FilterHelper::decodeFilter() - Code Metrics - Inspection of "Allow for CRC23 checksum gzuncompress()" - smalot/pdfparser - Measure and Improve Code Quality continuously with Scrutinizer

Test Failed

Pull Request — master (#622)

unknown

created 2023-07-31 17:32 UTC

FilterHelper::decodeFilter() B

↳ Parent: FilterHelper

Complexity

Conditions	11
Paths	11

Size

Total Lines	30
Code Lines	23

Duplication

Lines	0
Ratio	0 %

Code Coverage

Tests	21
CRAP Score	11.0795

Importance

Changes	1
Bugs	0	Features	1

Metric	Value
cc	11
eloc	23
c	1
b	0
f	1
nc	11
nop	3
dl	0
loc	30
ccs	21
cts	23
cp	0.913
crap	11.0795
rs	7.3166

How to fix Complexity

<?php

/**
 * This file is based on code of tecnickcom/TCPDF PDF library.
 *
 * Original author Nicola Asuni ([email protected]) and
 * contributors (https://github.com/tecnickcom/TCPDF/graphs/contributors).
 *
 * @see https://github.com/tecnickcom/TCPDF
 *
 * Original code was licensed on the terms of the LGPL v3.
 *
 * ------------------------------------------------------------------------------
 *
 * @file This file is part of the PdfParser library.
 *
 * @author  Konrad Abicht <[email protected]>
 *
 * @date    2020-01-06
 *
 * @license LGPLv3
 *
 * @url     <https://github.com/smalot/pdfparser>
 *
 *  PdfParser is a pdf library written in PHP, extraction oriented.
 *  Copyright (C) 2017 - Sébastien MALOT <[email protected]>
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU Lesser General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with this program.
 *  If not, see <http://www.pdfparser.org/sites/default/LICENSE.txt>.
 */

namespace Smalot\PdfParser\RawData;

class FilterHelper
{
    protected $availableFilters = ['ASCIIHexDecode', 'ASCII85Decode', 'LZWDecode', 'FlateDecode', 'RunLengthDecode'];

    /**
     * Decode data using the specified filter type.
     *
     * @param string $filter Filter name
     * @param string $data   Data to decode
     *
     * @return string Decoded data string
     *
     * @throws \Exception if a certain decode function is not implemented yet
     */
    public function decodeFilter(string $filter, string $data, int $decodeMemoryLimit = 0): string
    {
        switch ($filter) {
            case 'ASCIIHexDecode':
                return $this->decodeFilterASCIIHexDecode($data);

            case 'ASCII85Decode':
                return $this->decodeFilterASCII85Decode($data);

            case 'LZWDecode':
                return $this->decodeFilterLZWDecode($data);

            case 'FlateDecode':
                return $this->decodeFilterFlateDecode($data, $decodeMemoryLimit);


            case 'RunLengthDecode':
                return $this->decodeFilterRunLengthDecode($data);

            case 'CCITTFaxDecode':
                throw new \Exception('Decode CCITTFaxDecode not implemented yet.');
            case 'JBIG2Decode':
                throw new \Exception('Decode JBIG2Decode not implemented yet.');
            case 'DCTDecode':
                throw new \Exception('Decode DCTDecode not implemented yet.');
            case 'JPXDecode':
                throw new \Exception('Decode JPXDecode not implemented yet.');
            case 'Crypt':
                throw new \Exception('Decode Crypt not implemented yet.');
            default:
                return $data;
        }
    }

