path: root/src/fs/io/FileOutputStream.cxx

/*
 * Copyright (C) 2003-2015 The Music Player Daemon Project
 * http://www.musicpd.org
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include "config.h"
#include "FileOutputStream.hxx"
#include "fs/FileSystem.hxx"
#include "util/Error.hxx"

FileOutputStream *
FileOutputStream::Create(Path path, Error &error)
{
	FileOutputStream *f = new FileOutputStream(path, error);
	if (!f->IsDefined()) {
		delete f;
		f = nullptr;
	}

	return f;
}

#ifdef WIN32

FileOutputStream::FileOutputStream(Path _path, Error &error)
	:path(_path),
	 handle(CreateFile(path.c_str(), GENERIC_WRITE, 0, nullptr,
			   TRUNCATE_EXISTING,
			   FILE_ATTRIBUTE_NORMAL|FILE_FLAG_WRITE_THROUGH,
			   nullptr))
{
	if (handle == INVALID_HANDLE_VALUE)
		error.FormatLastError("Failed to create %s", path.c_str());
}

bool
FileOutputStream::Write(const void *data, size_t size, Error &error)
{
	assert(IsDefined());

	DWORD nbytes;
	if (!WriteFile(handle, data, size, &nbytes, nullptr)) {
		error.FormatLastError("Failed to write to %s", path.c_str());
		return false;
	}

	if (size_t(nbytes) != size) {
		error.FormatLastError(ERROR_DISK_FULL,
				      "Failed to write to %s", path.c_str());
		return false;
	}

	return true;
}

bool
FileOutputStream::Commit(gcc_unused Error &error)
{
	assert(IsDefined());

	CloseHandle(handle);
	handle = INVALID_HANDLE_VALUE;
	return true;
}

void
FileOutputStream::Cancel()
{
	assert(IsDefined());

	CloseHandle(handle);
	handle = INVALID_HANDLE_VALUE;
	RemoveFile(path);
}

#else

#include <fcntl.h>
#include <unistd.h>
#include <errno.h>

#ifdef HAVE_LINKAT
#ifndef O_TMPFILE
/* supported since Linux 3.11 */
#define __O_TMPFILE 020000000
#define O_TMPFILE (__O_TMPFILE | O_DIRECTORY)
#include <stdio.h>
#endif

/**
 * Open a file using Linux's O_TMPFILE for writing the given file.
 */
static int
OpenTempFile(Path path)
{
	const auto directory = path.GetDirectoryName();
	if (directory.IsNull())
		return -1;

	return OpenFile(directory, O_TMPFILE|O_WRONLY, 0666);
}

#endif /* HAVE_LINKAT */

FileOutputStream::FileOutputStream(Path _path, Error &error)
	:path(_path)
{
#ifdef HAVE_LINKAT
	/* try Linux's O_TMPFILE first */
	fd = OpenTempFile(path);
	is_tmpfile = fd >= 0;
	if (!is_tmpfile) {
#endif
		/* fall back to plain POSIX */
		fd = OpenFile(path,
			      O_WRONLY|O_CREAT|O_TRUNC,
			      0666);
		if (fd < 0)
			error.FormatErrno("Failed to create %s", path.c_str());
#ifdef HAVE_LINKAT
	}
#endif
}

bool
FileOutputStream::Write(const void *data, size_t size, Error &error)
{
	assert(IsDefined());

	ssize_t nbytes = write(fd, data, size);
	if (nbytes < 0) {
		error.FormatErrno("Failed to write to %s", path.c_str());
		return false;
	} else if ((size_t)nbytes < size) {
		error.FormatErrno(ENOSPC,
				  "Failed to write to %s", path.c_str());
		return false;
	}

	return true;
}

bool
FileOutputStream::Commit(Error &error)
{
	assert(IsDefined());

#if HAVE_LINKAT
	if (is_tmpfile) {
		RemoveFile(path);

		/* hard-link the temporary file to the final path */
		char fd_path[64];
		snprintf(fd_path, sizeof(fd_path), "/proc/self/fd/%d", fd);
		if (linkat(AT_FDCWD, fd_path, AT_FDCWD, path.c_str(),
			   AT_SYMLINK_FOLLOW) < 0) {
			error.FormatErrno("Failed to commit %s", path.c_str());
			close(fd);
			return false;
		}
	}
#endif

	bool success = close(fd) == 0;
	fd = -1;
	if (!success)
		error.FormatErrno("Failed to commit %s", path.c_str());

	return success;
}

void
FileOutputStream::Cancel()
{
	assert(IsDefined());

	close(fd);
	fd = -1;

#ifdef HAVE_LINKAT
	if (!is_tmpfile)
#endif
		RemoveFile(path);
}

#endif