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#include "lock.hpp"
// io/lock.hpp - Output to files with atomic replacement and backups.
//
// Copyright © 2013 Ben Longbons <b.r.longbons@gmail.com>
//
// This file is part of The Mana World (Athena server)
//
// 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 3 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, see <http://www.gnu.org/licenses/>.
#include <fcntl.h>
#include <unistd.h>
#include <cerrno>
#include <cstdlib>
#include "../strings/zstring.hpp"
#include "cxxstdio.hpp"
#include "fd.hpp"
#include "../poison.hpp"
/// number of backups to keep
static
const int backup_count = 10;
/// Protected file writing
/// (Until the file is closed, it keeps the old file)
namespace io
{
// Start writing a tmpfile
static
FD get_lock_open(ZString filename, int *info)
{
FD fd;
int no = getpid();
// Get a filename that doesn't already exist
AString newfile;
do
{
newfile = STRPRINTF("%s_%d.tmp"_fmt, filename, no++);
fd = FD::open(newfile, O_WRONLY | O_CREAT | O_EXCL, 0666);
}
while (fd == FD() && errno == EEXIST);
if (fd == FD())
abort();
*info = --no;
return fd;
}
WriteLock::WriteLock(RString fn, bool linebuffered)
: WriteFile(get_lock_open(fn, &tmp_suffix), linebuffered), filename(fn)
{}
WriteLock::~WriteLock()
{
if (!WriteFile::close())
{
// leave partial file
FPRINTF(stderr, "Warning: failed to write replacement for %s\n"_fmt, filename);
abort();
}
int n = backup_count;
AString old_filename = STRPRINTF("%s.%d"_fmt, filename, n);
while (--n)
{
AString newer_filename = STRPRINTF("%s.%d"_fmt, filename, n);
rename(newer_filename.c_str(), old_filename.c_str());
old_filename = std::move(newer_filename);
}
rename(filename.c_str(), old_filename.c_str());
AString tmpfile = STRPRINTF("%s_%d.tmp"_fmt, filename, tmp_suffix);
rename(tmpfile.c_str(), filename.c_str());
}
} // namespace io
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