Decoder::checkCursorPosition() - Code Metrics - Inspection of "WiP" - s9e/Bencode - Measure and Improve Code Quality continuously with Scrutinizer

Passed

Branch — test (3b2ced)

by Josh

created 2021-07-15 20:00 UTC

Decoder::checkCursorPosition() A

↳ Parent: Decoder

Complexity

Conditions	4
Paths	4

Size

Total Lines	14
Code Lines	6

Duplication

Lines	0
Ratio	0 %

Code Coverage

Tests	6
CRAP Score	4.0466

Importance

Changes	2
Bugs	0	Features	0

Metric	Value
cc	4
eloc	6
nc	4
nop	0
dl	0
loc	14
ccs	6
cts	7
cp	0.8571
crap	4.0466
rs	10
c	2
b	0
f	0

<?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 function str_contains, strcmp, strlen, strspn, substr;
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);

		if ($bencoded === '')
		{
			throw new DecodingException('Premature end of data', 0);
		}
		$this->computeSafeBoundary();
	}

	protected function checkBoundary(): void
	{
		if ($this->max < 1)
		{
			throw match ($this->bencoded[0])
			{
				'-', 'e' => new DecodingException('Illegal character', 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 (false)
		{
			die('?');

		}
		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 checkDictionaryCompliance(int $offset, string $key, string $lastKey): void
	{
		$cmp = strcmp($key, $lastKey);
		if ($cmp <= 0)
		{
			$msg = ($cmp === 0) ? 'Duplicate' : 'Out of order';
			$this->complianceError($msg . " dictionary entry '" . $key . "'", $offset);
		}
	}

	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 = $this->bencoded[$boundary];
		}
		while (str_contains('0123456789', $c) && --$boundary >= 0);

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

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

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

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

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

			$offset = $this->offset;
			$key    = $this->decodeString();
			if (isset($lastKey))
			{
				$this->checkDictionaryCompliance($offset, $key, $lastKey);
			}
			if ($this->offset > $this->max)
			{
				break;
			}
			$values[$key] = $this->decodeAnything();
			$lastKey      = $key;
		}

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

	protected function decodeDigits(string $terminator): int
	{
		// Digits sorted by decreasing frequency as observed on a random sample of torrent files
		$spn = strspn($this->bencoded, '4615302879', $this->offset);
		if (!$spn)
		{
			throw new DecodingException('Illegal character', $this->offset);
		}
		if ($this->bencoded[$this->offset] === '0' && $spn !== 1)
		{
			$this->complianceError('Illegal character', 1 + $this->offset);
		}

		// Capture the value and cast it as an integer
		$value = (int) substr($this->bencoded, $this->offset, $spn);

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

		return $value;
	}

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

		$value = $this->decodeDigits('e');

