function parseElementStartPart()

in lib/ace/mode/xml/sax.js [190:346]
137 lines of code
42 McCabe index (conditional complexity)

function parseElementStartPart(source,start,el,entityReplacer,errorHandler){
	var attrName;
	var value;
	var p = ++start;
	var s = S_TAG;//status
	while(true){
		var c = source.charAt(p);
		switch(c){
		case '=':
			if(s === S_ATTR){//attrName
				attrName = source.slice(start,p);
				s = S_EQ;
			}else if(s === S_ATTR_S){
				s = S_EQ;
			}else{
				//fatalError: equal must after attrName or space after attrName
				throw new Error('attribute equal must after attrName');
			}
			break;
		case '\'':
		case '"':
			if(s === S_EQ){//equal
				start = p+1;
				p = source.indexOf(c,start)
				if(p>0){
					value = source.slice(start,p).replace(/&#?\w+;/g,entityReplacer);
					el.add(attrName,value,start-1);
					s = S_E;
				}else{
					//fatalError: no end quot match
					throw new Error('attribute value no end \''+c+'\' match');
				}
			}else if(s == S_V){
				value = source.slice(start,p).replace(/&#?\w+;/g,entityReplacer);
				//console.log(attrName,value,start,p)
				el.add(attrName,value,start);
				//console.dir(el)
				errorHandler.warning('attribute "'+attrName+'" missed start quot('+c+')!!');
				start = p+1;
				s = S_E
			}else{
				//fatalError: no equal before
				throw new Error('attribute value must after "="');
			}
			break;
		case '/':
			switch(s){
			case S_TAG:
				el.setTagName(source.slice(start,p));
			case S_E:
			case S_S:
			case S_C:
				s = S_C;
				el.closed = true;
			case S_V:
			case S_ATTR:
			case S_ATTR_S:
				break;
			//case S_EQ:
			default:
				throw new Error("attribute invalid close char('/')")
			}
			break;
		case ''://end document
			//throw new Error('unexpected end of input')
			errorHandler.error('unexpected end of input');
		case '>':
			switch(s){
			case S_TAG:
				el.setTagName(source.slice(start,p));
			case S_E:
			case S_S:
			case S_C:
				break;//normal
			case S_V://Compatible state
			case S_ATTR:
				value = source.slice(start,p);
				if(value.slice(-1) === '/'){
					el.closed  = true;
					value = value.slice(0,-1)
				}
			case S_ATTR_S:
				if(s === S_ATTR_S){
					value = attrName;
				}
				if(s == S_V){
					errorHandler.warning('attribute "'+value+'" missed quot(")!!');
					el.add(attrName,value.replace(/&#?\w+;/g,entityReplacer),start)
				}else{
					errorHandler.warning('attribute "'+value+'" missed value!! "'+value+'" instead!!')
					el.add(value,value,start)
				}
				break;
			case S_EQ:
				throw new Error('attribute value missed!!');
			}
//			console.log(tagName,tagNamePattern,tagNamePattern.test(tagName))
			return p;
		/*xml space '\x20' | #x9 | #xD | #xA; */
		case '\u0080':
			c = ' ';
		default:
			if(c<= ' '){//space
				switch(s){
				case S_TAG:
					el.setTagName(source.slice(start,p));//tagName
					s = S_S;
					break;
				case S_ATTR:
					attrName = source.slice(start,p)
					s = S_ATTR_S;
					break;
				case S_V:
					var value = source.slice(start,p).replace(/&#?\w+;/g,entityReplacer);
					errorHandler.warning('attribute "'+value+'" missed quot(")!!');
					el.add(attrName,value,start)
				case S_E:
					s = S_S;
					break;
				//case S_S:
				//case S_EQ:
				//case S_ATTR_S:
				//	void();break;
				//case S_C:
					//ignore warning
				}
			}else{//not space
//S_TAG,	S_ATTR,	S_EQ,	S_V
//S_ATTR_S,	S_E,	S_S,	S_C
				switch(s){
				//case S_TAG:void();break;
				//case S_ATTR:void();break;
				//case S_V:void();break;
				case S_ATTR_S:
					errorHandler.warning('attribute "'+attrName+'" missed value!! "'+attrName+'" instead!!')
					el.add(attrName,attrName,start);
					start = p;
					s = S_ATTR;
					break;
				case S_E:
					errorHandler.warning('attribute space is required"'+attrName+'"!!')
				case S_S:
					s = S_ATTR;
					start = p;
					break;
				case S_EQ:
					s = S_V;
					start = p;
					break;
				case S_C:
					throw new Error("elements closed character '/' and '>' must be connected to");
				}
			}
		}
		p++;
	}
}