config rotation + redundancy prototype

src/engine/config.cpp

@@ -27,6 +27,30 @@
 #define CHECK_BUF_SIZE 8192
 
 bool DivConfig::save(const char* path, bool redundancy) {
+  if (redundancy) {
+    char oldPath[4096];
+    char newPath[4096];
+
+    if (fileExists(path)==1) {
+      logD("rotating config files...");
+      for (int i=4; i>=0; i--) {
+        if (i>0) {
+          snprintf(oldPath,4095,"%s.%d",path,i);
+        } else {
+          strncpy(oldPath,path,4095);
+        }
+        snprintf(newPath,4095,"%s.%d",path,i+1);
+
+        if (i>=4) {
+          logV("remove %s",oldPath);
+          deleteFile(oldPath);
+        } else {
+          logV("move %s to %s",oldPath,newPath);
+          moveFiles(oldPath,newPath);
+        }
+      }
+    }
+  }
   logD("opening config for write: %s",path);
   FILE* f=ps_fopen(path,"wb");
   if (f==NULL) {
@@ -39,7 +63,9 @@ bool DivConfig::save(const char* path, bool redundancy) {
     if (fwrite(toWrite.c_str(),1,toWrite.size(),f)!=toWrite.size()) {
       logW("could not write config file! %s",strerror(errno));
       reportError(fmt::sprintf("could not write config file! %s",strerror(errno)));
+      logV("removing config file");
       fclose(f);
+      deleteFile(path);
       return false;
     }
   }

src/fileutils.cpp

@@ -20,6 +20,10 @@
 #include "fileutils.h"
 #ifdef _WIN32
 #include "utfutils.h"
+#include <windows.h>
+#else
+#include <unistd.h>
+#include <errno.h>
 #endif
 
 FILE* ps_fopen(const char* path, const char* mode) {
@@ -29,3 +33,48 @@ FILE* ps_fopen(const char* path, const char* mode) {
   return fopen(path,mode);
 #endif
 }
+
+// TODO: copy in case of failure
+bool moveFiles(const char* src, const char* dest) {
+#ifdef _WIN32
+  return MoveFileW(utf8To16(src).c_str(),utf8To16(dest).c_str());
+#else
+  if (rename(src,dest)==-1) {
+    return false;
+  }
+  return true;
+#endif
+}
+
+bool deleteFile(const char* path) {
+#ifdef _WIN32
+  return DeleteFileW(utf8To16(path).c_str());
+#else
+  return (unlink(path)==0);
+#endif
+}
+
+int fileExists(const char* path) {
+#ifdef _WIN32
+  if (PathFileExistsW(utf8To16(path).c_str()) return 1;
+  // which errors could PathFileExists possibly throw?
+  switch (GetLastError()) {
+    case ERROR_FILE_EXISTS:
+      return 1;
+      break;
+    case ERROR_FILE_NOT_FOUND:
+    case ERROR_PATH_NOT_FOUND:
+    case ERROR_INVALID_DRIVE:
+    case ERROR_DEV_NOT_EXIST:
+    case ERROR_NETNAME_DELETED:
+    case ERROR_BAD_NET_NAME:
+      return 0;
+      break;
+  }
+  return -1;
+#else
+  if (access(path,F_OK)==0) return 1;
+  if (errno==ENOENT) return 0;
+  return -1;
+#endif
+}

src/fileutils.h

@@ -22,5 +22,9 @@
 #include <stdio.h>
 
 FILE* ps_fopen(const char* path, const char* mode);
+bool moveFiles(const char* src, const char* dest);
+bool deleteFile(const char* path);
+// returns 1 if file exists, 0 if it doesn't and -1 on error.
+int fileExists(const char* path);
 
 #endif