From aed113042d7467f1bf0793443e65a6941975394f Mon Sep 17 00:00:00 2001
From: William Wilgus <wilgus.william@gmail.com>
Date: Sun, 7 Nov 2021 14:25:21 -0500
Subject: [PATCH] RFC settings & nvram.bin save setting to tmp file save old

 save to a .tmp file on save and rename on next load

I think this should pretty minimally invasive as the same file
still gets overwritten in subsequent attempts until it is loaded again

the save path is still static
so it won't cause issues holding up shutdown.

load might be a bit slower with the searching for tmp+current file
and renaming them

Plus there is now a backup of your last settings file

Change-Id: If95618b93a0ba7954d5d8cab1d6ea3f07e658509
---
 apps/settings.c | 34 ++++++++++++++++++++++++++++++++--
 1 file changed, 32 insertions(+), 2 deletions(-)

diff --git a/apps/settings.c b/apps/settings.c
index 3f257e093a..c7dd2cf9ab 100644
--- a/apps/settings.c
+++ b/apps/settings.c
@@ -96,6 +96,29 @@ struct system_status global_status;
 #include "usb-ibasso.h"
 #endif
 
+#ifdef ROCKBOX_NO_TEMP_SETTINGS_FILE /* Overwrites same file each time */
+#define CONFIGFILE_TEMP CONFIGFILE
+#define NVRAM_FILE_TEMP NVRAM_FILE
+#define rename_temp_file(a,b,c)
+#else /* creates temp files on save, renames next load, saves old file if desired */
+#define CONFIGFILE_TEMP CONFIGFILE".new"
+#define NVRAM_FILE_TEMP NVRAM_FILE".new"
+static void rename_temp_file(const char *tempfile,
+                            const char *file,
+                            const char *oldfile)
+{
+    /* if tempfile does not exist -- Return
+     * if oldfile is supplied     -- Rename file to oldfile
+     * if tempfile does exist     -- Rename tempfile to file
+    */
+    if (file_exists(tempfile))
+    {
+        if (oldfile != NULL && file_exists(file))
+            rename(file, oldfile);
+        rename(tempfile, file);
+    }
+}
+#endif
 
 long lasttime = 0;
 
@@ -112,6 +135,7 @@ static char nvram_buffer[NVRAM_BLOCK_SIZE];
 
 static bool read_nvram_data(char* buf, int max_len)
 {
+    rename_temp_file(NVRAM_FILE_TEMP, NVRAM_FILE, NVRAM_FILE".old");
     unsigned crc32 = 0xffffffff;
     int var_count = 0, i = 0, buf_pos = 0;
     int fd = open(NVRAM_FILE, O_RDONLY);
@@ -182,7 +206,7 @@ static bool write_nvram_data(char* buf, int max_len)
     crc32 = crc_32(&buf[NVRAM_DATA_START],
                     max_len-NVRAM_DATA_START-1,0xffffffff);
     memcpy(&buf[4],&crc32,4);
-    fd = open(NVRAM_FILE,O_CREAT|O_TRUNC|O_WRONLY, 0666);
+    fd = open(NVRAM_FILE_TEMP,O_CREAT|O_TRUNC|O_WRONLY, 0666);
     if (fd >= 0)
     {
         int len = write(fd,buf,max_len);
@@ -203,6 +227,7 @@ void settings_load(int which)
         read_nvram_data(nvram_buffer,NVRAM_BLOCK_SIZE);
     if (which&SETTINGS_HD)
     {
+        rename_temp_file(CONFIGFILE_TEMP, CONFIGFILE, CONFIGFILE".old");
         settings_load_config(CONFIGFILE, false);
         settings_load_config(FIXEDSETTINGSFILE, false);
     }
@@ -571,7 +596,7 @@ static void flush_global_status_callback(void)
 static void flush_config_block_callback(void)
 {
     write_nvram_data(nvram_buffer,NVRAM_BLOCK_SIZE);
-    settings_write_config(CONFIGFILE, SETTINGS_SAVE_CHANGED);
+    settings_write_config(CONFIGFILE_TEMP, SETTINGS_SAVE_CHANGED);
 }
 
 void reset_runtime(void) {
@@ -609,6 +634,11 @@ int settings_save(void)
 
 bool settings_save_config(int options)
 {
+    /* if we have outstanding temp files it would be a good idea to flush
+     them before the user starts saving things */
+    rename_temp_file(NVRAM_FILE_TEMP, NVRAM_FILE, NULL); /* dont overwrite .old */
+    rename_temp_file(CONFIGFILE_TEMP, CONFIGFILE, NULL); /* files from last boot */
+
     char filename[MAX_PATH];
     const char *folder, *namebase;
     switch (options)