When I study the rbtree of nginx I can’t understand the comments. Can
someone give me a concrete example?Thanks 
for ( ;; ) {
/*
* Timer values
* 1) are spread in small range, usually several minutes,
* 2) and overflow each 49 days, if milliseconds are stored in
32
bits.
* The comparison takes into account that overflow.
*/
/* node->key < temp->key */
p = ((ngx_rbtree_key_int_t) (node->key - temp->key) < 0)
? &temp->left : &temp->right;
if (*p == sentinel) {
break;
}
temp = *p;
}
Hello!
On Tue, Mar 24, 2015 at 03:39:23PM +0800, 张奕普 wrote:
When I study the rbtree of nginx I can’t understand the comments. Can
someone give me a concrete example?Thanks 
[…]
? &temp->left : &temp->right;
Consider (assuming 32-bit keys):
node->key = 4294967295
temp->key = 0
The 0 value is bigger, because it’s (4294967295 + 1). And that’s
what the code checks. The
(ngx_rbtree_key_int_t) (node->key - temp->key)
evaluates to
(ngx_rbtree_key_int_t) (4294967295 - 0)
and becomes negative after casting to signed (note: this
conversion result is actually implementation-defined, but this is
how it works in practice).
–
Maxim D.
http://nginx.org/