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HTMLPurifier_Zipper

A zipper is a purely-functional data structure which contains a focus that can be efficiently manipulated. It is known as a "one-hole context". This mutable variant implements a zipper for a list as a pair of two arrays, laid out as follows:

Base list: 1 2 3 4 [ ] 6 7 8 9 Front list: 1 2 3 4 Back list: 9 8 7 6

User is expected to keep track of the "current element" and properly fill it back in as necessary. (ToDo: Maybe it's more user friendly to implicitly track the current element?)

Nota bene: the current class gets confused if you try to store NULLs in the list.

  • Full name: \HTMLPurifier_Zipper

Properties

front

public $front

back

public $back

Methods

__construct

public __construct(mixed $front, mixed $back): mixed

Parameters:

Parameter Type Description
$front mixed
$back mixed

fromArray

Creates a zipper from an array, with a hole in the 0-index position.

public static fromArray(mixed $array): \Tuple
  • This method is static.

Parameters:

Parameter Type Description
$array mixed

Return Value:

of zipper and element of first position.

toArray

Convert zipper back into a normal array, optionally filling in the hole with a value. (Usually you should supply a $t, unless you are at the end of the array.)

public toArray(mixed $t = NULL): mixed

Parameters:

Parameter Type Description
$t mixed

next

Move hole to the next element.

public next(mixed $t): \Original

Parameters:

Parameter Type Description
$t mixed Element to fill hole with

Return Value:

contents of new hole.

advance

Iterated hole advancement.

public advance(mixed $t, mixed $n): \Original

Parameters:

Parameter Type Description
$t mixed Element to fill hole with
$n mixed

Return Value:

contents of new hole, i away

prev

Move hole to the previous element

public prev(mixed $t): \Original

Parameters:

Parameter Type Description
$t mixed Element to fill hole with

Return Value:

contents of new hole.

delete

Delete contents of current hole, shifting hole to next element.

public delete(): \Original

Return Value:

contents of new hole.

done

Returns true if we are at the end of the list.

public done(): bool

insertBefore

Insert element before hole.

public insertBefore(mixed $t): mixed

Parameters:

Parameter Type Description
$t mixed

insertAfter

Insert element after hole.

public insertAfter(mixed $t): mixed

Parameters:

Parameter Type Description
$t mixed

splice

Splice in multiple elements at hole. Functional specification in terms of array_splice:

public splice(mixed $t, mixed $delete, mixed $replacement): mixed

$arr1 = $arr; $old1 = array_splice($arr1, $i, $delete, $replacement);

 list($z, $t) = HTMLPurifier_Zipper::fromArray($arr);
 $t = $z->advance($t, $i);
 list($old2, $t) = $z->splice($t, $delete, $replacement);
 $arr2 = $z->toArray($t);

 assert($old1 === $old2);
 assert($arr1 === $arr2);

NB: the absolute index location after this operation is unchanged!

Parameters:

Parameter Type Description
$t mixed
$delete mixed
$replacement mixed

Automatically generated on 2025-03-18