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<?php
/**
* This file is part of FPDI
*
* @package setasign\Fpdi
* @copyright Copyright (c) 2020 Setasign GmbH & Co. KG (https://www.setasign.com)
* @license http://opensource.org/licenses/mit-license The MIT License
*/
namespace setasign\Fpdi\PdfParser\Filter;
/**
* Class for handling ASCII base-85 encoded data
*/
class Ascii85 implements FilterInterface
{
/**
* Decode ASCII85 encoded string.
*
* @param string $data The input string
* @return string
* @throws Ascii85Exception
*/
public function decode($data)
{
$out = '';
$state = 0;
$chn = null;
$data = \preg_replace('/\s/', '', $data);
$l = \strlen($data);
/** @noinspection ForeachInvariantsInspection */
for ($k = 0; $k < $l; ++$k) {
$ch = \ord($data[$k]) & 0xff;
//Start <~
if ($k === 0 && $ch === 60 && isset($data[$k + 1]) && (\ord($data[$k + 1]) & 0xFF) === 126) {
$k++;
continue;
}
//End ~>
if ($ch === 126 && isset($data[$k + 1]) && (\ord($data[$k + 1]) & 0xFF) === 62) {
break;
}
if ($ch === 122 /* z */ && $state === 0) {
$out .= \chr(0) . \chr(0) . \chr(0) . \chr(0);
continue;
}
if ($ch < 33 /* ! */ || $ch > 117 /* u */) {
throw new Ascii85Exception(
'Illegal character found while ASCII85 decode.',
Ascii85Exception::ILLEGAL_CHAR_FOUND
);
}
$chn[$state] = $ch - 33;/* ! */
$state++;
if ($state === 5) {
$state = 0;
$r = 0;
for ($j = 0; $j < 5; ++$j) {
/** @noinspection UnnecessaryCastingInspection */
$r = (int)($r * 85 + $chn[$j]);
}
$out .= \chr($r >> 24)
. \chr($r >> 16)
. \chr($r >> 8)
. \chr($r);
}
}
if ($state === 1) {
throw new Ascii85Exception(
'Illegal length while ASCII85 decode.',
Ascii85Exception::ILLEGAL_LENGTH
);
}
if ($state === 2) {
$r = $chn[0] * 85 * 85 * 85 * 85 + ($chn[1] + 1) * 85 * 85 * 85;
$out .= \chr($r >> 24);
} elseif ($state === 3) {
$r = $chn[0] * 85 * 85 * 85 * 85 + $chn[1] * 85 * 85 * 85 + ($chn[2] + 1) * 85 * 85;
$out .= \chr($r >> 24);
$out .= \chr($r >> 16);
} elseif ($state === 4) {
$r = $chn[0] * 85 * 85 * 85 * 85 + $chn[1] * 85 * 85 * 85 + $chn[2] * 85 * 85 + ($chn[3] + 1) * 85;
$out .= \chr($r >> 24);
$out .= \chr($r >> 16);
$out .= \chr($r >> 8);
}
return $out;
}
}
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