1 files changed, 87 insertions, 0 deletions
diff --git a/src/io/lock.cpp b/src/io/lock.cpp
new file mode 100644
index 0000000..7ee4fbe
--- /dev/null
+++ b/src/io/lock.cpp
@@ -0,0 +1,87 @@
+#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 "../strings/zstring.hpp"
+
+// TODO remove this violation of include order
+#include "../common/cxxstdio.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)
+
+// Start writing a tmpfile
+static
+int get_lock_open(ZString filename, int *info)
+{
+    int fd;
+    int no = getpid();
+
+    // Get a filename that doesn't already exist
+    FString newfile;
+    do
+    {
+        newfile = STRPRINTF("%s_%d.tmp", filename, no++);
+        fd = open(newfile.c_str(), O_WRONLY | O_CREAT | O_EXCL, 0666);
+    }
+    while (fd == -1 && errno == EEXIST);
+    if (fd == -1)
+        abort();
+    *info = --no;
+    return fd;
+}
+
+namespace io
+{
+    WriteLock::WriteLock(FString 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", filename);
+            abort();
+        }
+
+        int n = backup_count;
+        FString old_filename = STRPRINTF("%s.%d", filename, n);
+        while (--n)
+        {
+            FString newer_filename = STRPRINTF("%s.%d", 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());
+
+        FString tmpfile = STRPRINTF("%s_%d.tmp", filename, tmp_suffix);
+        rename(tmpfile.c_str(), filename.c_str());
+    }
+} // namespace io