From: Christian Heller <c.heller@plomlompom.de>
Date: Wed, 9 Jul 2014 21:27:47 +0000 (+0200)
Subject: Server: Atomify the savefile writing.
X-Git-Tag: tce~721
X-Git-Url: https://plomlompom.com/repos/%7B%7B%20web_path%20%7D%7D/decks/%7B%7Bprefix%7D%7D/static/blog?a=commitdiff_plain;h=1bfcaf6f47bb2eb06c071e39b6f93c92a15d4de6;p=plomrogue

Server: Atomify the savefile writing.
---

diff --git a/TODO b/TODO
index 8ba4592..7557ab3 100644
--- a/TODO
+++ b/TODO
@@ -9,6 +9,8 @@ BOTH SERVER/CLIENT:
 - make server and client communicate by specific world state info requests 
   in server/out, replacing server/worldstate
 
+- on start, alarm about _tmp files (savefile/record) to avoid gameplay data loss
+
 SERVER:
 
 - consider
@@ -17,8 +19,6 @@ SERVER:
 - save confserver/world data in record and save file, too; handle them like god
   commands
 
-- ensure atomic re-writing of savefile
-
 CLIENT:
 
 - enable toggling of window borders
diff --git a/src/server/io.c b/src/server/io.c
index c703f0e..c1cbb3e 100644
--- a/src/server/io.c
+++ b/src/server/io.c
@@ -331,8 +331,11 @@ extern char * io_round()
 extern void save_world()
 {
     char * f_name = "save_world()";
-    char * path = s[S_PATH_SAVE];
-    FILE * file = try_fopen(path, "w", f_name);
+    uint16_t size = strlen(s[S_PATH_SAVE]) + strlen(s[S_PATH_SUFFIX_TMP]) + 1;
+    char * path_tmp = try_malloc(size, f_name);
+    int test=sprintf(path_tmp,"%s%s",s[S_PATH_SAVE], s[S_PATH_SUFFIX_TMP]);
+    exit_trouble(test < 0, f_name, s[S_FCN_SPRINTF]);
+    FILE * file = try_fopen(path_tmp, "w", f_name);
     write_key_value(file, s[S_CMD_DO_FOV], 0);
     try_fputc('\n', file, f_name);
     write_key_value(file, s[S_CMD_SEED_MAP], world.seed_map);
@@ -345,5 +348,5 @@ extern void save_world()
         write_thing(file, t);
     }
     write_key_value(file, s[S_CMD_DO_FOV], 1);
-    try_fclose(file, f_name);
+    try_fclose_unlink_rename(file, path_tmp, s[S_PATH_SAVE], f_name);
 }
diff --git a/src/server/io.h b/src/server/io.h
index 0e04d80..8211753 100644
--- a/src/server/io.h
+++ b/src/server/io.h
@@ -26,8 +26,8 @@
  */
 extern char * io_round();
 
-/* Write to savefile god commands (one per line) to rebuild the current world
- * state.
+/* Write to savefile (atomically) god commands (one per line) to rebuild the
+ * current world state.
  */
 extern void save_world();