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#include <assert.h>
#include <stdbool.h>
#include <stddef.h>
#include "util.h"
#define MAXH (sizeof(void *) * 8 * 3 / 2)
static inline int
height(struct treenode *n) {
return n ? n->height : 0;
}
static int
rot(void **p, struct treenode *x, int dir /* deeper side */)
{
struct treenode *y = x->child[dir];
struct treenode *z = y->child[!dir];
int hx = x->height;
int hz = height(z);
if (hz > height(y->child[dir])) {
/*
* x
* / \ dir z
* A y / \
* / \ --> x y
* z D /| |\
* / \ A B C D
* B C
*/
x->child[dir] = z->child[!dir];
y->child[!dir] = z->child[dir];
z->child[!dir] = x;
z->child[dir] = y;
x->height = hz;
y->height = hz;
z->height = hz + 1;
} else {
/*
* x y
* / \ / \
* A y --> x D
* / \ / \
* z D A z
*/
x->child[dir] = z;
y->child[!dir] = x;
x->height = hz + 1;
y->height = hz + 2;
z = y;
}
*p = z;
return z->height - hx;
}
/* balance *p, return 0 if height is unchanged. */
static int balance(void **p)
{
struct treenode *n = *p;
int h0 = height(n->child[0]);
int h1 = height(n->child[1]);
if (h0 - h1 + 1u < 3u) {
int old = n->height;
n->height = h0 < h1 ? h1 + 1 : h0 + 1;
return n->height - old;
}
return rot(p, n, h0<h1);
}
void *
treeinsert(void **root, unsigned long long key, size_t sz)
{
void **a[MAXH];
struct treenode *n = *root;
int i = 0;
a[i++] = root;
while (n) {
if (key == n->key) {
n->new = false;
return n;
}
a[i++] = &n->child[key > n->key];
n = n->child[key > n->key];
}
assert(sz > sizeof(*n));
n = xmalloc(sz);
n->key = key;
n->child[0] = n->child[1] = 0;
n->height = 1;
/* insert new node, rebalance ancestors. */
*a[--i] = n;
while (i && balance(a[--i]))
;
n->new = true;
return n;
}
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