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Introduce AtomicFile
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Al2Klimov committed Jul 26, 2022
1 parent 34cb7cd commit ef95a9b
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Showing 5 changed files with 131 additions and 5 deletions.
2 changes: 1 addition & 1 deletion CMakeLists.txt
Original file line number Diff line number Diff line change
Expand Up @@ -163,7 +163,7 @@ else()
set(LOGROTATE_CREATE "\n\tcreate 644 ${ICINGA2_USER} ${ICINGA2_GROUP}")
endif()

find_package(Boost ${BOOST_MIN_VERSION} COMPONENTS coroutine context date_time filesystem thread system program_options regex REQUIRED)
find_package(Boost ${BOOST_MIN_VERSION} COMPONENTS coroutine context date_time filesystem iostreams thread system program_options regex REQUIRED)

# Boost.Coroutine2 (the successor of Boost.Coroutine)
# (1) doesn't even exist in old Boost versions and
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1 change: 1 addition & 0 deletions lib/base/CMakeLists.txt
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Expand Up @@ -17,6 +17,7 @@ set(base_SOURCES
application.cpp application.hpp application-ti.hpp application-version.cpp application-environment.cpp
array.cpp array.hpp array-script.cpp
atomic.hpp
atomic-file.cpp atomic-file.hpp
base64.cpp base64.hpp
boolean.cpp boolean.hpp boolean-script.cpp
bulker.hpp
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92 changes: 92 additions & 0 deletions lib/base/atomic-file.cpp
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@@ -0,0 +1,92 @@
/* 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;

AtomicFile::AtomicFile(String path, int mode) : m_Path(std::move(path))
{
m_TempFilename = m_Path + ".tmp.XXXXXX";
int fd;

#ifdef _WIN32
fd = Utility::MksTemp(&m_TempFilename[0]);
#else /* _WIN32 */
fd = mkstemp(&m_TempFilename[0]);
#endif /* _WIN32 */

if (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));
}

exceptions(failbit | badbit);
open(boost::iostreams::file_descriptor(fd, boost::iostreams::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));
}
}

AtomicFile::~AtomicFile()
{
if (!m_TempFilename.IsEmpty()) {
try {
Utility::Remove(m_TempFilename);
} catch (...) {
// A destructor must not throw
}
}
}

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();

Utility::RenameFile(m_TempFilename, m_Path);
m_TempFilename = "";
}
33 changes: 33 additions & 0 deletions lib/base/atomic-file.hpp
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@@ -0,0 +1,33 @@
/* Icinga 2 | (c) 2022 Icinga GmbH | GPLv2+ */

#ifndef ATOMIC_FILE_H
#define ATOMIC_FILE_H

#include "base/string.hpp"
#include <boost/iostreams/device/file_descriptor.hpp>
#include <boost/iostreams/stream.hpp>

namespace icinga
{

/**
* Atomically replaces a file's content.
*
* @ingroup base
*/
class AtomicFile : public boost::iostreams::stream<boost::iostreams::file_descriptor>
{
public:
AtomicFile(String path, int mode);
~AtomicFile();

void Commit();

private:
String m_Path;
String m_TempFilename;
};

}

#endif /* ATOMIC_FILE_H */
8 changes: 4 additions & 4 deletions lib/base/utility.hpp
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Expand Up @@ -134,6 +134,10 @@ class Utility

static String CreateTempFile(const String& path, int mode, std::fstream& fp);

#ifdef _WIN32
static int MksTemp(char *tmpl);
#endif /* _WIN32 */

#ifdef _WIN32
static String GetIcingaInstallPath();
static String GetIcingaDataPath();
Expand Down Expand Up @@ -185,10 +189,6 @@ class Utility
private:
Utility();

#ifdef _WIN32
static int MksTemp (char *tmpl);
#endif /* _WIN32 */

#ifdef I2_DEBUG
static double m_DebugTime;
#endif /* I2_DEBUG */
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