BAN: String now uses union for its sso storage

This allows String to shrink by 8 bytes since Variant's 8 index is
no longer stored in here.

This required me to make Strings max size one bit less, but that
should still be fine. There should never be strings with size of
over half of the computer's address space.

BAN/BAN/String.cpp

@@ -1,6 +1,5 @@
 #include <BAN/String.h>
 #include <BAN/New.h>
-#include <BAN/Variant.h>
 
 namespace BAN
 {
@@ -32,8 +31,7 @@ namespace BAN
 	String& String::operator=(const String& other)
 	{
 		clear();
-		if (!other.fits_in_sso())
-			MUST(ensure_capacity(other.size()));
+		MUST(ensure_capacity(other.size()));
 		memcpy(data(), other.data(), other.size() + 1);
 		m_size = other.size();
 		return *this;
@@ -43,14 +41,18 @@ namespace BAN
 	{
 		clear();
 
-		if (other.fits_in_sso())
+		if (other.has_sso())
 			memcpy(data(), other.data(), other.size() + 1);
 		else
-			m_storage = other.m_storage.get<GeneralStorage>();
+		{
+			m_storage.general_storage = other.m_storage.general_storage;
+			m_has_sso = false;
+		}
 		m_size = other.m_size;
 
 		other.m_size = 0;
-		other.m_storage = SSOStorage();
+		other.m_storage.sso_storage = SSOStorage();
+		other.m_has_sso = true;
 
 		return *this;
 	}
@@ -58,8 +60,7 @@ namespace BAN
 	String& String::operator=(StringView other)
 	{
 		clear();
-		if (!fits_in_sso(other.size()))
-			MUST(ensure_capacity(other.size()));
+		MUST(ensure_capacity(other.size()));
 		memcpy(data(), other.data(), other.size());
 		m_size = other.size();
 		data()[m_size] = '\0';
@@ -125,8 +126,9 @@ namespace BAN
 	{
 		if (!has_sso())
 		{
-			deallocator(m_storage.get<GeneralStorage>().data);
-			m_storage = SSOStorage();
+			deallocator(m_storage.general_storage.data);
+			m_storage.sso_storage = SSOStorage();
+			m_has_sso = true;
 		}
 		m_size = 0;
 		data()[m_size] = '\0';
@@ -167,15 +169,6 @@ namespace BAN
 			return {};
 		}
 
-		// shrink general -> sso
-		if (!has_sso() && fits_in_sso(new_size))
-		{
-			char* data = m_storage.get<GeneralStorage>().data;
-			m_storage = SSOStorage();
-			memcpy(m_storage.get<SSOStorage>().storage, data, new_size);
-			deallocator(data);
-		}
-
 		m_size = new_size;
 		data()[m_size] = '\0';
 		return {};
@@ -194,20 +187,21 @@ namespace BAN
 
 		if (fits_in_sso())
 		{
-			char* data = m_storage.get<GeneralStorage>().data;
-			m_storage = SSOStorage();
-			memcpy(m_storage.get<SSOStorage>().storage, data, m_size + 1);
+			char* data = m_storage.general_storage.data;
+			m_storage.sso_storage = SSOStorage();
+			m_has_sso = true;
+			memcpy(this->data(), data, m_size + 1);
 			deallocator(data);
 			return {};
 		}
 
-		GeneralStorage& storage = m_storage.get<GeneralStorage>();
+		GeneralStorage& storage = m_storage.general_storage;
 		if (storage.capacity == m_size)
 			return {};
 
 		char* new_data = (char*)allocator(m_size + 1);
 		if (new_data == nullptr)
-			return BAN::Error::from_errno(ENOMEM);
+			return Error::from_errno(ENOMEM);
 
 		memcpy(new_data, storage.data, m_size);
 		deallocator(storage.data);
@@ -222,40 +216,45 @@ namespace BAN
 	{
 		if (has_sso())
 			return sso_capacity;
-		return m_storage.get<GeneralStorage>().capacity;
+		return m_storage.general_storage.capacity;
 	}
 
 	char* String::data()
 	{
 		if (has_sso())
-			return m_storage.get<SSOStorage>().storage;
-		return m_storage.get<GeneralStorage>().data;
+			return m_storage.sso_storage.data;
+		return m_storage.general_storage.data;
 	}
 
 	const char* String::data() const
 	{
 		if (has_sso())
-			return m_storage.get<SSOStorage>().storage;
-		return m_storage.get<GeneralStorage>().data;
+			return m_storage.sso_storage.data;
+		return m_storage.general_storage.data;
 	}
 
 	ErrorOr<void> String::ensure_capacity(size_type new_size)
 	{
-		if (m_size >= new_size || fits_in_sso(new_size))
+		if (m_size >= new_size)
+			return {};
+		if (has_sso() && fits_in_sso(new_size))
 			return {};
 		
 		char* new_data = (char*)allocator(new_size + 1);
 		if (new_data == nullptr)
-			return BAN::Error::from_errno(ENOMEM);
+			return Error::from_errno(ENOMEM);
 		
 		memcpy(new_data, data(), m_size + 1);
 
 		if (has_sso())
-			m_storage = GeneralStorage();
+		{
+			m_storage.general_storage = GeneralStorage();
+			m_has_sso = false;
+		}
 		else
-			deallocator(m_storage.get<GeneralStorage>().data);
+			deallocator(m_storage.general_storage.data);
 
-		auto& storage = m_storage.get<GeneralStorage>();
+		auto& storage = m_storage.general_storage;
 		storage.capacity = new_size;
 		storage.data = new_data;
 
@@ -264,7 +263,7 @@ namespace BAN
 
 	bool String::has_sso() const
 	{
-		return m_storage.has<SSOStorage>();
+		return m_has_sso;
 	}
 
 }

BAN/include/BAN/String.h

@@ -82,17 +82,21 @@ namespace BAN
 	private:
 		struct SSOStorage
 		{
-			char storage[sso_capacity + 1] {};
+			char data[sso_capacity + 1] {};
 		};
 		struct GeneralStorage
 		{
-			size_type capacity { 0 };
-			char* data;
+			size_type capacity	{ 0 };
+			char* data			{ nullptr };
 		};
 
 	private:
-		Variant<SSOStorage, GeneralStorage>	m_storage	{ SSOStorage() };
-		size_type							m_size		{ 0 };
+		union {
+			SSOStorage sso_storage;
+			GeneralStorage general_storage;
+		} m_storage										{ .sso_storage = SSOStorage() };
+		size_type m_size	: sizeof(size_type) * 8 - 1	{ 0 };
+		size_type m_has_sso	: 1							{ true };
 	};
 
 	template<typename... Args>