Proyectos de Subversion Moodle

<?php

/**

 * Class for converting between different unit-lengths as specified by

 * CSS.

 */

class HTMLPurifier_UnitConverter

{

    const ENGLISH = 1;

    const METRIC = 2;

    const DIGITAL = 3;

    /**

     * Units information array. Units are grouped into measuring systems

     * (English, Metric), and are assigned an integer representing

     * the conversion factor between that unit and the smallest unit in

     * the system. Numeric indexes are actually magical constants that

     * encode conversion data from one system to the next, with a O(n^2)

     * constraint on memory (this is generally not a problem, since

     * the number of measuring systems is small.)

     */

    protected static $units = array(

        self::ENGLISH => array(

            'px' => 3, // This is as per CSS 2.1 and Firefox. Your mileage may vary

            'pt' => 4,

            'pc' => 48,

            'in' => 288,

            self::METRIC => array('pt', '0.352777778', 'mm'),

        ),

        self::METRIC => array(

            'mm' => 1,

            'cm' => 10,

            self::ENGLISH => array('mm', '2.83464567', 'pt'),

        ),

    );

    /**

     * Minimum bcmath precision for output.

     * @type int

     */

    protected $outputPrecision;

    /**

     * Bcmath precision for internal calculations.

     * @type int

     */

    protected $internalPrecision;

    /**

     * Whether or not BCMath is available.

     * @type bool

     */

    private $bcmath;

    public function __construct($output_precision = 4, $internal_precision = 10, $force_no_bcmath = false)

    {

        $this->outputPrecision = $output_precision;

        $this->internalPrecision = $internal_precision;

        $this->bcmath = !$force_no_bcmath && function_exists('bcmul');

    }

    /**

     * Converts a length object of one unit into another unit.

     * @param HTMLPurifier_Length $length

     *      Instance of HTMLPurifier_Length to convert. You must validate()

     *      it before passing it here!

     * @param string $to_unit

     *      Unit to convert to.

     * @return HTMLPurifier_Length|bool

     * @note

     *      About precision: This conversion function pays very special

     *      attention to the incoming precision of values and attempts

     *      to maintain a number of significant figure. Results are

     *      fairly accurate up to nine digits. Some caveats:

     *          - If a number is zero-padded as a result of this significant

     *            figure tracking, the zeroes will be eliminated.

     *          - If a number contains less than four sigfigs ($outputPrecision)

     *            and this causes some decimals to be excluded, those

     *            decimals will be added on.

     */

    public function convert($length, $to_unit)

    {

        if (!$length->isValid()) {

            return false;

        }

        $n = $length->getN();

        $unit = $length->getUnit();

        if ($n === '0' || $unit === false) {

            return new HTMLPurifier_Length('0', false);

        }

        $state = $dest_state = false;

        foreach (self::$units as $k => $x) {

            if (isset($x[$unit])) {

                $state = $k;

            }

            if (isset($x[$to_unit])) {

                $dest_state = $k;

            }

        }

        if (!$state || !$dest_state) {

            return false;

        }

        // Some calculations about the initial precision of the number;

        // this will be useful when we need to do final rounding.

        $sigfigs = $this->getSigFigs($n);

        if ($sigfigs < $this->outputPrecision) {

            $sigfigs = $this->outputPrecision;

        }

        // BCMath's internal precision deals only with decimals. Use

        // our default if the initial number has no decimals, or increase

        // it by how ever many decimals, thus, the number of guard digits

        // will always be greater than or equal to internalPrecision.

        $log = (int)floor(log(abs($n), 10));

        $cp = ($log < 0) ? $this->internalPrecision - $log : $this->internalPrecision; // internal precision

        for ($i = 0; $i < 2; $i++) {

            // Determine what unit IN THIS SYSTEM we need to convert to

            if ($dest_state === $state) {

                // Simple conversion

                $dest_unit = $to_unit;

            } else {

                // Convert to the smallest unit, pending a system shift

                $dest_unit = self::$units[$state][$dest_state][0];

            }

            // Do the conversion if necessary

            if ($dest_unit !== $unit) {

                $factor = $this->div(self::$units[$state][$unit], self::$units[$state][$dest_unit], $cp);

                $n = $this->mul($n, $factor, $cp);

                $unit = $dest_unit;

            }

            // Output was zero, so bail out early. Shouldn't ever happen.

            if ($n === '') {

                $n = '0';

                $unit = $to_unit;

                break;

            }

            // It was a simple conversion, so bail out

            if ($dest_state === $state) {

                break;

            }

            if ($i !== 0) {

                // Conversion failed! Apparently, the system we forwarded

                // to didn't have this unit. This should never happen!

                return false;

            }

            // Pre-condition: $i == 0

            // Perform conversion to next system of units

            $n = $this->mul($n, self::$units[$state][$dest_state][1], $cp);

            $unit = self::$units[$state][$dest_state][2];

            $state = $dest_state;

            // One more loop around to convert the unit in the new system.

