hello.cpp

#include <cstring>
#include <memory>
#include <iostream>
#include <string>
#include <vector>

#include "pugixml.hpp"

struct t_hello;

struct t_hello {
	std::string greeting;
	std::vector<std::string> name_list;
};

std::unique_ptr<t_hello> hello;

void read_t_hello(pugi::xml_node &root, t_hello &out);

void read(const char *filename){
	pugi::xml_document doc;
	pugi::xml_parse_result result = doc.load_file(filename);
	if(!result){
		throw std::runtime_error("Could not load XML file " + std::string(filename) + ".");
	}
	pugi::xml_node node = doc.first_child();
	for(; node; node = node.next_sibling()){
		if(std::strcmp(node.name(), "hello") == 0){
			hello = std::unique_ptr<t_hello>(new t_hello);
			read_t_hello(node, *hello);
		}
		else throw std::runtime_error("Invalid root-level element " + std::string(node.name()));
	}
}


void read_t_hello(pugi::xml_node &root, t_hello &out){
	pugi::xml_node node = root.first_child();
	const char *in = node.name();
	int state = 2;
	while(1){
		switch(state){
		case 0:
			if(strcmp(in, "name") == 0){
				state = 0;
				out.name_list.push_back(node.text().get());
			}
			else if(strcmp(in, "end of input") == 0){
				goto accept;
			}
			else throw std::runtime_error("expected <name> or end of input, found " + std::string(in));
			break;
		case 1:
			if(strcmp(in, "name") == 0){
				state = 0;
				out.name_list.push_back(node.text().get());
			}
			else throw std::runtime_error("expected <name>, found " + std::string(in));
			break;
		case 2:
			if(strcmp(in, "greeting") == 0){
				state = 1;
				out.greeting = node.text().get();
			}
			else throw std::runtime_error("expected <greeting>, found " + std::string(in));
			break;
		}
		node = node.next_sibling();
		if(node) in = node.name();
		else in = "end of input";
	}
accept:
	return;
}


int main(){
	read("hello.xml");
	std::cout << hello->greeting << "\n";
	for(auto name : hello->name_list){
		std::cout << "\t" << name << "\n";
	}
}

Is it possible to use enums for the state values and provide better names for them?

Something like this?

enum class t_hello_state {GET_NAME_OR_END, GET_NAME, GET_GREETING};
void read_t_hello(pugi::xml_node &root, t_hello &out){
	pugi::xml_node node = root.first_child();
	const char *in = node.name();
	t_hello_state state = t_hello_state::GET_GREETING;
	while(1){
		switch(state){
		case t_hello_state::GET_NAME_OR_END:
			if(strcmp(in, "name") == 0){
				state = t_hello_state::GET_NAME_OR_END;
				out.name_list.push_back(node.text().get());
			}
			else if(strcmp(in, "end of input") == 0){
				goto accept;
			}
			else throw std::runtime_error("expected <name> or end of input, found " + std::string(in));
			break;
		case t_hello_state::GET_NAME:
			if(strcmp(in, "name") == 0){
				state = t_hello_state::GET_NAME_OR_END;
				out.name_list.push_back(node.text().get());
			}
			else throw std::runtime_error("expected <name>, found " + std::string(in));
			break;
		case t_hello_state::GET_GREETING:
			if(strcmp(in, "greeting") == 0){
				state = t_hello_state::GET_NAME;
				out.greeting = node.text().get();
			}
			else throw std::runtime_error("expected <greeting>, found " + std::string(in));
			break;
		}
		node = node.next_sibling();
		if(node) in = node.name();
		else in = "end of input";
	}
accept:
	return;
}

Much better!