fs/io/FileOutputStream: merge all classes into one, add enum Mode

src/PlaylistFile.cxx

@@ -199,7 +199,6 @@ SavePlaylistFile(const PlaylistFileContents &contents, const char *utf8path)
 	assert(!path_fs.IsNull());
 
 	FileOutputStream fos(path_fs);
-
 	BufferedOutputStream bos(fos);
 
 	for (const auto &uri_utf8 : contents)
@@ -354,7 +353,7 @@ try {
 	const auto path_fs = spl_map_to_fs(utf8path);
 	assert(!path_fs.IsNull());
 
-	AppendFileOutputStream fos(path_fs);
+	FileOutputStream fos(path_fs, FileOutputStream::Mode::APPEND_EXISTING);
 
 	if (fos.Tell() / (MPD_PATH_MAX + 1) >= playlist_max_length)
 		throw PlaylistError(PlaylistResult::TOO_LARGE,

src/fs/io/FileOutputStream.cxx

@@ -21,22 +21,56 @@
 #include "FileOutputStream.hxx"
 #include "system/Error.hxx"
 
+FileOutputStream::FileOutputStream(Path _path, Mode _mode)
+	:path(_path), mode(_mode)
+{
+	switch (mode) {
+	case Mode::CREATE:
+		OpenCreate();
+		break;
+
+	case Mode::APPEND_EXISTING:
+		OpenAppendExisting();
+		break;
+	}
+}
+
 #ifdef WIN32
 
-FileOutputStream::FileOutputStream(Path _path)
-	:BaseFileOutputStream(_path)
+inline void
+FileOutputStream::OpenCreate()
 {
-	SetHandle(CreateFile(_path.c_str(), GENERIC_WRITE, 0, nullptr,
-			     CREATE_ALWAYS,
-			     FILE_ATTRIBUTE_NORMAL|FILE_FLAG_WRITE_THROUGH,
-			     nullptr));
+	handle = CreateFile(path.c_str(), GENERIC_WRITE, 0, nullptr,
+			    CREATE_ALWAYS,
+			    FILE_ATTRIBUTE_NORMAL|FILE_FLAG_WRITE_THROUGH,
+			    nullptr);
 	if (!IsDefined())
 		throw FormatLastError("Failed to create %s",
-				      GetPath().ToUTF8().c_str());
+				      path.ToUTF8().c_str());
+}
+
+inline void
+FileOutputStream::OpenAppendExisting()
+{
+	handle = CreateFile(path.c_str(), GENERIC_WRITE, 0, nullptr,
+			    OPEN_EXISTING,
+			    FILE_ATTRIBUTE_NORMAL|FILE_FLAG_WRITE_THROUGH,
+			    nullptr);
+	if (!IsDefined())
+		throw FormatLastError("Failed to append to %s",
+				      path.ToUTF8().c_str());
+
+	if (!SeekEOF()) {
+		auto code = GetLastError();
+		Close();
+		throw FormatLastError(code, "Failed seek end-of-file of %s",
+				      path.ToUTF8().c_str());
+	}
+
 }
 
 uint64_t
-BaseFileOutputStream::Tell() const
+FileOutputStream::Tell() const
 {
 	LONG high = 0;
 	DWORD low = SetFilePointer(handle, 0, &high, FILE_CURRENT);
@@ -47,7 +81,7 @@ BaseFileOutputStream::Tell() const
 }
 
 void
-BaseFileOutputStream::Write(const void *data, size_t size)
+FileOutputStream::Write(const void *data, size_t size)
 {
 	assert(IsDefined());
 
@@ -108,18 +142,18 @@ OpenTempFile(FileDescriptor &fd, Path path)
 
