Streamlined Decoder::readDigits() for common paths

Author: JoshyPHP

src/Decoder.php

@@ -252,6 +252,13 @@ protected function dictionaryComplianceError(string $key, string $lastKey): void
 		$this->complianceError($msg . " dictionary entry '" . $key . "'", $offset);
 	}
 
+	protected function digitException(): DecodingException
+	{
+		return (str_contains('0123456789', $this->bencoded[$this->offset]))
+		     ? new ComplianceError('Illegal character', $this->offset)
+		     : new DecodingException('Illegal character', $this->offset);
+	}
+
 	/**
 	* Return the rightmost boundary to the last safe character that can start a value
 	*
@@ -276,23 +283,26 @@ protected function getSafeBoundary(): int
 
 	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 === 0)
+		if ($this->bencoded[$this->offset] === '0')
 		{
-			throw new DecodingException('Illegal character', $this->offset);
+			++$this->offset;
+			$string = '0';
 		}
-
-		$string = substr($this->bencoded, $this->offset, $spn);
-		if ($string[0] === '0' && $spn !== 1)
+		else
 		{
-			$this->complianceError('Illegal character', 1 + $this->offset);
+			// Digits sorted by decreasing frequency as observed on a random sample of torrent files
+			$spn = strspn($this->bencoded, '1463720859', $this->offset);
+			if ($spn === 0)
+			{
+				throw new DecodingException('Illegal character', $this->offset);
+			}
+			$string = substr($this->bencoded, $this->offset, $spn);
+			$this->offset += $spn;
 		}
 
-		$this->offset += $spn;
 		if ($this->bencoded[$this->offset] !== $terminator)
 		{
-			throw new DecodingException('Illegal character', $this->offset);
+			throw $this->digitException();
 		}
 		++$this->offset;
 

src/NonCompliantDecoder.php

@@ -9,7 +9,7 @@
 
 use ArrayObject;
 use const SORT_STRING, false, true;
-use function strcmp;
+use function preg_match, strcmp, strlen;
 
 class NonCompliantDecoder extends Decoder
 {
@@ -41,4 +41,16 @@ protected function dictionaryComplianceError(string $key, string $lastKey): void
 	{
 		$this->sortDictionary = true;
 	}
+
+	protected function readDigits(string $terminator): string
+	{
+		if ($this->bencoded[$this->offset] === '0')
+		{
+			// Skip past the trailing zeroes and stop at the next digit or the last zero
+			preg_match('(0++[1-9]?)A', $this->bencoded, $m, 0, $this->offset);
+			$this->offset += strlen($m[0]) - 1;
+		}
+
+		return parent::readDigits($terminator);
+	}
 }

tests/DecoderTest.php

@@ -268,6 +268,10 @@ public static function getDecodeInvalidTests()
 				'i1x',
 				new DecodingException('Illegal character', 2)
 			],
+			[
+				'i0x',
+				new DecodingException('Illegal character', 2)
+			],
 			[
 				'lxe',
 				new DecodingException('Illegal character', 1)