Decoder::checkDictionaryCompliance() - Code Metrics - Inspection of "Replaced string comparison with substr_compare()" - s9e/Bencode - Measure and Improve Code Quality continuously with Scrutinizer

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by Josh

created 2021-10-05 23:15 UTC

Decoder::checkDictionaryCompliance() A

↳ Parent: Decoder

Complexity

Conditions	3
Paths	3

Size

Total Lines	10
Code Lines	5

Duplication

Lines	0
Ratio	0 %

Code Coverage

Tests	6
CRAP Score	3

Importance

Changes	2
Bugs	0	Features	0

Metric	Value
cc	3
eloc	5
c	2
b	0
f	0
nc	3
nop	2
dl	0
loc	10
ccs	6
cts	6
cp	1
crap	3
rs	10

<?php declare(strict_types=1);

/**
* @package   s9e\Bencode
* @copyright Copyright (c) 2014-2021 The s9e authors
* @license   http://www.opensource.org/licenses/mit-license.php The MIT License
*/
namespace s9e\Bencode;

use ArrayObject;
use const PHP_INT_MAX, PHP_INT_MIN, false;
use function is_float, str_contains, strcmp, strlen, strspn, substr, substr_compare;
use s9e\Bencode\Exceptions\ComplianceError;
use s9e\Bencode\Exceptions\DecodingException;

class Decoder
{
	/**
	* @var string Bencoded string being decoded
	*/
	protected string $bencoded;

	/**
	* @var int Length of the bencoded string
	*/
	protected int $len;

	/**
	* @var int Safe rightmost boundary
	*/
	protected int $max;

	/**
	* @var int Position of the cursor while decoding
	*/
	protected int $offset = 0;

	public static function decode(string $bencoded): ArrayObject|array|int|string
	{
		$decoder = new static($bencoded);
		$value   = $decoder->decodeAnything();

		$decoder->checkCursorPosition();

		return $value;
	}

	protected function __construct(string $bencoded)
	{
		$this->bencoded = $bencoded;
		$this->len      = strlen($bencoded);

		$this->computeSafeBoundary();
		$this->checkBoundary();
	}

	/**
	* Cast given string as an integer and check for clamping
	*/
	protected function castInteger(string $string, bool $negative): int
	{
		if ($negative)
		{
			$string = "-$string";
			$clamp  = PHP_INT_MIN;
		}
		else
		{
			$clamp = PHP_INT_MAX;
		}

		$value = (int) $string;
		if ($value === $clamp)
		{
			$this->checkIntegerOverflow($string);
		}

		return $value;
	}

	protected function checkBoundary(): void
	{
		if ($this->max < 1)
		{
			throw match (substr($this->bencoded, 0, 1))
			{
				'-', 'e' => new DecodingException('Illegal character',     0),
				''       => new DecodingException('Premature end of data', 0),
				default  => new DecodingException('Premature end of data', $this->len - 1)
			};
		}
	}

	/**
	* Check the cursor's position after decoding is done
	*/
	protected function checkCursorPosition(): void
	{
		if ($this->offset !== $this->len)
		{
			if ($this->offset > $this->len)
			{
				throw new DecodingException('Premature end of data', $this->len - 1);
			}

			$this->complianceError('Superfluous content', $this->offset);
		}
	}

	protected function checkIntegerOverflow(string $str): void
	{
		if (is_float(+$str))
		{
			throw new DecodingException('Integer overflow', $this->offset - 1 - strlen($str));
		}
	}

	protected function complianceError(string $message, int $offset): void
	{
		throw new ComplianceError($message, $offset);
	}

	/**
	* Adjust the rightmost boundary to the last safe character that can start a value
	*
	* Will rewind the boundary to skip the rightmost digits, optionally preceded by "i" or "i-"
	*/
	protected function computeSafeBoundary(): void
	{
		$boundary = $this->len - 1;
		do
		{
			$c = substr($this->bencoded, $boundary, 1);
		}
		while (str_contains('0123456789', $c) && --$boundary >= 0);

