Extract consecutive strings logic into a separate class

This is going to be also used in the upcoming ClassManager class.
It also makes FullSignatureOwning less cluttered.

include/wrenpp/callback_manager.hpp

@@ -18,6 +18,7 @@
 #pragma once
 
 #include "wren_types.hpp"
+#include "strings_in_vector.hpp"
 #include <unordered_map>
 #include <vector>
 #include <string_view>
@@ -60,25 +61,13 @@ namespace wren {
 			std::size_t m_signature_hash;
 		};
 
-		class FullSignatureOwning : public FullSignatureBase {
+		class FullSignatureOwning : public FullSignatureBase, private StringsInVector<3> {
 		public:
 			FullSignatureOwning (std::string_view module_name, std::string_view class_name, std::string_view signature);
 
-			std::string_view module_name() const { return make_string_view(m_module_range); }
+			std::string_view module_name() const { return as_string_view<0>(); }
-			std::string_view class_name() const { return make_string_view(m_class_range); }
+			std::string_view class_name() const { return as_string_view<1>(); }
-			std::string_view signature() const { return make_string_view(m_signature_range); }
+			std::string_view signature() const { return as_string_view<2>(); }
-
-		private:
-			struct WordRange {
-				std::size_t start, length;
-			};
-
-			std::string_view make_string_view(WordRange range) const;
-
-			std::vector<char> m_full_name;
-			WordRange m_module_range;
-			WordRange m_class_range;
-			WordRange m_signature_range;
 		};
 
 		//Temp because it's only supposed to be used to store temporaries

include/wrenpp/strings_in_vector.hpp

@@ -0,0 +1,136 @@
+/* Copyright 2020-2022, Michele Santullo
+ * This file is part of wrenpp.
+ *
+ * Wrenpp is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Wrenpp is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with wrenpp.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <vector>
+#include <string_view>
+#include <utility>
+#include <algorithm>
+#include <cassert>
+
+namespace wren {
+	namespace detail {
+		template <std::size_t Num>
+		struct StringsInVectorBase;
+
+		struct StringsInVectorWordRange {
+			std::size_t start, length;
+		};
+
+		template <std::size_t Num>
+		struct StringsInVectorBase {
+			explicit StringsInVectorBase (StringsInVectorWordRange range) :
+				m_word_range(range)
+			{ }
+
+			StringsInVectorWordRange m_word_range;
+		};
+
+		template <std::size_t Index, typename String, typename... Strings>
+		[[gnu::pure]]
+		std::size_t string_offset_at_index (const String& string, const Strings&... strings) {
+			static_assert(Index < sizeof...(Strings) + 1, "Index out of range");
+
+			if constexpr (not Index) {
+				return 0;
+			}
+			else {
+				return std::string_view{string}.size() + string_offset_at_index<Index - 1>(strings...);
+			}
+		}
+
+		inline void set_zero (char& value) {
+			value = '\0';
+		}
+	} //namespace detail
+
+	template <std::size_t Count, typename IndexSeq>
+	class StringsInVectorImplem;
+
+	//It's a class that stores a series of strings in a vector, consecutively
+	//and interleaved by a null char. Objects of this class are safe to move
+	//and copy, move doesn't invalidate previously obtained string_views
+	//and strings_views are guaranteed to be null-terminated, so the result
+	//of data() is safe to pass to C functions.
+	template <std::size_t Count, std::size_t... Indices>
+	class StringsInVectorImplem<Count, std::index_sequence<Indices...>> : detail::StringsInVectorBase<Indices>... {
+		typedef detail::StringsInVectorWordRange WordRange;
+	public:
+		template <typename... Strings>
+		StringsInVectorImplem (const Strings&... strings);
+
+		template <std::size_t Index>
+		std::string_view as_string_view() const;
+
+		bool operator== (const StringsInVectorImplem& other) const;
+		bool operator< (const StringsInVectorImplem& other) const;
+
+	private:
+		std::vector<char> m_memory;
+	};
+
+	template <std::size_t Count, std::size_t... Indices>
+	template <typename... Strings>
+	inline StringsInVectorImplem<Count, std::index_sequence<Indices...>>::StringsInVectorImplem(const Strings&... strings) :
+		detail::StringsInVectorBase<Indices>(WordRange{detail::string_offset_at_index<Indices>(strings...) + Indices, std::string_view{strings}.size()})...
+	{
+		using detail::string_offset_at_index;
+		using detail::set_zero;
+
+		const std::size_t buffer_size = (std::string_view{strings}.size() + ...) + sizeof...(Indices);
+		m_memory.resize(buffer_size);
+		(std::copy(
+			std::string_view{strings}.cbegin(),
+			std::string_view{strings}.cend(),
+			m_memory.begin() + string_offset_at_index<Indices>(strings...) + Indices
+		), ...);
+
+		//zero out the byte after each string
+		(set_zero(m_memory[string_offset_at_index<Indices>(strings...) + Indices + std::string_view(strings).size()]), ...);
+	}
+
+	template <std::size_t Count, std::size_t... Indices>
+	template <std::size_t Index>
+	inline std::string_view StringsInVectorImplem<Count, std::index_sequence<Indices...>>::as_string_view() const {
+		static_assert(Index < Count, "Index out of range");
+		const auto& word_range = detail::StringsInVectorBase<Index>::m_word_range;
+		assert(m_memory.size() >= word_range.start + word_range.length + 1);
+
+		std::string_view retval{
+			m_memory.data() + word_range.start,
+			word_range.length
+		};
+		assert(*(retval.data() + retval.length()) == '\0');
+		return retval;
+	}
+
+	template <std::size_t Count, std::size_t... Indices>
+	inline bool StringsInVectorImplem<Count, std::index_sequence<Indices...>>::operator== (const StringsInVectorImplem& other) const {
+		return this->m_memory == other.m_memory;
+	}
+
+	template <std::size_t Count, std::size_t... Indices>
+	inline bool StringsInVectorImplem<Count, std::index_sequence<Indices...>>::operator< (const StringsInVectorImplem& other) const {
+		std::string_view this_memory{m_memory.data(), m_memory.size()};
+		std::string_view other_memory{other.m_memory.data(), other.m_memory.size()};
+		return this_memory < other_memory;
+	}
+
+	template <std::size_t Count>
+	using StringsInVector = StringsInVectorImplem<Count, decltype(std::make_index_sequence<Count>())>;
+} //namespace wren

