = RDZERO;
return lower;
}
static struct TreeNode *rotate_leftright(struct TreeNode *base)
{
struct TreeNode *l = base->lower; /* ___________b_ */
struct TreeNode *lh = l->higher; /* __l____ h */
base->lower = lh->higher; /* ll _lh_ */
l->higher = lh->lower; /* lhl lhh */
lh->higher = base;
lh->lower = l; /* becomes */
if (lh->rankdelta == RDMINUS) {
base->rankdelta = RDPLUS; /* _____lh____ */
l->rankdelta = RDZERO; /* __l__ _b_ */
} else { /* ll lhl lhh h */
base->rankdelta = RDZERO;
l->rankdelta = RDMINUS;
}
lh->rankdelta = RDZERO;
return lh;
}
/** Performs a right-left rotation and returns the new subtree root */
static struct TreeNode *rotate_rightleft(struct TreeNode *base)
{
struct TreeNode *h = base->higher; /* _b___________ */
struct TreeNode *hl = h->lower; /* l ____h__ */
base->higher = hl->lower; /* _hl_ hh */
h->lower = hl->higher; /* hll hlh */
hl->lower = base;
hl->higher = h; /* becomes */
if (hl->rankdelta == RDPLUS) {
base->rankdelta = RDMINUS; /* ____hl_____ */
h->rankdelta = RDZERO; /* _b_ __h__ */
} else { /* l hll hlh hhh */
base->rankdelta = RDZERO;
h->rankdelta = RDPLUS;
}
hl->rankdelta = RDZERO;
return hl;
}
static struct TreeNode *create_node(HashCode h, size_t len, const char *name,
struct TreeNode *newnode, size_t newsize)
{
if (!newnode) {
newnode = malloc(newsize);
NO_NULL(newnode);
}
newnode->lower = NULL;
newnode->higher = NULL;
newnode->hashcode = h;
newnode->rankdelta = RDZERO;
assert(len <= TREENODE_LEN_MAX);
newnode->length = (TREENODE_LEN_TYPE)len;
newnode->is_new = 1;
newnode->is_defined = 0;
newnode->name = memzdup(name, len);
return newnode;
}
struct TreeNode *tree_insert_str(struct TreeNode **root,
const char *name, size_t len,
struct TreeNode *newnode, size_t newsize)
{
return tree_insert(root, hash_str(name, len), name, len, newnode, newsize);
}
struct TreeNode *tree_insert(struct TreeNode **root,
HashCode h, const char *name, size_t len,
struct TreeNode *newnode, size_t newsize)
{
struct TreeNode *path[TREE_MAXDEPTH];
struct TreeNode **lastp;
struct TreeNode *n, *rotroot;
struct TreeNode **inspoint;
size_t length;
short depth;
assert(len <= TREENODE_LEN_MAX);
if (!*root) {
n = create_node(h, len, name, newnode, newsize);
*root = n;
return n;
}
length = len;
lastp = &path[0];
depth = 0;
n = *root;
/* Insert */
for (;;) {
int cmp;
if (++depth >= TREE_MAXDEPTH) goto too_deep;
*lastp = n;
cmp = ncmp(n, h, length, name);
if (cmp == 0) {
n->is_new = 0;
return n;
} else if (cmp > 0) {
inspoint = &n->lower;
n = n->lower;
} else {
inspoint = &n->higher;
n = n->higher;
}
if (!n) break;
lastp++;
}
n = create_node(h, len, name, newnode, newsize);
*inspoint = n;
newnode = n;
/* Rebalance if necessary.
This is done by backtracking through the path. */
for (;;) { /* while depth > 0 */
struct TreeNode *p = *lastp;
assert(n->lower || n->rankdelta != RDMINUS);
assert(n->higher || n->rankdelta != RDPLUS);
if (p->lower == n) { /* new node is in left/lower subtree */
if (p->rankdelta == RDMINUS) {
if (n->rankdelta == RDPLUS) {
rotroot = rotate_leftright(p);
} else {
rotroot = rotate_right(p);
}
} else if (p->rankdelta == RDPLUS) {
p->rankdelta = RDZERO;
break;
} else {
p->rankdelta = RDMINUS;
goto continue_up;
}
} else { /* new node is in right/higher subtree */
assert(p->higher == n);
if (p->rankdelta == RDPLUS) {
if (n->rankdelta == RDMINUS) {
rotroot = rotate_rightleft(p);
} else {
rotroot = rotate_left(p);
}
} else if (p->rankdelta == RDMINUS) {
p->rankdelta = RDZERO;
break;
} else {
p->rankdelta = RDPLUS;
goto continue_up;
}
}
if (depth <= 1) *root = rotroot;
else if (lastp[-1]->lower == p) {
lastp[-1]->lower = rotroot;
} else {
assert(lastp[-1]->higher == p);
lastp[-1]->higher = rotroot;
}
break;
continue_up:
if (!--depth) break;
lastp--;
n = p;
}
return newnode;
too_deep:
error("Tree structure too deep.");
return NULL;
}
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