        }

        // Post-condition: $unit == $to_unit

        if ($unit !== $to_unit) {

            return false;

        }

        // Useful for debugging:

        //echo "<pre>n";

        //echo "$n\nsigfigs = $sigfigs\nnew_log = $new_log\nlog = $log\nrp = $rp\n</pre>\n";

        $n = $this->round($n, $sigfigs);

        if (strpos($n, '.') !== false) {

            $n = rtrim($n, '0');

        }

        $n = rtrim($n, '.');

        return new HTMLPurifier_Length($n, $unit);

    }

    /**

     * Returns the number of significant figures in a string number.

     * @param string $n Decimal number

     * @return int number of sigfigs

     */

    public function getSigFigs($n)

    {

        $n = ltrim($n, '0+-');

        $dp = strpos($n, '.'); // decimal position

        if ($dp === false) {

            $sigfigs = strlen(rtrim($n, '0'));

        } else {

            $sigfigs = strlen(ltrim($n, '0.')); // eliminate extra decimal character

            if ($dp !== 0) {

                $sigfigs--;

            }

        }

        return $sigfigs;

    }

    /**

     * Adds two numbers, using arbitrary precision when available.

     * @param string $s1

     * @param string $s2

     * @param int $scale

     * @return string

     */

    private function add($s1, $s2, $scale)

    {

        if ($this->bcmath) {

            return bcadd($s1, $s2, $scale);

        } else {

            return $this->scale((float)$s1 + (float)$s2, $scale);

        }

    }

    /**

     * Multiples two numbers, using arbitrary precision when available.

     * @param string $s1

     * @param string $s2

     * @param int $scale

     * @return string

     */

    private function mul($s1, $s2, $scale)

    {

        if ($this->bcmath) {

            return bcmul($s1, $s2, $scale);

        } else {

            return $this->scale((float)$s1 * (float)$s2, $scale);

        }

    }

    /**

     * Divides two numbers, using arbitrary precision when available.

     * @param string $s1

     * @param string $s2

     * @param int $scale

     * @return string

     */

    private function div($s1, $s2, $scale)

    {

        if ($this->bcmath) {

            return bcdiv($s1, $s2, $scale);

        } else {

            return $this->scale((float)$s1 / (float)$s2, $scale);

        }

    }

    /**

     * Rounds a number according to the number of sigfigs it should have,

     * using arbitrary precision when available.

     * @param float $n

     * @param int $sigfigs

     * @return string

     */

    private function round($n, $sigfigs)

    {

        $new_log = (int)floor(log(abs((float)$n), 10)); // Number of digits left of decimal - 1

        $rp = $sigfigs - $new_log - 1; // Number of decimal places needed

        $neg = $n < 0 ? '-' : ''; // Negative sign

        if ($this->bcmath) {

            if ($rp >= 0) {

                $n = bcadd($n, $neg . '0.' . str_repeat('0', $rp) . '5', $rp + 1);

                $n = bcdiv($n, '1', $rp);

            } else {

                // This algorithm partially depends on the standardized

                // form of numbers that comes out of bcmath.

                $n = bcadd($n, $neg . '5' . str_repeat('0', $new_log - $sigfigs), 0);

                $n = substr($n, 0, $sigfigs + strlen($neg)) . str_repeat('0', $new_log - $sigfigs + 1);

            }

            return $n;

        } else {

            return $this->scale(round((float)$n, $sigfigs - $new_log - 1), $rp + 1);

        }

    }

    /**

     * Scales a float to $scale digits right of decimal point, like BCMath.

     * @param float $r

     * @param int $scale

     * @return string

     */

    private function scale($r, $scale)

    {

        if ($scale < 0) {

            // The f sprintf type doesn't support negative numbers, so we

            // need to cludge things manually. First get the string.

            $r = sprintf('%.0f', (float)$r);

            // Due to floating point precision loss, $r will more than likely

            // look something like 4652999999999.9234. We grab one more digit

            // than we need to precise from $r and then use that to round

            // appropriately.

            $precise = (string)round(substr($r, 0, strlen($r) + $scale), -1);

            // Now we return it, truncating the zero that was rounded off.

            return substr($precise, 0, -1) . str_repeat('0', -$scale + 1);

        }

        return number_format((float)$r, $scale, '.', '');

    }

}

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