Simple STL-only HTML entity unescaper

html.h

	inline void unescape(std::string& input) {
			bool in_escape_block = false;
			std::string::size_type begin{}, count{};
		
			auto iter = input.begin();
			while(iter != input.end()) {
				char c = *iter;
			
				if(c == '&' && !in_escape_block && /* Please send help */ (*(iter+1) != '&' && *(iter+1) != ' ')) {
					// Entered a escape block
					begin = (iter - input.begin());
					in_escape_block = true;
				}
			
				if(c == ';' && in_escape_block) {
					// Exited a escape block.
					std::string code = input.substr(begin+1, (count-1));
					in_escape_block = false;
	
#define HTML_CODECASE(htmlcode, replacement) if(code == htmlcode) { \
											input.replace(begin, sizeof("&" htmlcode), replacement); \
											unescape(input); \
											return; }

					HTML_CODECASE("nbsp", " ")
					HTML_CODECASE("amp", "&")
					HTML_CODECASE("lt", "<")
					HTML_CODECASE("gt", ">")
					HTML_CODECASE("quot", "\"")
					HTML_CODECASE("#x27", "\'")
					HTML_CODECASE("#x2F", "/")
				}
				
				if(in_escape_block && count >= 5 /* Max size of any entity processed, update */) {
					return;
				}
				
				if(in_escape_block) count++;
				iter++;
			}
		}