		$this->max = match ($c)
		{
			'-'     => $boundary - 2,
			'i'     => $boundary - 1,
			default => $boundary
		};
	}

	protected function decodeAnything(): ArrayObject|array|int|string
	{
		return match ($this->bencoded[$this->offset])
		{
			'i'     => $this->decodeInteger(),
			'd'     => $this->decodeDictionary(),
			'l'     => $this->decodeList(),
			default => $this->decodeString()
		};
	}

	protected function decodeDictionary(): ArrayObject
	{
		$values  = [];
		$lastKey = null;

		++$this->offset;
		while ($this->offset <= $this->max)
		{
			$c = $this->bencoded[$this->offset];
			if ($c === 'e')
			{
				++$this->offset;

				return new ArrayObject($values, ArrayObject::ARRAY_AS_PROPS);
			}

			// Quickly match the most common keys found in dictionaries
			$key = match ($c)
			{
				'4'     => $this->decodeFastString('4:path',   6, 'path'),
				'6'     => $this->decodeFastString('6:length', 8, 'length'),
				default => $this->decodeString()
			};
			if (isset($lastKey) && strcmp($key, $lastKey) <= 0)
			{
				$this->dictionaryComplianceError($key, $lastKey);
			}
			if ($this->offset > $this->max)
			{
				break;
			}
			$values[$key] = $this->decodeAnything();
			$lastKey      = $key;
		}

		throw new DecodingException('Premature end of data', $this->len - 1);
	}

	/**
	* @param string $match Bencoded string to match
	* @param int    $len   Length of the bencoded string
	* @param string $value String value to return if the string matches
	*/
	protected function decodeFastString(string $match, int $len, string $value): string
	{
		if (substr_compare($this->bencoded, $match, $this->offset, $len, false) === 0)
		{
			$this->offset += $len;

			return $value;
		}

		return $this->decodeString();
	}

	protected function decodeInteger(): int
	{
		$negative = ($this->bencoded[++$this->offset] === '-');
		if ($negative && $this->bencoded[++$this->offset] === '0')
		{
			$this->complianceError('Illegal character', $this->offset);
		}

		return $this->castInteger($this->readDigits('e'), $negative);
	}

	protected function decodeList(): array
	{
		++$this->offset;

		$list = [];
		while ($this->offset <= $this->max)
		{
			if ($this->bencoded[$this->offset] === 'e')
			{
				++$this->offset;

				return $list;
			}

			$list[] = $this->decodeAnything();
		}

		throw new DecodingException('Premature end of data', $this->len - 1);
	}

	protected function decodeString(): string
	{
		$len = (int) $this->readDigits(':');
		if ($this->offset + $len >= PHP_INT_MAX)
		{
			throw new DecodingException('String length overflow', $this->offset - 1 - strlen((string) $len));
		}

		$string = substr($this->bencoded, $this->offset, $len);
		$this->offset += $len;

		return $string;
	}

	protected function dictionaryComplianceError(string $key, string $lastKey): void
	{
		// Compute the offset of the start of the string used as key
		$offset = $this->offset - strlen(strlen($key) . ':') - strlen($key);

		$msg = ($key === $lastKey) ? 'Duplicate' : 'Out of order';
		$this->complianceError($msg . " dictionary entry '" . $key . "'", $offset);
	}

	protected function readDigits(string $terminator): string
	{
		// Digits sorted by decreasing frequency as observed on a random sample of torrent files
		$spn = strspn($this->bencoded, '1463720859', $this->offset);
		if (!$spn)
		{
			throw new DecodingException('Illegal character', $this->offset);
		}
		if ($this->bencoded[$this->offset] === '0' && $spn !== 1)
		{
			$this->complianceError('Illegal character', 1 + $this->offset);
		}

		$string = substr($this->bencoded, $this->offset, $spn);

