Implement const_iterators.

Note that they are not available in the base class.

src/env_fake.cpp

@@ -126,4 +126,19 @@ void EnvFake::clear() noexcept {
 	m_map_strong_cpy.clear();
 }
 
+auto EnvFake::begin() const -> const_iterator {
+	return m_map.cbegin();
+}
+
+auto EnvFake::cbegin() const -> const_iterator {
+	return m_map.cbegin();
+}
+
+auto EnvFake::end() const -> const_iterator {
+	return m_map.cend();
+}
+
+auto EnvFake::cend() const -> const_iterator {
+	return m_map.cend();
+}
 } //namespace duck

src/env_fake.hpp

@@ -25,6 +25,8 @@ namespace duck {
 	class EnvFake : public EnvBase {
 		typedef std::unordered_map<std::string_view, std::string_view> map_type;
 	public:
+		typedef map_type::const_iterator const_iterator;
+
 		explicit EnvFake (bool starts_empty=false);
 		~EnvFake() noexcept = default;
 
@@ -36,6 +38,11 @@ namespace duck {
 		virtual size_type size() const noexcept override;
 		virtual void clear() noexcept override;
 
+		const_iterator begin() const;
+		const_iterator cbegin() const;
+		const_iterator end() const;
+		const_iterator cend() const;
+
 	private:
 		std::unordered_map<std::string_view, std::unique_ptr<char[]>> m_map_strong_cpy;
 		map_type m_map;

src/env_real.cpp

@@ -27,7 +27,6 @@
 #include <unordered_map>
 #include <memory>
 #include <cassert>
-#include <utility>
 #include <cstring>
 
 #if defined(__GNU_LIBRARY__) && ((__GLIBC__ == 2 && __GLIBC_MINOR__ >= 17) || __GLIBC__ > 2)
@@ -149,8 +148,56 @@ namespace {
 			}
 		}
 	}
+
+	std::pair<std::string_view, std::string_view> to_pair (char* env_entry) noexcept {
+		std::string_view text(to_string_view(env_entry));
+		const auto eq_pos = text.find('=');
+		if (eq_pos == text.npos) {
+			assert(false);
+			return {"", ""};
+		}
+
+		return std::make_pair(
+			text.substr(0, eq_pos),
+			text.substr(eq_pos + 1)
+		);
+	}
 } //unnamed namespace
 
+namespace detail {
+	EnvironIterator::EnvironIterator (char** env) noexcept :
+		m_curr(),
+		m_env(env),
+		m_dirty(true)
+	{
+		assert(m_env);
+	}
+
+	auto EnvironIterator::operator*() noexcept -> value_type& {
+		return *this->operator->();
+	}
+
+	auto EnvironIterator::operator->() noexcept -> value_type* {
+		if (m_dirty) {
+			m_curr = (m_env and *m_env ? to_pair(*m_env) : value_type());
+			m_dirty = false;
+		}
+		return &m_curr;
+	}
+
+	EnvironIterator EnvironIterator::operator++(int) noexcept {
+		EnvironIterator cpy(*this);
+		++(*this);
+		return cpy;
+	}
+
+	EnvironIterator EnvironIterator::operator--(int) noexcept {
+		EnvironIterator cpy(*this);
+		--(*this);
+		return cpy;
+	}
+} //namespace detial
+
 EnvReal::EnvReal() :
 	m_name_buff(std::make_unique<char[]>(g_name_buff_len)),
 	m_name_buff_len(g_name_buff_len)
@@ -251,4 +298,21 @@ const char* EnvReal::raw_fetch_env (std::string_view name) const noexcept {
 	);
 }
 
+auto EnvReal::begin() const -> const_iterator {
+	return {::environ};
+}
+
+auto EnvReal::cbegin() const -> const_iterator {
+	return {::environ};
+}
+
+auto EnvReal::end() const -> const_iterator {
+	assert(*(::environ + this->size()) == nullptr);
+	return {::environ + this->size()};
+}
+
+auto EnvReal::cend() const -> const_iterator {
+	assert(*(::environ + this->size()) == nullptr);
+	return {::environ + this->size()};
+}
 } //namespace duck

src/env_real.hpp

@@ -19,10 +19,36 @@
 
 #include "env_base.hpp"
 #include <memory>
+#include <utility>
 
 namespace duck {
+	namespace detail {
+		class EnvironIterator {
+		public:
+			typedef std::pair<std::string_view, std::string_view> value_type;
+
+			EnvironIterator (char** env) noexcept;
+			value_type& operator*() noexcept;
+			value_type* operator->() noexcept;
+
+			bool operator== (const EnvironIterator& other) const { return m_env == other.m_env; }
+			bool operator!= (const EnvironIterator& other) const { return m_env != other.m_env; }
+			EnvironIterator& operator++() noexcept { ++m_env; m_dirty = true; return *this; }
+			EnvironIterator& operator--() noexcept { --m_env; m_dirty = true; return *this; }
+			EnvironIterator operator++(int) noexcept;
+			EnvironIterator operator--(int) noexcept;
+
+		private:
+			value_type m_curr;
+			char** m_env;
+			bool m_dirty;
+		};
+	} //namespace detail
+
 	class EnvReal : public EnvBase {
 	public:
+		typedef detail::EnvironIterator const_iterator;
+
 		EnvReal();
 		virtual ~EnvReal() noexcept = default;
 
@@ -34,6 +60,11 @@ namespace duck {
 		virtual size_type size() const noexcept override;
 		virtual void clear() noexcept override;
 
+		const_iterator begin() const;
+		const_iterator cbegin() const;
+		const_iterator end() const;
+		const_iterator cend() const;
+
 	private:
 		const char* raw_fetch_env (std::string_view name) const noexcept;
 

src/string_view_cat.hpp

@@ -33,7 +33,7 @@ namespace duck {
 		return str;
 	}
 
-	inline std::string_view to_string_view (const char* str) {
+	inline std::string_view to_string_view (const char* str) noexcept {
 		return (str ? std::string_view{str} : std::string_view{""});
 	}