enh(FileStream): Add FileStreamBuf::resizeBuffer to set larger internal buffers. (#4621)

Larger buffers improve performance significantly when streaming large quantity of data on very fast devices.

Foundation/include/Poco/BufferedBidirectionalStreamBuf.h

@@ -43,15 +43,15 @@ class BasicBufferedBidirectionalStreamBuf: public std::basic_streambuf<ch, tr>
 	/// for implementing an iostream.
 {
 protected:
-	typedef std::basic_streambuf<ch, tr> Base;
-	typedef std::basic_ios<ch, tr> IOS;
-	typedef ch char_type;
-	typedef tr char_traits;
-	typedef ba Allocator;
-	typedef typename Base::int_type int_type;
-	typedef typename Base::pos_type pos_type;
-	typedef typename Base::off_type off_type;
-	typedef typename IOS::openmode openmode;
+	using Base = std::basic_streambuf<ch, tr>;
+	using IOS = std::basic_ios<ch, tr>;
+	using char_type = ch;
+	using char_traits = tr;
+	using Allocator = ba;
+	using int_type = typename Base::int_type;
+	using pos_type = typename Base::pos_type;
+	using off_type = typename Base::off_type;
+	using openmode = typename IOS::openmode;
 
 public:
 	BasicBufferedBidirectionalStreamBuf(std::streamsize bufferSize, openmode mode):
@@ -69,6 +69,9 @@ public:
 		Allocator::deallocate(_pWriteBuffer, _bufsize);
 	}
 
+	BasicBufferedBidirectionalStreamBuf(const BasicBufferedBidirectionalStreamBuf&) = delete;
+	BasicBufferedBidirectionalStreamBuf& operator = (const BasicBufferedBidirectionalStreamBuf&) = delete;
+
 	virtual int_type overflow(int_type c)
 	{
 		if (!(_mode & IOS::out)) return char_traits::eof();
@@ -130,6 +133,22 @@ protected:
 		this->setp(_pWriteBuffer, _pWriteBuffer + _bufsize);
 	}
 
+	virtual bool resizeBuffer(std::streamsize bufferSize)
+	{
+		if (_bufsize != bufferSize)
+		{
+			Allocator::deallocate(_pReadBuffer, _bufsize);
+			Allocator::deallocate(_pWriteBuffer, _bufsize);
+
+			_bufsize = bufferSize;
+			_pReadBuffer = Allocator::allocate(_bufsize);
+			_pWriteBuffer = Allocator::allocate(_bufsize);
+		}
+		resetBuffers();
+
+		return true;
+	}
+
 private:
 	virtual int readFromDevice(char_type* /*buffer*/, std::streamsize /*length*/)
 	{
@@ -152,13 +171,10 @@ private:
 		return -1;
 	}
 
-	std::streamsize _bufsize;
-	char_type*      _pReadBuffer;
-	char_type*      _pWriteBuffer;
-	openmode        _mode;
-
-	BasicBufferedBidirectionalStreamBuf(const BasicBufferedBidirectionalStreamBuf&);
-	BasicBufferedBidirectionalStreamBuf& operator = (const BasicBufferedBidirectionalStreamBuf&);
+	std::streamsize _bufsize {0};
+	char_type*      _pReadBuffer {nullptr};
+	char_type*      _pWriteBuffer {nullptr};
+	openmode        _mode {0};
 };
 
 
@@ -172,8 +188,8 @@ private:
 #if defined(_MSC_VER) && defined(POCO_DLL) && !defined(Foundation_EXPORTS)
 template class Foundation_API BasicBufferedBidirectionalStreamBuf<char, std::char_traits<char>>;
 #endif
-typedef BasicBufferedBidirectionalStreamBuf<char, std::char_traits<char>> BufferedBidirectionalStreamBuf;
-
+using BufferedBidirectionalStreamBuf
+	= BasicBufferedBidirectionalStreamBuf<char, std::char_traits<char>>;
 
 } // namespace Poco
 

Foundation/include/Poco/FileStream.h

@@ -53,7 +53,7 @@ public:
 	FileIOS();
 		/// Creates the basic stream.
 
-	~FileIOS();
+	~FileIOS() override;
 		/// Destroys the stream.
 
 	virtual void open(const std::string& path, std::ios::openmode mode);
@@ -115,7 +115,7 @@ public:
 		/// Throws a FileNotFoundException (or a similar exception) if the file
 		/// does not exist or is not accessible for other reasons.
 
-	~FileInputStream();
+	~FileInputStream() override;
 		/// Destroys the stream.
 
 	void open(const std::string& path, std::ios::openmode mode = std::ios::in) override;
@@ -158,7 +158,7 @@ public:
 		/// for std::ofstream, which is std::ios::out only. This is for backwards compatibility
 		/// with earlier POCO versions.
 