		return ($negative) ? -$value : $value;
	}

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

		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 function str_contains, strcmp, strlen, strspn, substr;
12		use s9e\Bencode\Exceptions\ComplianceError;
13		use s9e\Bencode\Exceptions\DecodingException;
14
15		class Decoder
16		{
17		/**
18		* @var string Bencoded string being decoded
19		*/
20		protected string $bencoded;
21
22		/**
23		* @var int Length of the bencoded string
24		*/
25		protected int $len;
26
27		/**
28		* @var int Safe rightmost boundary
29		*/
30		protected int $max;
31
32		/**
33		* @var int Position of the cursor while decoding
34		*/
35		protected int $offset = 0;
36
37	64	public static function decode(string $bencoded): ArrayObject\|array\|int\|string
38		{
39	64	$decoder = new static($bencoded);
40	53	$value = $decoder->decodeAnything();
41
42	28	$decoder->checkCursorPosition();
43
44	20	return $value;
45		}
46
47	64	protected function __construct(string $bencoded)
48		{
49	64	$this->bencoded = $bencoded;
50	64	$this->len = strlen($bencoded);
51
52	64	if ($bencoded === '')
53		{
54	1	throw new DecodingException('Premature end of data', 0);
55		}
56	63	$this->computeSafeBoundary();
57	53	}
58
59	63	protected function checkBoundary(): void
60		{
61	63	if ($this->max < 1)
62		{
63	10	throw match ($this->bencoded[0])
64		{
65	2	'-', 'e' => new DecodingException('Illegal character', 0),
66	8	default => new DecodingException('Premature end of data', $this->len - 1)
67		};
68		}
69	53	}
70
71		/**
72		* Check the cursor's position after decoding is done
73		*/
74	28	protected function checkCursorPosition(): void
75		{
76	28	if (false)
77		{
78		die('?');
		0 ignored issues – show Best Practice introduced 2021-07-15 15:42 UTC by Report Bug Copy Issue Report Using `exit` here is not recommended. In general, usage of exit should be done with care and only when running in a scripting context like a CLI script. Loading history...
79		}
80	28	if ($this->offset !== $this->len)
81		{
82	8	if ($this->offset > $this->len)
83		{
84	3	throw new DecodingException('Premature end of data', $this->len - 1);
85		}
86
87	5	$this->complianceError('Superfluous content', $this->offset);
88		}
89	20	}
90
91	7	protected function checkDictionaryCompliance(int $offset, string $key, string $lastKey): void
92		{
93	7	$cmp = strcmp($key, $lastKey);
94	7	if ($cmp <= 0)
95		{
96	4	$msg = ($cmp === 0) ? 'Duplicate' : 'Out of order';
97	4	$this->complianceError($msg . " dictionary entry '" . $key . "'", $offset);
98		}
99	3	}
100
101	13	protected function complianceError(string $message, int $offset): void
102		{
103	13	throw new ComplianceError($message, $offset);
104		}
105
106		/**
107		* Adjust the rightmost boundary to the last safe character that can start a value
108		*
109		* Will rewind the boundary to skip the rightmost digits, optionally preceded by "i" or "i-"
110		*/
111	63	protected function computeSafeBoundary(): void
112		{
113	63	$boundary = $this->len - 1;
114		do
115		{
116	63	$c = $this->bencoded[$boundary];
117		}
118	63	while (str_contains('0123456789', $c) && --$boundary >= 0);
119
120	63	$this->max = match ($c)
121		{
122	6	'-' => $boundary - 2,
123	6	'i' => $boundary - 1,
124	51	default => $boundary
125		};
126	63	$this->checkBoundary();
127	53	}
128
129	53	protected function decodeAnything(): ArrayObject\|array\|int\|string
130		{
131	53	return match ($this->bencoded[$this->offset])
132		{
133	16	'd' => $this->decodeDictionary(),
134	19	'i' => $this->decodeInteger(),
135	13	'l' => $this->decodeList(),
136	43	default => $this->decodeString()
137		};
138		}
139
140	16	protected function decodeDictionary(): ArrayObject
141		{
142	16	$values = [];
143	16	$lastKey = null;
144
145	16	++$this->offset;
146	16	while ($this->offset <= $this->max)
147		{
148	16	if ($this->bencoded[$this->offset] === 'e')
149		{
150	7	++$this->offset;
151
152	7	return new ArrayObject($values, ArrayObject::ARRAY_AS_PROPS);
153		}
154
155	15	$offset = $this->offset;
156	15	$key = $this->decodeString();
157	14	if (isset($lastKey))
158		{
159	7	$this->checkDictionaryCompliance($offset, $key, $lastKey);
160		}
161	14	if ($this->offset > $this->max)
162		{
163	1	break;
164		}
165	13	$values[$key] = $this->decodeAnything();
166	10	$lastKey = $key;
167		}
168
169	1	throw new DecodingException('Premature end of data', $this->len - 1);
170		}
171
172	46	protected function decodeDigits(string $terminator): int
173		{
174		// Digits sorted by decreasing frequency as observed on a random sample of torrent files
175	46	$spn = strspn($this->bencoded, '4615302879', $this->offset);
176	46	if (!$spn)
177		{
178	7	throw new DecodingException('Illegal character', $this->offset);
179		}
180	41	if ($this->bencoded[$this->offset] === '0' && $spn !== 1)
181		{
182	3	$this->complianceError('Illegal character', 1 + $this->offset);
183		}
184
185		// Capture the value and cast it as an integer
186	38	$value = (int) substr($this->bencoded, $this->offset, $spn);
187
188	38	$this->offset += $spn;
189	38	if ($this->bencoded[$this->offset] !== $terminator)
190		{
191	5	throw new DecodingException('Illegal character', $this->offset);
192		}
193	33	++$this->offset;
194
195	33	return $value;
196		}
197
198	19	protected function decodeInteger(): int
199		{
200	19	$negative = ($this->bencoded[++$this->offset] === '-');
201	19	if ($negative && $this->bencoded[++$this->offset] === '0')
202		{
203	1	$this->complianceError('Illegal character', $this->offset);
204		}
205
206	18	$value = $this->decodeDigits('e');
207
208	13	return ($negative) ? -$value : $value;
209		}
210
211	13	protected function decodeList(): array
212		{
213	13	++$this->offset;
214
215	13	$list = [];
216	13	while ($this->offset <= $this->max)
217		{
218	12	if ($this->bencoded[$this->offset] === 'e')
219		{
220	8	++$this->offset;
221
222	8	return $list;
223		}
224
225	9	$list[] = $this->decodeAnything();
226		}
227
228	4	throw new DecodingException('Premature end of data', $this->len - 1);
229		}
230
231	36	protected function decodeString(): string
232		{
233	36	$len = $this->decodeDigits(':');
234	28	$string = substr($this->bencoded, $this->offset, $len);
235	28	$this->offset += $len;
236
237	28	return $string;
238		}
239		}

s9e / Bencode

Branch — test (3b2ced)

Decoder::checkCursorPosition() A

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