    /**
     * ASCIIHexDecode
     *
     * Decodes data encoded in an ASCII hexadecimal representation, reproducing the original binary data.
     *
     * @param string $data Data to decode
     *
     * @return string data string
     *
     * @throws \Exception
     */
    protected function decodeFilterASCIIHexDecode(string $data): string
    {
        // all white-space characters shall be ignored
        $data = preg_replace('/[\s]/', '', $data);
        // check for EOD character: GREATER-THAN SIGN (3Eh)
        $eod = strpos($data, '>');
        if (false !== $eod) {
            // remove EOD and extra data (if any)
            $data = substr($data, 0, $eod);
            $eod = true;
        }
        // get data length
        $data_length = \strlen($data);
        if (0 != ($data_length % 2)) {
            // odd number of hexadecimal digits
            if ($eod) {
                // EOD shall behave as if a 0 (zero) followed the last digit
                $data = substr($data, 0, -1).'0'.substr($data, -1);
            } else {
                throw new \Exception('decodeFilterASCIIHexDecode: invalid code');
            }
        }
        // check for invalid characters
        if (preg_match('/[^a-fA-F\d]/', $data) > 0) {
            throw new \Exception('decodeFilterASCIIHexDecode: invalid code');
        }
        // get one byte of binary data for each pair of ASCII hexadecimal digits
        $decoded = pack('H*', $data);

        return $decoded;
    }

    /**
     * ASCII85Decode
     *
     * Decodes data encoded in an ASCII base-85 representation, reproducing the original binary data.
     *
     * @param string $data Data to decode
     *
     * @return string data string
     *
     * @throws \Exception
     */
    protected function decodeFilterASCII85Decode(string $data): string
    {
        // initialize string to return
        $decoded = '';
        // all white-space characters shall be ignored
        $data = preg_replace('/[\s]/', '', $data);
        // remove start sequence 2-character sequence <~ (3Ch)(7Eh)
        if (0 === strpos($data, '<~')) {
            // remove EOD and extra data (if any)
            $data = substr($data, 2);
        }
        // check for EOD: 2-character sequence ~> (7Eh)(3Eh)
        $eod = strpos($data, '~>');
        if (\strlen($data) - 2 === $eod) {
            // remove EOD and extra data (if any)
            $data = substr($data, 0, $eod);
        }
        // data length
        $data_length = \strlen($data);
        // check for invalid characters
        if (preg_match('/[^\x21-\x75,\x74]/', $data) > 0) {
            throw new \Exception('decodeFilterASCII85Decode: invalid code');
        }
        // z sequence
        $zseq = \chr(0).\chr(0).\chr(0).\chr(0);
        // position inside a group of 4 bytes (0-3)
        $group_pos = 0;
        $tuple = 0;
        $pow85 = [85 * 85 * 85 * 85, 85 * 85 * 85, 85 * 85, 85, 1];

        // for each byte
        for ($i = 0; $i < $data_length; ++$i) {
            // get char value
            $char = \ord($data[$i]);
            if (122 == $char) { // 'z'
                if (0 == $group_pos) {
                    $decoded .= $zseq;
                } else {
                    throw new \Exception('decodeFilterASCII85Decode: invalid code');
                }
            } else {
                // the value represented by a group of 5 characters should never be greater than 2^32 - 1
                $tuple += (($char - 33) * $pow85[$group_pos]);
                if (4 == $group_pos) {
                    $decoded .= \chr($tuple >> 24).\chr($tuple >> 16).\chr($tuple >> 8).\chr($tuple);
                    $tuple = 0;
                    $group_pos = 0;
                } else {
                    ++$group_pos;
                }
            }
        }
        if ($group_pos > 1) {
            $tuple += $pow85[$group_pos - 1];
        }
        // last tuple (if any)
        switch ($group_pos) {
            case 4:
                $decoded .= \chr($tuple >> 24).\chr($tuple >> 16).\chr($tuple >> 8);
                break;

            case 3:
                $decoded .= \chr($tuple >> 24).\chr($tuple >> 16);
                break;

            case 2:
                $decoded .= \chr($tuple >> 24);
                break;

            case 1:
                throw new \Exception('decodeFilterASCII85Decode: invalid code');
        }

        return $decoded;
    }

    /**
     * FlateDecode
     *
     * Decompresses data encoded using the zlib/deflate compression method, reproducing the original text or binary data.
     *
     * @param string $data              Data to decode
     * @param int    $decodeMemoryLimit Memory limit on deflation
     *
     * @return string data string
     *
     * @throws \Exception
     */
    protected function decodeFilterFlateDecode(string $data, int $decodeMemoryLimit): ?string
    {
        /*
         * gzuncompress may throw a not catchable E_WARNING in case of an error (like $data is empty)
         * the following set_error_handler changes an E_WARNING to an E_ERROR, which is catchable.
         */
        set_error_handler(function ($errNo, $errStr) {
            if (\E_WARNING === $errNo) {
                throw new \Exception($errStr);
            } else {
                // fallback to default php error handler
                return false;
            }
        });

