feature(FileStream): Allow using Poco::FileStream to wrap arbitrary file handles/descriptors as C++ streams (#4424)

* Allow using Poco::FileStream to wrap arbitrary file handles/descriptors as C++ streams (#3444).

* Allow opening a file descriptor/HANDLE as C++ stream.

* FileStream: treat read from closed pipe as EOF.

* chore(Filestream): conde style (naming)

Co-Authored-By: Alex Fabijanic <alex@pocoproject.org>
Co-Authored-By: Matej Kenda <matejken@gmail.com>

* enh(FileStream): make FileIOS::open a virtual function. (#3444)

* test(FileStream): unit test for FileStream::openHandle (#3444)

* Update CONTRIBUTORS.

* test(FileStream): Win32 unit test fix.

* build(CMake): Require policy minimum version 3.15.

---------

Co-authored-by: Daniel Grunwald <grunwald@axivion.com>
Co-authored-by: Alex Fabijanic <alex@pocoproject.org>

CMakeLists.txt

@@ -1,4 +1,5 @@
 cmake_minimum_required(VERSION 3.5.0)
+cmake_policy(VERSION 3.15.0)
 
 project(Poco)
 

CONTRIBUTORS

@@ -60,9 +60,11 @@ Friedrich Wilckens
 Pavle Dragišić
 Nino Belušić
 Kari Argillander
-Alexander B
+Alexander Bychuk
 Andrew Auclair
 Jochen Sprickerhof
 Jesse Hoogervorst
 Aron Budea
 zhuzeitou
+Daniel Grunwald
+

Foundation/include/Poco/FileStream.h

@@ -56,6 +56,16 @@ public:
 	~FileIOS();
 		/// Destroys the stream.
 
+	virtual void open(const std::string& path, std::ios::openmode mode);
+		/// Opens the file specified by path, using the given mode.
+		///
+		/// Throws a FileException (or a similar exception) if the file 
+		/// does not exist or is not accessible for other reasons and
+		/// a new file cannot be created.
+
+	void openHandle(NativeHandle handle, std::ios::openmode mode);
+		/// Takes ownership of the handle.
+
 	void close();
 		/// Closes the file stream.
 		///
@@ -108,7 +118,7 @@ public:
 	~FileInputStream();
 		/// Destroys the stream.
 
-	void open(const std::string& path, std::ios::openmode mode = std::ios::in);
+	void open(const std::string& path, std::ios::openmode mode = std::ios::in) override;
 		/// Opens the file specified by path, using the given mode, which
 		/// will always include std::ios::in (even if not specified).
 		///
@@ -151,7 +161,7 @@ public:
 	~FileOutputStream();
 		/// Destroys the FileOutputStream.
 
-	void open(const std::string& path, std::ios::openmode mode = std::ios::out | std::ios::trunc);
+	void open(const std::string& path, std::ios::openmode mode = std::ios::out | std::ios::trunc) override;
 		/// Opens the file specified by path, using the given mode, which
 		/// always includes std::ios::out, even if not specified.
 		///
@@ -196,7 +206,7 @@ public:
 	~FileStream();
 		/// Destroys the FileOutputStream.
 
-	void open(const std::string& path, std::ios::openmode mode = std::ios::out | std::ios::in);
+	void open(const std::string& path, std::ios::openmode mode = std::ios::out | std::ios::in) override;
 		/// Opens the file specified by path, using the given mode.
 		///
 		/// Throws a FileException (or a similar exception) if the file

Foundation/include/Poco/FileStream_POSIX.h

@@ -42,6 +42,9 @@ public:
 	void open(const std::string& path, std::ios::openmode mode);
 		/// Opens the given file in the given mode.
 
+	void openHandle(NativeHandle fd, std::ios::openmode mode);
+		/// Take ownership of the given file descriptor.
+
 	bool close();
 		/// Closes the File stream buffer. Returns true if successful,
 		/// false otherwise.

Foundation/include/Poco/FileStream_WIN32.h

@@ -41,6 +41,9 @@ public:
 	void open(const std::string& path, std::ios::openmode mode);
 		/// Opens the given file in the given mode.
 