 #endif /* HAVE_LINKAT */
 
-FileOutputStream::FileOutputStream(Path _path)
-	:BaseFileOutputStream(_path)
+inline void
+FileOutputStream::OpenCreate()
 {
 #ifdef HAVE_LINKAT
 	/* try Linux's O_TMPFILE first */
-	is_tmpfile = OpenTempFile(SetFD(), GetPath());
+	is_tmpfile = OpenTempFile(fd, GetPath());
 	if (!is_tmpfile) {
 #endif
 		/* fall back to plain POSIX */
-		if (!SetFD().Open(GetPath().c_str(),
-				  O_WRONLY|O_CREAT|O_TRUNC,
-				  0666))
+		if (!fd.Open(GetPath().c_str(),
+			     O_WRONLY|O_CREAT|O_TRUNC,
+			     0666))
 			throw FormatErrno("Failed to create %s",
 					  GetPath().c_str());
 #ifdef HAVE_LINKAT
@@ -127,14 +161,22 @@ FileOutputStream::FileOutputStream(Path _path)
 #endif
 }
 
+inline void
+FileOutputStream::OpenAppendExisting()
+{
+	if (!fd.Open(path.c_str(), O_WRONLY|O_APPEND))
+		throw FormatErrno("Failed to append to %s",
+				  path.c_str());
+}
+
 uint64_t
-BaseFileOutputStream::Tell() const
+FileOutputStream::Tell() const
 {
 	return fd.Tell();
 }
 
 void
-BaseFileOutputStream::Write(const void *data, size_t size)
+FileOutputStream::Write(const void *data, size_t size)
 {
 	assert(IsDefined());
 
@@ -158,20 +200,20 @@ FileOutputStream::Commit()
 		/* hard-link the temporary file to the final path */
 		char fd_path[64];
 		snprintf(fd_path, sizeof(fd_path), "/proc/self/fd/%d",
-			 GetFD().Get());
-		if (linkat(AT_FDCWD, fd_path, AT_FDCWD, GetPath().c_str(),
+			 fd.Get());
+		if (linkat(AT_FDCWD, fd_path, AT_FDCWD, path.c_str(),
 			   AT_SYMLINK_FOLLOW) < 0)
 			throw FormatErrno("Failed to commit %s",
-					  GetPath().c_str());
+					  path.c_str());
 	}
 #endif
 
 	if (!Close()) {
 #ifdef WIN32
 		throw FormatLastError("Failed to commit %s",
-				      GetPath().ToUTF8().c_str());
+				      path.ToUTF8().c_str());
 #else
-		throw FormatErrno("Failed to commit %s", GetPath().c_str());
+		throw FormatErrno("Failed to commit %s", path.c_str());
 #endif
 	}
 }
@@ -183,51 +225,18 @@ FileOutputStream::Cancel()
 
 	Close();
 
+	switch (mode) {
+	case Mode::CREATE:
 #ifdef HAVE_LINKAT
-	if (!is_tmpfile)
-#endif
-		unlink(GetPath().c_str());
-}
-
+		if (!is_tmpfile)
 #endif
+			unlink(GetPath().c_str());
+		break;
 
-AppendFileOutputStream::AppendFileOutputStream(Path _path)
-	:BaseFileOutputStream(_path)
-{
-#ifdef WIN32
-	SetHandle(CreateFile(GetPath().c_str(), GENERIC_WRITE, 0, nullptr,
-			     OPEN_EXISTING,
-			     FILE_ATTRIBUTE_NORMAL|FILE_FLAG_WRITE_THROUGH,
-			     nullptr));
-	if (!IsDefined())
-		throw FormatLastError("Failed to append to %s",
-				      GetPath().ToUTF8().c_str());
-
-	if (!SeekEOF()) {
-		auto code = GetLastError();
-		Close();
-		throw FormatLastError(code, "Failed seek end-of-file of %s",
-				      GetPath().ToUTF8().c_str());
+	case Mode::APPEND_EXISTING:
+		/* can't roll this back */
+		break;
 	}
-#else
-	if (!SetFD().Open(GetPath().c_str(),
-			  O_WRONLY|O_APPEND))
-		throw FormatErrno("Failed to append to %s",
-				  GetPath().c_str());
-#endif
 }
 