src/callback_manager.cpp

@@ -21,40 +21,9 @@
 
 namespace wren::detail {
 	FullSignatureOwning::FullSignatureOwning (std::string_view module_name, std::string_view class_name, std::string_view signature) :
-		FullSignatureBase(std::hash<std::string_view>{}(module_name), std::hash<std::string_view>{}(class_name), std::hash<std::string_view>{}(signature))
+		FullSignatureBase(std::hash<std::string_view>{}(module_name), std::hash<std::string_view>{}(class_name), std::hash<std::string_view>{}(signature)),
+		StringsInVector<3>(module_name, class_name, signature)
 	{
-		m_full_name.resize(module_name.size() + 1 + class_name.size() + 1 + signature.size() + 1);
-		char* buff = m_full_name.data();
-		std::size_t buff_used = 0;
-
-		std::copy(module_name.cbegin(), module_name.cend(), buff + buff_used);
-		m_module_range.start = buff_used;
-		m_module_range.length = module_name.size();
-		buff[buff_used + module_name.size()] = '\0';
-		buff_used += module_name.size() + 1;
-
-		std::copy(class_name.cbegin(), class_name.cend(), buff + buff_used);
-		m_class_range.start = buff_used;
-		m_class_range.length = class_name.size();
-		buff[buff_used + class_name.size()] = '\0';
-		buff_used += class_name.size() + 1;
-
-		std::copy(signature.cbegin(), signature.cend(), buff + buff_used);
-		m_signature_range.start = buff_used;
-		m_signature_range.length = signature.size();
-		buff[buff_used + signature.size()] = '\0';
-		buff_used += signature.size() + 1;
-
-		assert(m_full_name[m_module_range.start + m_module_range.length] == '\0');
-		assert(m_full_name[m_class_range.start + m_class_range.length] == '\0');
-		assert(m_full_name[m_signature_range.start + m_signature_range.length] == '\0');
-		assert(this->module_name() == module_name);
-		assert(this->class_name() == class_name);
-		assert(this->signature() == signature);
-	}
-
-	std::string_view FullSignatureOwning::make_string_view(WordRange range) const {
-		return {m_full_name.data() + range.start, range.length};
 	}
 
 	TempFullSignature::TempFullSignature (const FullSignatureOwning& full_sig) :