-	~FileOutputStream();
+	~FileOutputStream() override;
 		/// Destroys the FileOutputStream.
 
 	void open(const std::string& path, std::ios::openmode mode = std::ios::out | std::ios::trunc) override;
@@ -203,7 +203,7 @@ public:
 		/// for std::fstream, which is std::ios::out only. This is for backwards compatibility
 		/// with earlier POCO versions.
 
-	~FileStream();
+	~FileStream() override;
 		/// Destroys the FileOutputStream.
 
 	void open(const std::string& path, std::ios::openmode mode = std::ios::out | std::ios::in) override;

Foundation/include/Poco/FileStream_POSIX.h

@@ -36,7 +36,7 @@ public:
 	FileStreamBuf();
 		/// Creates a FileStreamBuf.
 
-	~FileStreamBuf();
+	~FileStreamBuf() override;
 		/// Destroys the FileStream.
 
 	void open(const std::string& path, std::ios::openmode mode);
@@ -49,10 +49,16 @@ public:
 		/// Closes the File stream buffer. Returns true if successful,
 		/// false otherwise.
 
-	std::streampos seekoff(std::streamoff off, std::ios::seekdir dir, std::ios::openmode mode = std::ios::in | std::ios::out);
+	bool resizeBuffer(std::streamsize bufferSize) override;
+		/// Resizes internal buffer. Minimum size is BUFFER_SIZE.
+		/// Minimum is used when requested size is smaller.
+		/// Buffer can be resized only when the file is not open.
+		/// Returns true if resize succeeded.
+
+	std::streampos seekoff(std::streamoff off, std::ios::seekdir dir, std::ios::openmode mode = std::ios::in | std::ios::out) override;
 		/// Change position by offset, according to way and mode.
 
-	std::streampos seekpos(std::streampos pos, std::ios::openmode mode = std::ios::in | std::ios::out);
+	std::streampos seekpos(std::streampos pos, std::ios::openmode mode = std::ios::in | std::ios::out) override;
 		/// Change to specified position, according to mode.
 
 	void flushToDisk();
@@ -70,13 +76,13 @@ protected:
 		BUFFER_SIZE = 4096
 	};
 
-	int readFromDevice(char* buffer, std::streamsize length);
-	int writeToDevice(const char* buffer, std::streamsize length);
+	int readFromDevice(char* buffer, std::streamsize length) override;
+	int writeToDevice(const char* buffer, std::streamsize length) override;
 
 private:
 	std::string _path;
 	NativeHandle _fd;
-	std::streamoff _pos;
+	std::streamoff _pos {0};
 };
 
 

Foundation/include/Poco/FileStream_WIN32.h

@@ -25,7 +25,6 @@
 
 namespace Poco {
 
-
 class Foundation_API FileStreamBuf: public BufferedBidirectionalStreamBuf
 	/// This stream buffer handles Fileio
 {
@@ -48,10 +47,16 @@ public:
 		/// Closes the File stream buffer. Returns true if successful,
 		/// false otherwise.
 
-	std::streampos seekoff(std::streamoff off, std::ios::seekdir dir, std::ios::openmode mode = std::ios::in | std::ios::out);
+	bool resizeBuffer(std::streamsize bufferSize) override;
+		/// Resizes internal buffer. Minimum size is BUFFER_SIZE.
+		/// Minimum is used when requested size is smaller.
+		/// Buffer can be resized only when the file is not open.
+		/// Returns true if resize succeeded.
+
+	std::streampos seekoff(std::streamoff off, std::ios::seekdir dir, std::ios::openmode mode = std::ios::in | std::ios::out) override;
 		/// change position by offset, according to way and mode
 
-	std::streampos seekpos(std::streampos pos, std::ios::openmode mode = std::ios::in | std::ios::out);
+	std::streampos seekpos(std::streampos pos, std::ios::openmode mode = std::ios::in | std::ios::out) override;
 		/// change to specified position, according to mode
 
 	void flushToDisk();
@@ -69,13 +74,13 @@ protected:
 		BUFFER_SIZE = 4096
 	};
 
-	int readFromDevice(char* buffer, std::streamsize length);
-	int writeToDevice(const char* buffer, std::streamsize length);
+	int readFromDevice(char* buffer, std::streamsize length) override;
+	int writeToDevice(const char* buffer, std::streamsize length) override;
 
 private:
 	std::string _path;
 	NativeHandle _handle;
-	UInt64 _pos;
+	UInt64 _pos {0};
 };