Don't successfully save a savegame if a buffer overrun occurs, and don't

overwrite the existing savegame.

Subversion-branch: /trunk/chocolate-doom
Subversion-revision: 1119

3 files changed, 51 insertions, 10 deletions

diff --git a/src/g_game.c b/src/g_game.c
index c9e3879f..4f7a3d43 100644
--- a/src/g_game.c
+++ b/src/g_game.c
@@ -1485,21 +1485,25 @@ G_SaveGame
  
 void G_DoSaveGame (void) 
 { 
-    char	name[100]; 
-    char*	description; 
-	
-    strcpy(name, P_SaveGameFile(savegameslot));
+    char *savegame_file;
+    char *temp_savegame_file;
 
-    description = savedescription; 
-	 
-    save_stream = fopen(name, "wb");
+    temp_savegame_file = P_TempSaveGameFile();
+    savegame_file = P_SaveGameFile(savegameslot);
+
+    // Open the savegame file for writing.  We write to a temporary file
+    // and then rename it at the end if it was successfully written.
+    // This prevents an existing savegame from being overwritten by 
+    // a corrupted one, or if a savegame buffer overrun occurs.
+
+    save_stream = fopen(temp_savegame_file, "wb");
 
     if (save_stream == NULL)
     {
         return;
     }
 
-    P_WriteSaveGameHeader(description);
+    P_WriteSaveGameHeader(savedescription);
  
     P_ArchivePlayers (); 
     P_ArchiveWorld (); 
@@ -1516,11 +1520,19 @@ void G_DoSaveGame (void)
         I_Error ("Savegame buffer overrun");
     }
     
+    // Finish up, close the savegame file.
+
     fclose(save_stream);
 
+    // Now rename the temporary savegame file to the actual savegame
+    // file, overwriting the old savegame if there was one there.
+
+    remove(savegame_file);
+    rename(temp_savegame_file, savegame_file);
+    
     gameaction = ga_nothing; 
     strcpy(savedescription, "");
-	 
+
     players[consoleplayer].message = DEH_String(GGSAVED);
 
     // draw the pattern into the back screen
diff --git a/src/p_saveg.c b/src/p_saveg.c
index afd3852d..40b5f988 100644
--- a/src/p_saveg.c
+++ b/src/p_saveg.c
@@ -44,11 +44,36 @@
 FILE *save_stream;
 int savegamelength;
 
+// Get the filename of a temporary file to write the savegame to.  After
+// the file has been successfully saved, it will be renamed to the 
+// real file.
+
+char *P_TempSaveGameFile(void)
+{
+    static char *filename = NULL;
+
+    if (filename == NULL)
+    {
+        filename = malloc(strlen(savegamedir) + 32);
+    }
+
+    sprintf(filename, "%stemp.dsg", savegamedir);
+
+    return filename;
+}
+
+// Get the filename of the save game file to use for the specified slot.
+
 char *P_SaveGameFile(int slot)
 {
-    static char filename[256];
+    static char *filename = NULL;
     char basename[32];
 
+    if (filename == NULL)
+    {
+        filename = malloc(strlen(savegamedir) + 32);
+    }
+
     sprintf(basename, DEH_String(SAVEGAMENAME "%d.dsg"), slot);
 
     sprintf(filename, "%s%s", savegamedir, basename);
diff --git a/src/p_saveg.h b/src/p_saveg.h
index 6f95585e..3a96cc3e 100644
--- a/src/p_saveg.h
+++ b/src/p_saveg.h
@@ -34,6 +34,10 @@
 
 #define SAVESTRINGSIZE 24
 
+// temporary filename to use while saving.
+
+char *P_TempSaveGameFile(void);
+
 // filename to use for a savegame slot
 
 char *P_SaveGameFile(int slot);