Alert: This function’s access is marked private. This means it is not intended for use by plugin or theme developers, only in other core functions. It is listed here for completeness.
wp_find_hierarchy_loop_tortoise_hare( callable $callback, int $start, array $override = array(), array $callback_args = array(), bool $_return_loop = false ): mixed
Uses the “The Tortoise and the Hare” algorithm to detect loops.
Description
For every step of the algorithm, the hare takes two steps and the tortoise one.
If the hare ever laps the tortoise, there must be a loop.
Parameters
-
$callbackcallable Required -
Function that accepts ( ID, callback_arg, ... ) and outputs parent_ID.
-
$startint Required -
The ID to start the loop check at.
-
$overridearray Optional -
An array of ( ID => parent_ID, ... ) to use instead of $callback.
Default:
array() -
$callback_argsarray Optional -
Additional arguments to send to $callback.
Default:
array() -
$_return_loopbool Optional -
Return loop members or just detect presence of loop? Only set to true if you already know the given $start is part of a loop (otherwise the returned array might include branches).
Default:
false
Return
mixed Scalar ID of some arbitrary member of the loop, or array of IDs of all members of loop if $_return_loop
Source
File: wp-includes/functions.php.
View all references
function wp_find_hierarchy_loop_tortoise_hare( $callback, $start, $override = array(), $callback_args = array(), $_return_loop = false ) {
$tortoise = $start;
$hare = $start;
$evanescent_hare = $start;
$return = array();
// Set evanescent_hare to one past hare.
// Increment hare two steps.
while (
$tortoise
&&
( $evanescent_hare = isset( $override[ $hare ] ) ? $override[ $hare ] : call_user_func_array( $callback, array_merge( array( $hare ), $callback_args ) ) )
&&
( $hare = isset( $override[ $evanescent_hare ] ) ? $override[ $evanescent_hare ] : call_user_func_array( $callback, array_merge( array( $evanescent_hare ), $callback_args ) ) )
) {
if ( $_return_loop ) {
$return[ $tortoise ] = true;
$return[ $evanescent_hare ] = true;
$return[ $hare ] = true;
}
// Tortoise got lapped - must be a loop.
if ( $tortoise == $evanescent_hare || $tortoise == $hare ) {
return $_return_loop ? $return : $tortoise;
}
// Increment tortoise by one step.
$tortoise = isset( $override[ $tortoise ] ) ? $override[ $tortoise ] : call_user_func_array( $callback, array_merge( array( $tortoise ), $callback_args ) );
}
return false;
}
Changelog
| Version | Description |
|---|---|
| 3.1.0 | Introduced. |