-void
-AppendFileOutputStream::Commit()
-{
-	assert(IsDefined());
-
-	if (!Close()) {
-#ifdef WIN32
-		throw FormatLastError("Failed to commit %s",
-				      GetPath().ToUTF8().c_str());
-#else
-		throw FormatErrno("Failed to commit %s", GetPath().c_str());
 #endif
-	}
-}

src/fs/io/FileOutputStream.hxx

@@ -38,7 +38,7 @@
 
 class Path;
 
-class BaseFileOutputStream : public OutputStream {
+class FileOutputStream final : public OutputStream {
 	const AllocatedPath path;
 
 #ifdef WIN32
@@ -47,40 +47,58 @@ class BaseFileOutputStream : public OutputStream {
 	FileDescriptor fd = FileDescriptor::Undefined();
 #endif
 
-protected:
-#ifdef WIN32
-	template<typename P>
-	BaseFileOutputStream(P &&_path)
-		:path(std::forward<P>(_path)) {}
-#else
-	template<typename P>
-	BaseFileOutputStream(P &&_path)
-		:path(std::forward<P>(_path)) {}
+#ifdef HAVE_LINKAT
+	/**
+	 * Was O_TMPFILE used?  If yes, then linkat() must be used to
+	 * create a link to this file.
+	 */
+	bool is_tmpfile = false;
 #endif
 
-	~BaseFileOutputStream() {
-		assert(!IsDefined());
-	}
-
-#ifdef WIN32
-	void SetHandle(HANDLE _handle) {
-		assert(!IsDefined());
+public:
+	enum class Mode : uint8_t {
+		/**
+		 * Create a new file, or replace an existing file.
+		 * File contents may not be visible until Commit() has
+		 * been called.
+		 */
+		CREATE,
+
+		/**
+		 * Append to a file that already exists.  If it does
+		 * not, an exception is thrown.
+		 */
+		APPEND_EXISTING,
+	};
+
+private:
+	Mode mode;
 
-		handle = _handle;
+public:
+	FileOutputStream(Path _path, Mode _mode=Mode::CREATE);
 
-		assert(IsDefined());
+	~FileOutputStream() {
+		if (IsDefined())
+			Cancel();
 	}
-#else
-	FileDescriptor &SetFD() {
-		assert(!IsDefined());
 
-		return fd;
+public:
+	Path GetPath() const {
+		return path;
 	}
 
-	const FileDescriptor &GetFD() const {
-		return fd;
-	}
-#endif
+	gcc_pure
+	uint64_t Tell() const;
+
+	/* virtual methods from class OutputStream */
+	void Write(const void *data, size_t size) override;
+
+	void Commit();
+	void Cancel();
+
+private:
+	void OpenCreate();
+	void OpenAppendExisting();
 
 	bool Close() {
 		assert(IsDefined());
@@ -108,50 +126,6 @@ protected:
 		return fd.IsDefined();
 #endif
 	}
-
-public:
-	Path GetPath() const {
-		return path;
-	}
-
-	gcc_pure
-	uint64_t Tell() const;
-
-	/* virtual methods from class OutputStream */
-	void Write(const void *data, size_t size) override;
-};
-
-class FileOutputStream final : public BaseFileOutputStream {
-#ifdef HAVE_LINKAT
-	/**
-	 * Was O_TMPFILE used?  If yes, then linkat() must be used to
-	 * create a link to this file.
-	 */
-	bool is_tmpfile;
-#endif
-
-public:
-	FileOutputStream(Path _path);
-
-	~FileOutputStream() {
-		if (IsDefined())
-			Cancel();
-	}
-
-	void Commit();
-	void Cancel();
-};
-
-class AppendFileOutputStream final : public BaseFileOutputStream {
-public:
-	AppendFileOutputStream(Path _path);
-
-	~AppendFileOutputStream() {
-		if (IsDefined())
-			Close();
-	}
-
-	void Commit();
 };
 
 #endif