		$this->offset += $spn;
		if ($this->bencoded[$this->offset] !== $terminator)
		{
			throw new DecodingException('Illegal character', $this->offset);
		}
		++$this->offset;

		return $string;
	}
}

1		<?php declare(strict_types=1);
2
3		/**
4		* @package s9e\Bencode
5		* @copyright Copyright (c) 2014-2021 The s9e authors
6		* @license http://www.opensource.org/licenses/mit-license.php The MIT License
7		*/
8		namespace s9e\Bencode;
9
10		use ArrayObject;
11		use const PHP_INT_MAX, PHP_INT_MIN, false;
12		use function is_float, str_contains, strcmp, strlen, strspn, substr, substr_compare;
13		use s9e\Bencode\Exceptions\ComplianceError;
14		use s9e\Bencode\Exceptions\DecodingException;
15
16		class Decoder
17		{
18		/**
19		* @var string Bencoded string being decoded
20		*/
21		protected string $bencoded;
22
23		/**
24		* @var int Length of the bencoded string
25		*/
26		protected int $len;
27
28		/**
29		* @var int Safe rightmost boundary
30		*/
31		protected int $max;
32
33		/**
34		* @var int Position of the cursor while decoding
35		*/
36		protected int $offset = 0;
37
38	83	public static function decode(string $bencoded): ArrayObject\|array\|int\|string
39		{
40	83	$decoder = new static($bencoded);
41	71	$value = $decoder->decodeAnything();
42
43	42	$decoder->checkCursorPosition();
44
45	34	return $value;
46		}
47
48	83	protected function __construct(string $bencoded)
49		{
50	83	$this->bencoded = $bencoded;
51	83	$this->len = strlen($bencoded);
52
53	83	$this->computeSafeBoundary();
54	83	$this->checkBoundary();
55	71	}
56
57		/**
58		* Cast given string as an integer and check for clamping
59		*/
60	25	protected function castInteger(string $string, bool $negative): int
61		{
62	25	if ($negative)
63		{
64	4	$string = "-$string";
65	4	$clamp = PHP_INT_MIN;
66		}
67		else
68		{
69	21	$clamp = PHP_INT_MAX;
70		}
71
72	25	$value = (int) $string;
73	25	if ($value === $clamp)
74		{
75	4	$this->checkIntegerOverflow($string);
76		}
77
78	23	return $value;
79		}
80
81	83	protected function checkBoundary(): void
82		{
83	83	if ($this->max < 1)
84		{
85	12	throw match (substr($this->bencoded, 0, 1))
86		{
87	2	'-', 'e' => new DecodingException('Illegal character', 0),
88	1	'' => new DecodingException('Premature end of data', 0),
89	9	default => new DecodingException('Premature end of data', $this->len - 1)
90		};
91		}
92	71	}
93
94		/**
95		* Check the cursor's position after decoding is done
96		*/
97	42	protected function checkCursorPosition(): void
98		{
99	42	if ($this->offset !== $this->len)
100		{
101	11	if ($this->offset > $this->len)
102		{
103	3	throw new DecodingException('Premature end of data', $this->len - 1);
104		}
105
106	8	$this->complianceError('Superfluous content', $this->offset);
107		}
108	34	}
109
110	4	protected function checkIntegerOverflow(string $str): void
111		{
112	4	if (is_float(+$str))
113		{
114	2	throw new DecodingException('Integer overflow', $this->offset - 1 - strlen($str));
115		}
116	2	}
117
118	13	protected function complianceError(string $message, int $offset): void
119		{
120	13	throw new ComplianceError($message, $offset);
121		}
122
123		/**
124		* Adjust the rightmost boundary to the last safe character that can start a value
125		*
126		* Will rewind the boundary to skip the rightmost digits, optionally preceded by "i" or "i-"
127		*/
128	83	protected function computeSafeBoundary(): void
129		{
130	83	$boundary = $this->len - 1;
131		do
132		{
133	83	$c = substr($this->bencoded, $boundary, 1);
134		}
135	83	while (str_contains('0123456789', $c) && --$boundary >= 0);
136
137	83	$this->max = match ($c)
138		{
139	8	'-' => $boundary - 2,
140	7	'i' => $boundary - 1,
141	68	default => $boundary
142		};
143	83	}
144
145	71	protected function decodeAnything(): ArrayObject\|array\|int\|string
146		{
147	71	return match ($this->bencoded[$this->offset])
148		{
149	31	'i' => $this->decodeInteger(),
150	21	'd' => $this->decodeDictionary(),
151	16	'l' => $this->decodeList(),
152	58	default => $this->decodeString()