        $decoded = null;


        // initialize string to return
        try {
            $decoded = gzuncompress($data, $decodeMemoryLimit);
            if (false === $decoded) {
                throw new \Exception('decodeFilterFlateDecode: invalid code');
            }
        } catch (\Exception $e) {
            try {
                // If gzuncompress() failed with a data error, try again
                // allowing for a CRC32 checksum instead of Adler-32.
                // See: https://www.php.net/manual/en/function.gzuncompress.php#79042
                // Issue: https://github.com/smalot/pdfparser/issues/592
                $crc32 = @tempnam('/tmp', 'gz_fix');
                if (false != $crc32) {

                    file_put_contents($crc32, "\x1f\x8b\x08\x00\x00\x00\x00\x00".$data);
                    $decoded = file_get_contents('compress.zlib://'.$crc32);
                    unlink($crc32);
                }

                // If the decoded string is empty, that means decoding failed.
                if (empty($decoded)) {
                    throw $e;
                }
            } catch (\Exception $e) {
                throw $e;
            }
        } finally {
            // Restore old handler just in case it was customized outside of PDFParser.
            restore_error_handler();
        }

        return $decoded;
    }

    /**
     * LZWDecode
     *
     * Decompresses data encoded using the LZW (Lempel-Ziv-Welch) adaptive compression method, reproducing the original text or binary data.
     *
     * @param string $data Data to decode
     *
     * @return string Data string
     */
    protected function decodeFilterLZWDecode(string $data): string
    {
        // initialize string to return
        $decoded = '';
        // data length
        $data_length = \strlen($data);
        // convert string to binary string
        $bitstring = '';
        for ($i = 0; $i < $data_length; ++$i) {
            $bitstring .= sprintf('%08b', \ord($data[$i]));
        }
        // get the number of bits
        $data_length = \strlen($bitstring);
        // initialize code length in bits
        $bitlen = 9;
        // initialize dictionary index
        $dix = 258;
        // initialize the dictionary (with the first 256 entries).
        $dictionary = [];
        for ($i = 0; $i < 256; ++$i) {
            $dictionary[$i] = \chr($i);
        }
        // previous val
        $prev_index = 0;
        // while we encounter EOD marker (257), read code_length bits
        while (($data_length > 0) && (257 != ($index = bindec(substr($bitstring, 0, $bitlen))))) {
            // remove read bits from string
            $bitstring = substr($bitstring, $bitlen);
            // update number of bits
            $data_length -= $bitlen;
            if (256 == $index) { // clear-table marker
                // reset code length in bits
                $bitlen = 9;
                // reset dictionary index
                $dix = 258;
                $prev_index = 256;
                // reset the dictionary (with the first 256 entries).
                $dictionary = [];
                for ($i = 0; $i < 256; ++$i) {
                    $dictionary[$i] = \chr($i);
                }
            } elseif (256 == $prev_index) {
                // first entry
                $decoded .= $dictionary[$index];
                $prev_index = $index;
            } else {
                // check if index exist in the dictionary
                if ($index < $dix) {
                    // index exist on dictionary
                    $decoded .= $dictionary[$index];
                    $dic_val = $dictionary[$prev_index].$dictionary[$index][0];
                    // store current index
                    $prev_index = $index;
                } else {
                    // index do not exist on dictionary
                    $dic_val = $dictionary[$prev_index].$dictionary[$prev_index][0];
                    $decoded .= $dic_val;
                }
                // update dictionary
                $dictionary[$dix] = $dic_val;
                ++$dix;
                // change bit length by case
                if (2047 == $dix) {
                    $bitlen = 12;
                } elseif (1023 == $dix) {
                    $bitlen = 11;
                } elseif (511 == $dix) {
                    $bitlen = 10;
                }
            }
        }

