1 files changed, 33 insertions, 13 deletions

diff --git a/src/common/lock.cpp b/src/common/lock.cpp
index 2ba9a0a..82856e1 100644
--- a/src/common/lock.cpp
+++ b/src/common/lock.cpp
@@ -1,36 +1,56 @@
-#include <unistd.h>
-#include <stdio.h>
 #include "lock.hpp"
+
+#include <unistd.h>
+
+#include <cstdio>
+
+#include "cxxstdio.hpp"
 #include "socket.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
-FILE *lock_fopen (const char *filename, int *info)
+FILE *lock_fopen(const char *filename, int *info)
 {
-    char newfile[512];
     FILE *fp;
-    int  no = getpid ();
+    int no = getpid();
 
     // Get a filename that doesn't already exist
+    std::string newfile;
     do
     {
-        sprintf (newfile, "%s_%d.tmp", filename, no++);
+        newfile = STRPRINTF("%s_%d.tmp", filename, no++);
+        fp = fopen_(newfile.c_str(), "wx");
     }
-    while ((fp = fopen_ (newfile, "r")) && (fclose_ (fp), 1));
+    while (!fp);
     *info = --no;
-    return fopen_ (newfile, "w");
+    return fp;
 }
 
 // Delete the old file and rename the new file
-void lock_fclose (FILE * fp, const char *filename, int *info)
+void lock_fclose(FILE *fp, const char *filename, int *info)
 {
-    char newfile[512];
     if (fp)
     {
-        fclose_ (fp);
-        sprintf (newfile, "%s_%d.tmp", filename, *info);
-        rename (newfile, filename);
+        fclose_(fp);
+        int n = backup_count;
+        std::string old_filename = STRPRINTF("%s.%d", filename, n);
+        while (--n)
+        {
+            std::string newer_filename = STRPRINTF("%s.%d", filename, n);
+            rename(newer_filename.c_str(), old_filename.c_str());
+            old_filename = std::move(newer_filename);
+        }
+        rename(filename, old_filename.c_str());
+
+        std::string tmpfile = STRPRINTF("%s_%d.tmp", filename, *info);
+        rename(tmpfile.c_str(), filename);
     }
 }