1 files changed, 123 insertions, 0 deletions
diff --git a/lib/base/atomic-file.cpp b/lib/base/atomic-file.cpp
new file mode 100644
index 0000000..762f384
--- /dev/null
+++ b/lib/base/atomic-file.cpp
@@ -0,0 +1,123 @@
+/* Icinga 2 | (c) 2022 Icinga GmbH | GPLv2+ */
+
+#include "base/atomic-file.hpp"
+#include "base/exception.hpp"
+#include "base/utility.hpp"
+#include <utility>
+
+#ifdef _WIN32
+#	include <io.h>
+#	include <windows.h>
+#else /* _WIN32 */
+#	include <errno.h>
+#	include <unistd.h>
+#endif /* _WIN32 */
+
+using namespace icinga;
+
+void AtomicFile::Write(String path, int mode, const String& content)
+{
+	AtomicFile af (path, mode);
+	af << content;
+	af.Commit();
+}
+
+AtomicFile::AtomicFile(String path, int mode) : m_Path(std::move(path))
+{
+	m_TempFilename = m_Path + ".tmp.XXXXXX";
+
+#ifdef _WIN32
+	m_Fd = Utility::MksTemp(&m_TempFilename[0]);
+#else /* _WIN32 */
+	m_Fd = mkstemp(&m_TempFilename[0]);
+#endif /* _WIN32 */
+
+	if (m_Fd < 0) {
+		auto error (errno);
+
+		BOOST_THROW_EXCEPTION(posix_error()
+			<< boost::errinfo_api_function("mkstemp")
+			<< boost::errinfo_errno(error)
+			<< boost::errinfo_file_name(m_TempFilename));
+	}
+
+	try {
+		exceptions(failbit | badbit);
+
+		open(boost::iostreams::file_descriptor(
+			m_Fd,
+			// Rationale: https://github.com/boostorg/iostreams/issues/152
+			boost::iostreams::never_close_handle
+		));
+
+		if (chmod(m_TempFilename.CStr(), mode) < 0) {
+			auto error (errno);
+
+			BOOST_THROW_EXCEPTION(posix_error()
+				<< boost::errinfo_api_function("chmod")
+				<< boost::errinfo_errno(error)
+				<< boost::errinfo_file_name(m_TempFilename));
+		}
+	} catch (...) {
+		if (is_open()) {
+			close();
+		}
+
+		(void)::close(m_Fd);
+		(void)unlink(m_TempFilename.CStr());
+		throw;
+	}
+}
+
+AtomicFile::~AtomicFile()
+{
+	if (is_open()) {
+		try {
+			close();
+		} catch (...) {
+			// Destructor must not throw
+		}
+	}
+
+	if (m_Fd >= 0) {
+		(void)::close(m_Fd);
+	}
+
+	if (!m_TempFilename.IsEmpty()) {
+		(void)unlink(m_TempFilename.CStr());
+	}
+}
+
+void AtomicFile::Commit()
+{
+	flush();
+
+	auto h ((*this)->handle());
+
+#ifdef _WIN32
+	if (!FlushFileBuffers(h)) {
+		auto err (GetLastError());
+
+		BOOST_THROW_EXCEPTION(win32_error()
+			<< boost::errinfo_api_function("FlushFileBuffers")
+			<< errinfo_win32_error(err)
+			<< boost::errinfo_file_name(m_TempFilename));
+	}
+#else /* _WIN32 */
+	if (fsync(h)) {
+		auto err (errno);
+
+		BOOST_THROW_EXCEPTION(posix_error()
+			<< boost::errinfo_api_function("fsync")
+			<< boost::errinfo_errno(err)
+			<< boost::errinfo_file_name(m_TempFilename));
+	}
+#endif /* _WIN32 */
+
+	close();
+	(void)::close(m_Fd);
+	m_Fd = -1;
+
+	Utility::RenameFile(m_TempFilename, m_Path);
+	m_TempFilename = "";
+}