+	void openHandle(NativeHandle handle, std::ios::openmode mode);
+		/// Take ownership of the given HANDLE.
+
 	bool close();
 		/// Closes the File stream buffer. Returns true if successful,
 		/// false otherwise.

Foundation/src/FileStream.cpp

@@ -35,6 +35,20 @@ FileIOS::~FileIOS()
 }
 
 
+void FileIOS::open(const std::string& path, std::ios::openmode mode)
+{
+	clear();
+	_buf.open(path, mode);
+}
+
+
+void FileIOS::openHandle(NativeHandle handle, std::ios::openmode mode)
+{
+	clear();
+	_buf.openHandle(handle, mode);
+}
+
+
 void FileIOS::close()
 {
 	if (!_buf.close())
@@ -77,7 +91,7 @@ FileInputStream::FileInputStream():
 FileInputStream::FileInputStream(const std::string& path, std::ios::openmode mode):
 	std::istream(&_buf)
 {
-	open(path, mode | std::ios::in);
+	open(path, mode);
 }
 
 
@@ -88,8 +102,7 @@ FileInputStream::~FileInputStream()
 
 void FileInputStream::open(const std::string& path, std::ios::openmode mode)
 {
-	clear();
-	_buf.open(path, mode | std::ios::in);
+	FileIOS::open(path, mode | std::ios::in);
 }
 
 
@@ -102,7 +115,7 @@ FileOutputStream::FileOutputStream():
 FileOutputStream::FileOutputStream(const std::string& path, std::ios::openmode mode):
 	std::ostream(&_buf)
 {
-	open(path, mode | std::ios::out);
+	open(path, mode);
 }
 
 
@@ -113,8 +126,7 @@ FileOutputStream::~FileOutputStream()
 
 void FileOutputStream::open(const std::string& path, std::ios::openmode mode)
 {
-	clear();
-	_buf.open(path, mode | std::ios::out);
+	FileIOS::open(path, mode | std::ios::out);
 }
 
 
@@ -138,8 +150,7 @@ FileStream::~FileStream()
 
 void FileStream::open(const std::string& path, std::ios::openmode mode)
 {
-	clear();
-	_buf.open(path, mode);
+	FileIOS::open(path, mode);
 }
 
 

Foundation/src/FileStream_POSIX.cpp

@@ -72,6 +72,22 @@ void FileStreamBuf::open(const std::string& path, std::ios::openmode mode)
 }
 
 
+void FileStreamBuf::openHandle(NativeHandle fd, std::ios::openmode mode)
+{
+	poco_assert(_fd == -1);
+	poco_assert(fd != -1);
+
+	_pos = 0;
+	setMode(mode);
+	resetBuffers();
+
+	_fd = fd;
+
+	if ((mode & std::ios::app) || (mode & std::ios::ate))
+		seekoff(0, std::ios::end, mode);
+}
+
+
 int FileStreamBuf::readFromDevice(char* buffer, std::streamsize length)
 {
 	if (_fd == -1) return -1;

Foundation/src/FileStream_WIN32.cpp

@@ -15,7 +15,6 @@
 #include "Poco/FileStream.h"
 #include "Poco/File.h"
 #include "Poco/Exception.h"
-#include "Poco/UnicodeConverter.h"
 
 
 namespace Poco {
@@ -74,6 +73,22 @@ void FileStreamBuf::open(const std::string& path, std::ios::openmode mode)
 }
 