153		};
154		}
155
156	21	protected function decodeDictionary(): ArrayObject
157		{
158	21	$values = [];
159	21	$lastKey = null;
160
161	21	++$this->offset;
162	21	while ($this->offset <= $this->max)
163		{
164	21	$c = $this->bencoded[$this->offset];
165	21	if ($c === 'e')
166		{
167	12	++$this->offset;
168
169	12	return new ArrayObject($values, ArrayObject::ARRAY_AS_PROPS);
170		}
171
172		// Quickly match the most common keys found in dictionaries
173	20	$key = match ($c)
174		{
175	3	'4' => $this->decodeFastString('4:path', 6, 'path'),
176	1	'6' => $this->decodeFastString('6:length', 8, 'length'),
177	17	default => $this->decodeString()
178		};
179	19	if (isset($lastKey) && strcmp($key, $lastKey) <= 0)
180		{
181	8	$this->dictionaryComplianceError($key, $lastKey);
182		}
183	19	if ($this->offset > $this->max)
184		{
185	1	break;
186		}
187	18	$values[$key] = $this->decodeAnything();
188	15	$lastKey = $key;
189		}
190
191	1	throw new DecodingException('Premature end of data', $this->len - 1);
192		}
193
194		/**
195		* @param string $match Bencoded string to match
196		* @param int $len Length of the bencoded string
197		* @param string $value String value to return if the string matches
198		*/
199	3	protected function decodeFastString(string $match, int $len, string $value): string
200		{
201	3	if (substr_compare($this->bencoded, $match, $this->offset, $len, false) === 0)
202		{
203	1	$this->offset += $len;
204
205	1	return $value;
206		}
207
208	3	return $this->decodeString();
209		}
210
211	31	protected function decodeInteger(): int
212		{
213	31	$negative = ($this->bencoded[++$this->offset] === '-');
214	31	if ($negative && $this->bencoded[++$this->offset] === '0')
215		{
216	2	$this->complianceError('Illegal character', $this->offset);
217		}
218
219	30	return $this->castInteger($this->readDigits('e'), $negative);
220		}
221
222	16	protected function decodeList(): array
223		{
224	16	++$this->offset;
225
226	16	$list = [];
227	16	while ($this->offset <= $this->max)
228		{
229	15	if ($this->bencoded[$this->offset] === 'e')
230		{
231	9	++$this->offset;
232
233	9	return $list;
234		}
235
236	12	$list[] = $this->decodeAnything();
237		}
238
239	5	throw new DecodingException('Premature end of data', $this->len - 1);
240		}
241
242	46	protected function decodeString(): string
243		{
244	46	$len = (int) $this->readDigits(':');
245	38	if ($this->offset + $len >= PHP_INT_MAX)
246		{
247	1	throw new DecodingException('String length overflow', $this->offset - 1 - strlen((string) $len));
248		}
249
250	37	$string = substr($this->bencoded, $this->offset, $len);
251	37	$this->offset += $len;
252
253	37	return $string;
254		}
255
256	4	protected function dictionaryComplianceError(string $key, string $lastKey): void
257		{
258		// Compute the offset of the start of the string used as key
259	4	$offset = $this->offset - strlen(strlen($key) . ':') - strlen($key);
260
261	4	$msg = ($key === $lastKey) ? 'Duplicate' : 'Out of order';
262	4	$this->complianceError($msg . " dictionary entry '" . $key . "'", $offset);
263		}
264
265	63	protected function readDigits(string $terminator): string
266		{
267		// Digits sorted by decreasing frequency as observed on a random sample of torrent files
268	63	$spn = strspn($this->bencoded, '1463720859', $this->offset);
269	63	if (!$spn)
270		{
271	7	throw new DecodingException('Illegal character', $this->offset);
272		}
273	58	if ($this->bencoded[$this->offset] === '0' && $spn !== 1)
274		{
275	6	$this->complianceError('Illegal character', 1 + $this->offset);
276		}
277
278	55	$string = substr($this->bencoded, $this->offset, $spn);
279
280	55	$this->offset += $spn;
281	55	if ($this->bencoded[$this->offset] !== $terminator)
282		{
283	5	throw new DecodingException('Illegal character', $this->offset);
284		}
285	50	++$this->offset;
286
287	50	return $string;
288		}
289		}

s9e / Bencode

Push — master ( 94dc81...d2c9a0 )

Decoder::checkDictionaryCompliance() A

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