        return $decoded;
    }

    /**
     * RunLengthDecode
     *
     * Decompresses data encoded using a byte-oriented run-length encoding algorithm.
     *
     * @param string $data Data to decode
     */
    protected function decodeFilterRunLengthDecode(string $data): string
    {
        // initialize string to return
        $decoded = '';
        // data length
        $data_length = \strlen($data);
        $i = 0;
        while ($i < $data_length) {
            // get current byte value
            $byte = \ord($data[$i]);
            if (128 == $byte) {
                // a length value of 128 denote EOD
                break;
            } elseif ($byte < 128) {
                // if the length byte is in the range 0 to 127
                // the following length + 1 (1 to 128) bytes shall be copied literally during decompression
                $decoded .= substr($data, $i + 1, $byte + 1);
                // move to next block
                $i += ($byte + 2);
            } else {
                // if length is in the range 129 to 255,
                // the following single byte shall be copied 257 - length (2 to 128) times during decompression
                $decoded .= str_repeat($data[$i + 1], 257 - $byte);
                // move to next block
                $i += 2;
            }
        }

        return $decoded;
    }

    /**
     * @return array list of available filters
     */
    public function getAvailableFilters(): array
    {
        return $this->availableFilters;
    }
}


1		<?php
2
3		/**
4		* This file is based on code of tecnickcom/TCPDF PDF library.
5		*
6		* Original author Nicola Asuni ([email protected]) and
7		* contributors (https://github.com/tecnickcom/TCPDF/graphs/contributors).
8		*
9		* @see https://github.com/tecnickcom/TCPDF
10		*
11		* Original code was licensed on the terms of the LGPL v3.
12		*
13		* ------------------------------------------------------------------------------
14		*
15		* @file This file is part of the PdfParser library.
16		*
17		* @author Konrad Abicht <[email protected]>
18		*
19		* @date 2020-01-06
20		*
21		* @license LGPLv3
22		*
23		* @url <https://github.com/smalot/pdfparser>
24		*
25		* PdfParser is a pdf library written in PHP, extraction oriented.
26		* Copyright (C) 2017 - Sébastien MALOT <[email protected]>
27		*
28		* This program is free software: you can redistribute it and/or modify
29		* it under the terms of the GNU Lesser General Public License as published by
30		* the Free Software Foundation, either version 3 of the License, or
31		* (at your option) any later version.
32		*
33		* This program is distributed in the hope that it will be useful,
34		* but WITHOUT ANY WARRANTY; without even the implied warranty of
35		* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
36		* GNU Lesser General Public License for more details.
37		*
38		* You should have received a copy of the GNU Lesser General Public License
39		* along with this program.
40		* If not, see <http://www.pdfparser.org/sites/default/LICENSE.txt>.
41		*/
42
43		namespace Smalot\PdfParser\RawData;
44
45		class FilterHelper
46		{
47		protected $availableFilters = ['ASCIIHexDecode', 'ASCII85Decode', 'LZWDecode', 'FlateDecode', 'RunLengthDecode'];
48
49		/**
50		* Decode data using the specified filter type.
51		*
52		* @param string $filter Filter name
53		* @param string $data Data to decode
54		*
55		* @return string Decoded data string
56		*
57		* @throws \Exception if a certain decode function is not implemented yet
58		*/
59	52	public function decodeFilter(string $filter, string $data, int $decodeMemoryLimit = 0): string
60		{
61	52	switch ($filter) {
62	52	case 'ASCIIHexDecode':
63	1	return $this->decodeFilterASCIIHexDecode($data);
64
65	51	case 'ASCII85Decode':
66	1	return $this->decodeFilterASCII85Decode($data);
