Core: Add EmptyStream class

ChangeLog.md

@@ -212,6 +212,7 @@ Nazara Engine:
 - Added ENetPeer::GetTotalByte[Received|Sent]
 - Added ENetPeer::GetTotalPacketSent
 - ⚠ ENetHost::GetTotalReceivedPackets now returns the number of commands received (instead of the number of UDP packets received)
+- Added EmptyStream class, useful to measure how many bytes some writing operations will take
 
 Nazara Development Kit:
 - Added ImageWidget (#139)

include/Nazara/Core/EmptyStream.hpp

@@ -0,0 +1,46 @@
+// Copyright (C) 2019 Jérôme Leclercq
+// This file is part of the "Nazara Engine - Core module"
+// For conditions of distribution and use, see copyright notice in Config.hpp
+
+#pragma once
+
+#ifndef NAZARA_EMPTYSTREAM_HPP
+#define NAZARA_EMPTYSTREAM_HPP
+
+#include <Nazara/Prerequisites.hpp>
+#include <Nazara/Core/Stream.hpp>
+
+namespace Nz
+{
+	class NAZARA_CORE_API EmptyStream : public Stream
+	{
+		public:
+			inline EmptyStream();
+			EmptyStream(const EmptyStream&) = default;
+			EmptyStream(EmptyStream&&) noexcept = default;
+			~EmptyStream() = default;
+
+			void Clear();
+
+			bool EndOfStream() const override;
+
+			UInt64 GetCursorPos() const override;
+			UInt64 GetSize() const override;
+
+			bool SetCursorPos(UInt64 offset) override;
+
+			EmptyStream& operator=(const EmptyStream&) = default;
+			EmptyStream& operator=(EmptyStream&&) noexcept = default;
+
+		private:
+			void FlushStream() override;
+			std::size_t ReadBlock(void* buffer, std::size_t size) override;
+			std::size_t WriteBlock(const void* buffer, std::size_t size) override;
+
+			UInt64 m_size;
+	};
+}
+
+#include <Nazara/Core/EmptyStream.inl>
+
+#endif // NAZARA_EMPTYSTREAM_HPP

include/Nazara/Core/EmptyStream.inl

@@ -0,0 +1,22 @@
+// Copyright (C) 2019 Jérôme Leclercq
+// This file is part of the "Nazara Engine - Core module"
+// For conditions of distribution and use, see copyright notice in Config.hpp
+
+#include <Nazara/Core/EmptyStream.hpp>
+#include <Nazara/Core/Debug.hpp>
+
+namespace Nz
+{
+	/*!
+	* \ingroup core
+	* \class Nz::EmptyStream
+	* \brief Constructs an EmptyStream object by default
+	*/
+	inline EmptyStream::EmptyStream() :
+	m_size(0)
+	{
+	}
+
+}
+
+#include <Nazara/Core/DebugOff.hpp>

src/Nazara/Core/EmptyStream.cpp

@@ -0,0 +1,99 @@
+// Copyright (C) 2019 Jérôme Leclercq
+// This file is part of the "Nazara Engine - Core module"
+// For conditions of distribution and use, see copyright notice in Config.hpp
+
+#include <Nazara/Core/EmptyStream.hpp>
+#include <algorithm>
+#include <cstring>
+#include <Nazara/Core/Debug.hpp>
+
+namespace Nz
+{
+	/*!
+	* \ingroup core
+	* \class Nz::EmptyStream
+	* \brief Core class that simulate an empty buffer (discarding all content) which can be used to measure size
+	*/
+
+	/*!
+	* \brief Resets the stream size to zero
+	*/
+	void EmptyStream::Clear()
+	{
+		m_size = 0;
+	}
+
+	/*!
+	* \brief Checks whether the stream reached the end of the stream
+	* \return Always false
+	*/
+	bool EmptyStream::EndOfStream() const
+	{
+		return false;
+	}
+
+	/*!
+	* \brief Gets the position of the cursor (which is always zero)
+	* \return Always zero
+	*/
+	UInt64 EmptyStream::GetCursorPos() const
+	{
+		return 0;
+	}
+
+	/*!
+	* \brief Gets the size of the raw memory (how many bytes would have been written on a regular stream)
+	* \return Size occupied until now
+	*/
+	UInt64 EmptyStream::GetSize() const
+	{
+		return m_size;
+	}
+
+	/*!
+	* \brief Does nothing
+	* \return true
+	*
+	* \param offset Offset according to the beginning of the stream
+	*/
+	bool EmptyStream::SetCursorPos(UInt64 offset)
+	{
+		return true;
+	}
+
+	/*!
+	* \brief Flushes the stream (does nothing)
+	*/
+	void EmptyStream::FlushStream()
+	{
+		// Nothing to flush
+	}
+
+	/*!
+	* \brief Reads data
+	* \return Number of byte read (always zero)
+	*
+	* Reading from an empty stream does nothing and will always returns zero
+	*
+	* \param buffer Preallocated buffer to contain information read
+	* \param size Size of the read and thus of the buffer
+	*/
+	std::size_t EmptyStream::ReadBlock(void* buffer, std::size_t size)
+	{
+		return 0;
+	}
+
+	/*!
+	* \brief Writes data
+	* \return size
+	*
+	* \param buffer Dummy parameter
+	* \param size How many bytes will be "written"
+	*/
+	std::size_t EmptyStream::WriteBlock(const void* /*buffer*/, std::size_t size)
+	{
+		m_size += size;
+
+		return size;
+	}
+}