 
+void FileStreamBuf::openHandle(NativeHandle handle, std::ios::openmode mode)
+{
+	poco_assert(_handle == INVALID_HANDLE_VALUE);
+	poco_assert(handle != INVALID_HANDLE_VALUE);
+
+	_pos = 0;
+	setMode(mode);
+	resetBuffers();
+
+	_handle = handle;
+
+	if ((mode & std::ios::ate) || (mode & std::ios::app))
+		seekoff(0, std::ios::end, mode);
+}
+
+
 int FileStreamBuf::readFromDevice(char* buffer, std::streamsize length)
 {
 	if (INVALID_HANDLE_VALUE == _handle || !(getMode() & std::ios::in))
@@ -85,7 +100,14 @@ int FileStreamBuf::readFromDevice(char* buffer, std::streamsize length)
 	DWORD bytesRead(0);
 	BOOL rc = ReadFile(_handle, buffer, static_cast<DWORD>(length), &bytesRead, NULL);
 	if (rc == 0)
+	{
+		if (GetLastError() == ERROR_BROKEN_PIPE)
+		{
+			// Read from closed pipe -> treat as EOF
+			return 0;
+		}
 		File::handleLastError(_path);
+	}
 
 	_pos += bytesRead;
 

Foundation/testsuite/src/FileStreamTest.cpp

@@ -51,6 +51,54 @@ void FileStreamTest::testRead()
 }
 
 
+#if defined(POCO_OS_FAMILY_WINDOWS)
+#include "Poco/UnicodeConverter.h"
+#else
+#include <fcntl.h>
+#endif
+
+void FileStreamTest::testWriteReadNativeHandle()
+{
+	Poco::FileOutputStream fos;
+	Poco::FileInputStream fis;
+	Poco::FileIOS::NativeHandle outHandle;
+
+#if defined(POCO_OS_FAMILY_WINDOWS)
+	char tmp[]={'\xc3', '\x84', '\xc3', '\x96', '\xc3', '\x9c', '\xc3', '\xa4', '\xc3', '\xb6', '\xc3', '\xbc', '\0'};
+	std::string file(tmp);
+	file.append(".txt");
+	std::wstring utf16Path;
+	Poco::UnicodeConverter::toUTF16(file, utf16Path);
+    outHandle = CreateFileW(utf16Path.c_str(), GENERIC_WRITE, FILE_SHARE_WRITE | FILE_SHARE_WRITE, nullptr, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, nullptr);
+    assertTrue(outHandle != INVALID_HANDLE_VALUE);
+#else
+	std::string file("testfile.txt");
+	outHandle = ::open(file.c_str(), O_WRONLY, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH);
+#endif
+
+	Poco::TemporaryFile::registerForDeletion(file);
+
+    fos.openHandle(outHandle, std::ios::binary | std::ios::out | std::ios::trunc);
+	fos << "sometestdata";
+	fos.close();
+
+    Poco::FileIOS::NativeHandle inHandle;
+
+#if defined(POCO_OS_FAMILY_WINDOWS)
+    inHandle = CreateFileW(utf16Path.c_str(), GENERIC_READ, FILE_SHARE_READ, nullptr, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nullptr);
+    assertTrue(inHandle != INVALID_HANDLE_VALUE);
+#else
+    inHandle = ::open(file.c_str(), O_RDONLY, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH);
+#endif
+
+	fis.openHandle(inHandle, std::ios::in);
+	assertTrue (fis.good());
+	std::string read;
+	fis >> read;
+	assertTrue (!read.empty());
+}
+
+
 void FileStreamTest::testWrite()
 {
 #if defined(POCO_OS_FAMILY_WINDOWS)
@@ -304,6 +352,7 @@ CppUnit::Test* FileStreamTest::suite()
 	CppUnit::TestSuite* pSuite = new CppUnit::TestSuite("FileStreamTest");
 
 	CppUnit_addTest(pSuite, FileStreamTest, testRead);
+	CppUnit_addTest(pSuite, FileStreamTest, testWriteReadNativeHandle);
 	CppUnit_addTest(pSuite, FileStreamTest, testWrite);
 	CppUnit_addTest(pSuite, FileStreamTest, testReadWrite);
 	CppUnit_addTest(pSuite, FileStreamTest, testOpen);

Foundation/testsuite/src/FileStreamTest.h

@@ -25,6 +25,7 @@ public:
 	~FileStreamTest();
 
 	void testRead();
+	void testWriteReadNativeHandle();
 	void testWrite();
 	void testReadWrite();
 	void testOpen();