67
68	50	case 'LZWDecode':
69		return $this->decodeFilterLZWDecode($data);
70
71	50	case 'FlateDecode':
72	44	return $this->decodeFilterFlateDecode($data, $decodeMemoryLimit);
		0 ignored issues – show Bug Best Practice introduced 2023-07-31 17:33 UTC by Report Bug Copy Issue Report The expression `return $this->decodeFilt...ta, $decodeMemoryLimit)` could return the type `null` which is incompatible with the type-hinted return `string`. Consider adding an additional type-check to rule them out. Loading history...
73
74	6	case 'RunLengthDecode':
75		return $this->decodeFilterRunLengthDecode($data);
76
77	6	case 'CCITTFaxDecode':
78	1	throw new \Exception('Decode CCITTFaxDecode not implemented yet.');
79	5	case 'JBIG2Decode':
80	1	throw new \Exception('Decode JBIG2Decode not implemented yet.');
81	4	case 'DCTDecode':
82	1	throw new \Exception('Decode DCTDecode not implemented yet.');
83	3	case 'JPXDecode':
84	1	throw new \Exception('Decode JPXDecode not implemented yet.');
85	2	case 'Crypt':
86	1	throw new \Exception('Decode Crypt not implemented yet.');
87		default:
88	1	return $data;
89		}
90		}
91
92		/**
93		* ASCIIHexDecode
94		*
95		* Decodes data encoded in an ASCII hexadecimal representation, reproducing the original binary data.
96		*
97		* @param string $data Data to decode
98		*
99		* @return string data string
100		*
101		* @throws \Exception
102		*/
103	1	protected function decodeFilterASCIIHexDecode(string $data): string
104		{
105		// all white-space characters shall be ignored
106	1	$data = preg_replace('/[\s]/', '', $data);
107		// check for EOD character: GREATER-THAN SIGN (3Eh)
108	1	$eod = strpos($data, '>');
109	1	if (false !== $eod) {
110		// remove EOD and extra data (if any)
111		$data = substr($data, 0, $eod);
112		$eod = true;
113		}
114		// get data length
115	1	$data_length = \strlen($data);
116	1	if (0 != ($data_length % 2)) {
117		// odd number of hexadecimal digits
118		if ($eod) {
119		// EOD shall behave as if a 0 (zero) followed the last digit
120		$data = substr($data, 0, -1).'0'.substr($data, -1);
121		} else {
122		throw new \Exception('decodeFilterASCIIHexDecode: invalid code');
123		}
124		}
125		// check for invalid characters
126	1	if (preg_match('/[^a-fA-F\d]/', $data) > 0) {
127		throw new \Exception('decodeFilterASCIIHexDecode: invalid code');
128		}
129		// get one byte of binary data for each pair of ASCII hexadecimal digits
130	1	$decoded = pack('H*', $data);
131
132	1	return $decoded;
133		}
134
135		/**
136		* ASCII85Decode
137		*
138		* Decodes data encoded in an ASCII base-85 representation, reproducing the original binary data.
139		*
140		* @param string $data Data to decode
141		*
142		* @return string data string
143		*
144		* @throws \Exception
145		*/
146	1	protected function decodeFilterASCII85Decode(string $data): string
147		{
148		// initialize string to return
149	1	$decoded = '';
150		// all white-space characters shall be ignored
151	1	$data = preg_replace('/[\s]/', '', $data);
152		// remove start sequence 2-character sequence <~ (3Ch)(7Eh)
153	1	if (0 === strpos($data, '<~')) {
154		// remove EOD and extra data (if any)
155		$data = substr($data, 2);
156		}
157		// check for EOD: 2-character sequence ~> (7Eh)(3Eh)
158	1	$eod = strpos($data, '~>');
159	1	if (\strlen($data) - 2 === $eod) {
160		// remove EOD and extra data (if any)
161		$data = substr($data, 0, $eod);
162		}
163		// data length
164	1	$data_length = \strlen($data);
165		// check for invalid characters
166	1	if (preg_match('/[^\x21-\x75,\x74]/', $data) > 0) {
167		throw new \Exception('decodeFilterASCII85Decode: invalid code');
168		}
169		// z sequence
170	1	$zseq = \chr(0).\chr(0).\chr(0).\chr(0);
171		// position inside a group of 4 bytes (0-3)
172	1	$group_pos = 0;
173	1	$tuple = 0;
174	1	$pow85 = [85 * 85 * 85 * 85, 85 * 85 * 85, 85 * 85, 85, 1];
