Add new helper class for no-copy istream

src/Engine/CrossPlatform.cpp

@@ -1822,6 +1822,101 @@ static auto dummy = ([]
 
 	return 0;
 })();
+
+static auto dummyRawFile = ([]
+{
+	{
+		char text[] = "test";
+		StreamData raw(RawData{text, std::strlen(text), +[](void*){}});
+
+		assert(raw.get() == 't');
+		assert(raw.get() == 'e');
+		assert(raw.get() == 's');
+		assert(raw.get() == 't');
+		assert(raw.get() == std::char_traits<char>::eof());
+	}
+
+	{
+		char text[] = "test123";
+		StreamData raw(RawData{text, std::strlen(text), +[](void*){}});
+
+		char dummy1[10] = { };
+		assert(raw.read(dummy1, 4) && std::strcmp(dummy1, "test") == 0);
+
+		char dummy2[10] = { };
+		assert(raw.read(dummy2, 3) && std::strcmp(dummy2, "123") == 0);
+
+	}
+
+	{
+		char text[] = "test123";
+		StreamData raw(RawData{text, std::strlen(text), +[](void*){}});
+
+		char dummy1[10] = { };
+		assert(!raw.read(dummy1, 10) && std::strcmp(dummy1, "test123") == 0);
+	}
+
+	{
+		char text[] = "test123";
+		StreamData raw(RawData{text, std::strlen(text), +[](void*){}});
+
+		raw.seekg(0, std::ios::end);
+		std::streamoff end = raw.tellg();
+		raw.seekg(0, std::ios::beg);
+		std::streamoff begin = raw.tellg();
+
+		assert(end-begin == (int)std::strlen(text));
+	}
+
+	{
+		static int calledDelete = 0;
+		char text[] = "test123";
+		StreamData raw(RawData{text, std::strlen(text), +[](void*){ ++calledDelete; }});
+
+		assert(raw.get() == 't');
+
+		raw.extractRawData();
+
+		assert(raw.get() == std::char_traits<char>::eof());
+		assert(calledDelete == 1);
+	}
+
+	{
+		static int calledDelete = 0;
+		char text[] = "0123";
+		StreamData raw(RawData{text, std::strlen(text), +[](void*){ ++calledDelete; }});
+
+
+		assert(raw.get() == '0');
+
+		StreamData raw2 = std::move(raw);
+
+		assert(raw.get() ==  std::char_traits<char>::eof());
+		assert(!!raw2);
+		assert(raw2.get() == '1');
+
+		raw = std::move(raw2);
+
+		assert(raw.get() == '2');
+		assert(raw2.get() == std::char_traits<char>::eof());
+
+		assert(raw.get() == '3');
+		assert(!!raw);
+		assert(raw.get() == std::char_traits<char>::eof());
+		assert(!raw);
+
+		{
+			StreamData raw3 = std::move(raw);
+			assert(!raw3);
+
+			assert(calledDelete == 0);
+		}
+
+		assert(calledDelete == 1);
+	}
+
+	return 0;
+})();
 #endif
 
 

src/Engine/CrossPlatform.h

@@ -27,6 +27,139 @@
 namespace OpenXcom
 {
 
+using RawDataDeleteFun = void(*)(void*);
+
+/**
+ * Unique pointer with size to raw data buffer.
+ */
+class RawData
+{
+	std::unique_ptr<void, RawDataDeleteFun> _data;
+	std::size_t _size;
+
+
+public:
+
+	/// Default constructor.
+	RawData() : _data{ nullptr, +[](void*){} }, _size{ }
+	{
+
+	}
+
+	/// Create data from pointer and size.
+	RawData(void* data, std::size_t size, RawDataDeleteFun del) : _data{ data, del }, _size{ size }
+	{
+
+	}
+
+	/// Move constructor.
+	RawData(RawData&& d) : RawData()
+	{
+		*this = std::move(d);
+	}
+
+	/// Move assignment.
+	RawData& operator=(RawData&& d)
+	{
+		_data = std::exchange(d._data, std::unique_ptr<void, RawDataDeleteFun>{ nullptr, +[](void*){} });
+		_size = std::exchange(d._size, 0u);
+
+		return *this;
+	}
+
+
+	/// Size of buffer.
+	std::size_t size() const { return _size; }
+
+	/// Data of buffer.
+	const void* data() const { return _data.get(); }
+
+	/// Data of buffer.
+	void* data() { return _data.get(); }
+};
+
+/**
+ * Stream to raw data buffer, owning its data buffer.
+ */
+class StreamData : public std::istream, private std::streambuf
+{
+	RawData _data;
+
+
+public:
+
+	/// Default constructor.
+	StreamData()
+	{
+		this->rdbuf(this);
+	}
+
+	/// Constructor from raw data.
+	StreamData(RawData data) : StreamData()
+	{
+		insertRawData(std::move(data));
+	}
+
+	/// Move constructor, move whole state to new object.
+	StreamData(StreamData&& f) : StreamData()
+	{
+		*this = std::move(f);
+	}
+
+	/// Move assignment, move whole state to new object.
+	StreamData& operator=(StreamData&& f)
+	{
+		auto state = f.rdstate();
+		auto pos = f.tellg();
+		insertRawData(f.extractRawData());
+		this->seekg(pos);
+		this->clear(state);
+
+		return *this;
+	}
+
+
+	/// Move out raw data from object.
+	RawData extractRawData()
+	{
+		this->setg(nullptr, nullptr, nullptr);
+		return std::move(_data);
+	}
+
+	/// Insert raw data into object.
+	void insertRawData(RawData data)
+	{
+		_data = std::move(data);
+		this->setg((char*)_data.data(), (char*)_data.data(), (char*)_data.data() + _data.size());
+		this->clear();
+	}
+
+
+protected:
+
+	/// https://stackoverflow.com/questions/35066207/how-to-implement-custom-stdstreambufs-seekoff
+	virtual  std::streambuf::pos_type seekoff(
+		std::streambuf::off_type off, std::ios_base::seekdir dir,
+		std::ios_base::openmode) override
+	{
+		if (dir == std::ios_base::cur)
+			gbump(off);
+		else if (dir == std::ios_base::end)
+			setg(eback(), egptr() + off, egptr());
+		else if (dir == std::ios_base::beg)
+			setg(eback(), eback() + off, egptr());
+		return gptr() - eback();
+	}
+
+	/// https://stackoverflow.com/a/46069245/1938348
+	virtual std::streambuf::pos_type seekpos(
+		std::streambuf::pos_type pos,
+		std::ios_base::openmode which) override
+	{
+		return seekoff(pos - std::streambuf::pos_type(std::streambuf::off_type(0)), std::ios_base::beg, which);
+	}
+};
+
 /**
  * Generic purpose functions that need different
  * implementations for different platforms.