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<?php
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/**
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 * Represents a measurable length, with a string numeric magnitude
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 * and a unit. This object is immutable.
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 */
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class HTMLPurifier_Length
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{
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    /**
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     * String numeric magnitude.
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     * @type string
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     */
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    protected $n;
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    /**
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     * String unit. False is permitted if $n = 0.
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     * @type string|bool
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     */
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    protected $unit;
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    /**
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     * Whether or not this length is valid. Null if not calculated yet.
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     * @type bool
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     */
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    protected $isValid;
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    /**
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     * Array Lookup array of units recognized by CSS 3
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     * @type array
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     */
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    protected static $allowedUnits = array(
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        'em' => true, 'ex' => true, 'px' => true, 'in' => true,
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        'cm' => true, 'mm' => true, 'pt' => true, 'pc' => true,
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        'ch' => true, 'rem' => true, 'vw' => true, 'vh' => true,
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        'vmin' => true, 'vmax' => true
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    );
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    /**
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     * @param string $n Magnitude
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     * @param bool|string $u Unit
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     */
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    public function __construct($n = '0', $u = false)
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    {
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        $this->n = (string) $n;
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        $this->unit = $u !== false ? (string) $u : false;
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    }
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    /**
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     * @param string $s Unit string, like '2em' or '3.4in'
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     * @return HTMLPurifier_Length
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     * @warning Does not perform validation.
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     */
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    public static function make($s)
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    {
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        if ($s instanceof HTMLPurifier_Length) {
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            return $s;
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        }
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        $n_length = strspn($s, '1234567890.+-');
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        $n = substr($s, 0, $n_length);
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        $unit = substr($s, $n_length);
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        if ($unit === '') {
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            $unit = false;
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        }
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        return new HTMLPurifier_Length($n, $unit);
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    }
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    /**
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     * Validates the number and unit.
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     * @return bool
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     */
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    protected function validate()
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    {
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        // Special case:
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        if ($this->n === '+0' || $this->n === '-0') {
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            $this->n = '0';
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        }
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        if ($this->n === '0' && $this->unit === false) {
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            return true;
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        }
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        if ($this->unit === false || !ctype_lower($this->unit)) {
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            $this->unit = strtolower($this->unit);
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        }
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        if (!isset(HTMLPurifier_Length::$allowedUnits[$this->unit])) {
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            return false;
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        }
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        // Hack:
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        $def = new HTMLPurifier_AttrDef_CSS_Number();
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        $result = $def->validate($this->n, false, false);
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        if ($result === false) {
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            return false;
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        }
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        $this->n = $result;
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        return true;
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    }
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    /**
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     * Returns string representation of number.
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     * @return string
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     */
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    public function toString()
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    {
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        if (!$this->isValid()) {
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            return false;
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        }
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        return $this->n . $this->unit;
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    }
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    /**
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     * Retrieves string numeric magnitude.
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     * @return string
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     */
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    public function getN()
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    {
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        return $this->n;
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    }
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    /**
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     * Retrieves string unit.
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     * @return string
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     */
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    public function getUnit()
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    {
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        return $this->unit;
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    }
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    /**
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     * Returns true if this length unit is valid.
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     * @return bool
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     */
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    public function isValid()
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    {
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        if ($this->isValid === null) {
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            $this->isValid = $this->validate();
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        }
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        return $this->isValid;
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    }
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    /**
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     * Compares two lengths, and returns 1 if greater, -1 if less and 0 if equal.
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     * @param HTMLPurifier_Length $l
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     * @return int
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     * @warning If both values are too large or small, this calculation will
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     *          not work properly
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     */
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    public function compareTo($l)
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    {
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        if ($l === false) {
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            return false;
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        }
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        if ($l->unit !== $this->unit) {
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            $converter = new HTMLPurifier_UnitConverter();
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            $l = $converter->convert($l, $this->unit);
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            if ($l === false) {
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                return false;
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            }
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        }
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        return $this->n - $l->n;
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    }
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}
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// vim: et sw=4 sts=4