175
176		// for each byte
177	1	for ($i = 0; $i < $data_length; ++$i) {
178		// get char value
179	1	$char = \ord($data[$i]);
180	1	if (122 == $char) { // 'z'
181		if (0 == $group_pos) {
182		$decoded .= $zseq;
183		} else {
184		throw new \Exception('decodeFilterASCII85Decode: invalid code');
185		}
186		} else {
187		// the value represented by a group of 5 characters should never be greater than 2^32 - 1
188	1	$tuple += (($char - 33) * $pow85[$group_pos]);
189	1	if (4 == $group_pos) {
190	1	$decoded .= \chr($tuple >> 24).\chr($tuple >> 16).\chr($tuple >> 8).\chr($tuple);
191	1	$tuple = 0;
192	1	$group_pos = 0;
193		} else {
194	1	++$group_pos;
195		}
196		}
197		}
198	1	if ($group_pos > 1) {
199	1	$tuple += $pow85[$group_pos - 1];
200		}
201		// last tuple (if any)
202		switch ($group_pos) {
203	1	case 4:
204		$decoded .= \chr($tuple >> 24).\chr($tuple >> 16).\chr($tuple >> 8);
205		break;
206
207	1	case 3:
208		$decoded .= \chr($tuple >> 24).\chr($tuple >> 16);
209		break;
210
211	1	case 2:
212	1	$decoded .= \chr($tuple >> 24);
213	1	break;
214
215		case 1:
216		throw new \Exception('decodeFilterASCII85Decode: invalid code');
217		}
218
219	1	return $decoded;
220		}
221
222		/**
223		* FlateDecode
224		*
225		* Decompresses data encoded using the zlib/deflate compression method, reproducing the original text or binary data.
226		*
227		* @param string $data Data to decode
228		* @param int $decodeMemoryLimit Memory limit on deflation
229		*
230		* @return string data string
231		*
232		* @throws \Exception
233		*/
234	44	protected function decodeFilterFlateDecode(string $data, int $decodeMemoryLimit): ?string
235		{
236		/*
237		* gzuncompress may throw a not catchable E_WARNING in case of an error (like $data is empty)
238		* the following set_error_handler changes an E_WARNING to an E_ERROR, which is catchable.
239		*/
240		set_error_handler(function ($errNo, $errStr) {
241	2	if (\E_WARNING === $errNo) {
242	2	throw new \Exception($errStr);
243		} else {
244		// fallback to default php error handler
245		return false;
246		}
247	44	});
248
249	44	$decoded = null;
		0 ignored issues – show Unused Code introduced 2021-07-13 16:36 UTC by Report Bug Copy Issue Report The assignment to `$decoded` is dead and can be removed. Loading history...
250
251		// initialize string to return
252		try {
253	44	$decoded = gzuncompress($data, $decodeMemoryLimit);
254	42	if (false === $decoded) {
255	42	throw new \Exception('decodeFilterFlateDecode: invalid code');
256		}
257	2	} catch (\Exception $e) {
258	2	try {
259	42	// If gzuncompress() failed with a data error, try again
260		// allowing for a CRC32 checksum instead of Adler-32.
261	44	// See: https://www.php.net/manual/en/function.gzuncompress.php#79042
262		// Issue: https://github.com/smalot/pdfparser/issues/592
263		$crc32 = @tempnam('/tmp', 'gz_fix');
264	42	if (false != $crc32) {
		0 ignored issues – show Bug introduced 2023-07-31 17:33 UTC by Report Bug Copy Issue Report It seems like you are loosely comparing `$crc32` of type `false\|string` against `false`; this is ambiguous if the string can be empty. Consider using a strict comparison `!==` instead. Loading history...
265		file_put_contents($crc32, "\x1f\x8b\x08\x00\x00\x00\x00\x00".$data);
266		$decoded = file_get_contents('compress.zlib://'.$crc32);
267		unlink($crc32);
268		}
269
270		// If the decoded string is empty, that means decoding failed.
271		if (empty($decoded)) {
272		throw $e;
273		}
274		} catch (\Exception $e) {
275		throw $e;
276		}
277		} finally {
278		// Restore old handler just in case it was customized outside of PDFParser.
279		restore_error_handler();
280		}
281
282		return $decoded;
283		}
284
285		/**
286		* LZWDecode
287		*
288		* Decompresses data encoded using the LZW (Lempel-Ziv-Welch) adaptive compression method, reproducing the original text or binary data.
