Add implementation to consume a number reference

https://html.spec.whatwg.org/multipage/syntax.html#consume-a-character-reference

HTMLKit/HTMLTokenizer.m

@@ -128,7 +128,49 @@
 
 - (NSString *)consumeNumberCharacterReference
 {
-	return nil;
+	[_inputStreamReader markCurrentLocation];
+
+	[_inputStreamReader consumeNextInputCharacter];
+
+	UTF32Char character = [_inputStreamReader nextInputCharacter];
+	unsigned int number;
+	BOOL success;
+
+	switch (character) {
+		case LATIN_CAPITAL_LETTER_X:
+		case LATIN_SMALL_LETTER_X:
+			[_inputStreamReader consumeNextInputCharacter];
+			success = [_inputStreamReader consumeHexInt:&number];
+			break;
+		default:
+			success = [_inputStreamReader consumeHexInt:&number];
+			break;
+	}
+
+	if (success == NO) {
+		[_inputStreamReader rewindToMarkedLocation];
+		[self emitParseError:@"Invalid characters in numeric entity"];
+		return nil;
+	}
+	success = [_inputStreamReader consumeCharacter:SEMICOLON];
+	if (success == NO) {
+		[self emitParseError:@"Missing semicolon in numeric entity"];
+	}
+
+	unichar numericReplacement = NumericReplacementCharacter(character);
+	if (numericReplacement != NULL_CHAR) {
+		[self emitParseError:@"Invalid numeric entity (a defenied replacement exists)"];
+		return StringFromUniChar(numericReplacement);
+	}
+	if (isValidNumericRange(character)) {
+		[self emitParseError:@"Invalid numeric entity (invalid Unicode range)"];
+		return StringFromUniChar(REPLACEMENT_CHAR);
+	}
+	if (isControlOrUndefinedCharacter(character)) {
+		[self emitParseError:@"Invalid numeric entity (control or undefined character)"];
+	}
+
+	return StringFromUTF32Char(character);
 }
 
 #pragma mark - States

HTMLKit/HTMLTokenizerCharacters.h

@@ -97,3 +97,47 @@ NS_INLINE BOOL isValidNumericRange(UTF32Char character)
 			|| character > 0x10FFFF);
 }
 
+NS_INLINE unichar NumericReplacementCharacter(UTF32Char character)
+{
+	switch(character) {
+		case 0x00: return 0xFFFD; /* REPLACEMENT CHARACTER */
+		case 0x80: return 0x20AC; /* EURO SIGN */
+		case 0x82: return 0x201A; /* SINGLE LOW-9 QUOTATION MARK */
+		case 0x83: return 0x0192; /* LATIN SMALL LETTER F WITH HOOK */
+		case 0x84: return 0x201E; /* DOUBLE LOW-9 QUOTATION MARK */
+		case 0x85: return 0x2026; /* HORIZONTAL ELLIPSIS */
+		case 0x86: return 0x2020; /* DAGGER */
+		case 0x87: return 0x2021; /* DOUBLE DAGGER */
+		case 0x88: return 0x02C6; /* MODIFIER LETTER CIRCUMFLEX ACCENT */
+		case 0x89: return 0x2030; /* PER MILLE SIGN */
+		case 0x8A: return 0x0160; /* LATIN CAPITAL LETTER S WITH CARON */
+		case 0x8B: return 0x2039; /* SINGLE LEFT-POINTING ANGLE QUOTATION MARK */
+		case 0x8C: return 0x0152; /* LATIN CAPITAL LIGATURE OE */
+		case 0x8E: return 0x017D; /* LATIN CAPITAL LETTER Z WITH CARON */
+		case 0x91: return 0x2018; /* LEFT SINGLE QUOTATION MARK */
+		case 0x92: return 0x2019; /* RIGHT SINGLE QUOTATION MARK */
+		case 0x93: return 0x201C; /* LEFT DOUBLE QUOTATION MARK */
+		case 0x94: return 0x201D; /* RIGHT DOUBLE QUOTATION MARK */
+		case 0x95: return 0x2022; /* BULLET */
+		case 0x96: return 0x2013; /* EN DASH */
+		case 0x97: return 0x2014; /* EM DASH */
+		case 0x98: return 0x02DC; /* SMALL TILDE */
+		case 0x99: return 0x2122; /* TRADE MARK SIGN */
+		case 0x9A: return 0x0161; /* LATIN SMALL LETTER S WITH CARON */
+		case 0x9B: return 0x203A; /* SINGLE RIGHT-POINTING ANGLE QUOTATION MARK */
+		case 0x9C: return 0x0153; /* LATIN SMALL LIGATURE OE */
+		case 0x9E: return 0x017E; /* LATIN SMALL LETTER Z WITH CARON */
+		case 0x9F: return 0x0178; /* LATIN CAPITAL LETTER Y WITH DIAERESIS */
+	}
+	return 0x00;
+}
+
+NS_INLINE NSString * StringFromUniChar(unichar character)
+{
+	return [[NSString alloc] initWithCharacters:&character length:1];
+}
+
+NS_INLINE NSString * StringFromUTF32Char(UTF32Char character)
+{
+	return [[NSString alloc] initWithBytes:&character length:sizeof(character) encoding:NSUTF32StringEncoding];
+}

HTMLKit/HTMLTokenizerStates.h

@@ -84,7 +84,7 @@ typedef NS_ENUM(NSUInteger, HTMLTokenizerState)
 #undef STATE_ENTRY
 };
 
-static NSString* HTMLTokenizerStatesTable[] = {
+static NSString * HTMLTokenizerStatesTable[] = {
 #define STATE_ENTRY( name, value ) [name] = @#name,
 	TOKENIZER_STATES
 #undef STATE_ENTRY