Consume expression to indicate how many characters to look ahead

Where possible consumeExpression should be provided with the
maximum number of characters the expression could be made of.
This allows for more efficiently peeking for a few characters
rather than the entire remaining character map.

Author: Frédéric Massart

lib/Sabberworm/CSS/Parser.php

@@ -265,7 +265,7 @@ private function parseCharacter($bIsForIdentifier) {
 			if (preg_match('/[0-9a-fA-F]/Su', $this->peek()) === 0) {
 				return $this->consume(1);
 			}
-			$sUnicode = $this->consumeExpression('/^[0-9a-fA-F]{1,6}/u');
+			$sUnicode = $this->consumeExpression('/^[0-9a-fA-F]{1,6}/u', 6);
 			if ($this->strlen($sUnicode) < 6) {
 				//Consume whitespace after incomplete unicode escape
 				if (preg_match('/\\s/isSu', $this->peek())) {
@@ -565,9 +565,10 @@ private function consume($mValue = 1) {
 		}
 	}
 
-	private function consumeExpression($mExpression) {
+	private function consumeExpression($mExpression, $iMaxLength = null) {
 		$aMatches = null;
-		if (preg_match($mExpression, $this->inputLeft(), $aMatches, PREG_OFFSET_CAPTURE) === 1) {
+		$sInput = $iMaxLength !== null ? $this->peek($iMaxLength) : $this->inputLeft();
+		if (preg_match($mExpression, $sInput, $aMatches, PREG_OFFSET_CAPTURE) === 1) {
 			return $this->consume($aMatches[0][0]);
 		}
 		throw new UnexpectedTokenException($mExpression, $this->peek(5), 'expression', $this->iLineNo);