289		*
290		* @param string $data Data to decode
291		*
292		* @return string Data string
293		*/
294		protected function decodeFilterLZWDecode(string $data): string
295		{
296		// initialize string to return
297		$decoded = '';
298		// data length
299		$data_length = \strlen($data);
300		// convert string to binary string
301		$bitstring = '';
302		for ($i = 0; $i < $data_length; ++$i) {
303		$bitstring .= sprintf('%08b', \ord($data[$i]));
304		}
305		// get the number of bits
306		$data_length = \strlen($bitstring);
307		// initialize code length in bits
308		$bitlen = 9;
309		// initialize dictionary index
310		$dix = 258;
311		// initialize the dictionary (with the first 256 entries).
312		$dictionary = [];
313		for ($i = 0; $i < 256; ++$i) {
314		$dictionary[$i] = \chr($i);
315		}
316		// previous val
317		$prev_index = 0;
318		// while we encounter EOD marker (257), read code_length bits
319		while (($data_length > 0) && (257 != ($index = bindec(substr($bitstring, 0, $bitlen))))) {
320		// remove read bits from string
321		$bitstring = substr($bitstring, $bitlen);
322		// update number of bits
323		$data_length -= $bitlen;
324		if (256 == $index) { // clear-table marker
325		// reset code length in bits
326		$bitlen = 9;
327		// reset dictionary index
328		$dix = 258;
329		$prev_index = 256;
330		// reset the dictionary (with the first 256 entries).
331		$dictionary = [];
332		for ($i = 0; $i < 256; ++$i) {
333		$dictionary[$i] = \chr($i);
334		}
335		} elseif (256 == $prev_index) {
336		// first entry
337		$decoded .= $dictionary[$index];
338		$prev_index = $index;
339		} else {
340		// check if index exist in the dictionary
341		if ($index < $dix) {
342		// index exist on dictionary
343		$decoded .= $dictionary[$index];
344		$dic_val = $dictionary[$prev_index].$dictionary[$index][0];
345		// store current index
346		$prev_index = $index;
347		} else {
348		// index do not exist on dictionary
349		$dic_val = $dictionary[$prev_index].$dictionary[$prev_index][0];
350		$decoded .= $dic_val;
351		}
352		// update dictionary
353		$dictionary[$dix] = $dic_val;
354		++$dix;
355		// change bit length by case
356		if (2047 == $dix) {
357		$bitlen = 12;
358		} elseif (1023 == $dix) {
359		$bitlen = 11;
360		} elseif (511 == $dix) {
361		$bitlen = 10;
362		}
363		}
364		}
365
366		return $decoded;
367		}
368
369		/**
370		* RunLengthDecode
371		*
372		* Decompresses data encoded using a byte-oriented run-length encoding algorithm.
373		*
374		* @param string $data Data to decode
375		*/
376		protected function decodeFilterRunLengthDecode(string $data): string
377		{
378		// initialize string to return
379		$decoded = '';
380		// data length
381		$data_length = \strlen($data);
382		$i = 0;
383		while ($i < $data_length) {
384		// get current byte value
385		$byte = \ord($data[$i]);
386		if (128 == $byte) {
387		// a length value of 128 denote EOD
388		break;
389		} elseif ($byte < 128) {
390		// if the length byte is in the range 0 to 127
391		// the following length + 1 (1 to 128) bytes shall be copied literally during decompression
392	41	$decoded .= substr($data, $i + 1, $byte + 1);
393		// move to next block
394	41	$i += ($byte + 2);
395		} else {
396		// if length is in the range 129 to 255,
397		// the following single byte shall be copied 257 - length (2 to 128) times during decompression
398		$decoded .= str_repeat($data[$i + 1], 257 - $byte);
399		// move to next block
400		$i += 2;
401		}
402		}
403
404		return $decoded;
405		}
406
407		/**
408		* @return array list of available filters
409		*/
410		public function getAvailableFilters(): array
411		{
412		return $this->availableFilters;
413		}
414		}
415

smalot / pdfparser

Pull Request — master (#622)

FilterHelper::decodeFilter() B

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