Use sendfile on Linux to optimize memory and improve latency #3277

Net/include/Poco/Net/SocketImpl.h

@@ -182,6 +182,16 @@ class Net_API SocketImpl: public Poco::RefCountedObject
 		///
 		/// Always returns zero for platforms where not implemented.
 
+	virtual void sendFile(const std::string& filePath, const size_t fileSize);
+		/// Implemented only on Linux. Noop on other platforms.
+		///
+		/// Sends the given file via sendfile system call.
+		/// Blocks the calling thread until the file is sent or the connection
+		/// is closed by the client.
+		///
+		/// @param filePath [i] path of the file on file system.
+		/// @param fileSize [i] size of the file being sent.
+
 	virtual int receiveBytes(void* buffer, int length, int flags = 0);
 		/// Receives data from the socket and stores it
 		/// in buffer. Up to length bytes are received.

Net/include/Poco/Net/StreamSocket.h

@@ -198,6 +198,9 @@ class Net_API StreamSocket: public Socket
 		/// The flags parameter can be used to pass system-defined flags
 		/// for send() like MSG_OOB.
 
+	virtual void sendFile(const std::string& filePath, const size_t fileSize);
+		/// Sends the given file to the socket
+
 	int receiveBytes(void* buffer, int length, int flags = 0);
 		/// Receives data from the socket and stores it
 		/// in buffer. Up to length bytes are received.

Net/src/HTTPServerResponseImpl.cpp

@@ -11,7 +11,6 @@
 // SPDX-License-Identifier:	BSL-1.0
 //
 
-
 #include "Poco/Net/HTTPServerResponseImpl.h"
 #include "Poco/Net/HTTPServerRequestImpl.h"
 #include "Poco/Net/HTTPServerSession.h"
@@ -53,7 +52,8 @@ HTTPServerResponseImpl::HTTPServerResponseImpl(HTTPServerSession& session):
 
 HTTPServerResponseImpl::~HTTPServerResponseImpl()
 {
-	delete _pStream;
+	if (_pStream != 0)
+		delete _pStream;
 }
 
 
@@ -128,7 +128,15 @@ void HTTPServerResponseImpl::sendFile(const std::string& path, const std::string
 		write(*_pStream);
 		if (_pRequest && _pRequest->getMethod() != HTTPRequest::HTTP_HEAD)
 		{
+#if (POCO_OS == POCO_OS_LINUX)
+			// delete the stream to flush the HTTP headers to the socket, required by HTTP 1.0 and above
+			delete _pStream;
+			_pStream = 0;
+			// send the file via socket handle
+			_session.socket().sendFile(path, length);
+#else
 			StreamCopier::copyStream(istr, *_pStream);
+#endif
 		}
 	}
 	else throw OpenFileException(path);

Net/src/SocketImpl.cpp

@@ -12,6 +12,14 @@
 //
 
 
+#ifdef __linux__
+#include <fcntl.h>
+#include <sys/sendfile.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <iostream>
+#endif
+
 #include "Poco/Net/SocketImpl.h"
 #include "Poco/Net/NetException.h"
 #include "Poco/Net/StreamSocketImpl.h"
@@ -370,6 +378,26 @@ int SocketImpl::sendBytes(const SocketBufVec& buffers, int flags)
 }
 
 
+void SocketImpl::sendFile(const std::string& filePath, const size_t fileSize)
+{
+#if (POCO_OS == POCO_OS_LINUX)
+	int filefd = ::open(filePath.data(), O_RDONLY);
+	size_t remaining = fileSize;
+	while (remaining > 0)
+	{
+		ssize_t sent = ::sendfile64(_sockfd, filefd, 0, remaining);
+		if (sent >= 0)
+			remaining -= sent;
+		else
+			break;
+	}
+	// instruct the kernel to drop the file cache
+	::posix_fadvise(filefd, 0, 0, POSIX_FADV_DONTNEED);
+	::close(filefd);
+#endif
+}
+
+
 int SocketImpl::receiveBytes(void* buffer, int length, int flags)
 {
 	checkBrokenTimeout(SELECT_READ);

Net/src/StreamSocket.cpp

@@ -180,6 +180,12 @@ int StreamSocket::sendBytes(FIFOBuffer& fifoBuf)
 }
 
 
+void StreamSocket::sendFile(const std::string& filePath, const size_t fileSize)
+{
+	impl()->sendFile(filePath, fileSize);
+}
+
+
 int StreamSocket::receiveBytes(void* buffer, int length, int flags)
 {
 	return impl()->receiveBytes(buffer, length, flags);