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119 lines
2.9 KiB
PHP
119 lines
2.9 KiB
PHP
<?php declare(strict_types=1);
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/*
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* This file is part of Composer.
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*
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* (c) Nils Adermann <naderman@naderman.de>
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* Jordi Boggiano <j.boggiano@seld.be>
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*
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* For the full copyright and license information, please view the LICENSE
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* file that was distributed with this source code.
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*/
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namespace Composer\DependencyResolver;
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/**
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* Wrapper around a Rule which keeps track of the two literals it watches
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*
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* Used by RuleWatchGraph to store rules in two RuleWatchChains.
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*
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* @author Nils Adermann <naderman@naderman.de>
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*/
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class RuleWatchNode
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{
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/** @var int */
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public $watch1;
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/** @var int */
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public $watch2;
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/** @var Rule */
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protected $rule;
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/**
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* Creates a new node watching the first and second literals of the rule.
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*
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* @param Rule $rule The rule to wrap
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*/
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public function __construct(Rule $rule)
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{
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$this->rule = $rule;
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$literals = $rule->getLiterals();
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$literalCount = \count($literals);
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$this->watch1 = $literalCount > 0 ? $literals[0] : 0;
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$this->watch2 = $literalCount > 1 ? $literals[1] : 0;
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}
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/**
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* Places the second watch on the rule's literal, decided at the highest level
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*
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* Useful for learned rules where the literal for the highest rule is most
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* likely to quickly lead to further decisions.
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*
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* @param Decisions $decisions The decisions made so far by the solver
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* @return void
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*/
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public function watch2OnHighest(Decisions $decisions): void
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{
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$literals = $this->rule->getLiterals();
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// if there are only 2 elements, both are being watched anyway
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if (\count($literals) < 3 || $this->rule instanceof MultiConflictRule) {
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return;
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}
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$watchLevel = 0;
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foreach ($literals as $literal) {
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$level = $decisions->decisionLevel($literal);
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if ($level > $watchLevel) {
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$this->watch2 = $literal;
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$watchLevel = $level;
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}
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}
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}
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/**
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* Returns the rule this node wraps
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*
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* @return Rule
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*/
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public function getRule(): Rule
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{
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return $this->rule;
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}
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/**
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* Given one watched literal, this method returns the other watched literal
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*
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* @param int $literal The watched literal that should not be returned
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* @return int A literal
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*/
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public function getOtherWatch(int $literal): int
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{
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if ($this->watch1 == $literal) {
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return $this->watch2;
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}
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return $this->watch1;
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}
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/**
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* Moves a watch from one literal to another
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*
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* @param int $from The previously watched literal
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* @param int $to The literal to be watched now
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* @return void
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*/
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public function moveWatch(int $from, int $to): void
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{
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if ($this->watch1 == $from) {
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$this->watch1 = $to;
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} else {
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$this->watch2 = $to;
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}
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}
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}
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