Iterate over a delimited input stream

delim_istream_iterator.hpp

#include <iterator>
#include <istream>
#include <string>
#include <cassert>
#include <cstddef>

/**
 * Iterate over each part of a delimited input stream.
 * For example, to split a string into a vector:
 *
 *     std::istringstream ss("This;is a;list");
 *     std::vector<std::string> items(delim_istream_iterator<>(ss,';'),
 *                                    delim_istream_iterator<>());
 */
template <class CharT = char,
          class Traits = std::char_traits<CharT>,
          class Distance = std::ptrdiff_t>
class delim_istream_iterator
	: public std::iterator<std::input_iterator_tag,
	                       std::basic_string<CharT, Traits>,
	                       Distance,
	                       const std::basic_string<CharT, Traits>*,
	                       const std::basic_string<CharT, Traits>&>
{
	public:
		typedef std::basic_istream<CharT, Traits> istream_type;
		typedef std::basic_string<CharT, Traits> value_type;

		delim_istream_iterator()
			: stream(nullptr), value(), ok(false) { }

		delim_istream_iterator(istream_type& stream, CharT delimiter)
			: stream(&stream), delimiter(delimiter) {
			read();
		}

		delim_istream_iterator(const delim_istream_iterator& other)
			: stream(other.stream), value(other.value),
			  ok(other.ok), delimiter(other.delimiter) { }

		const value_type &operator*() const {
			assert(ok);
			return value;
		}

		const value_type* operator->() const {
			return &(operator*());
		}

		delim_istream_iterator& operator++() {
			assert(ok);
			read();
			return *this;
		}

		delim_istream_iterator operator++(int) {
			assert(ok);
			delim_istream_iterator temp = *this;
			read();
			return temp;
		}

		friend bool operator==(const delim_istream_iterator& a,
		                       const delim_istream_iterator& b) {
			return (a.ok == b.ok) && (!a.ok || a.stream == b.stream);
		}

		friend bool operator!=(const delim_istream_iterator& a,
		                       const delim_istream_iterator& b) {
			return !operator==(a, b);
		}

	private:
		istream_type* stream;
		value_type value;
		bool ok;
		CharT delimiter;

		void read() {
			ok = (stream && *stream);
			if (ok) {
				std::getline(*stream, value, delimiter);
				ok = *stream;
			}
		}
};